EPA-600/3-83-088
September 1983
ADSORPTION AND DESORPTION OF HEXACHLOROBIPHENYL
A. Experimental Results and Discussions
B. Analysis of Exchangeable and
Nonexchangeable Components
by
Dominic M. Di Toro
Lewis M. Horzempa
Maureen C. Casey
Environmental Engineering and Science Program
Manhattan College
Bronx, New York 10471
January 1982
-------
r ' TECHNICAL REPORT DATA
| (Root read trutrucnara on tfu rr*ern btfcn compUttntf
[TREPPRTNO. J.
EPA-600/3-83-088
4. TITLE ANOSUBTITLB
Adsorption and Desorptlon of Hexach lorobipheny I
A. Experimental Results and Discussions; B. Analysis
[of Exchangeable and Nonexchangeable Components
IT. AUTHORISI
ID. M. DiToro, L. M. Horzempa, and M. C. Casey
|». PERFORMING ORGANIZATION NAMt AND ADDRESS
I Environmental Engineering and Science Program
I Manhattan College
I Bronx, New York 10471
I 17. SPONSORING AGENCY NAME AND AOORES3
I Environmental Research Laboratory
1 Office of Research and Development
I U.S. Environmental Protection Aqency
1 Duluth, MN 55804
a, REcmeNTTACcessiON NO.
/-H;:''5-v,7^/^:-y
8. REPORT OAT8
September 1983
•.PERFORMING ORGANIZATION COOl
«, PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
H. CONTRACT/GRANT NO
CR 805229 & CR 807853
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY COO6
EPA/600/03
MS. SUPPLEMENTARY NOTES .... . ,
I Final Report, Project 805229, Environmental Engineering and Science Program, Manhattan
I Co liege, Bronx, New York (January 1982)
118. ABSTRACT
The purpose of this report is to present the experimental and theoretical results that .lead to the
development model for the analysis of adsorption and dssorption of hexachlorobiphenyl fron suspended and
sedimented particles.
The reversibility of the adsorption reaction between dissolved organic chemicals and naturally occurring
soils, sediments, and suspended particles is of fundamental importance In th9 understanding of the fata
of these chemicals in tho environment. The Issue of reversibility becomes critical if the
adsorptlon-dosorption behavior of a-chemical is to be expressed quantitatively within the framework of
•nass balance equations. In the formulations used to date, with a notable exception to be discussed
tolow, the formulations used to express the adsorption and desorption reactions assume reversible
behavior, that is, at equl I Ibr lum, the same Isotherm applies for adsorption and desorption.
The difficulty «ith this assumption is that for rnany organic chemicals and many naturally occurring.
adsorbents, laboratory adsoption and subsequent desorption experiments demonstrate only partially
reversible behavior.
In the experiment described In Part A, Section VIII, this nonsingular behavior was confirmed and, using
various experimental procedures, It was found to persist. This suggests that it Is necessary to account
for this behavior in a quantitative and consistent way.
It is the purpose of Part B of this report to present a framework within which this nonsingular behavior
can be analyzed In a manner that can be easily Incorporated Into mass balance calculations.
[17. KIV WORDS AND DOCUMENT ANALYSIS "
[a. DESCRIPTORS
|1>. OIlTMiauTION STATEMENT
[RELEASE TO PUBLIC
b.lDENTIPIERS/OPEN ENDED TERMS
It. SECURITY CLASS (JTUl K.fwt)
UNCLASSIFIED
70. SECURITY CLASS IT»lt ptft)
UNCLASSIFIED
c. COSATI FieUVGroup
21. NO. OF PAQES
322
aa. rmct
tf A
J239-1 ("•»• <-T7) •••vtovii COITION n O»»OL«T«
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
11
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ACKNOWLEDGEMENT
The authors are pleased to acknowledge the assistance and cooperation
of our colleagues in this effort. The members of the EPA Large Lakes Re-
search Station, Grosse lie, Michigan: Nelson Thomas, William Richardson,
Michael Mullin; and our group at Manhattan College: John Jeris, Robert
Thomann, Donald O'Connor, John Mancini, Joanne Guerriero, Michael Labiak
and Danny Ciarcia.
The research described in this report was conducted under two research
grants:
Analysis of Nutrient and Toxic Chemical Fluxes to the Great Lakes
(CR 805229)
Mathematical Models of the Fate of Toxic Chemicals in the Great Lakes
(CR 807853)
Part A and Part B of the report correspond, approximately, to that portion
of the research conducted under each grant.
Our special thanks to Katherine King, Eileen Lutomski and Margaret
Cafarella for assistance in the report preparation and typing.
iii
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TABLE OF CONTENTS
Part A
Section Title Page
I Summary and Recommendations 1
II Introduction and Previous Work 13
III Experimental Methodology and Initial Experimental
Results 16
IV Kinetics , 34
V Effect of Solution Composition 51
VI Sediment Composition Effects . 66
VII Sediment Concentration Effects 86
VIII Reversibility of Adsorption and Desorption 107
Part B
I Exchangeable and Nonexchangeahle Components Model of
Adsorption and Desorption 139
II Effect of Sediment Concentration and Composition 169
III Resuspension and Dilution: Implications for Fate
of PCB 193
IV
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FIGURES - Part A
Fig.
1-1. Exchangeable-Nonexchangeable Component Model
of Desorption 4
1-2. HCB Isotherm Analysis. Saginaw Bay Station #50 . . . . 6
1-3. Partition Coefficient vs. Adsorbent Concentration 7
1-4. HCB Partition Coefficient versus Adsorbent Concen-
tration. Saginaw Bay Station #50, Distilled Water 8
1-5. Particulate fraction versus adsorbent mass for
reversible desorption, eq. (15); and exchangeable-
4
nonexchangeable desorption, eq. (17). IT =10 £/kg,
v =0.5 11
x
III-l. Flow Chart of Experimental Procedure 17
III-2. Adsorption-Desorption Experimental Procedure . . 19
III-3. Histogram of Mass Balance Error, e (%) 23
III-4. Adsorption of HCB to Vessel Walls 24
III-5. Adsorption of HCB to Metal Coated Vessels 25
III-6. Glass Adsorption Isotherm: Volumetric Concentration of HCB
Adsorbed to the Wall versus Aqueous Concentration. Dis-
tilled Water 27
III-7. Adsorbed HCB Concentration at Adsorption Equilibrium, mr ,
21
versus Total HCB Concentration at Desorption Equilibrium,
-------
c , for Type 3 Experiments. Histograms of % Error = 100%
(mra ~ CTd)/CT
-------
Supernatant, t =2 hr 44
3
IV-8. Long Term Desorption. Sediment Bound HCB, r. and desorption
partition coefficient, IT ,(H/g) (x 10 for convenience in
plotting) versus desorption time 45
IV-9. Adsorption (r vs. c ) and Desorption (r, vs. c.)
a a d d
Isotherms: t = 3 hr., t, = 3 hr. m = 1100 mg/£.
ad
Saginaw Bay //50. Distilled Water 48
IV-10. Adsorption (r vs. c ) and Desorption (r. vs. c,). Isotherms
a a d d
for increasing desorption times: t = 72 and 144 hr. m =
1100 mg/£ Saginaw Bay #50, Distilled Water 49
IV-11. Effect of Increasing Desorption Time. Saginaw Bay #50 50
V-l. Effect of Temperature on HCB Adsorption, t = 3 hr.,
&
m = 1100 mg/Jl Saginaw Bay #50 52
V-2. Effect of pH on HCB Partitioning to Montmorillonite 56
V-3. Effect of Increasing Ionic Strength using NaCl and Cad-
on HCB Adsorption Partition Coefficient for Montmorill-
onite. m = 200 mg/«,. t = 4 hr 57
Q.
V-4. Adsorption Isotherm for Distilled Water and 0.01M CaCK
ra = 220 mg/£ Montmorillonite 60
V-5. Adsorption Isotherm for Distilled Water and 0.01M CaCl_.
m = 220 mg/S, Saginaw Bay #50 61
V-6. Effect of pH on Vessel Adsorption of HCB 62
V-7. Effect of Solution Composition on Vessel (Glass) Adsorption
of HCB 64
vii
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VI —1. Location Map Lor Sediment Samples O/
VI-2. HCB Adsorption and Desorption Isotherms for Saginaw Bay
sediment samples, m = 1100 mg/£ 74
VI-3. HCB Adsorption and Desorption Isotherms for Station #69 75
VI-4. HCB Adsorption & Desorption Isotherms for Station //31
on Total and Suspended Solids Samples 77
VI-5. Adsorption and Desorption Partition Coefficients versus
Specific Surface area and % Volatile Solids 82
VI-6. Comparison of Estimated Partition Coefficient using
Regression Equation to Observed Values 83
VII-1. Adsorption Partition Coefficient vs. Adsorbent Concentration. . . 88
VII-2. Adsorption Isotherms for m = 55, 220, and 1100 mg/£
Saginaw Bay #50 .89
VII-3. Adsorption Isotherms for m = 50, 200, 1000 mg/X,
Montmorillonite 91
VII-4. Adsorption Isotherms for m = 55 and 1100 mg/Jl Montmorillonite
Aqueous phase = 2 mM NaHC03 92
VII-5. Variation in Adsorption partition coefficient, TT , and
Si
Sediment Bound HCB, r , versus adsorbent concentration,
a
m, at constant equilibrium aqueous concentration, c 94
VII-6. Variation in Adsorption partition coefficient, ir , and
a
Sediment Bound HCB, r , versus adsorbent concentration,
a
m, at constant equilibrium aqueous concentration, c 95
a
VII-7. Variation in Adsorption partition coefficient, ir , and
viii
-------
Sediment Bound HCB, r versus adsorbent concentration, m,
a.
at constant equilibrium aqueous concentration, c 96
3
VII-8. Variation in Adsorption partition coefficient, IT , and
a.
Sediment Bound HCB, r versus adsorbent concentration, m,
a
at constant equilibrium aqueous concentration, c 98
a
VII-9. Variation in Adsorption partition coefficient, ir , and
3
sediment bound HCB, r , versus adsorbent concentration,
a
m, at constant equilibrium aqueous concentration, c .
a
Effect of increased adsorption time, t = 24 hr. versus
3.
t = 3 hr. (dashed line from fig. VII-6) 99
3.
VII-10. Log-log analysis of ir versus m. Straight line slopes &
3
intercepts are given in Table VII-1 101
VII-11. Comparison of particulate fraction computed using constant
IT to observed data 105
a
VIII-1. Adsorption and Desorption Isotherms - Montmorillonite
Distilled Water. Lines have, unity slope 110
VIII-2. Adsorption and Desorption Isotherms - Montmorillonite,
Aqueous phase = 2mM NaHCO. and Kaolinite, Distilled
Water. Lines have unity slope Ill
VIII-3. Adsorption and Desorption Isotherms - Saginaw Bay #50
Distilled Water. Lines have unity slope .... 112
VIII-4. Effect of Adsorbent Concentration on Degree of Reversibility
Adsorption, ir , and Desorption, IT,, Partition Coefficients
a d
and their ratio 115
VIII-5. Effect of Adsorbent Concentration on Degree of Reversibility
Adsorption, IT , and Desorption, IT , Partition Coefficients
3 . Q
and their ratio ..... 116
ix
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Vlll-6. Effect of Dilution on 1KH1 Dusorpticm 118
VIII-7. Effect of Adsorption Time on Reversibility m = 55 mg/fc
Saginaw Bay #50 121
VIII-8. Effect of Adsorption on Reversibility Adsorption tr , and
a
Desorption, ir, Partition Coefficients versus Adsorbent
mass, t = 24 hr. Montmorillonite. Supernatant 122
3.
VIII-9. Consecutive Desorption Isotherms - Saginaw Bay and
Montmorillonite 124
VIII-10. Consecutive Desorption Isotherms - Saginaw Bay and
Montmorillonite 125
VIII-11. Consecutive Desorption. Saginaw Bay #50. m = 1100 mg/&,
Distilled Water (a) Sediment Bound HCB, r, and (b) aqueous
concentration, c versus desorption cycle, (c) Isotherm 127
VIII-12. Consecutive Desorption. Saginaw Bay #50 and Montmorillonite.
m = 200 mg/£. Distilled Water (a) Sediment Bound HCB, r,
and (b) aqueous concentration, c, versus desorption cycle.
(c) Isotherm 131
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TABLES - Part A
Table
III-l.
Ill-2.
III-3.
111-4.
IV-1.
IV-2.
V-l.
V-2.
VI-1.
VI-2.
VI-3.
VI-4.
VI-5.
VI-6.
VI-7.
VI-8.
VII-1.
VIII-1.
VIII-2.
VIII-3.
VIII-4.
VIII-5.
VIII-6.
Page
Nomenclature and Computational Equations 20-21
Glass Desorption Data 26
Speciation Experiment - Montmorillonite , . 32
Speciation Experiment - Saginaw Bay #50 33
Saginaw Bay Adsorption Isotherms . 39
Long Term Desorption Study . . . , 47
Effects of Temperature on Adsorption 53
Adsorption vs. Chemical Composition ... 59
Sampling Locations for Saginaw Bay 68
Sediment Size Distribution for Saginaw Bay 69
Chemical Characteristics of Saginaw Bay Sediments .... 71
Chemical Characteristics of Saginaw Bay Sediments
Seived Subsamples 72
Sediment Partition Coefficients and Freundlich
Isotherm Parameters 73
HCB Partitioning to Saginaw Bay Suspended Matter 78
Representative PCB Concentrations for Saginaw Bay
Suspended Solids* 80
Multiple Linear Regression Results , 84
Partitioning Coefficient - Adsorbent Mass Regression . . . 102
Isotherm Parameters - Saginaw Bay Sediments 109
Isotherm Parameters - Effect of Sediment Concentration . . 113
Isotherm Parameters - Effect of Adsorption Time 120
Consecutive Desorption Data 126
Consecutive Desorption , , , . 128
Consecutive Desorption ..,,.,,.,. 133
xi
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Adsorption and Desorption of
Hexachlorobiphenyl
Part A
Experimental Results and Discussions
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SECTION I
SUMMARY AND RECOMMENDATIONS
A. Introduction
The purpose of this report is to present the experimental and theoretical
results that lead to the development model for the analysis of adsorption and
desorption of hexachlorobiphenyl from suspended and sedimented particles. In
contrast to the desorption reaction, a large body of information already exists
for the adsorption reaction. Relationships have been developed that relate the
extent of adsorption of organic chemicals to their characteristics such as
aqueous solubility (Chiou et al., 1979) and adsorbent properties such as spe-
cific surface area (Hiraizumi et al., 1979) and organic carbon content
(Karickhoff et al., 1979).
This is not the case, however, for the desorption reaction. The available
information, to be discussed in more detail subsequently, indicates that for a
great many organic adsorbent systems the desorption reaction is not completely
or even moderately reversible. As a consequence the assumption of reversible
behavior is neither justified nor realistic, and it is not possible to directly
apply the large body of adsorption theory and data to describe desorption
since, for nonreversible systems, it is not the same reaction.
This is unfortunate since it is not clear how to incorporate nonreversible
behavior into modeling frameworks that have been, and are being, developed by
EPA and other groups for the computation of the fate of toxic chemicals in
natural waters (Baughman and Lassiter, 1978; Thomann and Di Toro, 1979, O'Connor
and Schnoor, 1979). If the adsorption were either completely reversible, or
completely irreversible so that no desorption occurred, then it would be
straightforward to include such behavior in a fate model. What has been found
experimentally, however, is that some desorption takes place. The amount is
variable and depends on the details of the situation such as the mass of ad-
sorbent and the adsorbate-adsorbent pair involved.
The use of a desorption "partition coefficient" in a way that is analogous
to the use of the adsorption partition coefficient in fate computations, is
not a solution to the problem since the actual quantity of chemical desorbed
when exposed to lower aqueous concentration is not directly related to only the
desorption partition coefficient but also to the quantity of chemical previously
adsorbed. As it happens, for the desorption model described below, the desorp-
tion partition coefficient does have a specific meaning, which the model
-------
clarifies, but it cannot be used directly in fate computations. Without a
specific model for nonreversible desorption, it is not surprising that this
mechanism has not heen explicitly included in fate computations.
The nonreversible behavior of adsorption and desorption can have important
consequences for the fate of chemicals in natural waters. As inputs of toxic
chemicals are reduced, the desorption of already existing toxic chemical from
suspended solids and sediments will constitute the major inputs of dissolved
toxicants into the water column. The magnitude and extent of this reaction
can control the environmental distribution and the exposure level for the biota.
If the quantity of chemical desorbed is much less than the quantity initially
adsorbed then assuming completely reversible behavior can significantly over-
estimate the dissolved chemical in the water column. This overestimate may
translate into an underestimation of the impact of remedial measures such as
discharge reductions via treatment of effluents. Hence, a quantitative under-
standing of the factors that influence the behavior of the desorption reaction
is an essential component for understanding the fate of toxic chemicals in
natural waters and the consequences of remedial actions.
Summary
As part of the effort at Manhattan College to formulate and test mathe-
matical models of the fate of PCB's in the Great Lakes (Thomann, 1977) a series
of experiments have been conducted using tritiated hexachlorobiphenyl (abbreviated
as HCB) as the adsorbate and natural sediments and inorganic clays as the adsor-
bents. The experiments concentrated on the desorption behavior as well as con-
ventional adsorption tests. Nonreversible desorption occurred and an effort was
made to formulate a model which explained the data.
It was assumed that the adsorbed HCB was made up of two components: an
exchangeable component which readily and reversibly desorbes and readsorbes
depending upon aqueous phase concentration, and a second component, which
was termed nonexchangeable, which resisted desorption until very low (or
possibly zero) aqueous concentrations. This idea is often used to explain
nonreversible behavior in qualitative terms, e.g. physical versus chemical
adsorption. Methods were developed for calculating the quantity of the
exchangeable and nonexchangeable components from the experimental adsorption
and desorption data. This is the unique feature of the model since it gives
quantitative estimates of the magnitudes of these components. An analysis of
the individual behavior suggested that each was describable in terms of (dis-
tinct) linear isotherms. This regular behavior, for both natural sediments
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and inorganic clays, represents a significant simplification and codification
of a large quantity of adsorption and desorption data in terms of distinct
partition coefficients for the exchangeable and nonexchangeable components.
Subsequent consecutive adsorption experiments confirmed the distinct behavior
of the two components and supported the validity of the model.
-The basic idea is illustrated in fig. 1. A conventional adsorption-desorption
~tfa't'a s'et (assuming three adsorption points and three desorption points for clarity)
is shown in fig. la. The fact that two distinct isotherms are found for the
adsorption and desorption data indicates that the desorption is not completely
reversible. Consider a single pair of points corresponding to a single adsorp-
tion-desorption experiment, fig. Ib. If it is assumed that continued desorption
cycles follow a straight line, then the intersection of this line and the ordin-
ate defines the particulate concentration which is nonexchangeable (since it
remains on the particles even at zero aqueous concentration). This concentration,
r , is illustrated in fig. Ib. Once the nonexchangeable component concentra-
tion, r , has been found, the differences between this concentration and that
o
found at adsorption and desorption equilibria must be the exchangeable component
since two components are assumed to be present. The fact that it responded to
the decrease in aqueous concentration that occurred from adsorption to desorp-
tion equilibrium supports its exchangeability. Note that two exchangeable
component data points result: at adsorption equilibrium, r , and at desorption
X
-------
(a)
Single Description
"Isotherm1!/
-K
Adsorption
Isotherm
(b)
60
60
C
a
o
cd
l-l
Nonexchangeable Component
(O)
g (c)
O
§
I'x
H
cd
PL4
Exchangeable Component
Isotherm
Exchangeable Components
(d)
Nonexchangeable ComponenJ
Isotherm
Aqueous Concentration (ng/£)
Fig. 1-1. Exchangeable-Nonexchangeable Component Model of Desorption
4
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The actual data set for an HCB adsorption-desorption isotherm experiment,
corresponding to the illustrations in lig. 1. are shown in fig. 2. 1'uri b ol
this report contains additional results of the isotherm analysis for HCB and
a full discussion of the development of the proposed adsorption-desorption
model. Part A of this report presents further data and the results of ex-
perimental modifications designed to eliminate experimental artifacts as the
cause of the nonreversible behavior.
A second focus of the experiments conducted with HCB was the effect of
the mass of adsorbent on the partition coefficients. It had been observed
from an analysis of published data (O'Connor and Connolly, 1980) that adsorp-
tion partition coefficients decrease as adsorbent mass increases. -Ftgr—3",
reproduced from O'Connor and Connolly, 1980, illustrates the effect. This
phenomena was investigated for HCB adsorption and also for desorption. It
was found to occur for both reactions. If the data is interpreted in terms
of exchangeable and nonexchangeable components, it was found that the nonex-
changeable partition coefficient is essentially independent of adsorbent mass
whereas the exchangeable partition coefficient is inversely proportional to
adsorbent mass. An- example is presented in fig. 4. The adsorption and desorp-
tion partition coefficients are seen to decrease as adsorbent mass, m, increases
(fig. 4a). Note that the extent of irreversibility increases as mass increases. .
That is, the desorption partition coefficient becomes Increasingly larger than
the adsorption partition coefficient as adsorbent mass increases. The exchange-
able partition coefficient is seen to be inversely proportional to mass (fig. 4b)
whereas the nonexchangeable partition coefficient is independent of mass (fig. 4c).
This suggests a definition of an exchangeable distribution coefficient: v = TT m
X X
which is also mass independent. The solid lines in fig. 4a are the variations
of adsorption and desorption partition coefficients predicted by the exchange-
able-nonexchangeable desorption model (See Part B for details).
The variation of these mass-independent parameters as functions of sediment
properties has been examined. The details, together with additional data and a
more complete description of the adsorbent mass effects are given subsequently
in Parts A and B.
The result of this combined experimental and modeling program is a quanti-
tative framework within which it is possible to predict the adsorption, and more
significantly, the desorption behavior of hexachlorobiphenyl as a function of
adsorbent mass and its characteristics.
-------
Di-sorpt Ion
a
o
•H
4-1
C
-------
I02
• -DDT
•-HEPTACHLOR
»-LINDANE
• -KEPONE
B - MANGANESE
*- CADMIUM
A-COBALT
k-CALCIUM
I - STRONTIUM
SEDIMENT CONCENTRATION, mg/i
Fig. 1-3. Partition Coefficient vs. Adsorbent Concentration
(O'Connor & Connolly, 1980)
-------
(a)
10
n 10
UAg)
10
3.5-
Dcsorption
i-
io
°'5
10
10-
g
VM " It
a>
o
u
c
o
10
10
(I/kg) 10
p
0)
(V,
10
Exchangeable
io°-5 'lo1
10
10-
io
10-
10
Nonexchangeable
2L_OL
°-5
10
Adsorbent Mass (ng/O
10"
Fig. 1-4". HCB Partition Coefficient versus Adsorbent Concentration.
Saginaw Bay Station 050, Distilled Water.
-------
The importance of the interaction between modeling analysis and experimental
design in such an investigation cannot be overemphasized. The exchangeable-non-
exchangeable model was formulated as a consequence of the need to organize, syn-
thesize, and understand the experimental data. Once the hypothesis was. .formu-
lated in quantitative terms, it was possible to design experiments to test the
model predictions and illucidate the relevant features. The dual capability ;
to do the experiments and formulate the models within a cooperating group is .
essential if progress is to be made in formulating and testing rational, quan-
titative descriptions of complex phenomena such as the desorption reaction.
C. Implications for Receiving Water Fate Models
The use of models for the computation of toxic chemicals exposure levels in
natural waters is currently an important component of rational toxic chemical
regulation and control. The development of EXAMS by EPA (Baughman and Lassiter,
1978), models for PCB, radionuclides and toxic heavy metals in the Great Lakes
by our group at Manhattan College, and other investigations, are currently in
progress. These models have a common approach in dealing with the adsorption-
desorption reaction.
The mass balance equations are written in terms of total chemical, c , with
the transport and kinetic terms suitably modified with the fraction of chemical
in the dissolved, f., or particulate, f , form depending on whether the terms in
the equation apply to particulate or dissolved phases. As an example, consider
a two layer segmentation representing the water column of depth H , and an active
sediment layer of depth H_. These interact via vertical mixing of the aqueous
phases, with mass transfer coefficient 1C ; and settling and resuspension of the
particulate phases, wi
balance equations, are:
particulate phases, with velocities w and w respectively. The governing mass
3 ITS
Hl "dT = KL(fd2CT2 - ^Tl' - WafplCTl + Wrsfp2CT2 + W
H2 -3T = VfdlCTl - fd2cT2) + WafplCTl ~ Wrsfp2CT2
where c and c „ are the total chemical concentrations in the water column and
i JL J, ^ n
sediment layers respectively, and W is the input mass loading rate (M/L /T).
-------
Note the central role of the dissolved (f... and f,0) and particulate (f , and f „)
al o.i pi p2
fractions, in the water column and sediment segments respectively. They directly
affect the magnitudes of the mass transfer coefficients and therefore the fate of
the chemical. A more complex fate computation would include terms for outflow,
the various appropriate decay mechanisms, and sedimentation losses. However, the
principle is still the same. Once the total concentration is computed, the dis-
solved water column concentration is given by: c,1 = f, c , with analagous ex-
pressions for the particulate concentration. Again the particulate and dissolved
fractions play a central role, and these fractions are a direct result of the
adsorption-desorption model employed.
For completely reversible adsorption-desorption and a linear isotherm,
the dissolved and particulate fractions are given by:
(4)
where IT is the reversible partition coefficient and m is the adsorbent concen-
trations. The subscripts 1 and 2 in equations (1) and (2) refer to evaluating
these fractions using the appropriate adsorbent concentration in segments 1
and 2.
Fo.r the HCB exchangeable-nonexchangeable component model of adsorption-
desorption, these fractions depend upon the model parameters: rr , the partition
coefficient for the nonexchangeable component; and v , the distribution coeffi-
f^
cient for the exchangeable component; and the maximum dissolved aqueous concen-
tration to which the particle has been exposed: c ,. This latter concentration
sets the magnitude of the nonexchangeable component. It can be shown (Part B)
that the dissolved and particulate fractions are given by the expressions:
fd = 1 + v + IBIT (c ,/c.) (5)
x o md d
\ ' + "mo(cmd/Cd)
where crf is the current dissolved aqueous phase concentration. The particu-1-ate
. fraction as a function of adsorbent solids concentration, m, is shown in fig-.— 5-;
10
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The Effect of Nonreversible Desorption
1.0
0.3
fp 0.6
0.4
0.2
Cmd/c
100
X
Exchangeable-Nonexchangeable
Desorption Model
Reversible Desorption - - - -
0 .— I""* Itttllll iltlllill I I » I I t I 1 I I illltll|
10 100
Adsorbent Mass.m, (mg/Ji)
1000
10,000
Fig. 1-5. Particulate fraction versus adsorbent mass for reversible
desorption, eq. (15); and exchangeable-nonexchangeable
desorption, eq. (.17). =
11
-------
The conventional, expression, assuming rrver.qIMo behnvlor Is ,-ilso r.hown. Tlirrr
is a significant difference between the conventional reversible formulation
and the exchangeable-nonexchangeable model. The particulate fraction is always
a substantial portion of the total chemical concentration, even at low sus-
pended solids concentrations that are characteristic of most receiving waters
(10-100 mg/£). This suggests that fate computations using the exchangeable-
nonexchangeable model will give quite different results which emphasize the
importance of particle transport.
12
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SECTION II
INTRODUCTION AND PREVIOUS WORK
A. Introduction
The construction of accurate computer models designed to predict the
behavior of polychlorinated biphenyl compounds (PCB's) in natural waters such
as the Great Lakes requires a quantitative knowledge of PCB sediment-water
interactions. Current knowledge of PCB behavior in natural waters is based
in part on studies pertaining to the general behavior of organics in natural
waters (Lambert, 1967; Briggs, 1973; Chiou, 1977; Karickhoff et al., 1979, etc.)
There exists a wide body of information on pesticides including reviews by
Bailey and White (1970), and Dinauer (1974).
Studies specifically addressing PCB behavior have included many field
observations of PCB levels in natural waters such as the Great Lakes (Gloo-
shenko et al., 1976; Haile, 1977; Veith et al., 1977, etc.). Fewer studies
have been devoted to analysis of the mechanisms of PCB sediment-water inter-
actions. Studies on sediment-water Interactions have included soil (Haque
et al., 1974, 1976) fresh water (Steen et al., 1978) and marine (Hiraizumi,
1979) systems. While factors of importance to PCB partitioning to solid
phases have been characterized, the available literature includes wide
variations in reported equilibrium constant values for PCB adsorption to
sediments. These variations suggest that current knowledge of PCB behavior
is insufficient to permit direct quantitative prediction of PCB partitioning
in specific systems such as the Saginaw Bay region of Lake Huron.
The apparent variability of partitioning data may reflect diversity in
the physiochemical properties of the sediments under investigation. Alter-
nately, it is quite possible that results reflect variations in experimental
techniques and reaction conditions. There currently exist several factors of
particular concern in terms of the potential applicability of experimental data
to computer models. The first concerns the need for experimental partitioning
data run under conditions reflecting observed natural water PCB concentrations
particularly in the Great Lakes. The extrapolation of isotherm data run at
high aqueous PCB concentrations to more realistic natural water levels suffers
from a number of objections including solubility constraints. The more highly
chlorinated PCB Isomers (Cl ^ 6) exhibit extremely low water solubility (< 10
13
-------
(Dexter and Pavlov, 1978). Data obtained at aqueous concentrations
in excess of solubility levels may not represent true partitioning between
adsorbed and dissolved phases. Recent decreases in PCB pollution Inputs
should result in reductions in the current part per trillion natural water
levels. Also of critical importance from the modeling standpoint is the
need for quantitative data on PCB desorption from sediments. With reduc-.
tions in PCB inputs, future aqueous phase concentrations may well be con-
trolled by the extent of PCB movement into the water column from underlying
sediments.
The purpose of this study has been to evaluate the problem of PCB
sediment-water interactions both in general terms and more specifically
in terms of determining the magnitude of such interactions in the Saginaw
Bay region of Lake Huron. Studies have been designed to specifically ad-
dress the need for obtaining data at low aqueous concentrations as well as
that of obtaining information on the magnitude of the desorption process.
In addition, experiments have been conducted to assess the potential impor-
tance of possible physiochemical variations in natural waters to the PCB
partitioning process.
B . Theory
Sediment-water HCB partitioning has been evaluated by determining HCB
concentrations in both aqueous, c (ng HCB/2,), and solid phases, r (ng HCB/kg
3. .a
adsorbent). The mass balance equation relating these quantities is:
CTa = Ca + mra (II-1}
where c_ is the initial total HCB concentration, and m is the adsorbent con-
Ta
centration (kg/£) . The partition coefficient TT may be defined as:
3.
_ ^a_ (ng/kg)
The subscript "a" is used to denote the quantities that apply to adsorption.
In the present study, experimental data has been evaluated both in
terms of partition coefficient TT and in terms of the parameters of the
a
Freundlich expression:
-------
where K and 1/n represent constants. This empirical expression lias proviul
useful in describing the behavior of a variety of trace organics and pesti-
cides on soil and sediment systems. Converted to logarithmic form, the
Freundlich expression yields:
log x/m = log K + - log c (II-4)
n 3
The intercept, log K, of a Freundlich plot of the log of the solid phase
HCB concentration vs. the log of the equilibrium concentration is an in-
direct measure of relative free energy changes. As such, it provides some
measure of the relative strength of attachment of the HCB molecule to the
solid phase.
In a review of a large body of adsorption data Hamaker and Thompson (1972)
concluded that the routine approximation of 1/n ^ 1 was probably not justified
and could lead to large errors in attempting to extrapolate adsorption data.
For this reason it is important that HCB laboratory experiments represent as
closely as possible actual aqueous PCB concentrations found in the field.
For this reason radiochemical techniques were employed so the reliable
measurements at low aqueous (1-100 ng/£) and sediment (10-1000 ng/g) concen-
trations could be made, even at low suspended solids levels (10-1000 mg/£).
The methodology is discussed in the next section.
1.5
-------
SECTION III
EXPERIMENTAL METHODOLOGY AND INITIAL EXPERIMENTAL RESULTS
A. Experimental Methodology
PCB partitioning studies have been conducted using tritiated 2,4,5,2',A1,
5' hexachlorobiphenyl (HCB). A single isomer was chosen so that experimental
results are more directly interpretable. Radiochemical studies were found to
combine the advantages of low level HCB detection with ease of sample handling.
Tritiated HCB (38.2 Ci/mmole) was obtained from New England Nuclear Corp. Aqueous
HCB stock solutions were prepared by addition of hexane-tritiated HCB solutions to
a volumetric flask, followed by hexane evaporation. The HCB was subsequently
washed in 2 ml of acetone (Burdick & Jackson, non-spectro grade) and the solution
re-evaporated. The HCB was then taken up in distilled water. Solutions were re-
frigerated to minimize HCB evaporation losses. Aqueous HCB concentrations were
confirmed by capillary column gas chromatographic analysis (EPA, Grosse lie,
Michigan).
A flowchart of the experimental procedure for adsorption is indicated
in Fig. III-l. Partitioning experiments were conducted in 25 ml (Corex-Corning)
centrifuge tubes. (These tubes were selected on the basis of extensive experi-
mentation, discussed subsequently.) Samples were equilibrated for specified
time periods using a Burell Wrist Action Shaker. With the exception of kinetic
studies, adsorption experiments were usually equilibrated for 3 hours and de-
sorption experiments for 2 hours, preceded by an initial adsorption step. Fol-
lowing equilibration, both total HCB (sediment + water) and aqueous HCB samples
were taken. Solid and liquid phases were separated by centrifugation (7000 RPM
for 15 minutes). Both total and aqueous HCB samples were analyzed for tritium
using a Beckman LS-150 liquid scintillation counter. Experimentatio indicated
that HCB was efficiently extracted from the sediment particles directly into
the scintillation fluid (Aquasol-2, New England Nuclear).
Sorption studies were conducted by equilibrating aqueous HCB stock solutions
with a series of natural lake sediment (Saginaw Bay, Lake Huron, Michigan) and
montmorillonite (Wards Natural Science Co.). Montmorillonite samples were
used as received without cation saturation treatment. Sediment suspensions
(<200 mesh solids) were equilibrated at 24 ± 2°C in the 25 ml Corex brand
(Corning Glass Co.) centrifuge tubes.
16
-------
ADD TRITIATED HCB TO
SEDIMENT SUSPENSION
IN COREX TUBE
EQUILIBRATE
AQUEOUS SAMPLE:
SAMPLE FOR
TOTAL COUNT
MIX SAMPLE WITH
AQUASOL II IN
LSC VIAL
EQUILIBRATE
-1 HR
CENTRIFUGE
VIALS
CENTRIFUGE FOR 15
WIN AT 7000 RPM
MIX SAMPLE WITH
AQUASOL II IN
LSC VIAL
COREX TUBE WALLS:
COUNT RADIOACTIVITY WITH
BECKMAN LS-150
DISCARD TUBE CONTENTS.
EXTRACT WALLS WITH
AQUASOL II FOR 1 HR
MIX SAMPLE WITH
AQUASOL II IN
LSC VIAL
Fig. III-l. Flow Chart of Experimental Procedure
-------
The experimental and measurement procedures for the basic adsorption-desorption
measurements are illustrated in fig. (III-2). The aqueous phase, sediment, and HCB
stock solutions are combined to achieve the desired concentrations in 15 mi of
solution in the centrifuge tube. The tube is caped and agitated until adsorption
equilibria is achieved. A sample of the sediment-aqueous phase mixture is removed
and analyzed for HCB concentration, c . After centrifuging, a sample of aqueous
1.3.
phase is removed and analyzed yielding the dissolved concentration at adsorption
equilibrium, c . The particulate concentration at adsorption equilibrium is cal-
3.
culated by difference: r = (c -c )/m, where m is the adsorbent concentration.
3. J.3 3.
This completes the adsorption step.
For the desorption step, the contaminated aqueous phase is carefully removed
leaving the sedimented solids in the tube, and uncontaminated aqueous phase is
added (to achieve a total volume that produces the same adsorbent concentration as
initially present at adsorption). The caped tube is agitated until desorption
equilibrium is achieved. A sample of sediment-aqueous phase mixture is removed and
analyzed yielding c ,. After centrifuging an aqueous phase sample is removed and
analyzed for c,. The particulate concentration is obtained by difference, r, =
(c_,-c,)/m. The remaining sediment and aqueous phase is either discarded or saved
Td d
for further analysis. The centrifuge tube is extracted, and the HCB adsorbed to
the tube is analyzed. A mass balance calculation is made to insure the integrity
of the experiment.
Multiple adsorption and desorption experiments are modifications of these pro-
cedures. The data analysis equations for the calculation of the adsorption and
desorption concentrations are given in Table III-l. Each experimental point is
triplicated in order to reduce the magnitude of the experimental variability.
For the most part three types of experiments were performed:
Type 1: an 'adsorption cycle only
Type 2: an adsorption followed by a desorption with no c_,, measurement
Type 3: an adsorption followed by a desorption with c measured.
The only difference between the Type 2 and 3 results is the presence of a c
measurement. As pointed out subsequently the Type 3 experimental data indicate
that no significant glass desorption occurs so that c can be calculated from
mass balance: c™. = m,r .
Id da
18
-------
ADSORPTION
Sediment (Adsorbent)
Aqueous
Phase
15m2
Adsorbate
Shake
ads
Centrifuge
Remove aqueous
phase
DESORPTION
Add uncontarainated
Aqueous phase
Shake
des
Centrifug
c
i
k
I
k
)
Remove Aqueous
& Sediment
Ext
ract glass
> ,
Mass balance
check
Fig. III-2. Adsorption-Desorption Experimental Procedure
19
-------
Table III-l
Nomenclature and Computational Equations
Initial Conditions
Total Volume (rafc) V
Stock Volume Added (m£) V
SK.
Stock Count (1 m£ sample) (cpm) N
SK
Sediment Concentration (mg/£) m
3.
Adsorption
Total Sample Volume Removed (mJl) V,
»Ta
Ta
Total Count (cpm) N
Aqueous Sample Volume Removed (m£) V
clcl
Aqueous Count (cpm) N
aa
Desorption
Aqueous Phase Volume (m£) V.
c
7Td
'd
Total Sample Volume Removed (m&) V
Total Count (cpm) N ,
Id
Aqueous Sample Volume Removed (m£) V
ad
Aqueous Count (cpm) N
ad
Glass
Total Glass Count (cpm) N
o
Volumes for all experiments
V± = 10-15 m£
VTa = VTd - l m*
V = V , = 1 mil
aa- ad
Final Concentrations
Conversion factor
fo = (940 ng/£)/(515000
Initial Concentration
c. = f N . V . /V.
i o sk sk i
Initial HCB Mass
h. = f N , V ,
i o sk sk
20
-------
Table III-l (cont'd)
Adsorption
Total Concentration
CTa = fo NTa/VTa
Aqueous Concentration
c = f N /V
a o a aa
Particulate Concentration
r
a
(cTa - ca)/(ma
10~3 g/mg)
Desorption (Experiment Type 2 and 3)
Sediment Concentration
m,
"a
-------
The data generated during the course of these experiments is presented in
tabular form in the Appendix of this report if it is not included in the body
of the report.
B. Mass Balance of HCB
In order to check that the experiments were properly executed, HCB mass
conservation was checked. The initial mass of HCB added, h. must be accounted
for at the end of the experiment. The most direct check is to compute the initial
HCB mass adsorbed to the vessel:
go = (ci - CTa)Vi (III-r>
where c. is the initial concentration from the diluted stock solution, c
1 • . icl
is the total HCB concentration at adsorption equilibrium, and V is the volume
of solution. This is compared to the computed change in mass adsorbed to the
glass after desorption equilibrium (for Type 3 experiments):
' «1 ' (CTd - rama)Vd t111-2'
and the observed glass concentration, g_ at the end of the experiment. The
mass balance error is this difference normalized by the total initial HCB
mass added to the vessel, h.. Thus the mass balance error in percent is
et = 100% (g2 - g0 -
A histogram of this error is shown in figure III-3. Typically the error is
VLO% which indicates that the recovery of HCB mass is on the order of 90%.
C. Vessel Adsorption of HCB
Preliminary experiments indicated that HCB adsorption to vessel walls is
a significant problem. Studies on a variety of potential vessel materials
(Figure III-4) indicated potentially serious HCB lo.sses could occur from
dilute solutions (<1 yg/£) even during relatively short reaction periods
(hours). Aqueous solutions were observed to lose more than 80% of the
initial HCB concentration (40 ng/Jl) to organic reaction vessel surface
(polyethylene, polycarbonate, teflon) in less than 2 hours. The results
suggested that Corex (Corning Glass Co.) adsorbed slightly less HCB than
did Pyrex (Corning Glass Co.). Experiments conducted on metal surfaces
(Figure III-5) showed uniformly rapid uptake. Under quiescent conditions
chrome, gold, copper and nickel coated surfaces all displayed HCB losses
from solutions of > 80% in a matter of hours. Experiments on stainless
22
-------
35
30
o 25
LU
o
UJ
DC
20
> 15
jjj 10
0
-80
N=197
-60 -40 -20 0 20 40
MASS BALANCE ERROR, e, percent
60
80
Fig. III-3. Histogram of Mass Balance Error, e (%)
-------
ADSORPTION TO VESSEL WALLS
INITIAL SOLUTION = 35ng/l
COREX
SI LAN I ZED
PYREX
POLYCARBONATE
TEFLON
POLYETHYLENE
12345
TIME, hours
Fig. 1II-4. Adsorption of HCB to Vessel Walls
24
-------
VESSEL ADSORPTION OF HCB (METALS)
100
g 90
15
O
CO
80
70
< 60
LLJ
CC
CD
O
I
o
CC
50
40
30
20
10
QUIESCENT EXPERIMENT
0
J_
1
Q =GOLD
O = COPPER
V = NICKEL
A = CHROME
3 4
TIME, hrs
Fig. III-5. Adsorption of HCB to Metal Coated Vessels
25
-------
steel, lead and aluminum also resulted in similar rapid HCB removal from
solution.
Additional studies on Corex glass (Section V) revealed that although
solution composition affected the extent of glass adsorption it still did
not exceed ^ 10% of the initial HCB mass. Since these vessels (25 m& Corex
centrifuge tubes) appeared to be the least adsorptive they were chosen for
these experiments. An adsorption isotherm constructed from adsorption ex-
periments (type 1) in distilled water, shown in fig. III-6, confirms that
^ 10% of equilibrium aqueous concentration, c , had been adsorbed to the
3
glass wall. Both adsorption and desorption cycles used the same tube in
order that HCB adsorption to fresh vessel surfaces was reduced. This is
especially important for the desorption phase of the experiment since trans-
fer of solids to a second vessel would cause additional vessel adsorption.
D. Glass Desorption
A number of experiments were conducted to evaluate the sorption effects
of the Corex glass tubes on the desorption process. The purpose of this study
was to determine the magnitude of the effect of the glass surfaces on the aque-
ous HCB concentration, c,, during the desorption process. In these reference
studies HCB stock solutions were added to Corex tubes and allowed to equili-
brate for time periods equivalent to those used in the sediment studies. After
equilibration, aqueous HCB levels, c , were determined and the stock solutions
a
replaced with distilled water. These solutions were allowed to equilibrate with
the vessel walls after which the aqueous concentration, c,, levels were again
measured.
Data typical of the results obtained in these experiments are tabu-
lated below.
TABLE III-2
GLASS DESORPTION DATA
2
Corex Tubes (Contact Surface Area = 38 cm )
ADSORPTION DESORPTION
c c, r , HCB Adsorbed
a d gd
(ng/£) (ng/£) (ng/cm2) (ng)
18.6 2.8 .001 .037
41.6 4.0 .005 .185
81.8 8.5 .011 .418
163.6 15 .018 .684
26
-------
100.0 c
z
o
cc
h-
z
UJ
o -
z £
o g
o ~
CO t
<'
-J a"
O
Q
UJ
>
CC
LU
CO
OQ
O
1.0 =
1.0
0.1
0.01
HCB ADSORPTION-DESORPT1ON
{GLASS ISOTHERM)
i i i i tun i i i 11 mi I 11 111 ill l l l 1111
0.1 1.0 10.0 100.0 1000.0
AQUEOUS CONCENTRATION, ca, ng/l
Fig. III-6. Glass Adsorption Isotherm: Volumetric Concentration of HCB Adsorbed
to the Wall versus Aqueous Concentration, Distilled Water.
-------
These results suggest an approximate linear relationship between the
equilibrium HCB concentration for adsorption, c , and the equilibrium HCB
a
concentration observed during desorption, c . Desorption concentrations ap-
pear to constitute ^ 10% of the equilibrium adsorption concentrations. It
is, therefore, possible that of the total equilibrium HCB concentrations
observed during sediment desorption, a fraction (up to 10% of the equilib-
rium aqueous HCB concentration) may result from desorption from the walls.
This would suggest that partitioning studies may overestimate the extent of
HCB desorption from sediments and underestimate the magnitude of the desorp-
tion partition coefficient. However, since the absolute quantity of HCB ad- .
sorbed to the glass walls is small relative to the quantity adsorbed to the
sediment, even at low sediment concentrations, the glass desorption contri-
bution is also small. This can be seen in fig. III-7 which compares, on a
concentration basis, the mass of HCB on the sediment after adsorption equilib-
rium, mr , to the total HCB measured at desorption equilibrium, c_,. These
3 JL Q
observations are from all the experiments in which both quantities were meas-
ured (Type 3 experiments). The histogram of percent error: 100% (mr - c )/c
& id Id
is within ±2.5% for 48% of the observations and within ±7.5% for 72% of the ob-
servations. The observed equality indicates that glass desorption is an insig-
nificant contribution.
This fact is also apparent from fig. III-8 which compares the observed glass
concentration for type 2 experiments, g., on a volumetric basis, after the desorp-
tion cycle versus the aqueous adsorption concentration, c . The isotherm is that
a
found from the type 1 adsorption experiments (fig. 1II-6). Although the glass
concentrations are slightly lower indicating some glass desorption has occurred,
it is an insignificant quantity compared to the total HCB at desorption equil-
ibrium, c.,,. (See fig. III-7).
Id
E. HCB Speciation
It is possible that partitioning data may be affected by changes in HCB
speciation in aqueous solution. It has been suggested that at aqueous HCB
levels in excess of the aqueous solubility, molecules may bind together as
aggregates, forming a micro-emulsion rather than a true solution. Such aggre-
gates may display partitioning behavior quite different from that of only dis-
solved species. Although HCB concentrations in the present studies are well
below the solubility limits of 8 yg/£ (Dexter and Pavlou, 1977), experiments
were conducted to evaluate the possibility of solution speciation.
28
-------
Glass Desorption
10'
•o er
10'
t I » 1 1 lil
1
Relative
•H-yr*
x&
I AT.
frequency
40%
20%
Tl-^ J_rT__r— i
-29 6
% Error
f I I I I 1 1 1
28
10J
Total HCB Concentration at Desorption En«-ll. ib'rium
"Td
Fig. III-7. Adsorbed HCB Concentration at Adsorption Equilibrium, mr ,
versus Total HCB Concentration at Desorption Equilibrium,
c_., for Type 3 Experiments. Histograms of % Error = 100%
To
(mr - c ,)/c .
a Td Td
29
-------
to
c
c
o
M
4-1
a)
o
c
o
o
w
o
EC
•o
01
XI
M
o
10
V)
M
O
Observed Glass Adsorption at Desorption Equilibrium
100.0 ET
10.0 =
1.0 =
0.1 =
Glass Adsorption Isotherm
0.01
0.1 1.0 10.0 100.0 1000.0
AQUEOUS CONCENTRATION, ca, ng/l
Fig. III-8. Comparison of Glass Adsorption Isotherm (from Fig. III-6) to
Glass Adsorbed HCB after Desorption Equilibrium
-------
In these experiments stock HCB solutions were initially equilibrated
with 100 mg/£ sediment suspensions (montmorillonite clay and Saginaw Bay
// 50). After equilibration (3 hr.), the samples were centrifuged, the solid
phase discarded and the aqueous phase equilibrated (3 hr.) with additional clean
sediment. Sediment concentrations were kept constant during both equilibration
cycles. Partitioning data for the individual cycles were compared. If aqueous
stock solutions contained more than one HCB species whose partition coeffici-
ent values differed, then the consecutive adsorption process would be expected
to selectively separate such species. Table III-3 and III-4 contains the data
in the replicated experiment using montmorillonite and Saginaw Bay sediments.
Although there is a slight tendency for the second adsorption cycle partition
coefficient to be less than the first adsorption cycle, especially for the
Saginaw Bay sediment, the differences are statistically insignificant as in-
dicated from the Analysis of Variance results. The significance levels of
the F test are much larger than the usual critical significance level of 0.05
(95% significance) which indicates no statistical difference between the par-
tition coefficients found in cycle 1 and cycle 2. This suggests that the
stock solutions used in the present study did in fact contain dissolved HCB
species with no preferential adsorptive properties.
The effect of adsorption and desorption equilibration times are discussed
in the next section.
31
-------
Table III-3
Speciation Experiment - Montmorillonite
Data
Adsorption
Cycle 1
c
Cng/4)
23.97
23.25
25.84
26.58
r
a
(ng/g)
125.1
127.3
117.9
115.3
IT.
(A/kg)
5218
5478
4562
4338
Adsorption
Cycle 2
c
(ng/i)
11.64
9.18
10.13
12.12
r
a
(ng/g)
33.6
44.4
58.7
45.4
TT
a/kg)
2886
4832
5799
3746
Statistics
Overall Mean TT = 4607 (£/kg)
cl
Number of Observations = 8
Cycle N
1
2
4
4
Mean
4899
4315
IT. (A/kg)
3
Standard
Error
487
487
95% Confidence Interval
Lower Limit Upper Limit
3704
3121
6093
5509
Source
Total
a
Error
DF
7
1
6
SS
6380997
680361
5700636
MS
680361
950106
Analysis of Variance
F-Test
0.716
Significance Level
0.429
32
-------
Table III-4
Speciation Experiment - Saginaw Bay #50
Data
(ng/i)
22.12
25.98
30.53
Adsorption
Cycle 1
(ng/g) (A/kg)
118.0
98.1
204.3
4696
3775
6692
Adsorption
Cycle 2
c
(tig/i)
10.75
12.05
14.38
r
a
(ng/g)
53.5
52.0
51.7
TT
(A/kg)
4974
4311
3594
Overall Mean ir = 4673 (£/kg)
3.
Number of Observations = 6
Statistics
Cycle N
1
2
3
3
Mean
5054
4293
Standard
Error
670
670
(Vkg)
95% Confidence Interval
Lower Limit Upper Limit
3176
2415
6931
6170
Source
Total
a
Error
DF
5
1
4
SS
6269177
869442
5399734
MS
869442
1349933
Analysis of Variance
F-Test
0.644
Significance Level
0.467
33
-------
SECTION IV
KINETICS
A. Introduceion
An assessment of HCB sediment-water interactions in naural systems
requires an evaluation of the rate at which the partitioning process occurs.
Specifically, it is necessary to determine how rapidly aqueous suspensions
approach equilibrium with respect to adsorbed and dissolved HCB. Previous
work on a variety of organic compounds (Wahid and Sethunathan, 1978, Paris,
1978) has suggested that the partitioning process for physical adsorption
to sediments occurs quite rapidly (hours). The goals of the present study
were to determine time periods required for the hexachlorobiphenyl isomer
to approach equilibrium during both adsorption and desorption processes.
Experimental studies have been of both short (< 24 hours) and longer term
(1-10 days) duration.
B. Effect of Adsorption Time on Adsorption Partition Coefficient
Initial experiments were conducted on both Saginaw Bay and montmor-
illonite samples for time intervals ranging up to 24 hours. It has been
suggested that partitioning of dissolved pesticide molecules to montmor-
illonite occurs somewhat more slowly than for other clay minerals such as
illite and kaolinite (.Huang, 1970). In the present study, data for the
partitioning of HCB to 200 mg/Jl montmorillonite suspensions is shown in
Figure IV-1. The aqueous phase employed was the supernatant from a pre-
viously equilibrated HCB-free 200 mg/£ montmorillonite suspension. This
procedure was adopted in order that the aqueous phase was in equilibrium
with montmorillonite and no further dissolution of montmorillonite (if indeed
any occurred) would take place during the kinetic experiments. HCB aqueous
and sediment concentration values have been plotted, together with the ad-
sorption partition coefficient. It can be seen that the partitioning pro-
cess appears to occur quite rapidly. A slight change is observed from t =
a
15 min. to t =2 hours suggesting that the adsorption process is essentially
fl.
complete in a matter of minutes.
It has been suggested (Huang and Liao, 1970) that bonding of organic
molecules to montmorillonite may involve a two stage process. The first
state being a rapid adsorption to external particle surfaces occurring in
34
-------
c Effect of Adsorption Time - Montmorillonite
10
10
4
io3
1G1
10°
(ng/g)
A - - - ta = 2 hr.
t = 15 min
A
O 0 Q 0 ^ Q^O Q.
a
' D G = =r 0 t = 15 jnin.
i-O-nHb 0 £ t* = 2h
1 MINI I L—J I I I |JJ I I I I I I I I
-k *^ •* fl /X
0.1 1.0 10.0 100.0
Adsorption Time, t (hours)
Si
Fig. IV-1. Effect of Adsorption time, t , on aqueous concentration, c ,
sediment adsorbed HCB, r , and partition coefficient, TT .
m = 200 mg/£ Montmorillonite, Aqueous phase is supernatant.
-------
a matter of minutes or less and the second stage being a slower migration
of organic molecules into interlayer spaces. The extent of migration to
internal sites appears to be dependent upon the size, conformation, and
polarity of the organic molecule. The present results do suggest a small
decrease in aqueous HCB concentrations during the first couple of hours.
This may be related to additional migration into the solid phase. However,
the magnitude of this effect appears to be quite small. Initial studies on
200 mg/& Saginaw Bay sediment //50 suspensions using previously equilibrated
supernatant show rapid partitioning behavior similar to that observed for
montmorillonite (Figure IV-2). The adsorption appears to be essentially
complete within the first 2 hours. The scatter observed in the data pre-
cludes a more careful analysis of this type of experiment.
The results of the present experiments are supported by a number of
other studies on organic partitioning between sediment and water phases.
Sorption studies on parathion (Wahid and Sethurathan, 1978), paraquat (Juo
and Ogiani, 1978) and Arachlor mixtures (Steen et al., 1978) all suggest
the partitioning process to be complete in less than one hour.
Kinetically rapid partitioning processes such as those observed in the
present study appear to result from weak physical adsorption of organic mole-
cules at sediment particle surfaces (Goring and Hamaker, 1972). Conversely,
it has been observed that for some porous substrates such as activated char-
coal (Crittenden and Weber, 1978) reaction kinetics appear to be controlled
by the rate of diffusion or organic molecules into particle interiors. Dif-
fusion processes have also been suggested to be of importance in the uptake
of pesticides by clay flocculates (Haque et al., 1968).
To further evaluate this effect a number of experiments were conducted
to assess the potential importance of kinetically slow processes on HCB ad-
sorption from Saginaw Bay sediment. In these experiments adsorption isotherms
were constructed for experimental shaking times ranging up to one week. The
results of long term adsorption studies conducted on 1000 mg/£ Saginaw Bay
sediment samples are indicated in Figure IV-3. The results suggest that small
increases in adsorption may occur during the first 24 hours. However, these
results may be due to losses of HCB from the aqueous phase. An examination of
the data shows no observable increase in HCB sediment concentrations with time
(see Table IV-1),
36
-------
10-
io2
r~
10
10°
Effect of Adsorption Time - Saginaw Bay #50
v U/kg)
a A A
A A
A A — - - & - t = 2 hr.
rg(ng/g)
O Q Q O
c (ng/Jl)
3
D
A
A
a
0 t = 15
D —n :re a t = 2
-nQ- Q
J 1 1—I_1_LJ_U_ 1 I \ I .1 .1 1 ) f. I I III l_i_
|min.
0.1 1.0 10.0 100.0
Adsorption Time, t , (hours)
3
Fig. IV-2. Effect of Adsorption Time, t , on aqueous concentration, c ,
sediment adsorbed HCB, r , and partition coefficient, TT .
m = 200 mg/£ Saginaw Bay //50, Aqueous phase = supernatant.
37
-------
dO
tt>
C
C
O
•H
•P
0)
C
0)
o
C
O
o
o
•p
0)
CU
HCB Adsorption Isotherm - Effect of Adsorption' Time
100
80
60
40
20
•f
3 hours
1 day
5 days
10
Aqueous Concentration, c ,(ng/£)
3
Fig. IV-3. HCB Adsorption Isotherms at various Adsorption Times
'Saginaw Bay //50, m = 1000 mg/£%Distilled Water.
38
-------
ta - 3 hr.
t = 5 day
3
TABLE IV-1
SAGINAW BAY ADSORPTION ISOTHERMS
SAGINAW BAY #50, 1000 mg/£
c. c r ir Freundlich
a a a Parameters
(ng/£) (ng/gm) (A/kg)
1/n = 1.06
K =10.4
16.2
30.1
53.8
86.2
-
t = 24 hr.
a
15.2
30.4
60.8
91.3
121.7
1.11
2.50
3.46
4.92
8.6
1.0
1.7
3.4
5.2
7.4
12
24
41
68
96
12
24
46
76
82
10900
9600
11700
13600
11100
12500
14200
13600
14500
11000
15.2
30.4
45.5
75.1
121.6
0.9
1.5
1.9
3.6
6.3
11
22
34
53
84
12400
15200
17900
14800
13200
1/n = 0.97
K =13.6
1/n =1.02
K =13.9
39
-------
A comparison of all the adsorption data (Saginaw Bay #50, m = 1000 - 1100
mg/£) with adsorption times of 1 to 5 hours generated for other purposes to
the longer adsorption time data is shown in figure IV-4. Although the longer
adsorption times appear to increase the partitions coefficient somewhat, the
effect is not dramatic. A similar plot for isotherms conducted for the same
sediment at m = 55 mg/Jl, figure IV-5, show less increases for t = 48 hour when
H
compared to t =2 hour.
3,
It is concluded that although there appears to be slight effect of t
3.
on adsorption partition coefficient, TT , the effect is not large and a two
&•
hour absorption time appears to be sufficient.
C. Effect of Desorption Time on the Desorption Partition Coefficient
A major focus of this research is the desorption reaction for HCB since
very little information was available. Initial kinetic experiments were con-
ducted to examine the effect of desorption time, t,, on the aqueous and sedi-
ment concentrations and the desorption partition coefficient. Vessels were
equilibrated for t =2 hour followed by the desorption step. Vessels were
CL
analyzed for desorption times of 15 minutes to 24 hours. The results are
shown in figures IV-6 and IV-7 for montmorillonite and Saginaw Bay #50 at
m = 200 mg/£. Pre-equilibrated supernatants were again employed. Unlike
the adsorption experiments the time of desorption experiments displayed no
consistent change in sediment or aqueous concentrations as a function of
desorption time.
Because of the importance of this observation to the interpretation of
the extent of reversibility of HCB adsorption, longer periods of desorption
were employed. The difficulty with the kinetic experiment design is that
sampling fluctuations obscure the effects if only discrete points are generated
at each desorption time even if they are replicated. As shown in figure IV-8,
and Table IV-2, the sediment concentration shows a slight initial trend but
the partition coefficient varies in apparently random fashion.
A more convincing experiment is to generate full isotherms at fixed adsorption
time and at various desorption times. The reference isotherms and data (Saginaw
Bay #50, m = 1100 mg/&), for t = 3 hr and t = 2 hr, are shown in fig. IV-9.
3. Q
40
-------
HCB Adsorption Isotherms - Effect of Adsorption Time
300.0
10CLO -
00
00
c
o
c
a)
o
C
O
o
D
O
Cfl
CM
10.0
3.0
0.3
1.0 10.0
Aqueous Concentration, c (ng/i)
30.0
Fig. IV-4. HCB Adsorption Isotherms. Comparison. Saginaw Bay #50
m = 1000-1100 mg/£. Distilled Water
-------
3000.0
HOB Absorption Isotherms - Effect of Adsorption Time
1000.0
t>o
oo
a
c
o
c:
-------
Effect of Desorption Time - Montmorillonite
10 ,
10
10"
10
10
iol
0.1
rd(ng/g)
.A.
A
A A
TT
a
-OL
a
I I I I I I I I
-A—
TT
1.0
_L L l_LJJU.LI I 1—i-J J_LLL
10
100
Desorption Time, t, (hours)
Fig. IV-6. Effect of Desorption Time, t,, on Desorption Aqueous Concentration
c , Sediment Bound HCB, r,, and Desorption Partition Coefficient
n,. m = 200 mg/t, tnontmorillonite, supernatant. t =2 hr.
-------
10
10-
10
10
10
0.1
Effect of Desorption Time - Saginaw Bay //50
rd(ng/g)
a
_§.
a
-B-
1.0 10.0
Desorption Time, t, (hours)
100.0
Fig. IV-7. Effect of Desorption Time, t , on desorption aqueous concentration,
. c , sediment bound HCB, r,, and desorption partition coefficient,
TT . m = 200 mg/£. Saginaw Bay #50, Supernatant, t = 2 hr.
-------
100Q
100
10
Effect of DosorpLion Tiinu - Saginaw Bay //50
D Dosorptlon Partition Coefficient, TT ,(£/g) x 10
• Sediment Concc%ntration • r , (ng/&)
a a
a
j
6
468
Desorption Time, t (days)
a
10
t
~~1.2
1 ig. IV-8. Long Term Desorpl.ion. Sediment. Hound HCB, r. and desorption
partition (.inefficient, ••i.("/g) (x 10 for convenience in ploLting)
vcrsvis dosorption titTiO..
-------
These isotherms are compared to the adsorption and desorption data for t = 3 hr
3
and t, = 72 and 144 hrs. in fig. IV-10. A composite plot of all data is shown
in fig. IV-11. The results indicate no significant difference for the desorption
isotherm employing t. = 3 hour, 3 days and 6 days.
The conclusion is that the desorption reaction is essentially complete
after 1-2 hour and much longer desorption times have no appreciable effect
on the desorption partition coefficient obtained.
The apparent lack of full reversibility of the adsorption reaction plays
an important role in the experimental investigations that follow and the
theoretical treatment of the phenomena developed in Part B of this report.
Subsequent chapters of Part A discuss other factors that influence parti-
tioning with a view toward elucidating the possible mechanisms that may
cause this behavior.
46
-------
TABLE IV-2
LONG TERM DESORPTION STUDY
SAGINAW BAY # 50
Time
(Days)
15 (min)
1
2
3
4
7
8
9
10
11
cd
4,7
3.6
2.8
2.4
5.4
2.6
3.0
2.0
6.0
2.8
rd
(ng/gm)
55
53
50
43
47
39
36
48
42
45
U/kg
11600
14600
18200
18100
8600
15000
12100
26500
7000
15800
GI = 70.1 ng/S,
pH = 7.1 ± 0.1
47
-------
Adsorption and Desorption Isotherms - Saginaw Bay //50
300 i - -•
100.0
00
oo
c
PQ
O
ffl
'I
O
pa
i
10.c_
3;0
D Adsorption
-f Desorption
0.3
1.0
10.0
30.0
Aqueous Concentration, c , c, (ng/£)
3 O
Fig. IV-9. Adsorption (r vs. c ) and Desorption (r vs. c.)
33 O d
Isotherms: t = 3 hr., t = 3 hr. m = 1100 mg/X,
3 O
Saginaw Bay //50. Distilled Water
-------
Effect of Increasing Desorptlon Time
300.0
Adsorption D 0
Desorption - - -I- x
0.3
10.0
30.0
Aqueous Concentration, c ,
(ng/£)
Fig. IV-10. Adsorption (r vs. c ) and Desorption (r vs.. c ). Isotherms for
increasing desorption times: t = 72 and 144 hr.
Saginaw Bay //50, Distilled Water.
m = 1100 mg/«.
49
-------
V.
z
H
QC
H
Z
LLJ
O
Z
O
O
D
O
H
DC
cn
O)
c
10°
SEDIMENT CONCENTRA TION,
1.000 PPM
DESORPTION
• 2- HOUR
' 3-DAY
* 6-DAY
3- HOUR
ADSORPTION
10
-1
10° 101
AQUEOUS CONCENTRATION, ng/l
102
Fig. 3V-11. Effect of Increasing Desorption Time. Saginaw Bay #50
50
-------
SECTION V
EFFECT OF SOLUTION COMPOSITION
A. Introduction
The adsorption of organic chemicals can be affected by the state of
the aqueous phase. This is especially true of chemicals which have ion-
izable groups as part of their structure. The purpose of this section
is to present the results of these experiments. Initially temperature
variations are considered, followed by pH and ionic strength influences.
The unexpected influence of CaC&_ is discussed.
B. Temperature
Similar to many temperate zone water bodies, Great Lakes water column
temperatures vary slightly with seasonal changes. In Saginaw Bay, water
column temperatures typically range from 0°C - 30°C during a yearly cycle
(Smith et al. , 1977). Experiments were conducted to determine whether tem-
perature changes of this magnitude would significantly affect HCB partitioning.
Using Saginaw Bay sediment (//50), adsorption isotherms were constructed at
1 ± 1°C and at 40 ± 1°C. Equilibration procedures were identical to those
used for ambient temperature studies.
Experimental results are indicated in Figure V-l and Table V-l. Somewhat
surprisingly, 1°C data indicates a lower adsorption partition coefficient (IT =
3
6680 a/kg) than does the 40°C data (IT = 14780 £/kg) . Overall, these equilibrium
3-
constant values bracket the previously reported value (IT = 7240 &/kg) for ambi-
a
ent temperature and m = 1100 mg/£,
The relatively non-reversible HCB bonding implied by the partitioning
studies to be discussed subsequently appears to conflict somewhat with calcu-
lations of the enthalpy of adsorption (AH) based on variations in adsorption
with temperature. A value of AH for Saginaw Bay sediment has been estimated
from the expression,
- T
K RTT
Kl RT1T2
51
-------
HCB Adsorption Isotherms - Effect of Temperature
250
to
c
co
v,
c
o
•H
•P
o!
h
•P
C
4>
o
C
o
o
0)
•P
t)
-H
-P
>-,
03
0,
200 -
150.
10.0 _
Aqueous Concentration, c (ng/£)
3
Fig. V. Effect of Temperature on HCB Adsorption. t = 3 hr.,
m = 1100 mg/Jl Saginaw Bay //50 a
52
-------
TABLE V-l
EFFECTS OF TEMPERATURE ON ADSORPTION
Saginaw Bay:
Temperature
1°C ± 1°C
ci
29.2
58.4
116.8
175.2
233.6
Temperature
40°C ± 1°C
c .
(ng/A)
29.2
58.4
116.8
175.2
233.6
#50
Q
(ng/A)
2.7
6.9
15.7
20.6
29.4
c
a
(ng/A)
1.8
3.3
6.9
13.1
19.3
r
a
(ng/gm)
24
46
88
132
180
Average TT 6680
cl
a
(ng/gm)
28
55
111
164
214
t = 3 hr.
a
m = 1100 mg/£
IT
a
(A/kg)
8700
6600
5600
6400
6100
± 1190 A/kg.
7T
a
(A/kg)
15300
16500
16000
12500
11100
Freundlich
Constants
1/n = .86
K = 9.3
Corr. = .99
1/n = .87
K = 17.8
Corr. = .99
Average ir = 14280 ± 2356 £/kg
Si
53
-------
where K0 and K represent the equilibrium constant values for adsorption (TT )
2. 1 a
at temperatures T9(40°C) and T (1°C). The resulting positive value of AH
(^ 3.3 kcal/mole) is not what would be predicted for an exothermic adsorption
process. The small absolute value of AH is, however, similar in magnitude to
values commonly observed for weak physical adsorption to sediment (Hamaker and
Thompson, 1972). In contrast, this value is much smaller than values associ-
ated with chemisorption processes (> 10 kcal/mole) such as might be implied by
the non-singular isotherms for adsorption and desorption discussed previously
in Section IV. In addition, it should be noted that the direction of the
temperature effect is not unique to HCB and has been observed in soil-pes-
ticide studies (Spencer and Cliath, 1970; Haque and Coshow, 1971).
The observations of the present study may result from a number of factors.
First, it is possible that reaction rates for the adsorption process may in-
crease with increasing temperature. Alternately, variations in temperature
could affect the aggregation state of the sediment, with increased tempera-
tures resulting in greater dispersion.
In summary, it would appear that water temperature changes within
Saginaw Bay will have a relatively small effect on PCB partitioning pro-
cesses. From an experimental point of view, however, the temperature
variation is small enough so that changes in ambient temperature should
not cause large changes in partitioning.
C. Aqueous Phase Composition
The chemical composition of natural waters such as Saginaw Bay and
its tributaries may differ considerably from the solution conditions of
the present study. Interstitial waters, for instance, typically possess
higher ionic strength levels than are observed in the overlying water
column. Several experiments were conducted to evaluate the effects of
changes in solution composition on HCB partitioning.
Initial experiments were conducted on montmorillonite clay samples.
The chemical structure of montmorillonite is considerably simpler than that
of natural sediments and evaluation of solution composition effects is, there-
fore, somewhat easier. In addition, a one component adsorbent was used in
54
-------
order to attempt to characterize some aspects of the nature of HCB bonding to
solid surfaces.
Figure V-2 depicts the results of experiments conducted to assess the effect
of pH on HCB partitioning to 200 mg/£ montmorlllonite suspensions. In these ex-
_3
periments, solution pH levels were adjusted by incremental additions of 10 M HC1
or NaOH and the suspensions allowed to equilibrate for several hours prior to
HCB addition. This was done to minimize the occurrence of pH shifts during the
course of the experiment. In all reaction solutions the total Na and Cl con-
—4
centrations were maintained below 5.10 M. The results indicate a significant
reduction in HCB adsorption by the clay as pH levels were increased over a range
from pH = 4 to pH = 10. The data suggests a rather abrupt decrease in ir as
a
solution pH levels are increased from pH = 6 to pH ~ 8. Values of TT for acidic
a
solutions (pH<6) are approximately 2-3 times greater (TT ^12,000 £/kg vs. IT
a a
^4000 £/kg) than those observed under more basic conditions (pH>7).
The overall variation in TT may reflect changes in montmorillonite par-
a
ticle surface charge characteristics resulting from pH changes. It is known
that while montmorillonite particle surfaces are negatively charged above pH
'v/ 4, the charge on particle edges is pH dependent (van Olphen, 1963). .Under
acidic conditions (pH<5) particle edges are positively charged. However, as
pH levels are increased from pH = 6 to pH = 8 edges undergo a neutralization
reaction which, with continued pH increases, may result in the development
of negative charge sites. This would suggest that the abrupt decreases in
TT as solution pH levels increase above pH = 6 may be related to changes in
a
the charge characteristics of particle edges.
The "poTential importance of solid phase charge characteristics to HCB
adsorption is also suggested in comparisons of variations in TT with changes
a
in solution composition. In experiments designed to evaluate the effect of
solution ionic strength on HCB adsorption, the NaCl concentrations of 200
mg/£ montmorillonite suspensions were systematically varied. As indicated by
figure V-3, the value of n was relatively little affected by increasing NaCl
-4 a -2
concentrations from 10 M to 10 M. Partition coefficient values fluctuated
55
-------
14
60
o?
12
£•10
LU
o
UL
LL.
LU
O
O
O
b
i-
oc
<
Ou
8
6
0
200-PPM MONTMORILLONITE
CONCENTRATION
_L
JL
JL
_L
JL
6
pH
7
8
10
Fig. V-2. Effect of pH on HCB Partitioning to Montmorillonite
56
-------
Effect of Ionic Strength Variation
30
25
00
o?
.« 20
15
•LJ
e
0)
0)
o
u
c
o
M 10
n)
10
O
9
o o
o
o
o
•+ CaCl,
^
O NaCl
-1—I I I I Illl \ I i I i I in I i i I I I HI i i i I ii u
10
10
Molarity
10
-2
10
-1
Fig. V-3. Effect of Increasing Ionic Strength using NaCl and CaCl2
on HCB Adsorption Partition Coefficient for Montmorillonite.
m = 200 mg/£. t = 4 hr.
57
-------
between 10000 £/kg and 14000 £/kg with some evidence for a gradual increase in
TI with.increasing NaCl concentration. However, in similar experiments in which
3
CaCl» concentrations were systematically varied, TT increased from M1000 £/kg
- -4-2 a
to >25000"£/kg over a 10~ M to 10 M concentration range. It is unlikely that
this effect is the result of changes in HCB solubility since aqueous HCB concen-
trations were over an order of magnitude below reported HCB solubility limits
(Dexter and Pavlov, 1978).
Dilute artificial seawater solutions appear to yield partition coefficient
values intermediate between NaCl and CaCl~ solutions (Table V-2). Interestingly,
the presence of dissolved humic acid (Aldrich Chemical Co,) at concentrations
achievable in natural waters did not appear to significantly alter the observed
partition coefficient values. Increases in hunic acid concentrations from 5-50
ppm did not significantly affect partition (Table V-2). Thus it appears that
HCB is not being strongly complexed by the organic phase. Nor does the humic
acid appear to be competing with HCB adsorption sites on the clay particles.
The effect of CaCl_ on HCB partitioning was confirmed in isotherm studies
conducted on both montmorillonite and Saginaw Bay sediment samples. As demon-
strated in figure V-4, for HCB adsorption onto 220 mg/S, montmorillonite suspen-
sions, TI increased from ^000 2,/kg in distilled water to V35000 in .01M Cad,.
3 • £.
For 220 mg/i Saginaw Bay sediment suspensions (figure V-5), somewhat smaller
increases in TT (12,000 to 25,000 A/kg) were observed. For both solid phases
a
the results suggest that isotherms in .01M CaCl maintain the linear behavior
observed for the distilled water and supernatant systems.
It is interesting to note that in preliminary experiments on vessel
absorption it was also observed that the presence of .01M CaCl increased the
adsorption of HCB by glass surfaces and a pH effect was found. The adsorp-
tion process was found to be pH dependent with more extensive adsorption oc-
curring at pH = 3 than at pH = 11 (Figure V-6). By contrast, the solution
pH appeared to have little effect on the adsorption of HCB by polyethylene.
Under basic conditions the glass surfaces may be expected to display more
negatively charged surfaces possibly impeding adsorption of HCB. In this
regard it is of interest to observe the effects of electrolyte composition
on HCB partitioning to the vessel.
58
-------
TABLE V-2
Adsorption vs. Chemical Composition
Montmorillonite, m = 200 mg/Jl
Composition
Distilled H20
0.001M NaKH_PO *
2 4
0.002M NaCl
0.01M NaCl
0.01M CaCl0
Artificial Seawater
1.8 gm/kg
3.8 gm/kg
Humic Acid (Dissolved)
5 mg/£
10 mg/£
50 mg/£
PH
6.9
7.2
6.9
6.9
6.9
_
*" "
6.7
6.7
7.1
c
a
(ng/O
15.0
12.2
10.7
9.3
4.6
6.3
5.1
14.6
22.8
12.5
r
a
(ng/gra)
79
98
96 •
126
130
94
75
76
104
70
7T
a
(A/k
6000
8000
9200
13,500
28,000
15,000
14,600
5000
5000
5500
Composition: H PO, = 0.001M
0.001M
Na
0.0008M
59
-------
500
oo
Effect of CaCl. on HCB Adsorption
Montmorillonite
IT = 35,000 £/kg
ct
TT = 5000 fc/kg
3.
O 0.01M CaCl2
Distilled Water
10
20
30
50
Aqueous Concentration, c (ng/£)
3.
Fig. V-4. Adsorption Isotherm for Distilled Water and 0.01M CaCl
m = 220 rag/& Montmorillonite
60
-------
500
AGO
60
60
PQ
O
X
I
o
4-1
e
3
•H
•a
0)
to
300
200-
100-
Effect of CaCl- on HCB Adsorption
Saginaw Bay #50
O0.01
O Distilled Water
0 10 20 30
Aqueous Concentration, c (ng/£)
3.
Fig. V-5. Adsorption Isotherm for Distilled Water and 0.01M CaCl_.
m = 220 mg/A Saginaw Bay #50
61
-------
140
o-
KJ
INITIALHCB^25ng/l
3— PH~~11 COREX GLASS
pH~~3COREXGLASS
9ALL DATA POINTS ARE
DUPLICATE SAMPLE
AVERAGES
pH= 11 POL YETHYLENE
/ pH = 3 POLYETHYLENE
•a—-a~-ft/
I T^ I I
23456
TIME, hrs
Fig. V-6. Effect of pH on Vessel Adsorption of HCB
8
-------
Experiments indicated that significantly more HCB adsorption to Corex
occurred from 0.1M CaCl,. solutions than from 0.1M NaCl solutions (figure
V-7). More than 50% of the initial 40 ng/H HCB concentration was adsorbed
onto vessel walls from a 0.1M CaCl- solution. Once again, solution composi-
tion (0.1M NaCl) appeared to have no observable effect on HCB adsorption to
polyethylene.
It has been reported that natural sediments as well as clay minerals
possess negatively charged surfaces (Neihof and Loeb, 1972). In addition,
I I
it is well known that Ca is more effectively adsorbed at particle surfaces
than is Na (van Olpen, 1963). Thus it would appear that increased sediment
adsorption of HCB in the presence of CaCl? may be the result of neutralization
of surface charge. This interpretation of the CaCl- data would appear to be
consistent with the pH results. In these experiments HCB adsorption was
significantly reduced under pH conditions (pH>7) which should have favored
maximization of negative surface charge. It is interesting that adsorption
of the neutral HCB moleclue should be as significantly affected by surface
charge as it appears to be.
CaCl- may also affect sediment aggregation and particle size. It is
possible that CaCl« may increase partitioning by flocculating extremely
small sediment particles (<0.1u) which might otherwise remain suspended
in distilled water even after centrifugation. HCB adsorbed on such par-
ticles would appear to be dissolved rather than adsorbed. The effect would
be to reduce the calculated equilibrium constant value. Experimentation con-
ducted to test this hypothesis proved inconclusive. In one experiment, sedi-
ment solutions were added to reaction vessels and subsequently centrifuged.
The supernatant solutions were then discarded and replaced with distilled
water after which tritiated HCB was added. The results did not show any
significant increase in partitioning when compared to samples treated in
the standard manner. However, it has been reported (Karickhoff and Brown,
1978) that shaking natural sediment materials may result in redispersion
of the sediments into finer and finer particles. This may occur in the
present experiments.
63
-------
INITIAL HCB = 40 ng/l
0.1M NaCI
pH = 9.2 COREX GLASS
0.1M CaC/2
= 8 COREX GLASS
'ALL-DATA POINTS ARE
DUPLICATE SAMPLE
AVERAGES
0.1M NaCI POL YETHYLENE
A.
i i
TIME, hrs
Fig.-V-7. Effect of Solution Composition on Vessel CGlass) Adsorption of HCB
-------
In summary, it has been shown that although pH effects are observed
in the range pH = 5 to pH = 7, the effects of higher pH values, more common
in surface and interstitial waters, is small. Ionic strength effects are
slight if NaC£ is used. However, the effect of CaCl2 is marked. This sur-
prising result may be due to neutralization of surface charge changes re-
I i
suiting from Ca adsorption.
65
-------
SECTION VI
SEDIMENT COMPOSITION EFFECTS
A. Introduction
The composition of the adsorbent is known to strongly affect the degree
of adsorption of organic chemicals. For PCB's a number of investigators have
proposed that various sediment properties can be used to correlate to adsorp-
tion partition coefficient. This is discussed in more detail below.
From the point of view of an analysis of PCB distributions in Saginaw
Bay, it was apparent that PCB adsorption partition coefficients were not well
enough known for Saginaw Bay sediment to be used in the fate computations
that were planned and are currently underway. Thus Saginaw Bay samples from
various locations were analyzed to establish the relevant relationships.
B. Saginaw Bay Field Samples
Saginaw Bay is a relatively large arm of Lake Huron. The inner half of
the Bay is quite shallow (mean depth = 5m) with bottom sediments ranging in
composition from sand to clay. The large area and varied bottom composition
suggest that HCB partitioning to sediments may vary significantly depending
on location. For this reason, HCB partitioning studies were conducted on a
series of field samples collected from different inner Bay locations.
Grab samples of the top 6" of the bottom sediments were taken from a
number of locations throughout the inner Bay area (Figure VI-1). Locations,
given in Table VI-1, were selected in an attempt to gather samples reflect-
ing varying sediment composition. After collection (September 21-22, 1979)
samples were refrigerated (5°C) but not frozen. (Station //50 was collected
in August, 1978).
Sediment size fractions were characterized in a series of hydrometer
studies (Table VI-2). The sediments vary in texture from predominantly sand
(#19, #53, #69). to predominantly silt (#31, /M3, //50). In general, samples
from the middle Bay area contain much higher percentages of fine materials
66
-------
SAGINAW BAY SAMPLING AREA
SCALE:
SAMPLING STATION
BAY CITY.'1
Fig. VI-1. Location Map for Sediment Samples
67
-------
TABLE VI-1. Sampling Locations for Saginaw Bay
Station //
Location
Water Depth
(ft)
Sediment
Characteristics
19
31
43
50
53
69
Saginaw R.
43°54.2'N 83°35.7'W
43°50.8' 83°40.5'
43°47.3'
43°45.5'
43°43.8'
83°42.9'
83°42.9'
83°50.4'
83°33.5'
83°51.8'
25
26
24
25
15
12
15
Muddy Sand
Silty Mud
Silty Mud
Mud
Muddy Sand
Sand
Mud
68
-------
TABLE VI-2. Sediment Size Distribution For Saginaw Bay
Station
#19
//31
#43
#50
#53
#69
Saginaw River
Sand >62p
Silt l-62v
Clay
-------
than do sites .located closer to the shore areas. Fine clay fractions (-'liO
range from .^ 0.1% for Station #69 in the peripheral sand zone up to ^ 4%
(//31) in the middle Bay.
General chemical characteristics of the sediments are tabulated in
Table VI-3. Sediment organic contents were determined by wet digestion
using the Wakley-Black method. Surface area values were determined by single
point BET nitrogen analysis. Volatile solids were calculated from gravi-
metric changes resulting from heating to 500°C after initial drying at 100°C.
Organic matter varies from 0.1% (Station //69) to 5.4% (Station //31). The
organic content appears to be inversely related to general particle size
suggesting that most of the organic matter is present in the fine fractions.
Organic concentrations in the sandy stations (#19, #69) are <1%. Similar
correlations appear to exist between particle size in the major cations and
phosphorus. The reason for the high Ca and Mg levels in the Saginaw River
sample may reflect high levels of human activity in the immediate area.
HCB adsorption and desorption isotherms were constructed for each sam-
ple. Samples were wet seived and the <75y fraction used in these studies.
Station #69 which consisted largely of sand was wet seived and only the >75u
fraction used in the analysis. The characteristics of these seived subsam-
ples are listed in Table VT-4. Adsorption studies were conducted using 1100
mg/£ (except #69 for which m = 20,000 mg/£) sediment concentrations and 3 hr
3
equilibration times. Following the adsorption phase, 2 hour desorption studies
were performed at sediment concentrations of 990 mg/Jl (except #69 for which
m, = 18,000 mg/!l). For each sediment sample, isotherms were constructed on
the basis of 5 points, each being the average value of 3 replicates as usual.
The results are presented in Figure VI-2. Tabulated data is included
in the Appendix. Freundlich isotherm parameters and partition coefficient
values have been summarized in Table VI-5. With the exception of Station #69
the samples appear to display relatively uniform adsorption behavior. K values
cL
range from 9-16 and IT values from 9500-15000 A/kg. Slope values (1/n ) for the
Freundlich plots range from 0.93-1.15 suggesting relatively linear behavior. The
desorption data exhibits considerably greater variability with 1/n values ranging
from .94 to 1.47 and K ranging from 13.6 to 35.2. Desorption partition coeffi-
70
-------
TABLE VI-3. Chemical Characteristics of Saginaw Bay Sediments
Total Sample
-------
TABLE VI-4. Chemical Characteristics of Saginaw Bay Sediments
Seived Subsamples
Saginaw Bay
Station //
19
31
43
50
53
69**
Saginaw River
Montmorillonite
Surface area
a(m2/g)
17.0
17.8
15.9
12.8
7.0
0.2
8.4
12.6
% Volatile Solids
15.0
9.9
9.3
7.6
8.7
0.3
9.6
0.0
**
Single Point BET Nitrogen Determinations
For the >. 75y Fraction
72
-------
TABLE VI-5. Sediment Partition Coefficients and Freundlich Isotherm Parameters
Saginaw Bay
Station //
19
31
43
50
53
69
Saginaw R.
Montmorillonite
IT
a
14.83
12.27
10.67
7.01
11.18
0.036
9.63
2.10
Adsorption
m = 1100
'""a
0.97
0.93
1.14
0.91
0.94
-
0.95
-
mg/X,
K
15.7
14.1
9.3
11.3
12.6
-
10.6
-
(A/8)
30.13
30.85
26.09
20.22
19.76
0.052
22.43
7.23
.Desorption
990 mg/X,
l/nd
1.17
0.94
1.50
1.10
1.28
-
1.37
-
Kd
26.0
35.2
22.6
29.3
13.6
-
14.6
-
20,000 mg/Z sediment concentration for adsorption and 18,000 mg/£ for desorption
-------
o>
o>
c
Z
O
r-
O
z
o
O
HI
O
H
103
• r..nnplf.' (idirt S
1 9
-1//» = 1.17
K ?6.0 /
/
' Mn - 0.97
AT * 15.7
DLSOHPJ'ION
-/ • ADSQHPFION
I.. -_I. 1..J-I J 1._1..LJ
10° io1 io2
S.implc (nun Si .111 on 31
Mn - 0.94
•/ Mn - 0.93
K = 14.1
/
.1 _j I_JLJ j i_.i ~iJ
10°
10'
IO2
102
10°
Mn= 1.47 /
K = 22.6 '
1/n= 1.14
Sample from Station 43
~ Sample from Station 50
-Mn = 1.10
.AT =29.3
10'1
10°
101
/ J-4/1//7 = 0.91
x* ./ ** - 11 i
;/ / ^ 3
1 l-.l_l..l.__l I U
10° TO1 102
101
Sample from Station No. 53
Mn = 1.28. /•' X'
K = 13.6 /* /* 1//> = 0.9'
./ S r _ , - -
/x
* ADSORPTION
• DESORPTION
10
Sample from Saginaw River
~1/A7= 1.37 S S
./f-14.6/ /'
- /
'V*
AT? 10.6
10°
101
10' I J 1- I I I L_
10? 10° 10f
10'
AQUEOUS CONCENTRATION, ng/l
Fig. VI-2. HCB Adsorption and Desorption Isotherms for
Saginaw Bay sediment samples m = 1100 mg/S,
74
-------
7.0
Sample from Station #69
"Baginaw Bay
t>o
60
c
c
o
TJ 1.0
cd
H
u
C
(1)
O
o
u
0)
-------
cients, TT , ranged from 7000 to 30,000 £/kg. For all of the stations IT and
a a
K values were observed to be higher for desorption than for adsorption sug-
gesting that the partitioning process was not completely reversible. Station
#69 displayed dramatically reduced partitioning (TT = 36 £/kg) for adsorption
cl
and almost reversible behavior, TT = 52 £/kg (see fig. VI-3).
C. Saginaw Bay Suspended Matter
Samples of suspended matter were collected at Station #31 during a ver-
tical plankton tow (9/30/79). Samples were stored in bay water. A portion
of the samples were allowed to settle for 3 days at which time settled and
suspended fractions were separated. Subsequent adsorption experiments were
conducted on 500 ppm solutions of both total suspended samples and on the
fraction remaining in suspension after 3 days. The results of 3 hr adsorp-
tion and 2 hr desorption studies are indicated in Figure VI-4 and Table
VI-6. Partition coefficient values for adsorption onto total samples were
somewhat higher (TT = 6200 £/kg) than values observed for the suspended
cl
supernatant (IT = 3400 i/kg) . The higher values observed for the mixed
cl
samples may reflect higher percentages of organic material. However, no
chemical analyses were performed on the sediment material.
Partition coefficient values for the suspended sediment samples appear
to be similar to,, although somewhat less than, values for Saginaw Bay bot-
tom sediments. In studies on Arochlors 1016 and 1242 Paris et al. (1978)
reported partition coefficient values for freshwater pond seston (TT ^ 1000
3
£/kg) to be similar to values observed for bottom sediments but somewhat
less than values for suspended bacteria (TT ^ 6000 A/kg) . Conversely,
3
Hiraizumi et al. (1979) has reported much higher partition coefficients for
marine suspended solids compared to bottom sediments suggesting that the for-
mer possess higher specific surface areas.
D. Results and Discussions; Partition Coefficients
The differences in values of tr for adsorption (jr ^ 12000 £/kg) and de-
3.
sorption (IT ^ 30000 £/kg) of Saginaw Bay suspended matter appear to indicate
76
-------
o>
o>
c
102
O
h-
cc.
H
LU
o
z
O
O
UJ
o
H
QC
102
101
Settled Sample
DESOKPTION
ONJ
^ADSORPTION
J I i i .1 i i .1 .i_J i iii
Mixed Sample
DESORPTION
icr1 10° 101 io2
AQUEOUS CONCENTRATION, ng/l
Fig. VI-A HCB Adsorption and Desorption Isotherms
Station //31 on total and suspended solids samples.
77
-------
TABLE VI-6. HCB Partitioning to Saginaw Bay Suspended Matter
Adsorption (2 Hr,
Material
Settled
Mixed
•
Desorption (2 Hr,
Settled
Mixed
m = 500 mg/A)
3
c , c
i a
(ng/A) (ng/A)
15.3 8.3
30.6 15.5
45.9 17.1
76.5 43.9
15.3 3.5
30.6 6.3
45.9 10.1
76.5 28.2
md = 500 mg/A)
1.9
3.2
3.4
6.1
1.4
1.6
2.2
4.9
r
a
(ng/gm)
26.
52
60
150
Average IT
3
22
42
62
164
Average TT
3.
20
46
46
118
Average TT
Si
18
37
60
155
Average TT
a
IT
a
(A/kg)
3100
3500
3400
3400
= 3350 + 160 A/kg
6400
6700
6100
5800
= 6230 + 350 A/kg
11800
14400
15100
21300
= 14400 + 3660 A/kg
13100
23000
27000
32000
= 23700 + 8030 A/kg
78
-------
that the adsorption process is not readily reversible. Similar results were
also obtained for other Saginaw Bay sediments (Table VI-5). Adsorption par-
tition coefficients (TT ^ 9000-14000 £/kg) appeared to be consistently lower
3.
than those observed for desorption (IT ^ 20000-33000 i/kg). By comparison,
sand from which the fine fractions (< 75u) had been removed by washing, dis-
played dramatically reduced HCB adsorption. Partitioning results for 20,000
mg/£ sand suspensions (Station //69) showed only small differences between ad-
sorption and desorption isotherms (TT ^ 40 £/kg, TT ^ 60 A/kg) suggesting
a d
relatively reversible behavior.
The partition coefficients derived from the isotherm studies have been
compared to values of TT calculated from measurements of PCB concentrations
SL
in aqueous and suspended sediment samples taken from Saginaw Bay (Richardson,
personal cummunication). Mean values of TT (£/kg) computed from field data
3,
for suspended solids > 0.7y vary from 13,000-36,000 fc/kg closely resembling
the range of HCB it values (Table VI-7). Although possibly fortuitous, this
d
correlation does suggest that Great Lakes PCB concentrations are in fact con-
trolled by sediment-water interactions as has been proposed for estuarine
environments (Pavlov and Dexter, 1979), In addition, these results also tend
to support the hypothesis that natural water PCB concentrations may be pre-
dominantly comprised of the more highly chlorinated PCB compounds.
E. Effect of Particle Size and Organic Content
In natural waters, such as Saginaw Bay, the physical and chemical vari-
ables characterizing the system may undergo significant changes with time.
Effective application of laboratory partitioning data to such regimes requires
a determination of those factors capable of controlling or altering the magni-
tude of the partitioning process. The difference in partitioning observed
between the sand (Station #69) and the finer sediment fractions suggest that
the magnitude of adsorption and possibly the extent of reversibility may be
related to the physical and chemical properties of the sediments. Both
organic matter (Chiou et al., 1977; Karickhoff et al., 1979) and surface
area (Hiraizumi, 1979) have been suggested as controlling the magnitude of
partitioning to sediments.
79
-------
TABLE VI-7. Representative PCB Concentrations
For Saginaw Bay Suspended Solids*
Study
Segment**
1
2
3
4
5
Volume Weighted
Suspended
Solids (> 0.7u)
mg/2.
17.7
12.6
15.5
4.2
13.1
Averages for Arochlor 1254
Dissolved
PCB Cone.
ng/£
16.2
13.5
18.0
25.8
41.9
Particulate
PCB Cone.
ng/g
384
482
286
320
548
Partition
Coefficient
tt/g)
23.7
35.7
15.9
25.8
13.1
*
Data furnished by EPA Large Lakes Research Station, Grosse lie, Michigan
**
Data for each study segment represents mean values for results from 12
cruises
80
-------
In the present study both effects were investigated for adsorption and
desorption partition coefficients. Figure VI-5a presents the relationship
between partition coefficients and specific surface area. Although the
Saginaw Bay sediments exhibit a reasonable relationship, the montmorillonite
results are not in conformity with the trend. Figure VI-5b presents the re-
lationship between partition coefficients and percent volatile solids. Again
a trend is evident, however, montmorillonite and the sandy Station #69 sedi-
ment are not both in conformity. Although both these samples are low in per-
cent volatile solids montmorillonite has a significantly higher surface area.
In an effort to further clarify the role of the sediment organic matter ,
samples of Saginaw Bay sediment (#50) were stripped of their organic coatings.
In these experiments organic matter was removed by either chemical oxidation
(H_0?) or dry ashing. Partition coefficient values for the remaining inorganic
fractions were found to be markedly reduced by both processes (TT (H-0,,) £ 5000
5,/kg, TT (ashing) ^ 600 il/kg). These results suggest that loss of the sediment
3-
organic fraction reduced HCB partitioning to Saginaw Bay sediments. Results
from this type of experiment must, however, be interpreted with caution since
the extraction process may significantly alter the chemical characteristics of
the inorganic sediment fraction. This suggests that both independent variables
(organic matter and surface area) are important and the proper method of analy-
sis is a regression that includes both of these effects.
The results of a multiple linear regression are shown in Figure VI-6 and
Table VI-8. The estimated partition coefficients are calculated using the
listed equations. The fit is quite good for both equations, as indicated by
2
the magnitude of the variance removed (R ), The small - and for practical
purposes negligible - constant terms in the regression correctly reflect the
fact that partitioning is small for both small percent volatile solids and
specific surface area. Strictly speaking the constant coefficients should
be exactly zero. The inset in Figure Vl-6 illustrates the cross correlation
between surface area and percent volatile solids for the sediments considered.
The presence of montmorillonite and the sandy Station #69 sediment prevents a
strong cross correlation which would weaken the ability of fhe analysis to
discriminate between these two effects.
81
-------
5 10 15
Surface Area (nr/g)
(Single Point BET - N2)
4J
C
0)
•H
U
-------
00
u>
ADSORPTION
D DESORPTION
0 10 20
PERCENT VSS
10 20 30 40
OBSERVED PARTITION COEFFICIENTS u/g>
Fig. VI-6. Comparison of Estimated Partition Coefficient using Regression
Equation to Observed Values.
-------
TABLE VI-8. Multiple Linear Regression Results
Partition Coefficient
Adsorption
Desorption
Constant
0.46
0.516
Surface Area Coefficient
Wg)/0n2/g)
0.103(0.11)
0.652(0.277)
% Volatile Solids
0.903(0.13)
1.537(0.268)
Multiple Regression
R2
0.945
0.949
TT = 0.46 + 0.103 a + 0.903 (% VSS)
a
TT, = 0.516 + 0.
d
a + 1.
Standard Error of the Coefficient
84
-------
It does not appear that the observed non-singular HCB isotherms can be
readily related to bonding with the organic fraction of the sediments. As
shown in Table VI-8, the regression coefficients for both the specific sur-
face area and percent volatile solids increase when desorption is considered
relative to adsorption. Further HCB isotherms for montmorillonite and kao-
linite clay samples also displayed nonsingular behavior as shown subsequently
in Part B of this report. For 1100mg/£ clay suspensions, HCB adsorption onto
montmorillonite (IT = 2100 £/kg) was found to be substantially greater than
a
that observed for kaolinite (IT * 1060 &/kg). Desorption values for both
a
montmorillonite (rr = 9700 fc/kg) and kaolinite (IT ^ 3300 fc/kg) were signifi-
cantly larger than the respective adsorption values. The differences in HCB
partitioning between the two clays probably reflects the fact that montmor-
illonite possesses a substantially greater surface area than does kaolinite.
These results indicate that both organic content and surface area are
important determinants of the extent of HCB adsorption. The regression
equations can be used to predict the partition coefficient for adsorption
and desorption. However it should be pointed out that these partition co-
efficients apply only to sediment concentration of m = 1100 mg/Jl. As shown
in the next section, the sediment concentration itself exerts a strong in-
fluence on the measured adsorption partition coefficient.
85
-------
SECTION VII
SEDIMENT CONCENTRATION EFFECTS
A. Introduction
The application of the results of laboratory trace organic partitioning
studies to natural waters often involves extrapolating experimental data to
systems possessing markedly different physical and chemical characteristics.
This problem is well recognized with respect to the potential effects on par-
titioning of variations in the chemical composition of natural waters. Less
consideration, however, has been devoted to the possible influence of the large
variations in sediment concentrations which can occur in natural systems.
Sediment concentrations typically occurring in lake surface waters may differ
by many orders of magnitude over those found in bottom sediments or in adja-
cent drainage basin soils. Suspended solids concentrations in the Saginaw
Bay water column typically range from 10 - 500 mg/£ (Smith, et. al. 1977).
Bottom waters may reach 1000 mg/£ while underlying sediments may approach
500,000 mg/£. During sediment erosion within the drainage basin, PCB com-
pounds may be subjected to this entire range of solid phase concentrations.
In the development of models for the fate of chemicals in the environment
the experimental results of partitioning studies conducted at one suspended
solids level may be extrapolated to systems of very different sediment concen-
trations. Such extrapolations may be inappropriate if partition coefficient
values are affected by sediment concentration variations. Any systematic vari-
ations in the HCB partitioning with sediment concentration could have a signifi-
cant impact on the overall cycling of PCB in the Saginaw Bay water column and
the underlying sediments.
An attempt was made to evaluate the possible influence of sediment con-
centration on HCB partitioning. While there have been a number of studies on
PCB binding to soils and.sediments (Haque and Schmedding, 1976; Dexter, 1976;
Steen et al. 1978; Hiraizumi et al. 1979; Lee et al., 1979; Farquhar et al.,
1979) there appears to be relatively little available information on the
possible influence of sediment concentration. As previously indicated such
information is of potential importance in attempting to accurately predict
the chemical cycling of organics compounds such as PCB's.
86
-------
A review of the literature on organic adsorption to soils and sediments
reveals no consistent trend in the reported magnitude of the influence of sed-
iment concentration changes on partitioning. Studies on DDT, heptachlor and
dieldrin adsorption to natural clays (Huang and Liao, 1970) suggested that
partitioning of these compounds may vary as a function of sediment concentra-
tion. Similar effects have been observed in investigations on the adsorption
of lindane to lake sediments (Lotse et al., 1968) and kepone to estuarine sed-
iments (Connolly, 1980). Conversely, Karickhoff (1979) did not find evidence
chat sediment concentration changes significantly affected pyrene and methoxy-
chlor partitioning. Observations of the possible influence of sediment concen-
tration on partitioning do not appear to be limited to organics and have also
been reported for trace metals and radionuclides. (see the review by O'Connor
and Connolly, 1980, and the references contained therein). Figure VII-1 from
their report illustrates the effect. It is the purpose of this section to re-
port the results of studies conducted to determine the extent of the effects
of sediment concentration variations on HCB partitioning.
B. Isotherms
In initial experiments designed to characterize HCB partitioning, iso-
therms were constructed for a series of differing sediment concentrations.
These studies were conducted on both Saginaw Bay sediment and montmorillonite
clay samples. As indicated by figure VII-2, adsorption isotherms constructed
at m = 1100, 220 and 55 mg/fc concentrations of Saginaw Bay #50 sediment sug-
gest that HCB adsorption increases with decreasing sediment concentration.
Partition coefficient values, in order of decreasing sediment concentration,
were TT <= 9900, 12,300 and 17,100 A/kg respectively. The data suggest that
Si
all of the isotherms are essentially linear over aqueous HCB concentration
ranges investigated.
The results of similar isotherm studies conducted on montmorillonite clay
are depicted in figure VII-3. Again it can be seen that decreasing sediment
concentrations resulted in increased HCB partitioning to the solid phase. For
m = 1000, 200 and 50 mg/£ sediment concentrations, partition coefficient values
were found to be TT = 2900, 6690, and 10,600 £/kg, respectively. The isotherms
3
87
-------
00
00
10'
_ 10'
X,
CT
—i
•c
D1
O>
3.
2
UJ
a
o
u
S .
cr
10-
10'
• -DDT
I -HEPTACHLOR
0-LINDANE
ft-KEPONE
B - MANGANESE
*- CADMIUM
A-COBALT
k - CALCIUM
i - STRONTIUM
10'
I02 I03 !04
SEDIMENT CONCENTRATION, m
-------
Effect of Adsorbent Concentration - Saginaw Bay
700 -
Aqueous Concentration, c (ng/£)
3
Fig. VII-2. Adsorption Isotherms for m = 55, 220, and 1100 mg/fc
Saginaw Bay #50
89
-------
appear to be essentially linear, although the ra = 50 mg/£ data does dis-
play some scatter. A comparison of these data suggests that montmorillonite
displays a more marked variation in HCB partitioning with sediment concentra-
tion than does the Saginaw Bay sediment.
There exist a variety of factors which could conceivably be responsible
for the apparent affect of sediment concentration on partitioning. Among those
of possible importance are isotherm linearity, reaction kinetics, solution
composition, and the uniformity of solid phase binding site energies. Inves-
tigations were conducted to ascertain the influence of each of these processes
on the relationship between sediment concentration and partitioning.
Non-linear adsorption isotherms represent one possible explanation for
the apparent sediment concentration effect. However, the available experi-
mental evidence does not appear to support this hypothesis. As already in-
dicated, the isotherms for both the Saginaw Bay sediment and montmorillonite
displayed a linear character over the entire aqueous HCB concentration range
investigated. In addition, the adsorption isotherms constructed for 1100
mg/£ suspensions from a variety of different Saginaw Bay sediment samples
(Section VI) also demonstrated a linear relationship between r and c over
a a
a range of 1 ng/Jl - 100 ng/Jl in aqueous HCB concentration. Similarly other
studies (Lee et al., 1979; Wildish et al., 1980) on PCB adsorption to a
variety of sediments over a wide range of aqueous PCB concentrations sug-
gest linear isotherm behavior.
It is possible that the observed effects may be the result of variations
in solution chemical composition. Changes in suspended solids concentrations
may influence factors such as solution pH and ionic strength. However, as
shown in Section IV ionic strength effects are small and pH has an effect
only in the range, pH = 5 to 7.
In order to completely eliminate the effect of pH variations, isotherms
where constructed using a 2mM NaHCO- aqueous phase for montmorillonite concen-
trations of m = 55 and 1100 ppm. The large difference in partition coefficient,
as seen in fig. VII-4, cannot be attributed to pH variations since it remained
relatively constant (pH = 8.0 - 8.4) and above the inflection point found for
montmorillonite (fig. V-2),
90
-------
Effect of Adsorbent Concentration - Montmorillonite
500
oo
t>o
c
o
C
-------
Effect of Adsorbent Concentration - Montmorillonite
t>o
t>o
C
O
•a
c
o
•a
(D
500
400 _
300
200 -
100 -
50
Aqueous Concentration, c (ng/i)
Si
Fig. VII-4. Adsorption Isotherms for m = 55 and 1100 mg/Jl Montmorillonite
Aqueous phase = 2mM NaHCO-
92
-------
C. Variation in Binding Energy of Adsorption Sites
One difficulty in evaluating sediment concentration behavior, results
from the manner in which experimental sorption data are gathered. Studies
are typically carried out, either by varying the aqueous organic chemical
concentrations at constant sediment mass or by varying sediment mass at con-
stant total initial chemical concentration. It is probable that organic
molecules are capable of adsorbing onto solid phase sites of varying energy.
Under these conditions, variations in adsorption may simply reflect changes
in the type of solid phase sites occupied by the organic molecules rather
than effects due solely to the sediment concentration. It has been proposed
by a number of workers (see review by Hamaker and Thompson (1972) and the
references contained therein) that sediment surfaces may present a variety
of adsorption sites of differing binding energies to dissolved organic mole-
cules. Previous experimentation suggests that HCB moleclues may also demon-
trate similar behavior. The nature and fraction of such solid phase binding
sites occupied by a dissolved organic molecule such as HCB may depend on the
compounds' equilibrium aqueous concentration (c ). However, at a constant
a
initial aqueous concentration (c.), c may vary with sediment concentration,
i 3
as binding sites of differing energy are occupied. Hence, the apparent sedi-
ment concentration effect observed for HCB could result from variations in
binding site occupation.
A series of studies were conducted in an effort to evaluate this possibility.
In these experiments sediment concentrations were varied while maintaining ap-
proximately constant equilibrium aqueous HCB concentrations, c . Under these
a.
conditions all HCB adsorption should have been to surface sites of equivalent
energy. The results of experiments conducted on the Saginaw Bay sediment are
presented in figure VII-5. Under approximately constant equilibrium HCB aqueous
concentrations, (c ^ constant) values of r for adsorbed HCB decreased by
a, 3
approximately a factor of four as sediment concentrations were increased from
10 - 1000 mg/Jl. The resulting variation in partition coefficient is also
shown.
In contrast to the Saginaw Bay data, the results of similar experiments
utilizing montmorillonite (figure VII-6) indicated more marked changes in
r as sediment concentrations were varied. In adsorption studies conducted
93
-------
10"
10
10'
10
10
10
Effect of Adsorbent Concentration on Adsorption
Saginaw Bay C/50, Distilled Water
IT
a
a/kg)
(ng/g)
8
O
a D
(ng/fc)
O
O
go g
D
O
O
D
§
D
D
i i M inn i i I M MM i I i i i mi i i i i 1111
10
10 10 10-
Adsorbent Concentration, m (mg/£)
10
Fig. VII-5. Variation in Adsorption partition coefficient, TT , and Sediment Bound
HCB, r&, versus adsorbent concentration, m, at constant equilibrium
aqueous concentration, c .
a
94
-------
105
io4
10
102
101
10°
Effect of Adsorbent Concentration on Adsorption'
Montmorillonite, Distilled Water
IT A
rt / ^\
(I/kg)
A
A
ra
(ng/g)
ca o
A ..-
9 a
a a
0
A
D
§ § O ° ° ° ° §
(ng/A)
i i i mm i i i i in
10° 101 10' ID" 10^
Adsorbent Concentration, m (mg/A)
Fig. VII-6. Variation in Adsorption partition coefficient, TT , and Sediment
Bound HCB, r , versus adsorbent concentration, m, at constant
equilibrium aqueous concentration, c .
3
95
-------
105
io4
10
io2
101
10°
Effect of Adsorbent Concentration on Adsorption
Montmorillonite, Supernatant
r
a
(ng/g) A
(ng/fc) 8
0 o
A
10° IO1 IO2 IO3 IO4
Adsorbent Concentration, m (mg/Jl)
Fig. VII-7. Variation in Adsorption partition coefficient, IT , and Sediment
Bound HCB, r versus adsorbent concentration, m, at constant
equilibrium aqueous concentration, c .
96
-------
while maintaining essentially constant equilibrium aqueous HCB levels (c ^
3.
constant), r decreased from ^500 ng/g at a 10 mg/£ montmorillonite concen-
3.
tration to ^14 ng/g at 5000 mg/Jl. These data indicate that a two order of
magnitude increase in sediment concentration resulted in over an order of
magnitude decrease in the partition coefficient as shown.
In a related experiment designed to minimize the potential effects of
solution composition on partitioning, the supernatant solution resulting from
the centrifugation of a 1000 mg/Jl montmorillonite suspension was used in place
of distilled water. Use of this solution should have minimized solution com-
position changes as well as any solid surface area alterations resulting from
clay solubilization at low sediment concentrations. This supernatant stabilized
suspension pH levels within a relatively narrow range (pH = 6.7±0.3). However,
as indicated in figure VII-7, the use of this supernatant did not appear to sig-
nificantly reduce the magnitude of the effect of sediment concentration on par-
titioning. Adsorption results indicated an order of magnitude decrease in IT
Q.
over a 10 - 1000 mg/fc sediment concentration range. A similar experiment using
potassium phosphate buffer (2 • 10 M, pH = 7.25) gave similar results as
shown in fig. VII-8.
In order to consider the possible effects of kinetic factors on adsorption,
an evaluation was made of the influence of equilibration time on the relation-
ship between sediment concentration and partitioning. If sediment concentrations
affected the rate of adsorption, then increasing the equilibration time to longer
time periods should have resulted in significant increases in HCB adsorption.
Preliminary kinetic experiments indicated possible small increases in HCB ad-
sorption during time increases of up to 24 hours and no significant changes
for longer time periods (Section IV). However, as indicated in figure VII-9,
increasing the equilibration time to 24 hours appeared to have little effect
on the variation in TT with sediment concentration. For montmorillonite con-
a
centrations ranging from 20 mg/£ to 1000 mg/I values of ir decreased from
3.
^30,000 £/kg to <2000 £/kg. The magnitude and direction of this change was
quite similar to that observed for a 3 hour equilibration period as shown.
While these results do not entirely rule out kinetic effects, it does not
appear that such factors are responsible for the observed sediment concen-
tration behavior.
97
-------
10-
10
10-
10
10
10
Effect of Adsorbent Concentration on Adsorption
Montmorillonite, KH PO, Buffer
a/kg)
a
(ng/g)
(ng/fc)
I I I Mill I
o
D
D
A A
10
10
10"
10
Adsorbent Concentration, m (mg/£)
Fig. VII-8. Variation in Adsorption partition coefficient, TT , and Sediment
Bound HCB, r versus adsorbent concentration, m,aat constant
equilibrium aqueous concentration, c .
3
98
-------
10
10
10-
10
10
10
Effect of Adsorbent concentration on Adsorption
Montmorillonite, Distilled Water
71
a
(A/kg)
a
(ng/g)
(ng/i)
I I t I I Illl
I I I I I I lit
O
O
ii i i 11 n (
D t =24 hr.
3
t = 3 h
a
( I I I I I II
10V
10 10* .
Adsorbent Concentration, m (mg/£)
10
Fig. VII-9. Variation in Adsorption partition coefficient- 7T , and sediment
bound HCB, r , versus adsorbent concentration, m, at constant
equilibrium aqueous concentration, c . Effect of increased
adsorption time7 t = 24 hr. versus 1=3 hr. (dashed line
from fig. VII-6). a a
99
-------
The preceding experimental results appear to suggest that the effect of
sediment concentration on HCB is not readily explained by kinetic factors,
solution ionic strength or variations in the binding sites utilized during
adsorption. While it appears that solution composition changes can affect
partioning, the evidence does not seem to indicate that those changes which
were investigated (pH, ionic strength, etc.) can account for the magnitude
of the observed sediment concentration effect.
It has been suggested (O'Connor and Connolly, 1980) that an empirical
relationship exists between partition coefficient and sediment concentration
of the form.
IT = amb (VII-1)
a
Figure VII-10 presents the HCB data analyzed in this way. Table VII-1 gives
the regression coefficients and their standard errors. The exponent for
Saginaw Bay sediment is ^ - 0.36 to -0.40 whereas montmorillonite has an
exponent of -0.52 to -0.67 indicating the stronger sediment mass dependency.
The partition coefficients at m = 1 mg/£. (ir = a) range from a = 90 - 100
3
H/g for Saginaw Bay and 110-290 H/g for montmorillonite. Thus at low concen-
trations of sediment, the extrapolated partition coefficients are quite large.
It is interesting to note that the available data consistently indicates that
the sediment concentration effect is larger for montmorillonite than for the
Saginaw Bay sediment. The results also indicate that at the higher sediment
concentrations (>_ 1000 ppm) the lake sediment was significantly more effective
in adsorbing HCB than montmorillonite.
D. Discussion
A variety of studies (including Haque and Schmedding, 1976; Steen et al.,
1978; Karickhoff et al., 1979) have suggested that the magnitude of the parti-
tioning of organic molecules to natural sediments is related to the sediment
organic content. In studies on PCB distributions in sediments (Hiraizumi, 1978)
it has also been suggested that sediment surface areas may play a significant
role in partitioning. The results of the experimental data and analysis pre-
sented in Section VI, on a series of Saginaw Bay sediments and montmorillonite
clay, indicated that both factors were highly correlated with HCB partition
coefficient values and appear to be important to the HCB adsorption process.
This would imply that any variables which affect either of these
100
-------
10
10
Saginaw Bay Station #50
Distilled Water
10 . i
10
..i
100
1000
10'
Saginaw Bay Station //50
Supernatant
10
1C
*fr
1 f 111 | j a r I • 1 tl t _| • « a i tut
fe
TuouJ
Adsorbent Concentration, m (mg/£)
10
Montmorillonite
Distilled Water
Montmorillonite
Supernatant
100
1000
100
1000
10'
10
10'
...1
Montmorillonite
Distilled Water
10 100 1000*
Adsorbent Concentration, m (mg/£)
10
Montmorillonite
Phosphate Buffer
10 UK)
Adsorbent Concentration, m (m
Fig. VII-10 Log-log analysis of IT versus tn. Straight line slopes and
cx
intercepts are given in Table VII-1.
101
-------
• §
TABLE VII-1. Partitioning Coefficient - Adsorbent Mass Regression
o
K)
Adsorbent
Saginaw Bay
//50
M
Montmorillonite
a
it
tr
Aqueous
Phase
Distilled
Water
Supernatant
Distilled
Water
if
Supernatant
2 x 10~4M KH2P04
pH = 7.25
Adsorption
time
(hr)
2.0
2.0
2.0
24.0
2.0
2.0
a
101 A
(90.6, 113)
89.5
(48.6, 165)
162
(136, 192)
113
(101, 126)
182
(131, 251)
293
(217, 394)
b
-0.358 A
(-0.336, -0.381)
-0.408
(-0.28, -0.536)
-0.585
(-0.555, -0.615)
-0.518
(-0.494, -0.541)
-0.662
(-0.599, -0.784)
-0.668
(-0.608, -0,728)
Regression Equation TT = am
Mean + Standard Error
-------
factors might significantly affect partitioning.
The lack of organic matter in the montmorillonite clay suspensions would
rule out changes in this fraction as the cause of the observed sediment mass-
partition coefficient variations. It does, however, appear possible that un-
anticipated changes in surface area might occur within the sediment suspensions.
Specifically, it is suggested that linear increases in sediment concentration
(mass/unit volume) may not necessarily result in analogous linear increases in
surface area. Conceivably, the area of a sediment surface available for adsorp-
tion could be influenced by interactions occurring between suspended sediment
particles. For instance, electrostatic interactions arising from surface sites
of differing charge might result in a certain amount of interparticle association.
Interactions of this nature could result in a reduction in the number of solid
phase binding sites accessible for adsorption of a molecule such as HCB. In
the case of montmorillonite suspensions, interparticle associations have, in
fact, been reported (Laffer et al., 1969; Schweitzer and Jennings, 1971; Gil-
bert and Laudelout, 1971).
Controversy appears to exist over the precise geometrical arrangement of
such associations with a variety of structures having been proposed. Nor does
detailed information appear to be available on the influence of sediment concen-
tration or chemical composition on such interactions. Ascribing the HCB par-
titioning results of the present study to such interactions requires that in-
creasing montmorillonite and, to less an extent, Saginaw Bay sediment concen-
trations result in a decrease in the number of available binding sites on a per
unit mass basis. The relationship between HCB partitioning and solid phase
surface area would, however, depend upon the location of principal binding
sites. If HCB molecules preferable bond at clay particle edges then avail-
able clay edge surface area and not total surface area would be of importance
to partitioning.
Under this interpretation, at high sediment concentrations (> 1000 mg/£)
the Saginaw Bay sediment is a much more effective HCB adsorber probably as a
result of the dominance of interactions involving the sediment organic phase.
However, as sediment concentrations are decreased, TT increases more rapidly
3.
for montmorillonite than for the Saginaw Bay sediment. This increase is pre-
sumably due to a significant increase in the total or edge surface area to mass
103
-------
ratio for the clay. The Saginaw Bay sediment would not be expected to possess
the same surface charge characteristics as montmorillonite and hence particle
interactions are unlikely to be of the same magnitude. A more detailed analysis
of the relationship between the nature of the solid phase binding sites and the
effects of sediment concentration is presented in Part B of this report.
E. Implications
The potential implications of the relationship between partitioning and
sediment concentration to natural water PCB distributions may be illustrated
by a consideration of HCB adsorption ratios. The fraction of a given total
HCB concentration, CT , which is adsorbed on suspended particles, mr , may
1 £1 • ' cl
be calculated from the relationship:
(VII-2)
Values for f have been determined from previously discussed Saginaw Bay and
P
montmorillonite data (figures VII-5 and VII-6) and the results plotted against
sediment concentration (figure VII-11). For comparison, curves representing the
partitioning behavior expected from measurements made at high sediment concen-
trations (1000 rag/A and 10000 mg/Jl) in the absence of any concentration effect
(IT assumed constant and equal to 2000 £/kg for montmorillonite and 10,000 £/kg
3.
for Saginaw Bay sediment) have also been plotted. The results demonstrate the
relatively large differences in the.predicted fraction of HCB adsorbed onto
dilute montmorillonite suspensions (<10 mg/A) in the absence of a sediment con-
centration effect (f M).02) and the values calculated on the basis of the ob-
P
served experimental data (f ^0.35). It would appear that at suspended solids
concentrations typical of many quiescent fresh water bodies (1-50 mg/O, inor-
ganic clay materials may be capable of carrying a significant fraction of the
overall total aqueous PCB loading, possibly initially outcompeting more organic
rich sediment fractions. However, since HCB is more readily desorbed from
montmorillonite than from organic containing lake sediment, as shown in the next
section it is uncertain that clay particles would act as a significant PCB sink.
It is somewhat more difficult to evaluate the overall implications of the
partitioning results for PCB cycling through sediment transport. Processes
such as the shoreline erosion of red clays into Lake Superior (Bahnick et al.,
1979) may involve, first, sequential reductions in suspended clay concentrations
104
-------
Saginaw Bay Station #50
c
o
T-l
U
CJ
(8
M
u-i
4)
*J
ifl
,— I
3
u
>J
(fl
cu
I—t J iimt i • i i mil i
1.0-
Montmorillonite
0.1
TT = 2000 £/kg
a
JLU
10 10 10 10
Adsorbent Concentration, tn (mg/£)
10
Fig. VII-11. Comparison of particulate fraction computed using
constant TT to observed data
105
-------
through dilution and subsequent increases in solid phase concentrations as
material settles into lake bottom sediments. The preceding results suggest
that conceivably during such a. cycle aqueous dissolved PCB molecules might
first be adsorbed from solution only to be later partially desorbed in re-
sponse to increases in sediment concentration. Clearly, interactions between
sediment concentration and partitioning may suggest a rather more dynamic
cycling of PCB's between aqueous and solid phases than is generally accepted.
In summary, the results of these studies suggest that the partitioning
of HCB to both Saginaw Bay sediment and montmorillonite clay is affected by
the sediment concentration. Decreasing the sediment concentration from 1000
mg/H to 10 mg/£ resulted in a considerably larger increase in IT for montmor-
3
illonite than for the Saginaw Bay sediment. Experiments failed to demonstrate
that this effect was the result of non-linear isotherms, kinetics or changes
in solution chemistry. It is tentatively suggested that this effect may be
the result of direct interactions between solid phase particles which result
in changes in the amount of sediment surface area, available for HCB adsorp-
tion. The occurrence of such effects in natural systems could result in sig-
nificant variations in HCB sorption as sediment concentrations change during
erosional and depositional processes.
106
-------
SECTION VIII
REVERSIBILITY OF ADSORPTION AND DESORPTION
A. Introduction
A principle focus of this experimental investigation is the issue of rever-
sibility. Although some information from previous studies was available for the
PCB adsorption reaction on sediments, less information is available on the mag-
nitude of PCB desorption from sediments. As PCB usage declines, it is likely
that the extent of desorption may determine future changes in natural water con-
centrations. PCB desorption studies include measurements of Arochlor 1254 re-
lease from contaminated soils (Farquhar et al., 1979) and sediments (Halter and
Johnson, 1977). In addition, Freundlich isotherm parameters have been determined
for Arochlor 1254 partitioning to sand and silt (Wildish et al., 1980). There
appears to be relatively little information on the desorption of individual
highly chlorinated (Cl _>_ 6) PCB isomers from natural sediments. Studies (Furu-
kawa, 1978) have suggested that it is the more highly chlorinated PCB compounds
which are likely to be the most environmentally persistent. Thus it is these
species which may exert the greatest long term influence on natural water PCB
levels.
In addition, there is a need for information on the extent of PCB desorp-
tion at the « 1 ppb aqueous concentrations typically reported for natural
waters (Pavlov and Dexter, 1979). As pointed out by Hamaker and Thompson
(1970), such information is important to avoid the possibility of erroneous
estimates of the magnitude of partitioning resulting from the extrapolation of
high concentration data to more dilute solutions.
It is the purpose of this section to evaluate the extent of reversibility
of HCB sorption to natural sediment materials. As in the experiments discussed
in previous sections, studies have been conducted with a single hexachlorobi-
phenyl isomer at aqueous concentrations similar to PCB levels which have been
reported in natural waters.
107
-------
B. Isotherm Results
The partition coefficients for the fine fraction of the Saginaw Bay sedi-
ment samples discussed in Section VI all exhibited significant non-reversibility:
Adsorption partition coefficients were consistently lower (IT ^ 12,000 fc/kg) than
3.
the desorption partition coefficients (ir ^ 25,000 £/kg). The coarse fraction of
Station //69 also exhibited nonreversible behavior although the magnitude of both
coefficients was much lower (IT = 0.036 £/kg, TT = 0.052 fc/kg).
c* Q
A useful index of reversibility is the ratio of desorption to adsorption
partition coefficient: ^J^ , which approaches unity for complete reversibility
Q 3.
and increases as norireversibility increases. Table VIII-1 lists the isotherm
parameters, their coefficients of variation, and the reversibility index which
ranges from T /IT = 1.44 to 3.44. Since they are all statistically greater
u a
than unity (except Station //53) the evidence is that significant nonreversi-
bility exists for the Saginaw Bay sediment samples.
In addition to these sediment samples', inorganic clays were used as adsor-
bents for isotherm at various clay concentrations with various aqueous phases.
These isotherms are shown in figure VIII-1, for montmorillonite at adsorbent
concentrations of m = 50, 200, and 1000 mg/K, with distilled water as the aqueous
phase; in figure VIII-2 for montmorillonite (m = 55 and 1100 mg/£) and a 2mM
NaHCO. buffer as the aqueous phase, which corresponds to the alkalinity of
Saginaw.Bay water, and kaolinite (m = 1000 mg/J, in distilled water); and in
figure VIII-3 for Saginaw Bay Station //50 at sediment concentrations of m = 50,
220, and 1100 .mg/fc.
It is apparent that both the inorganic clays and the Saginaw Bay sediment
exhibit significant nonreversibility. The reversibility ratio ranges from
Tr./Tr ^2 for the lower sediment concentration (m ^ 50 mg/J!.) and IT /IT ^ 3 for
da da
the higher sediment concentration (m ^ 1000 mg/J,). Table VIII-3 presents the
partition coefficients and the reversibility factor for these isotherms.
The experimental design used to investigate the effect of sediment concen-
tration on adsorption partition coefficient (Section VII) can also be used to
investigate reversibility since a desorption followed the adsorption step.
The adsorption and desorption partition coefficients and the reversibility
index versus sediment concentration is shown in fig. VIII-4 for Saginaw Bay
108
-------
TABLE VIII-1
Station //
§
Isotherm Parameters - Saginaw Bay Sediments
Partition Coefficients
Adsorption Desorption
19
31
43
50
53
*
69
Saginaw R.
IT
a
14.
12.
10.
7.
11.
0.
9.
(A/8) \j
8
3
7
01
2
(0.
(0.
(0.
(0.
(0.
036(0.
63
(0.
10)
17)
21)
13)
04)
26)
08)
30.
30.
26.
20.
19.
0.
22.
(A/8)
1
9
1
2
8
052
4
(0.
(0.
(0.
(0.
(0.
(0.
(0.
17)
14)
40)
27)
21)
15)
23)
Reversibility Ratio
Va
2.03 (0.20)
2.51 (0.22)
2.45 (0.45)
2.88 (0.30)
1.44 (0.21)
2.33 (0.30)
3.44 (0.24)
Sediment concentration = 20,000 mg/fi.
§
Numbers in parentheses are coefficients of variation
-------
• fe »_11 ft * » J • ftJ AJ
n 10'
•k
cd
§
O
10
W 101
Desorption
10^
Adsorption
m = 200 rng/fc
10
a_ . a. .a A
_u_J
10
Aqueous Concentration, c , c (ng/£)
3- d
Fig. VIII-1. Adsorption and Desorption Isotherms - Montmorillonite
Distilled Water. Lines have unity slope
110
-------
10
10J
Montmorillonite
Desorptton
Adsorption
m = 50 rag/Si
mil
10
10
•o
14
PQ
u
•o
c
o
pq
•a
0)
c/j
10"
10
10
Montmorillonite
| Desorption
10'-
Adsor,p£lon
m = 1100 rag/A
10
10
10"
10
10-
Kaolinite
Adsorption
Aquequs Concentration, c c
fc
Fig. VIII-2. Adsorption and Desorption Isotherms - Montmorillonite, Aqueous
phase = 2mM NaHCO, and Kaolinite, Distilled Water.
Lines have unity slope.
Ill
-------
10"
10
Desorption
Adsorption
m = 50 mg/J,
t 1 « ^ «. til 1—I—I I t
nit
10
10
10
•** o
* 103
10
u
m
1
O
u 10
c
T3
(U
Adsorption
m = 220 mg/Jl
10J
10'
10
10-
10
10J
on
mg/A
Aqueous Concentration, c c
Fig. VIII-3. Adsorption and Desorption Isotherms - Saginaw Bay #50
Distilled Water. Lines have unity slope
112
-------
TABLE VIII-2
§
Isotherm Parameters - Effect of Sediment Concentration
Sediment Aqueous
Phase
Montmorillonite H~0
Montmorillonite H?0
Montmorillonite H»0
Montmorillonite Buffer
Montmorillonite Buffer
Kaolinite H~0
Saginaw Bay #50 H20
Saginaw Bay #50 H?0
Saginaw Bay #50 H^O
Sediment
Concentration
m (mg/fc)
50
200
1000
55
1100
1000
50
220
1100
Partition Coefficients
Adsorption Desorption
T (*/g) T U/g)
a d
10.
6.
2.
16.
2.
1.
17.
12.
7.
6
69
90
2
10
08
1
3
05
(0.
CO.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
40)
09)
20)
26)
19)
20)
27)
14)
13)
24.9
15.7
9.65
30.4
7.15
3.26
25.2
25.9
18.9
(0.
CO.
(0.
(0.
(0.
CO.
(0.
(0.
(0.
26)
21)
10)
21)
11)
05)
29)
21)
27)
Reversibility
Ratio
•n /IT
d a
•2
2
3
1
3
3
1
2
2
.35
.35
.33
.88
.40
.02
.47
.11
.68
(0.48)
(0.23)
(0.22)
(0.33)
(0.22)
(0.21)'
(0.40)
(0.25)
(0.30)
Adsorption time = 2 hours
§
Numbers in parentheses are coefficients of variation
Buffer is 2mM NaHCO,
-------
and fig. VIII-5 for montmorillonite. The two cases are for aqueous phases con-
sisting of distilled water and supernatant, as described in Section VII. The
gradual increase in separation between K, and ir , and the increase in TT/TT as
da da
mass increases indicates that the extent of nonreversibility is increasing as
sediment concentration increases. The exception is montmorillonite in super-
natant. An interpretation of these results in terms of exchangeable and non-
exchangeable components is presented in Part B of this report. However, it is
also possible that the nonreversibility is the result of an experimental arti-
fact. Experiments designed to address this issue are described below.
C. Irreversibility
A review of the literature on soil-organic interactions reveals that non-
singular isotherm behavior is not unique to hexachlorobiptienyl. Studies on
picloram (Farmer and Aochi, 1974), 2,4,5,-T (van Genuchten et al., 1977),
Diuron (Peck et al., 1980) and DDT (Pierce et al., 1974) among others, all
suggest distinct differences between adsorption and desorption isotherms. A
i
variety of factors have been postulated to account for this behavior. Rao
and Davidson (1980) in a review of literature on the subject indicate that non-
singularity may result from lack of attainment of equilibrium during desorp-
tion, chemical or microbial transformations, or experimental artifact. Experi-
ments were conducted to test the potential effects of these factors on the HCB
isotherms of the present studies.
Evidence suggests that microbial transformations are not responsible for
causing non-singular HCB isotherms. In experiments conducted using activated
14
sludge cultures, no evidence of HCB degradation (as measured by C-CO? evolu-
tion) was obtained during a two moath test period. Since it is likely that
such cultures contain far greater densities of microbial organisms than would
be expected in either the natural sediment or montmorillonite suspensions,
they probably represent optimal degradation conditions. Other studies (Tucker
et al., 1975; Furukawa et al., 1978) have confirmed these findings and indi-
cate that the rate of microbial degradation decreases as the degree of PCB
chlorination increases. Thus if microbial degradation of HCB occurs at all,
it requires time periods much longer than the reaction times of the present
study.
114
-------
Montmorillonite
~ io5
60
.M
oi
«=
c
ft! /
u
o 10
•H
U-J
a)
o
o
•H
4.J
'rl 3
£ 10
rt
(^
t
5.
4
3
t=
"O
«= 2
1
Q
v .L O L- ^ J« JU ^^ VA rV C* ^ ^^ ^ ^
.- 'S 10
" "^ "^
n ""--
U ^ o^
n ^
Q * * D na U/kg)
B o + -^ io4
r D T 2
• Q UJ
* ,!• 1>
" * O
e + "
° g
- -rl
O.
3
. .....1 . . . ...iJ j_i.i mill 1 t tlfcuJ ^ 10
3 10 100 1000 10000 nrt :
O-i
Distilled Water
t
4
"*" -K*
"*" •+• J* ^
^* •*. "^" ^^
„ •*• T * ' 2
+ •+• •**
-H
- i
-*'-«*"l 1 til iiii( 1 — ' * •""! - • » *nij 0
^ f~\ T /\ /^ ^ /^ ^^ ^^ ^ r^ ^ *^ ^ .
tjtapc.i. iiat-OLiu
^•B
«
»
•
" d
a D wa (a/kg)
**"
a +
T* 4*
: ° a 4.
• +
D _
o
• • I i k Al i •tftltAll t 1 ••*•••• * •
J 10 100 1000 3000
Supernatant
•
^,
"* 4- "*" 4- "*"
•
Adsorbent Concentration, m (mg/H)
10 100 1000 3000
Adsorbent Concentration, m (mg/J.)
Fig. VIII-4. Effect of Adsorbent Concentration on Degree of Reversibility
Adsorption, n and Desorption, IT Partition Coefficients and •
their ratio d
-------
Saginaw Bay #50
" 10 -
C '
01
•^ 4
2 10
U-l
O
O
o
o
% 10"
4
3
2
1
0
Distilled Water
_i.
+
*t
.+ 1
a
a
8
. + IT. (A/kg)
n_
~—r ......i . .
10 100
Distilled Water
1000 3000
I
..t
3 10 100 1000 3000
Adsorbent Concentration, m (mg/Z)
•* 10
-o
w<
t^
4-1
c
01
•H
O
-H 4
^ 10
01
o
CJ
c
o
•H
•H
« 3
P- 10
J» w
*
5
4
cd o
H. j
t=
2
1
0
kJ llpwl. HO UdLl i.
V
: A
•i-
»
n •+• ^ ^. .
• "T" "*
O
r to
: a a
•
•
. + TT a/kg)
a irda/kg)
.TTiTT — • — r~, ,....! . . ......i . .
} 10 100 1000 3000
Supernatant
•*-
•
•*••*•
•h
*
n • ••••' • ' • • "••' * i • • ••'•* ' *
10 100 1000 3000
Adsorbent Concentration, m Ong/£,)
Fig. VIII-5. Effect of Adsorbent Concentration on Degree of Reversibility
Adsorption, TT , and Desorption. TTH, Partition Coefficients and
their ratio .
-------
D. Dilution Experiment
It has been suggested (Rao and Davidson, 1980) that for some soil-pesti-
cide systems, non-singular isotherms may be an experimental artifact caused by
centrifugation. The possibility exists that centrifuging may alter the manner
in which an organic molecule is bonded to the solid phase resulting in a dis-
placement of the desorption isotherm. To test this hypothesis, desorption
isotherms were constructed by varying the sediment and aqueous concentrations
through dilution. Following HCB equilibrium adsorption to 1100 mg/£ sediment
suspensions, solid and liquid phase concentrations were diluted by replacing
varying volumes of the suspension with equal volumes of distilled water.
Samples were then re-equilibrated, subsequently centrifuged to determine the
amount of HCB desorbed from the solid phase, and the results used to construct
desorption isotherm.
Desorption isotherms based on this dilution technique (Figure VIII-6)
indicate that HCB adsorption to Saginaw Bay //50 and montmorillonite is not
readily reversible. For both sediments the results suggest that decreases
in aqueous concentration, c, do not result in significant reductions in ad-
sorbed particulate concentration, r, which is not what would be expected if
the adsorption process was readily reversible. The horizontal isotherms ob-
tained imply even less reversibility than is indicated from isotherms con-
structed in the usual manner. Hence it does not appear that centrifugation
is responsible for the observed non-singular isotherms. This conclusion is
supported by observations (Rao et al., 1978) suggesting that centrifugation
effects appear to be more pronounced for ionic water soluble molecules than
for neutral non-ionic species.
The interpretation of the dilution experiment ignores the effect of
varying sediment concentration on desorption. This is inherent in the dilution
method which relies on removing a portion of the total suspension and replacing
it with particle free aqueous phase. In fact, the analysis of dilution experi-
ments is fairly complicated. In Part B, the dilution experiments are analyzed
in terms of the exchangeable and nonexchangeable model of adsorption and desorp-
tion. This clarifies the mechanism which produces the almost horizontal dilution
isotherms.
117
-------
200
150
100
60
60
C
u
1
o
£ 50
•H
•o
01
CO
4
ADSORPTION (O)
DILUTION (+)
4 °
4
4
MONTMORILLONITE
+
4-
SAGINAW BAY //50
4 6 8 10 12 14
Aqueous Concentration,
16 18
20 22 24
Fig. VIII-6 Effect of Dilution on HCB Desorption
118
-------
E. Kinetic Effects
Previous studies (Steen ct al. , 1978) have suggested that PCB adsorption
to sediments is a rapid process reaching equilibrium in a. matter of minutes.
In the present study, experiments suggest that while adsorption time exerts an
influence on reversibility, it does not appear to account for the non-singular
isotherm behavior. As discussed in Section IV (Kinetics), a series of isotherms
were constructed for HCB adsorption to 1100 ppm Saginaw Bay sediment (//50) sus-
pensions for time periods of 3 hrs, 1 day and 5 days. The results suggested
that small increases in adsorption may occur during the first 24 hours with
little evidence for significant changes at longer equilibration periods.
The effect of desorption time on reversibility was also tested experimen-
tally. For a fixed adsorption time (3 hr) a series of desorption isotherms
for varying desorption times (2 hr, 3 day, 6 day) are shown in fig. IV-11 of
Section IV. Although some differences occurred the trend is not consistent:
the 2 hr desorption isotherm is bracketed by the 3 day and 6 day isotherms.
Further, the differences between the three desorption isotherms are much less
than the difference between the adsorption isotherm and any of the desorption
isotherms. Hence although there appears to be some effect of time of desorp-
tion it is not sufficient to eliminate non-reversible behavior. Overall, it
appears that small increases in HCB adsorption may occur between 3 and 24 hours
while no consistent evidence of changes in desorption with time were observed.
What was not discussed in Section IV is the effect of adsorption time on
the desorption partition coefficient. As shown in fig. VIII-7, for adsorption
times of t =2, 48 and 240 hrs, the adsorption partition coefficient increased
O
slightly (ir = 17000 to 18000 £/kg) but the desorption coefficient increased
3,
markedly (n = 25200 to 61000 £/kg) after 48 hrs of adsorption and little there-
after. The reversibility ratio increased from TT /IT = 1.5 to 3.4 (Table VIII-3).
This result suggests that whatever the binding reaction is that increases irre-
versibility, for this sediment, concentration at least, it requires ^ 2 days for
it to reach equilibrium. '
This result is contradicted by the results of a sediment concentration
experiment for montmorillonite for which the adsorption time is t =24 hr
cl
(.fig- VIII-8). The results are not substantially different from the equiv-
alent shorter term adsorption time experiment (fig. VIII-4). The aqueous
119
-------
TABLE VIII-3
§
Isotherm Parameters - Effect of Adsorption Time
*
Sediment
Saginaw
Station
Station
Station
Bay
#50
//50
#50
Adsorption
Time
tfl (hr)
2.0
48.0
240.0
Partition Coefficients Re
Adsorption Desorption
IT
a
17.
18.
16.
U/g)
1 (0.27)
2
3
(0.24)
(0.27)
"d U/g>
25.2 (0.
61.3
54.0
(0.
•CO.
29)
25)
42)
1.
3.
3.
versibilit
Ratio
47
37
31
(0.40)
(0.35)
(0.50)
ro ^
° Sediment concentration = 55 mg/fc; Aqueous phase is H,,0
§
Numbers in parentheses are coefficients of variation
-------
oo
oo
e
a
33
•a
3
O
M
C
8
•H
•O
0)
C/3
C Desorption
10-
10'
Aqueous Concentration, c ,c (ng/£)
Fig- VIII-7. Effect of Adsorption Ti.e on Reversibility
m = 55 mg/£ Saginaw Bay #50
121
-------
'artition Coefficient, IT, (il/kg
r-> t- H-
000
'•> . -I* 1
0 + ir.U/Rg)
* + m
U TT (i/kg)
Da
I n -h •
a
' i « tut 1 1 — 1 » 1 lilt 1 1 — t i i ml i 1
1 « 1 » «
.111
1 — I — 1. 1 II
I 111.
3.0 10.0
100.0
1000.0 3000.0
Adsorbent Concentration, m (mg/Jl)
Fig. VlII-8. Effect of Adsorption on Reversibility Adsorption
TT , and Desorption, TT , Partition Coefficients versus
o O . ^
Adsorbent mass, t = 24 hr. Montmorillonite.
Supernatant
122
-------
phase is supernatant for both experiments.
These conflicting results indicate that further experimental investigations
are required to elucidate the details of the mechanism by which the irreversi-
bility occurs and its relationship to kinetic effects.
F. Consecutive Desorption
In an attempt to more clearly define the extent .of reversibility of HCB
adsorption, a series of consecutive desorption studies were performed. In
these experiments, HCB was initially adsorbed onto sediment samples (Saginaw
Bay #50 and montmorillonite) and subsequently subjected to a series of con-
secutive desorption cycles. After 1 hour equilibration periods, the samples
were centrifuged and the aqueous phase replaced with distilled water. Samples
were analyzed for aqueous and sediment HCB concentrations. Figure VIII-9 dis-
plays the results of initial experiments for sediment concentrations of m = 80
mg/fc and 220 mg/fc. The consecutive desorption isotherms are essentially linear
with the exception of the 80 mg/£ montmorillonite isotherm.
In order to evaluate the effect of longer desorption times, a second experi-
ment was performed with adsorption and desorption times of 24 hrs. The data
Cfig. VHI-lOa), although more scattered, indicates a linear isotherm although
it is difficult to judge the shape of the isotherm at low aqueous concentrations.
The effect of changing the aqueous phase (2mM NaHCO ) for montmorillonite is shown
in fig. VHI-lOb. As with the Saginaw Bay sediment at m = 1100 mg/A the small
aqueous concentrations that result at each desorption makes.it difficult to
judge the exact shape of the consecutive desorption isotherm. Table VIII-4
presents the data for these experiments.
In order to further define the consecutive desorption isotherm, the number
of desorption cycles was increased to ten. Figures VHI-lla and lib present the
variation in sediment bound HCB and aqueous phase HCB concentrations with de-
sorption cycle, for 15 mH, 1100 ppm Saginaw Bay #50 suspensions. To maintain
a constant sediment concentration, solution volumes were appropriately adjusted
(0.5 m£ per cycle) following the removal of each total suspension sample to
determine c . At both initial HCB concentrations, the results suggest a sharp
initial decrease in aqueous HCB levels (desorption cycles 1 and 2) followed by
almost constant levels (2.8 ng/X, and 5.5 ng/Z) during the remaining cycles (fig.
123
-------
200
00
oo
c
§ 100
T3
C
3
O
(Q
G
a
•H
T3
0)
CO
Consecutive Desorption Isotherms
S.iginaw Bay
m =220 mg/£
Montmorillonite
m =220 rag/Si
10
15
Aqueous Concentration (ng/£)
300
Saginaw Bay */50
m = 80 mg/SL
Montraorillonite
m = 80 mg/H
D Adsorption
i Desorption
Aqueous Concentration (ng/£)
Fig. VIII-9. Consecutive Desorption Isotherms Saginaw
Bay and Montmorillonite
124
-------
Consecutive ncr.orpl Ion Tsothurras
CO
oo
c
«
o
3:
T3
d
3
O
M
d
-------
Cycle
0
1
2
3
4
1
2
3
4
t = tj = 24 hr.
a d
0
1
2
3
4
0
1
2
3
4
220
209
199
189
179
24 hr.
1100
1045
993
943
896
TABLE VII1-4
Consecutive Desorption Data
Montmorillonite
Sediment
Cone.
m (mg/S,)
80
76
72
68
64
220
209
199
189
Aqueous
Cone.
c (ng/*)
17.3
5.5
3.8
2.4
1.6
12.3
7.4
5.0
3.4
Particulate
Cone.
r (ng/g)
191
122
113
89.4
77.1
153
106
90
66
17.5
5.0
2.5
6.4
3.3
134
84
65
53
50
Saginaw Bay #50
Aqueous
Cone.
c (ng/£)
13.6
6.3
3.9
2.9
1.9
6.2
5.1
3.9
3.5
14.4
5.4
5.9
6.2
4.3
7.6
1.65
1.4
1.3
1.1
Particulate
Cone.
r (ng/g)
287
209
195
162
157
207
177
154
140
178
141
114
86
58
59
55
48
47.6
48
Aqueous Phase = 2mM NaHCO,
0
1
2
3
4
5
1100
1063
1028
994
961
928
26
13
5.3
4.4
3.9
2.8
66
51
55
50
40
39
-------
IU
PQ
O
1 io2
O *-N
W 00
AJ 00
C' B
T
w , .,1
10
io2
c
0
1-1
1 I
i-l
4J
S i
S io1
C '"*•
O oi
CJ "^
00
?•£
f* ^"^
o
4) U
9
°" n
< 10U
200 ,
PQ
U
-a 100 .
C
o
00
B 00
a d
S ^
T3 M
,« n
: (a) Adsorption ^^ . /
- 1 Desorption (O ; D )
1
I
;^,oo--oo O.OOH>....
— 1
1
*
i 1 1 1 1 I 1 1 ' | 1 1
0123456 789 10
Cycle
-•
(b) Adsorption (^ • •)
' Desorption ( O - D)
» 1
4
"" Xrf^
: !o0<>00 O0*0
o°ooanO°a
a
1 1 1 1 1 1 1 1 1 1 1
0123456789 10
Cycle
(c) Isotherm
o-^>- — —7^
; €<> x
/^> x
' >r >X^
/ /
fff^l jr
s^
.S
s'
r \ 1 * *
' 0 5 10 15 20
Aqueous concentration, c, (ng/fc)
Fig. VIII-11. Consecutive Desorption, Saginaw Bay #50
m = 1100 mg/£, Distilled Water (a) Sediment
Bound HCB, r, and (b) aqueous concentration,
c versus desorption cycle, (c) Isotherm
127
-------
00
TABLE VIII-5
Consecutive Desorption
Saginaw Bay #50
Cycle
0
1
2
3
4
5
6
7
8
9
10
CT
(ng/a)
81.00
74.28
70.36
66.66
77.52
62.88
61.55
58.80
59.15
54.63
51.20
c
(ng/a)
7.96
4.15
2.87
3.22
2.56
2.58
3.07
2.13
2.90
3.10
2.50
r
. (ng/g)
66.40
63.73
61.34
57.60
68.02
54.81
53.17
51.51
51.09
46.82
44.27
m = 1100 mg/«.
f»
CT
(ng/a)
190.25
174.37
164.92
167.68
153.08
149.43
128.12
139.32
134.29
121.60,
119.27
c .
(ng/A)
16.15
8.85
6.20
6.32
5.10
5.01
7.65
4.54
6.21
4.89
5.37
r
(ng/g)
158.22
150.41
144.29
146.69
134.50
131.29
109.08
122.50
. 116.32
106.06
103.90
-------
VHI-llb). Table VIII-5 presents the data. By comparison, values of
sediment bound HCB concentrations appear to decrease exponentially as the
number of desorption cycles increases (figure VHI-lla) . An extrapolation
of the sediment concentration results appears to suggest that s sufficiently
large number of washing cycles may result in desorption of all of the adsorbed
HCB. However, the curvilenear variation in aqueous HCB concentration is not
what would be expected if a single reversible isotherm described HCB sorption
behavior .
A single reversible isotherm would result in parallel curves for the par-
ticulate and aqueous data on a logarithmic scale, as implied by the linear par-
tition equation r = ire. Figure VIII-llc presents the isotherm for these data.
The first two desorption cycles produce essentially linear and distinct consec-
utive desorption isotherms. The remaining data is quite scattered due to the
experimental variability of the low aqueous concentrations.
Conceivably, the variations in sediment bound HCB concentration, r, with
desorption cycle, could be an experimental artifact caused by reductions in
sediment particle sizes resulting from abrasion during shaking. The formation
of extremely fine particles which resist contrifuging has been previously ob-
served for other natural sediments (Karickhoff and Brown, 1979). The creation
of such particles during the desorption cycle could result in losses of sediment
and could account for the observed reductions in r. However, it seems unlikely
that shaking should consistently lead to the formation of equivalent amounts of
fine particles as would be required to produce the observed data.
In a further effort to determine whether all of the HCB may be eventually
desorbed, studies were conducted on 220 ppm sediment suspensions. It can be
shown that the ratio of the dissolved phase HCB concentration, c , to the total
Si
HCB concentration In suspension, c , may be expressed as:
la
where m is the solid phase concentration. Therefore, decreasing the experi-
mental value of m from 1100 ppm to 220 ppm should result in a significantly
greater fraction of the total HCB concentration being removed during each
desorption cycle.
129
-------
The results of these 220 ppm experiments appear to confirm the decreases
in sediment HCB concentration observed for the 1100 ppm suspensions. In these
220 ppm experiments, solution volumes were kept constant and as a result sample
analysis resulted in small changes in the suspension sediment concentrations.
The results are shown in fig. VIII-12 for montmorillonite and Saginaw Bay
sediment (#50). The data are presented in Table VIII-6. A more rapid de-
crease in particulate HCB concentration during each desorption cycle is
apparent, in agreement with eq. (VII1-1) which predicts a larger HCB fraction
associated with the dissolved phase at m = 220 ppm. However the particulate
and aqueous phase concentrations are again not parallel: whereas the particu-
late concentrations decrease exponentially the aqueous concentrations decrease
rapidly at first and then more slowly. The isotherm plot (fig. VIII-12c) sug-
gests a two phase process: an initial linear consecutive isotherm, followed by
a second linear isotherm which appears to intersect the origin, implying that
eventually it is possible to eventually desorb all the HCB.
A detailed quantitative evaluation of the adsorption and initial consecu-
tive desorption isotherms in terms of two adsorbed components: an exchangeable
and initially non-exchangeable component is presented in Part B of this report.
The data presented in figs. VIII-11 and 12 suggest that low aqueous concentra-
tions must be reached in order that the "non-exchangeable" component eventually
desorbs. It is also apparent that the mass of solids, m, influences the aque-
ous concentration at which this desorption commences.
The observed consecutive desorption data might be explained if HCB mole-
cules were capable of forming bonds of differing strength with sediment sur-
faces. The consecutive desorption data for Saginaw Bay sediment (//50) indi-
cates that a majority of the adsorbed HCB is more strongly bound than would be
predicted by a reversible adsorption isotherm. A smaller amount of HCB appears
to be relatively exchangeable. This behavior could result from HCB adsorption
to both inorganic and organic components of the natural sediment. Under this
hypothesis, the desorption behavior displayed by montmorillonite could imply
adsorption to differing inorganic sites on the clay particles, possibly par-
ticle edges versus particle faces. Alternately, it is possible that HCB mole-
cules may adsorb in geometrically different arrangements to relatively uniform
130
-------
10'
(n) Adsorption ( U ;
PQ
o
•a
c
3
O X-N
PQ 00
u GO
c a
•H M
•O
u
t/5
10
10
10
Df.sorptJon
A.
' ' 1 L.
_J L l_
01234567
Cycle
(b) Adsorption /g . ^
A ' >
89 10
o
-H
14
C ,
ttl X
o 10
d <—
o <*t
to c
3 ^
o
at o
3
< 10°
:- Desorption ( U -, t± )
: ift
1 ^^
0 A A
1 ° A
- ' a a A A A
J a 0 a ^ A
a n
3 60
PQ OO
G
4J x_»
g U
a
•H
•O
01
CO
600
400 .
200
°1234 567
Cycle
(c) Isotherm
89 10
Aqueous Concentration, c, (ng/£)
Saginaw Bay J?50 H D
Montmorillonite A A
Fig. VIII-12. jConsecutive Desorption. Saginaw Bay //50 and
"Montmorillonite. m = 200 mg/£. Distilled Water
(a) Sediment Bound HCB, r, and (b) aqueous
concentration, c, versus desorption cycle.
(c) Isotherm
131
-------
surfaces. The formation of face to face versus edge to face bonds could re-
sult in differing degrees of desorption. Such behavior has been suggested to
account for the adsorption of certain pesticides to sediments (Huang, 1970).
G. Conclusion
It appears that while HCB adsorption to sediments may be.ultimately
ji
reversible, the process does not appear to be defined by a single reversible
isotherm. Partition coefficient values for desorption isotherms are substan-
tially greater than those obtained for adsorption. Consecutive desorption
data suggests the possibility of the formation of HCB-sediment bonds of dif-
fering strengths. Overall, the results indicate that the use of adsorption
isotherms alone, will result in overestimates of the amount of HCB released
from sediments to natural waters.
132
-------
Cycle
0
1
2
3
4
5
6
7
8
9
10
TABLE VIII-6
Consecutive Desorptlon
m = 220 mg/£
Montmorillonlte
CT
(ng/A)
176.36
95.72
66.83*
45.36
35.96*
30.06*
24.95*
21.52
*
17.81
*
13.27
17.48
c
(ng/£)
81.04
25.20
12.44
7.47
5.67
4.82
3.66
2.71
3.66
2.31
2.23
r
(ng/g)
433.10
335.28
272.62
190.24
159.06
131.99
111.90
99.21
73.75
5.9.32
82. '08
Saginaw
CT
(ng/£)
195.03
126.67
*
102.33
94.02
*
80.19
*
70.73
64.11*
46.62
*
39.67
*
35.60
28.32
Bay #50
c
(ng/fc)
47.25
19.15
13.34
9.71
9.48
6.64
4.97
4.81
3.98
3.43
3.54
r
(ng/g)
671.01
514.43
448.04
424.61
374.46
339.48
313.48
221.13
198.43
179.22
137.97
These values are not measurements but are calculated by mass balance
-------
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Connolly, J. The Effect of Sediment Suspension on Adsorption and Fate of Kepone.
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Furukawa, K., K. Tonomuru, and A. Kamibayashi. Effect of Chlorine Substitution
on the Biodegradability of Polychlorinated Biphenyls, Applied and Environ-
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Gilbert, M. and H. Laudelout. Tactoids in Hydrogen Montmorillonite Suspensions.
J. Colloid Interface Science, Vol. 36, pp. 486-489. 1971.
Glooschenko, W.A., W.M.J. Strachan, R.C. Sampson. Distribution of Pesticides
and PCBs in Water, Sediments, and Seston of the Upper Great Lakes. Pestic.
. Monit. J. Vol. 10, p. 61-67, 1976.
Haile, C.L., G. Veith, G.F. Lee, W.C. Boyle. Chlorinated Hydrocarbons in the
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134
-------
REFERENCES (cont'd)
Halter, M.T. and H.E. Johnson. A Model System to Study the Desorption and
Biological Availability of PCS in Hydrosoils, in Aquatic Toxicology and
Hazard Evaluation, A.S.T.M. STP 634, F.L. Mayer and J.L. Hamelink, eds.,
American Society for Testing, and Materials, pp. 178-195. 1977.
Hamaker, J.W. and J.M. Thompson. "Adsorption", in Organic Chemicals in the
Soil Environment, edited by C.A. Goring and J.W. Hamaker, Marcel Dekker,
Inc., New York. 1972.
Haque,, R., F.T. Lindstrom, V.H. Freed, R. Sexton. Kinetic Study of the
Sorption of 2,4-D on Some Clays. Envir. Sci. Tech. 2(3). p. 207, 1968.
Haque, R., and W.R. Coshow. Adsorption of Isocil and Bromocil from Aqueous
Solution onto Some Mineral Surfaces. Environ. Sci. Technol. Vol. 5,
pp. 139-141, 1971.
Haque, R., D.W. Schtnedding and V. Freed. Aqueous Solubility Adsorption
and Vapor Behavior of Polychlorinated Biphenyl Arochlor 1254, Environmental
Science and Technology, Vol. 8, #2, pp. 139-142. 1974.
Haque, R. and D. Schmedding. Studies on the Adsorption of Selected Poly-
chlorinated Biphenyl Isomers on Several Surfaces, J. Environ. Sci, Health,
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Hiraizumi, Y., M. Takahashi and H, Nishimura. Adsorption of Polychlorinated
Biphenyl onto Sea Bed Sediment Marine Plankton and Other Adsorbing Agents,
Environ. Sci. Technology, Vol. 13, #5, pp. 580-584. 1979.
Huang, Ju-C, Liao, C. Adsorption of Pesticides by Clay Minerals. J. Sanit.
Engr. Div., ASCE, Vol. 96, SA5, pp. 1057-1078. 1970.
Huang, J.C. Effect of Selected Factors on Pesticide Sorption and Desorption
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1748. 1971.
Karickhoff, S.W., D.S. Brown and T,A. Scott. Sorption of Hydrophobic Pollut-
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Laffer, B.C., A.M. Posner, and J.P. Quirk. Optical Density of Montmorillonlte
Suspensions During Sodium-Calcium Exchange, J. Colloid Interface Sci., 20/30
#3. pp. 355-358. 1969.
Lambert, S.M. Functional Relationship between Sorption in Soil and Chemical
Structure. J. Agric. Food Chem. Vol. 15, pp. 572-576, 1967.
Lee, M.C., R.A. Griffin, M.L. Miller, and E.S.K. Ghian. Adsorption of Water
Soluble Polychlorinated Biphenyl Arochlor 1242 and Used Capacitor Fluid by
Soil Materials and Coal Char, J, Environ. Sci. Health, A 14(5), pp. 415-442.
1979.
135
-------
REFERENCES (cont'd)
Lotse,.E.G., D.A. Graetz, G. Chesters, G.B. Lee, and L.W. Newland. Lindane
Adsorption by Lake Sediments, Environ. Sci. Technol., Vol. 2 #5, pp. 353-357.
1968.
Neihof, R. and G. Loeb. Dissolved Organic Matter in Seawater and the Electric
Charge of Immersed Surfaces. J. Mar. Res. 32, pp. 5-12. 1974.
O'Connor, D.J., Connolly, J.P. The Effect of Concentration of Adsorbing
Solids on the Partition Coefficient". Water Research, 14, p. 1517. 1980.
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Metals in Lakes and Reservoirs, Manhattan College Technical Report. 1980.
Paris, D.F., W.C. Steen, G.L. Baughman. Role of Physico-Chemical Properties
of Aroclors 1016 and 1242 in Determining their Fate and Transport in Aquatic
Environments. Chemosphere, 4 pp. 319-325. 1978.
Pavlov, S.P. and R.N. Dexter. Distribution of Polychlorinated Biphenyls
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pp. 65-70. 1979.
Peck, D.E., D.L. Corwin and W, J. Farmer. Adsorption-Desorption of Diuron by
Freshwater Sediments, J. Environ. Quality, Vol. 9, //I, pp. 101-106. 1980.
Pierce, R.H., Jr., Olney, C.E., Felbeck, G.T., Jr. pp'-DDT Adsorption to
Suspended Particulate Matter in Sea Water. Geochim. Cosmochim. Acta,
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Environmental Impact of Nonpoint Source Pollution, edited by M.R. Overcash
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Sweitzer, J. and B.R. Jennings. The Association of Montmorillonite by
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136
-------
REFERENCES (cont'd)
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Tucker, E.S., V.W. Saeger, 0. Hicks. Activated Sludge Primary Biodegrad-
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van Genuchten, M.Th., Wierenga, P.J., O'Connor, G.A. Mass Transfer Studies
in Sorbing Porous Media: III. Experimental Evaluation with 2,.4,5-T. Soil
Sci. Soc. Am. J., Vol. 41, pp. 278-285. 1977.
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New York. 1963.
Veith, G.D., D.W. Kuehl, F.A. Puglisi, G.E. Glass, and J.G. Easton. Residues
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Contam. Toxicol., 5, pp. 487-499. 1977.
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J. Agric. Food Chem. Vol. 26, p. 101-105. 1978.
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1980.
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1254 Between Estuarine Sediments and Water. Bull. Environ. Contam.
Toxicol., Vol. 24, pp 20-26. 1980.
137
-------
Adsorption and Desorption of
Hexachlorobiphenyl
Part B
Exchangeable and Nonexchangeable Components
138
-------
FIGURES - Part B
FIG, it
1-1. Hexachlorobiphenyl Adsorption-Desorption Isotherms Saginaw Bay
Sediment, Station //50. (a) Adsorption and Single Desorption data,
m = 220 mg/Jl (b) Adsorption and Consecutive Desorption data, ra =
1100 mg/JL Data on averages of three replicates 141
1-2. Schematic illustration of the definitions of nonexchangeable, r ,
and the exchangeable components at adsorption, r , and desorption,
xa
r , , assuming a linear consecutive desorption isotherm 144
1-3. Exchangeable-Nonexchangeable Component Model of Desorption:
Illustration of Data Analysis 146
1-4. Hexachlorobiphenyl Adsorption<-Desorption Isotherms, Saginaw Bay
Sediment, Station //50, m = 220 mg/JL (a) Adsorption and Single
Desorption data and Linear Isotherms, (b) Nonexchangeable component
estimates from eq. (1-^3) and linear isotherm, (c) Exchangeable
linear isotherm: adsorption (eq. 1-1) and desorption (eq. 1-2).
estimates of the exchangeable component 147
1-5. Hexachlorobiphenyl Adsorption-Desorption Isotherms - Montmorillonite
m = 220 mg/£, Kaolinite, m = 1000 mgA. (a) Adsorption and Single
Deaorption data and linear isotherms, (b) Nonexchangeable component
estimate (eq. Ir-3) and linear isotherm, (c) Exchangeable linear
isotherm, adsorption (eq. 1-1) and desorption (eq. I-r2) estimates
of the exchangeable component 151
1-6. Hexachlorobiphenyl Adsorption-Desorption and Consecutive Adsorption,
Saginaw Bay Sediment, Station #50 (m = 1100 ppm) and Montmorillonite
(m = 1100 ppm and 2 meq/fc NaHCO..buffer) 158
-------
FIG if Page
^^^^ i ••
1-7. Hexachlorobiphenyl Adsorption-Desorption Isotherms
Saginaw Bay Sediment, Station #50 m = 55 mg/f,
effect of adsorption time. See fig. 3 caption. Dotted
isotherms are the two hour results replotted for visual
reference 159
II- 1. Adsorption and Desorption Partition Coefficient variation
with Adsorbent concentration. Saginaw Bay Station #50
and Montmorillonite. Distilled water and supernatant
aqueous phases 172
II- 2. Nonexchangeable and Exchangeable Partition Coefficient
variation with adsorbent concentration Saginaw Bay
Station //50. Distilled water and supernatant as aqueous
phase 174
II-3. Nonexchangeable and Exchangeable Partition Coefficient
variation with adsorbent concentration, Montmorillonite.
Distilled water and supernatant as aqueous phase 175
II-4. Adsorption and Desorption Isotherms for Saginaw Bay
Stations and Montmorillonite. Aqueous phase is Distilled
Water except for Montmorillonite (2mM NaCHCL) m = 1100
mg/S. except for Station //69 (m = 20,000 mg/JO 179
II-5. Variation of Nonexchangeable Partition Coefficient and
exchangeable distribution coefficient with respect to
percent volatile solids and specific surface area .... 182
ILi-6. Comparison of Calculated (using the regression equations)
and observed coefficients ..... 184
II-7. Ratio of Particulate to Dissolved fraction of HCB versus
adsorbent concentration 187
-------
FIG. # Page
II- 8 Ratio of Particulate to Dissolved fraction of PCS versus
suspended solids concentration for Saginaw Bay. All
cruises. Line if regression equation: I°g10 f /f * =
a + bm; a = -0.532; b = 0.0343 . 188
II- 9. Particulate Fraction versus adsorbent concentration with
and without adsorbent dependent partitioning 190
III-l. Resuspension Experimental Procedure 194
III-2. Resuspension Experiment - Model Predictions and Observations 200
III-3. Exchangeable and Nonexchangeable Component Behavior at
Adsorption and Resuspension Equilibria ......... 201
III-4. Experimental Procedure for Dilution Experiment 203
III-5. Comparison of Observed Particulate to Dissolved Fraction
Ratio-Adsorbent Mass Relation Without Correction due to the
Dilution Equilibration 206
III-6. Comparison of Observed Particulate to Dissolved Fraction
Ratio to Adsorbent Mass, modified by c /c,. as predicted
£1 OX>
from the Exchangeable-Nonexchangeable Model 208
III-8. Exchangeable Partition Coefficient at Adsorption and
Dilution Equilibrium Estimated from the Subsequent Desorption,
versus Adsorbent Concentration, m and m respectively . 211
3. dX>
III-9. Particulate fraction versus adsorbent mass for reversible
desorption, eq. (111-28); and exchangeafale-nonexchangeable
desorption, eq. (111-30). TT = 104«,/kg, v =0.5 ... 215
O X
-------
TABLES - Part B
TABLE
1-1. Isotherm Parameters for HCB Adsorption-Desorption . . . 149
Ir2, Adsorption and Consecutive Desorption Isotherm
Parameters 153
§
II-l. Regression Analyses of Adsorbent Concentration
Effect 176
II-2. Experimental Data for Partition Coefficients 180
II-3. Multiple Linear Regression Analysis* 183
III-l. Resuspension Experiment - Saginaw Bay #50 196
-------
SECTION I
EXCHANGEABLE AND NONEXCHANGEABLE COMPONENTS MODEL
OF ADSORPTION AND DESORPTION
A. Introduction
The reversibility of the adsorption reaction between dissolved organic
chemicals and naturally occurring soils, sediments, and suspended particles
is of fundamental importance in the understanding of the fate of these chem-
icals in the environment. The strong particle binding tendency of persistent
organic chemicals such as DDT and PCB is well known and its importance has
been stressed many times (1,2,3). The issue of reversibility becomes criti-
cal if the adsorption-desorption behavior of a chemical is to be expressed
quantitatively within the framework of mass balance equations. These are
used in mathematical models of the transport of chemicals in soil column
leaching laboratory and field experiments (4) and in models of the fate of
chemicals in natural water systems (5,6,7) In the formulations used to date,
with a notable exception to be discussed below, the formulations used to
express the adsorption and desorption reactions assume reversible behavior,
that is, at equilibrium, the same isotherm applies for adsorption and de-
sorption.
The difficulty with this assumption is that for many organic chemicals
and many naturally occurring adsorbents, laboratory adsorption and subsequent
desorption experiments demonstrate only partially reversible behavior. That
is, the measured desorption does not conform to the adsorption isotherm. This
troublesome behavior has been ascribed to a number of possible experimental
artifacts but the weight of the evidence so far suggests that indeed the ef-
fect is real (8). It is described as a nonsingular or hysteretic isotherm.
In the experiments described in Part A, Section VIII, this nonsingular
behavior was confirmed and, using various experimental procedures, it was
found to persist. This suggests that it is necessary to account for this
behavior in a quantitative and consistent way.
It is the purpose of Part B of this report to present a framework within
which this nonsingular behavior can be analyzed in a manner that can be
easily incorporated into mass balance calculations. The presentation is
139
-------
restricted to linear isotherms since these have been found to be applicable
to HCB adsorption-desorption, at least until small aqueous concentrations are
achieved. However, the basic framework is not restricted to only this class
of isotherms.
B. Previous Methods of Analysis
A typical desorption experiment follows an adsorption experiment in which,
at equilibrium, the sediment bound chemical concentration r = q/m, (the mass
£L
of adsorbate/mass of adsorbent), and the dissolved aqueous concentration, c ,
3
are measured. The solids are separated, the supernatant is discarded and re-
placed by adsorbate-free aqueous phase. At desorption equilibrium the particu-
late, r,, and aqueous, c,, concentrations are measured. If this procedure is
repeated at constant temperature for different initial adsorbate concentrations,
an isotherm results. The adsorption isotherm relates r to c and for the
a a
linear case a partition coefficient for adsorption, TT , can be defined as the
a
slope of the isotherm: r = ir c . Similarly, if the desorption points fall
3. 3. 3.
on a straight line, a desorption "isotherm" can be defined, r, = 'fjC., with
d do
"partition coefficient", ir,. The result is illustrated in fig. I-la for HCB
a
adsorption-desorption with Saginaw Bay sediment.
Strictly speaking, it is incorrect to use the term isotherm for the desorp-
tion curve since in the presence of nonreversibility the desorption points ob-
tained depend on the previous adsorption and the details of the desorption step
rather than being strictly governed by the causal relationship r, = T,C,. How-
ever, with this restriction kept in mind, the procedure is well defined and,
for the sake of a simple nomenclature, this curve is called a single desorption
isotherm. Many examples of these isotherm pairs exist in the literature: for
various adsorbate-absorbent systems: Dieldrin - Montmorillonite (10); pp'-DDT -
Humic Acid (.11); Aldicarb, Terbufos - Soil (12); and PCB (Aroclor 1254) - Estu-
arine Sediment (13). The nonsingular nature of the isotherms is consequence of
the desorption partition coefficient, TT being greater than the adsorption
partition coefficient, IT .
3
A more refined and time-consuming experimental procedure is, after adsorp-
tion, to extend each initial desorption step by performing subsequent multiple
140
-------
HEXACHLOROBIWHNYL ADSORPTION-DESORPTION
SAGINAW BAY STATION #50 SEDIMENT
c
01
•o
01
10
60
PQ
60
C
§
800
600
400
(a) Single Desorption
20C
Adsorption Q
Desorption 4.
C
0)
o
C
o
cq
U
•O
C
o
PQ
•O
01
20C
15C
IOC
5(
Consecutive Desorption
Adsorption Q
Desorption -J-
10
15
20
Fig. 1-1. Hexachlorobiphenyl Adsorption-Desorption Isotherms Saginaw Bay
Sediment, Station //50. (a) Adsorption and Single Desorption data,
m = 220 tng/£ (b) Adsorption and Consecutive Desorption data,
m = 1100 mg/fc. Data on averages of three replicates.
141
-------
desorptions. The points generated in this fashion can also be described by an
isotherm, which may be termed the consecutive desorption isotherm as shown in
fig. I-lb and discussed in Part A, Section VIII. Examples of these consecutive
desorption isotherms with significant nonreversibility have also been reported
for various adsorbate-adsorbent systems: Atrazine - Soil (14,15); Picloram -
loam (4) Fluometuron - fine sandy loam (16); 2,4,5-T - clay (17) and loam (18)
Parathion - Soil (19), Montraorillonite (20), and sandy loam (21); and Diuron -
Soil (15), and lake sediment (22). It was first shown for Atrazine (14) that
each consecutive desorption isotherm, corresponding to each adsorption point,
can be represented as a Freundlich isotherm. However the isotherm parameters
were found to depend upon the individual adsorption concentrations. Thus al-
though the description of the desorption data is adequate, it is not concise.
This framework has been successfully applied to a mass balance analysis of
Picloram - soil column leaching experiments (4). At the start of the experi-
ment the initial adsorption at each computational node within the column
follows the adsorption isotherm as concentrations increase. Then the in-
fluent concentration is decreased and as the concentrations within the column
which are computed to begin decreasing, the isotherm branches off along the
appropriate desorption isotherm with the appropriate interpolated parameters.
An interesting question arises if the influent concentration to the column
were again to increase. What is the proper isotherm relationship in this
case. Such questions, and the desire for a more concise description of the
adsorption-desorption data leads to the model described below.
The results of experimental consecutive desorption studies indicate that
there exists a significant component of the adsorbed HCB which is extremely
difficult to desorb. The problems involved in experimentally achieving zero
aqueous concentration make it uncertain as to whether or not all of this frac-
tion is ultimately desorbable under the varying physical chemical conditions
of natural waters. However, it is clear that for HCB, see fig. I-lb, and the
other data in Part A and for other adsorbates - adsorbent systems cited pre-
viously, that the particulate HCB concentrations for the initial few desorptions
are significantly above the adsorption isotherm. That is, a portion of the ad-
sorbate does not significantly desorb even at low aqueous concentrations.
142
-------
To idealize the situation, consider fig. 1-2. The adsorption isotherm is
assumed to be linear as is the initial stages of the consecutive desorption
isotherm which is presumed to describe the behavior of the readily reversible
fraction. This idealization is important since it limits the applicability
of the analysis to those aqueous concentrations for which the consecutive
desorption data conform to the linear assumption. Define the nonexchangeable
component concentration, r , as the extrapolated intersection of the consecu-
tive desorption isotherm and the ordinate. Define the exchangeable components
at adsorption, r , and at the first desorption, r , as the difference between
xa XQ
the observed adsorption and desorption particulate concentration and the extrapo-
lated nonexchangeable concentration:
This component is exchangeable since it responds to the change in aqueous con-
centration from c at adsorption equilibrium to c, at desorption equilibrium.
3 d
From the geometry of the linear isotherms, or from an algebraic deriva-
tion given in Appendix I of this section, the exchangeable and nonexchangeable
components can be computed from each pair of adsorption (r , c ) and single
Si &
desorption (r , c ) values. The equation for the nonexchangeable component is:
r - 3 r
'--r4 «-»
where 6 = c /c . The exchangeable components follow by difference, eqs. (1-1)
u 3
and (1-2). The analysis of a hypothetical set of data is illustrated in fig.
1-3. A conventional adsorption-desorption data set (assuming three adsorption
points and, three desorption points for clarity) is shown in fig. I-3a. The
two distinct isotherms are shown. Each single pair of points, corresponding
to a single adsorption-desorption experiment, are linearly extrapolated and
the intersection of this line and the ordinate defines the particulate con-
centration, r , which is nonexchangeable (since it remains on the particles
even at zero aqueous concentration). Once the nonexchangeable component con-
centration, r , has been found, the differences between this concentration
143
-------
EXCHANGEABLE (r ) AND NONEXCHANGEABLE (r )
COMPONENTS OF ADSORPTION
LINEAR CONSECUTIVE DESORPTION ISOTHERM
c
-------
and that found at adsorption and desorption equilibria must be the exchange-
able component since two components are assumed to be present. The fact that
it responded to the decrease in aqueous concentration that occurred from ad-
sorption to desorption equilibrium supports its exchangeability. Note that
two exchangeable component data points result: at adsorption equilibrium, r ,
xa
and at desorption equilibrium, r ,. These correspond to the two aqueous con-
centrations c and c,, respectively. If this analysis is repeated for the
a. d
remaining two adsorption-desorption data pairs in the illustration, the result
is six pairs of exchangeable component-aqueous concentration data.
The validity of this analysis depends upon the observation that all the
exchangeable component data conform to a single isotherm, fig. I-3c. The same
isotherm applies to all exchangeable component data, regardless of whether
they correspond to the quantity of exchangeable component that is present at
adsorption, r , in equilibrium with aqueous concentration, c , or at desorp-
xa a
tion, r ,, in equilibrium with aqueous concentration, c,. That is, the ex-
changeable component is behaving in accordance with classical reversible
adsorption-desorption theory.
The three nonexchangeable component concentrations calculated from the
data analysis have also been found to follow one isotherm, illustrated in fig.
I-3d. They are a linear function of the adsorption aqueous concentration as
illustrated.
Figure 1-4, which are the experimental data in fig. I-la analyzed using
eqs. (.1-1,2,3), shows that indeed all the exchangeable adsorption and desorp-
tion points are described by a single, in this case linear, exchangeable iso-
therm:
r = TT c (1-4)
xx
i
independent of which adsorption experiment is considered, and whether r = r
X 3C3
or r and c = c or c, respectively (Figure I-4c).
3CQ cl d
145
-------
(a)
Single Desorption
"Isotherm1^
V
Adsorption
Isotherm
60
C
g
T-(
(b)
Exchangeable Components
Nonexchangeable Component
(0)
0>
§ (0
o
u
1
o
« r
4J *
I
T-l
"O
(11
Exchangeable Component
Isotherm
(d)
Nonexchangeable ComponenJ
Isotherm
Aqueous Concentration (ng/Z)
Fig. 1-3. Exchangeable-Nonexchangeable Component Model of Desorption:
Illustration of Data Analysis
146
-------
HEXACHLOROB1PHENYL ADSORPTJON-DESORPTJON
SAGINAW BAY STATION //50 SEDIMENT
10'
•o
M
•>
A
10'
'. Desorption
"- rd ™
10'
» ««« ».---«—i—t-t 11
; 10
60
60
c
o
C
0)
o
c
o
u
ta
o
o
10"
10'
(b)
Nonexchangeable
Adsorption
Isotherm
a i a i • • a i a .»
10°
10'
a
OJ
s
•H
•O
(U
(A
10
10'
? (c)
I Exchangeable Isotherm
Adsorption, r
(0) Xa
• Desorption
r ,
1-4.
Hexachloroblphenyl Adsorption-Desorption Isotherms, Sagiriaw Bay Sediment, Station
' m8 * U) AdS°rPtlon and S1"8le Desorption data and Linear Isotherms.
fbNonexCha K!
(b) Nonexchangeable component estimates from eo (l-^^
(c Exchangeable linear isotherm: adsorption (I^/J-J and
estimates of the exchangeable component.
147
' 1-2) .
-------
Figure I-4b illustrates that for these isotherm pairs the nonexchangeable
component is a linear function of the equilibrium adsorption aqueous concen-
tration, c , leading to a nonexchangeable isotherm:
a
r = TT c (1-5)
o o a
Since the adsorption isotherm is linear, the nonexchangeable component
can also be expressed in terms of the particulate adsorption concentration: .
r = TT r /TF . Which is the more useful characterization is discussed subse-
o o a a
quently. The experimental conditions and isotherm parameters are listed in
Table 1-1. -
D.Relationship to.Single Desorption Isotherm
The formulation presented above is based upon the consecutive desorption
isotherm (fig. I-lb). It is of interest to inquire what is the relationship
of this analysis to the single desorption isotherm (fig. I-la). It can be
shown (Appendix II of this section) that, if the single desorption and adsorp-
tion isotherms are linear, and essentially all the adsorbate mass is asso-
ciated with the particles at the start of the desorption, that is, that the
glass desorption is small and mr ** c . as is the case for these experiments
ci i. Q
(Section II of Part A), then the exchangeable and nonexchangeable components
also follow linear isotherms, eq. (1-4) and (1-5) with partition coefficients:
TT
= __—-5 _ (X_6)
x 1 4- m(ir,-iT )
d a
mn (IT -TT )
a a a /T 7\
TT = • ; r- (I-/J
o 1 + jn(Tr,-iT )
d a
>
These relationships provide the connection between the conventional adsorption,
TT , and single desorption TT partition coefficients and the partition coeffi-
cients of the exchangeable, TT , and nonexchangeable, TT components. In addi-
tion, they establish the fact that linear adsorption and single desorption
isotherms imply linear exchangeable and nonexchangeable isotherms.
148
-------
TABLE 1-1
Isotherm Parameters for HCB Adsorption-Desorption
Adsorbent
Saginaw Bay #50
Montmorillonite
Kaolinite
m
sorbent
entration
(mg/i)
55
55
220
220
1000
Adsorption
Time
(hr)
2
48
3
3
3
Desorption
Time
(hr)
3
48
3
3
3
Partition Coefficients
(A/kg)
IT IT IT IT
a d o x
17000 25100 5270 11700
18100 60900 12700 5400
9170 3070
4250 2350
730 327
12200 25800
6600 15600
1060 3290
fig.
(1-6)
(1-6)
(1-3)
(1-4)
(1-5)
Aqueous Phase is Distilled Water for all experiments, Temperature = 23°C
-------
Since the exchangeable isotherm applies at both the adsorption and single
desorption aqueous concentration, and r is constant for an adsorption-desorp-
o
tion experiment, each consecutive desorption isotherm can be expressed as:
r = r + TT c (1-8)
O X
which is linear. Thus these results lead to the conclusion that an analysis
using linear adsorption and consecutive desorption isotherms (fig. 1-2) is
consistent with linear adsorption and single desorption isotherms (fig. I-la),
and both types of isotherms are reasonable representations of linear desorp-
tion data.
The exchangeable and nonexchangeable partition coefficients can be ob-
tained either from an analysis of the individual data, eqs. (1-1,2,3), or from
the partition coefficients, TT , TT , and eqs. (1-6,7). This symmetry is espec-
3. Q
ially useful in analyzing previously published adsorption-desorption data for
which only the adsorption and single desorption isotherms are presented.
A comparison of both these methods is presented in fig. (1-5): HCB ad-
sorption and single desorption data for montmorillonite and kaolinite respec-
tively. The nonexchangeable (fig. I-5b) and exchangeable component estimates
(fig. I-5c) are computed using eqs. (1-1,2,3). The linear isotherms are eqs.
(1-4,5) using average IT and IT. computed from a fit of the adsorption and
single desorption data, fig. (I-5a), and eqs. (1-6) and (1-7) for the par-
tition coefficients. Table 1-1 lists the isotherm parameters. The agree-
ment is basically due to the observed linearity of the adsorption and single
desorption isotherms.
E. Relationship to Freundlich Consecutive Desorption Isotherms
Consecutive desorption isotherms have been analyzed within the framework
of Freundlich isotherms (4, 14, 17). The adsorption isotherm is represented by:
N
r = K c a (1-9)
a a a ^ '
150
-------
HEXACHLOROBIPHENYL ADSORPTION-DESORPTION
MONTMORILLONITE KAOLIN1TE
(a)
10'
Nonexchangeable Component
Adsorption Isotherm
(b)
io3i
...ill. « t .......
10
; Desorption (+)
10
-J—i I 1 »III
10
10
Nonexchanp,eable Component
Adsorption Isotherm
10
10
10
10
102
Exchangeable Component Is.otherm
Adsorption (°), Desorption (+)
io3
10"
10
10
Exchangeable Component Isotherm
Adsorption (a), Desorption (+)
10% xa xd
10
-1
10
10
1-5. Hexachlorobiphenyl Adsorption-Desorption Isotherms - Montmorillonite, m = 220 mg/Jl
Kaoliriite, m = 1000 mg/Jl. (a) Adsorption and Single Desorption data and linear
isotherms, (b) Nonexchangeable component estimate (eq. 1-3) and linear isotherm.
(c) Exchangeable linear isotherm, adsorption (eq. 1-1) and desorption (eq. 1-2)
estimates of exchangeable component.
-------
and each consecutive desorption Isotherm is represented by:
r, - Kdcd d (1-10)
Since the consecutive desorption isotherm intersects the adsorption isotherm
at the adsorption concentration, r, = r at c. = c , so that:
d a d a
N - N
K = K c * d (1-11)
d a a
which indicates that the consecutive desorption Freundlich parameter, K , is
a nonlinear function of the initial adsorption concentration, c .
a
However a peculiar result has been noted: the ratio N /N, is approxi-
£1 Q
mately constant, N /N = 2.3. Table 1-2 presents some examples. It is of
3 d
interest to investigate the implication of this result with respect to an
analysis based upon exchangeable and nonexchangeable components.
As shown in Table 1-2, the adsorption isotherms are almost linear, N -
cl
1, and the partition coefficient is the slope of the isotherm:
dr N -1
TT = —S. = K N c a (1-12)
a dc a a a
a
The consecutive desorption isotherm, when approximated as a-straight line with
a non-zero intercept, eq. (1-8), has a slope TT . If this slope is equated to
Ji
the slope of the Freundlich consecutive desorption isotherm at the point of
intersection of the adsorption isotherm, then:
(1-13)
and using the equality of the isotherms at the intersection, eq. (1-11), yields:
N -1
IT = K N,c a (1-14)
x a d a
and using eq. (.1-12) for K yields:
Si
X
drd
dcd
N -1
= K,N,c
d d a
c.=c_
152
-------
Ui
TABLE 1-2
Adsorption and Consecutive Desorption Isotherm Parameters
Adsorbate
Atrazine
Atrazine
Picloram
2,4,5-T
Adsorbent K N
a N a
(ng/kg)/(ng/JO a
Mohave Soil
Walla Walla Soil
Norge Loam
Glendale" Clay Loam
0.21
2.61
0.18
0.616
1.0
0.85
0.94
0.792
a d
2.3
2.3
2.22-2.98
2.30
o
(a/kg)
0.12
0.87-1.08
0.095-0.125
0.20 -0.24
X
U/kg)
0.091
0.77-0.96
0.060-0.073
0.12 -0.15
Ref
(14)
(14)
(14)
(17)
TT and TT calculated using eq. (1-17) and eq. (1-13) and the experimental range in c .
OX 3
-------
N
Since N /N is approximately constant and u is constant for linear adsorption
da 3.
isotherms, and almost constant for N ^ 1, the exchangeable partition coeffi-
a
cient is the same for each consecutive desorption isotherm. Hence to" the
extent that a linear approximation of the consecutive desorption isotherm is
a reasonable representation, the fact that N,/N is the same for each consecu-
d a
tive desorption isotherm is a reflection of the fact that all the consecutive
desorption isotherms can be represented by a single exchangeable component
with partition coefficient, IT .
X
The fact that the desorption Freundlich constant, K , is a function of
the adsorption concentration, c , eq. (1-11), is reflected in the fact that
a
the nonexchangeable component given by eq. (1-8),
r = r - IT c (1-16)
o a x a
can be expressed in terms of the Freundlich parameters, eq. (1-9) and (1-15),
yielding:
N N
'o = " - /> KaCa 3 (I-17>
a
Since N,/N is constant for every consecutive desorption isotherm, r is a
da o
function only of the adsorption concentration, c . For a linear adsorption
a
isotherm, N = 1, and the nonexchangeable partition coefficient is:
a
% = (1 - ^) Ka (1-18)
a
which is, again, the same for each consecutive desorption isotherm. Hence, eqs.
(1-15) and (1-18) represent all the consecutive desorption isotherms consistently
in terms of two parameters: ir and IT , as compared to the individual Freundlich
O X
isotherms for each consecutive desorption isotherm. The observational fact
that N./N is constant for each isotherm is the key to this simplification.
u a
154
-------
The nonexchangeable and exchangeable partition coefficients corresponding
to the Freundlich parameters are listed in Table 1-2. The indicated ranges
are the effect of the slight nonlinear adsorption isotherm. The linear
approximation of the adsorption isotherm results in only slight changes in
IT and IT . The critical approximation is that the consecutive desorption
isotherm is linear. This is reasonable until fairly low aqueous concentra-
tion achieved after multiple desorptions, as discussed previously.
F. Discussion
The proposed linear approximation describing the binding of organics to
sediments is clearly an oversimplification of the actual process. In the case
of HCB, experimental evidence suggests that under certain chemical conditions
the binding to sediments during consecutive desorption may be described by a
curvilinear isotherm which may or may not ultimately demonstrate complete
desorbability. It is also quite possible that the actual adsorption process
may involve binding to sites of a gradation of energies rather than the two
arbitrarily defined fractions (exchangeable and nonexchangeable). Neverthe-
less, there exist distinct advantages for data analysis which result from
treating HCB and other organic adsorption study results in terms of this
approximation.
For a sediment adsorbed organic molecule such as HCB, it may not be
experimentally feasible to generate consecutive desorption isotherms under
all of the chemical conditions of concern from an environmental modeling
standpoint.
For instance, it will be shown that the magnitude of the adsorbed and
readily desorbed HCB sediment fractions is a function of a variety of para-
meters including aqueous composition and sediment concentration. This sug-
gests that a large number of consecutive desorption isotherms would be re-
quired to adequately define the environmental behavior of HCB. However, for
certain chemcial conditions (such as high (> 1000 mg/£) sediment concentra-
tions) it is extremely difficult to obtain consecutive desorption isotherms
at the aqueous HCB concentrations of concern in natural water systems. The
extremely small aqueous HCB concentrations which result from sediment HCB
release during successive desorption cycles possess large experimental un-
certainties, require a prohibitive number of experimental data points, and
lead to ill defined isotherms.
155
-------
From the standpoint of environmental modeling the linear approximation
offers a means of refining currently used assumptions such as complete re-
versibility for organic adsorption to sediments. From the environmental
chemical perspective the approximation can be utilized to separate reaction
variables and provide an aid in interpreting organic binding mechanisms.
These applications may be demonstrated by examining derivation results for
both experimental binding mechanism and multiple cycle adsorption-desorption
studies.
G. Consecutive Adsorption
In order to incorporate environmental cycling within mass balance calcu-
lations there exists a need to provide a method of analyzing the behavior of
adsorption and desorption under changing aqueous PCB concentrations. (An ex-
ample would be sediments initially exposed to high PCB concentrations subse-
quently migrating into environments characterized by lower but varying aqueous
PCB levels.) The isotherm treatment of the present study has been utilized to
predict how such changes would affect the sediment adsorbed PCB fractions.
Model predictions have been compared with the results of laboratory experi-
ments designed to simulate the cycling process described above. As discussed
in detail in the methods section these experiments involved an adsorption step
followed by a single desorption (the standard isotherm experiment) and following
this a series of consecutive adsorptions. For small incremental increases in
the aqueous concentration during the adsorption steps, small such that they do
not exceed the initial adsorption concentration, c , the nonexchangeable compo-
&
nent should be constant and only the exchangeable component should vary. .That
is, this portion of the data should follow the consecutive desorption isotherm:
r = r + TV c c, c (1-20)
OX S
156
-------
Figure 1-6 presents the results for HCB binding to Saginaw Bay sediment and
montmorillonite. The initial adsorption, single desorption, and the subsequent
consecutive adsorption data are differentiated in the legend. The range of the
quadruplicated data are as indicated. For Saginaw Bay sediment, the theoretical
prediction is followed almost exactly. The agreement for montmorillonite is
less satisfactory although it also clearly shows a change in behavior as the
aqueous concentration exceeds c . These results provide at least a preliminary
3
answer to the question posed at the outset: namely, how are these isotherms to
be interpreted if the aqueous concentration, c(t), is changing in time during a
mass balance calculation. Assuming local equilibria the nonexchangeable compo-
nent reacts in response to the maximum aqueous concentration achieved up to that
time:
c (t) = max c(t) (1-22)
ma
whereas the exchangeable component follows the linear reversible isotherm:
r = TT c(t) (1-23)
A A
in all circumstances. Since this interpretation is based upon rather limited
experimental data it should be regarded with caution. However it does suggest
the advantages of applying the proposed model to scenarios of this type as
opposed to assuming a completely reversible formulation for HCB adsorption-
desorption.
H. Kinetic Effects
The assignment of exchangeable and nonexchangeable sediment HCB components
in accordance with the method described above also offers potential advantages
in the utilization of kinetic data to evaluate binding mechanisms. Of particu-
lar interest is the effect of time on the relationship between the exchangeable
and nonexchangeable HCB components. The results of experiments designed to
assess these effects can be seen from the comparison (presented in figure 1-7)
of the adsorption, single desorption, exchangeable and nonexchangeable iso-
157
-------
HEXACHLOROBIPHENYL ADSORPTION-DESORPTION
CONSECUTIVE ADSORPTION
' Saglnaw Bay Station *50
«
«
•
»
160
120
•$• Adsorption
4- Desorptlon
4. Consecutive Adsorption
0 10 20 30 40 SO
Aqueous HCB Concentration, c, (ng HCB
Fig. 1-6. Hexachlorobiphenyl Adsorption-Desorption and Consecutive Adsorption
Saginaw Bay Sediment, Station #50 (m = 1100 ppm) and Montmorillonite
(m = 1100 ppm and 2 meq/X, NaHCO» buffer)
158
-------
Saginaw Bay Station #50
Adsorption Time = 2 hr. (a)
Adsorption Time = 48 hr.
ncf
c
8-"
-------
therms found for 2 hour and 48 hour adsorption times. (It has been found that
increasing the desorption time has no effect on the desorption isotherms.) The
adsorption partition coefficient is slightly increased (ir = 1700 -*• 1800 SL/kg)
cl
but the desorption partition coefficient is markedly increased (IT = 25000 -»•
61000 £/kg). As result the nonexchangeable component partition coefficient
increases by approximately a factor of two (TT = 5100 ->• 12800 £/kg) and the
exchangeable component partition coefficient decreases (IT = 11800 ->• 5400 A/kg)
X
by approximately the same factor.
Since the partition coefficient can be thought of as the product of a
binding strength constant and a capacity factor, the question arises as to
which factor is responsible for the increase in TT with time. That is, are
HCB molecules being bound more strongly at a fixed number of sites or is the
number of strongly bound sites increasing with time. Although the exchangeable
component data are quite scattered there is some suggestion that the increase
in the nonexchangeable fraction is accompanied by an equal and opposite decrease
in the magnitude of the exchangeably bound fraction. This would seem to imply
that a change in the capacity factor of the nonexchangeable component is occur-
ring rather than a change in the binding strength. Such an effect could con-
ceivably result from a transformation of reversible binding sites to strong
binding sites (metastable complex •*• stable configuration). If the magnitude
of the exchangeable partition coefficient had remained constant during the ex-
periment it would have implied that separate sites are responsible for reversible
and resistant binding of HCB. Clearly, more experimental data is warranted be-
fore a choice of change in capacity factor versus binding strength constant can
be made with certainty. However, the results again illustrate the utility of
considering the data In terms of reversible and resistant components.
I. Summary
It is useful to summarize the experimental basis for the component hypothe-
sis. The definition of the nonexchangeable or perhaps better termed the resis-
tant component follows from two observations: (1) that the single desorption
isotherm is not coincident with the adsorption isotherm, that is that this pair
of isotherms display hystersis; and (2) that the consecutive desorption isotherm
can be approximated by a straight line, at least for the first few consecutive
160
-------
desorptions. These are distinct observations and each can be examined in
the light of experimental evidence.
The presence of hystersis in the adsorption and single desorption iso-
therms can be ascribed to a number of phenomena and possible experimental
artifacts. A recent review (8) concluded that hystersis persists in most
cases in spite of experimental modifications designed to eliminate the phen-
omena. Our experimental investigations for HCB have evaluated the influence
of increasing the desorption times (no reduction in hystersis was observed)
and the influence of using the dilution method to produce the desorption iso-
therm (hystersis was still present). Thus HCB hystersis is not being caused
by insufficient desorption time or by the centrifugation used to separate the
solids prior to the desorption experiment.
The second observation, that the consecutive desorption isotherm is linear
is experimentally observed for the first few consecutive desorptions. After
that the data are inconclusive in one case (fig. I-1B) and, at a lower sedi-
ment concentration, they suggest that in fact the consecutive desorption iso-
therm decreases toward the origin (fig. VIII-12 of Part A). It is for this
reason that the "nonexchangeable" component responsible for this behavior is
more appropriately termed resistant. That is the resistant component does
not desorb at all for the first few consecutive desorption (i.e. nonexchange-
able), and may or may not subsequently desorb. Its existence accounts for
the observed hystersis in the single desorption experiments, and it has been
argued above that experimental artifacts are not the cause for hystersis.
The question of the linearity of the consecutive desorption isotherm
can be interpreted in terms of the resistant component consecutive desorption
isotherm: is it a horizontal straight line indefinitely (as shown in fig. 1-2)
or is it initially a horizontal straight line which eventually curves to the
origin as aqueous concentrations approach zero. In either case it is clear
that the resistant component consecutive desorption isotherm is a straight
line initially and that it is linear for the consecutive adsorption data pre-
sented in fig. 1-6. These observations justify the assumption employed in
this analysis. Further detailed experimental investigations are required to
establish the shape of the resistant component consecutive desorption isotherm.
161
-------
The issue is significant since it relates to the ultimate desorbability
of PCB from previously contaminated sediments. But this issue should not be
confused with the existence of hysteretic isotherms. The hypothesis employed
in this analysis sharpens the question of ultimate desorbability since it is
clear that the issue is the behavior of the resistant component at aqueous
concentrations approaching zero rather than the overall utility of separating
the data into the two components using the method proposed above.
J. Conclusions
From an empirical point of view, the analysis of HCB isotherm data in
terms of exchangeable and resistant components is quite successful in pro-
viding a concise and unified description. The full adsorption and desorption
isotherm data set is represented by two partition coefficients, TT and ir .
O X
The relationship between consecutive desorption isotherms and a single de-
sorption isotherm has been clarified for the linear isotherm case at least,
and they have been shown to be equivalent in the sense that either can be
used to obtain the relevant partition coefficients for the components. The
consecutive adsorption experiments provide preliminary confirmation that
the exchangeable and resistant components behave in accordance with their
expected properties. The exchangeable component exhibits no hystersis in
response to changes in aqueous concentrations, and the resistant component
reacts only to increases in aqueous concentrations that exceed the initial
adsorption concentration. The use of the method described above to esti-
mate the exchangeable and resistant components of adsorption-desorption
provides additional insight into the influence of kinetics, sediment type,
aqueous phase modifications (e.g. altering the pH) since it is possible to
observe the effects on each of the components individually. Perhaps such
investigations will help to clarify the mechanisms responsible for hyster-
etic isotherms and clairfy the issue of ultimate desorbability.
162
-------
Notation
c = dissolved aqueous concentration of HCBP at adsorption equilibria (ng/Jl)
3.
c, = dissolved aqueous concentration of HCBP at desorption equilibria (ng/Jl)
N
ft
K = Freundlich adsorption parameter (ng/kg)/(ng/&)
Nd
K, = Freundlich consecutive desorption parameter (ng/kg)/(ng/£)
m = adsorbent concentration (kg/£)
N = Freundlich adsorption exponent
3.
N, = Freundlich consecutive desorption exponent
r = sediment bound concentration of HCBP at adsorption equilibria (ng/g)
£L
r, = participate concentration of HCBP at desorption equilibria (ng/g)
r = resistant component of adsorbed HCBP (ng/g)
r = reversible component of adsorbed HCBP at adsorption equilibria (ng/g)
XcL
r , = reversible component of adsorbed HCBP at desorption equilibria (ng/g)
TT = partition coefficient for adsorption (Jl/kg)
3
TT = partition coefficient for single desorption (A/kg)
IT = partition coefficient for the resistant component (i/kg)
TT = partition coefficient for the reversible component (£/kg)
X
163
-------
- A 1 -
Appendix I
Derivation of Exchangeable and Nonexchangeable Components.
The equilibrium particulate concentrations that result from an adsorption
experiment, r at aqueous concentration c , and a subsequent desorption, r at
& 3L Q
aqueous concentration c, , are assumed to be the sum of a nonexchangeable com-
ponent, r , and the exchangeable components, r and r ., that is:
O Act XQ
rd ' ro + rxd (A2)
The nonexchangeable component is the same for both adsorption and desorption
since it is assumed to be nonexchangeable and therefore not affected by the
desorption step, whereas the exchangeable component reacts to the lower
aqueous concentration at desorption and decreases from r to r . at
equilibrium.
It is further assumed for this derivation that the exchangeable component
follows a linear isotherm with partition coefficient, TT , so that the exchange
jL
able components are related to the aqueous concentration by the equations:
rxa = \Ca (A3)
rxd = \ Cd
Using eq. (A2) to solve for r and substituting eq. (A4) for r , yields;
O JtQ
r = r , - TT c, (A5)
o d x d
Substituting eq. (A3) for ir and using eq. (Al) for r yields:
X X3
ro = rd-r (ra-ro> , (A6)
a
The final result for the nonexchangeable component is:
= rd " g ra (A7)
ro 1-0
where 8 = c /c . The exchangeable components are obtained by subtraction
d a
using the defining eqs. (A1,A2):
rxa=ra-ro
rxd = rd * ro (A9)
164
-------
- A 2 -
The assumption of a linear exchangeable isotherm is checked by examining a
composite plot of r versus c and r , versus c. for linearity.
xa a xd d J
It is significant to note that the derivation does not involve a mass
balance argument so that the equations are applicable even if the experi-
mental vessel is acting as a third phase with adsorption and desorption
characteristics of its own. Also it is not necessary that the desorption
be carried out by removing all the supernatant after centrifugation or that
a correction be made for any residual aqueous phase. In fact the equations
apply to whatever method is used to accomplish the desorption; for example
by using an immiscible organic solvent as a third phase to accomplish the
desorption (15), It is only necessary that the linearity assumption for the
exchangeable component is satisfied and that its partition coefficient is
unaffected by the desorption method employed.
If the linearity assumption is found to be inappropriate, it is still
possible to separate the components. The derivation using nonlinear ex-
changeable isotherms (e.g. a Langmuir or Freundlich equation) is similar with
the exception that an unknown parameter (.the Langmuir binding constant and
the Freundlich exponent respectively), remain in the equations for r and r .
Thus an iterative fitting procedure is required to make the estimates.
165
-------
- A 3 -
Appendix II
Relationship between Linear Adsorption, Single Desorption, Nonexchangeable,
and Consecutive Desorption Isotherms.
It is the purpose of this derivation to show that if the adsorption and
single desorption isotherm are linear, then the nonexchangeable and the
consecutive desorption isotherm are also linear. The linearity assumptions
for adsorption and desorption are expressed by the equations:
r ."• TT c (AlO)
a a a
The nonexchangeable component concentration is given by (eq. A7) :
rd " B ra (A12)
f J= • * '
o 1 - 8
which can be expressed in terms of aqueous concentrations only using eqs.
(AlO, All):
_ Cd ClTd " V
ro 1 - c./c (A13)
d a
A relationship is available between c. and c If the desorption is carried
a a
out by removing essentially all the supernatant and replacing it with adsor-
bate-free solvent (or equivalently that the mass of adsorbate associated
with the residual supernatant is negligible) and that the vessel desorption
is negligible. Then the mass of adsorbate prior to solvent addition, m r ,
3
is equal to the total mass of adsorbate in the dissolved and particulate
phases:
m r = c, + m r (A1A)
ad d
where m is the mass of adsorbent present. Substituting eqs. (AlO, All) yields
the desired relationship:
m it c
(A15)
d
This relationship in eq. (A13) yields:
.- , ,^
r «. a d a c (A16)
o 1 + m(ir , - TT )
d a
166
-------
- A 4 -
so that r is linearly related to c and by the definition of TT , eq. (4):
O 3 O
m TT (TT - TT )
^o = 1 +am(Tr - I ) (
d a
Hence, if the linearity and mass balance equations are applicable, the resistant
component partition coefficient can be computed from the adsorption and single
desorption partition coefficients.
Similarly the consecutive desorption isotherm can also be shown to be
linear. This is equalvalent to showing that the slope of the consecutive de-
sorption isotherm, which is the partition coefficient of the reversible compo-
nent, is the same at the adsorption and desorption aqueous concentrations.
The reversible component concentration at adsorption equilibrium is given
by eq. (A8):
r = r - r (A18)
xa a o
or, using eqs. (A10) and (A16):
m ir (IT - TT )
a d a / A i r\ \
r • = IT c = -=—: 7 . c (A19)
xa a a 1-1- m(Tr, - it ) a \«*'/
d a
which simplifies to:
IT
r = T—r—-r r c (A20)
xa 1 + m(ir - TT ) a
Q a
Similarly the reversible component concentration at desorption equilibrium
is given by eq. (A9):
r , = r - r (A21)
xd d o
m it (IT - IT ) 1 + m TT
= "jCj - i J* / ^ ~ c. (A22)
d d 1 + ra(TT, -Tr)mTrd
da a
where eq. (All) and eq. (A16) have been used for r, and r and eq. (A15) for
d o
c . Combining terms and simplifying yields:
a
IT
3 (A23)
xd 1 + m(Tr - IT ) d
d a
167
-------
- A 5 -
Hence the reversible component isotherm has the same slope at c , eq. (A20),
3.
and c,. eq. (A23) so that the consecutive isotherm is linear and further the
d
reversible component partition coefficient is given by:
IT
TT = -7———. r- (A2A)
x 1 + m(ir - IT )
d a
It should be noted that these relationships can be easily corrected for
the mass associated with the residual supernatant if its volume is known
by simply adding that mass to the left hand side of eq. (A14).
168
-------
SECTION II
EFFECT OF SEDIMENT CONCENTRATION AND COMPOSITION
A. Introduction
The effect of sediment concentration on the extent of partitioning of HCB
has been investigated in Part A, Section VIII, of this report. It is related
to the well-known phenomena that the fraction of adsorbate in the particulate
phase increases as the mass of adsorbent increases. What is surprising is
that in the case of HCB, the extent to which the particulate fraction increases
is inconsistent with the conventional assumption that the isotherm parameters
are independent of the sediment concentration.
The experiments which reproduce this effect for HCB adsorption have been
discussed in Part A of this report. Possible experimental artifacts which may
explain the effect have also been investigated. It has been found that the
effect is not caused by nonlinear isotherms improperly characterized by a
single partition coefficient, or by aqueous or particulate phase changes that
result as a consequence of adsorbent concentration increases. The conclusion
from these experiments is that the phenomena is real and must be considered
systematically in the description of HCB adsorption and desorption.
The second focus of the experiments described in this report is the extent
of reversibility of the adsorption reaction. Since both adsorption and desorp-
tion are occurring in natural systems, the experiments were designed to address
both processes. It was consistently found that the adsorption reaction was not
completely reversible, and, depending upon the details of the experiment, a.
substantial quantity of adsorbed HCB remained in the particulate phase after
desorption, in excess of that which would be predicted by the adsorption iso-
therm.
This disturbing result implies that the conventional reversible description
of adsorption-desorption is inadequate and that a. refined quantitative desorp-
tion is required. It has been shown in Section I that the process can be con-
sistently described if the adsorbed HCB is assumed to be composed of two compo-
nents: an exchangeable component which readily adsorbs and desorbs reversibly;
and a nonexchangeable, or resistant, component which resists desorption during
169
-------
the single desorption phase of the experiment, and may or may not ultimately
desorb during consecutive desorptions. The irreversibility has been found to
persist under a variety of experimental modifications: it is not affected by
either the time of desorption or the manner of phase separation, and it
occurs for clay adsorbents as well as Saginaw Bay sediments.
The dual focus of these experiments makes it possible to investigate the
effect of sediment concentration on both the exchangeable and nonexchangeable
components of HCB adsorption. It is shown below that the observed systematic
variation of adsorption and single desorption partition coefficient as a
function of sediment concentration can be explained in terms of the behavior
of the exchangeable and nonexchangeable partition coefficients. The latter
has been found to be approximately constant with respect to adsorbent concen-
tration variations, as would be expected from conventional adsorption theory;
whereas the exchangeable partition coefficient has been found to be inversely
proportional to adsorbent concentration. The interplay of these two compo-
nents determine the variation of the adsorption and single desorption parti-
tion coefficients as a function of sediment concentration. It is the purpose
of this section to present the analysis of these experimental data and to
relate these findings to the conventional descriptions of adsorption-desorp-
tipn as applied to the computation of the fate of PCB in natural water sys-
tems.
B. Definitions and Methodology
For isotherm experiments at a fixed sediment concentration with many
pairs of adsorption (r ,c ) and desorption (r ,c ) data, the adsorption, ir ,
3. 3 (. Q d 3.
and desorption, IT,, partition coefficients are obtained as the slopes of r
versus c and r. versus c, respectively. For experiments that are designed
a ct Q
to investigate the effect of sediment concentration variations it is incon-
venient to evaluate a complete isotherm at each sediment concentration of
interest. Rather the concentration of sediment is varied systematically. In
order to reduce the effect of systematically varying aqueous concentrations -
for example if a constant initial HCB concentration is used, then the equi-
librium dissolved concentration would decrease systematically as adsorbent
concentration increases - the initial concentration is varied to produce sim-
170
-------
ilar equilibrium dissolved concentrations as discussed in Section VIII of
Part A. The results of this experimental design are (triply replicated) pairs
of adsorption (c ,r ) and desorption (c, ,r.) points at varying adsorbent concen-
33 Q Q
trations, m. The partition coefficients are then calculated from the ratio of
r and c, i.e., IT =r/c and IT. - r./c..
a a a d d d
For some of the initial experiments which were focused on desorption,
the total HCB concentration at adsorption equilibria, CT , was not measured
LcL
(Type 2 experiment) so that a direct estimate of r is not available. If it
Q.
is assumed that no significant vessel adsorption or desorption occurs during
the desorption phase of the experiment then the mass balance relationship:
m r = c_, can be used to estimate r . Figure III-7 of Part A presents the
a Td a
experimental confirmation of this relationship for those experiments in which
both r and c_. are available. No significant bias is observed which confirms
a Td
the assumption that no significant vessel adsorption or desorption occurs
during the desorption phase of the experiment.
The variations of the adsorption, IT , and desorption, TT,, partition co-
a d
efficients as a function of adsorbent concentration are shown in fig. II-l
for Saginaw Bay sediment (Sta. #50) and montmorillonite, and two aqueous
phases, distilled water and supernatant - which is distilled water previously
equilibrated with uncontaminated adsorbent - are shown. The data points are
averages of triplicate replicates as usual, the curves are discussed below.
The systematic decrease of both adsorption and single desorption partition
coefficients as adsorbent concentration increases .is apparent, as is the
irreversibility of adsorption-desorption, illustrated by the fact that IT,
d
exceeds IT . It can be seen that the extent of irreversibility increases as
adsorbent concentration increases as pointed out in Part A, Section VIII,
which contains a more complete description of these experiments and the ex-
perimental modifications employed to insure that the results are not experi-
mental artifacts. The purpose of this section is to analyze these results in
terms of exchangeable and nonexchangeable component behavior.
The definitions of the exchangeable and nonexchangeable components are
given in Section I. From the geometry of the relationships it is clear that
171
-------
Saginaw Bay - Station #50
•vj
Nl
71
D Adsorp tion ,n
10
U)
i-l
C
..TO " 100 1000
Adsorbent Concentration ,m, (rag/1)
Montmorillonite
Distilled Water
100 1000
Adsorbent Concentra tion, m , (mg/1)
10
Superna tant
Hill
1 • •' *"
10 100 1000
Adsorbent Concentration,™, (mg/1)
10"
10"
Supernatant
10 100 1000
Adsorbent Concent rat ion, m, (mg/1)
Fig. II-l. Adsorption and Desorption Partition Coefficient variation with Adsorbent concentration. Saginaw
Bay Station #50 and Montmorillonite. Distilled water and supernatant aqueous phases.
-------
the partition coefficients for the exchangeable and nonexchangeable components
are given by:
r -r
7T =-§_! (II-1)
X C3-Cd
and
(II-2)
The second equation follows from the fact that IT = tr + IT , These equations
a o x
are re-expressions of eqs. (1-6) and (1-7) of the previous section.
C. Sediment Mass Effects for Exchangeable and Nonexchangeable Partition
Coefficients
The results of these experiments analyzed in terms of exchangeable and
nonexchangeable partition coefficients, eq. (II-l) and eq. (II-2), are shown
in fig. (II-2) for Saginaw Bay sediment (Sta. //50) and fig. (II-3) for mont-
morillonite. They correspond to the adsorption-desorption data presented in
fig. 1-1. The open squares represent triplicate logarithmic averages of the
partition coefficients. The filled circles are the logarithmic average ±
the standard error of the average from isotherm experiments each of which was
conducted at the fixed adsorbent concentrations as indicated in the figure.
(These isotherms were only available for distilled water as the aqueous phase.)
For the Saginaw Bay sediment, fig. (II-2), it is found that the nonex-
changeable partition coefficient, TT , is independent of sediment concentra-
tion whereas the exchangeable partition coefficient, ir , is inversely propor-
Jv
tional to sediment concentration. The lines on the plot have slopes of zero
and minus one respectively. For montmorillonite, fig. (II-3), the nonexchange-
able partition coefficient appears to decrease slightly for distilled water
and more markedly for supernatant as the aqueous phase. However, the exchange-
able partition coefficients are both inversely proportional to sediment concen-
tration as was the case for Saginaw Bay sediment.
Regression analyses of these data, using the relationship: IT = am
(O'Connor and Connolly, 1980) are given in Table II-l. The slopes, n, for
173
-------
SAGINAW BAY - STATION #50
Distilled Water
10 : Nonexchangeable Partition Coefficient
B
00
. io
TT =10,000 8,/kg
o
o) .
u
C
10100 1000
Adsorbent Concentra t ion ,m, (mg/1)
Supernatant
I? Nonexchangeable Partition Coefficient
10
-O-
IT - 5200 H/kg
o
• « • AAli A > • • « • > «i ft a > 1 » 1 t»i • *
10" 100 1000
Adsorbent Concentration , m, (mg/1)
01
o
c
o
t-l
oj
10"
10
Distilled Water
^Exchangeable Partition Coefficient
a v = 0.624
100
1000
Adsorbent Concentra t ion, m, (mg/
Supernatant
Exchangeable Partition Coefficient
10
v = 0.521
x
100
-1 .
1000
Adsorbent Concent ra tion, m , (mg/1)
Fig. II-2. Nonexchangeable and Exchangeable Partition Coefficient variation with adsorbent concentration
Coo-Jnow Hov <3f-afl nn //SCI. fH B t-•( 1 1 o/l Mat-or1 nnH annor-nat-unf- aa annonno n>>aao
-------
MONTMORILLONITE
Distilled Water
c
(U
ai
o
a
c
o
•H
4J
M
(T)
^5*-
: Nonexchangeable Partition Coefficient
10
10
10'
B a
_n_
4-
T
ir = 3620 Jl/kg
..1
10 100 • 1000
Adsorbent Concent ration,m,(mg/i)
Distilled Water
Exchangeable Partition Coefficient
v = 0.439
-a
10
10 100 1000
Adsorbent Concent ratii on, m, (m'g/i)
10"
10
Supernatant
Nonexchangeable Partition Coefficient
-a—er
2610
10 100 1000
Adsorbent Concentration,!!!, (mg/ 1)
Supernatant
Exchangeable Partition Coefficient
V = 0.557
x
A l^AUl 1 • lfl.AllJ
10
10
Adsorbent Concentration,m,(mg/i)
Fig. II-3.. Nonexchangeable and Exchangeable Partition Coefficient variation with adsorbent concentration,
Montmorillonite. Distilled water and supernatant as aqueous phase.
-------
TABLE II-l
Adsorbent
Saginaw Bay #50
REGRESSION ANALYSES OF ADSORBENT CONCENTRATION EFFECT
Aqueous Phase
Nonexchangeable
Partition Coefficient*
Exchangeable
Partition Coefficient*
irou/kg)
Distilled
Water
Slope (n)
-0.015
(0.039, -0,070)
Intercept (a) Average
(x 10~3) TTQ(Vg)
9.64 10.0
(12.6, 7.33)
TTx(£/kg)
Slope (n)
-1.025
(-0.98, -1.07)
Intercept (a)
(x 10"6)
0.681
(.862, .538)
Average
V
x
0.624
Saginaw Bay //50 Supernatant
0,011 5.83
(0.093, -0.07) (8.72, 3.90)
5.29 -0.952 .410
(-0.90, -1.01) (.534, .315)
0.521
Montmorillonite
Distilled
Water
-0.247
(-0,21, -0.29)
13.6
(.16.9, 10.9)
3.62 -1.04 .541
(-1.01, -1.06) (.635, .461)
0.439
Montmorillonite Supernatant
-0.421
(-0.35, 0.49)
2,12
(3,09, 1.45)
2.61 -0.855 .261
(-0.79, -0.92) (.367, 1.86)
0.557
§
Regressions performed on individual data points rather than the triplicate averages.
*Values in parentheses are regression coefficients ± standard errors of the estimates.
176
-------
the exchangeable partition coefficient relationship are all found to be n =
-1 within 95% confidence limits, whereas for the nonexchangeable partition
coefficients, only the Saginaw Bay sediment yields n = zero within the con-
fidence limits.
Nevertheless it is a useful approximation to assume that the nonexchange-
able partition coefficient, TT , is constant with respect to sediment concen-
tration, m. The inverse relationship between TT and m, i.e. :
•*v
TT = v m"1 (II-3)
X A
defines v , a dimensionless distribution coefficient for the exchangeable com-
*»
ponent. Hence a consistent description of the exchangeable and nonexchangeable
partition coefficient - sediment concentration relationships requires two para-
meters only: a nonexchangeable partition coefficient: ir and an exchangeable
distribution coefficient: v .
X
The utility of this assumption is that it provides a concise description
of the behavior of the variation of adsorption, IT , and desorption, IT , par-
Si Q
tition coefficients as functions of adsorbent concentration. It has been
shown in Section I that there are relationships which express IT and IT in
terms of n and TT,. These equations can be derived as follows. For TT , it
a d M x'
follows from eq. (II-l) that:
The relationship between c and c, follows from the mass balance relationship:
cL Q
mr = c_,, and the fact that c_, = c, + m r. so that:
a Td To d d
mrr
Using these equations, solving for IT and TT in terms of TT and IT , and using
ad ox
eq. (II-3) for n yields:
X
.„ . *o+-i (II-6)
177
-------
IT , = IT (1 + —) + — (H-7)
d o v ' m
x
The curves in fig. (II-l) for IT and ir versus m are these relationships using
3 u
constant TT and v represented by lines in fig. (II-2) and (II-3), and the
O X
average values given in Table 1-1. The extent of the goodness of fit re-
flects the assumption of constant TT : the fit is better for Saginaw Bay
sediment than for montmorillonite, as is expected, since the assumption of
constant TT is more appropriate for the former data.
o
D. Effect of Sediment Characteristics
It has been proposed in the previous section that the adsorption and de-
sorption behavior of HCB can be described in terms of two parameters, IT and
v , which are essentially independent of the sediment concentration. However,
^v
they may be functions of the types of sediment used. To investigate these
relationships the Saginaw Bay sediment isotherms generated for sediment samples
from seven locations can be used (Section VI, Part A).
The results of the adsorption-desorption isotherm experiments are shown
in fig. II-4. The straight lines are linear isotherms for the average adsorp-
tion and desorption partition coefficients, which are listed in Table II-2.
Although there is some tendency for the desorption isotherm to be nonlinear the
fits are reasonable representations of the data. Nonreversible behavior is
found in all cases but is quite small for Station //69 in contrast to the other
stations. Note that the Station #69 particulate concentrations are an order
of magnitude smaller and the dissolved concentrations are an order of magni-
tude larger than the other stations. In addition the adsorbent concentration
used is much larger (m = 20,000 mg/£) than for the rest of the adsorbents
(m = 1100 mg/2.). This was necessary in order that appreciable particulate
concentrations resulted for this sediment.
The variation in adsorption partition coefficient has been correlated to
organic carbon content of the sediment (Karickhoff et al., 1979) and to the
sediment surface area (Hiraizumi et al., 1979). Similar correlation studies
have been made for the adsorption and desorption partition coefficients found
in the present studies (Section VI).
178
-------
s
0)
0)
oo
60
§
5 2.
c
0>
o
o
o
Q ADSORPTION
DESORPT10N
10,0
g
03
C!
I
I STATION 69
•m=20,OOOmg/R.
T.o 10.0 1,0
Aqueous Concentration, c, (ng/Jl)
10.0
Fig. II-4 Adsorption and Desorption Isotherms for Saginaw Bay Stations and
Montmorillonite. Aqueous phase is Distilled Water except for
Montmorillonite (2mM NaHCO-) m = 1100 mg/£ except for Station
#69 (m = 20.000 mg/fc)
179
-------
TABLE II-2
EXPERIMENTAL DATA FOR PARTITION COEFFICIENTS
Sediment
Saginaw Bay
19
31
43
50
t
I 53
69
Saginaw River
Montmorillonite
Volatile
Solids
(%
15.
9.
9.
7.
8.
0.
9.
0.
.)
0
9
3
6
7
3
6
0
Specific
Area
(m2
17.
17.
15.
12.
7.
0.
8.
12.
/g)
0
8
9
8
0
2
4
6
Adsorbent
Concentration
(mg/A)
1100
1100
1100
1100
1100
22000
1100
1100
14
12
10
7
11
0
9
2
TT *
a
U/g)
.8 (15)
.3 (18)
•7 (21)
.01(17)
.2(7)
.036(27)
.63(12)
.10(17)
U/g)
30
30
26
20
19
0.
22
7
.1 (18)
.9 (17)
.1 (35)
.2 (32)
.8 (22)
052(25)
.4 (23)
.23(15)
TT *
0
U/g)
14.0 (14)
11.7 (18)
10.1 (21)
6.56(17)
10.1 ( 8)
0.0087(64)
8.99 (12)
1.79 (16)
v *
X
0.915 (44)
0.630 (39)
0.653 (66)
0.496 (52)
1.18 (48)
0.545 (46)
0.702 (43)
0.349 (29)
The numbers in parentheses are the standard errors of the experimental data, in percent.
-------
As suggested above, the most concise description of adsorption and desorp-
tion is in terms of the nonexchangeable partition coefficient, TT , and the
exchangeable distribution coefficient, v . The variation of these coefficients
X
(mean ± standard deviation) as functions of percent volatile solids (% VSS) and
specific surface area (o) as determined by a single point N2-BET isotherm, are
shown in fig. II-5. The variation of nonexchangeable partition coefficient,
TT , with % VSS (fig. II-5a) is fairly regular for the Saginaw Bay stations, but
o
montmorillonite does not conform to the relationship since it has a significant
TT and no volatile solids fraction. The surface area correlation (fig. II-5b)
o
is more erratic and again montmorillonite does not conform.
The variation of exchangeable distribution coefficient, v , with volatile
j^
solids fraction (fig. II-5c) and surface area (fig. II-5d) is not systematic
although there is a slight trend for v to increase with volatile solids frac-
X
tion. The surprising result is that to within approximately a factor of three
the exchangeable distribution coefficient is nearly constant and independent of
sediment properties. The value obtained for the coarse fraction (>75p) of Sta-
tion #69 sediment (v = 0.545) is consistent with the range for the fine frac-
X
tion (<75y) of the other Saginaw Bay Stations (v = 0.496 - 1.18) and for
X
montmorillonite (v = 0.349). This weak variation of the exchangeable distri-
X
bution coefficient as a function of sediment properties contrasts sharply with
the strong variation of the nonexchangeable partition coefficient: whereas the
range of v is 0.349-1.18, the range of TT is 0.036-14.8 (fc/g).
A multiple linear regression analysis of these data, shown in Table II-3,
further illustrates this result. Whereas the regression equation for TT has
a small constant term relative to the contribution of the volatile solids
fraction and surface area, the reverse is true for v . The goodness of fit
X
of the prediction equations are illustrated in fig. II-6. The observed non-
exchangeable partition coefficients are well represented by the linear rela-
tionship (Table II-3) as indicated by the large fraction of the variance re-
2
moved by the regression (R = 0.953) whereas the exchangeable distribution
coefficient is less well represented, although a significant fraction of the
2
variance is removed by the regression (R = 0.66).
Both the nonexchangeable and exchangeable coefficients tend to increase
181
-------
irr
20. 0
15.0
10.0
t
0.
20.0
15.0
10.0
c
r
• 0 Oi \^^
TjL
MONTMORILLONITE ^^\
I iX^S- STATION #69
0 4.0 8.0 12.0 11
% VOLATILE 'SOLIDS
,
1 T
* * I
MONTMORILLONITE
STATION #69 ^ o
1,20
v 0,90
0.60
0.30r
5.0 o
1.50
1.20
0.90
* 0.60
0.30
(70- 5.0 10.0 15.0 20.0 0
Q
I T
. STATION tf69 I
\^ 1 fft
1 T 1
lj-x_J10NTMORILLONITE '
.0 4.0 8.0 12.0 16
% VOLATILE SOLIDS
T
II
1 '
^STATION #69 1 T
i? 1
^.l {
s^"\
MONTMORILLONITE
.0 5.0 10.0 15.0 20
n
SPECIFIC SURFACE AREA (I*T/G)
SPECIFIC SURFACE AREA
Fig. II-5. Variation of Nonexchangeable Partition Coefficient and exchangeable
distribution coefficient with respect to percent volatile solids
and specific surface area.
182
-------
Constant
TABLE II-3
MULTIPLE LINEAR REGRESSION ANALYSIS*
Volatile Solids**
VSS(%)
Surface Area**
o(m /g)
Multiple
Regression Coefficient
.,2
0.219
0.850(0.115)
0.110(0.097)
0.953
0.625
0.0507(0.0163)
-0.028(0.0138)
0.660
CO
*Prediction Equations are:
IT = 0.219 + 0.850 (% VSS) + 0.110 a
o
v =0.625 + 0.0507 (% VSS) - 0.028 a
X
**The numbers in parentheses are the estimated standard errors of the coefficients.
-------
20-,
15-
oo
t=
•a 10,
u
Nonexchangeable
Partition
Coefficient
k*-Montmorillonite
-Station #69
Observed IT
15
2(
•o
0)
o
Exchangeable
Distribution
Coefficient
Observed v
x
Fig. II-6. Comparison of Calculated (using the regression equations) and
observed coefficients.
184
-------
as volatile solids fraction increases and the standard errors of the regression
coefficients are small (14% and 32% respectively). The influence of increasing
surface area is to tend to increase TT , as a result of montmorillonite which
o
shows a significant nonexchangeable partition coefficient with no fraction
volatile solids. However, the standard error of this regression coefficient
is large (88%). In contrast the exchangeable distribution coefficient tends
to decrease as surface area increases. This puzzling result may be spurious
and due to the cross correlation between volatile solids fraction and surface
area. In any case the regression equation is not a dramatic improvement over
the assumption of a constant v . Further experimental information is required
Jv
in order to refine the relationship for v , if indeed they exist.
Jx
E. Implications for Modeling PCS Fate in Natural Waters
The results of these experiments and their analysis in terms of a non-
exchangeable partition coefficient and an exchangeable distribution coeffi-
cient directly impact the formulations used to model the fate of chemicals
which adsorb to suspended and sedimented particles. The conventional assump-
tions are that the adsorption-desorption reaction is reversible and, for a
linear isotherm relationship, that the partition coefficients are constant
with respect to adsorbent concentration. Both of these assumptions have been
shown to be inappropriate approximations of the experimentally observed be-
havior of HCB.
The issue of the impact of the nonexchangeable component on the eventual
fate of HCB is still uncertain since it has been shown that apparently this com-
ponent does eventually desorb at very low aqueous concentration (Section VIII,
Part A). Whether the desorption is complete is uncertain at present.
The sediment concentration effects, however, can have a substantial im-
pact on the computation of the fate of PCB. The transport processes and
kinetic reactions are significantly different for adsorbed (.= particulate)
and dissolved chemical fractions. These are estimated using the relation-
ships for dissolved and particulate fraction :
fd • TT^T
185
-------
mrr
where f = c /c and f = 1 -. f . These equations follow directly from the
d a Ta p d
mass balance equation c_ = c + mr , and the linear isotherm: r = IT c .
Ta a a* a a a
A useful quantity is the ratio of particulate to dissolved fraction:
-3- = m TT (11-10)
rd a
since if the adsorption partition coefficient is independent of the adsorbent
concentration, m, then one would expect that a graph of f /f , versus m would
P d
be a straight line.
It has been shown above, however, that TT is indeed a function of m and
d
that eq (II-6) provides an expression of this variation. The result is that
the ratio of particulate to dissolved fraction should vary as:
f
-r2- = v + m IT (11-11)
f, X O
d
where v and TT are constant with respect to m. Thus at low suspended solids
concentrations the particulate fraction should approach v following eq. (11-11)
X
and not zero, as implied by eq. (11-10).
The experimental adsorption data, presented in this way is shown in
fig. II-7. The straight line is eq. (11-10) using TT = TT , the curved line
Si O
is eq. (11-12) with v =0.5 for all cases and TT as indicated. The marked
X ' O
deviation from straight line behavior is a consequence of the sediment concen-
tration dependent adsorption partition coefficient. The data for quartz and
kaolinite as adsorbents also appear to conform to this relationship, as shown
in fig. II-7.
These data are all laboratory experimental results. The fact that v
X
is approximately independent of adsorbent properties, however, suggests that
field data would also exhibit the same solids dependency if TT is not fluc-
o
tuating too widely. Fig. II-8 illustrates the relationship for logiri f /f ,
10 p d
versus m for Saginaw Bay suspended particulates. The line is a linear re-
186
-------
o
r-f
Saginaw Bay Sta. 50
Distilled Water
TT = 10,000
o
V =0.5
X
eq. II-ll
eq. 11-10 (TT <=IT )
O
•
O
10
100
1000
Saginaw Bay Sta. 50
Supernatant
Tr - 6,000
1 U AJIJA »
10
100
1000
•o
p-
o
•
o
Montmorillonite
Distilled Water
IT
O
•
O
10
100
1000
Montmorillonite
Supernatant
TT = 2,500£/kg
o Kaolinite
*
2 E Distilled Water
f1^ —
TT = 750 £/kg
v - 0.5
x
o
o
O
t t I tllll
Silica
Distilled Water
TT = 400 «./kg
o 10 100 1000
Adsorbent Concentration,ra,(mg/A)
Fig. II-7 Ratio of Particulate to Dissolved fraction of HCB versus
adsorbent concentration.
187
-------
o
UJ
o
ta
in
O
ce
Ul
a.
o
<
a:
li
ID
, 10°
10-1
10
-2
10
-3
4 *> A^
A
*A, * A*
0.0
10.0 20.0
SUSPENDED SOLIDS,M,(MG//)
28.0
Fig. II-8 Ratio of Particulatt co Dissolved fraction of PCS versus suspended
solids concentration for Saginaw Bay. All cruises. Line is re-
gression equation; log "f /f = a + bm; a = -0.532; b = 0.0343.
188 .
-------
gression. Using eq. (11-11) for the particulate to dissolved ratio, and the
approximation: £n (1 + e) = e for e small yields:
(£nwx + m W
The regression slope (0.0343 «7mg) and intercept (-0.532) yields v =
Jt
0.294 and ir = 23.2 £/g. The exchangeable distribution coefficient is at
the lower range of the experimental values (v = 0.35 - 1.2) and the nonex-
J^
changeable partition coefficient is larger than those observed experimentally
(ir = 0.036 - 14.8 £/g) . The latter result suggests that the percent volatile
solids of the suspended particulates in Saginaw Bay is on the order of 20%
(see fig. II-5) which is not unreasonable since a substantial fraction of
the suspended particulate fraction is phytoplankton and detrital organic
matter. Thus it appears that the Saginaw Bay suspended particulate PCB
field data is in reasonable conformity with the experimental results, and,
in particular, exhibits the relationship implied by the exchangeable-nonex-
changeable model of PCB partitioning.
The implication of these results is that the expressions for dissolved
and particulate fractions should be modified. In particular the particulate
fraction, eq. (II-9), becomes:
v + mrr
f '
A comparison of this equation to the conventional expression (eq. (Il-rlO)) is
shown in fig. II-9. Whereas at adsorbent concentrations of less than 10 rag/fc
the conventional expression predicts no significant particulate fraction in
the water column (.f = 0.09), the revised expression, eq. (11-13) predicts
a substantial fraction (f = 0.38). Although this may be compensated for by
suitably increasing the "apparent" partition coefficient, the shapes of the
two curves are quite different. The influence of this modification on detailed
PCB fate calculations in Saginaw Bay is currently under way.
189
-------
l.Or
10 100 1000
Suspended Solids,m,(mg/£)
Fig. II-9 Particulate Fraction versus adsorbent concentration with and
without adsorbent dependent partitioning.
190
-------
F. Discussion and Conclusions
The data presented for HCB adsorption and desorption for various Saginaw
Bay sediments and clay adsorbents clearly indicates that sediment concentra-
tion has a significant effect on the extent of partitioning. The behavior of
the particulate fraction is quite different from that which is expected if
TT is constant.
a
The behavior of both the adsorption, TT , and single desorption, ir ,
a a
partition coefficients as a function of sediment concentration is somewhat
more complicated. They are nearly equal at low adsorbent concentrations
(m = 10 mg/A) and both decrease as m increases. They appear to reach asymp-
totic values in the range of m ** 200 - 1000 mg/£. However, the desorption
partition coefficient varies less markedly than the adsorption partition
coefficient (fig. II-l).
In contrast, the behavior of the partition coefficients for the exchange-
able and nonexchangeable components is quite regular. The former is inversely
proportional to adsorbent concentration and the parameter describing this be-
havior, v , is found to be nearly a constant regardless of adsorbent type or
X
properties. This is a remarkable result and suggests that some ubiquitous
mechanism is the cause for the behavior of the exchangeable component.
In contrast, the nonexchangeable component partition coefficient has been
found to be constant with respect to adsorbent concentration but to vary quite
markedly with adsorbent type. The interplay of these two parameters determines
the extent of the adsorbent concentration effect and the degree of reversibility
observed, i.e., the extent to which IT = TT . Equations (II-6) and (II-7) specify
u cl
the relationships. In particular if the ratio of TT to ir is used as the measure
G 3.
of irreversibility as was done in Section VIII of Part A, then they predict that:
as m
and
as m -*• o (11-15)
191
-------
Hence PCS adsorption-desorption should appear to be quite reversible at low
adsorbent concentrations, IT,/TT •*• 1, and to exhibit moderately nonreversible
d a
characteristics, TT /ir -»• 3, at high adsorbent concentrations. Indeed, this is what
u 3.
was observed in Part A, fig. VIII-4 and 5.
However, if the measure of irreversibility is the difference between TT,
and TT , then eqs. (II-6) and (II-7) predict that:
3.
IT
Tf . - TT = — (11-16)
d a v
x
which is independent of sediment concentration, and so, also, is the extent
of irreversibility. The point is that the more fundamental description of
HCB adsorption and desorption and their behavior as a function of sediment
concentration is in terms of rr and V and that TT and TT, are simply a result
ox ad v }
of the behavior of the exchangeable and nonexchangeable components.
The description of HCB adsorbent concentration effects for both adsorp-
tion and desorption is certainly parsimonious and empirically quite successful.
In addition it describes the behavior of experiments in which both aqueous phase
and adsorbent concentrations are varied together as discussed in the next sec-
tion. The difficulty that remains is to ascribe the results to mechanistic
models. Partition coefficients that decrease as sediment concentration in-
creases suggest that particle-particle interactions are responsible. But why
should the variation be exactly inverse to mass and for the exchangeable com-
ponent, why should V be independent of adsorbent type.
X
Conversely the nonexchangeable partition coefficient appears to be constant
with respect to sediment concentration but a strong function of sediment type.
The mechanism that accounts for this behavior is also unknown at present. Thus
although the description of adsorbent concentration effects in terms of the ex-
changeable and nonexchangeable component behavior is successful, it is not yet
complete and additional experimental and theoretical investigations are required
to determine what mechanisms are responsible for this regular, if puzzling,
behavior.
192
-------
SECTION III
RESUSPENSION AND DILUTION: IMPLICATIONS FOR FATE OF PCB
A. Introduction
The formulation and validation of a desorption model is guided by the use
for which this model is being developed: namely as a portion of the computa-
tion of toxic chemical fate. An important interaction in such models is the
settling and resuspension of the adsorbent particles. Consider the situation
in which particles settle into a region near the sediment-water interface. The
concentration of adsorbent particles will increase in this region. Since the
experimental information indicates that the exchangeable partition coefficient
decreases as adsorbent mass increases, it might be expected that some desorp-
tion from the particles will take place. This mechanism would liberate PCB's
to the dissolved phase and thereby increase the exposure concentration for the
biota.
Conversely, decreases in suspended solids concentrations can occur if in-
fluents, which carry both PCB's and suspended solids, are dispersed in the re-
ceiving water. For example, a tributary with a high concentration of both PCB's
and suspended solids enters a deeper, more quiescent, region of a lake. The
mass dependent partitioning for the exchangeable components would interact to
produce a redistribution of the total quantity of PCB among the adsorbed compo-
nents and the soluble fraction. Both of these situations are of practical sig-
nificance and are discussed below.
B. Resuspension
An experimental design to investigate this mechanism, called a resuspen-
sion experiment, is shown in fig. III-l. Following adsorption equilibrium and
adsorbent separation, a portion of the contaminated aqueous phase is removed.
No new aqueous phase is added. Rather the adsorbent is then resuspended into
the previously contaminated aqueous phase and equilibriated. The only change
has been to increase the concentration of the adsorbent, since it is now re-
•suspended into only a portion of the aqueous phase volume.
193
-------
Shake
Resuspension Experiment
ADSORPTION
Centrifuge
RESUSPENSION
Remove a portion
of the <
aqueous phas '.
\
Shake
tn
rs
"Trs
Centrifuge
rs
DESORPTION
Remove all
aqueous
phase
Add uncontaminated
aqueous phase
Shake
Centrifuge^
Fig.. III-l. Resuspension Experimental Procedure
194
-------
If the exchangeable-nonexchangeable model of desorption is valid, then
it is expected that the exchangeable partition coefficient should decrease
since it is inversely proportional to adsorbent mass (refer to fig. II-2).
This should cause an increase of dissolved chemical in the aqueous phase.
Hence, the first prediction is that the aqueous phase concentration at resus-
pension equilibrium should increase.
This is a somewhat surprising prediction since during resuspension equi-
librium the only change that has occurred is in the number of particles per unit
volume. The aqueous phase is the same as that which resulted from adsorption
equilibrium. Thus each particle is exposed to the same aqueous phase concentra-
tion as it was previously exposed to, and with which it was in equilibrium. The
only difference is that the particle-particle interaction is increased: each
particle is exposed to more particles than at adsorption equilibria. Accordingly,
one would expect no change if the particle concentration has no effect on this
desorption.
But the sediment concentration experiments indicate that it does have an
effect on the exchangeable component partition coefficient. Hence the resus-
pension experiment is a direct check on the validity of the sediment concentra-
topm effects and the formulation of the desorption model.
Three experiments were performed; for the first two experiments, the sed-
iment concentration was increased four-fold from the adsorption sediment concen-
tration of (.1) m = 55 mg/£ to the resuspension sediment concentration of m =
3 ITS
220 mg/x.; and (.2) from m = 220 mg/2, to m = 11.00 mg/Jl. For ^he third experi-
fit t S
ment a twenty-fold change was examined: (3) from m = 55 mg/£ to m = 1100 mg/£.
ci r s
Saginaw Bay #50 sediment was employed. The results are shown in Table III-l where
each replicate is listed. In all cases the aqueous concentration at resuspension
equilibrium, c , is larger than at adsorption equilibrium, c , in conformity
r s a
with the rather unexpected model prediction.
The experiment is a clear confirmation of the sediment concentration on
partitioning that was observed in the conventional adsorption-desorption
experiments at different solids concentrations. What is unexpected is that
by simply resuspending the solids into a reduced volume of supernatant but
with the same HCB concentration as at adsorption equilibrium, causes any
195
-------
Experiment
No.
(1)
(2)
(3)
m
TABLE III-l
Resuspension Experiment - Saginaw Bay //50
Adsorption Resuspension
m
VD
a
«/*)
55
55
55
220
220
220
55
55
55
a
(ng/4)
41.8
37.1
38.1
22.1
23.3
21.5
29.8
29.3
27.6
a
(ng/g)
692.
647.
663.
300.
269.
259.
497.
480.
511.
rs
(ng/i)
220
220
220
880
880
880
1100
1100
1100
rs
(ng/A)
104.
58.3
70.9
32.2
42.3
27.5
84.8
74.4
63.6
rs
(ng/g)
345.
575.
443.
286.
298.
301.
488.
458.
487.
Dissolved Concentration
Ratio
c /c
rs a
2,
1,
1
1
1
,49
.57
,86
,46
,82
1.28
2.85
2.54
2.30
-------
change at all. The only difference is that the solids concentration has in-
creased. What seems to be occurring is that the particle-particle inter-
actions are increased and that either the quantity of available exchangeable
sites are decreased, causing desorption, or, more likely, that the binding
strength of all the exchangeable sites is decreased by the particle-particle
interactions, causing desorption from all exchangeable sites.
Note that the effect is more pronounced for adsorption at (1) m = 55 mg/H
d.
and resuspension at m = 220 mg/£ for which c /c =2.0 then at (2) m =
T 3 IS 3, fi
220 mg/£ and m = 11.00 mg/X, for which c /c = 1.5. This is due to the fact
rs rs a
that the quantity of the exchangeable component is larger at the lower sediment
concentration m = 55 mg/X, than at m = 220 mg/X,.. To see this, consider the
Q. Si
fraction of adsorbed HCB that is exchangeable:
r ir c v m v
x _ x a _ x x
r TT c ^ -1 v -Unir
a a a TT + v m x o
O X
so that for TT = 10,000 £/kg and v = 0.5, r /r = 0.5 at m =55 mg/fc, whereas
O X X 3 3
at m = 220 mg/fc, r /r - 0.2.
a x a
The largest change in dissolved HCB occurs for the twenty-fold increase in
sediment concentration (3) m = 55 mg/£ and m = 1100 mg/£ for which c /c -
o ITS ITS 3.
2.6, which is the result of the initially large fraction of exchangeable compo-
nent present and the large change in sediment concentration.
The quantitative predictions are derived as follows. Consider the ratio
of the particulate fraction of total HCB:
fp = mra/cTa
and the dissolved fraction:
That is:
fd -
f mr
_£
mir
d a
197
-------
where the second equality is what is predicted from the exchangeable-nonexchange-
able model. As shown in section II, fig. II-7 the varying sediment concentration
experiments are in agreement with this equation.
Now consider the effect of resuspension. The aqueous concentration at re-
suspension equilibrium c , is increased, c > c , due to increased sediment
r n rs' rs a'
concentration m > m . Hence additional nonexchangeable HCB should adsorb.
ITS 3
This was verified by the consecutive adsorption experiment (fig. 1-7). Thus
the total HCB concentration at resuspension equilibrium, c , is given by:
CTrs = crs * "r.rr.
' Crs + mrs(ro + V
since r is the sum of the exchangeable and nonexchangeable components. Since
rs .
the aqueous concentration increased, the nonexchangeable component concentration
should be given by the nonexchangeable isotherm: r = ir c . The exchangeable
o o rs
component is always determined by the reversible exchangeable isotherm:
r = IT c . Therefore eq. (III-6) becomes:
x x rs M
C™ = c + m (TT 4- ir )c
Trs rs rs o x rs
and since the exchangeable partition coefficient is mass dependent: ir = m v ,
the final formula is:
^, = c (1 + v + m IT ) (III-7)
Trs rs x rs o v
The dissolved fraction is:
fd - c- = l + vm u
Trs x rs o
the fraction particulate is:
and the ratio is:
f = 1 - f , (HI-9)
P a
f
•
198
-------
which is the same form as the participate to dissolved ratio at adsorption
equilibrium (eq. III-4) except that it is evaluated at the sediment concen-
tration at resuspension, m . Figure III-2 present's the results for both
L S
the adsorption and resuspension ratios, which also contains the desorption
model prediction for this experiment. The ratio of the fraction of particu-
late to dissolved chemical is predicted to increase as sediment mass is in-
creased. As shown the experimental results are in conformity with the quan-
titative prediction. The data, although somewhat scattered, is consistent
with v =0.5 and rr = 10,000 £/kg, which are in fairly close agreement to
the results of the adsorption-desorption experiments at varying sediment con^
centrations (fig. U-2, it = 10,000 fc/kg and \>^ = 0.624).
C. Component Behavior at Resuspension Equilibrium
Since the desorption model is based upon the distinct behavior of the
exchangeable and nonexchangeable components, the experimental design includes
a final desorption step (fig. II-l). Its purpose is analogous to the desorp-
tion phase of the previous experimental designs: namely to allow the deter-
mination of the concentration of exchangeable and nonexchangeable components
actually on the particles at resuspension equilibrium. The increased aqueous
phase concentration at resuspension equilibrium should interact with the par-
ticles. Since the nonexchangeable partition coefficient is constant with
respect to sediment concentrations (fig. II-2)f this increased aqueous con-
centration should cause the nonexchangeable component concentration to in-
crease via increased adsorption until it is in equilibrium with the increased
aqueous phase. These quantities, expressed as partition coefficients, are
compared to the model predictions in fig. III-3. The lines represent the
theoretical behavior inferred from the sediment concentration experiments.
The results of the desorption following the resuspension experiments are
shown as are parallel adsorption-desorption experiments. Although quite
scattered, the component behavior is in rough conformity with expectations:
the observed exchangeable partition coefficients do decrease, and the ob-
served nonexchangeable partition coefficient are approximately constant. The
data are given in the Appendix.
199
-------
f
_
f
Adsorption (a)
Resuspension (+)
Sediment Concentration (mg/A)
Fig. III-2. Resuspension Experiment - Model Predictions and Observations
200
-------
X
(4/kg)
10
,. Exchangeable Partition Coefficient
10
10"
10
4 '
Adsorption (o)
Resuspension (+)
10
10 -
10
IT
O
(a/kg)
10
10H
1Q
10
5 Nonexchangeable Partition Coefficient
Q TT = 10 a/kg
a ° •
fc
10
10
10
3 '
10
Adsorption (a)
Resuspension (+)
Adsorbent Mass (mg/£)
Fig. III-3. Exchangeable and Nonexchangeable Component Behavior
at Adsorption and Resuspension Equilibria
201
-------
However the agreement is not sufficient to firmly establish that component
behavior is in absolute accord with model predictions. More experiments of
this type would be required to firmly establish the detailed validity of compo-
nent behavior.
D. Dilution Experiment
The dilution experiment is, in a sense the reverse of the resuspension
experiment, in that the concentration of sediment is reduced by adding uncon-
taminated aqueous phase to the vessel after adsorption equilibrium is achieved,
This procedure is sometimes used to construct adsorption isotherms without an
intervening solids separation step. It has been suggested that a possible
cause of the nonsingularity of adsorption and desorption isotherm is the
solids separation step, which involves centrifuging and subsequent resus-
pension into adsorbate-free aqueous phase. This mechanical procedure can
conceivably alter the particle aggregations so that the available sites and,
therefore, the observed desorption partition coefficient increases.
The dilution isotherm avoids the solids separation step. As shown in
fig. III-4: following adsorption equilibrium, a fraction of the mixed
aqueous-solids phase is removed and replaced by adsorbate-adsorbent-free
aqueous phase. This step lowers the aqueous phase adsorbate concentration
and causes desorption to occur. Unfortunately the dilution step also lowers
the solids concentration so that the analysis of this experiment must account
for that effect as well. If sediment concentrations affect the partitioning
then the dilution "isotherm" is not a direct experimental determination of
the desorption isotherm because of the sediment concentration reduction which
occurs at dilution. However if the sediment concentration effect has been
quantified, as it has for the model of adsorption and desorption proposed in
this report, then it is possible to account for this effect.
An analysis of the dilution experiment can be made using the predicted
ratio of particulate to dissolved fractions at adsorption and dilution equil-
ibrium in the same way as the resuspension experiment. At adsorption equil-
ibrium, the ratio of f = 1 - f,, to the dissolved fraction: f , = c /cm is
p d d a Ta
202
-------
Dilution Experiment
Not J,
Centrifuged
m
ADSORPTION
c
Centrifuge
DILUTION
Remove some
aqueous ^
& sediment
Add uncon-
_taminated
aqueous phase
Shake
Centrifuge
DESORPTION
Remove all
aqueous *—
phase
Add uncon-
taminated
aqueous
phase
Shake
Centrifuge"
Fig. III-A. Experimental Procedure for Dilution Experiment
203
-------
given by: (eq. II-l).
f
-^- = v + m IT (III-ll)
f , x a o
d
The sediment concentration effect accounts for the difference between this
expression and the conventional expression; f /f, = m TT ,
p d a a
Consider the situation at dilution equilibrium. The total concentration
is given by:
where c, .. and r, . are the aqueous and particulate concentrations and m, is the
U Ar Q Xf Q X
sediment concentration at dilution equilibrium. The particulate concentration
is made up of the sum of the nonexchangeable, r , and exchangeable, r
Ou X*
components, that is:
The exchangeable component has reacted to the lowered aqueous concentration
caused by the dilution and it is given by the exchangeable isotherm:
- Vd*
However, the nonexchangeable component does not react, since it is nonexchange
able. Rather it remains at the concentration that is determined by the non-
exchangeable isotherm at adsorption equilibrium:
r ., = r = -n c (111-15)
odi o o a
Hence the particulate concentration at dilution equilibrium is, from eqs. (III
13, 14 and 15):
r,n = TT c + TT c,. (111-16)
dl, o a x di
Using this expression in eq. (111-12) yields:
204
-------
and since m IT = v from the exchangeable-partition coefficient - sediment
Q J6 X X
concentration relationship, the result is that:
and the dissolved fraction at dilution equilibrium is given by:
Q
f
d c 1 + v + m..ir (c /cjo)
Tdi x dt ov a d£
and finally, the particulate to dissolved fraction ratio is;
(m-20)
d dfc
Note the difference between this formula, which applies at dilution equilibrium,
and eq. (III-ll) which applies at adsorption equilibrium. The ratio is larger
for dilution equilibrium due to the presence of the factor: c /c, ., which is due
,H QX>
to the assumption that the nonexchangeable component concentration is determined
by the aqueous concentration at adsorption equilibrium: r = ir c and that it
o o a
remains constant at dilution equilibrium and does not decrease in response to
the decreased aqueous concentration that is: c,. < c , whereas: r ..= r (eq.
dx a odx o
111-15} .
The experimental data is compared to the (incorrect) expression for the
particulate to dissolved ratio that applies only at adsorption equilibrium:
f
-3- = v + rnir (Adsorption) (111-21)
I - X O
d
in fig. III-5. Note that the ratio found for the dilution experiment is sig-
nificantly larger than that predicted from the adsorption sediment concentra-
tion effect alone. This suggests that indeed dilution equilibration is not
simply another technique to produce adsorption isotherms even if the sediment
concentration effect is taken into account. In fact the nonreversibility
persists and the particulate fraction is larger than expected. It is not
linearly related to sediment concentration as is predicted by the adsorption
equilibrium expression (eq. 111-21).
205
-------
U-l
Saginaw Bay #50
m - 220 mg/Jl
v = 0.5
x
IT = 11000 £/kg
; *
4-
+
+
50
L /f, - V + rnTT
p d x o
D Adsorption
+ Dilution
100 150 200 250
C
o
4J
O
01
f-l
O
CO
CO
•H
Q
01
•u
O
-H
JJ
0.
Saginaw Bay #50
20
m = 1100 mg/i
a ..
0 200 400 600 ,800 1000 1200
3.
Montmorillonite
m = 1100 mg/£
Q.
v = 0.5
TTX - 1.725 Jl/kg
o
7UD
fe'OO • Ht)0 - TfiUD - 1200
Adsorbent Concentration, tn, (mg/£)
Fig. III-5. Comparison of Observed Particulate to Dissolved -Fraction
Ratio-Adsorbent Mass Relation Without Correction due to
the Dilution Equilibration
206
-------
By contrast, if the nonreversibility is taken into account, then the
particulate-dissolved concentration ratio is given by:
-r- = \> + mrr (--) (Adsorption and (111-22)
d X ° Cd£ Dilution)
This expression predicts a straight line if the ratio is plotted against sedi-
ment concentration, m, modified by the ratio of aqueous concentration of ad-
sorption equilibrium, c , to aqueous concentration at dilution equilibrium,
o
c,0. Since the former concentration is not measured in the dilution experi-
d X*
ment, it is estimated from the total concentration at adsorption equilibrium,
c , which is measured and the adsorption partition coefficient, ir , which is
la a
available from the parallel adsorption experiment, as described previously.
The results are shown in fig. III-6 where t /f are plotted against me /c...
DO 3 u X>
The straight line corresponds to eq. (111-22), the prediction of the exchange-
able-nonexchangeable model. The values of it and v (from which IT = TT +
e ox a o
v m is also calculated) are shown in the figure.
x a
The value of the exchangeable distribution coefficient is v = 0.5 in all
X
cases, in conformity with the experiments for which sediment concentration was
varied. The nonexchangeable partition coefficient, IT , is chosen to conform
with the parallel adsorption experiment.
Note that the dilution experimental data are in conformity with the pre-
diction except at the largest dilution, corresponding to the lowest aqueous
concentrations. This suggests that, although the exchangeable-nonexchangeable
model is certainly more successful than the model which accounts for only the
adsorption sediment concentration (compare fig. III-5 to fig. 111-^6), it is
not fully descriptive of the behavior of the experiments at large dilutions.
This failure was also noted at low aqueous concentrations in the analysis of
consecutive desorption isotherms, where for m = 220 mg/£, it appeared that
3.
eventually it may be possible to desorb the nonexchangeable component (fig. VIII
-12 of Part A). This point is discussed below in more detail.
E. Component Behavior at Dilution Equilibrium
The utility of the division of adsorbed HCB into exchangeable and non-
exchangeable components depends upon the applicability of the isotherms
207
-------
•o 2
M
•*»
a.
ra = 220 mg/i
s
v = 0.5
x
TI = ]l,OQO?,/kg
f /f = V + mir c /c 0
pa x o a dX,
29
15
10
50 1(>0 150 200 250
'm "Ca/CdJl
Saginaw Bay #50
m = 1100 mg/i
o.
V = 0.5
x
TI = 15,000 £/kg
Adsorption '-'
Dilution ' ' "*"
200 400 600 800 1000 1200
Montmorillonite
m = 1100 mg/£
3.
v = 0.5
x
TT = 1725
0 200 400 600 800 1000 1200
m Ca/CdS,
Fig. II1-6. Comparison of Observed Particulate to Dissolved Fraction Ratio
to Adsorben^ Mass, modified by c /c as predicted from the
3. ux<
Exchangeable-Npnexchangeable Model
208
-------
r = IT c and mr = v c to all situations that may be encountered during
o a a . x x
simulations of mixing phenomena in natural waters. In particular the dilu-
tion experiment can be thought of as the experimental analog of the mixing
that would occur if a tributary stream carrying a high HCB and suspended
solids concentration enters a relatively uncontaminated, suspended solids
free receiving water. The question is: are the isotherms capable of pre-
dicting the results. More specifically, is each component behaving as ex-
pected. The analysis of the ratio of particulate to dissolved fractions
suggest that it is. However a more detailed answer to this question involves
a direct measurement of the component concentrations at dilution equilibrium.
This can be determined if a desorption step follows dilution step in the ex-
periment. The final desorption step generates the desorption points (c•, r ),
which when extrapolated, can be used to calculate the exchangeable and nonex-
changeable components at dilution equilibrium in a way that is directly anal-
ogous to the method employed in the conventional adsorption-desorption experi-
ment with the exception that the dilution concentrations replace the adsorption
concentrations.
That is the nonexchangeable particulate concentration is estimated
using:
-------
DO
c
•o
o
•4
lOV
10
Saginaw Bay //50
m = 220 mg/S,
a
10J
10
c
o
•H
rt
M
4J
0)
O
C
o
PQ
O
sc
0)
.0
rt
a)
00
C
e
o
T3
C
3
O
03
6
•H
01
CO
10
10
10
10^
10
10
Saginaw Bay #50
m = 1100 ng/S,
a
1 H
10
Montmorillonite
m = 1100 mg/£
. a
10
IT^
D Adsorption - Desorption, r , c
+ Dilution - Desorption, r , c „
od ax,
* « • **•
* ««««•«
10" 10A 10'
Aqueous Concentration, c , c . (ng/£)
Fi,g. III-7. Nonexchangeable Component Concentration at Adsorption and
Dilution Equilibrium, estimated using a subsequent desorption,
versus aqueous HCB concentration at adsorption and dilution.
equilibrium respectively
210
-------
60
c*
•a
X
e
(0
oo
B
cfl
CJ
X
w
10-
10
10"
Saginaw bay //50
m = 220 mg/fc
ci
^ v
•» X
= 0.66
D Adsorption-Desorption.TT
•*• Dilution-Desorption.TT
xd
10
10 10 10-
Saginaw Bay #50
m = 1100 mg/£
a
10
10
" 10J
Montmorillonite
m = 1100 mg/8,
a
10
-1
10* 102 103 ' 10^
Adsorbent Concentration, m , m (mg/£)
Fig. III-8. Exchangeable Partition Coefficient at Adsorption and Dilution
Equilibrium Estimated from the Subsequent Desorption, versus
Adsorbent Concentration, m and m . respectively
.
211
-------
(Saginaw Bay, m = 220 mg/£) the nonexchangeable concentration appears to de-
a
crease with decreasing aqueous concentrations in violation of the assumption
of nonexchangeability whereas for the higher initial sediment concentrations,
the nonexchangeable hypothesis is roughly supported.
By contrast, the experimentally estimated exchangeable partition coeffi-
cients appear to conform to an inverse relationship to sediment concentration
as shown in fig. III-8 although the scatter in the data is substantial. The
lines have a slope of minus one in conformity with the relationship: rr ^ m
X
and v ^ 0.5 except for the scattered data at m = 1100 mg/JZ, for Saginaw Bay.
x a
Hence, while the exchangeable component behavior appears to be in agree-
ment with the model hypothesis, the nonexchangeable component appears to be
more exchangeable at lower sediment concentrations than assumed in the model
formulation.
F. Application to Receiving Water Fate Models
The use of models for the computation of toxic chemicals exposure levels
in natural waters is currently an important component of rational toxic chemical
regulation and control. The development of EXAMS by EPA (Baughman and Lassiter,
1978), models for PCB, radionuclides and toxic heavy metals in the Great Lakes
by our group at Manhattan College, and other investigations, are currently in
progress. These models have a common approach in dealing with the adsorption-
desorption reaction.
The mass balance equations are written in terms of total chemical, c_, with
the transport and kinetic terms suitably modified with the fraction of chemical
in the dissolved, f,, or particulate, f , form depending on whether the terms in
d p
the equation apply to particulate or dissolved phases. As an example, consider
a two layer segmentation representing the water column of depth HI, and an active
sediment layer of depth H^. These interact via vertical mixing of the aqueous .-
phases, with mass transfer coefficient K ; and settling and resuspension of the
particulate phases, with velocities w and w respectively. The governing mass
3 ITS
balance equations are:
Hl IT = KL(fd2°T2 - fdlCTl} - WafplCTl + Wrsfp2CT2 + W
212
-------
H2 -3T - VfdlCTl - fd2cT2) + WafplCTl ~ wrsfp2cT2
where c , and c are the total chemical concentrations in the water column and
-L -L -L +* r\
sediment layers respectively, and W is the input mass loading rate (M/L /T) .
Note the central role of the dissolved (f ... and f ,_) and particulate (f , and
dl dZ pi
f „) fractions, in the water column and sediment segments respectively. They
P2
directly affect the magnitudes of the mass transfer coefficients and therefore
the fate of the chemical. A more complex fate computation would include terms
for outflow, the various appropriate decay mechanisms, and sedimentation losses.
However, the principle is still the same. Once the total concentration is com-
puted, the dissolved water column concentration is given by: c,. = f, c , with
analagous expressions for the particulate concentration. Again the particulate
and dissolved fractions play a central role, and these fractions are a direct
result of the adsorption-desorption model employed.
For completely reversible adsorption-desorption and a linear isotherm, the
dissolved and particulate fractions are given by:
fd -
f = Y-— CHI-28)
p 1 + nnr
where ir is the reversible partition coefficient and m is the adsorbent concen-
trations. The subscripts 1 and 2 in equations (111-25 and 111-26) refer to
evaluating these fractions using the appropriate adsorbent concentration in
segments 1 and 2.
For the HCB exchangeable-nonexchangeable component model of adsorption-
desorption, these fractions depend upon the model parameters: TT , the parti-
tion coefficient for the nonexchangeable component; and v , the distribution
• 3C
coefficient for the exchangeable component; and the maximum dissolved aqueous
concentration to which the particle has been exposed: c ,. This latter con-
md
centration sets the magnitude of the nonexchangeable component. It is shown
in the previous section that the dissolved and particulate fractions are given
213
-------
by Che expressions:
f . = T-r - . t - 7— r (111-29)
d 1 4- v + mir (c ,/c.)
x o md d
v + tmr (c ,/c,)
f = -_* - ° md ^ (Hl-30)
p 1 + v + mil (c ,/c.) '
r x o md d
where c is the current dissolved aqueous phase concentration. The particu-
late fraction as a function of adsorbent solids concentration, m, is shown in
fig. III-9. The conventional expression, assuming reversible behavior is
also shown. There is a significant difference between the conventional re-
versible formulation and the exchangeable-nonexchangeable model. The partic-
ulate fraction is always a substantial portion of the total chemical concen-
tration, even at low suspended solids concentrations that are characteristic
of most receiving waters (.10-100 mg/£). This suggests that fate computations
using the exchangeable-nonexchangeable model will give quite different results
which emphasize the importance of particle transport.
214
-------
The Effect of Nonreversible Desorption
o
o
0)
3
O
M
(8
1.0'
0.3
0.6
0.4
0.2
md/c
= 100
Exchange.ible-Non ex changeable
Desorption Model • •
Reversible Desorption - - - -
>tn - 1 — i i » n i MI i i . i i i tin . i t i i
10 100
Adsorbent Mnss.m,(mg/£)
1000
10,000
Fig. III-9. Particulate fraction versus adsorbent mass for
reversible desorption, eq. (111-28); and exchangeable-
nonexchangeable desorption, eq. (111-30).
IT = 10 Jl/kg, V =0.5
O X
215
-------
REFERENCES
Baughman, G.L., Lassiter, R.R. Prediction of Environmental Pollutant Con-
centration in Estimating the Hazard of Chemical Substances to Aquatic
Life. Cairns, J., Dickson, K.L., Maki, A.W. eds. ASTM STP 657. 1978,
pp. 35-70.
Bowman, B.T., Sans, W.W. Adsorption of Parathion, Fenitroghion, Methyl
Parathion, Aminoparathion and Paraoxon by Na, Ca, and Fe Monttnorillonite
Suspension. Soil Soc. Am. J., Vol. 41, pp. 514-519. 1977.
Bowman, B.T. Method of Repeated Additions for Generating Pesticide Adsorption-
Desorption Isotherm Data. Can. J. Soil Sci., Vol. 59, pp. 435-437. Nov. 1979.
Connolly, J.P. The Effect of Sediment Suspension on Adsorption and Fate of
Kepone. Ph.D. Thesis, University of Texas, Austin, Texas. 208 p. 1980.
Felsot, A., Dahm, P.A. Sorption of Organophosphorus and Carbamate Insecti-
cides by Soil, Agricul. Food Chem., Vol. 27, pp. 557-563. 1979.
Hague, R. ed. Dynamics, Exposure and Hazard Assessment of Toxic Chemicals.
Ann Arbor Science Publ. Inc., Ann Arbor, Mich. 48106. 1980.
Hiraizumi, Y.M., Takahashi, M., Nishimura, H. "Adsorption of Polychlorinated
Biphenyl onto Sea Bed Sediment, Marine Plankton, and other Adsorbing Agents."
Environ. Sci. Tech., Vol. 13(5), p. 580. 1979.
Huang, Ju-C, Liao, C. Adsorption of Pesticides by Clay Minerals. J. Sanit.
Engr. Div., ASCE, Vol. 96, SA5, pp. 1057-1078. 1970.
Karickhoff, S.W., Brown, D.S., Scott, T.A. Sorption of Hydrophobic Pollutants
on Natural Sediments. Water Research, Vol. 13, p. 241. 1979.
Kishk, F.M., Abu-Sharar, T.M., Bakry, N.M., Abou-Donia, M.B. Sorption-
Desorption Characteristics of Methyl Parathion by Clays. Arch. Environ.
Contain. Toxicol., Vol. 8, pp. 637-645. 1979.
Koskinen, W.C., O'Connor, G.A., Cheng, H.H. Characterization of Hystersis
in the Desorption of 2,4,5-T in Soils. Soil Sci. Soc. Am. J., Vol. 43,
pp. 871-874. 1979.
Lotse, E.G., Graetz, D.A., Cheaters, G., Lee, G.B., Newland, L.W. Lindane
Adsorption by Lake Sediments. Environ. Sci. Technol., Vol. 2, No. 5,
p. 353. 1968.
Marking, L.L., Kimberle, R.A., eds. Aquatic Toxicology Proc. Second Annual
Symposium on Aquatic Toxicology. ASTM STP 667. 1979.
Mayer, F.L., Hamelink, J.L., eds. Aquatic Toxicology and Hazard Evaluation.
Proc. First Annual Symposium on Aquatic Toxicology. ASTM STP 634. 1916
Race St. Phil. Pa. 19103. 1977.
216
-------
REFERENCES (cont'd)
O'Connor, D.J., Connolly, J.P. The Effect of Concentration of Adsorbing
Solids on the Partition Coefficient". Water Research, 14, p. 1517. 1980.
O'Connor, D.J., Schnoor, J.L. Distribution of Organic Chemicals and Heavy
Metals in Lakes and Reservoirs, in press.
Peck, D.E., Corwin, D.L., Farmer, W.J. Adsorption-Desorption of Diuron by
Freshwater Sediments. J. Environ. Qual., Vol. 9, pp. 101-106. 1980,
Pierce, R.H., Jr., Olney, C.E., Felbeck, G.T., Jr. pp'-DDT Adsorption to
Suspended Particulate Matter in Sea Water. Geochim. Cosmochim. Acta,
Vol. 38, pp. 1061-1073. 1974.
Rao, P.S.C., Davidson, J.M. Estimation of Pesticide Retention and Trans-
formation Parameters Required in Nonpoint Source Pollution Models in
Environmental Impact of Nonpoint Source Pollution, ed. M.R. Overcash,
J.M. Davidson. Ann Arbor Science Publishers, Inc., pp. 23-67. 1980.
Rao, P.S.C., Davidson, J.M. Nonsingularity of Pesticide Adsorption-Desorption
Isotherms: Effect of Experimental Method, submitted to J. Environ. Qual.
1980.
Savage, K.E., Wauchope, R.D. Fluometuron Adsorption-Desorption Equilibria
in Soil. Weed Sci., Vol. 22, pp. 106-110. 1974.
Swanson, R.A., Dutt, G.R. Chemical and Physical Processes that Affect Atrazine
Distribution in Soil Systems. Soil Sci. Soc. Am. Proc., Vol. 37, pp. 872-876.
1973.
Thomann, R.V., Di Toro, D,M. Preliminary Model of Recovery of the Great Lakes
Following Toxic Substances Pollution Abatement, Workshop on Scientific Basis
for Dealing with Chemical Toxic Substances in the Great Lakes. Great Lakes
Basin Commission, Ann Arbor, Mich. 1979. Submitted, J. Great Lakes Res.
1980.
van Genuchten, M.Th., Davidson, J.M., Wierenga, P.J. An Evaluation of Kinetic
and Equilibrium Equations for the Prediction of Pesticide Movement Through
Porous Media. Soil Sci. Soc. Amer. Proc., Vol. 38, pp. 29-35. 1974.
van Genuchten, M.Th. Wierenga, P.J., O'Connor, G.A. Mass Transfer Studies
in Sorbing Porous Media; III. Experimental Evaluation with 2,4,5-T. Soil
Sci. Soc. Am. J., Vol. 41, pp. 278-285. 1977.
Wildish, D.J., Metcalfe, C.D., Akagi, H.M., McLeese, D.W. Flux of Aroclor
1254 Between Estuarine Sediments and Water. Bull, Environ. Contain. Toxicol.
Vol. 24, pp. 20-26. 1980.
217
-------
APPENDIX
-------
DATA APPENDIX
Table
No. Sediment
KINETIC STUDY
1 Montmorillonite
2 Sag Bay Sta.//50
3 Montraorillonite
4 Sag Bay Sta.//50
ISOTHERM
5 Sag Bay Sta.#50
6 Sag Bay Sta.//50
7 Sag Bay Sta.//50
8 Sag Bay Sta.//50
9 Sag Bay Sta.//50
10 Sag Bay Sta.//50
11 Sag Bay Sta.//50
12 Sag Bay Sta.#50
13 Sag Bay Sta.#50
14 Sag Bay Sta.//50
15 Sag Bay Sta.#50
16 Montmorillonite
17 Montmorillonite
18 Montmorillonite
19 Montraorillonite
20 Montmorillonite
21 Kaolinite
SOLUTION COMPOSITION
22 Montmorillonite
23 Montmorillonite
24 Montmorillonite
Aqueous
Phase
Supernatant
Supernatant
Supernatant
Supernatant
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Supernatant
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
NaHCO Buffer
NaHCO^ Buffer
Dist. Water
Nad
HC1 & NaOH
CaCln
2
ISOTHERM-SEDIMENT COMPOSITION
25 Sag Bay Sta.M3
26 Sag Bay Sta.//50
27 Montmorillonite
28 Sag Bay Sta.//69
29 Sag Bay Sta.f/19
30 Saginaw River
31 Sag Bay Sta.//53
32 Sag Bay Sta.//31
Dist. Water
Dist. Water
NaHCO Buffer
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Dist. Water
Sedi
Cone.
(mg/A)
200
200
200
200
50-55
55
55
200
220
1000
1100
1100
1100
1100
1100
50
200
1000
50
1100
1000
200
200
200
1100
1100
1100
20000
1100
1100
1100
1100
Time of
Ads.
(hours)
0.75-24
0.25-24
2
2
2-3
48
240
4
3
2-4
3
24
120
3
3
2-3
2-3
2
3
3
2.0
4
4
4
3
3
3
3
3
3
3
3
Time of
Des.
(hours)
0.25-24
0.25-6
1.5-3
48
240
3
1.5
3
72
144
1.5-3
1.5-3
1.5-3
3
3
1.5
3
3
3
3
3
3
3
-------
Table
No.
Sediment
Aqueous
Phase
Sedi.
Cone.
(rag/I)
Time of
Ads.
(hours)
Time of
Des.
(hours)
SEDIMENT CONCENTRATION
33 Montmorillonite
34 Montmorillonite
35 Sag Bay Sta.//50
36 Sag Bay Sta.//50
37 Montmorillonite
38 Montmorillonite
39 Silica
Dist. Water
Supernatant
Dist. Water
Supernatant
Dist. Water
Phosphate Buffer
Dist. Water
2
2
2
2
24
2-4
3
1-3
1.5-5
1.5
1.5-5
24
1.5-4
3
RESUSPENSION EXPERIMENT
40 Sag Bay Sta.#50
41 Sag Bay Sta.//50
42 Sag Bay Sta.//50
DILUTION EXPERIMENT
Dist. Water 55-220
Dist. Water 220-880
Dist. Water 55-1100
43 Montmorillonite
44 Sag Bay Sta.#50
45 Sag Bay Sta.//50
NaHCO Buffer 1100
Dist. Water 1100
Dist. Water 220
-------
TABLE 1. KINETIC STUDY
Sediment = Montmorillonite
Mass = 200 mg/2 Time of Adsorption
= 0.75-24 hr.
Aqueous Phase = Supern.atant
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta »'hr>
Md (f-i3--'1>
Td Chr>
Ci
CTa Cr.3/l>
Ca (n9'-'l >
R a v TI 3 •*' 3 •'
R x a ( TI 3 / 3 )
CTd (ng.-l)
Cd
Rd
R O "C fi 3 •'' 3 -^
Glass
MB Er. <':>
6229.66
1.00
2.68
7.28
—
288.88
8.75
—
—
56.48
43.17
24.26
119.56
--
--
--
—
—
—
21.54
-18.77
6229.00
1.66
2.66
7.25
—
286.36
2.86
__
—
54.76
48.74
22.04
133.51
••• UK
--
16.18
-8.04
6229.00
1.06
2.68
7.38
—
238.88
5.58
—
—
54.76
45.99
22.38
113.66
—
—
—
—
—
__
•» •»
-—
6229.00
1.00
2.00
7.30
—
286.00
7.75
__
—
54.76
44.62
26.85
122.84
—
--
—
—
—
—
69.89
-5,75
7039.00
1.00
2.00
7.20
--
200.00
18.06
—
—
54.76
43.27
16.93
131.69
*•» «•»
—
-.-
—
—
—
24.53
-16.51
6229.ee
i.ee
2.0e
7.38
--
200.08
0.25
—
—
54.76
53.70
27.57
130.65
—
—
—
—
—
--
15.55
0.92
-------
TABLE 1. (cont'd) KINETIC STUDY
Sediment = Montmorillonite
Mass = 200 rag/X, Time of Adsorption
= 0.75-24 hr.
Aqueous Phase = Supernatant
Date
Expt. Type
Aq. Phase
PH
Ionic
Ha
Ta f.hr>
Md <".M3''1 >
Td (hr:>
Ci 9/1 >
CTa
Ca (n3/l >
Ra
R x a ( n 3 / 3 >
CTd
Cd v'ns/1 >
Rd
Rxd (ri3--'3>
Ro (Tk3/9>
Glass (pd>
MB Er.
6229.60
1.00
2.86
7.25
—
289.66
3.68
—
—
56.48
49.63
22.09
137.72
—
—
—
—
—
•^ *••
73.73
1.67
6269.08
1.30
2.63
7.20
—
206.08
6.66
--
—
55.85
54.29
26.68
171.67
-_
—
--
—
—
— •
11.86
-6.68
6279.66
1.66
2.06
7.35
—
286.80
24.88
—
—
54.21
44.72
27.68
88.22
--
— .
^ •»
—
—
—
2.52
-17.04
6119.00
1.00
2.06
6.70
—
260.68
4.80
-_.
—
55. '30
48.30
18.85
147.23
. —
--
—
•
—
—
14.18
-10. 11
6119.00
2.00
2.00
6.66
—
200.60
2.66
200.00
1.50
55.30
45.56
20.26
126.53
77.50
25.28
8.77
82.56
33.54
49.02
9.73
-15.85
-------
TABLE 2. KINETIC STUDY
Sediment = Saginaw
Mass = 200 mg/£
Bay Station //50
Time of Adsorption = 0.
Aqueous
25-24 hr.
Phase = Supernatant
Date
Expt. Type
Aq. Phase
PH
lOTiiC
Ma
Ta i'hr>
Md u-13/1)
Td (hr>
Ci
CTa
R a £. ft 3 •'' 3 ^
Rxa (ris/g)
CTd (ri3''l>
Cd (n3-'1>
D *l / «. — ' -- s,
KCf V Hyr 3 ••
Rxd
Ro (ns-'S^
Glass
MB Er. <'-:>
7039.00
1.00
2.00
7.05
—
200.00
18.00
—
-.
54.76
49.38
14.55
174. 14
—
--
—
—
—
—
13.37
-7.38
6229.00
1.00
2.00
6.75
—
209.00
0.25
—
—
54.76
53.63
16. 61
185.06
—
—
—
__
--
—
12.55
0.23
€229.00
1.00
2.00
6.75
—
200.00
2.00
—
—
54.76
51 . 66
13.73
189.65
—
—
—
—
—
—
13.70
-3. 15
6229.90
1.08
2.00
6.75
—
soo.ee
7.75
--
—
54.76
56.24
10.48
228.80
—
-_
—
--
—
--
33. 17
3.77
6229.08
1.68
2.08
6.75
—
280.88
0.75
--
—
56.48
54.27
15.22
195.24
--
__
— -
--
--
—
17.21
-0.73
6229.88
1.88
2.88
6.75
— —
288.88
3.88
—
• --
56.48
52.84
12.42
282.89
—
— -
--
-—
__.
—
11.53
-4.27
-------
TABLE 2. (cont'd) KINETIC STUDY
Sediment = Saginaw
Mass = 200 mg/£
Bay Station //50
Time of Adsorption = 0.
Aqueous Phase = Supernatant
25-24 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (H9-''1>
Ta
Md (H3/D
Td
Ci
CTa
Ca
» ^ ^
K Q i. Ti 3 ' 3 ••*
Rxa »' Ti3/g)
CTd
r- j f — ~ » i \
L CI *. fi 3 •' 1 ••*
Rd (ri3--'3>
Rxd (ri3/3>
R 0 '. Ti 9 •'' 3 ')
Glass
MB Er.
6279.00
1.00
2.60
6.80
—
260.00
24.00
— -
—
54.21
52.98
19.70
166.40
--
—
.-
—
--
—
10.20
-0.40
6309.00
1.00
2.06
6.75
—
200.00
5.00
—
—
58.04
54.49
11.59
214.47
—
—
—
—
—
—
25.97
-1.65
6309.00
1.00
2.00
6.75
—
260.00
6.00
—
58.04
52.48
14.13
191.71
••**
—
—
—
—
.--
12.87
-7.37
-------
TABLE 3. KINETIC STUDY
Sediment = Montmorillonite Aqueous Phase = Supernatant
Mass = 200 rag/I Time of Adsorption = 2 hr. Time of Desorption = 0.25-24 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (ng/1 >
Ta
Hd
Td (hr)
Ci (Ti3/l )
CTa
Ca
Ra
Rxa
CTd
Cd (B3/l>
Rd
Ro
Glass (p3>
MB Er. 0;>
7039.
2.
2.
7.
--
288.
2.
260.
24.
47.
—
^ ••»
—
—
18.
5.
61.
•» •»
--
8.
—
00
00
00
40
88
88
00
00
09
31
95
81
26
7039.
2.
2.
7.
—
208.
b» •
200.
IS.
54.
—
—
—
—
19.
7.
68.
— —
9.
—
00
83
08
48
08
88
88
08
76
18
88
18
44
6289.
2.
2.
7.
—
200.
2.
280.
5.
55.
—
—
—
—
38.
9.
143.
__
18.
-—
83
00
08
85
88
68
08
80
85
22
68
11
cc
6269
2
2
8
-._
288
2
288
8
55
--
--
--
— —
19
6
69
_ _
5
_..
.08
.08
.88
.58
.80
.08
.88
.25
.85
.95
.85
.49
.86
6269.
2.
2.
8.
__
288.
2.
280.
2.
55.
— — •
--
--.
-.-
28.
7.
66.
*» •» '
6.
—• ••>
00
00
00
50
00
08
88
88
85
65
31
72
72
6279.00
2.00
2.00
8.50
__
200.00
2.00
280.00
0.75
54.21
«_
_._
_._
__
15.72
4.63
55.48
II
11.39
am M
-------
TABLE 3.(cont'd) KINETIC STUDY
Sediment = Montmorillonite
Mass = 200 mg/£ Time of
Aqueous Phase = Supernatant
Adsorption = 2 hr. Time of Desorption = 0.25-24 hr.
Date
Expt. Type
fiq. Phase
pH
Ionic
Ma < ns'.-' 1 >
Ta
Hd
Td
Ci
CTa
Ca
Ra
Rxa vrioj/£j>
CTd
Cd
Rd
Rxd
Ro
Glass
MB Er. <.':>
6279.80
2.03
2.80
7.90
—
208.33
2.06
200.00
4.00
54.21
—
—
*•» ••>
-
17.92
5.39
62.62
--.
•
9.85
--
6119.00
2.33
2.90
6.60
—
280.00
2.00
200.00
1.50
55.30
45.56
20.26
126.53
77.50
25.28
8.77
82.56
33.54
49.02
9.73
-15.85
-------
TABLE A. KINETIC STUDY
Sediment = Saginaw
Mass = 200 mg/£
Bay Station #50
Time of Adsorption = 2
Aqueous Phase = Supernatant
hr. Time of Desorption = 0.25-6 hr.
Date
Expt. Type
Act. Phase
PH
Ionic
Ma
Ta (hr>
Md u-13/1 >
Id
Ci (n3-'l>
CTa
Ca Cr,g/l>
R a ( Ti 3 ••* 3 ••*
Rxa
CTd (Ti3/l>
/*• i •" _• i ^
Cd M"i9-' 1 .•
Rd <:ri3-''3>
Rxd
Ro «r.3''3>
Glass
MB Er.
-------
TABLE 4.(cont'd) KINETIC STUDY
Sediment = Saginaw
Mass = 200 mg/2.
Bay Station #50 Aqueous Phase = Supernatant
Time of Adsorption = 2 hr. Time of Desorption = 0.25-6 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta
Hd Cf-I3''1 >
Td
Ci
CTa
Ca (r.3/l>
R a ( TI 3 / 3 )
Rxa
CTd
Cd
Rd
R O *. fi 3 •'' 3 ^
Glass Cpg>
MB Er. O:>
6279.09
2.00
2.60
6.75
—
260.00
2.00
200.03
4.00
54.21
—
— -
—
—
30.00
5.08
124.5?
__.
7.69
--
-------
. TABLE. 5. ISOTHERM
Sediment = Saginaw Bay Station 50
Mass = 50-55 mg/£ Time of Adsorption = 2-3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1.5-3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
CTd
4189.08
2.00
1.08
5.6Q
-—
se.ee
2.00
se.ee
1.58
7.3?
6.72
2.89
76.69
46.13
3.se
1.26
50.?2
20.16
30.56
2.46
-5.60
6679.ee
2.00
i.ee
5.69
— -
se.ee
2. ee
se.ee
1.50
—
41.22
20.ee
424.36
304.67
20.86
8.44
248.31
128.62
119.69
9.51
--
5239.ee
2.00
i.ee
5.56
— -
56.66
2. oe
50.ee
i.se
18.67
16.24
7.89
167.17
93.32
8.35
2.92
168.45
34.66
73.86
14.38
-2.14
5286.00
3.00
1.00
•"•*
— —
55.00
3.00
50.60
3.00
56.40
51.95
31.86
365.27
232.45
22.32
11.49
216.66
83.84
132.82
17.69
-11.96
5286.00
3.00
1.00
M •
•*"*
55.00
3.00
56.00
3.06
75.28
66.15
39.35
487.16
353.89
29. 61
15.41
271.87
138.66
133.27
27.88
-14.51
5286.66
3.66
1.00
_»— .
^ *•
55.88
3.80
50.00
3.08
112.80
100.42
54.49
835. 13
652.66
44.99
22.43
451.17
268.79
182.47
33.66
-10,86
-------
TABLE 5. ISOTHERM (cont'd)
Sediment = Saginaw.
Mass = 50-55 mg/£
Bay Station
50 Aqueous Phase = Distilled Water
Time of Adsorption = 2-3 hr. Time of Desorption = 1.5-3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ha (ng^1>
Ta
Td (hr)
Ci (Tig/1 >
CTa Ug/l>
Ca (ng/1)
Ra (ng/g)
Rxa (ng'g)
CTd (ng/l>
Cd (ng/l>
Rd
Rxd
Glass
HB Er.
saee.ee
3.00
i.ee
— —
-—
55.90
3.80
59.08
3.88
150.40
146.76
72.46
1241.89
392.57
64.61
28.80
704.09
354.77
349.32
20.26
-6.33
5280.09
3.00
1.00
— —
— —
55.00
3.00
58.90
3.00
188.90
178.62
94.49
1529.75
1138.58
76.88
35.77
822.18
431.01
391.17
27.25
-3.75
-------
TABLE 6. ISOTHERM
Sediment = Saginaw Bay Station 50
Mass = 55 rag/ Si Time of Adsorption = 48 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (M3''l )
Ta (hr)
Md (rig/1)
Td (hr>
Ci (rig/ 1)
CTa
Ca (ns/1 >
Ra (Tig/g)
Rxa (ri3/g>
CTd (rig/1 >
Cd (ng/1>
Rd (Tig/9>
Rxd (ris/3>
Ro (Ti3/s>
Glass (pg>
MB Er. (*>
3280.00
3.00
1.00
--
—
55.00
. 48.80
50.00
48.00
9.49
8.6?
5.26
61.99
-8.75
5.13
1.73
67.86
-2.88
70.74
—
' —
3280.00
3.00
1.00
--
—
55.00
48. 09
50.09
48.90
28.47
23.3?
13.59
177.74
36.68
9.78
2.40
147.54
6.48
141.06
—
—
3280.00
3.09
1.00
—
—
55.00
48.90
50 . 00
48.00
47.46
44.98
22.11
399.52
197.50
20.46
4.71
314.92
22.99
292.02
—
—
Aqueous Phase = Distilled Water
Time of Desorption = 48 hr .
3280.90
3. 09
1.00
— —
-—
55.00
48.09
50. 00
43. 09
75.93
68.41
32.82
647.04
171.91
33.83
7.98
516.94
41.81
475. 13
--
-.. .
3280.99
3.00
1.09
— —
__
55.09
48. 00
50.00
48.00
297. 1?
299.28
111.81
1772.22
98.19
193.21
18.69
1699.45
16.42
1674.93
—
--
428e.ee
3.00
i.ee
~~
——
55.99
48.99
59.99
48.99
93.63
84.26
35.59
884.89
445.39
39.58
19.83
574.99
135.58
439.41
— —
— -
-------
TABLE 6. ISOTHERM (cont'd)
Sediment = Saginaw Bay Station 50 Aqueous Phase = Distilled Water
Mass = 55 mg/X. Time of Adsorption = 48 hr. Time of Desorption = 48 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (M3/1 >
Ta
Md
Td
Ci Cng/l )
CTa
Ra (ng''3>
Rxa Cng/3>
CTd 3''1 )
Cd (ng/l)
Rd
Rxd (ng/3>
Ro g/g>
Glass
MB Er. <*>
4280.00
3.00
1.00
--
— —
55.00
48.00
50.00
48.00
124.85
86.49
39.16
860.58
320.23
43.76
11.88
637.51
97.16
540.36
--
—
4280.00
3.00
1.00
.- —
— —
55.00
48.00
50.00
48.00
156.06
106.07
48.31
1050.06
404.37
52.68
14.38
766.06
120.36
645.69
__
— -
4280.00
3.00
1.00
— —
••••
55.00
48.00
50.00
48.00
187.27
143.51
65.57
1417.16
407.77
67.04
12.64
1087.98
78.59
1009.39
—
—
-------
TABLE 7. ISOTHERM
Sediment = Saginaw Bay Station
Mass = 55 mg/Jl
50 Aqueous Phase = Distilled Water
Time of Adsorption = 240 hr. Time of Desorption = 240 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (wg/1)
Ta (hr)
Md (ng/1 )
Td
Ci
Ra
Rxa (ng/g>
CTd
Cd
Rd
Rxd
Ro
MB Er. <*>
4248.80
3.00
1.00
—
—
55.00
240.00
50.00
240.00
10.04
9.25
4.69
82.97
76.45
2.45
1.17
25.55
19.04
6.52
—
--
4240.00
3.00
1.00
—
—
55.00
240.00
50.80
240.00
10.04
8.62
5.26
61.06
30.22
2.65
0.86
35.77
4.93
30.84
--
—
4240.00
3.00
1.00
—
—
55.00
240.06
50.00
240.00
50. 19
39.97
22. 18
323.57
78.84
16.66
3.76
258.09
13.37
244.72
• —
--
4240.60
3.00
1.00
—
—
55.00
240.88
50.00
240.00
50. 19
47.82
26.92
379.96
221.68
12.63
3.34
185.81
27.50
158.31
—
— .
4240.00
3.00
1.00
—
—
55.00
240.00
50.00
240.00
50.19
29.02
12.59
298.68
141.27
12.23
2.79
188.73
31.33
157.40
—
—
4340.00
3.00
1.88
--
—
55.00
240.89
50.00
240.00
80.31
31.85
18.71
238.94
-39.69
18.43
5.04
267.95
-10.69
278.63
—
—
-------
TABLE 7. ISOTHERM (cont'd)
Sediment = Saginaw Bay Station 50 Aqueous Phase = Distilled Water
Mass = 55 rng/J. Time of Adsorption = 240 hr. Time of Desorption = 240 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta (hr>
Md
Ci
CTa (ng/1>
Ca
Ra
Rxa
CTd
Rxd (Tig/g)
Ro (ng/g)
4240.00
3.00
1.00
"***
•"•^
55.00
240.00
50.00
240.00
80.31
54.76
29.93
451.33
220.30
17.39
4.27
262.47
31.43
231.04
4240.00
3.00
1.00
'""" •
55.00
240.00
50.00
240.00
80.31
19.80
8.29
209.41
-14.42
13.32
2.34
219.76
-4.07
223.82
Glass
MB Er.
-------
TABLE 8. ISOTHERM
Sediment = Saginaw-Bay Station 50
Mass = 200 mg/fc Time of Adsorption = 4 hr.
Aqueous Phase = Distilled Water
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Md
Td
Ci Cng/1 >
CTa
Ca
Ra
Rxa
CTd (ng/l>
Cd
Rd (ngx'g>
Rxd (ng/g)
Ro
Glass (pg>
MB Er. CJO
6079.00
1.00
1.00
6.80
.
200.00
4.00
—
--
--
65.92
17.38
242.71
—
—
— .
—
—
--
28.60
--
2289.08
1.00
1.00
6.98
—
200.88
4.08
—
—
43.81
45.17
11.42
168.73
—
—
—
—
—
—
10.34
5.47
3019.88
1.00
1.00
6.90
—
200.00
4.00
—
—
195.30
198.81
67. 14
658.35
—
M* «•
--
52.39
4.48
3029.00
1.00
1. 00
6.98
— -
200. 00
4.00
—
—
97.65
90.75
16.98
368.87
--
--
--
--
—
—
28.43
-4. 15
3879.88
1.08
1.00
6.90
-.-.
208.80
4.08
—
--
17.70
15.61
2.95
63.29
—
—
--
—
—
—
2.14
-18.65
3879.86
1.80
1.88
6.98
— —
288.88
4.08
—
—
88.52
75.81
17.77
298.23
— _
.--
--
-—
-.-
— -
11.28
-13.89
-------
TABLE 8. ISOTHERM (cont'd)
. Sediment = Saginaw Bay Station 50
Mass = 200 mg/Jt Time of Adsorption = 4 hr.
Aqueous
Phase = Distilled Water
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta (hr>
Md
Td
Ci
CTa <. ng/1 >
Ca (ng'l >
Ra
Rxa
CTd Cng/1 >
Cd (ng/M >
Rd
Rxd (ng/g)
Ro
Glass
MB Er. O:>
3879.00
1.00
1.00
6.90
--
200.00
4.00
—
—
141.64
124.51
24.02
582.43
—
—
—
_-
—
'
17.61
-10.85
3089.00
1.00
1 . 00
6.90
—
200.00
4.00
—
—
47.09
49.42
10.16
196.27
—
—
—
—
--
—
10.54
7. 18
3089.00
1.00
1.00
6.90
—
200.00
4.00
—
—
94.18
92.39
20.25
360.69
—
—
—
—
—
—
19.40
0. 16
3269.00
1.00
1.00
• —
—
200.00
4.00
—
—
29.39
24.84
4.65
100.94
—
-- .
—
--
—
—
8.86
-12.46
1040.00
1.00
1.00
.
— •
200.00
3.00
—
—
30.12
27.39
5.79
107.55
--.
—
—
—
—
--
—
—
-------
TABLE 9. ISOTHERM
Sediment = Saginaw Bay Station 50
Mass = 220 mg/£ Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Mn (nqS 1 )
1 1 ^A > I • ^J 9 f
Ta
Md (ng/1 )
i i *« » i • ^j * *
T d ( h r* j>
1 V4 . 1 1 • r
Ci ( TIC!/ 1 )
A * « 1 23 ' •
CTa (ng/D
Co ( nci/ 1 )
^^ ^A > ii ^y 9v
Ra
Rxa
Cd Cng/1)
Rd (ng/cj)
Rxd
Ro (ng/g)
Gi ass t poi )
f %• «^ ^7 • ^r ^^ w
MB Er.
7269.99
3.00
1.00
7.08
220.00
3.00
198.00
3.00
17. 16
17.97
4.93
59.26
21.24
12.18
2.51
48.83
10.81
38.02
4.96
5.05
7269.99
3.90
1.90
7.98
229.90
3.00
198.00
3.00
51.47
52.52
11.66
185.76
54.48
36.09
5.25
155.80
24.52
131.28
6.62
4.66
7269.90
3.99
7.95
220.00
3.90
198.00
3.00
102.94
194.31
28.59
344.19
71.63
65.89
7.97
292.53
19.97
272.56
12.96
4.69
7319.09
3.90
1.90
•» ••
229.90
3.00
229.00
3.00
31.76
30.68
8.66
100. 12
37.77
19.39
2.85
74.77
12.42
62.34
5.88
7.06
7319.99
3.99
1.99
*• ^»
229.09
3.09
229.09
3.00
79.48
77.37
21.65
253.28
72.03
52.07
7.04
204.67
23.43
181.25
14.12
3.83
7319.99
3f\ f\
. 09
1.99
229.99
^A ^K 4^
3.99
229.99
3.09
127.94
137.47
38.99
447.62
296.80
71.89
8.69
286.99
46.97
249.82
13.38
39.26
-------
TABLE 9. ISOTHERM (cont'd)
Sediment = Saginaw Bay Station 50
Mass = 220 mg/J, Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma (MS/))
Ta
Md
Cfc
Ra
Cd
Rd (ng/g>
Rxd (ng/g)
Ro
Glass
MB Er. (V.>
5278.09
3.00
1.00
—
—
220.00
3.80
198.00
3.00
98,56
86.36
25.96
274.54
30.09
63.83
12.55
258.99
14.55
244.45
18.26
-20.14
5270.80
3.00
1.00
— .
—
220.00
3.00
198.08
3.08
164.27
138.56
38.78
453.56
141.94
97.65
20.84
387.91
76.29
311.62
61.91
-16.66
5270.00
3.00
1.00
—
—
220.00
3.00
198.00
3.00
229.98
207.45
60.17
669.46
93.68
141.80
21.25
608.86
33.08
575.78
59.53
-11.23
5270.09
3.09
1.00
— —
—
220.00
3.90
198.00
3.08
262.83
245.58
68.52
804.81
218.95
160.01
26.96
672.00
86. 14
585.86
32.51
-5.58
5270.00
3.00
1.00
-—
—
220.00
3.00
198.00
3.80
295.69
264.61
56.71
945.02
333.05
196.04
34.62
815.28
203.31
611.97
58.97
-11.54
-------
TABLE 10. ISOTHERM
Sediment = Saginaw Bay Station 50
Mass = 1000 mg/£ Time of Adsorption = 2-4 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1.5 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta
Td
Ci (ns/1 >
CTa
Ca (ti3/1>
Ra
Rxa Cri3/3^
CTd
Cd (ns/l)
Rd
Rxd (ns/s)
Ro
Glass
MB Er. C'.>
2289.
1.
1.
7.
—
1000.
4.
__
— —
43.
43.
5.
37.
—
--
--
—
—
--
6.
0.
80
99
00
30
00
00
81
26
37
90
91
34
1970.
1.
1.
—
1000.
3.
--
-_
16.
13.
1.
11.
—
—
—
—
—
--
—
—
00
00
00
00
00
15
01
11
91
1079.
1.
1.
—
—
1000.
3.
—
—
53.
44.
3.
41.
—
—
—
—
—
—
--
00
00
00
00
00
84
54
46
08
1970.
1.
1.
—
— -
1000.
3.
—
--
86.
73.
4.
68.
—
--
—
—
. —
—
—
—
09
00
00
09
00
15
21
92
30
1940.
1.
1.
_-
——
1000.
3.
—
—
30.
26.
2.
24.
—
-.-.
—
—
—
—
—
-—
09
00
09
00
09
12
58
49
09
4119.88
2.09
1.98
6.99
<•»«•
1000.09
2.00
1000.00
1.50
19.17
18.53
1.96
16.56
1.26
16.56
0.77
15.80
0.49
15.31
3.97
-1.25
-------
TABLE 10. ISOTHERM (cont'd)
Sediment = Saginaw
Mass = 1000 mg/fc
Bay Station
50 Aqueous Phase = Distilled Water
Time of Adsorption = 2-4 hr. Time of Desorption = 1.5 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma Cng/1>
Ta
Hd (ng/1 >
Td
CTa Cng/1>
Ca
Ra (ng/g)
Rxa
CTd (ng/1 >
Cd (ng/1>
Rd (r.g/g>
Rxd
Ro
Glass
MB Er. C/.>
4119.00
2.00
1.00
6.90
--
1000. 00
2.00
1000.00
1.50
76.66
76.26
7.89
68.37
3.09
68.34
2.20
66.1.5
0.86
65.29
4 . 88
0. 12
4119.00
2.00
1.00
6.90
— —
1000.00
2.00
1000.00
1.50
153.32
151.45
13.13
138.32
6.22
138.32
4.22
134.10
2.00
132.11
12.85
-0.38
-------
TABLE 11. ISOTHERM
Sediment = Saginaw Bay Station
Mass = 1100 mg/fc
50
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
jj
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (ng/1 )
Ta (hr)
Md (rig/I)
Td (hr)
Ci (ng/1)
CTa (ng/l)
C a ( n g / I >
Ra (ng/g>
Rxa (ng/g)
CTd (ng/l)
Cd (ng/l)
Rd (ng/g>
Rxd (ng/g)
Ro (ng/g)
Glass (pg)
MB Er.
-------
TABLE 11. ISOTHERM (cont'd)
Sediment = Saginaw Bay Station 50 Aqueous Phase = Distilled Water
Mass = 1100 mg/£ Time of Adsorption = 3 hr. Time of Desorption =3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma (rig/I)
Ta (hr>
Md (rig/ 1 >
Td (hr)
Ci (tig/I)
CTa (T.g/l>
Ca
Rxa (ng/g>
CTd
Cd
Rd
Rxd
Ro (ng/g>
Glass (pg>
MB Er. (*>
10167.08
3.00
1.00
—
—
11-00.88
3.80
990.00
3.00
30.66
27.34
3.30
21.85
-1.18
23.51
1.10
22.64
-0.39
23.03
1.66
-16.40
leies.ee
3.00
1.08
*• *•»
— •
1188.80
3.80
998.00
3*80
61.33
56.95
6.32
46.62
-15.15
57.51
2.22
55.85
-5.33
61.18
5.21
-25.78
iei09.ee
3.80
1.00
—
—
1100.00
3.00
990.00
3.00
122.66
127.42
12.55
104.43
50.87
70.65
3.52
67.81
14.25
53.56
11.35
31.50
iei29.ee
3.ee
1.09
'. —
1100.09
3.80
990.80
3.08
15.33
14.18
1.75
11.30
8.43
11.37
0.49
10.99
0.12
10.88
1.31
-7.84
iei29.ee
3.00
1.00
mm Mb
--
1100.00
3.00
990.00
3.00
30.66
35.10
3.16
29.04
15.87
17.50
0.75
16.92
3.76
13.16
13.01
55.39
iei29.ee
3.00
1.90
--
1100.80
3.00
990.80
3.09
61.33
56.08
6.59
44.99
8.38
40.08
1.70
38.77
2.17
36.61
11.65
0.61
-------
TABLE 11. ISOTHERM (cont'd)
Sediment = Saginaw Bay Station
Mass = 1100 mg/X,
50
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
I on i i
Ma (wg/l>
Ta (hr>
Md (rig/I)
Td (hr>
Ci Cng/1 >
CTa <*g/l>
Ca
Ra (ng/g>
Rxa
CTd
Cd (ng/1 >
Rd (tig/g)
Rxd (ng/g>
Ro
MB Er. <*>
10129.00
3.00
1.00
—
—
1130.30
3.00
990.00
3.00
122.66
112.97
14.21
89.78
21.10
75.10
2.88
72.95
4.27
68.67
19.16
4.90
10179.00
3.00
1.00
— —
— —
1103.33
3.38
998.80
3.00
16.61
11.60
1.83.
8.89
1. 18
8.78
0.78
8.16
0.45
7.71
— —
— -
10179.00
3.00
1.00
• «
— •*
1103.00
3.00
993.30
3.00
33.22
24.14
3.07
19.16
8.55
15.18
1.25
14.08
3.47
10.61
-—
——
10179.00
3.00
1.00
** ••
• «•
1133.03
3.03
993.03
3. 00
66.44
53.73
6.01
43.38
23.36
31.80
2.14
29.96
7.43
22.52
MM
*• «•
10179.09
.3.00
1.00
MM flM
1133.33
3.30
998.83
3.80
132.88
111.86
12.09
90.69
17.84
83. 13
3.31
77.89
4.24
73.65
•M •»
mm •»
-------
TABLE 12. ISOTHERM
Sediment = Saginaw
Mass = 1100 mg/il
Bay Station
50
Time of Adsorption = 24 hr.
Aqueous
Phase = Distilled Water
Date
Expt. Type
Aa. Phase
pH
Ionic
Ma
Ta
Md (rig/I)
Td (hr)
Ci
CTa
Ca
Ra
Rxa
CTd
Cd
Rd
Rxd
Ro ( ng/g )
Glass (pg>
MB Er.
11289.00
1.00
1.33
--
—
1100.00
24.00
—
--
15.15
14, 11
0.94
11,97
—
—
—
--
—
—
—
-._
11289.03
1.00
1.00
—
—
1100.00
24.38
—
—
33.30
28.28
1.68
24.11
--
.
mm MB
_-
• -
--
11289.30
1.83
1.88
—
—
1189.38
24.83
—
—
63.68
53.81
3.37
45.86
—
—
—
—
—
—
—
—
11289.60
1.00
1.03
—
-—
1108.00
24.00
—
—
98.90
87.95
5.19
75.24
—
—
--
--
--
— —
--.
--.
11289.08
1. 30
1.03
—
-—
1180.08
24.88
— —
--
121.28
96.96
7.35
81.46
— -
--
--
—
— —
--
'
-------
TABLE 13. ISOTHERM
Sediment = Saginaw
Mass = 1100 rog/S,
Bay Station
50
Time of Adsorption = 120 hr.
Aqueous Phase = Supernatant
Date
Expt. Type
Aa. Phase
pH
Ionic
Ha (ng.-'O
Ta (hr>
Md (N3/1 >
Td (hr>
Ci
CTa
Ra (ng/g)
Rxa
Ro
Glass
MB Er. <*>
12169.60
1.00
2.60
7.35
—
1100.00
128.00
• —
—
15.15
13.14
0.89
11.14
—
—
—
—
--
--
--
--
12169.00
1.00
2.00
7.45
-—
1100. 00
120.00
•^ •••
—
30.30
25.87
1.45
22.20
—
.
—
—
—
—
—
—
12169.66
1.00
2.00
7.45
—
1 160.00
120.00
.
—
45.45
39.41
1.90
34.09
—
—
—
— •
—
—
--
12109.00
1.00
2.06
7.40
--
1100.00
126.00
--
—
75.75
62.21
3.63
53.26
--
--
-_
— —
-_
• _-
_«
.»
12189.00
1.00
2.00
7.35
— —
1100.00
120.00
--
— -
121.20
130.57
6.29
112.98
--
--.
_~
-.—
— _
_..
_-
....
-------
TABLE 14. ISOTHERM
Sediment = Saginaw
Mass = 1100 mg/H
Bay Station #50
Time of Adsorption = 3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 72 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta
Hd < MOJ- 1 >
Td
Ci (T.9/1)
CTa
Ca (ri3/l>
Ra (Ti3/£j>
Rxa (ri3''3>
CTd Cr.3/1 >
Cd
Rd
Rxd (Ti3>3>
R.o (ri3''cj>
Glass
MB Er. <*;>
iei29.ee
3.90
1.90
—
^v •*
1100.66
3. so
936.60
72.6C
15.33
15.11
. 1.35
11.96
6.67
12.32
6.53
11.91
6.02
11.89
2.45
-2.94
16129.66
3.66
1.60
_~
—
1106.66
3.00
996.06
72 . 60
15.33
13.73
1.62
11.06
1.27
10.48
6.47
16.16
6.37
9.73
0.36
-7.25
10129.00
3.66
1.66
—
-------
TABLE 14.(cont'd) ISOTHERM
Sediment = Saginaw
Mass = 1100 mg/£
Bay Station #50
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 72 hr.
Date
Expt. Type
Aci. Phase
pH
Ionic
Ma O-icjxl)
Ta i'hr>
Md <.M3/1>
Td (hr>
Ci (rig/I >
CTa
C a < n 3 x i >
Ra
R */. a ( TI 3 s 3 >
CTd (Ti3-''l>
Cd
Rd
Rxd
Ro
Glass
MB Er. <5j>
10129.06
3.00
1.66
—
—
1180.00
3.00
998.00
7 A. 00
61.33
63.96
6.41
52.32
1 1 .80
44.39
1.51
43.31
2.79
40.52
4.69
17.13
16129.68
3.68
1.88
—
--
1180.00
3.00
398.88
72.00
61.33
47.31
7.32
36.36
9.04
32.28
2.32
36.18
2.86
27.32
72.72
-4.81
10129.88
3.60
1.88
— —
•W IB
1168.00
3. 88
990.00
la. 08
122.66
Hi. 14
17.83
84.82
18.27
71.77
2. 92
69.54
2.99
66.55
8.54
1.26
18129.06
3.08
1.08
**M.
— ..
1166.00
3.08
998.00
ia.08
122.66
115.72
12.41
93.92
21.72
77.81
2.32
76.25
4.06
72.28
7.06
7.29
10129.00
3.00
1.60
— —
«i •-•
1108.08
3.68
990.08
ia.00
122.66
112. 11
12.98
90. 12
23.43
75.84
3.52
73.65
6.36
66.69
116.51
11.80
-------
TABLE 15 ^ISOTHERM,
Sediment = Saginaw Bay Station #50
Mass = 1100 mg/2. Time of Adsorption
= 3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 144 hr.
Date
Expt. Type
Aq. Phase
PH
I 0 Ti I C
Ha
Ta (hr>
Hd Cng/1)
Td
."S * •* * 1 ^
Cl i. fiS-- 1 v
CTa (ns/n
Ca fng'l >
Ra
Rxa
C d <•' TI 3 ' ' I )
Rd
Rxd (ng/g)
Ro
Glass
MB Er. <5j>
16179.
3.
1.
—
—
1100.
3.
990.
144.
16.
10.
1.
7.
0.
8.
0.
r .
0.
7 .
—
—
06
00
66
00
03
06
00
61
55
81
95
32
09
71
45
32
12
10179.
3.
1.
—
—
1190.
3.
990.
J44.
16.
11.
2.
3.
0.
8.
0.
8.
0.
7.
—
—
60
00
66
00
00
00
00
61
32
01
46
58
74
73
69
21
88
10179.
3.
1.
—
—
1100.
3.
990.
144.
16.
13.
1.
10.
2.
9.
0.
9.
0.
8.
—
—
00
66
66
60
00
00
00
61
09
68
37
26
56
66
00
88
11
10179.
3.
1.
—
—
1160.
3.
996.
144.
33.
24.
3.
19.
0.
19.
0.
18.
0.
18.
—
—
00
00
00
00
00
00
00
22
66
34
38
78
40
80
79
19
60
10179.
3.
1.
--.
—
1100.
3.
998.
14f.
33.
25.
2.
23.
8.
15.
1.
14.
3.
11.
—
—
00
00
66
60
00
00
00
22
12
92
18
68
84
13
86
36
50
10179.88
3.88
1.88
— — .
--.
1160.80
3.88
990.08
H4.08
66.44
52.06
6.35
41.55
4.09
39.95
1.75
38.59
1.13
37.46
—
—
-------
TABLE 15/cont'd) ISOTHERM
Sediment =
Mass = 1100
Saginaw Bay Station #50
mg/£ Time of Adsorption
= 3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 144 hr.
Date
Expt.
Type
nq. Phase
PH
Ionic
Ma (ng
Ta (hr
Md
>
'1 >
>
3.-'l>
3-''l>
ci,'1>
3'3>
3-''3>
OK 1 >
Rd (ncj.-'cj)
Rxd (n;
Ro (Ti;
G1 ass
MB Er.
3.-'cj>
3-'3>
( p 3 )
( '•'. >
10179.
3.
1.
•A •<•
_-
1188.
3.
996.
144.
66.
66.
6.
49.
9.
44.
1.
42.
2 f
39.
—
— —
03
03
00
00
88
68
36
44
63
82
65
85
13
81
75
95
86
13179.
3.
1.
_ _
.. _
1108.
3.
990.
144.
132.
114.
12.
93.
13.
85.
3.
83.
3.
80.
_ _
— —
36
63
03
83
08
08
88
88
57
16
18
84
59
07
35
29
86
10175.
3.
1.
*• -•.
1138.
•3
N^ •
998.
144.
132.
114.
12.
92.
13.
81.
3.
79.
4.
74.
— —
«» •*
03
63
00
30
66
60
83
88
15
16
72
84
55
88
26
58
63
10179.
3.
1.
1188.
3.
996.
144.
132.
187.
11.
86.
19.
73.
2.
71.
4.
66.
00
00
08
33
38
33
86
88
01
97
48
58
78
88
53
72
82
-------
TABLE 16. ISOTHERM
Sediment = Montmorillonite
Mass = 50 mg/X.
Time of Adsorption = 2-3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 1.5-3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Md
Td Chr)
Ci (ng/1 >
CTa (Tia/l )
Ca ("HS/I >
Ra
Rxa 3/3>
CTd
Cd 3/ 1 )
Rd
Glass Cp9>
HB Er. C'^>
6069.00
2.00
1.00
5.70
__
50.00
2.00
50.00
1.50
77.57
60.53
37.85
453.77
365.64
22.24
12.03
204.33
116.21
88.12
24.82
-18.77
6019.00
2.00
1.00
5.70
- —
50.00
2.00
50.00
1.50
22.54
19.52
11.10
168.38
111.22
8.40
3.69
94. 15
36.99
57.16
7.99
-9.86
3309.00
2.00
5.70
— —
50.00
2.00
50.00
1.50
22.54
17.60
9.43
163.38
80.28
8.16
2.81
107.03
23.93
83.10
5.42
-19.50
4010.00
3.00
1.00
~_
•» w
50.90
3.00
45.00
3.00
10.95
9.44
7.61
36.64
-13.01
3.88
1.78
46.61
-3.05
49.65
~—
^ ••
4010.00
3.00
1.00
«• *»
•M *W
50.00
3.00
45.00
3.00
21.90
18.60
13.07
110.58
58.84
5.37
2.53
63.14
11.39
51.74
— —
** **
4910.00
3.00
1.08
50.00
3.00
45.08
3.00
43.81
34.78
22.90
237.55
168.82
10.86
5.83
111.74
43.00
68.74
-------
TABLE 16. ISOTHERM (cont'd)
Sediment = Montmorillonite
Mass = 50 mg/£
Aqueous Phase = Distilled Water
Time of Adsorption = 2-3 hr. Time of Desorption = 1.5-3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta
Md (.n^s} >
Td Chr)
Ci (ng/1 >
CTa (noi/l >
Ca
Rxa (ng/g)
CTd (ngxl)
Cd (ng.-'l>
Rd
Rxd (ng/g>
Ro
Glass
MB Er.
4eie.ee
3.00
1.00
--
--
50.00
3.00
45.00
3.00
87.61
66.27
46.52
394.92
222.32
20.66
10.62
223.32
50.73
172.60
—
—
4eie.ee
3.00
1.00
—
—
50.00
3.00
45.00
3.00
204.43
167.88
98.35
1390.62
707.87
64.28
25.34
865.16
182.41
682.75
— —
— —
-------
TABLE 17. ISOTHERM
Sediment = Montmorillonite
Mass = 200 mg/J,
Aqueous Phase = Distilled Water
Time of Adsorption = 2-3 hr. Time of Desorption = 1.5-3 hr.
Date
Expt. Type
Act. Phase
pH
Tnni r
1 O II 1 1
Ma
Ta
Md
Td Chr)
C i ( T\ g / I )
CTa (tig/ 1 )
Ca < r.g/1 >
R a c. ft g / g ?
Rxa (Tici/q)
1 > ^\ N» • • i ^y ^y f
CTd
^/ ^^ ^ It ^^ * 1 r
Rol
Rxd Ctig/g)
Ro
Glass
5389.88
2.88
1.89
5.78
*•» ^
289.98
2.08
286.99
1.59
43.35
42.93
16.32
128.59
63.92
25.46
6.96
92.4?
26.90
65.5?
10.58
-0.62
3215.00
3.00
1.00
— —
....
200.09
3.00
180.09
3.99
--
10.38
4.28
39.48
9.63
6.40
1.88
25.99
4.24
20.85
__
— —
3215.18
3.98
1.00
•* "*
_.-
3.08
180.09
3.99
— -
13.99
5.77
36.61
3.31
8.56
2,33
34.64
1.33
33.39
~—
— •
3215.20
3.90
1.98
•»••
3.80
188.80
3.00
••••
27.33
12.15
75.93
22.13
15.53
4.40
61.82
8.02
53.80
** *" .
•M «•
3215.39
3.08
1.89
__
299.09
3.09
189.99
3.99
** "^
59.45
22.76
138.41
34,96
27.29
6.63
114.28
9.92
184.36
3215.48
3.89
1.89
280.89
180.99
3«K •&
.99
157.22
67.76
447.31
124.88
77.68
14.75
349.61
27.18
322.43
-------
TABLE 18. ISOTHERM
Sediment = Montmorillonite
Mass = 1000 mg/£
Time of Adsorption = 2 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1.5-3 hr.
Date
Expt. Type
ftq. Phase
PH
Ionic
Ha Oig/i)
Ta
Td (hr>
Ci
CTa (ng/l >
Ca
Ra
Rxa
CTd
Cd Cng.T,
Rd
Rxd
Ro
Glass Cpg)
MB Er. <«>
4059.00
2.09
1.00
6.30
—
1080.09
2.00
1080.09
1.59
54.76
43.69
12.08
31.61
4.08
31.61
3.05
29.56
1.03
27.53
8.55
. -18.65
4859.00
2. 00
1.00
6.30
—
1080. 00
2.00
1000.00
1.50
91.26
68. 63
21. 10
47.52
6. 15
47.46
4.71
42.75
1.37
41.37
11.43
-23.55
4059.00
2.00
1.00
6.30
--
1000.00
2.00
1000.00
1.50
146.02
109.50
37.58
71.92
10.52
71.91
8.21
63.69
2.30
61.40
22.03
-23.50
4029.00
2.00
1.00
6.30
__
1000.00
2.00
1000.09
1.50
18.07
18.78
4.40
14.38
2. 17
14.31
1.40
12.90
0.69
12.21
2.48
5.33
4029.00
2.00
1.00
6.30
M «•»
1000.00
2.00
1000. 00
1.50
54.21
59.39
15.50
43.89
5.32
43.84
3.93
39.91
1.35
38.56
5.29
10.53
4829.08
2.98
1.09
6.39
— —
1800.00
2.00
1008.09
1.50
90.35
97.22
25.97
71.25
8.19
71.04
6.07
64.97
1.91
63.06
11.97
8.93
-------
TABLE 18. ISOTHERM (cont'd)
Sediment = Montmorillonite
Mass = 1000 mg/S,
Time .of Adsorption = 2 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption - 1.5-3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma (M3/1)
Ta
Td (hr)
Ci M )
R a ( T\ 3 •' 3 )
Rxa (ng/g)
CTd (ng/1 >
Cd (rig/1 )
Rd
Ro (ng/g)
Glass (&g)
MB Er. <50
4029.00
2.00
1.00
6.30
—
1000.00
2.00
1000.00
1.50
144.56
136,80
34.93
101.86
12.58
101.7?
9.18
92.58
3.31
89.28
17.84
-4.14
3299.00
2.00
1.00
6.30
—
1000.00
2.00
1000.00
1.00
72.83
62.91
13.83
49.02
7.85
49. 00
5.00
44.00
2.82
41.18
20.23
-16.84
3299.80
2.00
1.00
6.30
—
1000.00
2.60
1000.00
1,50
72.83
62.37
12.80
49.57
6.02
49.55
4.08
45.47
1.92
43.55
10.7?
-12.88
3299.00
2.00
1.00
6.30
—
1000.60
2.00
1000.06
2.06
72.83
57.07
12.37
44.70
5.73
44.70
3.91
40.78
LSI
38.97
21. 11
-18.74
3299.09
2.00
1 .00
6.30
__
1000.00
2.00
1000.00
3.00
72.83
63.14
15.80
47.34
6.17
47.19
4.33
42.87
1.69
41.18
16.14
-11.08
-------
TABLE 19. ISOTHERM
Sediment = Montmorillonite
Mass = 50 mg/£
Time of Adsorption = 3 hr.
Aqueous
Time of
Phase = NaHCO-
Desorption = 3
Buffer
hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta (hr>
Md
Td
Ci (nci/l>
CTa <:ri3/l>
Ca
Ra
Rxa (risj/g)
CTd
Cd Cng/O
Rd (ngxg)
Rxd (ng.'g)
Ro
Glass (pg>
MB Er. <'/.>
7010.00
3.90
11.30
8.00
-.-
50.00
3.Q0
45.00
3.00
9.17
7.47
5.13
46.73
-23.56
5.07
2.41
59.22
-11.07
70.29
1.84
-49.90
7010.00
3.80
11.00
—
__
50 . 00
3.0Q
45.00
3.08
9.17
6.47
4. 14
46.55
7.51
3.99
2.06
42.78
3.74
39.84
5.23
-44.40
7010.00
3.00
11.09
6.00
— _
50. 00
3.00
45.00
3.00
18.34
14.80
7.85
139.08
93.47
7. 15
3.32
85. 18
39.56
45.62
3.63
-22.21
7018.00
3. 00
1 1.00
--
__
50.00
3.00
45.00
3.00
18.34
15.15
8.51
132.83
46.81
7.97
3.29
104. 10
18.09
66.01
6.24
-24.87
7810.00
3.60
11.00
8.00
56.00
3.00
45.00
3.00
36.69
29.59
15.20
287.66
155.81
15.59
6.61
199.56
67.71
131.85
10.46
-23.71
7010.88
3.86
11.80
50.88
3.08
45.08
3.60
36.69
30.91
16.44
289.25
137.92
15.43
6.26
203.85
52.51
151.34
5.06
-28.97
-------
TABLE 19. ISOTHERM (cont'd)
Sediment = Montmorillonite
Mass = 50 mg/J,
Time of Adsorption = 3 hr.
Aqueous Phase = NaHC03 Buffer
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
• *
PH
Ionic
Ma
Ta
Md (pig/I )
Td
Ci (T»g/l>
CTa ( rig/ 1 >
Ca
Rxa
CTd
Cd
•A . .
K a s TI 3 / 3 )
Rxd
Ro Cng/3;*
Gm
lass
• ^ MM ^^
MB Er. O:>
7010.00
3.00
11.00
7.95
__.
50.00
3.00
45.00
3.00
73.37
64.34
31.03
666.21
385.75
25.57
8.30
383.71
103.25
280.46
5.69
-5.53
7010.00
3.00
11.00
~_
«•*•
50.00
3.00
45.00
3.00
73.37
59.69
28.79
618.04
393.21
28.70
11.51
381.99
157.16
224.83
14.34
-17.90
7010.00
3.00
11.00
8. 00
50.00
3.00
45.00
3.00
110.06
91.23
5Q.41
816.25
375.21
40.05
15.13
553.66
112.62
441.04
9.49
-19.26
7910.80
3.00
1 1 . 80
on •»
50.00
3.00
45. 00
3.00
110.06
82.90
43.48
788.50
389. 13
45.52
19.64
575.15
175.78
399.38
32.64
-30.83
-------
TABLE 20. ISOTHERM
~ • • - ' - -
Sediment = Montmorillonite
Mass = 1100 mg/S.
Time of Adsorption = 3 hr.
Aqueous Phase = NaHCO
Time of Desorption =
3 Buffer
3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Md (ngx'l)
Td (hr>
Ci (T»gxl>
CTa Cng/1)
Ca
Ra
Rxa (ng/g)
CTd (ng/1)
Gd
Rd
Rxd (ng/g)
Ro (ng/g>
Glass (pg>
MB Er. OO
6280.00
3.00
11.00
8.40
— —
1100.00
3.00
9S-0.09
3.00
22.2?
25.88
5.55
18.48
9.86
14.99
2.34
12.78
4.15
8.63
2.23
32.11
6200.00
3.00
11.00
—
— _
1 100.00
3.00
990.80
3.09
22.27
29.81
5.48
13.93
-0.86
16.25
1.91
14.49
-0.30
14.79
2.67
-16.43
6200.00
3.00
11.00
8.40
_—
1 100.00
3.00
996.00
3.00
44.54
39.94
11.79
25.59
4.31
25.39
3. 18
22.44
1. 16
21.28
6.37
-9.03
6200.08
3.00
11.00
_-
_..
1100.00
3.00
990.09
3.09
44.54
41.01
13.24
25.25
1.62
27.39
3.56
24.06
0.44
23.63
5.16
-12.13
6200.00
3.00
11.00
8.48
__.
1100.00
3.08
990.00
3.00
55.67
48.88
15.28
30.61
4. 14
30.86
3.67
27.47
1.00
26.47
11.44
-11. 14
6289.ee
3. 08
n.ee
__
_ _
1100.00
3.00
990.80
3.80
55.67
50.69
15.38
32.10
5.36
31.80
3.96
28.12
1.38
26.74
14.80
-6.32
-------
TABLE 20. ISOTHERM (cont'd)
Sediment = Montmorillonite
Mass = 1100 mg/fc
Time of Adsorption = 3 hr.
Aqueous Phase = NaHCO_ Buffer
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (ng/1)
Ta (hr)
Md (rig/1 )
Td (hr)
Ci (ng/l)
CTa (ns/1)
Ca (ng/l )
Ra (ng/g)
Rxa (ns/3)
CTd (ng/l)
Cd (ng/l )
Rd (ng/g)
Rxd (ng/g)
Ro (ng/g)
Glass (pg)
MB Er. (5O
62ee.ee
3.00
11.00
8.40
—
1100.00
3.00
990.00
3.00
66.30
60.40
19.27
37.38
4.54
37.58
4.11
33.81
0.57
32.85
8.30
-9.20
62ee.ee
3. 00
11.00
—
—
1100.00
3.00
990.00
3. 00
66.80
59.95
18.93
37.30
2.96
39.03
4.36
35.02
0.68
34.33
10.53
-11.83
62ee.ee
3.90
11.00
8.50
--
1100.00
3.00
990.00
3.00
87.96
80.75
26.98
48.83
12.06
44.83
5.80
39.42
2.59
36.82
22.60
-1.57
62ee.ee
3.00
11.00
—
--
1100.00
3.00
990.00
3.00
87.96
75.67
27.06
44.19
5.01
45.21
5.42
40.19
1.00
39.19
29.34
-12.29
-------
TABLE 21. ISOTHERM
Sediment = Kaolinite
Mass = 1000 mg/£
Time of Adsorption = 2.0 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1.5 hr.
Date
Exot. Type
Aq. Phase
PH
Ionic
Ma
Md (ris/l)
Td
Ci
CTa
Ca
Ra
Rxa
CTd (ng/l)
Cd
Rd Cr>3/3>
Rxd (ng/'3>
Ro (ns/g)
Glass
MB Er.
4099.00
2.00
1.00
8.70
__
1800.00
2.00
1000.00
1.50
18.43
18.93
8.22
10.70
3.84
10.68
2.60
8.08
1.21
6.87
4.59
5.15
4099.60
2.90
1.00
8.70
__
1000.00
2.60
1000.00
1.50
36.87
39.93
22.23
17.70
4.95
17.54
3.92
13.62
0.87
12.75
10.44
11.12
4099.00
2.00
1.00
8.70
__
1000.00
2.00
1000. 00
1.50
73.74
69.90
34.13
35.77
12.11
35.35
8.62
26.73
3.06
23.67
28.34
-1.36
4099.00
2.00
1.00
8.70
1000.00
2. 00
1000.00
1.50
147.48
145.26
64.42
80.83
26. 11
80.66
18.46
62.20
7.48
54.72
28.91
0.45
-------
TABLE 22^ SOLUTION COMPOSITION
Sediment = Montmorillonite
Mass = 200 mg/X. Time of Adsorption = 4
hr.
Aqueous Phase = NaCl
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Md
Id
CTa
Ca (rii)-' 1 >
Ra <.Tis--3>
Rxa
CTd
/% j /• ^ .*. * i \
Cd <. Ti3-' 1 }
Rd
Rxd (ing's)
Ro Cng/g)
Glass
MB Er. <.'<>
5699.66
i.ee
4.66
6.66
1.66
266.66
4.Q6
_-
—
31.96
41.75
12.01
148.72
—
—
—
—
—
--_
9.14
33.49
5699.66
1.66
4.66
6.66
5.66
268.66
4.66
—
--
31.96
£7.28
9.81
87.34
—
—
—
--
--
.
13.21
-16.56
5699.66
1.66
4.66
6.66
18.66
266.66
4.66
—
—
31.96
28.53
11.77
83.79
—
—
—
—
—
—
16.36
-7.49
5899.66
1.90
4.68
6.66
56.66
266.68
4.68
—
--
31.96
27.33
6. 55
163.93
--
-_
--
—
--
--
21.65
-7.71
5i79.ee
i.ee
4.99
6.68
i.ee
2ee.ee
4.66
— -
.-
38.16
24.34
7.98
81.81
— -
— -
— -
•» Mk
--
--
38.92
-8.85
5i79.ee
i.ee
4.ee
6.66
3.88
298.ee
4.86
--
—
36.16
24.43
8.92
77.54
—
— —
-•—
— —
— —
_ -
22.23
-11.46
-------
TABLE 22. (cont'd) SOLUTION COMPOSITION
Sediment = Montmorillonite
Mass = 200 mg/i Time of Adsorption = 4
hr.
Aqueous Phase = NaCl
Date
Expt. Type
Ad. Phase
pH
Ionic
Ma
Ta (hr>
Md 013/1 >
Td
Ci (rig/I >
CTa (ng.-'O
Ca (ns-'l >
Ra
Rxa
CTol
Rd
Rxd
Ro
Glass '•'PS)
MB Er. <:-;>
5179.90
1.00
4.00
6.68
50.80
200.00
4.00
—
-_
30.10
27.01
6.96
100.28
—
—
—
—
—
—
19.81
-3.67
5229.00
1.00
4.00
&. 60
20.00
200.ee
4.00
—
—
33.29
30.25
10.66
98.25
—
—
—
—
—
-- .
13.50
-5.09
5229.00
1.00
4,00
6.60
60. 00
200.00
4.00
—
—
33.29
30.59
8.76
109.15
—
—
__
—
—
—
12.57
-4.35
5259.00
1.00
4.06
6.60
100.00
200.00
4.00
—
—
35.03
32.95
S.84
120.56
—
—
—
_-
—
10.78
-2.84
-------
TABLE 23, SOLUTION COMPOSITION
Sediment = Montmorillonite
Mass = 200 mg/l
Aqueous Phase = HC1 and NaOH
Time of Adsorption = 4 hr.
Date
Expt. Type
Act. Phase
PH
lOTtlC
Ma (MS--!;.
Ta <.hr>
Md CMS--'! >
Td Chr)
Ci (Ticj.-'l >
CTa
.—. * ~ « ..
La *. Ti3-- i >
Ri * * ^
.a i. Ti 3 •' 9 r
Rxa ( ng-''3>
CTd
Cd Cngxl)
R d *' r» 3 •'' 9 ^
Rxd frig's)
Ro f.Ti3''3)'
Glass (P9>
i.« r% r* .. » «» v
5219.88
1.88
5.00
6.25
0. 18
283.38
4.80
—
—
33.29
28.84
9.66
95.90
—
~~
—
—
—
—
10.78
« A 4 A
5219.00
1.88
5.80
6.25
0.38
208.00
4.00
—
—
33.29
28.49
3.16
101.62
—
--
—
—
—
—
12.71
• ft f «i
5189.00
1.68
5.00
4.17
8.60
208.00
4.80
—
—
33.99
29.99
7.88
110.97
—
—
—
—
—
—
14.57
^ ji ^
5i89.ee
i.ee
5.08
3.73
1.28
280.00
4.60
—
—
33.99
32.51
9.46
115,25
—
—
—
—
—
—
11.16
< n /•
5229.ee
i.ee
6.08
6.78
8.28
208.ee
4.80
—
—
33.29
35.74
16.95
93.97
--
--
—
—
—
••* *•
18.66
4 /% & •%
5229.ee
i.ee
6.88
6.78
8.58
2ee.ee
4.88
—
—
33.29
31.59
14.22
S6.82
—
—
—
—
—
—
18.56
« ntr
-------
TABLE 23Ccont'd) SOLUTION COMPOSITION
Sediment = Montmorillonite
Mass = 200 mg/£
Aqueous Phase = HC1 and NaOH
Time of Adsorption = A hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma (nsj-'l >
Ta
Td
Ci Cr.3/l>
CTa
Co. .'3>
Rxa (ns.-'a)
CTd (. n3/1 >
Cd (rig.-'];.
Rd < 113/3 >
Rxd
Ro
Glass
MB Er. f.V.>
5189.08
1.00
6.08
7.75
1.83
288.80
4.00
—
--
33.99
31.65
14.11
87.69
—
—
—
—
—
—
10.90
-3.67
5189.80
1.00
6.00
9.30
2.00
203.38
4.38
__.
—
33.99
33.31
16.82
82.45
--
--
—
--
--.
—
10.53
1.18
-------
TABLE 24. SOLUTION COMPOSITION
Sediment = Montmorillonite .
Mass = 200 mg/X,
Aqueous Phase = CaCl?
Time of Adsorption = 4 hr.
Date
Expt. Type
ftci. Phase
PH
Ionic
Ha
Hd (M3.-'l >
Td Chr>
Ci <:r.s/1>
CTa (r,3/l>
Ca
Ra Cr,3''g>
CTd
Cd
Rd (fi3-'9)
Rxd
Ro (T>3''3>
Glass
MB Er. O;>
6149.08
1.88
7.88
6.58
1.88
200.68
4.00
— —
— -
28.44
27.14
9.89
90.24
__
—
—
—
—
11.02
-8.68
6149.88
1.88
7.80
6.50
5.00
288.08
4.88
-_
—
28.44
28.00
6.21
108.91
..—
--
—
—
-_
16.81
4.36
6149.00
1.08
7.00
6.60
18.00
200.80
4.88
—
—
28.44
28.67
4.73
119.72
-_.
- —
—
—
—
3.16
3.70
6i99.ee
1.08
7.60
6.60
9.80
280.80
4.80
—
__
28.44
23.93
9.51
72.09
--
—
— -
—
—
13.93
-10.95
6i99.ee
i.ee
7.00
6.58
38.ee
268.80
4.08
—
—
33.29
24.08
3.67
182.86
~~
—
—
--
—
8.88
-25.88
6i99.ee
i.ee
7.08
6.68
se.ee
2ee.ee
4.88
—
—
33.29
24.69
10.32
71.36
--
—
--
—
--
27.15
-17.96
-------
TABLE 25. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station 43
Mass = 1100 mg/X. Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt
Aq.
PH
loni
Ma <
Ta <
Md (.
Td <
Ci
CTa
Ca
Ra
Rxa
CTd
Cd
Rd
Rxd
Ro
. Type
Phase
c
M3/1 )
hr>
rig/I )
hr)
(Tiot.-'l )
(Tig/3>
(. 7*1 3 / 3 f
\ n 3 / 1 )
Cns/1 >
* ^ » «- \
1216.
3.
1.
«» «••
1180.
3.
998.
3.
—
10.
1.
8.
-i.
9.
0.
8.
-1.
9.
00
08
00
00
00
00
00
08
11
79
42
60
90
00
91
1210.00
3.00
1.90
—
—
1108.00
3.00
990.08
3.08
—
9.74
1.01
7.93
-1.23
8.96
0.52
8.53
-0.63
9.16
1218.
3.
1.
—
—
1100.
3.
998.
3.
-..
18.
1.
15.
0.
16.
0.
15.
8.
15.
68
60
68
00
66
60
08
79
47
75
61
03
74
45
31
14
1218.
3.
1.
—
—
1100.
3.
998.
3.
--
39.
2.
33.
8.
33.
1.
33.
0.
32.
00
88
88
08
68
60
00
61
80
46
68
93
19
07
29
78
1218.
3.
1.
— ?
—
1168.
3.
990.
3.
—
56.
3.
48.
-1.
50.
1.
49.
-0.
49.
08
86
08
08
00
06
08
85
65
37
51
18
36
31
56
88
1210.68
3.80
i.ea
--
--
1188.09
3.60
998.88
3.80
--
77.58
6.27
64.82
8.43
65.44
1.58
64.51
8.11
64.48
Glass
MB Er.
-------
TABLE 26. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station 50
Mass = 1100 mg/£ Time of Adsorption - 3 hr.
Aqueous Phase = Distilled
Time of Desorption = 3 hr
Water
•
Dote
Expt. Type
Aq. Phase
PH
Ionic
Ma (rig/I)
Ta
fld (ng/1)
Td (hr)
Ci
CTa
Ca
Ra Cng/g)
Rxa
CTd
Cd
Rd
Rxd (ng/g>
Ro (Tig/g)
Glass Cpg>
MB Er. <*>
7189.80
3.00
1.09
—
— —
1180.08
3.60
990.00
3.00
16.79
16.60
1.95
13.31
0.90
13.73
0.99
12.87
0.46
12.41
2.33
-3.06
7189.00
3.89
1.90
--
1100.00
3.00
990.00
3.00
50.38
53.66
5.40
41.15
0.97
42.00
1.89
40.51
0.34
40.17
3.72
-1.21
7189. 00
3.00
1.00
—
1100.60
3.00
990.00
3.00
83.96
81.26
8.63
66.03
-0.34
69.00
3.43
66.23
-0.13
66.37
8.17
-6.56
7189.00
3.00
1.00
—
• —
1100.00
3.00
990.00
3.00
134.34
132.25
14.35
107.19
15.44
99.92
4.40
96.48
4.74
91.75
7.82
3.65
ieio9.ee
3.00
i.ee
«-
«•» *»
1100.00
3.00
990.00
3.00
15.33
14.52
1.66
11.69
1.08
11.74
0.75
11.10
0.49
10.61
1.10
-5.65
10189.89
3.99
1.00
—
—
1100.00
3.00
990.00
3.00
30.66
27.79
3.01
22.53
-0.12
23.48
1. 10
22.61
-0.05
22.65
1.36
-12.78
-------
TABLE 26. (cont'd) ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station
Mass = 1100 mg/Jl
50
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma 0-13.' 1>
Ta
Td
Ci (ng/1)
CTa (fi3/l>
Ca (ng/l)
Ra Cn3/3>
Rxa
CTd
Cd Cng/1>
Rd (ng/g>
Rxd (ng/g>
Ro
Glass
MB Er. C^>
18107.00
3.00
1.00
—
•»•«
1103.00
3.00
990.00
3.00
30.66
2?. 34
3.30
21.85
-1.18
23.51
1.10
22.64
-0.39
23.03
1.66
-16.40
10109.00
3.00
1.00
—
—
1100.00
3.00
990.00
3.00
61.33
56.95
6.32
46.02
-15. 15
57.51
2.22
55.85
-5.33
61. 18
5.21
-25.78
10109.00
3.00
1 . 00
— -
—
1100.00
3.00
990.80
3.00
122.66
127.42
12.55
104.43
50.87
70.65
3.52
67.81
14.25
53.56
11.35
31.50
18129.00
3.00
1.09
—
—
1100.00
3.00
990.00
3.00
15.33
14.18
1.75
11.30
0.43
11.37
0.49
10.99
0.12
10.88
1.31
-7.84
10129.00
3;100
1.00
—
—
1100.00
3.00
990.00
3.90
30.66
35.10
3. 16
29.04
15.87
17.50
0.75
16.92
3.76
13.16
13.01
55.39
10129.99
3.90
1.80
—
—
1198.98
3.00
990.80
3.00
61.33
56.08
6.59
44.99
8.38
40.88
1.70
38.77
2.17
36.61
11.65
0.61
-------
TABLE 26. (cont'd) ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station
Mass = 1100 mg/Jl
50
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (rig/1 )
Ta (hr>
Md (M3/1 >
Td (hr)
Ci (113/1 >
CTa (T»g/1 >
Ca (ng/1)
Ra ( 113/3 >
Rxa (ng/3>
CTd (ng/O
Cd
Glass (P3>
MB Er.
10129.00
3.00
1.00
—
—
1100.00
3.00
990.00
3.00
122.66
112.97
14.21
89.78
21.10
75.10
2.88
72.95
4.27
68.67
19.16
4.90
10179.00
3.00
1.00
—
1100.00
3.00
990.00
3.00
16.61
11.60
1.83
8.89
1.18
8.78
0.70
8.16
0.45
7.71
—
—
10179.00
3.00
1.00
—
—
1100.00
3.00
990.00
3.00
33.22
24.14
3.07
19.16
8.55
15.18
1.25
14.06
3.47
10.61
—
•MM
10179.00
3.00
l.OO
—
Mk •*
1100.00
3.00
990.90
3.00
66.44
53.73
6.01
43.38
20.86
31.80
2.14
29.96
7.43
22.52
--
—
10179.00
3.00
1.00
--
—
1100.00
3.00
990.00
3.00
132.88
111.86
12.09
90.69
17.04
80.13
3.01
77.89
4.24
73.65
--
—
-------
TABLE 27. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Montmorillonite
Mass = 1100 mg/IL
Time of Adsorption = 3 hr.
Aqueous Phase = NaHCO_ Buffer
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Td
CTa Cng/1 >
Ca (ng/1 >
Ra g/g>
CTd
Rd (ng.'g)
Rxd
Ro (ng/g)
Glass
MB Er.
6200.00
3.00
11.00
8.40
--
1100.00
3.00
990.00
3.00
22.2?
25.88
5.55
18.48
9.86
14.99
2.34
12.78
4.15
8.63
2.23
32.11
6200.00
3.00
11.00
—
—
1109,08
3.00
990.00
3.00
22.27
20.81
5.48
13.93
-0.86
16.25
1.91
14.49
-3.39
14.79
2.67
-16.43
6200.00
3.00
11.00
8.40
—
1100.00
3.00
990.00
3.00
44.54
39.94
11.79
25.59
4.31
25.39
3.18
22.44
1.16
21.28
6.37
-9.03
6200.00
3.00
11.00
—
—
1100.00
3.00
990. 00
3.00
44.54
41.01
13.24
25.25
1.62
27.39
3.56
24.06
0.44
23.63
5.16
-12.13
6200.00
3.00
11.00
8.40
--
1100.00
3.00
990.08
3.00
55.67
48.88
15.28
30.61
"4.14
30.86
3.67
27.47
1.00
26.47
11.44
-11. 14
6200.00
3.88
11.80
— —
— —
1100.00
3.00
990.00
3.09
55.6?
50.69
15.38
32.19
5.36
31.80
3.96
28.12
1,38
26.74
14.89
-6.32
-------
TABLE 29. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station 19
Mass = 1100 mg/X- Time of Adsorption = 3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (P19/1 >
Ta (hr>
Md (rig/I)
Td (hr>
Ci
CTa
Ca c.ng/1 )
Ra Cng/oj)
Rxa
CTd
Cd Cng/l>
Rd
Rxd Cng/3>
Ro (ng/g)
Glass
MB Er.
1180.00
3.00
1.00
—
—
1100.00
3.00
996.00
3.00
30.30
29.83
2.61
25.34
0.05
26.19
1.13
25.31
0.03
25.28
•• w*
--
1180.00
3.00
1 . 00
— ~
-~,
1100.00
3.00
999.90
3.00
30.30
30.13
1.65
25.89
0.52
26.49
1.04
25.70
0.33
25.38
—
--
1186.00
3.00
1.00
--
-—
1100.00
3.00
990.00
3.00
60.60
58.39
3.04
50.31
1.84
50.74
1.72
49.52
1.04
48.48
—
—
1180.00
3.80
1.80
--
—
1100.00
3.00
990.00
3.00
121.20
120.22
6.74
103.17
9.40
100.20
3. 10
98.08
4.32
93.77
—
—
1180.00
3.00
1.80
~-
—
1100.00
3.00
990.00
3. 90
181.79
174.61
11.68
148.11
-20.66
163.37
4.96
160.01
-8.77
168.78
—
—
1189.88
3.08
1.06
...
__
1190.00
3.00
990.80
3.08
242.39
231.31
14. 11
197.46
-2.30
202.32
5.44
198.87
-0.89
199.76
—
—
-------
TABLE 28. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station
Mass = 20,000 mg/£ .
69
Time of
Aqueous
Adsorption = 3 hr. Time of
Phase = Distilled Water
Desorption = 3 hr.
Date
Expt. Type
flq. Phase
PH
Ionic
Ma
Ta (hr)
Md fng/1)
Td
Ci (ng/1>
CTa (ng/1>
Ca (ng/1>
Ra
Rxa
CTd (ng/l>
Cd
Rd (ng.'g)
Rxd
Ro
Glass (pg>
MB Er. <*>
3050.00
3.00
1.00
—
—
20000.00
3.00
18000.00
3.00
40.70
22.83
10.55
0.61
0.68
9.69
5.04
8.26
0.33
-0.07
—
—
3050.00
3.00
1.00
—
— —
20000.00
3.00
18080.00
3.00
46.70
28.90
11.82
8.49
588. 28
-5820.48
4.86
-279.19
220.60
-499.79
—
• • . --
3050.00
3.00
1.00
—
—
20880.08
3.88
18000.08
3.88
81.41
38.52
21.18
0.87
0.78
16.37
8.33
0.45
0.28
0. 17
—
—
3050.00
3.00
1.00
. —
--
20000.00
3.00
18008.08
3.88
162.81
95.71
51.08
2.23
1.76
32.48
14.81
0.98
0.51
0.47
—
—
3050.00
3.00
1.00
—
<••» *•
20000.00
3.08
18000.88
3.00
244.22
150.22
91.30
2.95
2.68
34.28
19.32
0.83
8.57
0.26
—
--
3050.08
3.00
1.88
--
—
20008.00
3.00
18000.00
3.08
325.62
188.57
123.62
3.25
2.54
58. 12
27.26
1.27
8.56
0.71
—
—
-------
TABLE 31. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw Bay Station 53
Mass = 1100 mg/£ Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta (hr)
Md (rig/1 >
Td (hr)
Ci (r.g.'l)
CTa
Ca
Rxa (rig/g)
CTd (ng/1 )
Cd
Rd (ng.'g)
Rxd (ng/g)
Ro
MB Er. <*>
-------
TABLE 30. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw River
Mass = 1100 mg/£ Time of Adsorption = 3 hr.
Aqueous Phase = Distilled
Time of Desorption = 3 hr.
Water
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (Mg/1)
Ta (hr>
Md (rig/1 >
Td (hr)
Ci (ng/1 >
CTa (rig/1 )
Ca (ng/1 >
Ra (ng/g)
Rxa (ng/g)
CTd (ng/1 >
Cd (rtg/l >
Rd (ng/g>
Rxd (ng/g)
Ro (ng/g)
ii60.ee
3.00
1.00
—
-_
1100.00
3.00
990.00
3.00
30.30
27.93
2.57
23.05
3.00
22.80
1.37
21.64
1.59
20.05
1160.09
3.00
1.00
—
—
1100.06
3. 00
990.00
3.86
30.38
28.01
2.39
23.29
3.26
23. 03
1.36
21.89
1.86
20.03
1160.00
3.00
1.00
— —
—
1100.00
3.00
990.00
3. 00
60.60
54.72
4.21
45.92
2.42
46.42
2. 14
44.73
1.23
43.50
1160.08
3.00
1.00
— —
— —
1100.00
3.00
990.00
3.00
121.29
111.38
9.81
92.33
-1.87
96.41
3.88
93.47
-0.74
94.21
1160.80
3.00
1.66
•. «•»
— —
1100.00
3. 00
990.00
3.00
181.79
159.31
15.51
130.73
-5.79
138.34
5.05
134.63
-1.88
136.52
1168.88
3.06
1.60
•M ^
1108.60
3.00
990.80
3.00
242.39
212.96
17.91
177.32
7.51
176.65
6.04
172.34
2.53
169.81
G1ass (pg>
MB Er. <*>
-------
TABLE 32. (cont'd) ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw
Mass = 1100 mg/J.
Bay Station
31 Aqueous Phase = Distilled Water
Time of Adsorption = 3 hr. Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (ng'n
Ta (hr)
Md (ng/1 >
Td Chr>
Ci
CTa
Ca
Ra (ns/s)
Rxa (ng^S)
CTd <.'n3'/1 )
Cd (Tis/1 >
Rd (ng/g)
Rxd
Ro ( ^3^9 ^
Glass
MB Er. <.'/.">
ii5e.ee
3.88
1.88
—
—
1108.80
3.09
990.00
3.08.
171.94
164.34
12.57
137.97
2.15
140.63
5.27
136.73
0.90
135.83
—
1158.08
3.88
1.88
-—
—
1180.00
3.80
990.08
3.00
229.25
217.16
14.88
183.89
5.88
183.29
5.87
188.02
2.01
178.82
—
—
-------
TABLE 32. ISOTHERM - SEDIMENT COMPOSITION
Sediment = Saginaw
Mass = 1100 mg/Jl
Bay Station
31
Time of Adsorption
= 3 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 3 hr.
Dote
Expt. Type
Aq. Phase
PH
Ionic
Ma Cng.-'l >
Ta (hr)
Md
Td (hr>
Ci
CTa
Ca (ng/1 >
Ra
Rxa (ng/g>
CTd g/g>
Rxd <".ng/g>
Ro
Glass
MB Er. <*>
1150.00
3.00
1.00
—
—
1100.00
3.00
990.00
3.00
42.98
39.70
3.58
32.84
-0.41
34.08
1.31
33.09
-0.15
33.24
—
—
1150.00 1
3.60
1.09
—
-_ •
1109.09 1
3.00
999.00
3.60
42.98
40.16
2.66
34.09
-0.84
35.34
1.11
34.58
-Q.35
34.93
—
—
150.00
3.00
1.08
— —
—
100.00
3.00
990.00
3.00
85.97
80.91
5.93
68.16
2.40
67.84
1.95
66.56
0.79
65.77
—
—
1150.00
3.00
1.00
—
—
1100.00
3.00
—
—
85.97
82.81
6.26
69.59
—
—
—
--
—
--
—
— —
1150.00
3.00
1.00
—
—
1100.00
3.00
—
—
114.63
111.75
6.10
96.04
--
—
—
—
—
—
--
--
1150.00
3.00
1.99
--
—
1100.00
3.80
990.00
3.00
114.63
111.70
5.99
96. 11
10.98
91.57
2.59
89.88
4.75
85.12
—
— -
-------
TABLE 33. SEDIMENT CONCENTRATION
(cont'd)
-Sediment = Montmorillonite
Time of Adsorption •= 2 .hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ha (MS/I. )
Ta (hr)
Md
Ci (ng/1)
CTa (tig/I)
Ca (r,g/l>
Ra (713/3)
Rxa (ri3/g>
f» •* | i m fc
CTd
Cd (ns/1 >
Rd (ns/s)
Rxd
Ro (Ti3/s>
Glass (ps>
MB Er. O;>
5309.00
2.00
1.00
5.70
. __
50.00
2.00
50.00
1.50
22.54
17.66
9.43
163.38
80.28
8.16
2.81
107.03
23.93
83.10
5.42
-19.50
6019.00
2.00
1.00
5.70
i
100.00
2.00
100.00
1.50
31.21
30.57
18.59
119.80
79.75
11.94
5.55
63.87
23.82
40.05
5.29
-0.36
5299.00
2.00
1.00
5.65
_-
190.00
2.00
100.00
1.50
30.88
28.09
12.59
154.99
76.68
15.49
4.76
107.30
28.99
73.31
12.97
-4.83
Aqueous Phase = Distilled Water
Time of Desorption = 1-3 hr.
5309.00
2.00
1.08
5.70
-_
200. 00
2.00
200. 00
1.50
43.35
42.03
16.32
128.59
63.02
25.46
6.96
92.47
26.90
65.57
10.50
-0.62
5299.00
2.00
1.00
6.27
— _
500.00
2.00
500.00
1.50
60.05
51.39
15.81
71. 16
21.84
35.56
6.45
58.23
8.91
49.32
18.47
-11.34
4059.00
2.00
1.00
6.30
__
1000.00
2.09
1000.80
1.59
54.76
43.69
12.08
31.61
4.08
31.61
3.85
28.56
1.03
27.53
8.55
-18.65
-------
TABLE 33. SEDIMENT CONCENTRATION
Sediment = Montmorillonite
Time of Adsorption = 2 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1-3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta. .(hr,)
Nd (ng/1>
Td (hr)
Ci (rig/I >
CTa (Ti3/1 >
Ca
Ra (ng/g)
Rxq (Tig'g)
CTd
Cd Cng/1 >
Rd (rig/g)
Rxd
Ro
MB Er.
5309.00
2.00
1.00
5.50
__
10.00
2.00
10.00
1.50
13.87
13.42
8.46
495.83
411.26
4.93
2.75
218.28
133.72
84.57
5.72
0.83
6069.00
2.00
1.00
5.60
—
25.00
2.00
25.00
1.50
62.06
46.58
28.81
710.69
585.77
17.59
9.53
318.71
193.80
124.91
39.46
-18.58
6019.00
2.00
1.00
5.60
—
25.00
2.00
25.00
1.50
17.34
16.35
13.63
228.87
132.00
5.60
2.43
127.03
30.16
96.87
6.68
-1.87
5369.00
2.00
1.00
5.50
—
25.00
2.00
25.00
1.50
17.34
15.41
8.77
265.39
169.47
6.56
2.80
150.09
54. 17
95.92
6.33
-7.46
6869.00
2.00
1.00
5.70
-—
58.00
2.00
50.00
1.50
77.57
60.53
37.85
453.77
365.64
2£. 24
12.03
204.33
116.21
88.12
24.82
-18.77
6819.ee
2.99
1.00
5.79
——
59.00
2.89
59.09
1.59
22.54
19.52
11.10
168.38
111.22
8.40
3.69
94. 15
36.99
57.16
7.99
-9.86
-------
TABLE 33. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Montmorillonite
Time of Adsorption = 2 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1-3 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (rag/I)
Ta
Md
Td
CTa
Ca (Tig/l)
Ra Cng/g>
Rxa (rtg/g)
CTd (r.3/1)
Cd
Rd
Rxd
Ro
Glass
MB Er. d':>
3299.00
2.09
1.00
6.30
--
1000.00
2.00
1090.00
1.00
72.83
62.91
13.88
49.62
7.85
49.00
5.00
44.00
2.82
41. 18
20.23
-10.84
3299.00
2.00
1.00
6.30
—
1000.00
2.00
1008.00
1.50
72.83
62.37
12.80
49.57
6.02
49.55
4.08
45.47
1.92
43,55
10.77
-12.88
3299.00
2.09
1.00
6.30
—
1000, 00
2.08
1030.00
2.00
72.83
57.07
12.37
44.70
5.73
44.70
3.91
40.78
1.81
38.97
21. 11
-18.74
3299.00
2.00
1 .00
6.30
—
1000.00
2.00
1000. 00
3. 00
72.83
63. 14
15.80
47.34
6. 17
47. 19
4.33
42.87
1.69
41. 18
16. 14
-11.08
-------
TABLE 33. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Montmorillonite
Time of Adsorption = 2 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1-3 hr.
Date
Expt. Type
flq. Phase
PH
Ionic
Ma (rig/l>
Ta (hr)
fid
Td
Ci
CTa
Ca
Ra
Rxa
CTd
Cd
Rd
Ro
Glass
MB Er. <*>
4e59.ee
2.00
1.80
6.30
— —
1000.90
2.86
1093.60
1.50
91.26
68.63
21.10
47.52
6.15
4?. 46
4.71
42.75
1.37
41.37
11.43
-23.55
4053.09
2.09
i.ee
6.39
—_
1000.90
2.Q0
1000.00
1 . 50
146.02
109.50
37.53
71.92
10.52
71.91
S.21
63.69
2.30
61.40
22.03
-23.59
4629.90
2.90
1.90
6.30
**•_
1000.00
2.00
1000.00
1.50
18.07
18.78
4.40
14.38
2.17
14.31
1.40
12.90
0.69
12.21
2.48
5.33
4029.00
2.00
1.99
6.39
_ , —
1000. 00
2.00
1000.00
1.50
54.21
59.39
15.50
43.89
5.32
43.84
3.93
39.91
1.35
38.56
5.29
10.53
4029.00
2.90
1.09
6.30
__
1000.00
2.00
1.50
90.35
97.22
25.97
71.25
8.19
71.04
6.07
64.97
1.91
63.06
11.97
8.93
4829.09
2.99
1.08
6.38
1000.08
2.09
1000.08
1.50
144.56
136.80
34.93
101.86
12.58
101.77
9.18
92.58
3.31
89.28
17.84
-4. 14
-------
TABLE 34. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Montmorillonite
Time of Adsorption = 2 hr.
Aqueous Phase = Supernatant
Time of Desorption = 1.5-5 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma Cng/1)
Ta (hr)
Md
Td
Ci (ng/l >
CTa s/1>
Ca
Ra (ng/cj)
Rxa (ng/g)
CTd
Cd
Rd
Rxd
Ro
Glass (pg)
MB Er. C/.)
6119.00
2.08
2.00
6.60
—
290.00
2.00
200.30
1.50
55.30
45.56
20.26
126.53
77.50
25.28
8.77
82.56
33.54
49.02
9.73
-15.85
6119.00
2.00
2.00
6.60
—
560.00
2. 00
500.00
1.50
73.74
58.78
26. 10
65.36
25.64
31 . 29
7.66
47.25
7.53
39.72
16.54
-18.04
6119.00
2.00
2.00
6.80
—
1000.00
2.00
1000.00
1.50
92. 17
75.23
23.60
51.63
20.39
51.57
10.90
40.66
9.42
31.24
13.23
-16.95
-------
TABLE 34. SEDIMENT CONCENTRATION
Sediment = Montmorillonite
Time of Adsorption = 2 hr.
Aqueous Phase = Supernatant
Time of Desorption = 1.5-5 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma Cng/1)
Ta Chr>
Md (ng/1 )
Td
Ci
CTa
-fc * % ^
ca \ ng/ i /
Ra
Rxa
CTd
Rxd Cng/g)
Ro (ng/g)
Glass
-------
TABLE 35. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Saginaw
Time of Adsorption
Bay Station 50
= 2 hr.
Aqueous
Time of
Phase = Distilled Water
Desorption = 1.5 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta
Ci (ng/1)
CTa
Ca
Ra
Ro ( Tig/g >
Glass
5239.00
2.00
1.00
5.50
--
50.00
2.00
50.00
1.50
18.07
16.24
7.89
167.17
93.32
8.35
2.92
108.45
34.60
73.86
14.38
-2.14
4189.00
2.00
1.00
6.88
—
100.08
2. 00
100.00
1.50
14.75
14.37
4.84
95.32
26.51
9.23
1.52
77. 11
8.38
68.81
2.87
-0.60
5249.00
2.00
1.00
6.80
—-
100.08
2.00
100.00
1.58
33.51
30.86
10.90
199.67
84.70
19.96
4.76
151.97
37.01
114.96
6.98
-5.81
6079. 30
2.08
1.00
6.25
——
280.00
2. 00
200.00
1.50
--
65.61
18.97
233. 18
71.55
46.49
8.07
192.08
30.45
161.63
14.23
— -
5239.86
2.00
1.00
6.38
•— —
288.08
2.80
280.00
1.50
45.17
40.41
9.88
152.63
39.56
30.27
4.25
138.09
17.02
113.07
11.83
-7.93
4189.00
2.00
1.00
6.50
•« •»
500.00
2.00
508.08
1.58
73.74
67.13
18.31
113.64
11.10
56.69
3.52
186.33
3.79
102.54
7.28
-7.98
-------
TABLE 35. SEDIMENT CONCENTRATION
Sediment = Saginaw Bay Station 50
Time of Adsorption = 2 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 1.5 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (MS/I)
Ta
(Id Ois/1 >
Td
Ci
CTa Cns/l)
Ca
Rxa (113/3)
CTd Cns/l >
Cd (ng/l >
Rd ( T> 3 ••' 3 )
Rxd (ns/3>
Ro ( T13/3 ?
Glass
MB Er. <5s>
5249.60
2.80
i.ee
5.35
— —
ie.ee
2.00
10.00
1.50
9.31
9.04
5.82
322.69
247.30
3.21
1.72
148.72
73.33
75.39
2.43
-0.24
5299.00
2.00
1.00
5.40
—
25.00
2.00
25.00
1.50
13.73
13.10
7.06
241.61
149.97
6.04
2.45
143.62
51.97
91.64
7.88
1.16
5239.00
2-.ee
i.ee
5.40
—
25.ee
2.ee
25.00
1.50
9.03
8.09
4.57
140.63
198.59
3.47
2.36
44.51
102.47
-57.96
5.35
-4.53
5249.00
2.00
1.00
5.40
--
30.00
2.00
30.00
1.50
14.89
14.32
7.51
227.02
147.52
6.81
2.78
134.16
54.66
79.50
5.79
0.03
4189.00
2.00
1.00
5.60
—
se.ee
2.00
50. 00
1.50
7.37
6.72
2.89
76.69
46.13
3.80
1.26
50.72
20.16
30.56
2.40
-5.60
6879.98
2.00
1.00
5.69
—
50.00
2.00
50.00
1.50
--
41.22
20.00
424.36
304.67
20.86
8.44
248.31
128.62
119.69
9.51
— —
-------
TABLE 36. SEDIMENT CONCENTRATION
Sediment = Saginaw Bay Station 50
Time of Adsorption = 2 hr..
Aqueous Phase = Supernatant
Time of Desorption = 1.5-5 hr.
Date
Expt. Type
Aq, Phase
pH
Ionic
Ma (Mg/1)
Ta (hr)
Md
Td f.hr)
Ci Cng/1 >
CTa (rig/1 >
Ca
Ra (ng/g)
Rxa
CTd
R d ( T\ g •'' g )
Rxd
Ro ( Tvg/g ?
Glass
MB Er. <*>
6059.00
2.00
2.00
6.70
-.—
10.00
2.00
10.00
1.50
14.60
13.37
8. 10
526.58
482.61
. 5.14
2.95
219.60
175.63
43.97
5.28
-4.83
6059.00
2.00
2.00
6.80
• -~
25.00
2.00
25.00
1.50
14.60
17.72
10.98
269.77
168.05
6.68
2.99
147.52
45.80
101.72
2.91
23.34
6059.00
2.00
2.00
7.00
_-.
50.00
2.00
50.00
1.58
18.98
22.43
13. 14
185.78
127.40
8.91
4.04
97.53
39. 15
58.38
4.64
20.61
6049.00
2.00
2.00
6.90
— —
100.00
2.00
100.00
1.58
31.54
30.31
15.53
147.87
74.01
14.60
4.88
97. 13
23.27
73.86
6.90
-1.71
6849.00
2.00
2.00
6.90
— —
100.00
2.00
100.00
1.50
29.20
29.95
17.80
121.56
91.89
12.16
6.06
60.96
31.29
29.67
13.63
7.23
6289.96
2.9@
2.89
6.8©
•* M
200. 88
2.88
200.09
5.80
55.85
— —
— -
— —
«- —
28.11
5.76
111.77
_._
— —
5.30
— —
-------
TABLE 35. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Saginaw
Time of Adsorption
Bay Station
= 2 hr.
50
Aqueous Phase = Distilled Water
Time of Desorption = 1.5 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta
Md <>ig/1>
Td
Ci (rig/1 >
CTa
Ca
Ra
Rxa
CTd (ng/1)
Cd
Rd
MB Er.
4119.08
2.98
1.08
6.93
—
i030.ee
2.00
1000.00
1.50
19.17
18.53
1.96
16.56
1.26
16.56
0.77
15.80
0.49
15.31
3.97
-1.25
4119.00
2.Q0
1.00
6.90
--
1000.30
2.00
1003.00
1.50
76.66
76.26
7.39
68.37
3.09
68.34
2.20
66. 15
0.86
65.29
4.88
0. 12
4119.00
2.00
1.00
6.90
—
1600. 00
2.30
1600.00
1.50
153.32
151.45
13. 13
138.32
6.22
138.32
4.22
134. 10
2.00
132. 11
12.85
-0.38
-------
TABLE 37. SEDIMENT CONCENTRATION
Sediment = Montmorillonite
Time of Adsorption = 24 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 24 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta (hr)
Md 0-13/1 >
Td
Ci
CTa
Ca
Ra
Rxa
CTd
Cd <
Rd (
Rxd (
Ro (
G1 ass
MB Er.
11069.00
3.00
11069.ee
3.e0
25.08
24.00
23.00
24.00
7.34
4.80
101.48
46.51
3.34
1:70
71.42
16.45
54.98
25.00
24.00
23.00
24.00
7.30
4.69
104.57
54.93
3.61
1.94
72.39
22.76
49.63
11069.00
9.94
5.59
87.05
90.56
3.06
1.86
26.60
30.11
-3.51
11069.00
3.00
11069.00
3.
10. 19
5.25
49.40
15.67
6.61
2.82
42.14
8.41
33.73
23.73
7.63
32. 19
12.75
15.33
3.76
25.72
6.28
19.44
11069.68
3,
58.00
24,00
45.00
24.00
100.00
24.09
90.00
24.09
500.08
24.00
450.00
24.00
1000.08
24.08
908.08
24.88
32.49
7.32
25.16
16.12
20.25
4.06
17.98
8.94
9.05
-------
TABLE 36. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Saginaw
Time of Adsorption
Bay Station
= 2 hr.
50
Aqueous
Time of
Phase = Supernatant
Desorption = 1.5-5 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta (hr)
Md Ong/1 )
Td (hr)
Ci (ng/l)
CTa Crig/1)
Ca Cng/V>
Ra (tig/g)
Rxa (ng/g> .
CTd (ng/1)
Cd (fig/ 1 )
Rd (ng/g>
Rxd (ng/g)
Ro (ng/g)
Glass (pg)
MB Er. <*/.>
6269.00
2.60
2.06
6.86
__
200.00
2.00
200.00
2.00
55.85
— —
. ~~
__
— -
39.13
6.77
161.81
__.
__
4.80
• — -
6269. 06
2.06
2.66
6.75
— —
260.60
2.06
206.00
2.00
55.85
--
—
—
--
40.90
5.25
178.28
—
--
21.71
-•-
6279.06
2.60
2. 00
6.75
—••
200.00
2. 60
200. 06
4.66
54.21
—
—
—
—
30.00
5.08
124.57
—
—
7.69
—
6089.00
2.60
2.00
7.65
*» ••
560.60
2.60
506.00
1.50
96.56
96.35
16. 12
160.45
23.88
80.03
6.77
146.61
10.03
136.57
10.27
6.85
6999.ee
2.66
2 A /%
.00
7.05
"""*
1000.00
2.00
1000.00
1.50
193.11
196.72
22.85
167.88
11.78
167.54
7.55
159.99
3.89
156.09
17.19
-6.35
-------
TABLE 38. SEDIMENT CONCENTRATION (cont'd)
Sediment = Montmorillonite Aqueous Phase = Phosphate Buffer
Time of Adsorption = 2-4 hr. Time of Desorption = 1.5-4 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma
Ta (hr>
Md
Td Chr>
Ci (ng/1>
CTa
Ca
Ra
CTd Cn9/l>
Cd
Rd (ng/g)
Rxd
MB Er. <*>
5049.00
1.00
8.00
7.25
5.90
1090.00
4.06
—
—
52.38
50.26
11.55
38.71
—
--
—
--
•
—
15.49
-1.10
-------
TABLE 38. SEDIMENT CONCENTRATION
Sediment = Montmorillonite
Time of Adsorption = 2-4 hr.
Aqueous
Time of
Phase = Phosphate Buffer
Desorption = 1.5-4 hr.
Date
Expt. Type
Aq. Phase
PH
Ionic
Ma (ng/1 )
Ta (hr>
Md
Td (hr>
Ci (ng/l>
CTa (ng/1 )
Ca (ng/1 >
Ra (ng/g>
Rxa
CTd (ng/1 >
Cd (ng/1 >
Rd (ng/g)
Rxd (ng/g>
Ro (ng/g>
Glass (pg)
MB Er. (':>
5049.60
1.00
8.00
7.25
5.90
10.00
4.00
—
--
—
11.25
6.87
437.66
—
--
—
—
--
--
6.90
--
5319.00
2.00
8.00
7.20
5.90
25.00
2.00
25.60
1.50
17. 16
15.90
8. 16
309.62
209.49
7.61
3.11
180.05
79.92
100. 13
3.68
-5. 17
5049.00
1.08
8. 90
7.25
5.90
100.00
4. 00
—
—
17.96
17.28
8.96
83. 17
—
—
—
—
—
—
7.57
0.41
5319.00
2.00
8.00
7.20
5.90
103.00
2.00
100.00
1.50
34.31
29.78
12.15
175.54
104.54
17,55
5.62
119.35
48.34
71.00
10. 18
-10.48
5189.09
1.00
8.00
7.25
5.90
200.00
4.00
—
—
33.99
30.78
9.71
105.31
— —
--
—
--
__
--
12.57
-5.75
5049.30
1.09
8.09
7.25
5.90
500.00
4.00
— -
--
37.42
30.78
10.68
40.20
— —
— —
--
--
— —
--
17.37
-13. 19
-------
TABLE 39. SEDIMENT CONCENTRATION
(cont'd)
Sediment = Silica
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma (ng/1)
Ta
Md (rig/1 >
Td (hr>
Ci (ng^l >
CTa (rig/1)
Ca (ng/1 >
Ra (ng/g>
Rxa (rig's)
CTd (ng/l>
Cd (ng/1 >
P. d ( n g / 3 /*
Rxd (ng/g>
Ro
Glass (pg>
MB Er. <*>
11149.00
3.00
1.00
—
«-
200.00
3.00
180.00
3.00
—
21.19
14.69
32.49
26.78
7.06
4.54
13.99
8.28
5.71
'--
—
11149.00
3.00
1.00
—
—
500.00
3.00
450.08
3.00
—
25.61
16.45
18.33
9.80
9.95
4.82
11.40
2.87
8.53
—
--
11149.80
3.00
1.08
—
—
500.00
3.00
450.00
3.00
—
26.87
15.44
22.85
18.22
9.55
4.87
10.38
5.75
4.63
—
—
11089.88
3.08
1.88
—
—
1000.00
3.00
900 . 00
3.00
—
47.93
22.85
25.08
17.74
19.75
7.74
13.34
6.01
7.34
—
—
11149.88
3.00
1.88
—
—
1000.00
3.00
900.00
3.00
--
33.22
22.21
11.01
5.69
10.42
4 . 58
6.49
1.17
5.32
—
—
11149.88
3.88
1.88
—
«...
1880.00
3.00
900.00
3.00
-_
33.22
22.21
11.01
5.69
10.42
4.58
6.49
1.17
5.32
—
—
-------
TABLE 39. SEDIMENT CONCENTRATION
Sediment = Silica
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr .
Date
Expt. Type
Aq. Phase
PH
Ionic
Ha
Ta
Md
Td
Ci 3/1>
CTa
Ca
Ra
Rxa
CTd (ri3/l>
Cd
Rd (ng/'g)
Rxd
Ro Cng^g)
Glass
MB Er. <*>
11089.00
3.00
1.00
.
—
20.08
3.00
18.30
3.30
—
13.18
10.22
147.84
134.25
3.83
2.90
51.72
38.12
13.60
-- .
—
11149.00
3.00
1.00
—
-.-,
20.08
3.00
18.00
3.08
—
12.38
9.49
144.19
109.43
3.89
2.73
65.91
31. 14
34.77
—
—
11149.00
3.00
1.00
—
«_
20.88
3.88
13.88
3. 88
—
12.23
9.23
154.23
134.48
3.47
2.46
55.77
36.82
19.75
—
—
11089.08
3.08
1.08
—
--
68.03
3.80
54.83
3.08
—
28.39
18.81
159.71
156.30
5.84
3.18
49.35
45.94
3.41
—
—
11149.80
3.08
1.88
— »
—
68.88
3.88
54.88
3.00
—
15.00
13.64
72.71
66.38
4.64
3.21
26.36
28.84
6.33
—
— -
u089.ee
3.00
1.80
—
--
288.88
3.99
180.99
3.08
—
31.14
13.98
85.79
78.94
11.43
5.86
35.39
28.55
6.84
—
-_
-------
TABLE 39 , SEDIMENT CONCENTRATION
(cont'd)
Sediment = Silica
Time of Adsorption = 3 hr.
Aqueous Phase = Distilled Water
Time of Desorption = 3 hr.
Date
Expt. Type
Aq. Phase
pH
Ionic
Ma
Ta (hr>
Md (rig/I >
Td
Ci (rig/l >
CTa
Ca (ng/l >
Ra
Rxa (rig/'g}
CTd (ng/l)
Cd (ng/ 1 )
Rd 3/3>
Rxd
Ro (. ng^g ^
Glass Cpg>
MB Er. (V.)
11149.90
3.00
1.00
—
—
203.00
3.00
180.00
3.00
-»
21.19
14.69
32.49
26.78
7.06
4.54
13.99
8.28
5.71
—
—
11149.00
3.00
1.00
— —
—
500.00
3.00
459.00
3.00
—
25.61
16.45
18.33
9.80
9.95
4.82
11.40
2.87
8.53
—
—
11149.00
3,00
1.08
—
—
500.00
3.00
450.00
3.09
—
26.87
15.44
22.85
18.22
9.55
4.87
10.38
5.75
4.63
• —
— .
u089.ee
3.00
1.00
—
—
1000.00
3.00
900.00
3.00
—
47.93
22.85
25.98
17.74
19.75
7.74
13.34
6.01
7.34
--
—
iii49.ee
3.00
1.08
—
—
1000.00
3. 00
900.00
3.00
--
33.22
22.21
11.01
5.69
10.42
4.58
6.49
1.17
5.32
—
—
iii49.ee
3.80
i.ee
--
—
1880.00
3.08
900.80
3.08
—
33.22
22,21
11.01
5.69
10.42
4.58
6.49
1. 17
5.32
—
—
-------
TABLE 40. RESUSPENSION EXPERIMENT
Sediment = Saginaw
Bay Station //50 Mass = 55-220 mg/ £ Aqueous Phase =
Distilled Water
Ha
Ca (ns/l)
Ra
tra <1/k3>
M rs (H3'1>
CT rs
Ca rs (tig/' >
Ra rs <.Ti9''9>
Ro rs
iix rs ( l-'ka.-1
Md 3'l>
Cd
R d \ TI 3 / 3 )
Ro d (n3''3>
'.txd
Glass
MB error (.'i>
55.ee
80.91
41.20
722.00
17523.75
--
—
—
— -
—
— -
18.72
888.85
1027.83
—
__
35.69
•••
-»—
55.00
73.91
41.66
5S6.30
14071.85
—
—
--
--
— •
-._
19.32
790.24
966.61
•
--
33.06
~~
_..
55.00
76.05
37.24
705.57
18944.55
—
—
—
—
—
—
19.82
534.22
339.34
9833.24
—
25.73
—
— —
55.00
79 . 83
41.75
692.36
—
220.00
180.49
104.61
344.92
—
--
220.00
81.48
15.88
298.20
289.89
526.05
——
— —
ss.ee
72. 68
37.07
647.43
--
22e.ee
184.85
58.32
575.17
—
226.00
106.02
16.93
404.98
335.37
4112.06
--
— —
ss.ee
74.54
38.07
663.19
--
22e.ee
168.25
70.87
442.65
—
--
22e.ee
102.84
15.25
398.12
385.91
800.76
__
— «
-------
TABLE 41. RESOSPENSION EXPERIMENT
Sediment = Saginaw
Bay Station #50 Mass = 220-880 mg/2. . Aqueous Phase =
= Distilled Water
Ma (Mg/1)
CTa (irg/1 >
Ca (ng/1 >
Ra (ng/3)
•ira (I/kg)
M rs (ng/1 >
CT rs
Ca rs
Ra rs
Ro rs (ng/g)
•Jrx rs
Md (ns/l>
CTd
Ro d (.ng/g)
vrxd (I/kg)
Glass
-------
TABLE 42. RESUSPENSION EXPERIMENT
Sediment = Saginaw Bay Station #50 Mass = 55-1100 mg/£
Aqueous Phase
= Distilled Water
Ma
CTa (Tia^l >
Ca
fra Cl/'kg)
M rs Gi3''l >
CT rs I'ng-'l >
Ca rs
Ra rs
Ro rs Cng/3>
ftx rs Cl.-'kg>
Hd Cngxl)
CTd
/*- 1 "* j ^ V
Cd *.ng/l ,'
Rd
'iixd
Glass
MB error (':>
55.00
58.01
28.63
534.18
13666.61
—
—
--
--
— —
__
5.22
72.57
--
19723.43
57.82
37.72
61.46
11.16
55.06
58.71
30.55
512.03
16758.90
—
—
—
--
--
—
4.21
50.20
22.77
16013.56
57.82
37.72
82.52
14.77
55.00
59.06
30.45
520.16
17083. 19
—
—
—
—
--
—
4.23
51.19
—
1,7889.87
57.82
28.81
38.63
-0.37
55.09
57.12
29.77
497.28
--
1100.00
622.03
84.80
488.39
—
--
1038.89
395.04
17.41
363.49
331.21
1853.44
250.82
-2.30
55.99
55.66
29.26
486.84
—
1106.80
578.47
74.41
458.24
—
—
1838.89
337.43
13.54
311.77
279.19
2466.32
298.35
-7.76
55.80
55.61
27.51
516.92
—
1188.88
599.44
63.56
487.16
—
—
1038.89
357.76
14.61
336.25
283.43
3265.37
328.99
-9.88
-------
TABLE 43. DILUTION EXPERIMENT
Sediment = Montmorillonite
Mass = 1100
mg/£
Aqueous Phase = NaHCO_ Buffer
Ma
CTa
Ca (ng-'l)
Ra
tra < 1 .-'kg >
M dl Cng.'1>
CT dl
Ca dl Cr.g/1 )
Ra dl
Ro dl (Tis/g)
•«x dl i'l/koj>
Hd (ns.'l)
CTd Cng/l>
Cd (. ng-x 1 )
Rd
Ro d
'rxd < 1 'kgvj
Glass
M P. o r- f- .-• »•>• ( *.-' j
iiae.ee
74.28
22.76
46.83
2057.34
_-
—
—
—
—
—
990.00
48.56
9.74
39.61
33.06
672.31
29.46
-7.83
iiee.ee
77.61
18.74
53.52
2855.56
_..
--
«• •*»
--
—
--
990.00
55.41
8.94
46.95
39.54
828.43
8.12
-7.91
1100. 00
78.21
23.23
49.99
2152.24
—
—
—
—
—
—
990.00
50.13
8.45
42.10
36.74
633.77
13.02
-9.83
uee.ee
80.92
—
--
--
660.00
48.18
14.13
51.59
_«
13827.56
594.00
27.46
5.02
37.78
30.18
1515.72
6.36
-9.91
iiee.ee
72.69
-.—
--
--
66e.ee
44.78
15.89
43.79
58.69
--.
594.00
27. 10
6.25
35.10
29.47
901.11
6.13
-12.34
iiee.ee
77.57
— —
—
__
6se.ee
50.51
15.48
53. 07
24.94
1316.61
594.ee
25.83
5.92
33.52
21.43
2843.52
5.82
-il.33
-------
TABLE 43.(cont'd) DILUTION EXPERIMENT
Sediment
= Montmorillonite
Mass = 1100
mg/A
Aqueous Phase
= NaHCO- Buffer
Ma <
CTa <
Ca <
Ra <
ft a < 1
M dl
CT dl
Ca dl
Ra dl
Ro dl
ITX dl
Md (
:Td (
Dd <
iiee.ee
r>9/1 > 77.63
ng/l >
Ttg/9>
/kg)
440.60
(ng/1) 33.61
48.52
4.50
f i cj / 9 > 34.36
( n 9 •-' 3 ^>
1xk3>' 1822.81
3.16
ror Oi> "*'7* ^^
nee.ee
78.26
—
—
--
440. 0e
34.27
12.11
50. 36
49.83
43.73
396.00
18.74
4.44
36.09
27.83
1860.08
3.91
-6.65
iiee.ee
75.46
-—
—
—
446.00
31.72
12.35
44.02
59.69
—
396.00
20.09
5.00
38. 11
34.09
803.99
6.84
-6.75
iiee.ee
78.58
--
—
—
275.00
2'1 . 77
7.34
50.66
49.82
107.09
247.50
11.56
3.17
33.89
22.52
3588^54
6.19
-6.68
iiee.ee
78.34
— —
—
—
275.88
22.03
8.19
50.34
58.15
23.14
247.50
12.88
3.51
37.83
28.43
2676.51
2.Q3
-5.45
1108.08
78.49
— —
—
—
275.ee
22.06
7.39
53.36
39.78
1838.17
247.50
14.61
4.20
42.07
27.15
3547.22
5.07
-3.77
-------
TABLE 43. (cont'd) DILUTION EXPERIMENT
Sediment = Montmorillonite
Mass = 1100 mg/X, Aqueous Phase = NaHCO_ Buffer
Ma
CTa (ng/l>
Ca
Ra (ng/9>
'ara (l/kg>
11 dl
CT dl
Ca dl Cr.g/1 >
Ra dl
Ro dl (ngxg)
•'ay, dl
Md (MS/I >
CTd (na/O
Cd (n3'"l >
Rd (113/3)
Ro d
MB error <5j)
1103.00
78.45
--
—
—
118.88
18.23
4.55
51.68
49.88
555.19
99.88
5.23
2.81
32.52
17.45
7499.67
3.29
-5.55
1100.00
86.42
. --
—
•w «•
110.38
11.24
5.17
55.16
55.78
—
99.88
5.80
2.55
32.91
11.33
8475.58
2.92
4.17
1183.88
78.25
.
—
--
118.33
11.55
5.80
52.24
48.91
573.18
99.88
6.89
2.80
41.26
35.49
2886.28
1.98
-3.47
-------
TABLE 44. DILUTION. EXPERIMENT
Sediment = Saginaw
Bay Station #50 Mass = 1100 rng/H Aqueous Phase = Distilled Water
Ma <
CTa <.
Ca <
Ra <
•Jra <1
M dl
CT dl
Ca .dl
Ra dl
Ro dl
jx dl
Md (
CTd (
Cd <:
Rd (.
Ro d
•irxd <
MS"' I >
nsxl >
ns'l >
n3/s>
.-'k3>
OJ/1 >
C1.-'k3>
W9/1 >
T>3/ 1 .^
Ti3""' I **
Ti 3 '' 3 j*
1 /ka>
1100.06
179.57
12.06
152.28
12623.56
—
--
—
__
_-.
—
990.00
189.72
5.05
186.54
216.34
—
1100.00
193,32
9.46
167.14
17668.08
—
—
—
--
-—
--
990.00
142.97
5.19
139.18
95.61
8401.67
1100 00
176.23
9.48
151.60
15996.99
—
—
— .
—
—
-_
990.06
143.41
4.93
139.39
123.86
3252.72
1100.00
138.42
-J.
—
—
660.00
101.06
8.71
139.93
218.59
594.00
80.33
4.28
123.04
116.55
2685.07
nee.ee
294.66
—
—
—
663.80
105.83
7.69
148.70
339.08
—
594.00
84.02
4.58
133.73
111.67
4812.50
nee.ee
176.20
—
' —
—
66e.ee
101.01
7.71
141.36
183.14
—
594.00
82.12
4.15
131.27
119.52
2832.63
Glass Cp3>
MB error
-------
TABLE 44Xcont'd) DILUTION EXPERIMENT
Sediment = Saginaw
Bay Station #50 Mass = 1100 mg/£ Aqueous Phase = Distilled Water
Ma
CTa
Ra
ira
M dl
CT dl
•Jrx dl vl.-'k3>
Md CM 3.-'! >
CTd
Cd
Rd
R o d
Glass
MB error (J;>
1188.88
174.72
—
—
—
440.00
72.27
6.55
149.38
150.91
—
396.06
54.53
3.82
128.06
98.22
7815.94
~~
— •>*
1188.88
215.97
—
—
--
440.00
69.15
6.22
143.01
329.26
—
396.00
59.68
4.24
139,98
133.50
1528.19
— —
— —
1108.80
224.52
—
—
—
440.00
74.15
13.21
138.49
225.74
—
396.00
51.48
4.20
119.37
110.46
2121.43
—~
_—
1188.88
186.61
—
—
—
275.88
45.42
8.68
133.87
171.59
--
247.50
56.28
4.53
209.09
292.87
--
——
— —
1188.88
195.55
—
—
—
275.88
45.40
6.44
141.65
187.04
--
247.50
34.84
4.62
122.09
72.43
10739.86
•• —
. - —
iiee.ee
171.97
— —
— —
—
275.08
67.11
5.88
222.66
96.14
21526.91
247.50
33.11
4.96
113.73
—
99999.80
*•» *»
— —
-------
TABLE AA, (cont'd) DILUTION EXPERIMENT
Sediment = Saginaw Bay Station #50
Mass = 1100 mg/fc Aqueous Phase = Distilled Water
Ma
CTa
Ca
Ra
ira
M d
CT
Ca
Ra
Ro
irx
Md
CTd
Cd
Rd
Ro
•irxd
<
1
d
d
d
d
d
d
1/k3>
]
]
}
1
]
<
(.
<
(
Tis-'l
tig/1
fig/3
Ti3-''3
I/kg
/ 1 >
/I >
/ 1 )
xc,>
>
>
>
>
>
1100.
179.
110.
31.
4.
245.
136.
23927.
99.
14.
3.
106.
00
53
00
83
82
53
23
92
Q8
19
68
21
s
Gl ass
MB
er
}/
f
k3>
pg>
ror <.':
^
j
99999.
__
— —
00
249.
110.
13.
4.
122.
254.
--
99.
13.
3.
101.
12.
24464.
•••••
— —
00
80
00
06
53
99
96
00
69
65
42
20
10
1100,
209.
110.
18.
5.
116.
198.
--
93.
12.
2.
102.
87.
5678.
— —
—
00
52
00
00
18
55
25
00
89
73
62
12
81
-------
TABLE 45 .DILUTION EXPERIMENT
.
Sediment = Saginaw Bay Station #50 Mass = 220 mg/£
Aqueous Phase = Distilled Water
Ma (ng'l)
CTa (Tig'l )
Ca (ng'l)
Ra (ng'g.)
ft a a 'kg)
M dl (ng'l >
CT dl (ng'T)
Ca dl (ng'l>.
Ra dl (ng'g>
Ro dl ( Tig's )
-irx dl (1'kg)
& A • * \ *
Md \M3'1 /•
CTd (ng'l)
Cd (ng'l>
Rd (ng'g)
Ro d (ng'g)
•irxd (1'kg)
Glass (pg>
MB error (':)
228.80
91.89
23.83
312.98
13589.53
—
—
—
—
—
—
198.00
66.41
8.88
290.59
273.82
1889.00
6.77
-1.51
220.00
94.66
23.78
322.20
13548.45
—
—
_-
—
. —
—
198.Q0
64.06
8.97
278.25
246.53
3535.15
4.17
0.32
220.80
92.91
23. 33
316.29
13557.06
—
—
—
--
—
—
198.00
64.32
9.10
278.87
250.26
3144.52
6.03
-1.74
228.88
91.38
—
—
_->
132*00
55.71
15.63
303.24
367.56
—
118.88
34.85
6.38
239.63
196.00
6839.74
7.35
-3.30
228.88
94.75
-._.
—
—
132.88
57.89
14.76
320.68
377.73
—
118.80
37.94
7.08
268.44
206.07
7762.04
8.18
0.76
228.88
98.15
— —
— —
— —
132.08
55.99
14.77
312.32
245.15
4549.23
118.80
37.81
6.66
262.28
220.98
6186.18
4.23
-1.85
-------
TABLE 45T(cont'd) DILUTION EXPERIMENT
Sediment = Saginaw Bay Station #50 Mass = 220 mg/£
Aqueous Phase = Distilled Water
Ma
CTa
Ca <*9-'l>
Ra (tig^S^
M» % ^ * . ^ ^
dl i. M9/1 y
CT dl
Ca dl
Ra dl Cri3/3>
Ro dl
•;rx dl n/kg>
Md Cnoj/n
CTd
C d ( TI 3 s \ )
Rd (r. 3 •''£!>
Ro d (ri3-'3>
^Tx-s'd n.-'k3>
Glass Cp9>
MB error O;>
220.06
103.44
' --
88.00
36.79
10.71
296.35
2142.30
—
79.20
24. 12
6.63
228.48
141.16
14497.86
12.41
6.17
220.06
92.61
—
—
88.00
38.20
11.24
306.41
358.01
—
79.20
22.81
5.65
216.68
125.95
16061.05
4.95
-2.21
220.00
98. 70
—
-_
88. 00
45.93
12.27
382.47
141.16
19665.01
79.20
25.45
6.60
237.95
69.65
25492.37
3.68
6.08
22e.ee
87.12
—
-—
55.06
25.62
9.97
284.54
311.22
_..
49.50
14.42
4.38
204.35
143.44
14153. 13
16.81
-2.03
22e.ee
91.37
—
_«
55.ee
24.70
8.70
291.01
349.82
_-.
49.50
13.48
4.14
188.68
95.93
22425.05
3.94
-2.30
22e.ee
91.29
—
— —
55.00
23.60
7.70
289.09
373.98
_«
49.50
14.37
4.04
208.70
119.99
21964.28
2.48
-2.63
-------
TABLE 45.(cont'd) DILUTION EXPERIMENT
Sediment = Saginaw
Bay Station
#50
Mass = 220 mg/fc Aqueous Phase = Distilled Water
Ma
CTa
Ca
CT dl 3'1>
Ca dl
Ro dl
',TX dl
h * • x j ^ V
Md u-ig.' 1 >
CTd
j*. i ,. f m v
W Cl Mi 3 •* ' '
Rd
Ro d (riS'-'s)
frxd (l-'k3>
Glass
MB error <^>
220.00
91.55
—
—
22.00
9.62
5.09
206.1?
393.60
— -
19.80
5.03
2.40
132.93
67.50
27259.69
1.96
-1.77
220.63
94.77
—
--
22.00
11. 11
6.00
232.05
382.15
— —
19.80
5.59
2.22
170.26
133.95
16346.4?
4.03
3. 11
220.06
89.79
~~ '
— —
22.80
10.17
5.46
214.13
370.02
*~~
19.80
5.1?
2.6?
126.20
42.29
31467.52
3.95
-2.68
------- |