United States
Environmental Protection
Agency
Health Effects
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S1-84-025 Jan. 1985
4>EPA Project Summary
Isolation and Concentration of
Organic Substances from
Water Using Synthetic Resins
and Graphitized Carbon Black
E.S.K. Chian, J.H. Reuter, and M. Giabbai
This study describes the evaluation of
an integrated adsorption system for the
isolation and concentration, not less
than 50 fold, of 22 specified organic
compounds at /ug/L levels. The system
was first developed and tested on a
laboratory scale and then adapted for
the processing of large volumes of
water (pilot scale).
With this system, dissolved organics
were separated into fractions by adsorp-
tion onto Amberlite XAD-8, AG MP-50
cation exchange resin, and graphitized
carbon black (GCB) under varying pH
conditions. Model compounds used in
the evaluation covered a broad spectrum
of physical and chemical properties, so
that comparisons between this and
other concentration/isolation tech-
niques could be made.
A substantial effort was made to
establish analytical techniques for
monitoring model compound recovery
in the proposed system. Quantification
was performed using GC, GC/MS and
HPLC.
In the laboratory-scale studies, 15 of
the 22 model compounds exhibited
recoveries varying from 30% to 90%. In
general, poorer recoveries were observed
for the more volatile, polar, or water
soluble compounds. Recoveries of
model solutes appeared to be virtually
unaffected by the presence of humic
acid (2 ppm) and inorganic salts.
The results of the final pilot experi-
ments with five 100-L test solutions
confirmed those of the bench-scale
studies. However, some difficulties
with column flow and lower recoveries
were encountered. These problems
were attributed to humic acid break-
through on the XAD-8 column and the
subsequent coprecipitation of calcium
salts, humic acid and possibly other
organic substances at high pH.
This Project Summary was developed
by EPA's Health Effects Research Labo-
ratory. Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project report orderingin information at
back).
Introduction
In recent years, organic waterborne
pollutants have been identified as
potential health hazards Epidemiological
studies have suggested a relationship
between the ingestion of these pollutants
in drinking water and carcinogenic and
teratogenic effects. Although hundreds
of organic compounds have been detected
and quantified in drinking water, the
majority of organic material, i.e. the
nonvolatile fraction-, cannot be identified
using currently available technology.
Therefore, the direct concentration/isola-
tion of organic contaminants in aqueous
samples for biological testing offers a
practical solution to the determination of
health risks associated with trace organic
contaminants.
The Health Effects Research Laboratory
has funded several independent studies
in an effort to determine the effectiveness
of different isolation/concentration
techniques. Systems or techniques
investigated were reverse osmosis,
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vacuum distillation, solid adsorbents, and
supercritical fluid C02 extraction. The
necessity of concentrating aqueous
samples before an assessment of potential
health risks can be made, stems from the
lack of sensitivity for existing in vitro and
in vivo biological test systems.
The following criteria must be considered
when attempting to concentrate organic
substances from potable water for
biological testing: 1) the aqueous organic
concentrate prepared by the selected
concentration scheme should have the
same relative abundance of the individual
components as the original water sample;
2) introduction of artifacts and constituent
alteration by the concentration method
should be kept to a minimum; 3) altera-
tion of the organic constituents after
preparation of concentrates and before
biological testing and chemical analysis
must be avoided; 4) the effect of humic
material, which constitutes the bulk of
the organic fraction, on the recovery of
trace solutes has to be taken into account;
5) co-recovery of toxic inorganic constitu-
ents by the concentration scheme should
be avoided and 6) effect of chlorine
residual on the material used in the con-
centration scheme — resins, graphitized
carbon black, etc., must be assessed.
These considerations, as well as the
necessity for a comprehensive approach
toward the isolation and concentration of
dissolved organic carbon in water, led to
the investigation of an isolation scheme
in which organic compounds with different
functionalities and sorption parameters
were separated and concentrated. A
mixture of 22 model compounds proposed
by the Health Effects Research Laboratory
was chosen for process evaluation. The
proposed isolation scheme was first
tested on a laboratory scale and then
adapted for processing several hundred
liters of water.
Procedur.e
Preparation of Model Compound
Test Solutions
As shown in Table 1 stock solutions of
quinaldic acid, glycine and glucose were
prepared in organic-free water (OFW).
Humic acid was dissolved in 0.02N
NaOH, 5-chlorouracil in 2N NH4OH, and
the remaining compounds in methanol
except for phenanthrene; 1-chlorodode-
cane; 2,4'-dichlorobiphenyl; and 2,2',5,5'
-tetrachlorobiphenyl. The spiking of the
test solution with the latter compounds
required successive solubilization and
evaporation in hexane and acetone prior
to the addition of OFW. The test solutions
for the other model sol utes were prepared
by simply diluting the required volume of
stock solutions in OFW containing 70
ppm NaHCOs, 120 ppm CaS04 and 47
ppm CaCI2-2H2O. The salts were included
to simulate inorganic levels found in a
typical drinking water.
Preparation of Resins and
Graphitized Carbon Black
(GCB)
The XAD-8 resin was air-dried and
sieved through 20- and 50-mesh size
sieves, sequentially. The 20-50 mesh size
fraction was washed and then stored in
0.1 N NaOH for 24 hours. The remaining
fines were removed by decanting. The
resin was soxhlet - extracted for 24 hours
each with acetone, hexane and methylene
chloride. The cleaned resin was stored in
methanol. In the laboratory-scale experi-
ments, glass columns (200 x 13 mm I.D.)
with Teflon stopcock were packed with 15
mL bed volumes (B.V.) of XAD-8. In order
to process 100 L of test solution, larger
glass columns (500 x 34 mm I.D.) with
250 mL B.V. of XAD-8 were prepared.
Immediately before passage of the test
solution, the resin bed was rinsed with
0.1N NaOH, 0.1NHCI and OFW in order to
eliminate methanol and stabilize the
column. The samples were processed at a
flow rate of approximately 15 B.V./hour.
AG MP-50 (20-50 mesh, H+-form) was
purified by Soxhlet-extraction with
methanol (24 hrs) and stored in fresh
solvent. Glass column dimensions were
the same as for the XAD-8 resins in both
the laboratory-scale and 100-liter pilot-
scale experiments. Just prior to use, the
AG MP-50 resin was rinsed with 3N
NH4OH, until breakthrough of ammonia
was observed, followed by four B.V. of 2N
HC1, and finaHy with OFW until the
effluent was Cl~ free.
GCB was washed with acetone, methy-
lene chloride, and OFW prior to column
packing. Since this material is fragile,
care was taken to avoid any mechanical
stress which might cause particle rupture
and consequently generate flow-rate
problems. In the laboratory-scale experi-
ments, 200 mg of GCB were packed in a
glass column (200 x 5 mm I.D.) with a
Teflon stopcock. In the large scale
experiments, 10 g of GCB were packed in
a glass column (300 x 35 mm I.D.) fitted
with a Teflon rotaflo valve.
Isolation Scheme
The flow schematic of the isolation
scheme devised and evaluated in the
bench-scale phase of the study is shown
in Figure 1. The test solution was first
acidified to pH 2 and passed through the
XAD-8 column by gravity flow at a rate of
approximately 15 B.V. hr~1. The final
portion of test solution was displaced
from the resin with 1 B.V. of 0.01 N HCI
rinse and combined with the initial
column effluent. Next, the hydrophobic
acid fraction was desorbed with 0.25 B.V.
of 0.1N NaOH followed by 1.5 B.V. of
OFW.
Following elution of the hydrophobic
acid fraction, the XAD-8 effluent plus
rinse was adjusted to pH 10 with 1N
NaOH. This solution was then recycled
through the XAD-8 column at a rate of
approximately 15 B.V. hr~1 followed by
2.5 B.V. of OFW which was combined
with the test solution effluent. The
hydrophobic base fraction was eluted
with 0.25 B.V. of 0.1 N HCIfollowedby 1.5
B.V. of 0.01N HCI. The hydrophobic
neutral fraction was recovered by transfer-
ring the XAD-8 resin from the column to a
separatory funnel and extracting with
three 50 mL aliquots of methylene
chloride.
The test solution effluent, which
should now contain only hydrophilic
substances, was readjusted to pH 2 with
1N HCI and passed through the AG MP-
50 cation exchange column at a flow rate
of approximately 15 B.V. hr~V Desorption
and elution of the hydrophilic base
fraction was accomplished with 1N
NH4OH. Finally, the test solution effluent
containing primarily hydrophilic acids
and neutrals, was adjusted to pH 7 and
passed through the graphitized carbon
black column at a rate which allowed a
0.5-minute contact time. Elution of the
adsorbed hydrophilic solutes was accom-
plished with methylene chloride.
In the pilot-scale experiments, two
XAD-8 columns, one for each pH condition
were used, rather than recycling the pH-
adjusted effluent through the same
column. Extraction of the hydrophobic
neutral fraction from XAD-8 was accom-
plished by shaking the resin with methylene
chloride in the glass column.
Results and Discussion
Bench-Scale Studies
The original scheme proposed for the
trace enrichment of model organic
solutes consisted of Amberlite XAD-8
resin, AG MP-50 cation exchange resin
and Duolite A-7 anion exchange resin in
series followed by reverse osmosis.
However, initial testing indicated that
Duolite A-7, as utilized in this system, did
not significantly increase model solute
recovery and it was eliminated from
further study. Reverse osmosis was
shown to recover a substantial amount of
hydrophobic neutrals.
Table 1 shows the average recoveries
obtained from six repetitive experiments
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Water Solution pH 2
1
I-
XAD-8
(2) Elution with NaOH
(4) Elution with HCI
(5) Extraction with CH^CL^
(3)
Water Solution pH 10
J
^> Hydrophobic Acids
^» Hydrophilic Bases
-^ Hydrophobic
Neutralis
Water Solution pH 2
AC MP-50
(71 Elution with NH
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hydrophobic neutral fraction was presumed
lost by the volatilization associated with
the concentration and analytical proce-
dures.
Because numerous model soluted
were only partially adsorbed on XAD-8
and AG MP-50, adsorption studies were
also conducted with graphitized carbon
black (GCB). Recovery data for this
adsorbent are provided in Table 2.
Pilot-Scale Studies
The average recoveries of the model
compounds from five 100-L batches of
test solution are shown in Table 3. The
majority of the model compounds demon-
strated lower recoveries than those
observed in the bench-scale experiments.
Part of the failure was attributed to humic
acid breakthrough on the XAD-8 column
at pH 2. This breakthrough of humic acid
resulted in the formation of solid calcium-
humate upon adjustment of the effluent
to pH 10. This affected column flow
characteristics and may have caused
some coprecipitation of other model
solutes.
Incomplete humic acid adsorption was
attributed to insufficient quantities of
XAD-8. The decision to utilize a resin bed
Table 2. Recovery of Model Compounds on Graphitized Carbon Black
Compound
2,4-Dichlorophenol
Quinoline
Isophorone
1 -Chlorododecane
2,4'-Dichlorobiphenyl
2,2',5,5'-Tetrachlorobiphenyl
Anthraquinone
bis-(2-Ethylhexyl)phthalate
Phenanthrene
Caffeine
Furfural
MIBK
Desorbed from GCB
115.2
97.5
16.3
51.2
48.6
54.1
92.1
51.1
114.0
92.1
NF
6.7
Extracted from
water after GCB
NF
NF
92.4
NF
0.9
37
NF
64.3
NF
NF
26.0
65.5
NF = Not found
volume of 250 ml, in the pilot study, was
based on the following factors: known
capacity of XAD-8 for aquatic humic
material, the requirement of a 50-fold or
greater concentration of solutes and a
desire to minimize resin artifacts. Unfortu-
nately, the capacity of XAD-8 resin for
commercially available humic acid (soil
origin) differed appreciably from the
reported values for aquatic humic material.
The low recovery of 2,6-di-tert-butyl-4-
methylphenol was attributed to partial
oxidation, since 2,5-bis-cyclohexadiene,1,4-
dione-bis(1,1 -dimethyethyl) was tentative-
ly identified in the test solution and in the
hydrophobic neutral fraction. Further
evidence was obtained from the observed
continuous decrease of this compound in
the organic standard solution used for GC
analysis. Glycine was also found in
considerably lower amounts in the
hydrophilic base fraction, since the
amount of Ca++ ions present in 100 L of
test solution exceeded the exchange
capacity volume of the AG MP-50 resin
(1.7 meq/mL).
Conclusions
1. A method for the isolation and con-
centration of 22 model organic
compounds from water (Table 1)
was developed. The process separ-
ates the organic solutes into several
fractions based on adsorption on
Table 3. Average Recovery of Model Compounds From Pilot-Scale Study
% Recovery (S.D.)
Compound
Stearic Acid
Trimesic Acid
2,4-Dichlorophenol
Quinaldic Acid
Isophorone
Biphenyl
1 -Chlorododecane
2,6-di-tert-Butyl
4-Methylphenol
2-4'-Dichlorobiphenyl
2,2', 5,5'- Tetrachlorobiphenyl
Anthraquinone
Phenanthrene
bis(2-Ethylhexyl)
phthalate
Glucose""
Furfural
Quinoline
5-Chlorouracil
Caffeine
Glycine
Humic Acids
Chloroform
MIBK
ND - Not Detected
NA = Not Analyzed
Hydrophobic Acid Hydrophobic Base
Fraction (XAD-8) Fraction (XAD-8)
7.819.1)
47.6(19.8)
11.3(11.3)
ND ND
2.0 (1.9)
61.6(25.6)
34.0(4.6)
Hydrophobic Neutral
Fraction (XAD-8)
37.4 ( 3.4)
568(14.4)
94.7 ( 3.5)
8.4(12.6)
70.1 (10.3)
64.8(14.7)
59.9 (13.8)
38.6 (6.9)
60.9(178)
ND
ND
3.3 (27)
Hydrophobic
Base Fraction GCB
(AG MP-50) Fraction
3.9 (7.3)
ND
27.8(10.7)
43.2 (28.4)
4.8(1.9)
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Amberlite XAD-8 resin, AG-MP-50
cation exchange, and graphitized
carbon black under varying pH
conditions. Out of the 22 model
compounds evaluated, the following
fifteen compounds showed average
recoveries between 30% and 90%:
stearic acid; trimesic acid; isophor-
one; biphenyl; 1-chlorododecane;
quincline; 2,4'-dichlorobiphenyl;
2,6-di-tert-butyl-4-methylphenol;
2,2',5,5'tetrachlorobiphenyl; anthra-
quinone; phenanthrene; bis-(2-
ethylhexyOphthalate; caffeine; humic
acid; and glycine.
2. The fractionation system in general
gave unsatisfactory recovery results
for the more polar, water soluble
and/or volatile solutes 5-chloroura-
cil, glucose, quinaldic acid, furfural,
chloroform, and methyl isobutylke-
tone. The lone exceptions were
glycine and trimesic acid which
were recovered on the cation
exchange resin (AG MP-50) and
XAD-8 resin, respectively.
3. The majority of the compounds
displayed a 15% or greater decline
in adsorption in the pilot-scale
study, as compared to the bench-
scale experiment. This difference
presumably resulted from undersized
resin beds.
4. The adsorption of the model solutes
was found to be unaffected by the
presence of humic acid.
5. The introduction of artifacts by the
resins appeared to be within reason-
able limits (only three impurities
were detected at levels comparable
to that of the model compounds).
6. The presence of a 2 ppm free
chlorine residual carried through
the adsorption scheme did not
produce any major GC detectable
artifacts.
Recommendations
1. To improve mass balance determin-
ations, future evaluation studies
should include the use of radiolabeled
model compounds where possible.
2. Aquatic humic acid, isolated from a
major drinking water source, should
be substituted for commercially
available humic acid in future
method evaluations, despite the
increased cost.
3. Both resin capacity (batch studies)
and column breakthrough data
should be used to establish column
dimensions for processing large
volumes of test solutions. Where an
increased concentration factor is
necessary, the use of multiple
column concentrations should be
evaluated since solute breakthrough
is a function of the column distribu-
tion coefficient as well as resin
capacity.
To provide increased recovery of a
broader spectrum of organic com-
pounds, resin columns should be
used in combination with reverse
osmosis.
U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/10764
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E. S. Chian. J. H. Reuter. and M. F. Giabbai are with Georgia Institute of
Technology, Atlanta, GA 30332.
H. P. Ringhand is the EPA Project Officer fsee below).
The complete report, entitled "Isolation and Concentration of Organic Substances
from Water—Using Synthetic Resins and Graphitized Carbon Black," (Order No,
PB 85-125 672; Cost: $13.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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