&EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-216
September 1979
Further Characterization
of Sorbents for
Environmental Sampling
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide'range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-216
September 1979
Further Characterization of Sorbents
for Environmental Sampling
by
J. F. Piecewicz, J. C. Harris, and P. L Levins
Arthur D. Little, Inc.
Acorn Park
Cambridge, MA 02140
Contract No. 68-02-2150
T. D. No. 10601
Program Element No. EHB537
EPA Project Officer: Larry 0. Johnson
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington. DC 20460
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TABLE OF CONTENTS
Page
LIST OF FIGURES iv
LIST OF TABLES v
I. SUMMARY 1
II. INTRODUCTION 2
III. BACKGROUND 4
IV. APPROACH 6
A. Experimental Technique 6
B. Experimental Apparatus 7
C. Introduction of Sorbate Samples 13
D. Materials and Reagents 13
E. Matrix of Experiments 15
V. RESULTS 18
A. Effects of Major Combustion Gases 18
B. Comparison of Various Sorbents 22
VI. CONCLUSIONS AND RECOMMENDATIONS 35
VII. REFERENCES 36
APPENDIX A A-l
iii
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LIST OF FIGURES
Figure No.
1 Relationship Between Initial Retention
Volume Vi and v|
2 Gas Chromatographic Apparatus Used
to Determine V3
3 Moisture Generation System ^.1
A-l Incremental Surface Area Distribution A-2
(Desorption) XE-340
A-2 Incremental Surface Area Distribution A-3
(Desorption) XE-347
A-3 Incremental Surface Area Distribution A-4
(Desorption) XAD-8
A-4 Incremental Surface Area Distribution A-5
(Desorption) Charcoal Lot 104
A-5 Incremental Surface Area Distribution A-6
(Desorption) Charcoal Lot 106
iv
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LIST OF TABLES
Table No.
1 Sorbates and Suppliers Used in the Study 14
2 Sorbents and Suppliers Used in the Study 14
3 Experimental Matrix - Combustion Gas Studies 16
4 Experimental Matrix - Other Sorbent Studies 17
5 % Relative Humidity Compared to Column Temperature 18
at constant 10% Moisture (vol/vol)
6 Comparison of V for Dry and Low % Relative 19
Humidity Atmospheres in XAD-2
7 Comparison of Vg's for Sorbates at Two Different 20
Relative Humdities on XAD-2
8 Comparison of Vg's for Sorbates at Two Different 21
Relative Humidities on Tenax-GC
9 Comparison Data for Vg in Humid Atmospheres With 23
and Without Carbon Dioxide
10 Retention Volumes, Vg, on Charcoals Lots 104 and 25
106 for the Tested Sorbates
11 Comparison of Retention Volume, Vg, of the Charcoals 26
Lots 104 and 106 at Common Temperatures
12 Retention Volumes, Vg, on Silica Gel for the Tested 26
Sorbates
13 Retention Volumes, Vg, on the Ambersorbs XE-340 and 28
XE-347 for the Tested Sorbates
14 Comparison of Sorbents via the Retention Volumes 29
of the selected Sorbates at 20°C
15 Retention Volumes on XAD-8 of the Tested Sorbates 30
16 Specific Surface Areas, Ag, for Sorbents 32
17 Adsorption Coefficients, K^, on Resins at 20°C 33
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I. SUMMARY
In this work, elution chromatography was successfully used to study
the effects of combustion gases, carbon dioxide, water and the combined
effect of carbon dioxide and water on the retention volume of trace
level sorbates on XAD-2 and Tenax-GC. The retention behavior of XAD-2
is relatively unaffected by the combustion gases studied. Introduction
of water vapor led to Vg reductions of 0-4% for the non-polar sorbates
studied and 13-17% for the two polar sorbates. Carbon dioxide at 10%
(vol/vol) levels resulted in essentially no further decrease for XAD-2.
On the other hand, the VB values on Tenax-GC were reduced by 22-43% in
5
the presence of water vapor, and an additional 25% decrease was observed
when carbon dioxide was introduced.
Other sorbents have been investigated for collecting of volatile
and polar organics. The charcoals, Lot 104 and Lot 106, and the
Ambersorbs, XE-340 and XE-347, appear to be potential candidates for
this purpose. The charcoals and Ambersorbs show Vg values three to five
orders of magnitude higher than XAD-2 for non-polar sorbates. For
alcohols, the differences are one to three orders of magnitude. The
increased Vg's are only partially attributable to differences in surface
area. Based on this study, the order of preference in selection of sorbents
for collection of high volatile and polar organics, listed in order of
decreasing intrinsic affinity (KA), are: Charcoal Lot 104 > Ambersorb
XE-340 > Charcoal Lot 106 > Ambersorb XE-347 > XAD-8 > Tenax-GC > XAD-2.
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II. INTRODUCTION
In the past decade adsorbent-filled cartridges have found increased
use in the sampling of volatile and relatively non-volatile organic com-
pounds. This technique has been used for the study of source emission
levels, ambient air concentration levels and for the characterization of
occupational exposure. Sorbent sampling methods have been developed for
the characterization of both air and water media. The use of sorbents
for characterization of source emissions and, in general, for environ-
mental assessment studies, has been adopted by the Process Measurements
Branch by incorporation of a sorbent module in the EPA SASS train, in
support of this application, and in order to provide an extended quanti-
tative data base to guide in the application of this methodology,
Arthur D. Little, Inc., has been carrying out research in this area for
several years. This report represents the third in a series related to
the use of sorbents for environmental sampling. The first report '
covered a discussion of selection criteria used in choosing particular
sorbents for application and presented some preliminary quantitative evalu-
(2)
ation data for a variety of sorbents. The second report presented a
detailed study of the behavior of Tenax-GC and XAD-2 for a variety of
sorbents. That report demonstrated that a good correlation existed be-
T
tween the elution volume of a sorbate on a sorbent (V ) and physical
O
properties such as boiling point. The correlations generally were grouped
by chemical class type.
These quantitative studies have demonstrated that elution chromato-
graphy is an efficient means of providing quantitative data necessary to
make the evaluation and selection of the proper conditions for use of
sorbents in a variety of sampling applications. At the conclusion of the
latter study, several additional areas of research were identified.
These included:
1) A study of the effects of major combustion gases, water and
carbon dioxide, on the elution characteristics of sorbents.
2) Evaluation of other sorbents which might be more effective
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in the collection of more volatile species and more polar
chemical groups.
3) A study of the effect of other types of major components
on the elution characteristics of sorbents. An example
would be the effect of methane in a gasifier sampling stream.
4) A study of other sorbates such as organometallics.
The material in this report deals with items (1) and (2) listed
above. Studies of combustion gas effects have been continued on both
Tenax-GC and XAD-2. Each of these resins has particular value for
special sampling and analysis applications. Studies of other sorbents
have involved the following: charcoal Lot 104 and Lot 106, silica gel,
ambersorb XE-340 and XE-347, and XAD-8.
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III. BACKGROUND
Sorbent modules are frequently employed as one of a number of col-
lection devices or stages in a multi-purpose sampling device, such as the
/3\
EPA-SASS train. ' The SASS train sorbent trap is primarily designed to
capture organic species that have sufficient volatility to pass through
particulate filters upstream from the sorbent bed.
For several reasons, care must be taken in designing experiments and
interpreting results with sorbent traps. Very volatile gases are retained
poorly by most sorbent resins currently used in sampling devices. Other
species will "break through" the trap if the sampled volume exceeds the
volume or weight capacity of the sorbent.
The availability of data which describe the quantitative relationship
between sorbent, chemical species and sampling volumes allows the sampling
conditions to be specified so that reliable results may be obtained.
One of the more common methods of characterizing adsorbents is the
(4 5)
use of gas chromatography. Several reviews ' attest to the popularity
of this technique for thermodynamic and kinetic characterization of solid
surfaces. The retention time (volume) in a gas chromatography experiment
is directly related to the breakthrough volume that would be observed for
an organic adsorbate in a sorbent sampler. Thus, tabulations of chroma-
tographic retention data have intrinsic value to the chemist or engineer
designing a sampling experiment involving sorbent resins. These data
allow an estimate to be made as to the suitability of a particular ad-
sorbent for the source to be sampled, the time required until breakthrough
has occurred, and the amount of sorbent required to collect a sufficient
amount of analyte for analytical or biological testing.
The previously reported studies in this series on the subject
of sorbent traps have considered:
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• The retention characteristics exhibited by two specific
sorbent resins, XAD-2 and Tenax-GC, for a large variety
of compound types.
• Correlation of chromatographic retention volume data
generated by a sorbent trap exposure apparatus with
frontal analysis results.
• The relationship between the equilibrium adsorption
isotherm and the retention volume results obtained in
the low surface coverage region (i.e., Henry's Law region)
and its application to sorbent sampling device design.
• The relationship between elution and frontal chromato-
graphic approaches and the advantages and disadvantages
of the several chromatographic-based methods for determining
T
V , breakthrough curves (adsorption and desorption branches),
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adsorption isotherms, and weight capacity of the sorbent
trap.
• The effect of flow rate on retention volume, particularly
at face velocities similar to those corresponding to actual
sampling conditions.
T
• The correlation of elution volume (V ) data with sorbate
g
physical properties to aid in the prediction of break-
through volumes of other organic species.
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IV. APPROACH
A. Experimental Technique
The chromatographic method used in this study was that of elution
analysis. In elution analysis, a small quantity of adsorbate is in-
jected onto the sorbate cartridge in a very short time. The specific
T
retention volume, V , can be determined for a sorbate on a particular
O
sorbent from the resultant elution peak.
T
The specific retention volume, V , is the fundamental retention
o
constant in gas chromatography and reflects the effect of flow rate, pres-
sure drop, temperature, column void volume, and stationary phase weight
(volume or surface area) on the retention of an injected solute. Know-
T
ledge of the value of V allows one to estimate the retention volume of
O
a solute at another temperature or for a different sorbent cartridge
T
size. Thus, V determined from conventional gas chromatographic columns
o
can aid in design of sorbent sampling modules.
Specific retention volumes, which actually correspond to the 50%
breakthrough in an elution chromatography experiment, in this study were
T
computed according to the following formula, which defines V at the
O
temperature of the column oven in the chromatographic experiement. The
derivation of this equation has been given elsewhere.
T Jpc (tr - ta)
8 WA
T
Where V = specific retention volume for the adsorbate at column
^ (sorbent trap) temperature
F » flow rate of carrier gas at column temperature and pressure
t = peak maximum retention time
t - retention time for a completely non-sorbed solute
Si
W. » adsorbent weight
j = pressure correction
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T
The correspondence between V and the 50% breakthrough in an elution
o
chromatography experiment is illustrated in Figure 1. The actual break-
through of the sorbate begins to occur after V volumes of gas have passed
over the sorbent bed. However, V is not routinely determined, because
its value is flow rate dependent, shows a dependence on the packing
structure of the sorbent column, and is difficult to precisely locate on
T
the chromatogram. The specific retention volume V , on the other hand,
O
is easily located and is the only point on the chromatographic band cor-
responding to true thermodynamic equilibrium. A safety factor can be
built into any calculation of breakthrough volume to account for the dis-
T
parity between V and V_.
o
T
The specific retention volume, V , for a sorbate on a sorbent is
O
directly related to the equilibrium adsorption coefficient, K., so long
as the experiments are carried out a low sorbate concentrations (the
Henry's Law region). Under these conditions,
VI-K*A *s
T
where V = specific retention volume
*
K . = equilibrium adsorption coefficient
A° » adsorbent specific surface area
s
B. Experimental Apparatus
Figure 2 is a schematic of the basic apparatus used to determine
T ^2}
elution volumes, V , in this study and in work reported earlier.v '
g
Principal components of the apparatus are: the sorbent cartridge, the
gas chromatograph, and the pressure, flow and temperature measuring sys-
tems.
The sorbent cartridges were proportionally scaled down from the
typical cross-section of a SASS train sorbent resin canister. Stainless
steel tubing 9 cm long, 0.45 to 0.51 cm I.D., and 0.64 cm O.D., was used
to contain the resin. The sorbent cartridge was connected to two
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Volumt (Timt)
Figure 1. Relationship between Initial Retention Volume V and VT
X o
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Thermocouple
GM Chronwtogripri
.CvritrGn
InM Prmurt Gwigt
Figure 2. Gas Chromatographic Apparatus Used to Determine
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0.64 cm x 0.16 cm (1/4 in x 1/16 in) reducing unions drilled out to mini-
mize dead volume. The resin was retained in the trap by stainless steel
frits at the end of the tubing. Connections to the chromatograph were
made with 0.16 cm tubing.
The gas chromatograph employed in this study was a Varian Model 1200,
a single column instrument employing either a flame ionization detector
or a photoionization detector.
The column head pressure on the Varian 1200 was read with a U-tube,
mercury filled manometer; the pressure reading was taken by puncturing
the injection septum with a Hamilton needle, No. 23 gauge conical point
with side hole, connected via tygon tubing to the manometer. Flow
control was provided by a Brooks Model 8743 flow controller. The reten-
tion volume data were collected at maximum electrometer sensitivity and
recorded on a Linear Instruments Model 355 potentiometric recorder or a
Hewlett Packard Model 7133A recorder.
The column temperatures were measured with the aid of a Rubicon
potentiometer. Iron-constantan thermocouples (No. 20) were placed in
contact with the sorbent cartridge and connected to the potentiometer.
To offset the effect of a "line" room temperature EMF generating junction,
a second thermocouple was connected in series with the oven thermocouple
and was immersed in an ice bath. The injector and detector temperature
were kept at 250°C. Total gas flow rates were measured using a soap
bubble flow meter.
In order to study the effects of the major combustion product, water,
on Vg, the apparatus was modified as shown schematically in Figure 3.
Considerable effort was involved in devising a system that could generate
high humidity atmospheres reproducibly for these studies. The modifica-
tions are, therefore, described here in some detail.
A photoionization detector was employed during the water and carbon
dioxide effect study. The purpose for the change in detectors was that
10
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CM Chrwwtogriph
Figure 3. Moisture Generation System
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the water vapor caused a noisy flame ionization detector signal in the
initial moisture experiments. In order to obtain elution peaks that
were discernible from the noise level and still in Henry's Law region,
the photoionization detector, which is insensitive to water, was used.
The modifications to the carrier gas system for the study of moisture
effects were as follows. The carrier gas line to the Varian 1200 was cut
and connected with 0.16 cm (1/16 in) stainless steel swagelok unions at
the appropriate inlet and outlet ports. Copper tubing, 0.64 cm (I/A in.
O.D.) was used throughout the humid atmosphere generation system. The
tubing went from the inlet of the system to a 0.64 cm (1/4 in) swagelok tee.
At this point the liquid water was metered into the system. The method
of introducing the water was found to be critically important in achiev-
ing reproducible levels. The water was added at 7 mg/min into a 100 mL/min
helium carrier gas stream. A 5 cc syringe (Glenco No. 19925-S Gas-Liquid
syringe) and a Harvard Apparatus Model 944 infusion-withdrawal pump was
used to meter in the water.
The syringe was connected with a plastic union to the tubing. A 6
cm length of 0.16 cm (1/16 in) I.D. plastic tubing was connected with a
0.16 cm (1/16 in) I.D. stainless steel swagelok union to a 70 cm length
of 0.16 cm (1/16 in) I.D. high volume stainless steel tubing. The tubing
was then placed into the 0.64 cm (1/4 in) tee with the appropriate
adapters. The tubing was placed inside the tee to allow the helium to
blow by the existing liquid. A fine mesh stainless steel screen was
placed at the outlet of the tee to ensure evaporation of all the droplets.
From the tee the water/helium mixture went through 6 meters (19 ft) of
0.64 cm (1/4 in) coiled copper tubing enclosed in a tube furnace. From
the furnace the carrier gas went into a 400 mL chamber to assure proper
mixing. From the chamber, .64 cm (1/4 in) copper tubing was used to the
outlet of the system where a 0.16 cm (1/16 in) to 0.64 cm (1/4 in) swagelok
reducing union was used to connect the tubing to the carrier gas lines
and then to the injection port.
12
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Heating tapes were used on all exposed tubing from the system inlet
to the injector port of the gas chromatograph. The gas temperature in
the humid atmosphere generation system was maintained above 100°C to
avoid condensation of the water, and was monitored by thermocouple A and
the thermocouple B. The tube furnace maintained the copper coil at 230°C
to ensure all the water was vaporized.
The exact concentration of the water in the carrier stream was
measured by determining the flow of the dry carrier gas and then deter-
mining the weight of the water per minute. This was done by collecting
the water on two cartridges in series filled with Drierite for a known
time and determining the water by weight difference. These values were
then corrected for the chromatographic conditions used.
C. Introduction of Sorbate Samples
The sample introduction technique used in the elution analysis
studies consisted of taking up a small amount (<0.5 uL) of liquid sorbate
in a 10 uL syringe, then expelling the liquid and pumping the syringe
50 or more times. This allowed generation of a reproducible dilute sor-
bate vapor concentration. With the resulting low concentration samples
(<10 ppm) the experiments could be conducted in the Henry's Law region.
Three to five replicate elution experiments were run for each set
of chromatographic conditions.
D. Materials and Reagents
The helium used in the "other sorbents" study and in the moist
atmosphere effects study was prepared by Linde, a Division of Union
Carbide, and obtained through Welders Supply of Billerica, Mass.
The carbon dioxide in helium used in the carbon dioxide effects
studies was 10.5% carbon dioxide in helium, certified standard, obtained
from Matheson Gas Products.
13
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The sorbates used and suppliers are given in Table 1.
TABLE 1
SORBATES AND SUPPLIERS USED IN THE STUDY
Sorbate Supplier
Pentane Burdick and Jackson
Hexane Burdick and Jackson
Decane Poly Science Corporation
Ethyl Bromide Fisher
2-Butanone Poly Science Corporation
Ethylbenzene Poly Science Corporation
Ethanol Gold Shield
n-Butanol Poly Science Corporation
The sorbents and suppliers are given in Table 2.
TABLE 2
SORBENTS AND SUPPLIERS USED IN THE STUDY
*
Sorbent Supplier
Tenax-GC Applied Science Laboratories
XAD-2 Rohm and Haas
XAD-8 Rohm and Haas
Ambersorb 340 Rohm and Haas
Ambersorb 347 Rohm and Haas
Silica Gel Davison
Charcoal Lot 104 SKC, Inc.
Charcoal Lot 106 SKC, Inc.
The Tenax-GC and charcoals were used as received. The silica gel
was held at 110° for 24 hours to activate it, then stored in a desiccator,
The resins obtained from Rohm and Haas were cleaned by several rinses
with water then extraction with methanol for 24 hours then methylene
chloride extraction for the same period. They were then dried under a
nitrogen stream.
*A third Rohm and Haas carbonaceous resin, Ambersorb 348, was not avail-
able in time to be included in this study.
14
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E. Matrix of Experiments
Table 3 lists experiments carried out to evaluate the effect of
combustion gases and Table 4 lists experiments to study other sorbents
for collection of volatile and polar species.
Sorbates were selected to represent the classes of compounds which
had major differences in elution behavior. The sorbate compound classes
chosen were the aliphatic hydrocarbons and the alcohols. The Kiselev
classification for the aliphatic hydrocarbons is Group A (non-polar)
and for the alcohols is Group D (highly polar). Specific compounds were
chosen to have a short retention time (3 to 10 min) at a given tempera-
ture.
In the combustion gas study, experiments that were to be run at
higher temperatures (150°) employed sorbates having higher boiling points
(greater retention volumes) than those employed in the experiments run
at low temperatures (50°C). This was done to provide conveniently
measurable retention times run at both low and high relative humidity
under constant conditions of 10% moisture in the carrier gas stream.
15
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TABLE 3
EXPERIMENTAL MATRIX - COMBUSTION GAS STUDIES
Analyte
n-Butanol
Ethyl benzene
Decane
Pentane
2-Butanone
Ethanol
Ethly Bromide
Dry
X
X
X
T
T
T
T
Moisture
Low R.H.
(High Temp.)
X
X
X
N.T.
N.T.
N.T.
N.T.
(10%)
High R.H.
(Low Temp.)
N.T.
N.T.
N.T.
X,T
X,T
X,T
X,T
10% Moisture & C02
N.T.
N.T.
N.T.
X,T
N.T.
X,T
N.T.
X indicates experiments conducted using XAD-2 resin .
T indicates experiments using Tenax-GC resin.
N.T. indicates experiment not performed.
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TABLE 4
EXPERIMENTAL MATRIX - OTHER SORBENT STUDIES
Pentane
Hexane
Ethanol
Butanone
Charcoal - Lot 104
Charcoal - Lot 106
Silica Gel
Ambersorb - 340
Ambersorb - 347
XAD-8
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
N.T.
/ * Indicates sorbent and sorbate combination tested.
N.T. = indicates combination not tested.
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V. RESULTS
A. Effects of Major Combustion Gases
The purpose of these experiments was to determine the effects that
typical concentration levels of major flue gas components (water and
carbon dioxide) would have on the volumetric breakthrough capacity. The
experiments were conducted by adding 10% by volume of carbon dioxide and/
or 10% by volume of moisture to the carrier gas in the elution chroma-
tography experiments.
1. Effects of Moisture
In the study of the effects of moisture on retention volume, the
carrier gas was maintained at 10% (vol/vol) moisture. Variation of the
column oven temperature, keeping the moisture constant at 10% (vol/vol),
changed the percent relative humidity (% R.H.). To assist in interpreta-
tion of these results, the relationship between % R.H., and column oven
temperature at the constant moisture level, is given below in Table 5.
TABLE 5
% RELATIVE HUMIDITY COMPARED TO COLUMN TEMPERATURE
AT CONSTANT 10% MOISTURE (vol/vol)
Column Temperature (°C) % Relative Humidity
140 3.02
120 5.51
100 10.79
80 23.09
50 88.64
20 Saturated
a. Effects of 10% (vol/vol) Moisture - Low % R.H.
The experiments at 10% (vol/vol) moisture—low % R.H. were run only
on XAD-2.
The three sorbates used and their Kiselev classification are:
18
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Decane—Group A, Ethyl benzene—Group B, and n-Butanol—Group D. The
sorbates were run at both wet and dry conditions for the comparison of
the V 's. The chromatographic conditions and retention volumes determined
O
are given in Table 6.
TABLE 6
COMPARISON OF Vg FOR DRY AND LOW % RELATIVE HUMIDITY
ATMOSPHERES IN XAD-2
Sorbate
n-Butanol
Ethyl
benzene
Decane
Column
Temperature °C
154.2
154.0
138.3
138.1
154.2
154.0
138.3
138.1
154.2
154.0
138.3
138.1
% Moisture
(vol/vol)
10.6
0
10.6
0
10.6
0
10.6
0
10.6
0
10.6
0
% Relative
Humidity
2.3
0
3.5
0
2.3
0
3.5
0
2.3
0
3.5
0
Vg (mL/g)
56.0
56.6
93.4
97.6
306
308
618
638
1320
1370
3410
3430
The retention volumes are essentially the same for the dry and
humid atmosphere for each of the sorbents tested.
b. Effects of 10% (vol/vol) Moisture - High % R.H.
In the 10% (vol/vol) moisture—high % R.H., experiments, two
sorbents, XAD-2 and Tenax-GC, and four sorbates, Pentane, 2-Butanone,
Ethyl bromide and Ethanol, were used.
The sorbates1 Kiselev classifications are: Pentane—Group A,
19
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2-Butanone and Ethyl bromide—Group B, and Ethanol—Group D. The Group
A and D compound classifications bracket all the other compound groups
except acids; therefore, any significant effect of moisture on retention
volume of any compounds except acids would be observed. The ketones
and halogenated hydrocarbons, both Group B compounds, were of particular
interest because there had been differences of 3-5 kcal/mole between
their differential heats of absorption, AH^, on Tenax-GC and XAD-2.
The data obtained with XAD-2 are summarized in Table 7.
TABLE 7
COMPARISON OF Vg's FOR SORBATES AT TWO
DIFFERENT RELATIVE HUMIDITIES ON XAP-2
" "-^fiondition
Sorbate ~*--^^^^
Pentane
2-Butanone
Ethanol
Ethyl bromide
Column
Temperature
(CC)
53.1
53.2
53.1
53.5
53.1
54.0
55.0
54.1
Z
Moisture
(vol/vol)
0
10.9
0
9.8
0
10.8
0
11.0
I Relative
Humidity
0
87
0
76
0
82
0
83
Vg(mL/g)
1080
1090
3430
2840
280
244
640
615
Relative V-
wet /dry
1.00
0.83
0.87
0.96
Comparing the relative V value, there is little effect from the
5
humid atmosphere for pentane and ethyl bromide. There is, however, a
13% decrease in V for ethanol and a 17% decrease for 2-Butanone at the
O
higher relative humidity. The results for the 2-Butanone were confirmed
in a replicate experiment.
The data obtained for Tenax-GC are given in Table 8. A comparison
of the wet and dry atmosphere retention volumes show decreases of 22%
for ethyl bromide and ethanol, 31% for 2-Butanone and 43% for pentane.
The effects of humidity on Tenax-GC retention volume are much higher than
20
-------
TABLE 8
COMPARISON OF V 's FOR SORBATES AT TWO DIFFERENT RELATIVE HUMIDITIES
8
ON TENAX-GC
\Condition
^\^^
Sorbate ^v^^s^
Fentane
Ethyl bromide
2-Butanone
Ethanol
Column
Tempera-
ture (°C)
55.5
54.4
54.8
54.4
55.5
54.4
54.8
54.4
55.2
54.4
54.8
54.4
55.5
54.4
54.8
54.4
%
Relative
Humidity
0
0
83
78
0
0
83
78
0
0
83
78
0
0
83
78
%
H20
0
V
(mL?g)
536.9
0
11
10
0
0
11
10
0
0
11
10
0
0
11
10
532.4
313.7
295.5
Relative V
wet K
dry
0.57
704.0 i
688.8
582.0
510.5
3234.9
3134.2
2420.5
1976.9
233.1
268.3
205.6
186.3
0.78
0.69
0.78
Relative V
rg» wet, determined by taking the average wet V over the average dry V for a given sorbent.
dry
-------
were found on XAD-2. The difference in moisture sensitivity between the
two resins can be understood in view of the more polar nature of Tenax-
GC.
2. Effects of Carbon Dioxide
Pentane—Group A and Ethanol—Group D were the sorbates used in
determining the effects of carbon dioxide on retention volume. The
carbon dioxide experiments were carried out in the presence of 10% (vol/vol)
moisture and the results of the combined carbon dioxide/water experiments
were compared to the 10% (vol/vol) moisture results. The data are given
in Table 9 for both XAD-2 and Tenax-GC.
Comparing the relative V with and without carbon dioxide on the
O
XAD-2 shows no sigifnicant change in the retention volume.
In conclusion for XAD-2, introduction of water vapor led to V re-
g
ductions of 0-4% for the nonpolar sorbates and 13-17% for the two polar
sorbates. Carbon dioxide at 10% (vol/vol) levels resulted in essentially
no further decrease on this sorbent. On the Tenax-GC, a 43% reduction
in the retention volume was observed for the addition of moisture and an
additional decrease of retention volume of 25% was observed in the com-
bined atmosphere of moisture and carbon dioxide.
B. Comparison of Various Sorbents
The purpose of these experiments was to characterize several
sorbents, other than XAD-2 and Tenax-GC, that have been used or have
potential for use in sampling applications. One objective was to
identify sorbents that would be more effective than XAD-2 or Tenax-GC
for collection of very volatile (b.p. <100°C) organic species.
A petroleum base charcoal, a coconut shell base charcoal, silica
gel, Ambersorb XE-340, Ambersorb XE-347, and XAD-8 were other solid
sorbents Investigated. Specific surface area analysis to characterize
these sorbents was performed by Micromeritics on the XAD-8, XE-340,
22
-------
TABLE 9
COMPARISOH DATA FOR Vg IN HUMID ATMOSPHERES WITH AND WITHOUT
CARBON DIOXIDE
XAD-2
to
Tenax-GC
^v^Jondltior
Sorbate ^\
Pentane
Ethanol
Column
Temp CC)
53.0
52.5
53.1
52.6
53.0
52.6
53.1
52.6
Atmosphere
C02 + H20
C02 + H20
H20
H20
C02 + 1^0
C02 + H20
H20
H20
Z Relative
Humidity
88.9
91.6
90.3
90.4
88.9
91.6
90.3
90.4
V
(mL/g)
1100.7
1043.8
1032.5
1281.5
240.7
229.6
210.5
250.0
Relative V *
(with C02/ g
without C02)
0.927
1.021
Pentane
Ethanol
52.1
52.6
52.8
52.8
52.1
56.6
52.8
52.8
C02 + H20
C02 + H20
H20
H20
CO2 + H2°
C02 + H20
H20
H20
93.4
90.3
82.2
88.4
93.4
90.3
82.2
88.4
345.1
304.1
464.9
398.2
167.2
185.3
204.6
197.3
0.752
0.877
Relatlve V
g ^Ithout^CO
detenllined
taking average C02 4- H20 Vg over H20 Vg for a given oorbent.
-------
XE-347, charcoal Lot 104, and charcoal Lot 106. The data are given in
Appendix A. The sorbates used and their Kiselev classification are
Pentane and Hexane—Group A, and Ethanol and n-Butanol—Group D. In
the previous work, a correlation between Log Vff20 and boiling point of
O
the compounds in chemical classes was determined. In this screening
of other sorbents, there were not enough data points per sorbent and
sorbate class to quantitatively compare the correlation between Ve and
O
a physical property of the sorbate.
Results of the individual experiments are presented in the next
four parts. A comparison of all of the sorbents is given in part 5.
1. Charcoals
The charcoals used were SKC, Inc., Lot 104, a petroleum-based
charcoal, and Lot 106, a coconut shell based charcoal. These charcoals,
Type I according to the Kiselev scheme for sorbents, are a non-
2
specific type of sorbent with surface areas of 1270 m /g, Lot 104, and
2
1270 m /g, Lot 106. The experimental data is summarized in Table 10.
In Table 11 the sorbate retention volumes, V , are compared at a
O
common temperature. The retention volumes on the Lot 106, coconut shell
base charcoal, are almost a factor of 2 greater than the V 's on the
O
Lot 104, petroleum base charcoal.
2. Silica Gel
The silica gel used was Davison Grade 5. This sorbent is classi-
fied by Kiselev as Type II, Specific, with localized positive charge.
The silica gel can be described as a highly polar sorbent.
The experimental results using silica gel are reported in Table 12.
Results could not be obtained for alcohols because they exhibited ex-
cessive peak broadening, and it is therefore recommended that silica
gel not be used for sampling of alcohols.
24
-------
TABLE 10
RETENTION VOLUMES, VE> ON CHARCOALS LOTS 104 AND 106
FOR THE TESTED SORBATES
»-
Sorbent
Charcoal
Lot No.
104
Charcoal
Lot No.
106
Compound
Pentane
Hexane
Ethanol
n-Butanol
Pentane
Hexane
Ethanol
n-Butanol
Column
Temp. °C
263.0
278.6
262.8
278.6
240.2
257.6
252.0
263.0
263.3
278.1
279.2
269.2
278.1
262,8
271.3
263.3
279.2
Vg(mL/g)
699
467
3,350
2,060
137
88.9
205
153
1,150
782
769
4,490
3,520
307
278
238
177
Standard
Deviation
7.7
4.6
29.1
18.7
3.0
3.2
8.2
7.5
9.7
7.0
8.3
75.4
17.4
7.9
3,4
4.2
4.0
25
-------
TABLE 11
COMPARISON OF RETENTION VOLUME. Vg, OF THE CHARCOALS LOTS
104 AND 106 AT COMMON TEMPERATURES
Compound
Pentane
Hexane
n-Butanol
Ethanol
Interpolation
Temp. °C
270°
270°
260°
260°
Lot 104
Vg(mL/g)
581
2,680
165
87.7
Lot 106
V (mL/g)
~ g "'-
964
4,390
254
318
TABLE 12
RETENTION VOLUMES, Vg> ON SILICA GEL FOR THE TESTED SORBATES
Sorbent
Silica Gel
Compound
Pentane
Hexane
Column
Temp . °C
73.4
81.8
94.5
108.9
Vg(mL/g)
87.4
46.7
92.3
54.9
Standard
Deviation
5.7
5.7
11
5.5
26
-------
3. Ambersorb XE-340 and XE-347
The Ambersorb XE-340 is a non-polar sorbent with a surface area of
480 m2/g. The Ambersorb XE-347 is a polar sorbent with a surface area
of 457 n»2/g- Tne experimental results are reported in Table 13.
One sorbate, pentane, was tested on the Ambersorb XE-347. Comparing
the retention volume data from Table 14 of the pentane on the XE-347 with
corresponding data for the charcoals and XE-340, indicated that the
XE-347 was similar to the XE-340 and charcoals. Further studies to
explore possible subtle differences among these high Vg sorbents due to,
for example, polarity differences, were beyond the scope of this work.
4. XAD-8
Amberlite XAD-8, an acrylic ester, is a polymeric resin with a
surface area of 120 m2/g. The data for the XAD-8 experiments are given
in Table 15. From the data in Table 14, the XAD-8 behaves much like
XAD-2 and Tenax-GC for non-polar compounds, but has a slightly larger
affinity (factor of ten) for alcohols.
5. Comparison of V and K. Values Among Sorbents
• i. • _ g f^
In Table 14, calculated retention volume values have been presented
for the sorbates on the six sorbents at 20°C. Because of the large
extrapolation (270°C to 20°C) required for some of the sorbents, the
data should be compared primarily with a view to order of magnitude
differences and effects. The extrapolated values are compared to the
previously reported retention volumes of the sorbates on Tenax-GC and
XAD-2.
Comparing the retention volumes of the charcoals to those of
45
Tenax-GC and XAD-2, the charcoal retention volumes are 10 to 10 times
larger for alcohols. From the data, the two charcoals behave very
similarly in their activity. Ambersorb XE-340 and XE-347 are roughly
comparable to the charcoals tested. Silica gel behaves very similarly
to the polymeric resins, XAD-2 and Tenax-GC for the aliphatic hydrocarbons,
27
-------
TABLE 13
RETENTION VOLUMES. V . ON THE AMBERSORBS XE-340 AND
XE-347 FOR THE TESTED SORBATES
Sorbent
Ambersorb
XE-340
Ambersorb
XE-347
Compound
Pentane
Hexane
Ethanol
Fentane
Column
Temp . °C
178.8
187.9
178.8
196.8
196.8
207.0
245.3
254.3
V6(mL/g)
490
274
1710
716
193
152
1680
1270
Standard
Deviation
7.3
6.7
154
108
6.9
59
80
25
28
-------
TABLE 14
Comparison of Sorbents via the Retention Voluaea
of the Selected Sorbates at 20*C
ro
s^4orbent
•prbateV^
Pentane
Hexane
Ethanol
n-Butanol
Charcoal
Lot 104
1 x 108
4 x 10*
3 x 106
2 x 107
Charcoal
Lot 106
1 x 108
2 x 109
6 x 10"
1 x 106
Silica
Gel
1 x 10*
3 x 103
Aaberaorb
ZE-340
4 x 109
4 x 108
2 x 10s
Aaberaorb
XE-347
2 x 108
XAD-8
3 x 10"
3 x 10"
2 x 101*
2 x 10s
XAD-2
2 x 10"**
8 x 10"**
2 x 103*
2 x 10"*
Tenax-GC
2 x 103**
1 x 10"**
9 x 10Z*
4 x 10"*
* from EPA Report EPA-600/7-78-054, pages 22-23.
Values determined fro* linear regression equations reported in
EPA-600/7-78-054, pages 52-53.
-------
TABLE 15
RETENTION VOLUMES ON XAD-8 OF THE TESTED SORBATES
So r bent
XAD-8
!
Compound
Pent an e
Hexane
Ethanol
n-Butanol
Column
Temp. °C
96.9
87.9
103.4
114. A
114.4
126
138.5
147.3
VK(mL/g)
103
174
268
164
108
66.2
245
173
Standard
Deviation
2.1
3.4
3.4
0
1.3
3.3
2.5
4.0
30
-------
Comparing the retention volumes of the charcoals to those of
4 5
Tenax-GC and XAD-2, the charcoal retention volumes are 10 to 10 times
larger for alcohols. From the data, the two charcoals behave very
similarly in their activity. Ambersorb XE-340 and XE-347 are roughly
comparable to the charcoals tested. Silica gel behaves very similarly
to the polymeric resins, XAD-2 and Tenax-GC for the aliphatic hydrocarbons.
The retention volumes for alcohols on XAD-8 is a power of ten larger than
XAD-2 and 100 times larger for Tenax-GC.
In order of decreasing volumetric capacity, the sorbents screened
are: Charcoal Lot 104 > Charcoal Lot 106 > Ambersorb XE-340 > Ambersorb
XE-347 > XAD-8 > XAD-2 > Tenax-GC.
The equilibrium adsorption coefficient, KA, can be calculated from
the retention volume data in Table 14 and the specific surface Area, A°,
for each of the sorbents used. In Table 16, the specific surface area
for the sorbents are given. K. is a measure of the intrinsic thermody-
namic affinity of sorbent for sorbate, independent of effects of increased
surface area. The equation is:
V
KA = A°RT
s
where: V * retention volume at 20°C in mL/g
8 2
A° • specific surface area in m /gram
/
R - 6.232 x 10 mL-mm/mole - °K
T - temperature of V (293.16°K) of V value
o o
The absorption coefficients have been calculated with the retention
volume data from Table 14 and listed in Table 17. It is interesting
to note that the charcoals, Lots 104 and 106, and Ambersorbs XE-340
and 347, both non-specific/non-polar, have greater K.'s (by three to
A
five orders of magnitude) than the polymeric resins, XAD-2, XAD-8, and
Tenax-GC when comparing pentane and hexane as the sorbates. When using
31
-------
TABLE 16
SPECIFIC SURFACE AREAS, A!, FOR SORBENTS
Sorbent
XAD-2
Tenax-GC
XAD-8
Ambersorb XE-340
Ambersorb XE-347
Charcoal Lot 104
Charcoal Lot 106
BET Surface Area
(m2/g)
364
23.5
120
480
457
1270
1270
32
-------
TABLE 17
Adsorption Coefficients . KA. on Resins at 20"C
^v^gorbent
Jorbate""--^
Pentane
Hexane
Ethanol
n-Butanol
Charcoal
Lot 104
4 x 10~3
2 x 10~]
1 x 10~"
9 x 10~"
Charcoal
Lot 106
4 x 10"3
9 x 10~2
3 x 10~6
4 x 10~5
Ambersorb
XE-340
5 x 10"1
5 x 10~2
2 x 10~5
Ambersorb
XE-347
2 x 10~2
XAD-8
1 x 10~5
1 x 10~5
9 x 10~6
9 x 10~5
XAD-2
3 x 10~6
1 x 10~5
__**
3 x 10 7
_,**
3 x 10 6
Tenax-GC
5 x 10~6
2 x 10~5
2 x 10-6**
1 xlO-***
**
In units of moles/mm-m2
From EPA Report EPA-600/7-78-054, page 71
-------
the alcohols ethanol and n-Butanol for comparison, the absorption coef-
ficients are also greater for the carbonaceous sorbents than for the
other resins. However, the K's for the alcohols vary over a smaller
range (one to three orders of magnitude) than those for the alkanes.
Sorbent attraction, in order of decreasing intrinsic affinity (K )
A
for sorbates tested, are: Charcoal Lot 104 > Ambersorb XE-340 > Charcoal
Lot 106 > Ambersorb XE-347 > XAD-8 > Tenax-GC > XAD-2.
34
-------
VI. CONCLUSIONS AND RECOMMENDATIONS
In this work, elution chromatography was successfully used to study
the effects of combustion gases, carbon dioxide, water and the combined
effect of carbon dioxide and water, on the retention volume of trace
level sorbates on XAD-2 and Tenax-GC. The retention behavior of XAD-2
is relatively unaffected by the combustion gases studied. Introduction
of water vapor led to Vg reductions of 0-4% for the non-polar sorbates
studied and 13-17% for the two polar sorbates. Carbon dioxide at 10%
(vol/vol) levels resulted in essentially no further decrease for XAD-2.
On the other hand, the Vg values on Tenax-GC were reduced by 22-43% in
the presence of water vapor, and an additional 25% decrease was observed
when carbon dioxide was introduced.
Other sorbents have been Investigated for collecting of volatile
and polar organics. The charcoals, Lot 104 and Lot 106, and the Ambersorbs,
XE-340 and XE-347, appear to be potential candidates for this purpose.
The charcoals and Ambersorbs show Vg values three to five orders of
magnitude higher than XAD-2 for non-polar sorbates. For alcohols, the
differences are one to three orders of magnitude. The increased Vg's are
only partially attributable to differences in surface area. Based on
this study, the order of preference in selection of sorbents for collec-
tion of high volatile and polar organics, listed in order of decreasing
intrinsic affinity (KA), are: Charcoal Lot 104 > Ambersorb XE-340 >
Charcoal Lot 106 > Ambersorb XE-347 > XAD-8 > Tenax-GC > XAD-2.
Further studies with sorbents should include:
1. The recovery of various chemical classes from different
sorbents: XAD-2, Ambersorb XE series and charcoals.
2. Determining retention volumes for organometallic species
on XAD-2 and Tenax-GC.
3. Further investigation of a sorbent to collect volatile
organics.
35
-------
VII. REFERENCES
1. Adams, J.W., K.T. Menzies, and P.L. Levins, "Selection and Evaluation
of Sorbent Resins for Collection of Organic Compounds," EPA Report
600/7-77-044, April, 1977, PB 268-559.
2. Gallant, R.J., J. King, P. Levins, J. Piecewicz, "Characterization
of Sorbent Resins for Use in Environmental Sampling," EPA Report
600/7-78-054, March, 1978, PB 284-347.
3. Hamersma, J.W., S.L. Reynolds, and R.F. Maddalone, "IERL-RTP
Procedures Manual; Level 1 Environmental Assessment," EPA Report
600/2-76-160a, June, 1976, PB 257-850.
4. Locke, D.C., Physiochemical Measurements Using Chromatography in
"Advances in Chromatography," Vol. 14, J.C. Gidding, E. Grushka,
J. Cazes, and P.R. Brown, eds., Marcel Dekker, Inc., 1976, pp.
87-198.
5. Kobayaski, R., H.A. Deans and P.S. Chappelear, Physio-Chemical
Measurements by Gas Chromatography. in "Applied Thermodynamics,"
American Chemical Society, Washington, D.C., 1968, pp. 227-246.
6. Kiselev, A.V. and Y.I. Yashin, "Gas-Adsorption Chromatography,"
Plenum Press, N.Y., 1969, pp. 11-14.
36
-------
APPENDIX A
Incremental Surface Area Distribution
37
-------
I OF MAXIMUM SUhhACL Anu*( +14-730 S(J M/G)
VEhSUS AVLhACL PUf'.L L»I A14LTU-.* AMGSTJUMS
+ 27
+ 32
+ 37
+ 42
+ 47
+ 52
+ 57
+ 62
+ 67
+ 72
+ 77
+ 82
+ 87
+ 92
+ 97
+ 105
+ 115
+ 125
+ 135
+ 145
+ 155
+ 170,
+ 190
+ 2IB
+ 230,
+ 270.
+ 290.
+ 325.
+ 375.
+ 425.
+475.
+ 550.
201 4C9& 602. 80i
"1 1 J J
***************************************i
*************************************
*»»*«»*»*****»***»**#»***********•
******************************
*************************
******************
************
**************
**************
***********
***********
*********
*******
***********
*****
**************
******************
*************
**********
*************
***** ***
*******************
****************
******************
**************
***************
**************
***>****»*****************
***********************************»«(
*****«************************»****,,,,
****************************
********************************
Figure A-l. Incremental Surface Area Distribution (Desorption) XE-340
38
-------
X OF MAXIMUM SURFACE AREA( +37.022 SC M/C>
VERSUS AVERAGE PORE DIAMETER.. ANGSTROMS
20S 40i 60S. 80% lees
I ............ i ..... ....... i ............ i ........ . • "i ...... ...... x
+ 22. 5 *****************************************************************
+ 27.5
+32*5 ************
+37.5 *********
+42.5 *******
+47.5 »*
+52.5 *
+57.5 *
+62.5 *
+ 67.5
+72.5 *
+77.5 *
+82.5 *
+87.5 *
+92.5 *
+ 97.5
+105.0 *
+115«0 ***
+125-0 **
+135.0 **
+145.0 **»*
+155.0 **
+170.0 *******
+190.0 ********
+210. C ********
+ 2317-0 *************
+250-0 **********
+27C«2 *********
4-290.0 ***********
+325-2 ****************
+375.0 *******
+425.0 *
+475.0
+553. Z
Figure A-2. Incremental Surface Area Distribution (Desorption) XE-347
39
-------
M1CROMERITICS INSTRUMENT CORPORATION
DIGISORB 2500
PACE 18
SAMPLE:ARTHUR D. LITTLE XE-347 STAi 3 ECTIMEt 3 MODEi 5 METHODi 3
INCREMENTAL SURFACE AREA DISTRIBUTION (DESORPTION)
X OF MAXIMUM SURFACE AREA( +14.097 SO M/G>
VERSUS AVERAGE PORE DIAMETER* ANGSTROMS
401
+ 22-5
+ 27.5
+ 32.5
+ 37.5
+ 42.5
+ 47.5
+ 52.5
+ 57.5
+ 62.5
+ 67.5
+ 72.5
+ 77.5
+ 82.5
+ 87.5
+92.5
+ 97.5
+105.0
+ 1 15.0
+125.0
+135.E
+145.0
+155.0
+170.0
+190.0
+210.0
+230.0
+250.0
+270.0
+ 290.e
+325.0
+375.0
+425.0
+475.0
+550.0
20*
I I "
******!
*******************************
**********
60;
80
lee*
i
>*»******
********
**
**
*
**
**
***
***
********
******
*****
***********
*******
************************
****************************
***************************
**************************************
*****************************
******************
***********
***************
**
Figure A-3. Incremental Surface Area Distribution (Desorption) XAD-8
40
-------
X Or MAXIMUM SURFACE AREA< +59*262 SO M/6>
VERSUS AVERAGE PORE DIAMETER* ANGSTROMS
20X 40X 60Z 80S 100S
x......,.,.,, !..,..,,,..., j..... ..... . .j.,.. ...... , .J............J
+22*5 *****************************************************************
+ 27. 5 ****************************
+ 32.5 *************
+37-5 ************************
+42.5 **************************
+47.5 ***
+52.5 *
+57.5 *
+62.5 *
+67.5 *
+ 72.5
+ 77.5
+82.5
+87.5
+92.5
+97.5
+105.0
+115.0
+125.0
+135.0
+145.0
+155*0
•170.0
+210V0
+230.0
4-250.0
4-270.0
+290.0
t-325.0
+
3
7
5.0
+425.0
+475.0
+550.0
Figure A-4. Incremental Surface Area Distribution (Desorption)
Charcoal Lot 104
41
-------
X OF MAXIMUM SURFACE AREA< * 144.074 SC M/G)
VERSUS AVERAGE PORE DIAMETER* ANGSTROMS
20Z
I
40X
I"
60Z
"I"
80S
"I"
I0ez
•••i
• 22
• 27
•32.
+37
•47
•52.
•57.
• 62.
+ 67.
• 77.5
• 82.5
+ 87.5
• 92.5
• 97.5
•105.0
•115*0
•125.0
•135.0
•145.0
•155.0
•170.0
•190.0
•210.0
•230*0
+250.0
+270.0
•290.0
•325.0
•375.0
•425.0
•475.0
•550.0
****************************
*************
***********
***
**
Figure A-5. Incremental Surface Area Distribution (Desorption)
Charcoal Lot 106
42
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-216
I. RECIPIENT'S ACCESSION- NO.
4. TITLE AND SUBTITLE
Further Characterization of Sorbents for Environmental
Sampling
5. REPORT DATE
September 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J.F. Piecewicz, J.C. Harris, and P.L. Levins
8. PERFORMING ORGANIZATION REPORT NO.
3. PERFORMING ORGANIZATION NAME AND ADDRESS
Arthur D. Little, Inc.
Acorn Park
Cambridge, MA 02140
10. PROGRAM ELEMENT NO.
EHB 537
11. CONTRACT/GRANT NO.
68-02-2150, T.D. 10601
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 3/78 - 6/79
14. SPONSORING AGENCY CODE
EPA/600/13
16. SUPPLEMENTARY NOTES
541-2557.
IERL-RTP project officer is Larry D. Johnson, Mail Drop 62, 919/
16. ABSTRACT " ' "
The report gives results of an ongoing experimental program to evaluate the
breakthrough characteristics of sorbent resins for sampling of organic vapors using
an elution analysis chromatographic technique. The effects of water vapor and C02,
at levels typical of gaseous effluents from combustion processes, on retention of
nonpolar and polar species on two commonly used sorbents (XAD-2 and Tenax-GC) have
been studied. Effects on XAD-2 were small but the volumetric capacity of Tenax-GC
was substantially decreased. Other sorbents were characterized for potential use
in vapor sampling systems: coconut-based charcoal, petroleum-based charcoal, silica
gel, Ambersorb XE-340 and XE-347, and XAD-8. Retention volumes for XAD-8 and silica
gel were roughly comparable to those of XAD-2 and Tenax-GC; those of the charcoals and
the Ambersorbs were 2 to 4 orders of magnitude higher. Recovery of sorbate from
charcoals is known to be poor in some cases, however, and recovery from the Ambersorbs
is suspect but under investigation.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Pollution
Sampling
Sorbents
Polymers
Organic Compounds
Carbon Dioxide
Charcoal
Analyzing
Vapors
Chromatography
Water Vapor
Silica Gel
Pollution Control
Stationary Sources
Resins
XAD-2
XAD-8
Tenax-GC
Ambersorbs
13B
14B
11G
07D
07C
07B
2 ID
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
47
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (»-73)
43
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