United States
Environmental Protection
Agency
Environmental Sciences Research
Laboratory
Research Triangle Park NC 27711
EPA-600/2-79-205
December 1979
Research and Development
Solid Sorbent for
Collecting
Atmospheric Sulfur
Dioxide

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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  ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate  instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                               EPA-600/2-79-205
                                               December 1979
SOLID SORBENT FOR COLLECTING ATMOSPHERIC SULFUR  DIOXIDE
                          by
                    R. J. Cotter
                    S. G. Smith Jr.
               Union Carbide Corporation
      Chemicals and Plastics Research Laboratories
             Bound Brook, New Jersey  08805
                Contract No. 68-02-1782
                    Project Officer

                      James Mulik

     Atmospheric Chemistry and Physics Division
     Environmental Sciences Research Laboratory
    Research Triangle Park, North Carolina  27711
      ENVIRONMENTAL SCIENCES RESEARCH LABORATORY
          OFFICE OF RESEARCH AND DEVELOPMENT
         U.S. ENVIRONMENTAL PROTECTION AGENCY
    RESEARCH TRIANGLE PARK, NORTH CAROLINA  27711

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                           DISCLAIMER
     This report has  been  reviewed  by the Environmental Science
Research Laboratory,  U.S.  Environmental Protection Agency,  and
approved for  publication.   Approval  does not signify  that  the
contents necessarily  reflect the views  and policies of the U.S.
Environmental Protection Agency, nor does mention of  trade names
or commercial products  constitute endorsement or recommendation
for use.
                               11

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                           ABSTRACT


     This  research  program  was initiated with  the overall
objective of developing a replacement method for the West-Gaeke
method presently used to measure 24-hour ambient sulfur dioxide
concentrations in ambient  air.

     It  was  demonstrated  that  a solid sorbent, consisting  of
Puramer S coated open cell polyurethane foam, can be used to fix
the  quantities of sulfur dioxide that would be collected  if
typical  ambient air was filtered for 24 hours at 200 cc/minute.

     The method of assaying  sulfur dioxide collected by the
adsorbent consisted of  controlled thermal  desorption  of  sulfur
dioxide  followed by continuous analysis using a Dohrmann micro-
coulometric Titration System.   Also,  it was shown that trouble-
some  sulfur dioxide  decay,  occurring during post collection
storage, was primarily the result of oxidation.   This  decay was
minimized,  to an acceptable level, by properly sealing  the spent
Puramer S collector devices to prevent oxygen contamination from
contacting the  adsorbent prior to thermal  desorption and  subse-
quent assaying.

     This report was  submitted  in fulfillment of 68-02-1782  by
Union  Carbide  Corporation  under the  sponsorship  of the U.S.
Environmental  Protection Agency.   This report  covers  a  period
from May 1,  1975  to  November 30,  1977 and  work was  completed
November 30, 1977.
                              111

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                            CONTENTS

Abstract	iii

Figures	   vi

Tables   	vii

     1.  Introduction  	    1
     2.  Conclusions and Recommendations 	    2
     3.  Prior Program Background  	    3
     4.  Puramer S-based Ambient Air Monitoring System ...    5
     5.  Experimental  	    9

           Sulfur Dioxide Adsorption Characteristics of
           Puramer S - Polyurethane  Foam Adsorbents ....    9

           Effect of Desorption Temperature on Sulfur
           Dioxide Recoveries  	   11

           Effect of Puramer S Content on Sulfur Dioxide
           Recovery Efficiency 	   12

           Effect of Collector Cycling on the Sulfur
           Dioxide Recovery Efficiency 	   14

           Effect of Prehydration on the Sulfur Dioxide
           Recovery Efficiency of Puramer S Adsorbents ...   16

           Effect of Storage on Sulfur Dioxide Recovery
           Efficiency	19

     6.  Procedures	25

           Method of Loading Sulfur Dioxide on Puramer
           S Adsorbents	25

           Calibration of Sulfur Dioxide Purmeation Tubes  .   27

           Thermal Desorption Dioxide Method for
           Assaying Sulfur Dioxide Dioxide Adsorbents  ...   29

           Preparation of Puramer S - Polyurethane Foam
           Adsorbent and Subsequent Collector Devices  ...   32

References	34

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                             FIGURES


Number                                                      Page
 1  Puramer S Based Sulfur Dioxide Monitoring
      System-Collector System  	  6

 2  Puramer S Based Sulfur Dioxide Monitoring
      System-Analyzer System	  7

 3  Puramer S Filter Seal	22
                               VI

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                            TABLES
Number                                                      Page
 1  Sulfur Dioxide Analysis by a Puramer S-based
    Analytical Method  	    8

 2  Adsorption Characteristics of Puramer S-polyurethane
    Foam Adsorbents	10

 3  The Effect of Desorption Temperature on Sulfur Dioxide
    Recoveries	11

 4  Effect of Puramer S Content on Sulfur Dioxide Recovery
    Efficiency	13

 5  Puramer S Adsorbent Cycling Versus Sulfur Dioxide
    Recovery Efficiency	15

 6  Effect of Prehydration on the Sulfur Dioxide Recovery
    Efficiency of Puramer S Adsorbents 	   16

 7  Puramer S-based Sulfur Dioxide Analytical System
    Parameters	  .   17

 8  Sulfur Dioxide Assays Via a Puramer S-based Method ...   18

 9  Effect of Post-collection Storage on Puramer S Adsorbent
    Recovery Efficiency  	   20

10  Puramer S—Sulfur Dioxide Storage Stability in an  Inert
    Atmosphere . . »	21

11  Effect of Proper Sealing on the Storage Stability
    of Spent Puramer S Adsorbents  	   23

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                           SECTION 1

                          INTRODUCTION
     One of  the goals  of the  Environmental  Protection Agency
(EPA)  is  to accurately monitor  24-hour  average sulfur dioxide
concentrations  in  ambient  air.   This  monitoring must  be as
simple  as  possible  because it  is  carried  out at unmanned mon-
itoring stations where collector  pickup  is  usually  performed
by  unskilled,  volunteer workers.   The  concentration  range of
interest is 26 to 2600 yg/m3  (n,.01  to  1 ppm) for  sulfur
dioxide.

     At the  present  time,  monitoring  is generally accomplished
using  the  West-Gaeke  method.   This wet  chemical method uses a
toxic  liquid  collector  containing  a mercuric  salt dissolved in
water.  This troublesome  collector solution  is packaged  after
use  and sent  to a central  testing  laboratory for analysis.
During both  the storage  and  analysis of  spent collectors,
spillage can result in  unwanted  contamination of important work
areas.   Also,  storage at ambient temperatures consistently
results in uncontrollable  sulfur dioxide  decay  which  leads to
lower than actual sulfur dioxide levels.  The  handling of liquid
systems by unskilled  workers at  the monitoring sites also leads
to poor assay accuracy.

     The purpose of this investigation, therefore, is to develop
a simple,   quantitative method for  collecting  and assaying atmo-
spheric levels  of  sulfur  dioxide.  The  method  is  to  be  based
on  a proprietary  Union Carbide Corporation polymeric  amine
adsorbent  called Puramer S.

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                           SECTION 2

                  CONCLUSIONS AND RECOMMENDATIONS
     It  has been  demonstrated  that a Puramer S-polyurethane
foam adsorbent  can be used to fix  the  levels  of sulfur dioxide
that would  be collected if typical  ambient  ait is filtered for
24  hours at  200  cc/minute.   The method of- assaying  the sulfur
dioxide  collected  by  the Puramer  S-based  adsorbent,  consists
of  controlled  thermal desorption of sulfur  dioxide  followed
by  continuous sulfur  dioxide  analysis  using  a Dohrmann Micro-
coulometric Titration  System.

     It  has  also  been shown that  sulfur  dioxide decay  can be
expected during  storage  of  spent  collector devices,  but  that
elimination  of oxygen during  this  storage  period reduces the
degree  of decay  to a minimum.   Therefore  a  collector sealing
method,  based on a glass plug,  Teflon sleeve  end cap,  has been
shown  to be  effective in preventing  undesirable sulfur dioxide
decay  during  storage  of spent  Puramer S collectors at 25°-27°C.
Collectors  were  successfully  stored for  up to  14 days,  prior
to  assaying,  without  significant  loss  of sulfur dioxide  (>95%
S02  recovery).    Storage  of  spent  collectors  at  40°C  were not
totally  successful.   After only  3  days  at 40°C, expected assays
were  reduced  by  as much  as  26  percent.   Subsequently, results
obtained on spent  filters again  sealed with  the glass rod-Teflon
sleeve  end  cap and stored in  an oxygen-free environment showed
negligible  sulfur dioxide decay.    These  results  indicate the
need for an even  better collector seal than presently available.

     All of the  data  obtained  to date has been under controlled
laboratory  conditions  and free  of  potential interferences from
gaseous  species  normal to ambient  air.   Therefore,  before this
unique Puramer  S-based sulfur  dioxide monitoring system can be
subjected  to  comparative  field  study with  the  presently  used
West-Gaeke method,  a  study of possible  interferences is recom-
mended.   To  totally complete  the  development  of the Puramer S
monitoring system will require additional funds.

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                           SECTION 3

                    PRIOR PROGRAM BACKGROUND


     As previously mentioned, the  sulfur dioxide  monitoring
system under  development is  to  be based on  Puramer S,  a pro-
prietary Union  Carbide  Corporation polymeric amine  adsorbent.1
Puramer S  is  an efficient,  high-capacity  sulfur dioxide adsorb-
ent which  is  prepared by heating  N-glycidyl piperazine oligomer
until  it  becomes  cross-linked and  hence water  insoluble.2»3
It has the following general structure:


                                       —CH —

   0
 CH2-CH-CH2-N/   \J-
                         PURAMER S
It is the tertiary amine and beta aliphatic hydroxyl groups that
are  believed  responsible  for the  sulfur  dioxide chemisorbent
properties of this  very unique polymer.   Hence,  sulfur dioxide
is removed  from  a flowing gas stream as a  sulfite or bisulfite
group.   Because  of this  chemistry,  moisture  is very important
for efficient sulfur dioxide  removal.   Best results are obtain-
ed at a relative humidity of 70-95 percent.

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     Early in our UCC Corporate  Research  funded program, direct-
ed  towards  developing Puramer  S  adsorbents for  use  in sulfur
dioxide removal from  industrial gas streams, as well as ambient
air,  it  was shown  that  a wide variety  of substrates,  coated
with Puramer S, could quantitatively remove and collect ambient
concentrations of  sulfur dioxide from properly  humidified gas
streams,  at high linear flow rates.4   During an  ambient air
filtration,  performed at a New Jersey Environmental Protection
Department Air Monitoring Station  located in Camden, New Jersey,
ambient  sulfur  dioxide  was quantitatively  removed  using  a
2-inch x  1/4-inch Puramer S-polyurethane foam  adsorbent,  for a
continuous period of 70 days.

     These  results  convinced  us that  low levels of  sulfur
dioxide  could  be collected  from  ambient air and  fixed by the
Puramer S structure, but we did not know exactly how to measure
the collected sulfur dioxide.  Early thermal analyses, performed
by  Dr.  B.  L. Joesten (Union  Carbide  Corporation,  Research and
Development Laboratories),  indicated  that  sulfur  dioxide could
be thermally desorbed and subsequently purged from the Puramer S
structure by heating  to  100°-110°C in the presence of nitrogen.
This  fact,  coupled with  the knowledge the sulfur dioxide can be
continuously measured by means of  a  Dohrmann Microcoulometric
Titration System, dictated that  initial contract research should
be  directed towards the optimization of the Dohrmann Sulfur
Analyzer as  well  as defining thermal  methods and equipment for
thermally generating the  collected sulfur  dioxide so  that it
can be quantitatively assayed.

     The  following  subsections  will be  devoted  to discussing,
in  detail,  the research  that has  led to  the successful develop-
ment  of  a Puramer S-based  method for measuring  the low levels
(nanogram quantities)  of  sulfur  dioxide required  for ambient
air monitoring.

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                             SECTION 4

          PURAMER S-BASED AMBIENT AIR MONITORING SYSTEM


     Conceptually the Puramer S-based monitoring system consists
of two  parts:   the  collector  and the analyzer.  The  collector
which is  located  at the air monitoring site consists of an air
mover, probably an  air  pump, a humidifier  to adjust  and  control
the  moisture  content  of  the  air prior  to  its entering the
Puramer S collector  device,  a  flow controller for adjusting the
air  flow  to  200 cc/minute  and  finally  a Puramer S filter device
consisting  of  two  1-inch by  1/4-inch  I.D.  plugs  of Puramer
S-coated polyurethane foam fitted into a  3-inch  by 1/4-inch O.D.
stainless tube.   These  collector tubes  are prehumidified with
enough moisture to assure quantitative sulfur dioxide adsorption
during the  initial  phase  of testing.   The collector tubes are
held  in  the  system  by 1/4-inch Swaglok tubing  connectors.   All
connection tubing are  made of  Teflon or  glass.   This system is
graphically illustrated in Figure 1.  After a 24-hour collection
cycle, the  Puramer  S tube is  removed, purged   with  oxygen-free
nitrogen  and carefully sealed  using  an  oxygen   impermeable end
cap  (probably  just  a pair of Swaglok tubing caps).   This spent
collector is  sent  to a central  testing laboratory where the
amount of collected sulfur dioxide is assayed.

     Presently, this assaying  procedure  is accomplished using
a thermal desorption  technique which  produces sulfur dioxide at
a rate  such that continuous gas  analysis  can   be accomplished.
The  total analysis   system consists of an  oxygen-free  nitrogen
purge gas, a gas flowmeter, a Bendix Flasher Unit and a Dohrmann
Microcoulometric Titration System,  connected in  that order.
All  gas  transfer  lines  are of 1/4 O.D. Teflon tubing and all
connections  are made  with  Swaglok tubing fittings.   This system
is shown' in  Figure  2.  The spent  collector is  carefully fitted
into  the Bendix  Flasher  Unit  and  collected sulfur  dioxide is
desorbed  by  programing the  flasher oven  temperature from 65°-
165°C.   The  desorbed sulfur dioxide is continuously  purged from
the  collector  device, using oxygen-free  nitrogen,  and  assayed
via  the  Dohrmann  analyzer.  Using  this two-part method, sulfur
dioxide  assays were determined  under  controlled  laboratory
conditions   (S02  loaded via permeation  tubes   and  zero air).
As the  data in Table  I  show,  excellent results were  obtained.

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                                            PURAMER S
                                            COLLECTOR
                                            DEVICE
                                  AIR FLOW
                                  CONTROLLER
       AIR PUMP
HUMIDIFIER
FIGURE 1.  PURAMER  S  BASED SULFUR DIOXIDE
          MONITORING SYSTEM - COLLECTOR SYSTEM.

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IN
Of




••
^m
ERT GAS
UNDER
FLOW
i^
•^
i
ME
^_
TER
1
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1 	 J 	 1

V 	 	 rll O O OO O
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DOHRMANN
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JBENDIX ANALYZER RECORDER
FLASHER


FIGURE 2. PURAMER S BASED SULFUR  DIOXIDE
         MONITORING SYSTEM - ANALYZER SYSTEM.

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     TABLE 1.  SULFUR DIOXIDE ANALYSIS  BY A  PURAMER S-
               BASED ANALYTICAL METHOD
     Loaded SO2            Assayed S02           S02 Recoveries
      nanograms            - nanograms           	- %
3782
4633
5254
6521
9994
11138
16870
17546
19385
22774
3559
4479
5233
6413
9547
11288
17346
17728
20208
22435
94
- 97
99
98
96
101
103
101
104
99

     It should be mentioned  that the total quantities of sulfur
dioxide being measured  in  this study represent analyses of syn-
thetic gas  streams,  containing sulfur dioxide levels from 13 to
80  yg/m3,  if collection is  carried out  for  24  hours at a flow
of  200  cc/minute.   These  sulfur dioxide concentrations are in
the  range that would be expected  in  actual ambient  air con-
ditions.  The accuracy of these  results,  although obtained under
controlled  laboratory  conditions,  certainly demonstrates  the
feasibility of monitoring  ambient levels of  sulfur dioxide with
a Puramer S-based method.

     To bring  the Puramer S-based sulfur dioxide  monitoring
system to  its present  level of technical development,  it was
necessary  to study  many  system variables  in detail.   These
studies are  individually discussed in  the following sections.

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                           SECTION 5

                          EXPERIMENTAL


     SULFUR DIOXIDE  ADSORPTION CHARACTERISTICS OF Puramer  S  -
     POLYURETHANE FOAM ADSORBENTS

     Once it was demonstrated that a Puramer S-polyurethane foam
adsorbent  could quantitatively  collect  sulfur dioxide  from  a
properly humidified  air stream,  it  was  necessary to determine
the  proper size  adsrobent  bed required  to  assure  efficient
collection of  sulfur dioxide for a  minimum of  24 hours  at the
maximum expected  level  of  ambient sulfur dioxide (2600 yg/m3).

     To properly  size  such a Puramer S-based  filter, collector
devices  were prepared by cutting  1-inch x 1/4-inch  plugs of
adsorbent from  foam  pieces coated with a wide range  of Puramer
S concentrations.   For test purposes,  these adsorbent plugs
were fabricated into filter  devices  by placing them into 6.4 mm
I.D., shrinkable Teflon tubing  fitted with 3 inch end pieces of
6 mm glass tubing.  Using sulfur dioxide loading equipment as
described in Section 6.1,  Procedures,  sulfur dioxide adsorption
characteristics of a number  of  various Puramer S  filter devices
were determined at  a  flow rate of  200  cc/minute  and  a  sulfur
dioxide  concentration of 3590 yg/m3.   During  these evalua-
tions, the water  content  of the feed gas stream was maintained
at approximately 22 mg H20/1 of air.

     As the data in Table 2 show, collection efficiency, defined
as the  percentage of  incident  sulfur dioxide removed  by the
adsorbent, was  100 percent  regardless of  filter  length  or the
amount of  active polymer contained on  the foam adsorbent.  How^
ever, the  total collection time for which quantitative removal
of sulfur dioxide  was  realized,  was  dependent on  the particular
adsorbent  tested..  At  least 2  inches of  foam adsorbent, con-
taining a  minimum  of 8.6  percent Puramer S will be required if
3590  vig S02/M3 of  air is  to  be collected  at 200  cc/minute
for a minimum of 24 hours.

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     TABLE 2.  ADSORPTION CHARACTERISTICS OF PURAMER S-POLY-
               URETHANE FOAM ADSORBENTS
.
Test.
No.
1
2
3
4
5
6
Filter
Length
2"
*
1"
2"
2"
2"
2"
Contained
Puramer S
2
8
8
8
8
18
.0%
.6%
.6%
.6%
.6%
.3%
Collection
Efficiency*
100%
1
1
1
1
1
00%
00%
00%
00%
00%
Collection
Time**
7
15
26
28
32
68
hrs.
hrs.
hrs.
hrs.
hrs.
hrs.
  *Based on the percentage of incident S02 removed.
  **Time at which zero S02 is measured in the filtered
   effluent gas (less than 7 yg/m3).

 ***Test Conditions;
      1.  Flow Rate - 200 cc/minute.
      2.  S02 Cone. - 3590 yg/m3 in zero air.
      3.  Relative Humidity - ^85% at 27°C.


      Since  actual  ambient  sulfur  dioxide  levels  will be  less
 than  3590   yg  F02/M3 of air,  a collector  device consisting  of
 2 inches  of foam adsorbent, coated with  a  minimum of  9  percent
 active polymer, will be more than  is  required  for 24-hour  col-
 lection  cycles.   Therefore,  future  laboratory  efforts  will
 center around  adsorbents containing  at least 9 percent  active
 polymer.

     Also,  it should be  pointed out that  tests  numbers 1, 3 and
 4 were run at 0,  23 and 48 days  after  the  foam adsorbent was
 prepared.    As  the  data  in  Table  2 show,  storage of Puramer  S-
 based adsorbent, prior  to  its  use as a  sulfur  dioxide  collec-
 tor,  does not  affect  its  overall  collection  efficiency and
within experimental  error,  does  not significantly  reduce  col-
 lection times.


                               10

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     EFFECT  OF  DESORPTION  TEMPERATURES  ON  SULFUR  DIOXIDE
     RECOVERIES

     Having  shown  that  properly sized  Puramer S-polyurethane
foam adsorbents  can  quantitatively  collect sulfur  dioxide from
air, efforts were directed  towards  developing an analytical
method  for measuring the  actual amount  of collected  sulfur
dioxide.   As previously mentioned,  this assaying method  was
to be  the result of  controlled  thermal desorption of  sulfur
dioxide using  a Bendix  Flasher and  continuous  sulfur  dioxide
Analysis  via  a  Dohrmann  MCTS  (see complete  method  in  Section
6.3, Procedures).

     As the data in  Table 3 show, sulfur dioxide recovery from
a Puramer S-urethane  foam collector (2 inches long-M2%  Puramer
S), previously blanked to 170°C to assure that no sulfur  dioxide
was present prior  to  loading, was highly dependent  on the max-
imum desoprtion  temperature  used  to  produce  sulfur  dioxide  for
subsequent assay.  At  160°-165°C, recoveries were low and quite

     TABLE 3.  THE EFFECT OF DESORPTION TEMPERATURE ON SULFUR
               DIOXIDE RECOVERIES


Loaded SO2
ng.
7,217
9,478
19,537
23,485
35,924
4,633
22,774

Assayed S02
ng.
6,382
6,440
15,040
23,292
34,400
4,479
22,435

Recovery
% .
88
68
77
99
96
97
99
Maximum
Desorption
Temp. , °C
160°
165°
165°
200°
190°
170°*
170°*
*Purge gas heated to 160°C prior to entering the Bendix Flasher
 Unit.
                               11

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variable, while  at 190°C  and  200°C,  recoveries were quantita-
tive.   However,  being  concerned about  possible  filter decom-
position at  these  high  temperatures,  which would foul the MCTS
cell,  attempts  were made to  reduce the maximum  desorption
temperature  by  using  preheated  purge  gas.  As  the data show,
quantitative  sulfur  dioxide recoveries  were  realized  at 170°C
when preheated CM60°C)  gas was employed.

     Using a maximum desorption temperature of  170°C, continuous
series of  sulfur  dioxide assays can be  run without fouling the
MCTS  sulfur  cell.    Until future laboratory  studies  dictate a
change in thermal  desorption technique,  170°C will be the final
temperature  used to  regenerate  sulfur  dioxide for all Dohrmann
MCTS analyses.


     EFFECT  OF PURAMER  S CONTENT ON  SULFUR DIOXIDE  RECOVERY
     EFFICIENCY

     In  order  to study  the effect  of  Puramer S content (poly-
urethane foam  substrate)  on the overall  sulfur dioxide recovery
efficiencies,  using  thermal  sulfur  dioxide desorption and sub-
sequent  Dohrmann  MCTS  analysis, a  series of assays  were run
using  2-inch  foam adsorbents  containing various  amounts of
Puramer  S.   Exact sulfur  dioxide  loadings were obtained using
a  calibrated sulfur dioxide  permeation  tube  (see  Section 6.1
for  a  detailed description of the loading  method).  As the data
in  Table 4  show,  foams  containing  4.3 percent and 8.9 percent
active polymer gave  sulfur dioxide  recoveries of 88-91 percent
while  filters  prepared from 12  percent and 18 percent Puramer S
foams  consistently  gave  quantitative sulfur dioxide recoveries
over  a wide  range  of  sulfur  dioxide  loadings.   The data also
indicated  that higher  loadings result  in more quantititative
recoveries regardless of Puramer S content.   It was fortunate
that  higher  loadings resulted  in  better  recovery  efficiencies
since  these and even  higher loadings are more realistic, in
actual ambient  applications,  than  the  lower levels  measured
in this  study.

     The poorer  recoveries  obtained  when low Puramer S content
adsorbents were  tested might  be due to  sulfur dioxide reaction
with  the urethane substrate.   Using  low amounts of  active
polymer  it would be expected that more urethane  structure would
be  exposed  to the sulfur dioxide-water  than  at  the  higher
Puramer  S  coatings.   If sulfur dioxide were  to  react  in such
a way  as to render the sulfur dioxide stable and  no longer
thermally regenerable,  low  recoveries  would be realized.   More
will be  said about sulfur dioxide loss due to reaction with the
adsorbent in the section discussing adsorbent cycling.  Preven-
tion of  sulfur dioxide   loss by reaction can be achieved using
foam coated with  at least 12 percent  Puramer S.
                               12

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     TABLE 4.   EFFECT OF PURAMER S CONTENT ON SULFUR DIOXIDE
               RECOVERY EFFICIENCY
Puramer S
Content
18
18
12
12
12
12
12
12
12
9
9
4
4
Loaded S02
ng.
4,633
22,774
3,782
4,633
6,521
9,994
16,870
17,546
22,774
3,853
5,524
3,790
6,488
Assayed S02
ng.
4,479
22,435
3,559
4,479
6,413
9,547
17,346
17,728
22,435
3,387
4,855
3,335
5,917
Recovery
Efficiency
97
99
94
97
98
96
103
101
99
88
88
88
91
*A11 Puramer S collectors treated for 5 minutes at 170°C and
 a 200 cc/minute N2 purge to assure that no S02 wss contained
 on the adsorbent prior to S02 loading.
                               13

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     EFFECT OF COLLECTOR CYCLING ON THE SULFUR DIOXIDE RECOVERY
     EFFICIENCY

     Another parameter  that  was studied during this laboratory
research program was  the effect of  cycling or re-use  of the
filters  on  sulfur dioxide recovery.  This study not only showed
that reuse was possible, but  probably  desirable.

     Using  collector  devices  containing  2-inch  lengths  of
Puramer S-urethane foam  adsorbents,  containing  4 -percent,
9  percent,  and  15  percent active amine polymer, sulfur dioxide
was  carefully  loaded and then  analyzed  via thermal desorption
and  subsequent Dohrmann  MCTS  analysis  of  the sulfur dioxide in
the  effluent purge gas  (see Sections 6.1 and 6.3 for details of
these experimental procedures).   After all the collected sulfur
dioxide  was desorbed and measured, the  collector  devices were
prehydrated by  passing  moisturized  nitrogen  ( ^22 mg  H20/&
through the device for  5  minutes  at 200  cc/minute and the
analytical cycle repeated..

     The data  in Table 5 show  that  sulfur  dioxide recoveries,
via  thermal  treatment,  were  always  lower  than expected for the
first  collection-assay  cycle.   Once  again  the recoveries were
lowest  for  adsorbents  containing  the  least  amount  of Puramer
S. In  every case,  however,  second,  third  and even fourth cycle
treatment  resulted  in quantitative  recoveries.  Cycling the
filters  through  the  desorption part of this process showed that
the  improved recoveries  were  not  the  result of residual sulfur
dioxide  left on  the collector and subsequently measured on the
next cycle.

     The low,  first cycle results again  indicated  that sulfur
dioxide was reacting with some functional group on the adsorbent
which  renders  it nonregenerable  and  hence,  not  available for
MCTS detection.   Once  this  small amount of  reaction  was com-
pleted,  however, the functional group or reactive  site  was no
longer  available  for sulfur dioxide attack and,  therefore,
additional  cycling  resulted   in  quantitative assays.   Efforts
will be needed  to  develop  a pretreatment for the Puramer S
adsorbent so  that  quantitative  recoveries  can be  realized in
the first cycle.  Also,  this  study showed that EPA could recycle
Puramer  S  collector  devicies  without affecting  subsequent
analysis of ambient  sulfur dioxide.
                               14

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TABLE 5.  PURAMER S ADSORBENT CYCLING VERSUS
          SULFUR DIOXIDE RECOVERY EFFICIENCY
Cycle
1
2
3
1
2
3
1
2
3
4
Puramer S
%
4
4
4
9
9
9
15
15
15
15
Loaded SO2
ng.
6,488
3,683
3,452
3,853
7,359
5,557
24,120
24,228
24,084
24,084
«
Assayed S02
ng.
5,917
3,650
3,365
3,387
7,572
5,407
22,320
23,599
24,000
23,441
Recovery
%
91
99
98
88
103
97
93
97
100
97
                           15

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     EFFECT  OF PREHYDRATION  ON THE  SULFUR  DIOXIDE RECOVERY
     EFFICIENCY OF PURAMER S ADSORBENTS

     Very early  in  our research, it was shown  that  many of the
low sulfur  dioxide  recoveries were  the direct result of  a low
moisture  content  on  the  Puramer S-polyurethane  foam adsorbent
prior to sulfur dioxide loading.   This was particularly true for
Puramer S adsorbents  being  used  to  study filter cycling  and its
effect on recoveries.   The low  preloading  moisture,  results in
poor adsorption efficiency  early in  the loading cycle.   Because
this laboratory effort  used short filter loading periods,  using
high concentrations of  sulfur dioxide  (3600 yg S02/M3 of  air),
the effect  of  moisture on the filter prior  to  loading was mag-
nified, since there was not enough time, early in the collection
cycle, during which water, needed for sulfur dioxide adsorption,
could be adsorbed.

     As the  data  in Table 6 show, low sulfur dioxide recoveries
due to  low  pre-sulfur dioxide loading  moisture could be easily
remedied  by  simply  prehydrating  the collectors by  passing 200
cc/minute of moisturized nitrogen  (^22 mg  H20/ji)  through the
device for 5 minutes.   (Longer prehydration times did not effect
recoveries.  Prehydration of Puramer S-based sulfur  dioxide
collectors is now standard procedure.


     TABLE 6.  EFFECT OF PREHYDRATION ON THE SULFUR DIOXIDE
               RECOVERY EFFICIENCY OF PURAMER S ADSORBENTS


        Puramer S   Prefilter    Loaded    Assayed   Recovery
Cycle    Content    Hydration    S02-ng    S02-ng      -  %


  7       8.9          No        3,604     2,771       77

  8       8.9          Yes       6,587     6,708      102

  3      12.0          No        5,016     4,592       91

  4      12.0          Yes      19,385    20,208      104
                               16

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     Having  completed most  of  the  more  important parameter
studies, a viable  Puramer S-based analytical procedure has been
developed.   This method  can  quantitatively assay known amounts
of  sulfur  dioxide  which are  carefully loaded  onto  adsorbents
under  controlled laboratory  conditions.    The  method,  however,
assumes  that actual thermal  desorption and subsequent Dohrmann
MCTS analysis  of the loaded sulfur dioxide is carried out imme-
diately  after  collection.  This is not at all practical because
there are sometimes  many  days that elapse between sulfur dioxide
collection and final  assay.   This delay  is  caused  by shipment
of  spent collectors from the air monitoring site to a central
laboratory for final testing.  Before  a  study  of the effect of
filter  storage time and  temperature,  after sulfur dioxide col-
lection,  on  the  subsequent recovery efficiency  is  detailed,  a
summary  of  the parameters  required to assay sulfur  dioxide, by
a Puramer  S-based method,  is appropriate.   This summary  can be
seen in  Table  7.
     TABLE 7.  PURAMER S-BASED SULFUR DIOXIDE
               ANALYTICAL  SYSTEM PARAMETERS
     Collection  of
          Filter  Used  -  2"  x  1/4" Puramer S-polyurethane foam.

          % Puramer  S  -  12-15%.

          Prehydration - Yes.

          % Relative Humidity  in Gas Stream - 85% at 25°C.

          Gas  Flow Rate  -  200  cc/min.


     Assaying  of  SO 9

          Desorption Temp.  -  50° to 170°C.

          Purge Gas  -  Oxygen-free nitrogen.

          Purge Gas  Flow -  135 cc/min.

          S02   Measurement  -  Dohrmann MCTS or equivalent.
                                17

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     Using  these parameters,  sulfur  dioxide  carefully  loaded
on Puramer  S-polyurethane foam  adsorbents can be  assayed  over
a wide  range  of concentrations.   A representative  summary  of
these results are shown in Table 8.
     TABLE 8.  SULFUR DIOXIDE ASSAYS VIA A PURAMER S-BASED
               METHOD
24 Hour
Average SOo
Conc.-ug/M3
13.1
16.1
18.2
22.6
34.7
38.7
58.6
60.9
67.3
78.1
79.1
83.6
83.6
83.6
84.1
Total
Collected
S0?-ng
3,782
4,633
5,254
6,521
9,994
11 ,138
16,870
17,546
19,385
22,500
22,774
24,084
24,084
24,084
24,228
Assayed
S02~ng.
3,559
4,479
5,233
6,413
9,547
11,288
17,346
17,728
20,208
22,164
22,435
23,760
24,072
23,280
23,592
S02
Recovery
- %
94
97
99
98
96
101
103
101
104
99
99
99
100
97
97
                               18

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     EFFECT  OF STORAGE  ON SULFUR  DIOXIDE RECOVERY  EFFICIENCY

     Having successfully developed a method for assaying ambient
levels of sulfur dioxide, collected by a Puramer S-based adsorb-
ent under ideal laboratory conditions, efforts were  concentrated
on determining whether or not  the  method was  applicable under
reallife conditions.  The  first phase of this study  was to
determine the  effect of  storage  time and temperature of spent
adsorbent  (sulfur  dioxide  loaded),  on subsequent  recovery
efficiency.

     Puramer  S-polyurethane  foam  adsorbents   were  loaded  with
various  amounts  of sulfur dioxide using  the procedure outlined
in Section  6.1.   The spent  filters  were sealed,  using rubber
septa and stored at 25°-27°C, 45°C,  0°C  and -30°C.   At various
storage  times  the amount of  loaded sulfur dioxide was measured
and  recovery  efficiencies  determined.    These initial storage
data are summarized  in Table 9.

     These  data  show that storage of  spent Puramer S-based col-
lectors  resulted  in significant  reductions  in overall  sulfur
dioxide  recoveries.  Sulfur  dioxide decay was minimized,  to
an acceptable level, via  sub-zero  storage  at -30°C.   Also,
these data  showed  that  the  rate of  decay was closely related
to the  storage  temperature.  At  0°C,  84 percent  of the col-
lected sulfur  dioxide could be assayed  after 21 days of storage
while only  33 percent could  be  found  after  24 days at  45°C.
Storage  at  25-27°C also resulted  in a  steady loss  of  sulfur
dioxide, with  only  68 percent  of  the collected sulfur dioxide
available for  measurement after 21  days.

     The results  seem to suggest that  sulfur dioxide was being
destroyed via  a  chemical  reaction.  It  was believed that oxygen
present  in  the free  void  space  of  the collector devices could
result  in  oxidation  of sulfur  dioxide to  sulfur  trioxide.
Sulfur trioxide  is not thermally desorbable from Puramer S and
if it were, it  could  not be  measured by the Dohrmann analyzer
because the sulfur cell employed is  specific for sulfur dioxide.
Using very  simple  calculations, it was  shown that the 3-inch by
1/4-inch collector  tube  could contain enough  oxygen to convert
all  the  sulfur  dioxide,  normally loaded,  to  sulfur trioxide.
This contained oxygen could  be eliminated  via purging  with an
oxygen-free   inert  gas,  but another calculation^ quickly showed
that air permeation  through the rubber septum  caps,  used to seal
the  spent  collector  tubes  could  allow  enough  oxygen to enter


                               19

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TABLE 9.  EFFECT OF POST-COLLECTION STORAGE ON PURAMER S
          ADSORBENT RECOVERY EFFICIENCY

Storage
Time-days
0
6
0
5
6
26
26
21
21
21
2
24
2
3
6
12
Storage
Temp.-°C
25-27
25-27
25-27
25-27
25-27
25-27
25-27
0
0
0
45
45
-30
-30
-30
-30
Loaded
S00 ng.
^
22,774
8,914
16,840
24,214
10,246
31,982
12,794
25,545
14,458
17,424
13,190
21,874
14,054
22,500
24,036
19,176
Assayed
S00 ng.
^*
22,435
7,840
17,346
22,568
8,267
21 ,600
8,400
21,360
11,520
14,640
7,680
7,200
15,240
22,128
23,366
18,408
Recovery
%
99
88
103
93
81
68
66
84
80
84
58
33
101
98
97
96
                          20

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the tubes, in 24 hours, to  completely convert all the contained
sulfur dioxide to trioxide.

     Having a full appreciation for the effect of oxygen  on  the
decay of sulfur dioxide fixed on a Puramer S filter, a study  was
run on  spent adsorbents  stored at 25°-27eC  in  an oxygen-free
atmosphere.  To accomplish this study, spent filters were  purged
for 10  minutes with  oxygen-free  nitrogen,  again sealed with
rubber  septa  and  stored at  ambient temperature  in  a  container
that  was continuously purged with oxygen-free nitrogen.  As
shown  in Table 10, sulfur dioxide decay  was reduced by min-
imizing  oxygen  during storage.   However,  some decay  still  was
taking  place  since  only 93-95 percent of  the collected  sulfur
dioxide was measured after 5-7 days.

     TABLE 10.  PURAMER S—SULFUR DIOXIDE STORAGE STABILITY
                IN AN  INERT ATMOSPHERE
Storage
Time-days
0
6
26
1
4
5
7
Loaded
SO -ng.
2
22,774
8,914
31,982
24,084
24,144
24,096
23,092
Assayed
SO -ng.
2
22,435
7,840
21,600
22,320
22,046
22,800
21,476
Recovery
- %
99
88
68
93
91
95
93
Storage
Atmosphere
Air
Air
Air
Oxygen Free
Oxygen Free
Oxygen Free
Oxygen Free
     Again,  looking  for possible sources  of oxygen  in our
overall  test system,  it was  pointed out that  enough oxygen
could  be dissolved  in the rubber end seals,  used to cap the
spent  filters, to convert approximately  38,000 nanograms of
sulfur  dioxide to  undetectable  sulfur  trioxide.6   This was
more sulfur  dioxide  than  normally  collected  by  the Puramer S
adsorbents.  These storage  studies  were  very  encouraging  since
they suggested that by using a properly designed  collector seal
to  avoid oxygen  contamination, sulfur dioxide  decay  would be
eliminated and spent Puramer S  filters would  have  the  required
stability, regardless of storage temperature.

     A preliminary program to develop  an improved  seal for
spent Puramer  S  adsorbents, resulted  in a seal consisting of

                               21

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glass  rod end  butts that  were tightly held to  the stainless
steel  collector via small  sections of  a  Teflon sleeve.   These
seals were firmly held in place using vinyl  tape (see Figure 3).
                        PURAMER S
            TEFLON SLEEVE
                               \
   GLASS ROD
   BUTT SEAL
STAINLESS
STEEL TUBING
             FIGURE  3. PURAMER S FILTER SEAL
                               22

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These  seals were put  in place  following  a 20-minute collector
purge  with oxygen-free  nitrogen.  Using filters fitted  with
these  end seals, storage stability tests were  run  at  25°-27°C

n^n^n0   day?'   V, the data  in Table 11 snow' this method of
preparing  spent collectors for  ambient  storage proved  very
effective.                                                     •*
     TABLE  11.   EFFECT OF PROPER SEALING ON THE STORAGE
                 STABILITY OF SPENT PURAMER S ADSORBENTS
Storage Time
-days
0
0
0
1
1
3
3
8
8
8
Note — Storage
Loaded S02
-ng
27,704
23,114
18,232
18,521
18,259
15,216
30,772
20,683
20,623
20,472
temperature at
Assayed S02
-ng
26,170
23,117
18,292
17,905
17,753
14,954
30,609
19,532
19,557
20,391
25°-27°C.
SO 2 Recovery
94.5
100.0
100.3
96.7
97.2
98.3
99.5
94.4
94.8
99.6

     Although  these data  show that  the  glass  butt  sealing tech-
nique  was effective  for  25°-278C storage, preliminary results
at 40°C  indicate  that sulfur  dioxide  decay still occurred at an
undesirable  rate.   Sulfur dioxide recoveries of 88 percent and
74 percent  were obtained  for sealed  collectors  stored at 40°C
for  1  and  3 days respectively.  This decay in  recovery was
probably due to a small amount of oxygen contamination  resulting
from the  loosening  of the end  butt  seals  at 40°C.  By placing
properly  sealed  spent filters in sealed jars, that were purged
with oxygen-free  nitrogen, sulfur dioxide decay  due to oxygen
contamination  was  minimized  and  recovery  of 95-98 percent was
obtained for a small number of samples.
                               23

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     This finding  again suggested the need for a seal  that would
completely  eliminate oxygen  contamination  of spent filters.
Success in developing such an end seal would  bring the Puramer
S-based sulfur  dioxide  monitoring  method to  a point where  it
would  be  functional  under real-life  ambient  condition.   This
final  Puramer S-based sulfur  dioxide method would  eliminate
almost all of the  troublesome shortcomings of the presently used
West-Gaeke method.
                              24

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                           SECTION 6

                           PROCEDURES


     METHOD  OF LOADING  SULFUR DIOXIDE ON PURAMER  S  ADSORBENTS


A.  Purpose:

     The purpose  of this procedure  is  to accurately  load  known
     amounts of S02 on Puramer S adsorbents.


B.  Equipment:

     1.  A calibrated S02 permeation tube.

     2.  A  cylinder of  zero zir  fitted  with a properly  sized
         pressure regulator.

     3.  A  cylinder of  nitrogen fitted  with a properly  sized
         pressure regulator.

     4.  A constant temperature water bath.

     5.  A flowmeter and needle valve flow regulator.

     6.  A  glass,  U-tube  holder fitted  with inlet and outlet
         connectors.

     7.  Two calibrated thermometers (range 7-31°C).

     8.  A  Dynasciences  S02 Pollution  Monitor  fitted  with
         a 0-0.5, 0-1.5, 0-5.0 ppm S02 sensor.

     9.  A 10 mv. strip-chart recorder.

    10.  1/4" I.D. Teflon tubing.

    11.  1/4" nylon tubing fittings.

    12.  Two,  Drechsel gas  washing  bottles.   (S.G.A.  JB-1370.)
                               25

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C.  Equipment Setup:   Puramer S Adsorbent Prehydrator.

     1.   The prehydrator  consists  of  a  cylinder of  nitrogen,
         fitted with  a  properly  sized pressure  regulator  that
         is  connected to  a gas  flowmeter-regulator using  1/4"
         I.D. Teflon  tubing.   The  flowmeter-regulator  is  con-
         nected to a  250  ml,  Drechsel gas washing  bottle  con-
         taining approximately  200  ml of  distilled water,  again
         using  1/4"  I.D.  Teflon  tubing.    The off-side of  the
         gas washing bottle is fitted  with a  1/4" nylon tubing
         fitting into which is placed the device containing  the
         Puramer S-based adsorbent.

     2.   Using a gas  flow  of  200 cc/minute, moisture  is loaded
         onto the adsorbent for 5 minutes.
D.   Equipment  Setup:   Puramer S Adsrobent  S02  Loading  System.

     1.  The S02  loading  system  consists  of a  cylinder of
         zero air,  fitted  with  a properly  sized pressure  reg-
         ulator,  a  flowmeter-regulator,  a 250 ml,  Drechsel  gas
         washing  bottle containing approximately  200  ml of
         distilled  water,  a  glass  U-tube  (containing glass
         beads in  the inlet  half  and an SC>2  permeation tube
         and thermometer  in the off side) immersed in a constant
         temperature water  bath, a  Puramer S  adsorbent  device
         holder,  a  Dynasciences  SC>2  Pollution Monitor  fitted
         with a 0-0.5,  0-1.5, 0-5.0 ppm SC>2  sensor and a 10
         mv. strip-chart recorder.    All of this  equipment is
         connected   together,   in  the order  listed,  using  1/4"
         I.D. Teflon  tubing  and  1/4" nylon  tubing fittings.

     2.  At a  constant  flow  of 200  cc/minute,  humidified  zero
         air is passed  over   a  calibrated  S02  permeation  tube
         (30°4'0.10C)  until a constant  S02 concentration is
         measured  by  the  Dynasciences  SC>2 monitor.   Once  a
         stable  SC>2  concentration  is realized,  Puramer  S
         adsorbents  can  be  accurately loaded with  SC>2 by
         inserting  a  Puramer S filter device into  the gas
         stream between the permeation tube and the  Dynasciences
         monitor;   By  measuring the filtered effluent gas, quan-
         titative  collection or  removal  of  S02  by the Puramer  S
         adsorbend  can be assured.  The loading time is recorded
         by a stopwatch  in  seconds.   The quantity of loaded  SC>2
         can be varied   by varying  the loading time.   Loaded
         Puramer S  devices are  sealed with  a proper sealing
         device.

     3.  SC>2 Loading = Permeation Rate (ng S02/min)  x Time (sec)
                                                         60
                              26

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     CALIBRATION OF SULFUR DIOXIDE PERMEATION TUBES

A.  Purpose:

     The purpose of  this method is to accurately determine  the
     S02 delivery rate  of a permeation  tube  under the exact
     flow  and temperature  conditions used when loading SO?
     onto Puramer S adsorbents.

B.  Equipment:

     1.  The  exact  permeation tube system described in  6.1-D.

     2.  The S02 permeation tube to be  calibrated.

     3.  A  Dohrmann  Microcoulometric  Titration  System  equipped
         with  a  Model T-300P-oxidative sulfur  titration cell.

     4.  1/4" I.D.  Teflon tubing.

C.  Equipment Setup and Procedure

     1.  Using as  short  a piece of 1/4" O.D. Teflon tubing as
         possible,  connect the  exit side of  the  S02  permeation
         system to  the microcoulometric titration  cell.

     2.  Before actually  making this  connection,  set the Dohr-
         mann  Microcoulometric  Titration  System parameters as
         described  in the  instruction manual.   This  usually
         means a Bias  setting of  140-150  ma. and a  coulometer
         gain of 200.

     3.  After the microcoulometer is properly adjusted,  connect
         the  S02  permeation  system directly  to  the titration
         cell and  set  the permeation  conditions  of  temperature
         and  flow  to  those  to be used in  loading  Puramer S
         adsorbents.

     4.  At  a  microcoulometer ohm setting of 10,  continuously
         measure  the nanograms of sulfur  in the synthesized
         gas  stream using the Dohrmann  recorder  and stroke
         integrator  (each  full stroke =  100  counts).   Con-
         tinue this  measurement until a stable  recorder read-
         out  (constant  sulfur  level   in gas) is realized for
         a  minimum analysis period of 30 minutes.


                              . 27

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D.  Calculation of  S02 Permeation Rate

                          Total Sulfur Conts x 4
                Rate  _
                Kate    Analysis Time — (mins. )  x  ohm setting



     Permeation Rate  of S02 = nanograms S02/minute.
                              28

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     THERMAL  DESORPTION METHOD  FOR ASSAYING  SULFUR DIOXIDE
     ADSORBED ON PURAMER S-BASED ADSORBENTS


A.  Purpose:

     The purpose of  this method is  to  quantitatively desorb
     S02  from  Puramer  S  adsorbents so that the  S02  can be
     assayed  using  a  Dohrmann Microcoulometric S02  Titration
     System.


B.  Equipment:

      1.  A cylinder of oxygen-free nitrogen,  fitted with a
          properly sized pressure  regulator.

      2.  A Bendix Flasher Unit (Model H/S 10).

      3.  3-inch  x  0.25-inch  stainless  steel collector tubes
          containing  Puramer  S-polyurethane foam adsorbent
          (2-inch x 1/4-inch plug).

      4.  A  25-foot  x   1/4-inch  O.D. coil  of  copper tubing
          filled with small glass  beads.

      5.  A hot plate.

      6.  A 0-250°C thermometer.

      7.  A  Bell jar  containing  high-temperature   silicon  oil
          stabilized with ionol.

      8.  A flowmeter.

      9   A Dohrmann Microcoulometric Titration System, equipped
        *  with  a Model  T-300P oxidative  sulfur  titration cell.

     10.  1/16-inch O.D.  Teflon tubing and stainless steel
          Swaglok tubing connectors.
                               29

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C.  Equipment  Setup:

     1.   The  system used to  assay the  SC>2  collected  on a
         Puramer  S-based  adsorbent  consists  of  a  cylinder of
         oxygen-free nitrogen, fitted  with a properly sized
         pressure  regulator,  a purge gas  preheater  made up of
         25 feet of  1/4-inch  O.D.  copper tubing filled  with
         glass beads  and immersed  in a  silicon oil bath heated
         to 160°C  via  a stirrer-hot plate, a Bendix  Flasher
         Unit  (Model H/S  10)   and  a Dohrmann  Microcoulometric
         Titration  System equipped with  a Model  T-300P oxidative
         sulfur  cell.    All  parts of the  system  are connected
         via 1/16  inch  O.D.  Teflon  tubing  using stainless steel
         Swaglok fittings.


D.  Procedure:

     1.   Using the  above described  setup,  set the nitrogen flow
         at ^135 cc/minute.

     2.   Set the gas preheater  temperature  at 160°C.

     3.   With the  Bendix Flasher Unit  in a gas bypass mode,
         set the Microcoulometer  parameters as  per the  instru-
         ment  instruction manual.   Set  ohm  range   at  10.

     4.   Place the spent Puramer  S collector device  in  the
         Bendix  Flasher Oven  and  set the  oven temperature  at
         50°C.

     5.    Change  the  Bendix  Flasher Unit  to  the  analysis  mode
         and  continuously measure  the  amount of  S02  in  the
         collector  purge gas.

     6.   Increase  the  Bendix Flasher Unit  oven temperature  in
         increments of  5°C  so  as to cause thermal  generation
         of S02  at a  rate  that can be  recorded  by  the  S02
         analyzer.

     7.   Program the oven temperature to  170°C.

     8.   Continue  the  analysis until no more  S02  is measured
         (Dohrmann  recorder  back   to  the  original baseline
         setting).

     9.   Cool  the  Flasher oven to   50°C using  compressed  air.
                              30

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E.  Calculation of Assayed S02:

     1.  Determine  the  total  number  of  SC>2 integration  counts
         recorded by  the disc-integrator.

     2.  Nanograms SC>2 = 4 x total counts
                              ohm setting

     3.  %  SO,  Recovery = assayed SOp x 100

                             loaded S00
                                 31

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     PREPARATION OF PURAMER S-POLYURETHANE FOAM ADSORBENT AND
     SUBSEQUENT COLLECTOR DEVICES


A.  Materials and Equipment Needed:

     1.  45 pores per inch polyurethane foam (Paramount).

     2.  15 percent aqueous solution of specification N-glycidyl
         piperazine oligomer.

     3.  Vacuum Oven.

     4.  Buchner funnel and flask.

     5.  Rubber Dam.

     6.  Source of vacuum.

     7.  8" x 8" x 3" glass dish.

     8.  Distilled water.


B.  Procedure:

     1.  Cut a 6" x 6" x  1" piece of  45  pores  per  inch  polyure-
         thane foam.

     2.  Wash  thoroughly  with  distilled  water,   squeeze  out
         excess  water  and dry  to  constant weight  in a  vacuum
         oven set at 120°C.

     3.  After weighing the washed  foam,  saturate  the foam with
         a 15 percent aqueous  oligomer solution by  immersing the
         foam  in an 8"  x  8"  x 3"  dish  filled with solution.

     4.  Remove  excess  oligomer solution by  placing the  foam
         piece  in  a Buchner  funnel,   covering  the  funnel  with
         rubber darning and  pulling  full  house vacuum (^28"Hg).
         The excess solution  is  collected in  the Buchner flask.

     5.  Place the  oligomer-coated  foam  into  a vacuum  oven and
         hold for 16 hours at  120°C  and 28" Hg.
                               32

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6.  Remove the  Puramer S-coated foam  from  the  oven,  cool
    in a  desiccator and weigh  to  determine  the  amount  of
    Puramer S.

7.  %  Puramer S  =  Wt. of Coated Foam  - Wt. of Foam x  1QO
                         Wt. of Coated  Foam


8.  Cut  out  1-inch x 1/4-inch plugs  of Puramer  S-poly-
    urethane foam  adsorbent  using a No.  4 cork  borer.

9.  Place two 1-inch plugs into a 3" x  1/4"  stainless steel
    tube by  carefully pushing one plug  into  each end of the
    3-inch  tube.    This  then  is the SC>2 collector device.
                           33

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                            REFERENCES
1.   Cotter,  R.  J.    "Engineered Adsorption  Surfaces—Selective
    Adsorbents for Sulfur  Dioxide Based on  Polymers  Containing
    Amino and Hydroxyl Groups."  Project Report, File No.  3328,
    June 23,  1972.

2.   Keogh,  M. J.   "Engineered  Adsorption  Surfaces—Characteri-
    zation  Studies on N-Glycidly Piperazine  Oligomer."   Project
    Report,  File No.  3892,  December 4,  1973.

3.   Smith,  S. G. Jr.  "N-Glycidly  Piperazine Oligomer:   A  Proc-
    ess Study and Subsequent Scale-Up to Pilot  Plant Equipment."
    Project  Report,  File No. 4225,  November 8,  1974.

4.   Heitz,  W. D.  "SC>2 Adsorbent Fabrication."  Project  Report,
    File No.  3819,  September 21, 1973.

5.   Stenstrom,  John.    Private communication,  September  1976.

6.   Stenstrom,  John.    Private communication,  September  1976.
                               34

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                                   TECHNICAL REPORT DATA
                            (rlcasc read Instructions on the reverse before completing!
 REPORT NO.

 EPA-600/2-79-205
             3. RECIPIENT'S ACCESSION-NO.
 HTLE AND SUBTITLE
 OLID SORBENT FOR  COLLECTING ATMOSPHERIC SULFUR DIOXIDE
             5. REPORT DATE
                December 1979
                                                           6. PERFORMING ORGANIZATION CODE
 AUTHORiS)
                                                           8. PERFORMING ORGANIZATION REPORT NO.
 R.  Cotter and S.  Smith Jr.
 PERFORMING ORGANIZATION NAME AND ADDRESS
 nion Carbide Corporation
;hetnicals and Plastics  Research Laboratories
Sound Brook, Hew  Jersey  08805
             10. PROGRAM ELEMENT NO.

              1AD712   BE-03  (FY-77)
             11. CONTRACT/GRANT NO.

              68-02-1782
 2.SPONSORING AGENCY NAME AND ADDRESS
 Environmental Sciences Research Laboratory - RTP, NC
 iffice of Research  and Development
U.S. Environmental  Protection Agency
 Research Triangle  Park, NC  27700
                                                            13. TYPE OF REPORT AND PERIOD COVERED
              Final   5/75-11/77
             14. SPONSORING AGENCY CODE
              EPA/600/09
 5. SUPPLEMENTARY NOTES
 6. ABSTRACT
     A solid sorbent for collecting  atmospheric S02 was evaluated as part of an
overall effort  to develop a replacement method for the West-Gaeke method presently
used to measure 24-hour ambient sulfur dioxide concentrations in ambient air.
Research showed that a' solid sorbent,  consisting of Puramer S coated open cell
polyurethane foam, can be used to  fix  the quantities of sulfur dioxide that  would
be collected if typical ambient air  was filtered for 24 hours at 200 cc/min.  The
method of assaying sulfur dioxide  collected by the sorbent consisted of controlled
 thermal desorption of sulfur dioxide followed by continuous analysis using a
Dohrmann microcoulometric titration  system.  Troublesome sulfur dioxide decay,
occurring during post collection storage, was primarily the result of oxidation.
Decay was minimized, to an acceptable  level, by properly sealing the spent Puramer
S collector devices to prevent oxygen  contamination from contacting the sorbent
prior to thermal  desorption and subsequent assaying.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.lDENTIFIERS/OPEN ENDED TERMS
                                                                           COSATi Field'Group
*Air pollution
*Su?fur dioxide
*Sorption
 'Sorbents
 Foam
 'olyurethane  resins
Evaluation
                             13B
                             07B
                             07D
                             11G
                             111
 3. DISTRIBUTION STATEMENT

        RELEASE  TO PUBLIC
EPA Form 2220-1 (9-73)
19 SECURITY CLASS (ThisRepot
    UNCLASSIFIED
43
                                               20 SECURITY CLASS (This page!
                                                  UNCLASSIFIED
                                                                         22. PRICE
                                             35

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