United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-110 July 1984
&ERA Project Summary
Methods of Chemical Analysis
for Oil Shale Wastes
J. Wallace, L Alden, F. S. Bonomo, J. Nichols, and E. Sexton
Several methods of chemical analysis
are described for oil shale wastewaters
and retort gases. These methods are
designed to support the field testing of
various pollution control systems, and
emphasis is therefore placed on
methods which are rapid and sufficient-
ly rugged to perform well under field
conditions.
Ion chromatography has been
developed as a technique for the minor
non-carbonate inorganic anions in
retort water, including SO= 4. NO"3, S:,
SCN-, and total sulfur (S). Acetate, Cl,
SO:4, NO 2, and PO3'4 can be observed
with this technique but cannot neces-
sarily be separated if present simultane-
ously.
The method recommended for sulfide
is a potiometric titration with Pb(ll).
SCN , S2O=3, SO-4, CI-, CO=3, NH3, and
OH' were shown not to interfere with
this technique. The freezing point
depression is used to determine the
total solute content in retort waters, a
test which can be considered analogous
to the standard residue test.
Three methods are described for the
determination of total ammoniacal
nitrogen in retort wastewaters: (1) a
modified ion selective electrode tech-
nique; (2) an optical absorption
technique; and (3) an ion chromato-
grapnic technique. The latter technique
is recommended for routine monitoring
of retort water, although the relative
advantages of each are discussed in the
report.
Total sulfur in retort gas is determined
by combusting the gas in a continuously
flowing system, whereupon the
resulting sulfur dioxide is determined by
an SO2 monitor. Individual sulfur spe-
cies in retort gas, including H2S, COS,
SO2, CS2, and CH3CH2SH, are deter-
mined by gas chromatography with
flame photometric detection.
Potential interferences due to co-
eluting hydrocarbons or other sulfur
species are examined extensively.
Quality control, pH, conductivity,
total inorganic carbon, and total
organic carbon measurements are
discussed briefly.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory, Cincinnati, OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
The full report describes methods of
chemical analysis required to adequately
test the various pollution control
technologies being proposed for the
treatment of oil shale retort gases and
wastewaters. Included in the full report
are step-by-step protocols for determin-
ing important species. Supporting
evidence and discussion permit the
analyst to adjust the procedure to the
varied sample types encountered. The
report stresses methods that are rugged
and rapid enough to be used during the
field testing of pollution control systems.
Major and Minor Ion Detection
A type of ion exchange chromato-
graphy, referred to in the literature as
suppressed ion chromatography, was
used to determine major and minor
anions in retort wastewaters. Originally,
this method indicated the presence in
retort wastewaters of very late-eluting
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compounds which, because they could
not be removed from the column in a
reasonable time, interfered with subse-
quent analyses. This problem was solved
with a column switching arrangement
that allows the late eluters to be
separated on a pre-column while the
earlier-eluting compounds are separated
on the main analytical column. The same
valve and column configuration can be
used for four different protocols: the first
protocol, referred to as the majors
protocol, determines SO-4, NO~3, S2O:3,
and SCN" in a single run using 7 mM
Na2CO3 as an eluent. The second protocol
determines the late eluters, S20:3 and
SCN using an eluent of 7 mM NaCO3 +
0.5 mg/L of SCN . The third protocol
determines earlier eluters by using a
valve switching arrangement that traps
the late eluters on a pre-column, which is
periodically flushed to waste. Peaks
observable with this procedure include
Cl , acetate, N0;2, S0rj, NO'3, PO3~4 and
SO 4, although not all have been
successfully separated when present in
the same solution. While the valving and
column configuration remain unchanged,
the analysts must be prepared to adjust
the eluent for the various types of
samples and analytes encountered. The
fourth protocol measures total sulfur by
oxidizing the various sulfur species
present to SO=4, which is then
determined by the protocol for the early
eluters.
Sulfide Detection
The determination of sulfide by
potentiometric titration with Pb(ll) was
investigated for retort wastewaters.
Thiocyanate, thiosulfate, sulfate,
chloride, carbonate, ammonia, and hy-
droxide ions, all of which are components
of retort waters, were tested as potential
interferences for sulfide concentration in
the range 1-1,000 mg/L and were shown
to be insignificant within the normal
range of interest. The titration was evalu-
ated for precision, recovery, reliability,
and ease of use, under field conditions
with actual retort waters. The titration
procedure was also compared to the
direct calibration method with the AgS
ion selective electrode to monitor the
titration and a Gran's plot end point, is the
preferred method of analysis.
Thermal evaporation, lyophilization,
and the measurement of colligative
properties were investigated as the total
solute content in retort wastewaters. Of
these, both thermal evaporation and
lyophilization were shown to be inap-
propriate. Of the various colligative
properties considered, the freezing point
depression method gave the best
measurement of total dissolved solutes:
the total solute content is measured in
units of moles/liter over the range 0.001
- 3.0 moles/liter (counting each ion
separately).
Ammoniacal Nitrogen
Detection
Three distinct methods were developed
for the analysis of ammoniacal N in retort
waters. Although the first method
employs an ammonia selective electrode,
it minimizes many of the problems
associated with that device by
maintaining the electrode in pure
standard to which small amounts of
sample are added. The second method,
ion chromatography, separates NH4+ on
an ion exchange column with detection
by electrical conductivity. The third
method involves absorption of UV
radiation by ammonia in the headspace
over a basic sample solution. All three
methods are capable of quantitating
ammoniacal N in turbid, briny, and
organic-laden wastewaters; all three
have notable secondary characteristics:
the first method requires the least
investment in equipment but is the most
labor intensive and the least precise; the
ion chromatographic method, readily
implemented with commercially
available equipment, can also measure
Na and K simultaneously; the gas
absorption method shows promise as the
basis for an on-line, unattended monitor
and is capable of distinguishing between
aqueous NH3 and NH4+. The gas
absorption method gives the most precise
measurement, but its spectral
background must be corrected to achieve
accuracy.
Sulfur Detection
A method for measuring total sulfur in
oil shale retort gas operates by converting
the various sulfur species to SO2, which
is then monitored by a commercially
available monitor. A heated tube and a
flame, respectively, were evaluated for
conversion of the various individual
sulfur species to S02. The tube was
rejected because it depended both on
temperature and on the species being
oxidized. The flame converted essentially
100% of the various sulfur species to S02,
and a full-scale device was constructed
for the measurement of total sulfur in
retort gas. The device was tested at an oil
shale retort, and measured total sulfur in
agreement within experimental error
with the sum of the individual sulfur
species.
Gas chromatography with flame
photometric detection was developed as
a method for measuring sulfur species in
retort gas. To establish the veracity of this
technique, two potential problems were
considered in detail. First, because
hydrocarbons, a major component of
retort gas, are known toquenchthefluor-
escence of the flame photometric
detector (FPD), it was necessary to deter-
mine fluorescent quenching effects in
realistic retort gas. The second potential
problem was the large number of sulfur
species which can occur in retort gas and
which must be separated from each other
if an unambiguous assignment is to be
made to each.
Fluorescent quenching effects were
measured on two types of commercially
available FPDs, a single-flame detector
and a dual-flame detector. The latter
exhibited no significant quenching
effects over the concentration ranges of
interest in retort gas. However,
quenching effects for the single flame
detector cannot be ruled out entirely.
Although hydrogen sulfide in retort gas is
usually abundant enough to minimize
quenching effects, the minor species can
be subject to quenching effects unless
precautions are taken. These precautions
include operating the detector with the
air and hydrogen flows reversed and
measuring peak height rather than peak
area. In addition, columns are selected
that minimize coelution with hydrocar-
bons. The single flame detector exhibited
both suppression and enhancement of
the fluorescent signal.
Becausfe of the large number of sulfur
species which could occur in retort gas, a
single packed column could not
unambiguously separate all possible
species; therefore, efforts were made to
locate a column which could separate the
compounds of primary interest--
hydrogen sulfide, carbonyl sulfide, sulfur
dioxide, carbon disulfide, methyl mer-
captan, and ethyl mercaptan-from each
other as well as from the later eluting
sulfur compounds. Several columns were
evaluated for their ability to achieve this
separation as well as the required
separation from hydrocarbons. Columns
were also tested for their ability to
tolerate water vapor and the other
compounds in retort gas. The best
general purpose column packing for the
determination of the sulfur compounds of
primary interest was a Carbopack B HT
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100*, although a Chromosil 310 packing
would be useful for the occasional deter-
mination of thiophenes. A protocol for the
primary sulfur species is described for the
concentration range of 5-50,000 ppmv
using a Carbopack B HT 100 column
arranged in a backflush-to-detector
configuration.
Other Pertinent Data
Although electrical conductivity, pH,
alkalinity, and total inorganic carbon are
not investigated explicitly in this study,
they are discussed briefly in the full
report. ' It is suggested that- the
measurement of pH and electrical
conductivity with the standard
conductivity cell and pH electrode, respec-
tively, has demonstrated no obvious
problems, but frequent cleaning and
calibration should be expected. It is
recommended that the alkalinity test be
discontinued as a measurement of
dissolved carbon dioxide because of
interferences due to ammonia and
organic acids. Dissolved carbon dioxide
should instead be determined by
commercially available analyzers which
are also suitable for total organic carbon
measurements. Precautions for the latter
two measurements are discussed in the
text.
'Mention of tradenames or commercial products
does not constitute endorsement or recommend-
ation for use by the U.S. Environmental Protection
Agency
John Wallace, Linda Alden, Francis S. Bonomo, John Nichols, and Elizabeth
Sexton are with Denver Research Institute, University of Denver, Denver, CO
80208.
Robert Thurnau is the EPA Project Officer (see below).
The complete report, entitled "Methods of Chemical Analysis for Oil Shale
Wastes," (Order No. PB 84-211 226; Cost: $20.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
•ft US GOVERNMENT PRINTING OFFICE, 1984 —759-015/7754
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