EPA-660/2-75-017
JUNE 1975
Environmental Protection Technology Series
Radiation Treatment of High Strength
Chlorinated Hydrocarbon Wastes
National Environmental Research Center
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
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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-
five series. These five broad categories were established to
facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in
related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY STUDIES series. This series describes research
performed to develop and demonstrate instrumentation, equipment
and methodology to repair or prevent environmental 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.
EPA REVIEW NOTICE
This report has been reviewed by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents- necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
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EPA-660/2-75-017
JULY 1975
RADIATION TREATMENT OF HIGH STRENGTH
CHLORINATED HYDROCARBON WASTES
by
T. F. Craft
R. D. Kimbrough
C. T. Brown
Engineering Experiment Station
Georgia Institute of Technology
Atlanta, Georgia 30332
EPA Project R800312
Program Element 1BB036
ROAP 21AZR, Task 009
Project Officer
Robert R. Swank, Jr.
Southeast Environmental Research Laboratory
National Environmental Research Center
College Station Road
Athens, Georgia 30601
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For sale by the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402
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ABSTRACT
The possible use of gamma radiation for the treatment of waste
effluents containing chlorinated hydrocarbons, particularly pesticides,
has been investigated. Significant destruction was obtained of repre-
sentative compounds such as pentachlorophenol, 2,4,5-trichlorophenoxy-
acetic acid, and 2,4-dichlorophenoxyacetic acid. Radiation treatment *
had little effect on polychlorlnated biphenyls "or mixtures of com-
pounds, Including actual manufacturing effluents.
It was found that the addition of a material of high atomic
weight, such as barium, increased the efficiency of radiation utiliza-
tion. No other materials were found which increased the desired
destruction. G-values were calculated for pentachlorophenol, 2,4,5-
trichlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic acid.
It is concluded from the magnitude of these values that radiation
treatment of chlorinated hydrocarbons is not economically feasible at
the present level of radiation costs.
This report was submitted in fulfillment of Grant No. R800312
by the Engineering Experiment Station of the Georgia Institute of
Technology under the partial sponsorship of the Environmental Protec-
tion Agency. Work was completed as of November 1974.
ii
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CONTENTS
Sections Page
I Conclusions 1
II Recommendations 2
III Introduction 3
IV Experimental Details 7
V Test Results 9
VI References 32
iii
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FIGURES
No. Page
1 Effect of radiation on Arochlor 1254 12
2 Gas chromatograms of Pentachlorophenol
after various radiation doses 14
3 Destruction of Pentachlorophenol by irradiation 16
4 Molecules and percent of Pentachlorophenol destroyed
by irradiation 17
5 Destruction of 2,4,5-Trichlorophenoxyacetic Acid
by irradiation 21
6 Destruction of 2,4-Dichlorophenoxyacetic Acid by
irradiation 26
7 Barium Sulfate enhancement of radiation effects 30
iv
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TABLES
No. Page
1 Summary of Arochlor 1254 Experiments 11
2 Summary of Pentachlorophenol Experiments 13
3 Summary of 2,4,5-Trichlorophenoxyacetic
Acid Experiments 20
4 Irradiation of 0.1% 2,4,5-T in 1% Sodium Carbonate
(cobalt-60 irradiator at 5.5 megarads/hour) 23
5 Summary of 2,4-Dichlorophenoxyacetic Acid Experiments 24
6 Calculated G-Values 28
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ACKNOWLEDGEMENTS
This project was funded by the United States Environmental
Protection Agency, Grant Number R800312 to the Georgia Tech Research
Institute, Georgia Institute of Technology, Atlanta, Georgia.
The support of this work by the Environmental Projection Agency
is greatly appreciated. The contribution of Project Officer Dr. Robert
R. Swank, Jr. (Southeast Environmental Research Laboratory) to the
project involved both scientific and managerial matters. His genuine
interest and assistance are acknowledged with sincere thanks.
vi
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SECTION I
CONCLUSIONS
The following conclusions can be drawn concerning the compounds
and mixtures on which experimental work was performed:
1. Gamma radiation from cesium-137 and cobalt-60 destroys
individual compounds with varying degrees of efficiency in
aqueous solutions.
2. Little or no radiation destruction occurs when the compound
is dispersed on an inert substrate.
3. Destruction can occur when the compound is dissolved in a
non-aqueous solvent such as hexane or benzene.
4. The presence of extraneous material is most likely to
diminish the destruction of the compound in question.
5. Destruction of mixtures is likely to be much less efficient
than destruction of single compounds.
6. The utilization of radiation in the destruction of these
materials is not very efficient as shown by the calculated
G-values.
7. Radiation treatment of wastes containing chlorinated hydro-
carbons such as those resulting from manufacturing processes
is unlikely to be economically feasible at present levels of
radiation costs unless a very effective means of radiation
utilization enhancement can be found.
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SECTION II
RECOMMENDATIONS
Ionizing radiation is a very effective agent for treating organic
waste constituents that are resistant to biological degradation. The
efficiency, however, depends on the radiation sensitivity of the
pollutant materials and their concentration in the waste stream.
Under present economic conditions, radiation treatment is somewhat
more expensive than the ordinary biological processes. Nevertheless,
it appears very useful for treatment of wastes containing obnoxious
bio-resistant components, particularly when the pollutant concentra-
tion of these refractories is not too low.
There are two major factors that have hindered the adoption of
radiation waste treatment processes. The first is the insensitivity
to radiation of some compounds. Radiation ruptures chemical bonds,
but this is of no benefit if the fragments recombine in their original
configuration. It is recommended that a search be carried out for
effective, low-cost scavenging agents which will damp out the recom-
bination reaction.
A second factor is the low concentration at which refractory
pollutants occur in the usual industrial waste stream. Much energy is
expended on the irradiation of large volumes of water in order to
degrade the small amount of obnoxious matter present. It is therefore
recommended that means be sought to produce more concentrated waste-
water streams through changes in waste-generating operations, or
through procedures for concentrating these refractory pollutants
produced in normally dilute solutions or suspensions.
It is specifically recommended that tests be conducted of waste
treatment systems that provide for retention of the refractory
material in a radiation zone while allowing the aqueous phase to pass
through. For example, refractory pollutants might be collected on
activated carbon or metal oxide surfaces positioned within a suitable
radiation field. The efficiency of radiation utilization would be
increased, as the target material would receive larger exposure times
and energy expended on the water would be minimized.
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SECTION III
INTRODUCTION
Within recent years environmentalists have become aware of wide-
spread contamination of the environment by inorganic and persistent
organic compounds. The general cause for this is attributable to
urbanization, industrialization, and highly developed agricultural
practices. More specifically, inappropriate disposal procedures and
accidental releases account for a large portion of the present
contaminant levels. Agricultural activities also contribute signifi-
cantly, mainly persistent pesticides. Pesticides must be dispersed
over large areas to be useful, and their subsequent control becomes
impossible.
Most persistent pesticides are organochlorine compounds and for
the purposes of this discussion may be grouped with a large number of
herbicides, plasticizers, flame retardants, and other chlorinated
hydrocarbons that find their way into the environment. The problem
cannot be solved by prohibiting the manufacture and use of these
compounds, as many are not particularly harmful and they are all very
useful (if indeed not indispensable) to our present level of tech-
nology. Chlorinated organic compounds, for instance, which are used
as pesticides have been exceedingly beneficial by controlling the
vectors of serious human disease which have claimed millions of lives
and by greatly increasing the yields of many crops. The need for food
will increase as the population grows, and thus it appears likely that
the need for pesticides will also increase.
The problem therefore becomes one of control in the production,
use, and disposal of potentially harmful compounds. It may eventually
prove necessary to ban some materials, but careful use and disposal
techniques would greatly reduce the present rate of environmental
contamination. This would reduce human contact with chlorinated
hydrocarbons which is at present unavoidably high because chlorinated
hydrocarbons are resistant to degradation and they accumulate in the
food chain.
Chlorinated hydrocarbons are, in general, soluble in fat and
insoluble in water, which causes them to accumulate in the lipid
tissue of organisms with which they come in contact; thus, their
concentration increases to many times that in the water. This effect
is repeated as the material moves up the food chain, producing
damaging and/or lethal concentrations in higher organisms. These
insidious properties of chlorinated hydrocarbons are shared by many
of the starting materials and reaction by-products (they themselves
being chlorinated hydrocarbons) involved in their manufacture.
-------
Because of the biomagnification phenomenon, dilution of this type of
waste as a means of disposal is not acceptable, and other disposal
procedures are needed. Pollution of both fresh and salt water by
chlorinated hydrocarbons, including persistent pesticides and
herbicides, polychlorinated biphenyls (PCB's), and polychlorinated
naphthalenes, originates in two ways: (1) as residues in trace
amounts from the use of these materials in agriculture and industry
and (2) in much higher concentration as waste effluents from chemical
companies manufacturing these compounds. It does not appear feasible
to process all the water in a large river to remove those chlorinated
hydrocarbon residues present in concentrations of a few parts per
million or less; however, it may be feasible to process the highly
concentrated effluent of a chemical company manufacturing chlorinated
hydrocarbon products.
In many chemical processes, the initial result of a reaction is
a complex mixture of compounds which include, in addition to the
desired end product, such things as unreacted starting material,
products of competing or side reactions (of both the initial reactants
and their impurities), condensation products, and decomposition
products. Various purification processes such as crystallization,
filtration, distillation, and extraction may be utilized to separate
out the desired product, leaving all the remainder for disposal.
From the waste treatment view, it would be highly desirable to
recycle and/or recover some usable by-product from the residual
mixture, even if the economics were not particularly attractive. In
the usual case, however, it is cheaper simply to discard the unwanted
residues.
Conventional methods of waste treatment such as sedimentation and
bacteriological degradation have little if any effect on these wastes.
Even when a resistant compound disappears from the water, it may only
be adsorbed but not metabolized and therefore may reappear in the food
chain often in a more concentrated form. Sometimes when compounds
are altered, the primary degradation product is as stable and as toxic
as the initial compound. Adsorption on activated carbon may be
possible, but this does not completely solve the problem because the
saturated adsorbent remains for disposal.
Bacteria can be acclimated to decompose many organic compounds
including some that are ordinarily quite resistant. With highly
resistant compounds, acclimation is very difficult, and for many
compounds has so far proven impossible. Even when acclimation is
possible, deacclimation occurs rapidly if an alternate source of
carbon becomes available. No suitable cultures have yet been reported
for chlorinated hydrocarbons* some of which are very toxic to bacteria
and may even be used as disinfectants. A need therefore exists for
an effective, economic procedure for the destruction of unwanted
-------
chlorinated hydrocarbons or for their degradation to a form that is
amenable to treatment by conventional procedures.
Ionizing radiation profoundly affects organic molecules through
rupture of chemical bonds, and it is possible that radiation could
effectively degrade biorefractory compounds. Radiolytic decomposition
may proceed via direct interation between a photon and the organic
molecule, or the effect may be brought about indirectly by radicals
or ions created by interaction of photons with the solvent. It seems
likely that both actually occur, although the direct action is perhaps
less important in aqueous solution where radiation is known to produce
a number of active ions and free radicals including hydrogen, hydroxyl,
peroxyl, plus a large number of more complex entities.
It has been observed in this laboratory that the effects of
radiation may be increased by the presence of an oxidant or other
chemical agent. Experiments have demonstrated that dye solutions can
be decolorized by a combined treatment of gamma radiation plus
hypochlorite. The combination is much more effective than the two
applied individually. Megarad radiation doses alone are required to
achieve the same result that can be obtained with 25-50 kilorads of
gamma radiation in the presence of hypochlorite.
There was no a^ priori reason to believe that simlar results could
not be achieved with chlorinated hydrocarbons, or, for that matter,
any other type of organic compound, although operating conditions
would not necessarily be the same. Radiolytic reactions involving
chlorinated hydrocarbons in water include oxidation, hydroxylation,
and dechlorination, all of which appear beneficial. These and other
degradative reactions are greatly increased in the presence of a
chemical oxidant. In general, each of these reactions would be
expected to result in increased susceptibility to further chemical or
biological degradation, decreased toxicity, and increased solubility
in water and, therefore, less accumulation in the food chain.
Radiolytic condensation and polymerization reactions would also be
encountered. The products of these reactions would be less soluble
and hence more susceptible to removal by sedimentation.
The ultimate usefulness of any treatment process depends largely
on economic factors. Neither radiation nor chemical treatment alone
seem likely to be economically attractive under most circumstances.
However, costs may be greatly reduced by a suitable combination
treatment, particularly in the presence of an efficient catalyst.
In the work here described, the effect of ionizing radiation,
alone and in combination with chemical agents, on chlorinated hydro-
carbons and mixtures of chlorinated hydrocarbons typical of those in
waste effluents from chemical companies making these compounds was
studied. Included in this program was a study of the rate of
-------
destruction of various chlorinated compounds as a function of their
concentration in the effluent, a study of the dose rate dependence of
the destruction, a study of the effects of various chemical and
physical agents on the rate of destruction of the chlorinated
compounds, and finally, a study of the radiation products produced in
these various experiments.
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SECTION IV
EXPERIMENTAL DETAILS
RADIATION SOURCES
Two irradiation facilities were employed in the experimental work
and preliminary plans were made to provide a capability for performing
dynamic flow tests.
Cesium-137 Source
A 12,000 curie cesium-137 source is available at Georgia Tech
for static irradiation tests. This source is housed in a 20-foot deep,
sub-surface well and is arranged to provide uniform irradiation in an
annular, coaxial configuration to as many as 12 vial specimens at a
time. The dose rate in aqueous samples in the standard geometry is
fixed at 1.0 Mrad per hour and total doses are varied by varying the
exposure time. Sample insertion takes less than one second from a
negligible field region.
Cobalt-60 Source
To provide greater variability in total dose and dose rate, an
irradiation arrangement was devised, using encapsulated cobalt-60
strips totaling approximately 100,000 curies. The cobalt-60 was
stored in a stainless steel bucket 15 feet below the surface of the
storage pool at the Frank H. Neely Nuclear Research Center at
Georgia Tech. Samples were irradiated in an aluminum pipe, the bottom
of which was fastened inside a circular aluminum container. The
radiation field inside the pipe was then governed by the number of
individual cobalt-60 strips placed in the container. Thermolumi-
nescent dosimeters were used to calibrate the field strength.
PROCEDURES
Maximum effects are obtained when the compound under study is in
solution, and suitable solvent systems were sought in all cases.
Hydrocarbons, alcohols, and base solutions were utilized at different
times. Some samples which could not be easily solubilized were
deposited on glass wool and Immersed in water. The results were not
significantly different from those obtained by irradiating non-
dispersed solid covered with water.
A portion of the prepared sample was then irradiated by inserting
it into the cesium^l37 or cobalt-60 irradiator for the selected
period of time. Following the irradiation period, the chlorinated
-------
hydrocarbon was extracted from solution and its gas chromatogram was
obtained. This was compared with the gas chromatogram obtained from
the remaining (non-irradiated) portion of the sample.
The gas chromatograph used was a Microtek Model 220 fitted with a
flame ionization detector and an Ni-63 electron capture detector. A
6-foot long, 1/4 inch diameter stainless stell column containing 5%
SE-30 on Chromport, 80/90 mesh was used with the flame ionization
detector. A glass column of the same dimensions containing 3% OV-1 on
Chromosorb W, 80/100 mesh was used with the electron capture detector.
The carrier gas utilized was a "prepurified" grade marketed by
Matheson Gas Products. Optimum column temperatures for the various
materials studied were in the range of 140-210*590. Injected samples
ranged in size from two to eight microliters.
Careful attention was given to the extraction technique in order
to assure quantitative recovery of the chlorinated hydrocarbon. In
some cases it was found necessary to methylate the compound prior
to determination of the gas chromatogram. This was accomplished using
diazomethane to convert the hydroxy to a methoxy form and was applied
to pentachlorophenol, 2,4-dichlorophenoxyacetic acid and 2,4,5-
trichlorophenoxyacetic acid. Any phenol resulting from cleavage of
an oxygen-carbon bond during irradiation of the acids would have been
readily methylated while the acid was undergoing esterification.
Non-methylated samples of these materials were found to pass through
the gas chromatograph column very slowly and yield strong "tailing" of
the peak. Such data were extremely difficult to analyze.
The quantity of the compound of interest present in any sample
was determined by measuring the area under its main peak on the gas
chromatograph. Area measurements were made with a polar planimeter,
and were reproducible within one percent.
Other procedures were followed as the need arose. Some gross
carbon content determinations were made using a Beckman Model 915
Total Organic Carbon Analyzer according to standard operating
procedures. A Beckman Model DBG-T Spectrophotometer was used to
obtain ultraviolet and visible spectra.
8
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SECTION V
TEST RESULTS
POLYCHLORINATED BIPHENYLS
Arochlor 1254, a mixture of polychlorinated biphenyls containing
54% chlorine by weight was used to represent this type of compound.
Typical PCB's are water soluble only to the extent of a few milli-
grams per liter, so for practical laboratory studies, other solvents
or means of dispersion were required. Arochlor 1254 is quite soluble
in ethanol and benzene, and it was found that slightly more than
400 mg/1 would dissolve in 15% ethanol-85% water mixture. This solvent
system was used for some studies, although commercial waste effluent
streams would not likely contain any auxiliary solvent. To eliminate
any effects caused by the alcohol, Arochlor 1254 was also deposited
on glass wool and on fine copper turnings for irradiation. This was
accomplished by placing the glass wool or copper turnings in an
alcohol solution of the Arochlor and evaporating the solvent under
reduced pressure. The container was then filled with distilled water.
Air was bubbled through the liquid during most irradiations, and
attempts were made to maintain an emulsion without any solubilizing or
suspending agent. The bubbling action was not satisfactory for this
purpose, and it was found that the Arochlor 1254 became rapidly
attached to the walls of the container and to the air inlet.
Benzene was used for the extraction of Arochlor 1254 from the
various solvent and dispersion systems, and gas chromatograms were
obtained from the benzene solutions. Recovery by benzene extraction
was essentially quantitative as shown by the results obtained with a
400 mg/1 solution of Arochlor 1254 in a 15% ethanol-85% water mixture:
Extraction Total % Recovered
1 83.9
2 92.3
3 98.6
4 99.9
Extraction from glass wool was slightly easier:
Extraction Total % Recovered
1 85.0
2 98.2
3 100.1
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The experimental data concerning Arochlor 1254 is summarized in
Table 1. Some of the preliminary work showed destructions of more
than 20%, but these results were subject to a rather large experimen-
tal error, and are therefore of doubtful validity. The major source
of error lies in the analysis of the gas chromatograms, where the
position of the base line cannot be determined unequivocally, and at
times must be assumed rather arbitrarily. The problem in essence is
that of measuring small differences between rather large quantities.
Overlapping of solvent tailings also presented difficulties. Two
methods of determining the area under peaks of the gas chromatograms
were evaluated. Some peaks were scissored from the recorder chart and
weighed, but this proved less satisfactory than measurement of area
with a polar planimeter. The planimeter technique, reproducible to
within about 1%, was therefore utilized during the remainder of the
work.
One experiment resulted in the rather interesting situation
illustrated by Figure 1. The total destruction of Arochlor 1254 was
essentially zero, but there was apparently a change in composition
during irradiation as indicated by an increase in the peaks shown by
the dotted line. This suggests an increase in two of the more
volatile, lower molecular weight components of the mixture, and may
have been caused by loss of chlorine from one of the heavier
components.
The variability of results obtained even under supposedly con-
stant conditions makes interpretation of the data difficult, particu-
larly when it is noted that a 6% "destruction" was noted when air was
bubbled through the solution for two hours without irradiation. It
is concluded however, that some Arochlor 1254 was destroyed under the
experimental conditions employed, and the use of copper turnings as
a support medium had little, if any, effect on the results obtained.
PENTACHLOROPHENOL
The gas chromatograms obtained from pentachlorophenol are much
simpler than those obtained from the mixture of PCB's identified as
Arochlor 1254. There was a considerable initial problem with tailing
of the pentachlorophenol, and all samples were subsequently methylated
before injection into the gas chromatograph. Diazomethane was the
methylating agent used, and was prepared from N-methyl-N-nitroso-p-
toluenesulfonamide. In each methylation, approximately 2 1/2 - 3
times the stoichiometric amount of diazomethane was added. Because of
the hazardous and not entirely predictable behavior of diazomethane,
all methylations were carried out behind the safety glass of a fume
hood, and no problems were encountered.
The results of all the pentachlorophenol experiments are
summarized in Table 2. One experiment involving deposition on glass
10
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Table 1. SUMMARY OF AROCHLOR 1254 EXPERIMENTS
Concentration
Mg/1
400
400
400
420
440
420
400
410
27 mg on
support
it
ti
it
it
it
ii
it
Solvent or
support
Ethanol
Benzene
15% Ethanol
15% Ethanol
15% Ethanol
15% Ethanol
15% Ethanol
15% Ethanol
Glass wool
Cu turnings
Cu turnings
Cu turnings
Cu turnings
Cu turnings
Cu turnings
Cu turnings
Radiation
megarads
1
1
2
19.5
20.5
20.6
20.6
20.75
16
0.0
0.5
0.5
4.0
4.0
15.0
39.0
Arochlor 1254
% destroyed
0
0
9
21
0
4
23
9
<3
6
1
5
4
11
10
11
Comments
No air
bubbled
No air
bubbled
See text
See
figure 1
See text
Air
bubbled
11
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GAS CHROMATOGRAM OF IRRADIATED
MATERIAL DIFFERED FROM ORIGINAL
ONLY BY PEAKS SHOWN
AS DOTTED LINES
Figure 1. Effect of radiation on Arochlor 1254.
12
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Table 2. SUMMARY OF PENTACHLOROPHENOL EXPERIMENTS
Concentration
mg/1
10 mg + water
10 mg + water
900
900
900
900
900
900
2860
2860
2860
2860
2860
2860
2860
28,600
28,600
28,600
400
900
900
6000
15,000
Air
bubbling3
Yes
No
Yes
1 b
3 b
Rapid
5-10 b
Yes
10 b
10 b
Rapid
10 b
No
10 b
10 b
Rapid
No
No
No
No
No
No
No
Radiation
megarads
18
18
0
0
0
0
1
17.5
0
0.25
0.25
1.0
1.0
4.0
17.5
1
8
16
1
0.5
1.6
1.0
1.0
% PGP
destroyed
>95
3.7
26
0
' 10
15
76.1
95.6
0
12.9
12.1
41.5
41.7
90.2
97.3
8.6
47.0
68.6
95.7
47.6
98.0
21.0
15.2
Comments
On glass wool
On glass wool
19 hrs. air
25.5 hrs. air
26 hrs. air
9.5 hrs. air
17 hrs. air
Copper foil
present
Bubbles per second = b
13
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NON-IRRADIATED
SAMPLE
AFTER 0.25
MEGARAD
AFTER 1.0
MEGARAD
AFTER 4.0
MEGARADS
Figure 2. Gas chromatograms of Pentachlorophenol
after various radiation doses.
14
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wool was performed, and destruction greater than 95% was observed. It
is believed, however, that most of this "destruction" is probably due
to volatilization of the pentachlorophenol during the long aeration
period. A repetition of the experiment without air bubbling showed
only a very small reduction of pentachlorophenol. All other experi-
ments were performed on solutions obtained by dissolving pentachloro-
phenol in 1% sodium carbonate. Benzene was the extraction solvent and
was used directly to recover the sample deposited on glass wool. The
aqueous solutions were acidified prior to benzene extraction.
It is clear that pentachlorophenol is destroyed by radiation
under the various conditions utilized. Figure 2 shows a series of gas
chromatograms of samples following various periods of irradiation of
a 2860 mg/1 solution. The strong pentachlorophenol peak diminished
as the radiation dose was increased, and at the same time other peaks
corresponding to more volatile species grew. The effect of irradia-
tion on this particular concentration of pentachlorophenol can be
summarized as follows:
Dose delivered PGP remaining
Megarads Per cent
0.0 100
0.25 87.1
1.0 58.5
4.0 9.8
These data, along with similar data for other concentrations have been
plotted and appear as Figure 3. It therefore appears that destruction
is proportional to the period of irradiation when the sample is
exposed at a constant dose rate.
A determination of pentachlorophenol destruction as a function of
concentration was made through, a series of 1 megarad irradiations.
Various concentrations from 0.04% to 2.86% were tested, and the resid-
ual pentachlorophenol determined. The number of molecules destroyed
was calculated and the information plotted as Figure 4. These data
indicate that the number of pentachlorophenol molecules destroyed by
a given dose increases with concentration up to approximately three
percent, but the fraction of the material destroyed drops quite
rapidly with increased concentration.
When pentachlorophenol was dissolved in 1% sodium carbonate, the
resulting solution typically had a pH of 10-11. It was observed that
in all cases the pH was reduced by irradiation to about 8-9 for short
irradiations and to 4-4.5 for a 24 hour irradiation. Appreciable
chloride ion also appeared in the irradiated mixtures, indicating
that, in effect, hydrochloric acid had been formed through removal of
15
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PENTACHLOROPHENOL REMAINING
AFTER IRRADIATION AT
1 MEGARAD PER HOUR
4 8 12
HOURS OF IRRADIATION
16
20
Figure 3. Destruction of Pentachlorophenol by irradiation.
16
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CONCENTRATION DEPENDENCE OF
PENTACHLOROPHENOL DESTROYED
BY 1 MEGARAD DOSE
D MOLECULES
O PERCENT
m
a
U
m
a
x
to
1.0 1.5 2.0
PERCENT PENTACHLOROPHENOL IN SOLUTION
Figure 4. Molecules and percent of Pentachlorophenol destroyed by irradiation.
-------
chlorine from the organic molecule. This is consistent with similar
observations recorded in the literature.
A precipitate was present in the mixture subjected to 24 hours of
irradiation, and when nitric acid was added to lower the pH from 4
to 1, additional solid was formed. This solid material was found to
be insoluble in water and in hexane, but slightly soluble in
chloroform and benzene. It melted in the 150-160° range. It was
subjected to elemental analysis with these results: carbon 31.6%,
hydrogen 0.83%, chlorine 51.3%, oxygen (by difference) 14.1%, inorganic
residue 2.2%. A 1.15 gram sample of pentachlorophenol yielded 0.78
grams of precipitate. A gravimetric determination of chloride in the
supernatant showed the presence of 0.3 gram. The total accounts
fairly well for all the starting material. A Rast determination showed
the molecular weight of the precipitate to be 650-750.
The infrared spectra indicated hydroxyl and aromatic groups. The
color of the dry solid was tan-gray; however, the material in solution
was dark brown. Chromatography of a chloroform solution on neutral
alumina showed a slight color in the eluent, but very little material.
Most of the material stayed at the top of the alumina column and did
not move.
The above properties indicate that the precipitated solid is a
low molecular weight "polymer" of probable formula [CfiCl_(OH)„] which
is in agreement with similar results recorded in the literature^. It
was reported that radiolysis of a six carbon aromatic compound gave
"a C-- fraction, a C_R fraction, and higher molecular weight material.
The average molecular weight of the mixture increased with the
increasing absorbed dose." Perhaps the property of the irradiation
product that is most significant in this work is the greatly reduced
solubility of the product compared to the starting material, penta-
chlorophenol.
2,4,5-TRICHLOROPHENOXYACETIC ACID
This material, commonly known as 2,4,5-T, is widely used in the
ester or salt form as a herbicide for species of plants that are
resistant to 2,4-dichlorophenoxyacetic acid derivatives (2,4-D).
2,4,5-T falls in the class of chlorinated compounds that persist in
the environment, and its dispersion should be subjected to the same
scrutiny accorded other similar materials. However, it is frequently
accompanied by an accidental impurity, 2,3,7,8-tetrachlorodibenzo-p-
dioxin that is formed during manufacture. This by-product, commonly
known as TCDD or simply dioxin, is significant because of its
persistence in the environment and its exceptionally toxic properties.
Experiments on the destructibn of dioxin were performed, and are
discussed below.
18
-------
All of the experiments involving 2,4,5-T were carried out with
the organic material dissolved in a 1% sodium carbonate solution. Gas
chromatograms were obtained from benzene extracts of acidified samples.
Experiments with other compounds led to the conclusion that the con-
tinuous bubbling of air through a sample during irradiation was of
little or no effect. Consequently no air injection was made during
the studies of 2,4,5-T.
Table 3 summarizes the observed effects of radiation on 2,4,5-T
solutions of several different concentrations. A number of replicated
runs are included and illustrate the degree of reproducibility of the
results. It was noted that the pH of the samples was lowered by
irradiation in the same manner as pentachlorophenol solutions. These
experiments show that 2,4,5-T can be destroyed quite effectively by
moderate doses of gamma rays from cesium-137. The dose required to
destroy a given percentage of a sample was found to depend strongly
on the initial concentration of the material as shown in Figure 5.
Visible and ultraviolet spectra were obtained from a 0.1% 2,4,5-T
solution before and after irradiation for 55 minutes (0.92 megarad).
A small peak was noted at 281 nm prior to irradiation, but was absent
in the spectrum of the irradiated sample. Gas chromatographic
analysis of the same sample indicated destruction of 81.5% of the
2,4,5-T present. Spectra of other materials were also obtained, but
the information available from gas chromatograms was considered more
reliable and was therefore utilized.
Possible temperature effects were evaluated in an experiment
where destruction at room temperature was compared with destruction
obtained at 90-95° C. A sample of 0.1% 2,4,5-T was heated by wrapping
the irradiation vessel with a heating tape that could be lowered into
the cesium-137 source. The temperature ranged during irradiation from
90° to 95° C as measured with a thermocouple. The heated sample
showed a destruction of 67.9% as compared to 69.1% for an unheated
control. These values are well within the limits of experimental
error, and it was concluded that the increased temperature had no
effect on the results obtained.
The effect of the solvent was clearly shown in a series of 1
megarad irradiations. Solutions of 2,4,5-T (0.1%) in diethyl ether,
benzene, and hexane revealed no destruction. This is in contradis-
tinction to the 84% destruction obtained under the same conditions
when the 2,4,5-T is dissolved in 1% sodium carbonate.
In addition to irradiations carried out in the cesium-137
irradiator at 1 megarad per hour, other tests were made in a cobalt-
60 facility where the dose rate was approximately 5.5 megarads per
hour.- The higher dose rate is quite effective in the destruction of
19
-------
Table 3. SUMMARY OF 2,4,5-TRICHLOROPHENOXYACETIC ACID EXPERIMENTS
Concentration
per cent
0.02
0.02
0.02
0.02
0.02
0.1
0.1
0.1
0.1
0.5
0.5
0.5
0.5
0.5
Radiation
megarads
0
0.25
0.53
1.0
4.0
0
0.25
1.0
4.0
0
0.25
0.5
1.0
4.1
Area under
6. C. peak
(in2)
1.43
1.33
1.34
1.22
1.32
0.40
0.36
0.07
0.05
.0
~o
2.07
1.96
2.01
1.38
1.45
1.35
0.30
0.32
0.34
.0
.0
~0
2.35
2.11
1.98
1.57
0.26
Average
area (in^)
1.33
0.38
0.06
..0
~o
2.01
1.39
0.32
.0
% 2,4,5-T
destroyed
0
31.4
95.5
,100
,100
0
30.9
84.1
.100
0
10.2
15.7
33.2
88.9
20
-------
100
50
<
a
oc
oc
<
C9
LU
OC
20
10
T
2,4,5-T REMAINING AFTER
IRRADIATION AT 1 MEGARAD
PER HOUR
T
I
I
I
1 2 3
HOURS OF IRRADIATION
Figure 5. Destruction of 2,4,5-Trichlorophenoxyacetic Acid by irradiation.
21
-------
2,4,5-T, but is less efficient. The cobalt-60 experiments are
summarized in Table 4.
2,4 DICHLOROPHENOXYACETIC ACID
The irradiation studies of 2,4-D produced results similar to
those for 2,4,5-T; i.e., dilute aqueous solutions of 2,4-D can be
destroyed quite effectively by moderate doses of gamma rays from
cesium-137. As was found with 2,4,5-T and pentachlorophenol the dose
required to destroy a given percentage of a sample depends strongly
on the concentration of the material. Aqueous solutions of 0.02 to
2.5 per cent 2,4-D in one percent sodium carbonate were irradiated.
The doses ranged from 0.25 to 16.8 megarads. The results of these
studies are given in Table 5 and plotted in Figure 6.
The product formed by longer irradiation of 2,4-D was found to be
a low molecular weight polymer. The material resisted all attempts of
crystallization, gave an elementary analysis indicating appreciable
dechlorination, and gave an average molecule weight of 635, as
determined by the Rast method. These results indicate something
between a trimer and a tetramer which had lost some chlorine.
MIXTURES OF COMPOUNDS
Samples of a waste stream resulting from the manufacture of
toxaphene were obtained and examined. The manufacturer reported the
toxaphene level in this effluent to be very low, and our laboratory
results concurred. The gas chromatograms of toxaphene are complex,
and at the parts per billion range are difficult to interpret quanti-
tatively. When effluent samples were irradiated at doses up to one
megarad, little or no effect was discemable.
Herbicide orange, a mixture of esters of 2,4-D and 2,4,5-T was
also the subject of investigation. This product contains a large
number of different impurities and by-products, the most significant
of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly called
dioxin. There is at present a large supply of the herbicide mixture
in existence that could be used in many locations if the very toxic
dioxin could be removed or destroyed.
Dioxin is present in the herbicide mixture at levels up to about
30 parts per million, and is difficult to detect in the presence of
massive amounts of other organic compounds. Column chromatography
offers one technique for the separation of dioxin from complex
mixtures^. The success of this procedure appears to depend strongly
on the experience of the analyst, but was found to give acceptable
results after some preliminary experimentation. It was found that
within experimental uncertainties, no change in the dioxin content of
22
-------
Table 4. IRRADIATION OF 0.1% 2,4,5-T IN 1% SODIUM CARBONATE
(cobalt-60 irradiator at 5.5 megarads/hour)
Time (Minutes)
0
5
10
•
15
30
60
Area (in2)
1.86
1.90
1.14
1.15
0.64
0.66
-
-
_o
,.0
Average (in )
1.88
1.15
0.65
-
-
.0
% Destroyed
0
38.8
63.5
82.3
..100
aoo
23
-------
Table 5. SUMMARY OF 2,4-DICHLOROPHENOXYACETIC ACID EXPERIMENTS
Concentration
per cent
.02
.02
.02
.02
.02
0.1
0.1
0.1
0.1
0.1
Radiation dose
megarads
0
0.25
0.5
1.0
2.0
0
0.25
0.5
1.0
2.0
Area tinder
G.C.peak
(in2)
0.66
0.65
0.70
0.38
0.41
0.38
0.10
0.10
0.11
0.005
0.0075
0.005
.0
0.98
1.02
1.02
0.69
0.79
0.72
0.54
0.57
0.56
0.26
0.27
0.29
0.05
0.03
0.04
Average area
in2
0.67
0.39
0.103
0.0058
.0
1.01
0.73
0.56
0.27
0.04
% 2,4, -D
destroyed
0
41.7
84.6
99.1
aoo
0
27.7
44.5
73.3
96.04
24
-------
Table 5 (continued). SUMMARY OF 2,4-DICHLOROPHENOXYACETIC
ACID EXPERIMENTS
Concentration
per cent
0.5
0.5
0.5
0.5
0.5
0.5
2.5
2.5
2.5
2.5
2.5
2.5
Radiation dose
megarads
0
0.25
0.5
1.0
4.0
16.8
0
0.53
1.0
2.0
4.2
8.0
V
Area under
G.C. peak
(in2)
1.06
0.90
0.82
0.94
0.77
0.80
0.84
0.74
0.85
0.87
0.83
0.77
0.63
0.60
0.21
0.20
»0
1.33
1.36
1.25
1.30
1.21
1.31
1.08
1.16
0.92
0.94
0.70
0.70
Average area
in2
0.93
0.80
0.82
0.67
0.205
~0
1.34
1.28
1.26
1.12
0.93
0.70
% 2,4,-D
destroyed
0
14.0
9.0
25.5
77.2
.100
0
4.5
6.0
15.4
30.6
47.8
25
-------
100
50 —
20
ec
LU
II
UJ
u
QC R
in w
2,4-D REMAINING AFTER
IRRADIATION AT 1 MEGARAD
PER HOUR
I
468
HOURS OF IRRADIATION
10
12
Figure 6. Destruction of .2,4-Dichlorophenoxyacetic Acid by irradiation.
26
-------
herbicide orange was brought about by radiation doses up to one
megarad.
Other means for the destruction of dioxin were attempted.
Solutions of dioxin in hexane, benzene, and alcohol were refluxed in
the presence of stainless steel for periods up to 48 hours. The
resulting gas chromatograms gave well-defined peaks, but indicated no
change in dioxin concentration due to the refluxing. The experiments
were repeated with the refluxing carried out under ultraviolet light.
Again the gas chromatograms were very good, but the ultraviolet
radiation had no detectable effect.
G-VALUES
In radiation chemistry studies, it is important to measure the
efficiency of radiation utilization. When dealing with liquids or
solutions, the term G-value is frequently used and denotes the number
of molecules changed for each 100 electron volts of energy absorbed.
Thus G(X) refers to the number of molecules of product X formed on
irradiation per 100 eV of energy absorbed and G(-Y) refers in the same
way to the loss of material Y that is destroyed on irradiation.
A number of G-values were calculated for some of the compounds
studied, and they indicate the relative efficiency (and therefore
cost) of radiation destruction of the compound in question. For this
work the G-value is defined as:
Number of Chlorinated Molecules Destroyed
Energy Absorbed by Sample (in units of 100 eV)
The calculated values are given in Table 6. As might be
expected, the G-value for each compound depends on the concentration.
In the more concentrated solutions, the target density is greater,
and more interactions result. However, the order of magnitude of
these values is too low to offer much hope for economic feasibility at
the present cost levels of radiation processes.
ENHANCEMENT OF RADIATION UTILIZATION
Two approaches were evaluated in attempts to increase the
efficiency of the gamma irradiations. The first method involved the
use of a material of high atomic number to act as a secondary irrad-
iator to increase the dose delivered to an aqueous solution. The
objective was to increase the number of gamma ray interactions
occurring in the sample and, in so doing, increase the number of
energetic electrons depositing energy in the aqueous solution. An
increase in the number of gamma ray interactions should result when
a sample is loaded with a high Z element such as barium. If the
barium compound is finely divided and maintained in dispersion, a
27
-------
Table 6. CALCULATED G-VALUES
Compound
Pentachlorophenol
it
H
2,4, 5-Trichlorophenoxyacetic acid
it
ii
2 , 4-Dichlorophenoxyacet ic acid
it
H
H
Concentration
(percent)
•
0.09
0.286
2.86
0.02
0.10
0.50
0.02
0.10
0.50
2.50
G-Value
2.49
5.35
8.92
3.3
5.1
7.4
2.1
4.8
5.6
9.0
28
-------
significant fraction of the electrons released in the barium
compound should find their way into the aqueous solution where much
of their energy might be deposited. The result would be an enhance-
ment of the dose delivered to the aqueous sample.
A series of experiments was performed in which varying amounts
of powdered barium sulfate were added to 20 ml portions of 0.1%
2,4,5-T in 1% sodium carbonate solution. Each sample was stirred
during irradiation to maintain a uniform suspension of the barium
sulfate. All samples were irradiated for 0.4 hr (at 1 megarad/hr).
The presence of barium resulted in increased destruction in all cases.
However, there is seemingly a saturation effect, as additions beyond
40 grams did not increase the destruction. The results of these
experiments are plotted in Figure 7.
A second approach to enhancement of radiation efficiency
involved evaluation of a number of potential catalysts. It has been
reported^ that lanthanum phosphate catalyzes the conversion of
aromatic chloro compounds to phenols at high temperatures (400° C).
Attempts to repeat this work resulted in some dechlorination, but the
percent conversion was quite low. Nevertheless, lanathanum phosphate
was used in a series of experiments involving irradiation at ambient
temperatures. A 0.1% suspension in water containing 0.5% finely
divided lanthanum phosphate was irradiated while being stirred.
Systems of Arochlor 1254 in water and 2,4,5-T in base were also
irradiated under similar conditions. The results of these experiments
indicate that lanthanum phosphate plays no significant role in the
destruction of these chlorinated hydrocarbons.
The catalytic effects of ferric sulfate, sodium nitrate, sodium
nitrite and sodium hypochlorite on dilute solutions and suspensions
of various chlorinated hydrocarbons have been studied. One-tenth
percent solutions or suspensions of DDT in water and 2,4,5-T in base
were irradiated while in the presence of each of the above potential
catalysts. No significant destruction of DDT occurred for doses to
one megarad. The effect of these additives on the radiation
destruction of 2,4,5-T is shown below for a dose of one megarad. For
purposes of comparison the percent destruction is also shown for the
case of no additive.
In each case 0.5 percent of the potential catalyst was added to
the solution.
Additive Percent 2,4,5-T Destroyed
No additive 84.1
Sodium Nitrate 32.6
Sodium Nitrite 10.0
Sodium Hypochlorite 67.2
Ferric Sulfate » 84.0
29
-------
in
CM
50
EFFECT OF BARIUM SULFATE ON
DESTRUCTION OF 0.1% 2,4,5-T
AT 0.4 MEGARAD
I
I
0 10 20 30 40 50
GRAMS OF BARIUM SULFATE ADDED TO 20 ML SAMPLE
Figure 7. Barium Sulfate enhancement of radiation effects.
30
-------
Ferric sulfate was apparently without effect, but all other
materials decreased the amount of destruction. These findings
suggest that the irradiation of manufacturing waste effluents is
likely to be very inefficient due to the diversity of materials pre-
sent, many of which would interfere with utilization of the radiation.
31
-------
SECTION VI
REFERENCES
1. Spinks, J. W. T. and R. J. Woods. An Introduction to Radiation
Chemistry. New York, John Wiley and Sons, Inc., 1964. p. 294.
2. Elridge, D. A. The Gas-chromatographic Determination of 2,3,7,8-
Tetrachlorodibenzo-p-dioxin in 2,4,5-Trichlorophenoxyacetic Acid
("2,4,5-T11), 2,4,5-T Ethylhexyl Ester, Formulation of 2,4,5-T
Esters and 2,4,5-Trichlorophenol. Analyst (London). 96;721-27,
1971. .
3. Rennard, R. J., Jr. and W. L. Kehl. The Hydrolysis of Aryl-
chlorides Over Rare Earth Phosphate Catalysts. (Presented at ACS
Division of Petroleum Chemistry. New York. August, 1972.)
ADDITIONAL REFERENCES
Blair, E. H. Chlorodioxins - Origin and Fate. Washington, D. C.,
American Chemical Society, 1973.
Craft, T. F. and G. G. Eichholz. Dyestuff Color Removal by
Ionizing Radiation and Chemical Oxidation. U. S. Environmental
Protection Agency. Washington, D. C. Report EPA-R2-73-048. 1973.
Craft, T. F. and G. G. Eichholz. Decoloration of Textile Dye Waste
Solutions by Combined Irradiation and Chemical Oxidation. Nuclear
Technology. 18:46-54, 1973.
Edwards, C. A. Persistent Pesticides in the Environment.
Cleveland, CRC Press, 1970.
Friedlander, G., J. W. Kennedy, and J. Miller. Nuclear and
Radiochemistry. New York, John Wiley and Sons, Inc., 1964.
Garrison, A. W., F. N. Case, D. E. Smiley, and D. L. Kau. The
Effect of High Pressure Radiolysis on Textile Wastes, Including
Dyes and Dieldrin. (Presented at 5th International Conference on
Water Pollution Research. San Francisco. July, 1970.)
Kimbrough, R. D. Gamma Irradiation of DDT: Radiation Products and
Their Toxicity. Journal of Agricultural and Food Chemistry.
19_: 1037-1038, 1971.
32
-------
Lenz, B. L., E. S. Robbins, F. N. Case, D. E. Smiley, and D. L. Kau.
The Effect of Gamma Irradiation on Draft and Neutral Sulphite Pulp
and Paper Mill Aqueous Effluents. Pulp and Paper Magazine of Canada.
72:75-80, 1971.
Matsumura, F., G. M. Baush, and T. Misato (Editors). Environmental
Toxicology of Pesticides. New York, Academic Press, Inc., 1972.
Morris, R. D. and T. F. Craft. Degradation of Acid Dyes by
Irradiation Plus Oxidation. International Journal of Applied
Radiation and Isotopes. 2A_:245-52, 1973.
Sherman, W. V., R. Evans, E. Nesyto, and C. Radlowski. Dechlorination
of DDT in Solution by Ionizing Radiation. Nature. 232;118, 1971.
Swallow, A. J. Radiation Chemistry of Organic Compounds. New York,
Pergamon Press, Inc., 1960.
Whittemore, W. L. Ionizing Radiation for the Treatment of Municipal
Waste Waters. Gulf General Atomic Final Report GA-9924, Contract
AT(04-3)-167. Atomic Energy Commission, Division of Technical
Information. 1970.
Zabik, M. J., R. D. Schuetz, W. L. Burton, and B. E. Pape. Photo-
chemistry of Bioactive Compounds: Major Photolytic Produce of Endrin.
Journal of Agricultural and Food Chemistry. 19_:308, 1971.
33
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-660/2-75-017
3. RECIPIENT'S ACCESSIOf*NO.
4. TITLE AND SUBTITLE
Radiation Treatment of High Strength Chlorinated
Hydrocarbon Wastes
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
T. F. Craft, R. D, Kimbrough, C. T. Brown
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Engineering Experiment Station
Georgia Institute of Technology
Atlanta, Georgia 30332
10. PROGRAM ELEMENT NO.
1BB036
11. CONTRACT/GRANT NO.
R800312
12. SPONSORING AGENCY NAME AND ADDRESS
US Environmental Protection Agency
National Environmental Research Center-Corvallis
Southeast Environmental Research Laboratory
College Station Road, Athens, Georgia 30601
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The possible use of gamma radiation for the treatment of waste effluents
containing chlorinated hydrocarbons, particularly pesticides, has been investigated.
Significant destruction was obtained of representative compounds such as
pentachlorophenol, 2,4,5-trichlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic
acid. Radiation treatment had little effect on polychlorinated biphenyls or
mixtures of compounds, including actual manufacturing effluents.
It was found that the addition of a material of high atomic weight, such as
barium, increased the efficiency of radiation utilization. No other materials were
found which increased the desired destruction. G-values were calculated for
pentachlorophenol, 2,4,5-trichlorophenoxyacetic acid, and 2,4-dichlorophenoxyacetic
acid.
It is concluded from the magnitude of these values that radiation treatment of
chlorinated hydrocarbons is not economically feasible at the present level of
radiation costs.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pesticides, Water Pollution Treatment,
Gamma Radiation, Polychlorinated Bi-
phenyls, 2,4,5-T, 2,4-D, Pesticides
Control, Chlorinated Hydrocarbons,
Tertiary Treatment
Pesticide Manufacturing
Industry
06/06
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
39
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
* U. S. GOVERNMENT PRINTING OFFICE: 1975-698-778 /I68 REGION 10
------- |