WATER POLLUTION CONTROL RESEARCH SERIES
16040 ELO 06/70
Investigation of Means for
-
Controlled Self-Destruction of Pesticides
ENVIRONMENTAL PROTECTION AGENCY • WATER QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH SERIES
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INVESTIGATION OF MEANS FOP CONTROLLED
SELF-DESTRUCTION OF PESTICIDES
AEROJET-GENERAL CORPORATION
ENVIRONMENTAL SYSTEMS DIVISION
9200 EAST FLAIR DRIVE
EL MONTE, CALIFORNIA 91731+
for the
WATER QUALITY OFFICE
ENVIRONMENTAL PROTECTION AGENCY
160UO ELO
JUNE 1970
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, B.C. 20402 - Price $1.25
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WATER QUALITY OFFICE/EPA REVIEW NOTICE
This report has been reviewed by the Water Quality Office of the
Environmental Protection Agency and approved for publication.
Approval does not signify that the contents necessarily reflect
the views and policies of the Water Quality Office, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
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ABSTRACT
Laboratory studies demonstrated the feasibility of controlled destruction
of chlorinated pesticides such as DDT.* The concept comprised (1) means
to degrade DDT to a harmless form, and (2) methods to delay the reaction
for given pest-control action.
Chemical methods for degrading DDT were screened and reduction was
selected as the most promising technique. Destruction of DDT, with-
out forming DDE as a product, was demonstrated in laboratory studies
by mildly acidic reduction with zinc powder. The principal product is
bis(p-chlorophenyl) ethane, DDT with all three aliphatic chlorines re-
moved; a material stated to be "void of the neurotoxic effects of DDT. "
Catalysis of the reaction resulted in complete destruction of DDT in
1 hr at 25°C and conversion to bis(chlorophenyl) ethane in 4-8 hrs.
Catalyzed aluminum or iron reduction of DDT produced tetra(p-chloro-
phenyl)tetrachlorobutane, reportedly lipoid insoluble.
A 90% destruction of DDT in soil in 4 days was demonstrated in a
laboratory test with spray-applied integral, catalyzed zinc-DDT particles
(5-micron).
Reaction delay can be achieved with wax or silicone coatings on the
reductant which are slowly dissolved or eroded, or possibly slow air
oxidation of sulfur. Coatings were produced which stopped zinc-acid
reaction. A test of combined reductant - delayed action technique was
made using silanized, catalyzed zinc (5 microns)-DDT particles sprayed
onto soil. Although faulty coating prevented the desired delay, 95% de-
composition of DDT was obtained.
Effective reductive degradation of the chlorinated pesticides dieldrin,
endrin, aldrin, chlordane, toxaphene, Kelthane, methoxychlor, Perthane
and lindane, and selected polychlorinated biphenyls was shown.
Degradation of DDT in water was demonstrated, a 421 mg/1 DDT sus-
pension being reduced to 1 ppm after 1 hr reaction at 75°C.
This report was submitted in fulfillment of Contract 14-12-596 between
the Federal Water Quality Administration and Aerojet-General Corporation.
Key Words: Pesticide Degradation, DDT, Reduction, Encapsulation,
Soil, Water, Chlorinated Pesticides, Polychlorinated
Biphenyls.
See glossary for formulas of pesticides and degradation products.
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CONTENTS
Section
I. CONCLUSIONS
II. RECOMMENDATIONS
III. INTRODUCTION
IV. SELECTION OF DEGRADATIVE TECHNIQUE FOR
DDT
V. DEGRADATION OF DDT BY METALS 35
VI. DEGRADATION OF DDT BY CATALYZED METALS 51
VII. DEGRADATION OF DDT IN SOIL 71
VIII. DEGRADATION OF DDT IN WATER 77
IX. CONTROLLED DELAYED REACTION TECHNIQUES 83
X. EVALUATION OF DELAYED ACTION DEGRADATION 87
OF DDT
XI. REDUCTIVE DEGRADATION OF OTHER CHLORINATED
PESTICIDES AND CHLORINATED BIPHENYLS 89
XII. ANALYSIS OF STUDIES 101
XIII. ACKNOWLEDGMENTS 107
XIV. REFERENCES 109
XV. PATENTS AND PUBLICATIONS 115
XVI. GLOSSARY OF PESTICIDES AND DEGRADATION 117
PRODUC TS
XVII. APPENDIX 121
11
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FIGURES
No.
1. Rate of Formation of bis(p-Chlorophenyl) Ethane
Product (DDEt) at 25°C When DDT Reduced With
Zn* Cu Couple, or Zn Powder
2. Rate of Formation of bis(p-Chlorophenyl) 55
Dichloroethane Product (DDD) at 25°C When DDT
Reduced With Zn« Cu Couple, or Zn Powder
3. Rate of Formation of bis(p-Chlorophenyl) 56
Chloroethane Product (DDMS) at 25°C When DDT
Reduced With Zn- Cu Couple, or Zn Powder
4. Gas Chromatographic Analyses of Dieldrin, and 91
Dieldrin Following Reduction by Zinc or Catalyzed
Zinc
5. Gas Chromatographic Analyses of Chlordane, and 93
Chlordane Following Reduction by Zinc or Catalyzed
Zinc
6. Gas Chromatographic Analyses of Heptachlor, and 94
Heptachlor Following Reduction by Catalyzed Zinc
7. Gas Chromatographic Analyses of Toxaphene, and 96
Toxaphene Following Reduction by Zinc or Catalyzed
Zinc
111
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TABLES
No. Page
I. Summary of Screening Tests of DDT Degradation 10
II. Rate of Catalyzed Zinc Reduction of DDT at 25°C 63
III. Selected Characteristics of Greenfield Sandy Loam 73
Used in Soil Studies
IV
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SECTION I
CONCLUSIONS
• The feasibility of controlled, self-destruction pesticides
was demonstrated by the effective degradation of DDT using a reductive
process with coatings to delay inception of the degradation reaction.
• Degradation of DDT with a mildly acidic reduction by zinc
leads to the formation of bis(p-chlorophenyl) ethane, a product from
which all three of the aliphatic chlorines in DDT are removed. The
reaction was carried out in the laboratory at ambient temperature
without forming DDE as a product.
• The mildly acidic zinc reduction of DDT can be effectively
catalyzed by copper to give a 2-4 fold faster ambient temperature re-
action and an equivalent greater conversion to the bis(chlorophenyl)
ethane product. The catalyzed system appears to promote the direct
conversion to the ethane product, whereas the uncatalyzed system
may proceed by a slower, stepwise dechlorination of DDT.
• Reaction of DDT with mildly acid copper-catalyzed alumi-
num or iron has led to the formation of a reductive condensation product
1, 1, 4, 4-tetra(p-chlorophenyl)-2, 2, 3, 3-tetrachlorobutane. This hexane-,
acetone- and water-insoluble, high-melting-point solid, is reportedly
lipoid insoluble and hence would presumably not be transmitted to life
forms as a fat soluble species.
• An effective degradation of DDT appears possible in soil
by using a micron-sized particle of the reductant in close proximity
to the DDT. A 90-95% reduction of the DDT in 4 days was achieved
under laboratory conditions by this technique.
• Two techniques appear to hold promise for the controlled
delay of the degradation reaction. Thin, slowly-soluble, wax or silyl
coatings on the reductant have succeeded in stopping the reaction of
micron-sized zinc particles with acid. The second technique which
may hold promise for reaction delay involves the slow air oxidation
of sulfur to produce required acidity for the reaction in situ.
• Although a test of the combined reduction-controlled delay
reaction with a DDT-silyl coated, catalyzed zinc system sprayed onto
soil did not give the requisite delay because of faulty coating, the fact
that a 90-95% reduction of the DDT in soil was achieved is believed to
provide ample evidence that the technique will work, given an initially
impervious coating.
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• Effective degradation of DDT in water has been achieved in
suspensions containing as little as 1 mg/1 of DDT. Both stirred re-
actors and packed bed columns were effective in significantly reducing
the DDT level of simulated and real DDT-laden waste streams.
• The reductive degradation technique has been found effec-
tive in completely or substantially degrading the chlorinated cyclodiene
pesticides dieldrin, endrin, aldrin and chlordane; the chlorinated cam-
phene toxaphene; the pesticides related to DDT: Kelthane, methoxychlor
and Perthane; the hexachlorocyclohexane pesticide lindane; and selected
polychlorinated biphenyls. However, the extent of degradation and the
products of the reaction are not known as yet.
• The reductive degradation process appears to be econo-
mically feasible, the theoretical cost for zinc powder to reduce DDT
to bis(p-chlorophenyl)ethane being about 5. 5 cents/lb of DDT, while
the cost is calculated to be 1.0 cents/lb or 0. 2 cents/lb of DDT if the
reductant is respectively catalyzed aluminum or catalyzed iron and
the product is the tetra(chlorophenyl) tetrachlorobutane. The simple
coating process and materials suggest that the reaction delay process
may also be economically feasible. The fact that the DDT-reductant
particles can be suspended and sprayed by a conventional air-blast
atomizer also suggests practicality of the approach.
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SECTION II
RECOMMENDATIONS
This study had as its objective the determination of the feasibility of
a concept for the controlled degradation of chlorinated pesticides.
With the establishment of the feasibility of this concept, the further
development of this important process for the several applications
that appear evident from these studies is recommended. These
include:
• Development of the process for controlled des-
truction of field-applied DDT.
• Development of the process for controlled des-
truction of field-applied chlordane, toxaphene
or other chlorinated pesticides of importance.
• Extension of the studies to the treatment of chlo-
rinated cyclodiene pesticide wastes, such as
the dieldrin used in wool mothproofing opera-
tions .
• Further development of the reductive degrada-
tion technique for the treatment of waste effluent
or accidental discharge from DDT manufacturing
plants.
• Examination of the feasibility of the reductive
degradation technique for degrading polychlor-
inated biphenyls (PCB's), and the development
of suitable waste control procedures to be used
with PCB's.
• Examine the feasibility of using the reductive
degradation technique for cleaning up agricultural
fields contaminated with chlorinated pesticides,
and for destroying surplus or waste pesticide pro-
ducts.
It will be important in developing suitable degradative techniques to be
assured that the products are harmless to life forms, and indeed to
know the extent to which the pesticide must be changed in order that
it not present a problem to the environment. While acute toxicity data
is generally known or can be obtained readily, the chronic or reproduc-
tive effects that lead to the "thin-eggshell syndrome" on exposure to
DDE or dieldrin are not well understood. This understanding is required
for the effective development of pest control agents.
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SECTION III
INTRODUCTION
The objective of this study has been the determination of the feasibility
of the degradation of persistent chlorinated pesticides to a form harm-
less to life, with the pesticide detoxification being delayed for a suit-
able time period so that the pest-control agent could exercise its
designed function. DDT was selected as the chlorinated pesticide to
be examined in initial studies, although limited tests with other chlor-
inated pesticides were to be undertaken if time permitted.
Although an initial degradation of DDT to DDE was proposed, it was
determined that more complete degradation of DDT without forming
DDE as a product was strongly desirable, and the objectives of the
study were modified accordingly. The degradation of 80% of the pest-
icide in one week at ambient temperatures was an initial goal. Delay
of the degradation for 15 to 30 days, or until sloughing-off from the
plant to the ground, were assumed as target times.
The program as initially set up consisted of five phases: (1) Selection
of Detoxification Reagents, (2) Selection of Controlled Delaying Tech-
niques, (3) Laboratory Evaluation of Delayed Pesticide Degradation
Reaction, (4) Laboratory Feasibility Examination of Application of
Reagents with Spray Formulation, and (5) Evaluation of Concept Feasi-
bility. The early determination that DDE was an undesirable product re-
sulted in primary emphasis on the first task: the study of the basic
chemistry of degradation leading to a selection and development of the
degradation reagent system.
The selection of the degradation reagents was based on the results of
a screening study in which five basic mechanisms of DDT degradation
were examined. These five basic techniques included Lewis-acid cata-
lysis, free radical catalysis , oxidation, reduction, and hydrolysis. On
the basis of these studies, the reduction technique was chosen for fur-
ther development, and studies directed towards the development of
simple and effective reductive degradation techniques will be described.
Application of the technique to reduction of other chlorinated pesticides
and to the related polychlorinated biphenyls is also described, as well
as studies showing that the reductive degradation of DDT in water and
soil can be achieved.
The selection of controlled delaying techniques involved studies with
two basic mechanisms of reaction delay. The first involved the use of
coatings on a reactive ingredient (such as the reductant) which would be
slowly dissolved or eroded from the particle, thus allowing a reaction
after a given delay period for pest control action. This is the basic
technique employed with many of the "controlled-release" fertilizers
(Reference 1). The second basic technique employs a slow reaction to
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generate an essential ingredient for the reductive reaction.
Limited studies of the delayed degradation of DDT in soils have also
been undertaken. These tests have included the reductive degrada-
tion of DDT in soils, and tests in which coated reductant was applied
to soil along with the pesticide DDT. In some of these tests the
pesticide and the reductant were applied simultaneously by a spray-
ing technique; indeed, it will be shown that simultaneous application
of the pesticide and degradation reagents is the preferred mode of
application. j
The analysis of the concept feasibility will be a part of this report.
In the sections to follow, the basic chemistry and experimental re-
sults leading to a selection of the reductive technique will be described,
the development of the dissolving metal reduction of DDT will be summa-
rized, the discovery that the basic metallic reduction technique can be
catalyzed to yield a significantly more rapid and selective process will
be described, studies leading to the degradation of DDT in waste waters
will be summarized, the results of tests of the degradation of DDT in
soil will be given, delayed reaction studies will be summarized, and
the tests of the combined application of a delay technique and the re-
ductive degradation process to studies on soil will be described. Data
showing that the reductive degradation technique is applicable to chlor-
inated pesticides other than DDT, and to the related industrial com-
pounds, the polychlorinated biphenyls, will also be given.
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SECTION IV
SELECTION OF DEGRADATIVE TECHNIQUE FOR DDT
The initial task of the Aerojet studies under Contract 14-12-596 consisted
of the examination of several possible degradative techniques for DDT and
from these the selection of the most promising mechanism for the prac-
tical destruction of the pesticide. Some of the basic considerations leading
to the selection of the optimal means for DDT degradation include:
• Degradation to proceed to the greatest extent possible,
removing a significant amount of chlorine from the
molecule. The products DDE and DDD were to be avoid-
ed if possible. The major products should be harmless
to life forms, whether mammalian, fish, or bird life.
• The degradative reaction should proceed to a substan-
tially complete destruction of DDT at ambient temp-
erature (~25°C) in periods of a week or less.
• The reaction should be capable of being carried out in
both soil and water, so that detoxification of both
of these media may be achieved.
• The degradative technique should be economically
feasible, and should not employ difficult to obtain
materials.
• The catalyst or degradative materials used should not
result in the introduction of harmful materials into
the environment.
Basic Chemistry of Degradation of DDT
An examination of the basic chemistry of DDT and other halogenated organic
compounds suggested several processes which should be investigated for
their feasibility in practically degrading DDT in accordance with the consid-
erations outlined. The reviews published on the chemistry of DDT (e. g. ,
References 2, 3,4, 5) suggest that the material is a relatively stable moiety,
although some techniques are known for its decomposition.
It has been known that the dehydrohalogenation of DDT to DDE could be cata-
lyzed by iron and iron salts, anhydrous aluminum chloride and certain min-
eral carriers (Reference 6). In studies in which the stability of DDT and
other chlorinated pesticides was related to the "surface acidity" of mineral
carriers, it became evident that dehydrochlorination was catalyzed by an
acidic nature of the carrier surface (References 7,8). Indeed, these studies
suggested a correlation between pesticide stability in contact with mineral
carriers and a low surface acidity. Conversely, highly acid surfaces were
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found to catalyze decomposition, in the case of DDT apparently lead-
ing to conversion to DDE. The use of strong Lewis-acid catalysts to
promote decomposition was one mode which was selected for evalua-
tion.
The photochemical decomposition of DDT reportedly occurs by a free-
radical mechanism (Reference9). Hence the use of catalysts which
promote free-radical reactions might be expected to be useful in
effectively degrading DDT, so materials of this type were also eva-
luated for their efficacy in degrading this pesticide.
Although it has been reported that DDT is relatively stable to reduc-
tion, it is known that the molecule can be degraded under rigorous
conditions to products other than DDE. For example, Beckman and
Berkenkotter (Reference 10) used sodium-liquid anhydrous ammonia
system to dechlorinate DDT, giving 1, 1-diphenyl ethane as the pro-
duct. Reduction by sodium in refluxing isopropanol with subsequent
titration of the chloride is a standard method for DDT analysis
(Reference 11). Less rigorous conditions for reduction were suggested
by Hornstein (Reference 12), who found that by passing DDT through
a zinc column, a 50% reduction of the chlorine content could be realized.
In another study, Romano (Reference 13) reported the reduction of
three of the five chlorine atoms on DDT by refluxing an alcoholic-
kerosene solution of DDT with ammonium sulfate and zinc. Although
these procedures suggest that DDT may be reduced without forming
DDE as a product, it remained to be determined that the reaction
would proceed in a practical way at ambient temperatures without
employing columns, exotic reagents, or other conditions which would
negate a practical field-applied degradation process. Clearly, fur-
ther studies were required to determine the feasibility of a practical
reductive attack of DDT.
The dehydrohalogenation of DDT by base is well known and has been
used extensively for the analysis of DDT. The kinetics of alkaline
hydrolysis have been investigated by many workers (e. g. , Cristol,
Reference 14). It has also been determined that basic amines are
capable of extracting an HC1 molecule from DDT to give DDE (Ref-
erence 15). Although the simple removal of one HC1 from DDT is
generally assumed on alkaline hydrolysis, Grummitt, Buck and
Stearns reported that elevated temperature hydrolysis under severe
conditions leads to the formation of the bis (p-chlorophenyl) acetic
acid, DDA (Reference 16). Accordingly, limited experiments were
conducted in order to determine if the hydrolysis reaction of DDT could
be made to proceed readily to an end product other than DDE.
It is well known that the body converts DDT to the soluble acetic acid
derivative, DDA (bis(p-chlorophenyl) acetic acid) (Reference 17). Hence
a brief examination of oxidizing techniques for the degradation of DDT
were considered.
8
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In summary, it will be shown that the reductive technique is pre-
ferred for effective ambient temperature degradation of DDT without
forming DDE as a product. The results of the screening tests are
summarized in Table No. 1; the details of the tests will be presented
in the sections to follow. Available information on the toxic proper-
ties of some important products of the reaction are also given; these
data appear to substantiate the selection of the reductive degradation
of DDT to yield bis (p-chlorophenyl) ethane as a product which would
appear to be without the toxic effects of DDT. The data from the screen-
ing tests will be grouped according to the type of reaction which was
investigated.
The principle product analysis has been by gas chromatography. The
methods of analysis and identification of product peaks are described
in Appendix A.
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TABLE 1
SUMMARY OF SCREENING TESTS OF DDT DEGRADATION
LEWIS ACIDS:
A1C13, AlBr3
Fed 3
Clays, halide salts
REDUCTION:
Zn + dil acetic acid
Zn + (NH4)2S04
FREE RADICAL:
Benzoyl peroxide
Other peroxide catalysts -
Redox system
OXIDATION:
Hot chromic acid
(117-120°C)
KMnO4
ALKALINE HYDROLYSIS:
KOH - ethanol
KOH - n-butanol
KOH - ethylene glycol
extensive degradation at 25, 50,
100°C. DDE a substantial product.
less effective than AlClg.
generally ineffective.
complete degradation of DDT with-
out DDE as a product. Reaction
proceeds at 25°C.
degradation as with acetic acid but
slower at 25° C.
complete conversion to DDE at
100 C; little reaction at lower temp-
eratures.
none effective at ambient tempera-
ture.
substantial 25°C conversion to DDE.
slow reaction; 40% DDT reacted in
8 hr.
little reaction at 25°C.
essentially complete conversion to
DDE at 78°C.
conversion to DDE and other pro-
ducts at 117°C.
complete consumption of DDT at
l68-175°C, mainly giving unidenti-
fied products.
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SCREENING TESTS
Lewis-Acid Catalysts
An extensive investigation of the applicability of strong Lewis-acids
as catalysts for DDT degradation was made. This decision was pre-
dicated on the observation that certain mineral fillers and metal halide
salts were known to catalyze the degradation of DDT, but the practical
extent of reaction was not known. If a clay-like catalyst, for example,
could be found which promoted degradation of DDT to desired end pro-
ducts, a system would be provided which would satisfy the require-
ments for a process which would not add harmful materials to the
environment.
In the discussion to follow, data will be presented in which the metal
halides and metal halide hydrates, modified montmorillonite catalysts,
commercial clay catalysts, and some BE-, adducts were examined as
catalysts. Data will also be shown on the effect of a solvent on the
reaction (most of the tests were conducted on dry mixes of DDT and
the catalyst), and a correlation with the Hammett acidity will be pre-
sented.
A1C13
Anhydrous aluminum chloride is a well-known catalyst for a variety of
organic reactions reportedly effective in degrading DDT* (Reference 6).
The A1C13 was ground in an agate mortar before blending, the DDT was
added and the samples were blended by grinding in the mortar for 5-10
minutes. These operations were conducted in a dry box, because of
the affinity of anhydrous AlClg for water.
Samples weighing about 1 g were placed in 16 x 150 mm glass-stoppered
test tubes and were heated in a thermostatted, stirred oil bath at 100°C
for 2 hr. After less than 5 min reaction, the evolved gases blew the
stopper from the test tube and the reaction mass turned to a black char.
The sample was removed from the bath after 2 hr, cooled, and the mass
dissolved in benzene. The black char dissolved very slowly and the re-
sultant solution was colored red. A black residue which was soluble in
water, although insoluble in benzene, was filtered off; the residue
The DDT used in these experiments was purified by recrystallizing
from absolute ethanol twice; mp 108. 6-108. 8°C. In this report, the
term DDT indicates purified p, p'-DDT unless otherwise stated.
11
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appeared to be AlCl^. The gas chromatographic analysis of the solu-
tion was as follows:
Gas Chrom.
Component Retention Time, Min. %•>'
DDE 15.2 26.3
16.3 57.5
ODD 17.8 13.7
DDT 21.0 1.0
28.8 1.3
It is important to note that essentially all of the DDT was decomposed
under these conditions. Although a substantial amount of DDE was ob-
tained, two additional unidentified peaks accounting for 59% of the
observed decomposition were obtained. One attempt was made to iden-
tify these peaks by trapping gas chromatographic effluent with a given
retention time range and subjecting the material to mass spectral anal-
ysis. The DDE peak was confirmed but other peaks were not identified.
The ambient temperature decomposition of DDT by A1C13 has also been
observed. "When DDT was ground with lOwt. %AlCl3, an immediate
coloring of the mix was obtained. An analysis of the mix after approxi-
mately 2 days and 1 week reaction at 25° follows:
Retention Analysis, %, after Reaction, hr, at 25 C
Product**
DBF
DDE
ODD
DDT
Time, min
9.8
14.2
15.1
16.4
17.6
19.0
21.0
23.4
27.6
28.5
29.3
31.2
32.4
34.4
37.9
40.9
42. 3
44.4
47.4
45
_
-
0.7
5.0
28.6
5.4
56.3
_
_
_
_
1.0
0.7
_
<0.7
<0.7
1.0
1.2
"•
166
1.8
5.3
48.9
16.0
_
-
15.0
0.3
4.3
0.7
1.2
_
_
1.0
0.3
5.1
_
_
0.3
* Analysis liased on the calibration curve for DDT; the sensitivities
for other materials with retention times in the range cited will be
approximately the same as DDT.
**See Glossary for names and chemical formulas of products.
12
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The sample experienced a \veight loss (presumably HC1) of 7. 3%
over the 166-hour reaction period.
Several general conclusions can be made. First, the gas chromato-
graphic analysis indicates a large number of degradation products so
that substantial degradation beyond DDE is being obtained. Secondly,
decomposition of the DDT at room temperature in reasonable periods
of time was achieved with this strong Lewis-acid type catalyst.
A comparison of the overall rate of DDE appearance and DDT removal
can be made. 45 hr 166 hr
Rate of DDE appearance, %/hr .64 .30
Rate of DDT removal, %/hr .97 .51
The sensitivity of the aluminum chloride to moisture was shown when
material which was stored in a presumeably dry atmosphere was found
to rapidly loose its activity, yet a freshly-opened bottle of the anhy-
drous aluminum chloride reproduced the preceding data.
It was observed in carrying out the reactions that extensive mixing of
the samples in the mortar and pestle would produce dark "reaction-
zones", where immediate reaction was obtained. In an effort to sepa-
rate the A1C13-catalyzed reaction from possible localized heating
effects, a means for sample mixing which did not require grinding of
the mixed samples was investigated.
A small "V" shaped particle blender was constructed of glass, the two
arms of the blender being 1 cm dia by 4 cm long. The "V" blender was
turned by a small motor at-a rate of 20 RPM. This blender is a scale-
down of a
commercial type particle blender; a unit of this type had been used
previously by the investigators for efficient mixing of small, fine-
particle blends.
When samples of finely-ground A1C13 and DDT were mixed in the
blender, it was found that reaction was initiated at ambient tempera-
tures. However, two important observations were made. First,
sample darkening indicative of reaction appeared most extensive at
areas on the reaction tube where relatively high concentrations of the
catalyst were evident; this observation had also been made previously
when extensive darkening of a sample appeared to initiate in fine dust
located on the sides of the reaction tube. Secondly, progressive dark-
ening appeared to spread from small dark reaction sites in the mix.
Thus autocatalysis must be considered.
13
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In an effort to further characterize the effect of AlClg mixing and
concentration, a sample consisting of DDT, 1% Ca.^CPO^)2 added to
promote free-flowing properties, and 29. 1% anhydrous A1C1, was
prepared. The mixture turned brown immediately upon mixing and
soon tended to be "sticky" in texture. Within 1 hr at 25° the reaction
mix turned a dark purple color. The mix was allowed to react for
116 hr at 25°C. The weight loss after this time was 15. 7%. The
results of the analysis of the reaction mix follow:
Retention
Component Time, min Reaction 116 hr at 25°C, %
1.6 0.3
10.4 0.9
13.4 0.1
14.8 2.5
DDE 15.6 10.8
17,0 18.4
DDT 21.4 0.1
22.2 0.3
28.4 3.7
35.4 0.7
40.4 0.4
42.0 1.0
The analysis does not account for 61% of the sample. However, thin-
layer chromatography results indicate that DDA may be a major pro-
duct; DDA will not respond in standard gas chromatography.
These results show that DDT may be degraded by AlClo, but the ma-
terial is highly moisture-sensitive. Further, DDE is a significant
product. A large number of other products, mainly small quantities,
are obtained.
A1C13 Hydrate
In an effort to establish that the aluminum chloride catalysis is due to a
strong Lewis-acid rather than an effect specific to AlClo, an experi-
ment was also conducted with the hydrate of AlClo, since the water is
a strong Lewis base. The results of reaction of DDT with 10% (A1C1,
anhyd. basis) of A1C13. 6H2O for 2 hr at 100°C follow:
Component Retention Time, Min. %
12.1 trace
13. 3 trace
DDE 15.4 1.5
DDT 21.0 98.5
Thus the hydrate of A1C1, was ineffective in promoting DDT decompo-
sition.
14
-------
AlBr3
A recent analysis of the Lewis-acidity of covalent metal halides by
Satchell (Reference 18) suggests that AlBr3 should be a stronger
Lewis acid than AlClj. A sample of the material was therefore pro-
cured and its reactivity with DDT was examined.
In the experiment, 1 g of recrystallized DDT was mixed with 12% by
weight of AlBr, in the "V" mixer. The ingredients immediately be-
came black and sticky. The mix was transferred to a mortar and
blended with a 'spatula without grinding. After 15 min at 25°, the mix
was dissolved in benzene, filtered and analyzed. The results follow:
Retention Analysis, %, after 15 min
Component Time, Min Reaction at 25°C
DBF 10.1 0.1
12.2 0.2
DDMU 13.1 1.2
DDMS 14.5 1.8
DDE 15.6 22.5
16.8 5.5
DDD 18.1 0.6
19.0 6.3
DDT 21.0 26.6
21.8 5.0
24.8 0.3
28.8 0.4
29.8 0.5
32.2 <0.1
35.1 0.2
36.8 0.2
39.8 0.7
41.8 2.9
Approximately 25% of the products were not found in the gas chroma-
tographic analysis and may represent products which will not elute from
the column under the conditions employed (DDA and p-chlorobenzoic
acids, for example). It is clear that very substantial degradation of
the DDT was obtained with AlBro catalyst, leading to a large number of
products. The reaction was rapid, too, since a 74% destruction of DDT
occurred in 15 min at room temperature. However, AlBro is very hy-
groscopic and loss of activity would be expected after brief exposure to
moisture-laden air.
FeCl3
Anhydrous ferric chloride has been reported to be effective in DDT
decomposition, similar to AlClj (Reference 6). Indeed, the results
with 10% by weight of anhydrous ferric chloride resemble those with
aluminum chloride in that a strong reaction leading to a charred
15
-------
reaction mass was observed after less than 5 min reaction at 100°C.
After 2 hr reaction the mass was dissolved in benzene, yielding a
dark green solution. A tan-white insoluble residue (6. 3% of the DDT
weight) was filtered off; the residue (probably Fed 3 or FeCl2) was
water soluble. The analysis of the benzene solution was as follows:
Reaction of DDT with 10% FeCl3 for 2 hr at 100°C
Component Retention Time, Min. %
14.7 12.8
DDE 16.0 81.8
16.9 5.0
DDT 21.3 0.2
25.7 0.1
Thus, DDT was essentially completely decomposed under these con-
ditions, with approximately 80% of the material being present as DDE
and 20% apparently as the same two unidentified products which were
obtained when AlClg was employed as a catalyst.
The reaction of DDT with 10% by weight of anhydrous FeClo was also
studied at 25°C. The results after nominal 1-day and 5-day reaction
follow:
Retention Analysis, %, after Reaction, hr, at 25°C
Component Time, min
12.6
15.0
DDE 15.7
ODD 18.8
DDT 21.3
29.8
30. 3
33.0
35.4
43.6
In another test in which the FeCl^ had apparently absorbed some mois
ture from the air, a 45 hr reaction of DDT with 10% by weight of FeCl
resulted in 94. 8% of the DDT being unreacted with 5. 2% being present
as DDE. After 166 hr, the DDT assayed 92. 7%, while 6. 8% was DDE.
Thus, reaction of DDT with FeCl3 at ambient temperature appears to
proceed much more slowly than with AlClo.
FeCl3 Hydrate
A result similar to that obtained with aluminum chloride hydrate was
obtained when FeCl^. 6H2O was used in an attempt to catalyze DDT
decomposition. The amount of the salt was adjusted to contain the
16
24
0.1
0.3
3.5
0. 1
95.7
-
_
0.4
-
-
lib
0.1
0.8
9.8
0.4
84.3
0.1
0.2
3.5
0.5
0.5
-------
same concentration of FeCl, as was used in the anhydrous salt re-
action.
2 hr Reaction of DDT + 10% (anhyd basis)
FeCl3. 6HzO at 100°C
Component ' Retention Time, min^c
13.2 <0.5
DDE 15.4 2.0
DDT 20.7 98.0
Protonated Montmorillonite
A siliceous material which reportedly has a high surface acidity and
hence might be expected to degrade DDT is the protonated form of
montmorillonite clays. The process for preparation of the material
is basically that employed by Dr. G. W. Bailey of the Southeast Water
Laboratory, FWQA (Reference 19).
Montmorillonite from Upton County, Wyoming (Ward's No. 25) was
separated as a< 2 p- fraction by sedimentation in water. The fine frac-
tion was air dried and then heated at 240°C overnight. The montmor-
illonite was then converted to the acid form by slowly passing a 1%
suspension of the clay through an acid-form Amberlite IR-120 ion
exchange column. The material was passed through the 48 mm dia x
50 cm long column at a rate of 2 ml/min. The effluent was then centri-
fuged to separate it from the bulk of the water and freeze-dried (pro-
duct temperature -10 to -20°C, ~ .5 mm pressure). The material
was stored at dry ice temperatures overnight until use.
A 10% mixture of the acid form montmorillonite was reacted with DDT
for 2 hr at 100°C. After that period of time the mass had darkened
appreciably and a 0. 22% weight loss was obtained. The benzene solu-
tion was yellow colored; however, analytical data for the initial experi-
ment show that no significant decomposition had occurred.
Retention
Component Time, min Reaction 2 hr at 100°C, %
DDE 15.4 3.4
DDT 20.6 96.6
A further attempt to catalyze DDT decomposition with the protonated
montmorillonite was made when a new batch of the montmorillonite
was converted to the acid-form, freeze-dried, and the reaction run in
a single day so that stability considerations could be minimized.
The montmorillonite was converted to the acid form by slowly passing
it through a freshly regenerated IR-120 ion exchange resin, using the
same procedure as outlined previously. The pH of the effluent acid-
form montmorillonite suspension was 2. 50. After the material was
freeze-dried, the surface acidity was determined with Hammett
17
-------
indicators. The material gave a strong, yellow coloration with the
benzalacetophenone indicator (pKa -5. 6), but did not give a color with
anthraquinone (pKa-8. 2), giving a pKa for the material between -5. 6
and -8. 2. The results of a test in which 10% of the freshly prepared
protonated montmorillonite was reacted with DDT for 2 hr at 100°C
yield the following analytical results:
Retention
Component Time, min Reaction 2 hr at 100°C, %
14.8 0.2
DDE 15.6 5.2
17.0 0.3
DDT 21.4 88.3
Clearly, significant decompositon of DDT was not obtained with this
catalyst.
Copper Montmorillonite
Montmorillonite in which copper has been added by ion exchange has
also been prepared for evaluation as a DDT degradation catalyst.
A portion of the air-dried < 2/•*• fraction of montmorillonite (Ward's No.
25) was reacted repeatedly with cupric chloride. The montmorillonite
was treated with CuCl2 solution at the rate of 3 ml of 1 N CuCl2 so-
lution per g of air-dried clay. If the montmorillonite has an exchange
capacity of 0. 3 meq/g, then the CuCl2 was added in nine-fold excess.
The clay-CuCl2 solution was shaken for 30 min with a wrist-action
shaker, centrifuged, and the CuCl2 solution decanted off. A fresh
portion of CuCl2 was added, the clay re-suspended and shaken for an
additional 30 min. The process was repeated for five 30-min per-
iods, each with a nine-fold excess CuC^- The product was then
washed with distilled water by suspension, and centrifugation, until
the liquid was free of chloride (by silver nitrate precipitation).
The copper montmorillonite was employed in a test in which 10% of
the catalyst was reacted with DDT for 2 hr at 100°C. The analytical
data, which indicate little decomposition of the DDT, follow:
Retention
Component Time, min Reaction 2 hr at 100°C, %
14.8 0.2
DDE 15.6 8.0
17.4 <0.1
18.9 0.5
DDT 21.1 91.4
Silica-Alumina Catalysts
Silica-alumina catalysts are reported to be effective for catalytic
cracking with the catalytically active sites identified as acid centers
18
-------
(Reference 20). A series of these experimental silica-alumina cata-
lysts was obtained from the Houdry Process and Chemical Company.
Reported characteristics of the catalysts tested follow:
Catalyst
o
Surface area, m^/g
Porosity, vol %
Absorption, wt %
Avg. Pore Diameter,
A12O3, wt %
SiO2,wt %
Na2O, wt %
2 CP 13
375-400
60
65
80
12.4
87. 3
<0.25
523 CP 8
180-200
56
55
85
12.4
87.3
<0.25
These catalysts were obtained as small pellets which were ground in
an agate mortar to a fine powder and dried at 110° overnight. The
results of a test in which 10% of each of these catalysts was blended
with DDT and reacted for 2 hr at 100°C gave the following analytical
results:
Component
DDE
DDD
DDT
Retention
Time, min
14.8
15.6
17.4
18. 9
21.1
Reaction 2 hr at 100°C
Product Analysis, % with Catalyst
2 CP 13
0.1
5.7
o'.3
93.8
5Z3CP 8
0.1
3.4
0.5
96.0
These results indicate no significant decomposition of DDT under the
conditions employed.
Commercial Clay Cracking Catalysts
Two commercial clay-type catalysts have been evaluated and have been
found ineffective in promoting degradation of DDT.
One of the materials evaluated was Filtrol type F-13. This material
is an activated clay with reported high acidic properties. The surface
area (BET) is rated at 325 sq m/gm and the acidity is given at 16 mg
KOH/gm. Initial tests with DDT showed no difference from the DDT
control when a mixture was heated for 2 hr at 100°C. The data in a
test using 10% of the as-received clay as a catalyst follow:
Reaction 2 hr at 100°C
Component
DDE
DDD
DDT
Retention Time, min %
12.9
15.1
17.9
20. 7
0.7
1.1
<0.5
98.3
19
-------
On contacting the supplier, an activating treatment of heating to
240°C for 4 hr was suggested. The results of a test in which 10% of
the activated catalyst was used follow:
Retention
Component Time, min Reaction 2 hr at 100°C> %
12.0 <0.5
13.2 <0.5
DDE 15.4 2.0
ODD 18.3 <0.5
DDT 21.1 99.0
The second clay catalyst purported to have a high surface acidity was
supplied by Georgia Kaolin Company. This material, termed Hydrite
UF, was believed to be a kaolinite-type material. Reaction of 10% of
-325 mesh material with DDT follows:
Reaction 2 hr at 100°C
Component
Retention Time, min %
12.5
13.5
14.2
15.7
16.6
18.4
21.0
< .5
< .5
< .5
3.3
< .5
< . 5
96.7
DDMS
DDE
DDD
DDT
Clearly, these materials have promoted no substantial degradation of
DDT.
Acid -Form Exchange Resin
On the basis that strong surface acidity may catalyze DDT decompo-
sition, a reaction of finely ground acid-form Amberlite IR-120 resin
with DDT was attempted. The finely ground material was dried over
Drierite in vacuum before use. When the DDT was heated with 10%
by weight of IR-120 for 2 hr at 100°C, neither a coloration of the mass
nor a weight loss were obtained. The benzene solution was also color-
less. Analysis of the sample showed no substantial degradation:
Retention
Component Time, min Reaction 2 hr at 100°C) %
12.6 <0.1
DDE 15.7 2.1
DDD 18.8 <0.1
DDT 21.3 98.4
On the basis that the lack of catalytic activity might be attributed to
moisture, a comparison was made in further experiments between
mixes prepared from the IR-120 resin dried in an oven at 110°C for
16 hr, and material dried in a vacuum desiccator over Drierite for
20
-------
16 hr. In both cases 10% of the resin was mixed with the recrystallized
DDT and reacted for 2 hr at 100°C.
little decomposition of the DDT.
Component
DDE
DDT
Time, min
12.
14.
15.
17.
18.
4
8
6
4
9
21.1
The analytical results indicate
Reaction 2 hr at 100 C
Product Analysis, % When Catalyst
Oven dried Vacuum desiccator dried
0.
0.
0
0.
6.0
1
4
93.0
<0.1
0.4
7.3
0.2
0.7
93.8
- Adducts
A general consideration of Lewis -acid theory leads one to BF3 and its
adducts, as compounds with high Lewis-acidity (Reference 18, 21). In
particular, the adduct BF3. H3PO4 has been used as a catalyst in some
organic reactions where correlations with Lewis -acidity were noted
(Reference 22). Accordingly, the BF3. H3PC>4 adduct was prepared and
its catalytic activity with DDT determined.
The BF3. HoPC^ (+ BF3 hydrate) was prepared by the method of Axe
(Reference 23). The method consists of the saturation of 85% H3PO4
with BF3, forming the liquid catalyst. In a comparative test, a cata-
lyst consisting of o-dichlorobenzene saturated with BF3 was also em-
ployed. The results of the analyses of the products of DDT reaction
with these catalysts at 25° and 100°C follow. In each case, 1 ml of
catalyst was used with 1 g of DDT.
Analysis, %
C t l t-
_ •> '
Reaction:
Retention
Component Time, min
DDE
DDT
BF
±5.b 3.
o-dichloro- o-dichloro-
benzene benzene
solvent solvent
2 hr; 100° 2 hr; 100U
120 hr;25° 118hr;25° 118 hr;25° 120 hr;25°
14.2
15.6
19.0
21.4
0.1
10.8
«0. 1
89.0
0.1
16.5
«0. 1
83. 3
0.1
10.3
«0. 1
89.7
0.1
9.5
89.3
Clearly, little reaction was shown, with the only significant product being
DDE. This catalyst system therefore holds little promise.
Solvents
Early degradation studies on DDT by Fleck and Haller (Reference 24)
21
-------
indicated that the catalytic action of FeCl3 was promoted by solution
in selcted chlorobenzenes, chloronaphalene, and nitrobenzene, and
inhibited by various hydrocarbon and fatty oils, alcohols, ketones,
etc. The solvent which appeared to give the greatest degradation with
FeCl 3 and DDT was o-dichlorobenzene. Accordingly, experiments
were carried out in order to determine whether this solvent would aid
degradation of DDT by siliceous catalysts, as well as FeCl^. In these
experiments, 1 g of DDT and 1 ml (ca. 1.3 g) of distilled o-dichloro-
benzene were reacted with the given catalysts; the results follow:
Analysis, %
Retention
Time, min
12.2
13.1
14.5
15.6
16.8
18.1
21.0
_
-
13.1
83.2
7.6
-
-
_
0.1
_
15.6
-
0.3
86.6
0.1
0. 1
0.5
32. 1
0.1
0.8
66.5
H
_
_
17.2
_
_
74.2
Catalyst: FeCl3 Protonated Copper Houdry*
montmoril- montmoril- 24CP12
lonite lonite
Catalyst, %; 0.42 13.3 14.6 38.0
Reaction: l_hr, 100°C 2Jhr, 100°C 2 hr, 100°C 2 hr, 100°C
Com-
ponent
DDMU
DDMS
DDE
ODD
DDT
The use of a solvent has increased the extent of reaction obtained,
especially with the siliceous catalysts. However, DDE appears to be
the principal product.
Surface Acidity Correlation
It has been suggested in earlier works (e. g. , Reference 8) that de-
composition of DDT catalyzed by clays could be correlated with the sur
face acidity or Lewis-acid response as shown by Hammett indicators.
Experiments to determine the surface acidity response of some of the
materials investigated were carried out in an effort to determine use-
ful correlations.
The indicators were dried in a vacuum desiccator over Drierite and
were prepared as 0. 1% solutions in benzene dried over fresh
The indicator solutions were stored in a desiccator.
The procedure employed and the indicators employed were essentially
as described by Benesi (Reference 25). An approximately 0. 1 g portion
of the sample was transferred to a 5 ml glass vial and 3 ml of dry
* A silica alumina catalyst having a specific surface of 425-450 m2/g, an
average pore diameter of 70 A, and containing 12.4% A^O^.S?. 3%
SiO2, and 0. 25% Na2O.
22
-------
benzene (dried overnight over fresh Pz0^) added. The indicator solu-
tion was then added and the suspension shaken. The indicators and
their pKa follow:
A. Phenylazonapthylamine -f-4. 0
B. Butter Yellow + 3. 3
C. Benzeneazodiphenylamine +1.5
D. Dicinnamalacetone -3. 0
E. Benzalacetophenone -5.6
F. Benzoylbiphenyl -6. 2
G. Anthraquinone -8. 2
H. Picramide -9. 3
The results obtained with selected samples follow:
Catalyst Indicator Color Indicator Color pKa
Filtrol F13
as received E yellow G colorless -5.6
dried 240°C E yellow G colorless -5.6
Hydrite UF E yellow G colorless -5.6
Acid Montmorillonite E yellow G colorless -5.6
Montmorillonite
air dried A blue violet B yellow +4.0
A1C13, Anhydrous G yellow H - -8.2
A1C13.6H2O A blue violet B yellow +4.0
AlBroAnhydrous G yellow H - -8. 2
The only catalysts tested which were effective for the ambient tempera-
ture degradation were AlClg and AlB-j, and these materials have the
most strongly acid pKa of the materials tested. The sharp decrease in
Lewis acidity comparing anhydrous AlClo with the hydrate (-8.2 vs
+4. 0), and the modest decrease in pKa apparently necessary in order
to effectively stop degradation (catalyst effective at pKa -8. 2, catalysts
at -5. 6 not effective) would show clearly why the absorption of a small
amount of moisture would make the anhydrous metal salts ineffective
as catalysts.
Summary
In summary, the strong Lewis acid catalyst AlClo has shown the ability
to degrade DDT, even at ambient temperatures. Although one product
is DDE, other products in substantial quantities are obtained. Similar
results were obtained with AlBr,, substantially degrading DDT in a
few minutes at ambient temperature. However, the adsorption of small
amounts of moisture appears to seriously decrease the effectiveness
of the catalyst, and the addition of water, a strong Lewis base, to form
the hydrate leads to essentially no degradation of the DDT. Anhydrous
ferric chloride also catalyzes decomposition of DDT, but the reaction
23
-------
appears less extensive at ambient temperatures than is obtained with
AlClo. The clay and modified montmorillonite catalysts have not been
effective in catalyzing DDT decomposition. The use of acid form ex-
change resin and BF3 adducts has also led to ineffective catalysis of
DDT degradation. The use of the solvent o-dichlorobenzene leads to
substantially greater degradation of DDT by the protonated montmori-
llonite, copper montmorillonite, and a commercial alumina-silica
catalyst, but DDE was the principal product.
Reduction
The mildly acidic reduction of DDT by zinc was investigated for its
efficiency in reducing DDT. Highly promising results were obtained
which led to its selection as the technique most suitable for development
as a practical degradation process that might be used for both field and
waste system treatment of DDT.
The initial test was made using an adaptation of the acidic reduction
system used by Romano (Reference 13). In this study, 1 g of DDT was
dissolved in 50 ml of alcohol, and 2 g of (1^4)2804 and 1 g of powdered
zinc dust were added and the reactants held at 50°C. Two samples were
tried, using 96% or 100% alcohol as the solvent. The results show clearly
that substantial reaction occurs in the 96% alcohol, while the 100% alcohol
solution was much less effective. The analytical results from these tests
follow:
Reaction 116 Hours at 50°C
.,, Retention 96% Alcohol Solution 100% Alcohol Solution
Component*^ Time, Min. % %
DDEt 8.0 43.7 5.2
12.4 <0.1 0.1
DDMU 13.4 0.2 0.4
DDMS 14.5 6.8 1.3
DDE 15.8 8.3 10.2
16.9 - 0.8
ODD 18.0 14.1 7.5
DDT 21.0 26.7 75.4
It is important to note in the test with the 96% alcohol that although more
than 73% of the DDT was destroyed, only 8% went to DDE and about 65%
formed degradation products other than DDE.
In a further test, the Romano experiment (Reference 13) was carried out
over a range of reaction times ranging from 1 hour to 8 hours.
In this study, 1 g of DDT was dissolved in 40 ml of n-dodecane (Romano
used kerosene). To this was added 20 ml of 95% ethanol containing 2 g of
zinc dust and 4 g of (NH4)2SO4, and the resultant mix was refluxed at 78°C.
After given times, a 10 ml sample was withdrawn for analysis and 10 ml of
a 2:1 dodecane-ethanol mix added to maintain the volume at the initial level.
* See Glossary for chemical names and formulas of cited compounds.
24
-------
Component
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time, min
7.8
]2, 0
13.2
14.2
15.4
16.3
17.4
17.8
21.0
Analysis, %, after Reaction, hrs, at 78 C
1
72.6
0,1
0.7
6.2
1.1
0.7
M
18.5
-
2
74.3
<0.1
0.7
6.5
-
<0. 1
_
18.3
-
4
81.9
<0.2
0.5
7.5
-
<0.2
0.2
9.9
-
8
81.3
<0.2
0.7
11.2
-
<0.2
0.7
6.1
-
Several significant results were obtained from this series of experiments.
It is noteworthy that complete destruction of the DDT was found over the
complete time range examined, and that DDE was not a product of the
degradation (other than the 1.1% found in the 1-hour sample). The sig-
nificant product was identified subsequently as DDEt, a product from which
all 3 aliphatic chlorines have been removed. It is to be noted that this
component increases with prolonged reaction.
It would appear that a reduction of DDT should proceed through DDD
(the dichloroethane equivalent of DDT) and DDMS (the rnonochloroethane
derivitive), at least as transient species.
It should be noted that the amount of DDD decreased with continued reaction
ranging from 18. 5% after 1 hr to 6. 1% after 8 hrs. The DDMS increased
from 6. 2 to 11. 2% and the DDEt from 72. 6 to 81. 3% in the same period.
An examination of the literature pointed out another type of zinc reduction
which was investigated. Hornstein (Reference 12) used a zinc column
in which selected chlorinated pesticides in acetone-dilute acetic acid so-
lution were completely or partially reduced at ambient temperatures.
The technique was described as an analytical method for certain chlorinated
pesticides.
It was not known, however, whether the zinc reaction could be effec-
tively carried out with a smaller ratio of reductant to DDT than the over-
whelming excess to be found in a column. A test was therefore made in
which 1 g of DDT was reacted with 1 g of zinc dust. The DDT was dis-
solved in 20 ml of acetone and 10 ml of 10% acetic acid was added to
provide the acidity. This ratio of zinc to DDT provides a 10% excess
for reaction to remove all chlorines, and assuming no reaction with the
acid. The mixture was reacted for 3 hours at ambient temperature,
filtered and analyzed to give the following data:
25
-------
Reaction 3 Hours at 25 C
Retention Time, min %
6.0
8.0
10.3
12.4
13.6
14.5
15.8
18.0
21.0
1.0
20.8
0.4
0.2
3.2
10.2
0.2
37.0
6.1
Component
DDEt
DDMU
DBMS
DDE
DDD
DDT
These data show that essentially all of the DDT has been consumed,
and that DDE was not a significant product. The product with a re-
tention time of 8.0 min, DDEt, appears prominently, as well as DDD.
The promising results of this study were confirmed in other tests;
the results of these tests are conveniently grouped in a later section
where the development of the mildly acidic reduction of DDT is described
at length.
In summary, reduction of DDT with zinc under mildly acidic conditions
has given complete or near complete degradation of DDT without forming
DDE as a product. The reaction was found to proceed effectively at 25°C
in periods of the order of a few hours, yielding a product DDEt (bis
(p-chlorophenly)-ethane) which appears, on the basis of published informa-
tion to be described in a later section of this document, to be "void of the
neurotoxic effects of DDT. " The reaction employs commonly available
materials and the method appears to be economically feasible. The small
amount of zinc employed in the reduction may not be deleterious to practi-
cal use in the field or in waste treatment of DDT-laden waters. Hence
this process was selected for further investigation and development.
Free-Radical Catalysis
Selected free-radical catalysts were investigated for their efficacy in
decomposing DDT to preferred end products.
Benzoyl Peroxide
In an initial test, benzoyl peroxide was employed. Finely powdered
benzovl peroxide (10%) and DDT were blended by gentle stirring and heated
at 100 C. After about 5 min reaction, the mass melted to form a yellow
colored solution. The analysis after 2 hr reaction was as follows:
Reaction 2 Hour at 100°C
Component
DDE
DDT
Retention Time, Min. %
15.5
20.4
25.6
29.4
30. 3
36.1
94.1
1.3
1.4
<0.5
<0.5
1.8
26
-------
Thus, almost complete decomposition of the DDT occurred, although
the degradation was mainly to DDE.
Since the benzoyl peroxide appeared to rapidly catalyze the decomposition
of DDT at 100°C, an attempt was made at decomposing DDT at 50°C with this
material. In a test in which 10% of the catalyst was employed, the follow-
ing analytical data were obtained:
Reaction 116 Hours at 50 C
Component Retention Time, Min. %
1.4 0.2
4,0 0.2
DDE 15.8 4.1
18.8 0.4
DDT 21.0 92.7
36.4 0.8
41.0 1.5
Substantial decomposition at 50 C was not obtained, although the pre-
viously reported decomposition in 2 hours at 100 C was confirmed in
another experiment.
Potassium Persulfate
The observation that benzoyl peroxide appeared to catalyze decomposition
of DDT to (mainly) DDE suggested the possibility that the decomposition
may have been induced by the peroxide function. As a check of this
possibility, a sample was run in which DDT was reacted for 2 hours at
100 C with 10% potassium persulfate. Little or no reaction appeared to
have taken place.
Reaction 2 Hours at 100 C
Component Retention Time, Min %
DDE 15.2 3.9
DDT 20.7 96.1
Azobis Isobutyronitrile
The action of free-radical catalysts was further explored in a test using
2,2' azobis (2-methylpropionitrile). This material was of special interest
because (1) the catalyst generally functions at lower temperatures than
benzoyl peroxide and (2) the catalyst is not a peroxide but a nitrogen-
forming system. Tests were run in which DDT was reacted with 10% of
the azobis catalyst at 100 and at 50 C. No substantial decomposition
was shown in either case. The analytical data follow:
Reaction Conditions
Component 2 Hours at 100°C 24 Hours at 50°C
DDE 1.4 1.4
DDT 98.6 98.6
27
-------
Redox System
An experiment was also carried out in which the redox system commonly
used as a free-radical catalysis system for near ambient temperature
polymerization was employed. The catalyst system used was basically
that given by Marvel (Reference 26).
In this test, 1 g of DDT was dissolved in 10 ml of benzene and added to a
solution in which 5 g of Triton X-100 surfactant, 0.5 g benzoyl peroxide,
1.25 g ferrous ammonium sulfate hexahydrate and 1.1 g of potassium
pyrophosphate were dissolved in 100 ml of water. The mixture emulsified
readily. The mixture was allowed to react for 1 week at 25 C, with fre-
quent shaking. After that time, the DDT and degradation products were
extracted repeatedly with benzene and analyzed by gas chromatography.
The analyses, which show almost complete destruction of the DDT, has
given DDE as a major product, but substantial degradation to other
products (/-N"'30%) is also shown. The results follow:
Reaction 168 Hours at 25 C
Component Retention Time, Min ~%
1.0 1.3
1.3 0.4
1.4 0.4
2.3 «0.1
2.5 <0.1
3.4 0.3
3.6 2.9
8.4 1.5
11.8 0.3
13.4 15.1
DDE 15.6 61.0
18.2 4.2
DDT 21.0 11.9
30.0 0.6
31.0 0.4
37.0 0.2
In summary, free-radical catalysis has not shown as extensive degra-
dation of DDT as some other systems. The peroxide catalyst examined
has catalyzed decomposition only to DDE at 100°C, and was substantially
unreactive at 50°C. The non-peroxide free-radical catalyst, azobis iso-
butyronitrile, was ineffective at both 50°C and lOO^C, as was the inorganic
peroxide salt potassium per sulfate. However, the initial test with the
ambient-temperature redox system shows some promise in that 88% of
the DDT was destroyed with 27% being found in degradation products
other than DDE.
Alkaline Hydrolysis
It is reported in the literature that the reaction of DDT with ethanolic
KOH (ambient or reflux) yields DDE as a product, yet refluxing with
28
-------
alkaline-ethylene glycol gives di(p-chlorophenyl)acetic acid, DDA
(Reference 27). A series of experiments were carried out to further
establish the extent to which alkaline hydrolysis reactions would take
place. In these tests, ethylene glycol, n-butanol, and ethanol were
made 1 N in KOH and refluxed with DDT. Samples were withdrawn for
analysis after 1, 2, 4, and 8 hours and subjected to gas chromatographic
analysis. The reflux temperatures were respectively 168 to 175°C,
117°C, and 78° C.
The results when ethylene glycol is the solvent follow:
Analysis, %, after Reaction, Hrs,
Retention at 168 to 1 75°C
Component Time, Min
6.6
8.4
DBF 9.4
DDMU 13.4
DDE 15.6
DDT 21.0 -
These results show several interesting factors. The DDT has been com-
pletely consumed in all of the experiments and the DDE was gradually re-
acted so that it too was nearly consumed after 8 hour reaction. A new,
unidentified peak with a retention time of 6. 6 min was shown and the build-
up of this peak was nearly proportional to the reaction time, after an ap-
proximately half-hour induction period. This peak cannot be quantitated
until it is isolated and a calibration curve determined; the results shown
are on the basis of the DDT calibration curve. The data are shown only
to demonstrate that the peak builds up in a near-linear manner with in-
creased reaction time. The balance of products shown by gas chroma-
tographic analysis falls far short of 100%, 65% of the products after 1
hour reaction not being accounted for. This presumeably represents
production of DDA, or a similar product which does not respond to the gas
chromato graph.
Reduction of the reflux temperature to 117 by using n-butanol as the
solvent yielded the following results:
1
(2.4)
0.2
0.1
0.1
32.2
2
(18.7)
0.8
21.8
4
(57.1)
2. 7
8
(90.4)
0.5
29
-------
Component
DDMU
DDE
DDT
Analysis, %, after Reaction, Hrs,
Retention j^l17 c in KOH-n-butanol
Time, Min
175
2.4
3.6
4.8
7.0
8.7
11.7
12.8
13.5
15.6
18.5
21.0
23.1
24.0
28.5
29.4
36.0
37.3
38.2
39.7
The DDT was consumed in all of the experiments and it appears that the
DDE formed is being gradually removed. Unidentified products with re-
tention times of 24. 0 and 29. 4 min appear to be increasing with continued
reaction time. Many trace quantities products were also shown. The
balance of products indicates that up to 20% of a material which does not
give a gas chromatographic response was also present; this product may
be DDA.
The results of a similar experiment in which DDT was refluxed with IN
KOH in ethanol can also be examined.
1
TCT
0.3
0.3
0.1
0.3
4.8
1.3
0.4
1.0
63.9
0.4
<0.1
12.8
0.1
4.6
<0. 1
<0. 1
<0. 1
<0. 1
2
37?
0.3
0.3
0.2
0.2
3.0
2.7
0.3
1.1
57.3
0.2
<0.2
10.8
<0.2
3.3
<0.2
<0.2
<0.2
<0.2
4
072-
0.2
0.2
0.2
0.2
2.7
3.1
0.4
1.2
47.0
0.2
<0.2
23.5
0.2
7.6
<0.2
<0.2
<0.2
<0.2
8
U72-
0.2
0.5
0.2
0.2
1.7
2.7
0.2
0.5
41.1
0.2
0.2
25.0
0.2
12.7
0.2
0.7
0.2
0.2
Component
DDMU
DDE
DDD
DDT
Retention
Time, Min 1
8.0 0.2
9.2 0.1
11.3 3.0
13.1 5.2
15.6 83.8
16.8 0.4
17.8 2.9
18.4 0.1
21.2
Analysis, %, after Reaction, Hrs,
at 78°C in KOH-Ethanol
8
0.6
1.0
6.4
13.9
59.0
3.2
15.3
0.7
0.4
0.2
2.5
3.8
91.2
0.2
1.7
0.2
0.2
2.2
3.3
93.3
1.2
Although the results are scattered, the principal product is DDE, as
expected, although minor or trace quantities of a variety of other products
were obtained also.
30
-------
In summary, it is clear that DDT may be simply dehydrochlorinated to
the dichloroethylene derivative DDE but the further transformation of
this species to a product expected to be harmless to the environment
appears to require extremely drastic conditions. Alkaline hydrolysis
appears to offer little promise as a practical means for degrading DDT
to a product compatible with environmental requirements.
Oxidation
The oxidation of DDT is another means of destruction of this pesticide
that deserves examination. Two general approaches have been considered.
In one, an oxidation of the DDT molecule was attempted with an acid-CrC>3
system. In the second system, an alkaline oxidation was considered on
the basis that the alkaline condition would dehydrochlorinate the DDT to
DDE, and the ethylenic structure thus formed would be susceptible to
oxidation, possibly to the soluble acetic acid derivative, DDA.
CrOo-Acetic Acid
The oxidation of DDT and DDE by CrO^-acetic acid was reported by
Grummitt, Buck and Jenkins (Reference 28), who reported "no identified
products" from DDT oxidation, and 4, 4' -dichlorobenzophenone (DBP) as
a product of DDE oxidation. In the experiment which was carried out,
2g of DDT were refluxed (117 to 120°C) in 50 ml of glacial acetic acid
containing 1. 6 g of CrO.,. A 10 ml sample was withdrawn after 1, 2, 4
and 8 hour reflux, with 10 ml of glacial acetic acid being added to the re-
flux mixture to maintain a constant volume. The mix turned a dark green
color within one hour and it appears that the CrO, was consumed in this
period. The analytical results follow:
Retention Analysis, %, after Reaction, Hr, at 117-120 C
Component Time, Min 1248
1.4 0.1 0.1 0.2 0.7
2.5 1.8 1.3 1.6 1.5
DBP 10.3 0.4 0.3 0.3 0.1
15.0 0.1 0.1 0.1 <0.1
DDE 15.8 6.9 4.7 6.9 4.6
18.8 0.7 0.2 0.5 0.1
DDT 21.0 61.7 54.1 64.6 59.7
Material un-
accounted for, % 28.3 39.2 25.8 33. 3
Although the results show scatter, it is clear that at least half of the DDT
was not consumed under the rigorous oxidation conditions employed. A
substantial amount of material(26 to 39%) was unaccounted for in the gas
chromatographic analysis. It is considered likely that the 26 to 39% of
material not shown in the analyses represents products such as DDA or
p-chlorobenzoic acid, neither of which will respond to conventional gas
chromatography unless derivatives are formed. No attempt was made to
further identify the products since a substantial amount of the DDT was
unreacted under extremely rigorous oxidation conditions - conditions much
more severe than might be used for a practical field destruction process
of DDT degradation.
31
-------
Alkaline KMnO4
Attempts have been made to oxidize DDT with alkaline KMnO4. In the
initial experiment, 1 g of DDT was dissolved in 45 ml of acetone and 1 g
of KMnO4 and 5 ml ION aq. KOH were added. An immediate reaction
leading to the production of a voluminous brown precipitate of MnO2 was
observed. However, analysis of the solution showed DDE as the only
pesticide product and a blank reaction yielded a similar MnO2 precipitate
when the alkaline KMnO. was reacted with acetone.
Similar results were obtained when dioxan and tetrahydrofuran were ex-
amined as solvents for the reaction.
The reaction of DDT with KMn©4 and pyridine was attempted also. The
pyridine was refluxed with KMnO4 to remove impurities, and then dis-
tilled before use. The experimental conditions were as follows:
a. 1 g DDE + 1 g KMnO4 +10 ml pyridine
reacted 67 hr at 25°C.
b. 1 g DDT + 1 g KMnO4 + 10 ml pyridine
reacted 69 hr at 25°C.
c. 1 g DDT + 1 g KMnO4 + 1 ml 10 N KOH + 10 ml pyridine
reacted 71 hr at 25°C.
The data for these experiments follows:
Analysis, %
(a)DDE, (b)DDT, (c)DDT,
Com- Retention KMnO4 KMnO4 alkKMnO4
ponent Time, Min pyr. pyr. pyr.
DBF 9.5 6.9 - 6.9
12.2 - <0.1
DDMU 13.1 - 1.3
DDE 15.6 96.4 8.6 79.0
DDD 18.1 - 0.2
DDT 21.0 - 80.3
The results indicate little hope for a successful oxidative degradation of
DDT.
TOXICOLOGY OF DDT DEGRADATION PRODUCTS
With the development of bis(p-chlorophenyl) ethane as a probable product
of the reductive degradation of DDT, information has been sought on the
toxicology of this material.
Van Oettingen (Reference 29) states that "2, 2-bis(p-chlorophenyl) ethane
is void of the neurotoxic effects of DDT. " The LD5Q for rats (oral
administration) was 1000 mg/kg (Reference 30). Comparative acute
toxicity values (LDso) were 150 mg/kg for DDT.
32
-------
Larson, et al (Reference 31), investigated the production of adrenal
cortical atrophy in dogs on administration of DDD and derivatives. One
dog was tested with bis(p-chlorophenyl)ethane. In this case, the cortical
atrophy was not noted, and moderate hyperplasia was observed. The dog
survived 5 weeks on a dose of 0.22 g/kg of the bis(p-chlorophenyl)ethane;
it cannot be determined whether the test was terminated at this time or
the dog succumbed. The necropsy indicated jaundiced tissues, liver
necrosis and bile necrosi s of the kidney. It should be noted the test was
made on one mongrel dog so that any conclusions would be tenuous.
In another test by Cobey, et al, the administration of 200 mg/kg of
bis (p-chlorophenyl) ethane to a dog daily for 4 days produced no changes
in the plasma corticoid level (Reference 32).
In summary, Smith, et al (Reference 30) , indicates that the neurotoxic
and hepatotoxic effects of DDT are dependent upon the 5 halogens in the
molecule and that compounds with aromatic or aliphatic chlorines alone
exhibit little toxicity and none of the DDT central nervous system effects;
all aliphatic chlorines have been removed from bis(p-chlorophenyl)ethane.
In addition, it should be noted (e.g. Reference 17) that bis(p-chlorophenyl)
ethane presumably occurs in the mammalian metabolic route leading
eventually to excretion of the soluble DDA.
Metcalf (Reference 33) reports that bis(p-chlorophenyl)ethane, DDEt, is
< 0.001 to 0.06 as toxic as DDT to insects. However, the material is
an effective acaricide. The monochloroethane derivative DDMS (2,2-
bis(p-chlorophenyl)-1-chloroethane) reportedly is an effective toxicant
to the blowfly Calliphora vomitoria, about 0.02 as toxic as DDT to the
mosquito, A. quadrimaculatus, and about 0.2 as toxic as DDT to the mouse.
33
-------
SECTION V
DEGRADATION OF DDT BY METALS
The initial promise that was shown by the DDT degradation technique
of mildly acidic reduction by zinc powder led to a more complete exa-
mination of this reaction, as well as tests with other materials having
similar reducing power.
DDT DEGRADATION BY ZINC
A series of tests were carried out in an effort to characterize the zinc
reduction and determine means for improving the reaction. The basic
test involved the solution of 1 g of DDT in 20 ml acetone, the addition
of 1 g of zinc powder, and acidification with 10 ml of 10% acetic acid,
giving a final acidity of 0. 5 N.
Rate of Zinc-Acetic Acid Reduction of DDT
An experiment was carried out to determine the effect of time on the
reaction. Time intervals from 1/4 hour to 27 hours at 25°C were
employed. The analytical results follow:
Com- Retention Analysis, %, after Reaction, hrs, at 25 C
ponent Time, min 1/4 1 2 3 27
3. 1 0. 1
6.6 1.1 1.0 1.0 0.8 1.2
DDEt 7.8 20.0 18.5 20.3 24.5 20.0
9.8 1.4 0.8 0.8 0.8 0.7
11.8 0. 1 0. 1 0. 1 0. 1 0. 1
12.4 0. 1 0. 1 0. 2 0.4 0. 2
DDMU 13.0 18.8 13.6 15.5 20.0 16.2
DDMS 14.2 7.9 7.5 9.8 10.0 16.8
DDE 15.6 11.2 5.9 2.5 2.3
ODD 18.0 16.2 23.2 21.0 19.9 17.3
DDT 21. 0 7. 7 6. 5 2. 1 1.4
These results show that substantially all of the DDT has been reduced
within the first 15 min, and that the small amount of DDE which appears
in the initial sample is soon consumed; DDD is formed early in the re-
action but tends to be reduced to DDMS.
Tests were made in which reaction times as long as 28 days were in-
vestigated. In each case the reaction of 1 g of DDT with 1 g of tech-
nical grade zinc dust in the dilute acetic acid-acetone medium was
used.
35
-------
Corn- Retention Analysis, %, after Reaction, hrs, at 25°C
ponent Time, min 24 48 97 170 340 504 673
7.0 0.2 0.5 0. 4 <0. 2 0.2 - 0.3
DDEt 7.8 30.2 28.1 31.4 33.8 35.7 35.6 38.2
10.2
12.0
12.4
13.0
14. 0
-
<0. 2
-
5.7
21. 2
-
<0. 2
-
6.7
28.8
-
0.2
-
5.5
35. 1
_
<0. 2
-
4.7
37.3
-
<0. 2
-
5.4
41.8
_
-
0.2
4.9
46.7
0. 5
0. 1
0.3
4. 1
43.4
DDMU
DDMS
DDD 17.8 42.5 36.0 27.3 24.0 16.4 12.5 13.0
DDT 21. 0
These results show that the DDD that appears to be formed in the early
stages of the reaction is slowly consumed during continued reaction,
with an equivalent buildup of the concentration of DDEt, the mono-
chloroethane derivative of DDT, DDMS, and possibly 4, 4f-dichloro-
stilbene (which occurs at approximately the same place in the gas
chromatogram). A small amount of material with a 13 min gas
chromatographic retention time which appears to be slowly consumed
is shown also; this material is probably the chloroethylene derivative,
DDMU.
Effect of Increased Temperature on Zinc-Acetic Acid Reduction of DDT
The effect of increased temperature on the rate of reaction was of in-
terest, since a slight increase in temperature may yield somewhat
increased reduction of the DDT. A series of tests in which the extent
of reaction was to be measured after 1, 4, 7, 14, 21 and 28 days at
40°C was therefore initiated. This temperature was chosen as a con-
servative simulation of summertime soil conditions in Southern U.S.
fields; Bowman, Schechter and Carter used a 45°C temperature in
persistence tests as the highest temperature to which Georgia soils
were likely to be subjected (Ref. 34). In these tests 1 g of DDT was
reacted with 1 g of zinc dust in 10 ml of 10% acetic acid and 20 ml
of acetone. The results follow:
Com- Retention Analysis, %, after Reaction, hrs, at 40 C
ponent Time, min 24 48 96 168 333 502 673
7. 0 0. 2 0.2 0. 3 0. 7 0. 9 0. 3 0.3
DDEt 7.8 31.1 36.0 38.3 37.5 37.5 39.3 39.6
10. 5
12.0
12.4
13.0
14.0
0.4
0. 1
0.5
5. 1
40.6
0.3
0. 1
0. 1
5.1
51.4
-
0. 1
-
4.6
55.8
0.3
0. 1
0.4
4.9
55.8
0.4
0. 1
0.5
5. 1
55.5
0.5
0.1
0.7
4.5
54.5
0. 6
0. 1
0.9
5.3
53. 0
DDMU
DDMS
DDD 17.8 22.0 6.9 0.8 0.3 - 0.2 0.1
DDT 21.0
36
-------
The major effect of higher reaction temperature appears to be the more
rapid and complete reduction of DDD to DDMS.
Effect of Concentration of Zinc on DDT Reduction
The screening tests have used 1 g of zinc to reduce 1 g of DDT. It was
of interest to vary the ratio of zinc to DDT and determine the effect on
the reaction. Tests have subsequently been made in which 1 g, 0. 5 g,
0. 25 g and 0.1 g of CP zinc dust were reacted with 1 g of DDT in the di-
lute acetic acid-acetone medium; the materials were reacted for 2 days
at 25°C.
The normal appearance of the reaction is that a voluminous precipitate
of DDT appears immediately upon mixing, but that the precipitate dis-
appears after about 15 min reaction, when the DDT appears to have been
essentially consumed. In this test, samples with Ig and 0. 5 g Zn led to
dissolution of the DDT after 15 min mixing, and the sample containing
0. 25 g Zn resulted in nearly complete solution of the DDT in 15 min and
complete solution in 24 hr. The sample with 0. 1 g of Zn did not appear
to yield complete solution of the DDT. The analyses of these samples
follow:
Analyses, %, after 48 hr Reaction at 25 C
Com- Retention g Zinc dust reductant/g DDT
ponent Time, min 1. 00 0. 50 0. 25 0. 10
DDEt 7.8 35.1 28.5 13.5 6.8
11.0 0.1 0.2 0.3
12. 0 0. 3 0. 2 0. 1 0. 2
DDMU 13.0 4.4 4.3 2.4 1.3
DDMS 14.0 20.6 15.2 5.6 1.6
DDE 15.6 - - 1.7 3.8
DDD 17.8 39.4 51.7 46.7 18.4
DDT 21.0 - - 29.8 67.8
These results show clearly that a reduced amount of zinc results in a less
complete reduction of the DDT. Indeed, the equal weight ratio resulted
in the highest concentration of DDEt product, as well as a somewhat re-
duced amount of DDD and an increased concentration of DDMS and/or
4, 4'-dichlorostilbene. An examination of the stoichiometry of the re-
action of DDT and zinc reveals that 0. 276 g of zinc would be consumed
in reducing 1 g of DDT to the product DDEt. However, these results
suggest that an excess of zinc may be required for effective reaction.
It should be noted that unconsumed zinc was found in all samples -
including the one in which 0. 1 g of zinc was used per g of DDT.
A test was also carried out in which 0. 1 g of granular CP zinc was used
per gram of DDT. The results were in reasonable agreement with those
tabulated above, with 72. 6% of the DDT remaining, 10. 1% being present
as DDD and 11. 8% as DDEt.
37
-------
Effect of Acidity on Zinc Reduction of DDT
The screening tests have shown that DDT may be reduced by zinc in the
presence of either 10% acetic acid, or (NH^^SC^ with 95% ethanbl. The
former reaction has generally been studied at 25° while the latter tests
(Romano reaction) were generally carried out at reflux temperature
(78°C). Accordingly, tests were carried out to determine the effect of
acidity on the extent of DDT reduction by zinc, in an effort to establish
suitable reaction conditions.
In the first series of tests, the zinc-acetic acid-acetone system was
examined. In each test, 1 g of DDT, 1 g of zinc dust, and 20 ml acetone
were reacted with 10 ml of aqueous acetic acid of varying strength. The
results are given in terms of the acidity of the final reaction mixture;
the reactions were all carried out for 96 hrs at 25°C. The analyses
follow:
Analysis, %, after Reaction for 96 hrs
at 25°C as a Function of Acetic Acid
Com- Retention Normality of Reaction Mixture
ponent Time, min 5 N 1 N . 25 N . 05 N . 005 N
4. 0 - - 0. 1 0. 1 0. 1
6.8 - 0. 2 0. 1 0. 3 0. 2
DDEt 7.8 63.2 32.5 31.1 32.1 45.9
10. 2 0. 1 0. 1 0.4 0. 1
12.0 0.1 0.1 0.1 0.1 0.1
DDMU 12. 8 2. 7 4. 6 7. 6 8. 3 3.5
DDMS 14.0 15.6 37.3 31.8 20.7 14.7
ODD 17.8 14.0 24.9 28.5 38.3 35.6
DDT 21. 0 -
These results show the greatest conversion of DDT to the ethane de-
rivative, DDEt, at the extremes of acidity employed. It is particularly
noteworthy that the extensive conversion of DDT to DDEt achieved with
the 5 N acidity also showed minimal DDD and presumably the mono-
chloroethane derivative, DDMS. The low-acidity extreme also showed
a high conversion of DDT to DDEt, but the residual DDD was also high;
the visual appearance and slow solubility of the flocculent precipitate
on the initiation of the reaction also indicated a slower reaction with
the 0. 005 N sample. However, both extremes appeared to give a more
extensive reaction than samples more nearly equivalent to the 0. 5 N
medium normally employed.
A sample was also examined in which the medium was 0. 5 N in acetic
acid but to which 0. 2 g of the surface active agent Triton X-100 was
added. The surfactant appeared to have no substantial effect on the
reaction.
38
-------
Retention Analysis, %, after Reaction
Component Time, rnin for 96 hrs at 25°C
6. 8 0.2
DDEt 7.8 32.7
10.2 0.3
12. 0 0. 1
12.4 0.1
DDMU 12.8 6.1
DBMS 14.0 36.6
ODD 17.8 23.9
DDT 21.0
In view of the suggested possibility that the reduction of DDT in the field
might be carried out using acidity developed by soil sulfur (Section IX),
tests were carried out in which the acidity for the reaction was provided
by sulfuric and sulfurous acids. The test with sulfuric acid was con-
ducted using 10 ml of 1. 5 N H^SO.^ in place of the 1. 5 N acetic acid
normally employed. The sulfurous acid was prepared by bubbling SC>2
into water; the solution assayed 2. 0 N in sulfurous acid. The results
of the analyses follow; the acidity indicated is that of the final reaction
mix:
Analysis, %, after Reaction
Retention for 24 hr at 25°C
Component Time, min 0. 5N in H?SO4 0. 7N in H2SO3
DDEt 7.8 39.4 12.2
12.0 0.3 0.2
DDMU 13.0 4.9 3.4
DDMS 14. 0 14. 2
14.8 - 1.0
DDE 15.6 - 4.1
DDD 17.8 41.2 45.6
DDT 21.0 - 33.3
These results indicate substantially greater reaction in the presence
of sulfuric acid. The reaction in the presence of the H^SO^. or an
equivalent amount of acetic acid appears approximately the same.
The reduction of DDT by zinc has been achieved in a medium of re-
fluxing 95% ethanol in which the acidity was supplied by the slightly
acid salt (NH^^SO^.. A series of tests were carried out in which this
reaction was examined at 25° (rather than the reflux temperature of
78°C) and in which the salts (NH4)2SO4, NH4NO3 and NH4C1 were
compared. In these tests, 1 g of DDT and 1 g of zinc powder were
reacted with 2 g of the ammonium salt in 50 ml of 95% ethanol. The
samples were allowed to settle and probe samples (1 microliter)
were withdrawn for analysis periodically. The results of the tests
with (NH ) SO were as follows:
39
-------
Com-
ponent
DDEt
DDMU
DDE
ODD
DDT
When the
Com-
ponent
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time, min
7.8
12.0
13.0
14.5
15.6
17.8
21.0
Analysis
71
1.2
0.2
0.4
0. 2
10. 7
2.3
84.9
salt NH.NO was used,
Retention
Time, min
7.8
10. 5
12. 0
13.0
14.0
14.4
15.6
16.0
17.8
21. 0
The results with the salt
Com-
ponent
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time, min
4.0
7.8
10. 0
12.0
12.5
13.0
14. 0
15.6
16.0
17.8
21.0
Analysis
75
0. 8
-
-
1. 1
-
-
3.0
-
10.4
84.6
, %, after
144
5. 2
-
0.5
0. 1
6.5
6.6
81. 1
Reaction,
334
6.2
-
1.4
0.3
10.8
7.2
74. 1
the results were as
, %, after
172
1. 1
0. 1
0. 1
2.8
-
-
1.8
-
12.3
81.8
Reaction,
334
1.0
0.4
-
1.7
0. 1
-
4.0
-
13.4
79.4
hrs, at 25 C
593
6. 1
-
4.6
0. 2
5.5
6.4
77. 2
follows:
hrs, at 25 C
526
0.9
0.7
-
0.3
0. 2
0. 1
0.7
0. 1
14. 0
82. 6
NH4C1 follow :
Analysis
75
25.3
0.4
0. 1
-
2. 1
7.7
0.3
0.7
52. 1
11.4
, %, after
172
34.8
0.4
0. 1
_
1.6
8.4
0. 1
0. 6
47.6
6.4
Reaction,
334
.
32.5
0. 6
0. 1
0. 1
1.8
8.8
0. 1
0.7
49.8
5.5
hrs, at 25 C
527
0. 1
34.4
0.6
0. 1
0. 1
1.8
8.6
0. 2
0.5
48.2
5.6
These results show a substantial 25 degradation of DDT when the
acidity is provided by NH^Cl, although the reaction is not nearly as
rapid as that observed at ambient temperature in the presence of dilute
acetic or sulfuric acids. Reduction in the presence of (NH4)2SO4 and
NH4NC>3 is much slower and does not appear to proceed to a useful
extent of reaction.
40
-------
In a further test of the effect of the pH of the reaction mix on the extent
of reaction, a test was conducted with a basic medium. In this test 1 g
of DDT was reacted with 1 g zinc dust in 20 ml acetone plus 10 ml of
water containing 1 g of sodium hydroxide (reaction mix 0. 8 N in NaOH).
The results follow:
Retention Analysis, %, after Reaction
Component Time, min for 72 hr at 25°C
DDEt 7.8 4. 9
DDMU 13.0 71.6
DDE 15.6 23.5
DDD 17.8
DDT 21.0
The basic reaction was interesting in that the DDT was entirely consumed
without forming DDD. A quantity of DDE was observed, as might be ex-
pected in a basic reaction, but the major product (72%) appears to be
DDMU, the monochloroethylene derivative of DDT. About 5% of the DDEt
was also observed.
Effect of Particle Size and Quality of Zinc
The effect of both the particle size of zinc and the quality of the material
was investigated in some tests in which the efficacy of DDT reduction
was compared using technical grade and CP grade dust, and CP grade
granular material. In each test, 1 g of DDT was reacted with 1 g of
zinc, 10 ml of 10% acetic acid and 20 ml of acetone. The results follow:
Analysis, % after 46 hr Reaction at 25 C
CP CP CP Tech.
Zinc Product: granular granular dust dust
Conn- Retention
ponent Time, min
DDEt 7.8 45.0 41.6 35.1 31.1
11. 0 - 0. 1 0. 1
12.0 0.1 0.1 0.3 0.2
DDMU 13.0 2.7 2.6 4.4 4.4
DDMS 14. 0 5. 5 5. 6 20. 6 37. 2
DDE 15.6 0.5 0.4
DDD 17.8 45.0 45.3 39.4 27.1
DDT 21.0 1.2 4.4
No highly significant trends were shown by these tests. Although the
granular zinc produced the largest amount of the DDEt product, this
material also yields an undesirably large amount of DDD as a product.
The largest amount of material with a 14 min gas chromatographic
41
-------
retention time (presumably DDMS and 4, 4'-dichlorostilbene) was pro-
duced by the zinc dust reductant, and indeed the technical grade dust
was more efficient in producing this product than the CP grade zinc
dust.
Zn Reduction of Technical DDT
Although substantial reduction of pure p, p1 -DDT has been shown by Zn in
the dilute acetic acid-acetone solvent system, it remained to be estab-
lished that similar results would be obtained with commercial-grade
DDT. Three samples were examined and in each case, complete de-
struction of the p,p'-DDT was shown, with a major amount of material
being the bis(p-chlorophenyl) ethane. Another major peak appears to
be p, p'-DDD with possibly some o, p'-DDT (an important impurity in
technical DDT); additional analyses would be required to differentiate
between these two materials which elute from the chromatographic
column at essentially the same time. However, it is believed the peak
probably represents p, p'-DDD since it is present in larger quantities
than the o, p'-DDT in commercial DDT (generally ~ 20% o, p'-DDT).
Analysis, %, after Reaction
for 24 hr at 25°C
Montrose Diamond Eastman
DDT Source: Chemical Shamrock Organic Chems.
Retention
Component Time, min
1.3 <0. 1 <0. 1 0.9
1.6 <0. 1 <0. 1 1.1
(1, 1-diphenylethane) 2.0 <0. 1
5.9 <0. 1 <0. 1
o, p'-DDEt(?) 6.6 6.0 7.1 5.2
p,p'-DDET 7.6 26.2 23.5 34.4
11.3 <0. 1 0.7
12.4 1.3 3.1 1.3
DDMU 13.1 4.2 4.2 3.1
DDMS 14.2 12.0 12.5 7.4
p,p'-DDE 15.6 11.0 11.3 8.7
p, p'-DDD + o, p'-DDT 17.9 29.3 37.7 38.0
p,p'-DDT 21.0 0.1
Reduction of Commercial DDT Emulsion
Tests were made to determine the effect of the additives used in com-
mercial spray formulations on the reduction of DDT by mildly acid
zinc. In the initial test, the reduction of a 25% emulsifiable concentrate
42
-------
of DDT" , to which an equivalent weight of heavy mineral oil had been
added**, was attempted. This formulation was chosen as a simulant
of spray formulations. In the first test, 4 g of the 25% DDT emulsion
and 4 g of the mineral oil were reacted with 1 g of zinc dust and 10 ml
of 10% acetic acid. The reaction was carried out for 24 hr at 25°C.
The results of the analysis of this sample indicated partial reduction
of the DDT. Visual observation of the reaction indicated the DDT was
held in the oil phase and appeared not to be effectively contacted by the
zinc-aqueous acetic acid. A modification of the system to allow more
effective mixing of the reactants was expected to provide essentially
complete reaction. The analysis of the reaction products follows:
Retention Analysis, %, after
Component Time, min 24 hr at 25°C
o,p'-DDEt - ? 6.8 2. 9
p,p'-DDEt 7.8 10.8
12.4 0.1
DDMU 13. 0 0. 5
DDMS 14. 0 0. 7
p,p'-DDE 15.6 4.4
p,p'-DDD + o, p'-DDT 17.8 17.6
p,p'-DDT 21.0 63.1
Additional tests are described in Section VIII of this report covering the
reduction of DDT in water.
METAL REDUCTANTS OTHER THAN ZINC
Additional experiments were performed in which metals with similar
electronegativity were substituted for zinc in the reduction of DDT.
These tests were made with the 10% acetic acid-acetone solvent system
as described earlier in the studies with zinc.
For comparison, reduced iron powder and aluminum flake and powder
samples were employed. The results of the analyses show less reduc-
tion than was obtained with zinc under similar conditions. Data from a
zinc reduction experiment are repeated for reference.
DDT (setting point 89°C 25. 0%
Xylene 55. 1
Deodorized Kerosene 16.8
Emulsifiers: Emnon 6932 2. 0
Agrimul 70A 1.0
Stabilizer: Epichlorhydrin 0. 1
100. 0%
extra heavy grade.
43
-------
Com-
ponent
DDEt
DDMU
DBMS
DDE
ODD
DDT
Reductant:
Reaction:
Retention
Time, min
3. 1
6.6
7.8
9.8
11.8
12.4
13. 0
14.2
15. 6
18. 0
21. 0
Fe powder Al-flake
118 hr, 25°C 3 hr, 25°
Analysis, %
Al-powder Zn-powder
3 hr, 25° 3 hr, 25°
0.3
1.2
4.0
15.8
17. 1
61.9
1.4
11.6
1.0
86. 0
1.4
13. 0
0.8
84. 6
0.8
24.5
0.8
0. 1
0.4
20. 0
10. 0
2.3
19.9
1.4
It should be noted that only a small amount of the 8-min peak, DDEt, a
major product of the zinc-dilute acetic acid reduction, has been obtained
with the iron powder, and that DDEt did not appear at all with the alumi-
num reduction system.
Experiments in which the reductant was manganese or magnesium metal,
or aluminum cleaned by forming an amalgam surface were performed
also. The reductions were carried out in the usual dilute acetic acid-
acetone medium. The data from these experiments follow:
Analysis, %, after Reaction for
3 hr at 25°C
Reductant: Mr>
A1-amalgam
Com-
ponent
DDMU
DDE
DDD
DDT
Retention
Time, min
12. 0
13.0
15.5
18.0
21. 0
0.6
11.9
2.2
85.3
<0. 2
0.7
5.9
3.9
89.5
1. 1
4.9
24.8
69.3
The results with manganese and magnesium show little decomposition,
with the major product appearing to be DDE. Hence, these metals ap-
pear to offer little promise. It should be noted, however, that about 25%
of the DDT was converted to DDD by the aluminum cleaned to produce an
amalgam surface. DDD also appears to be the initial step in the zinc
reduction of DDT.
44
-------
Experiments were also carried out using copper powder in place of zinc
in the dilute acetic acid-acetone medium. Although a blue coloration of
copper ion appeared in the reaction mix, the analytical data shows that
no significant reduction of the DDT was achieved.
Retention Analysis, %, after 24 hr
Component Time, min Reaction at 25°C
DDMS 13. 8 0. 3
DDE 15.5 5.0
DDT 20.8 94.7
Na2SQ3, Nal, CrCl3, Na2S2O3 as Reductants
The inorganic reductants Na2SC>3, Nal, CrCl3 and Na2S£O3 were also
examined as reductants in place of zinc. In each case, the reaction was
run in the 10% acetic acid-acetone medium used previously. The results
with each of these reductants show that 55 to 90% of the DDT was not re-
duced, and that the major product was DDE (10-40%). None of these re-
ductants produced the peak with an 8-min elution time, as was shown
with the zinc reduction.
Analysis, %, after Reaction
for 118 hr at 25°C
Reductant: Na0SO0
Com- Retention
<* ->
Nal
CrCl-
j
Na2S2°3
£ 4 was also examined in a. basic medium IN in KOH. The results
in each case showed little reduction of the DDT, with DDE being present
as the most significant product. The Na?S O -KOH reaction led to es-
sentially complete conversion to DDE.
45
-------
Analysis, %, after Reaction
for 48 hr at 25°C
Reductant: ZnS O Na~S O Na,S O +KOH
~~ £ i £ £ rt ^ £ ^T
Com- Retention
ponent Time, min
12.7 - - 0.1
DDMU 13.6 - - 0.8
14.2 0.2 0.2
DDE 15.6 10.3 9.5 99.2
19.0 0.1 0.3
DDT 21.4 89.4 89.3
Another test was made with sodium hydrosulfite in an aqueous acetone
medium. A solution of 1 g of DDT in 20 ml acetone was added to 7 g
of Na£S2O^ dissolved in 20 ml of water and reacted for 2 hours at 25°C.
The analytical data indicate approximately one-half of the DDT was con-
verted to DDE, but no significant quantities of other products were
found.
Reaction, 2 hours at 25 C
Component Retention Time, min %
7. 5 0. 1
8.4 0.1
DDMU 13.4 1.7
DDE 15.6 54.6
DDD 18. 2 0. 6
DDT 21.0 43.0
as a DDT Reductant
Sodium sulfide was also examined as a DDT reductant. When the re-
action was carried out in ethanol for 48 hr at 25°C, analysis showed
only DDE as a product, the simple dehydrohalogenation in the basic
medium being carried to completion with no reduction being observed.
Retention Analysis, % after Reaction
Component Time , min _ for 48 hr at 25°C _
DDE 15.6 98.5
LiBH4 as a DDT Reductant
The hydrides represent a class of important reductants which deserve
consideration. Since most of the simple metallic hydrides are in-
soluble in solvents for DDT, LiBH. was used in tetrahydrofuran solution.
46
-------
The THF was dried over L1BH4 before use. The results indicate little
reduction of the DDT.
Retention Analysis, %, after Reaction
Component Time, min for 3 hr at 25°C
(1, 1-diphenyle thane) 1.8 1.0
DDMU 13.3 0.5
14. 5 0.2
DDE 15.3 5.0
ODD 17.7 7.6
DDT 20.8 85.9
MECHANICS OF REDUCTIVE DEGRADATION
Results reported in preceding sections have shown that zinc dust in
weakly acid medium (10% acetic acid or (NH4j 2 SO4) led to the com-
plete or nearly complete reduction of DDT, without forming DDE as
a product. However, a series of other reductants with similar re-
ducing potentials did not yield the essentially complete destruction
of DDT shown by zinc. Therefore, further tests were made in an
effort to better define the role of zinc in the reaction. Reactions
were carried out in which the reductant was (a) magnesium, with
a slightly greater reducing potential than zinc, (b) magnesium + zinc,
(c) magnesium + ZnCl2, (d) zinc in granular form, and (e) zinc in
fine powder form. These tests were run with the 10% acetic acid-
acetone solvent system as described earlier. One gm of DDT was
reacted with the given amount of reductant (nominally 1 gm) in these
tests. The reaction was carried out for one day at 25°C. The re-
sults of the analyses of the products follows:
Reductant:
Com- Retention
ponent Time, min
Mg
1. 00 gm
Mg
0. 90 gm
Zn gran.
0. 10 gm
Analysis, '
Mg
1. 00 gm
ZnCl2
0. 164 gm
7o
Zn gran.
1. 00 gm
Zn
1.
powder
00 gm
DDEt 8.0 - 0.3 8.7 50.7 31.2
12.0 - - - - 0.1
DDMU 13.1 0.4 1.2 0.7 4.1 6.0
DDMS 14.0 0.1 0.4 1.7 4.6 18.0
DDE 15.5 10.7 8.3 5.9 0.5 -
DDD 18.0 4.0 15.3 26.4 38.4 44.8
DDT 21.0 84.8 74.4 56.7 1.7 -
These result show that the reduction of DDT by magnesium proceeds to
some degree when a small amount of ZnCl2 is present, or to a lesser
extent when zinc metal is used with the Mg. However, in neither case
47
-------
was the reaction as efficient as that obtained with zinc metal alone as
the red.uctant. The reaction with 20 mesh zinc granules appeared to
progress slightly better than that with zinc powder in this test.
Additional tests were made in which ZnCl2 was used in conjunction
with aluminum, iron, Nal and Na2SC>3 - systems that showed a small
reduction of DDT in earlier tests. In the experiments with aluminum,
fresh samples of aluminum granules and aluminum powder were used
as the reductant. The experiments were carried out using the metal
as the reductant, and adding zinc ion in order to observe any specific
effect of the zinc. The results of the analyses from, the tests with
aluminum follow:
Com-
ponent
DDE
DDD
DDT
Reductant:
Retention
Time, min
Analysis, %, after 46 hr Reaction at 25 C
Al granules Algranules Alpowder
(1 g) (1 g) (1 g)
ZnCl2
(. 164 g)
12. 0
13. 0
15. 6
17.8
21.0
0. 1
1.7
2.2
0.4
95.5
0. 1
1.0
1.8
0.4
96.9
0. 1
3.0
2.8
0.7
92.6
Al powder
dg)
ZnCl2
(.165 g)
0. 1
1.8
3.6
2.2
92.3
These results show that the aluminum was ineffective in reducing DDT,
both as the powder and in granular form. Added zinc ion had no signi-
ficant effect on the reduction.
The reductants sodium iodide and sodium sulfite with added zinc ion
were also examined but showed no significant effect in reducing DDT
to a desirable end product. In these tests, 1 g of the DDT with 1 g of
the reductant salt and 0. 16-0. 17 g of ZnCl2 were reacted in the medium
composed of 20 ml acetone and 10 ml of 10% acetic acid. The results
of the analyses are as follows:
Analysis, %, after 46 hr Reaction at 25 C
Component
DDMS
DDE
DDD
DDT
Reductant:
Retention
Time, min
14. 0
15.6
17.8
21.0
Nal(l g)
Na2S03 (1 g)
ZnCl, (. 165 g) ZnCl, (. 173 g)
0. 2
7. 2
0.7
91.9
0.2
5. 1
0.5
94.2
48
-------
Results reported earlier showed that some reduction of DDT was ob-
tained when iron was used as the reductant, although the extent of
reaction was significantly less than that obtained with zinc. A further
test was carried out in which some zinc ion (as ZnCl2) was added to
the reaction mix in an effort to increase the reactivity. In this test
1 g of DDT was reacted with 1 g of iron powder + 0. 164 g of ZnC^;
the usual dilute acetic acid-acetone solvent mixture was employed.
The following results were obtained:
Retention Analysis, %, after 24 hr
Components Time, min Reaction at 25°C
DDEt 7.8 1.5
DDMS 14. 0 0.7
DDE 15.6 4.9
DDD 17.8 17.4
DDT 21.0 75.6
The possibility that an easily consumed impurity, such as ZnO, may
promote the reaction, or that impurity metals could catalyze the re-
duction of DDT was considered. In one series of experiments, finely
powdered zinc oxide was added to the reaction mix in an effort to es-
tablish the effect on the extent of reaction. In this test, zinc oxide
was added to the usual reaction mix of 1 g of DDT, 1 g of zinc dust,
10 ml of 10% acetic acid and 20 ml acetone. The reaction was carried
out for 90 hr at 25°C. The results were as follows:
Com- Retention Analysis, %, after 90 hr Reaction at 25 C
ponent Time, min 1. 00 g Zn +0. 01 g ZnQ +0. 1 g ZnO +1 g ZnO
6.8 0. 2 0. 1 0. 2 0. 1
DDEt 7.8 32.5 34.2 30.8 25.9
10.0 0.1 0.4 0.5 0.5
12. 0 0. 1 0. 1 0. 1
12.4 - 0.4 0.5 0.2
DDMU 13. 0 4. 6 5. 1 5. 1 4. 8
DDMS 14.0 37.6 39.3 41.5 30.6
DDD 17.8 24.9 20.1 21.5 37.8
DDT 21.0
Clearly, the added zinc oxide has not promoted a more extensive degra-
dation of the DDT; indeed, the results with increasing zinc oxide suggest
a reduced degradation of the DDT. The loss of reduction with increased
zinc oxide may represent the consumption of acid by the basic oxide.
49
-------
SEC TION VI
DEGRADATION OF DDT BY CATALYZED METALS
CATALYZED ZINC REACTIONS
Reduction of DDT Using Zinc-Copper Couple
The studies described previously have shown that zinc dust in weakly
acid medium leads to complete or nearly complete reduction of DDT.
However, on close examination of the data, it appears that a complex
two-path reaction may be involved. A portion of the DDT appears to
be converted rapidly to the ethane derivative, DDEt, losing all three
aliphatic chlorine atoms. Another portion appears to be reduced by
the route DDT >DDD—»DDMS »DDEt; the stepwise dechlorination
involved in the second pathway appears to be a slower process. It was
important, therefore, to determine the conditions that promote the ap-
parently rapid and more complete reduction of DDT to bis(p-chloro-
phenyl)ethane (DDEt).
The possibility that metallic impurities in the zinc may act as catalysts
was considered. In one test a milli-mole. of copper ion was added to
form a zinc-copper couple. Zinc-copper couples are used to advantage
in some organic reductions (Reference 35). Other reaction conditions
were the same as previously employed (1 g DDT, 1 g zinc dust, 10 ml
10% acetic acid, 20 ml acetone). The reaction was carried out for 90
hr at 25°C. The analysis of the products follows:
Retention Analysis, %, after 90 hr
Component^ Time, min Reaction at 25°C
4.0 0.1
6.8 1.2
DDEt 7.8 85.0
10.0 0.1
12.0 0.1
DDMU 13.0 3.5
DDMS 14.0 10.1
DDE 15.6
DDD 1 7. 8
DDT 21.0
This test was significant in that almost complete conversion to the ethane
derivative of DDT, DDEt, was obtained. It should also be noted that no
DDT, DDD or DDE was shown by the analysis. Additional tests with the
metal couple were performed in order to further define the role of this
important additive.
51
-------
Tests were carried out in which the rate of the reduction of DDT by the
zinc-copper couple was compared with that of zinc reduction, and in
which the ratio of zinc-to-copper was varied.
In one series of tests, the couple was formed by adding the aqueous
copper solution (1 meq of CuC^) to the acetone solution of DDT (1 g
DDT in 20 ml acetone) in which the zinc (1 g) was suspended. The
copper appeared to precipitate on the zinc surface, leading to the
formation of a very dark (brown to black) precipitate, rather than the
usual grey of the zinc. After the formation of the couple, 10 ml of
10% acetic acid was added; the final solution was then 0. 5 normal in
acetic acid (technical-grade zinc dust was used in these tests). The
results of assay at a series of times follows:
Com- Retention Analysis, %, after reaction, hrs, at 25 C
ponent Time, min 1/4 1 2 4 8
6.8 0.9 1.7 1.2 4.3 1.5
DDEt 7.8 56.7 54.5 62.4 68.7 72.5
10.6 0.1 0.4 0.4 0.1 0.3
11.9 0.1 0.1 0.4 0.1 0.1
DDMU 12.8 3.2 4.0 4.0 3.4 5.0
DDMS 14.0 4.4 7.4 8.0 7. 9 . 11.2
DDE 15.6 0.2 0.1 0.1 0.1 0.1
ODD 17.8 34.4 31.8 23.5 15.4 9.2
DDT 21.0 - - - - 0.1
These results show a larger portion of the DDEt is formed within the first
15 min, and that most of the DDD produced initially is consumed in 8 hr
at ambient temperatures.
In another series of tests, the copper (1 meq) was added after the acid
(the reaction appears to be initiated on acid addition). The results of
these tests are as follows:
Com- Retention Analysis, %, after Reaction, hrs, at 25 C
ponent Time, min 1/4 2 4
6.8 0.1 0.1 0.2
DDEt 7.8 47.4 63.1 66.5
10.6 0.1 0.1 0.1
11.9 0.1 0.1 0.1
DDMU 12.8 4.9 3.8 3.5
DDMS 14. 0 4.7 7. 5 9.8
DDE 15. 6 0.2 <0. 1 <0. 1
DDD 17.8 42.3 25.2 19.5
DDT 21.0 0.1 - 0.1
52
-------
These results are in reasonable agreement with the previous series,
indicating that the order of copper addition does not appear to be a
large factor in the reaction.
A comparative series of tests in which the zinc powder (technical-grade
dust) was used as the reductant without the added copper, gave the fol-
lowing results:
Com- Retention Analysis, %, after Reaction, hrs, at 25 C
ponent Time, min 1/4 1 248
6.8 - 0.2 0.1 0.1 0.1
DDEt 7.8 24.6 28.7 27.7 26.9 26.5
10.6 0.3 0.5 0.4 0.1 0.2
11. 9 0. 1 0.2 0. 1 0. 1 0. 1
12.4 - 0.4 0.2 - 0.2
DDMU 12.8 5.5 5.1 5.6 5.7 5.9
DDMS 14.0 12.4 13.7 15.5 21.7 23.9
DDE 15. 6 -
DDD 17.8 56.5 51.1 50.4 45.3 43.0
DDT 21.0 0.7
A comparison of the results obtained with the zinc-copper couple, and
those using zinc alone as the reductant, reveal a dramatic difference.
The amount of DDEt product formed in an equivalent time was 1. 9 to
2. 7 times greater in the samples in which the zinc-copper couple was
used, compared to those in which zinc was the reductant. The samples
using the zinc-copper reductant also produced less DDD as a product;
the ratio of DDD when zinc was used for reducing compared to the zinc-
copper samples ranged from 1. 6 after 15 min to 4. 7 after 8 hrs. The
amount of the monochloroethane intermediate, DDMS, was also less
when the zinc-copper couple was employed by a factor of 1.8 to 2. 8.
A comparison of the results is shown graphically in Figures 1, 2 and
3 following.
In an additional set of samples, the extent of reaction after 15 min at
25°C was determined, using CP grade zinc powder rather than the
technical grade product used in the above studies. In this set of ex-
periments a comparison was made between samples of DDT reduced
with zinc, and with the zinc-copper couple. The results follow:
53
-------
Ul
o
LLJ
80 i—
70
60
50
40
30
20
10
O Zn-Cu COUPLE
A Zn REDUCTANT
234 567
REACTION TIME, HOURS
Figure 1
Rate of Formation of bis(p-Chlorophenyl) Ethane Product (DDEt) at 25°C
When DDT Reduced with Zn. Cu Couple, or Zn Powder
Solution 0. 5 N in Acetic Acid
8
-------
® Zn • Cu COUPLE REDUCTANT
A Zn REDUCTANT
70
60
50
* 40
k»
O
UJ
5 30
a:
O
u_
g 20
Q
10
0
A
1234567
REACTION TIME, HOURS
Figure 2
Rate of Formation of bis(p-Chlorophenyl) Dichloroethane Product (DDD) at 25°C
When DDT Reduced with Zn«Cu Couple, or Zn Powder
Solution 0. 5 N in Acetic Acid
8
-------
O Zn • Cu COUPLE REDUCTANT
A Zn REDUCTANT
30
a 20
ee.
O
UL
10
12 34567
REACTION TIME, HOURS
Figure 3
Rate of Formation of bis(p-Chlorephenyl) Chloroethane Product (DBMS) at 25°C
When DDT Reduced with Zn. Cu Couple, or Zn Powder
Solution 0. 5 N in Acetic Acid
8
-------
Analysis, %, after Reaction
for 15 min at 25°C
Com- Retention ' CP Zinc Powder-
ponent Time, min CP Zinc Powder Cu Couple
6.8 0.1 0.1
DDEt 7.8 27.1 37.8
10.6 0.2 0.2
11.9 0.1 0.2
DDMU 12.8 4. 0 3. 4
DBMS 14. 0 8. 1 4. 2
DDE 15.6 - 0. 1
ODD 17.8 60.2 53.9
DDT 21. 0 0.4 0. 1
These experiments show that the zinc-copper couple gave somewhat
better reduction than the zinc powder, but that the reduction was not as
efficient as that obtained when the technical grade zinc powder was used
in a zinc-copper couple. In an effort to determine the reason for this
difference, the particle size and shape of the powders was examined,
and the impurities in the materials determined by spectrographic
analysis.
The particle size of the technical grade and CP grade powders, as shown
from, photomicrographs, was roughly equal, although the technical grade
material was more nearly spherical in shape and the CP grade product
tended to be elongated in shape. The particles are a nominal 5 microns
in diameter. The trace metal analysis obtained by semi-quantitative
arc spectra is as follows:
Analysis, %
Tech. Grade CP Powder CP Granular
Metal Powder
Iron 0. 16 0. 07 0. 007
Aluminum 1. 2 - 0. 03
Lead 0. 75 0. 6
Silicon 0. 01 0. 005 0. 16
Copper 0. 005 0. 02 0. 0005
Indium 0. 03 0. 14
Cadmium 0. 12 0. 07
Chromium 0. 02
The trace analysis gives no clear-cut explanation for the apparent ef-
fectiveness of the technical grade zinc, although the iron impurity may
offer one possibility.
Tests were also run in which the amount of copper added to form the
couple was varied. In these tests, the efficacy of reduction of DDT after
15 min reaction at 25°C was compared. Common to these tests was the
57
-------
use of 1 g DDT in 20 ml acetone solvent, 1 g of technical grade zinc dust,
the addition of the copper before the acid, and the use of 10 ml of 10%
acetic acid, giving a final acidity of 0. 5 N. The results of the tests fol-
low:
Analysis, %, after 15 min Reaction at 25 C
Com- Retention Millieq. of Copper added as aq
ponent Time, min 0. 1 1. 0 2. 0 10. 0
6. 8 2.4 0. 9 0. 2 0. 1
DDEt 7.8 29.0 56.7 52.0 37.6
10. 6 0.4 0. 1 0.4 0.4
11. 9 0. 1 0. 1 0. 2 0.3
DDMU 12.8 4.6 3.2 2.9 3.0
DDMS 14. 0 9. 9 4. 4 3. 3 1. 8
DDE 15.6 - 0.2 0.2 1.3
DDD 17.8 53.8 34.4 40.2 43.8
DDT 21.0 - - 0.6 11.9
Examination of these data show that the maximum yield of the product
DDEt was shown with 1. 0 meq Cu/g Zn, as well as minimal amounts
of DDD and DDT. Hence this ratio of copper to zinc was used in further
testing.
Since several methods for the preparation of the zinc-copper couple are
mentioned in the literature, a comparison of the efficiency of the reduc-
tants to transform DDT to suitably degraded products was made. In this
series, both technical grade and CP grade zinc dust reacted with 1 meq
of CuCl2 (1 ml of 1 N solution) were compared with a freshly prepared
wet-couple, a couple prepared in wet form and then dried, and a couple
prepared by elevated temperature reduction of CuO with hydrogen. The
preparation of the couples follows.
Fresh, Wet Couple. This material was prepared basically by the method
of Corbin, Hahn and Shechter (Reference 36). A 1 g sample of CP zinc
powder was washed rapidly ('^lO sec) with 3-1 ml portions of 3% HC1,
then twice with 10 ml portions of water. The zinc was then treated twice
with 2 ml portions of 2% CuSO^ until the blue copper color disappeared
(•~1 min), then washed twice with 2 ml portions of water and 4 times
with 3 ml washes of acetone. The sample was then used immediately.
Dry Couple. This sample was prepared by the method of Smith and
Simmons (Reference 37). A 24. 6 g portion of CP zinc was weighed into
a flask equipped with a magnetic stirrer. Twenty ml of 3% HC1 was
added and the suspension was stirred rapidly for 1 min. The acid
solution was decanted off and a fresh 20 ml portion of 3% HC1 added
and the process was repeated. A total of 4 acid washes was given the
zinc. The dust was then washed 5 times with 50 ml portions of water,
stirring each portion rapidly for 1 min and then decanting. The zinc
58
-------
was then treated twice with 40 ml portions of 2% CuSO4, stirring each
portion for 2 min and then decanting. The sample was then washed 5
times with 50 ml portions of water, decanting the fluid through a filter
paper in a Buchner funnel so as to avoid loss of the product. The mate-
rial was then washed 4 times with 50 ml portions of absolute ethanol
and 5 times with absolute ether, in each case decanting through the
filter so as to reclaim the product. The material was then washed
into the filter funnel with absolute ether, washed three additional times
with ether, and dried under water suction with a rubber dam covering
the filter funnel. The material was then transferred to a vacuum desic-
cator and dried overnight under vacuum (P_O desiccant) before use.
Hot Reduced Couple. The third couple, prepared from an elevated
temperature reduction of CuO mixed with zinc dust, was made by the
method of Noller (Reference 38). A 30 g sample of CP zinc powder
was blended with 2. 5 g of CuO, and placed in a 50 ml, 3-necked flask
fitted with a thermometer, a fritted glass inlet tube for hydrogen in-
troduction and a gas outlet tube. The gas inlet tube was placed below
the level of the metal powder bed. A constant flow of hydrogen gas
was introduced into the flask during the reduction. The referenced
directions stated that the reactants should be heated to slightly below
the fusion point (nap Zn 419. 5°C); accordingly, the mass was heated
to 400°C where a steel-grey mass formed in a few minutes' reaction
time. This mass was cooled, ground to a fine powder with a mortar
and pestle, and stored in a vacuum desiccator over P?Cv.
Zinc Amalgam. A zinc amalgam sample was also prepared for com-
parison with zinc and zinc-copper couple reductants. The method of
preparation was basically that given by Fieser and Fieser (Reference
35). A 1 g sample of CP powdered zinc was treated for 5 min with 1. 5
ml of 0. 5 N HC1 containing 0. 1 g mercuric chloride, the reagent was
decanted from the zinc amalgam and the material was used immediately.
In testing these materials, a 1 hr reaction time at 25 C was chosen,
since the reaction did not appear to be complete at this point and there-
fore differences between the reductant preparations might be determined
more easily. In all tests, 1 g of DDT in 20 ml acetone, 1 g reductant,
xnd 10 ml 10% acetic acid was used (solution 0. 5 N in acetic acid). The
samples were stirred on a magnetic stirrer during the reaction. The
results follow:
59
-------
Analysis, %, after Reaction for 1 hr at 25 C
Reductant
Tech Fresh Hot
Com- Retention Zn CP Zn Dried Wet Reduced Zn-
ponent Time, min +CuCl2 +CuCl2 Zn-Cu Zn-Cu Zn-Cu O amalgam
DDEt
DDMU
DDMS
DDE
ODD
DDT
6.8
7.8
9.8
11. 5
11.9
12. 6
14. 0
15.4
17.8
21.0
0..3
47.6
0.7
0.1
0.3
4.0
5.7
0. 1
41. 1
0.1
0. 1
38. 0
0.5
0. 1
0.8
3.8
6.6
0. 1
49.9
0. 1
0.2
35.8
0.5
0. 1
1.0
3.6
6.7
<0. 1
51.9
0.1
0. 1
36.9
0.5
0. 2
1.1
3.8
7. 1
<0. 1
50. 1
<0. 1
0. 1
30. 1
0. 2
<0. 1
0.8
3.0
5.0
0.1
60.8
0. 1
23.3
0.6
0.2
_
6.3
0.4
0.4
18.9
49.9
An examination of these data shows that the couple prepared from technical
grade zinc and 1 meq of CuCl2 gave the best reduction. The couples pre-
pared from CP zinc + CuCl2 , dried Zn-Cu, and fresh, wet Zn-Cu were
all in reasonably close agreement, suggesting that these methods of pre-
paration are about equally effective; these preparations applied to technical
grade zinc may increase the activity somewhat. The hot, reduced Zn-CuO
couple and the zinc amalgam were both less effective preparations for DDT
reduction.
Tests were conducted to determine the shelf stability of dried Zn« Cu
couple. A larger batch was made as described above and tested after
one day and after 2 weeks' storage at 25°C. The results are tabulated
below:
Analysis, %, after Reaction for 24 hr at 25 C
Com-
ponent
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time, min
6.5
7.6
10. 1
11.6
12.1
12.8
14.0
15.3
17.7
21. 0
Dried Zn- Cu
After 1 day
0.5
65.7
0. 1
0. 1
0.6
3.9
8.9
0.7
19.5
Dried Zn. Cu
After 2 weeks
0. 2
66.5
0. 2
0.2
0. 2
3.5
13.9
1.0
14.3
These results show that the reductive capability of the Zn- Cu couple is
unchanged after 2 weeks' storage at room temperature.
60
-------
Anhydrous Reduction System
The screening tests described earlier in this report have consisted of
the examination of 1 g DDT and 1 g reductant in a solvent system con-
sisting of 20 ml acetone and 10 ml 1. 5 N acid. A voluminous precipitate
quickly forms which dissolves after about 10 to 15 min reaction with the
zinc reductants, and has not dissolved with other less efficient DDT-
reducing systems. It was of interest in establishing the mode of re-
duction to determine whether the initial precipitate represented a zinc
complex, or whether the flocculent mass was DDT which was consumed
in the early stages of the reaction. In an experiment where the preci-
pitate after 1 min reaction was quickly transferred to a filter funnel and
separated from the liquid phase, it was found that the solid mass con-
tained only 0. 05% zinc. Since the formation of a zinc complex would be
expected to give a product with 10 to 20% zinc or more, depending on
the complex, it can be concluded that significant zinc complex formation
is not observed. The precipitate assayed 85. 8% unconsumed DDT, 11. 7%
DDE, 1. 6% DDD and 0. 3% DDEt.
Since the DDT is presumably precipitated by the water, it was of interest
to examine a similar system from which the water was excluded, on the
basis that the reaction might proceed more completely if the DDT were
held in solution. Accordingly, a test was carried out in which the sol-
vent system consisted of 29 ml acetone and 1 ml glacial acetic; this mix
gave a final acidity of 0. 5 N, the same as used in the normal screening
tests. Very little reduction occurred; 50% remained as DDT, 38% was
converted to DDE and only 8% DDEt was formed.
Sulfamic Acid Reduction System
It was of interest to determine whether an acid available in solid form
might be used for providing the requisite acidity. A screening test
with Zn« Cu couple in which 1. 5 N sulfamic acid was substituted for
1. 5 N acetic acid showed a somewhat lower conversion to DDEt. The
experimental results are tabulated below, along with those for a typi-
cal run using acetic acid.
Com- Retention Analysis, %, after Reaction for 24 hr at 25 C
ponent Time, min 1. 5 N Sulfamic Acid 1. 5 N Acetic Acid
6. 6 0. 5 0. 2
DDEt 7.8 44. 5 66. 5
10.4 0.4 0.2
11.8 1.8 0.2
12.2 - 0.2
DDMU 12. 8 6.8 3. 5
DDMS 14. 0 7. 3 13. 9
15.2 0.2
DDE 15.4 - 1.0
16.0 0.5
DDD 17.8 38. 0 14. 3
DDT 21.0
61
-------
Rate of Zinc-Copper Reduction of DDT
A determination of the rate of reduction of DDT by the zinc-copper couple
was carried out in an effort to establish optimal reaction conditions. In
these tests, the reaction of 1 g of DDT with 1 g technical grade zinc to
which 1 meq of CuCl2 was added and in which the solution was made 0. 5
N in acetic acid (10 ml 10% acetic acid) was studied. Samples were stirred
for the reaction period with magnetic stirrers. After the reaction period,
the soluble zinc, copper and chloride salts were extracted with water,
and the DDT and organic degradation products extracted with 85% hexane-
15% methylene chloride solution. The zinc and copper were determined
by atomic adsorption, the chloride by micropotentiometric titration, and
the DDT and products by the usual gas chromatographic technique. The
results are given in Table II.
These tests show clearly that reduction is rapid, that a substantial amount
of the zinc is consumed in the first few minutes of reaction, and that a
significant amount of chloride ion is produced and acid consumed. The
ratio of zinc to chloride in solution increases from 2. 09 after 19 min
reaction to 2. 58 after 24 hrs. This increase may represent slow re-
action of the zinc with acetic acid to form soluble acetates. It is of
interest to note the very low quantities of copper in solution, with the
quantity of copper decreasing to detection limits after about 2 hrs re-
action.
The gas chromatographic results are comparable with those given ear-
lier in this report. From the amounts of the reduction components as
determined by gas chromatography, values were calculated for the
amounts of chloride ion produced. These calculated chloride values
are tabulated below with the measured chloride values for comparison.
Chloride Ion from Reduction of DDT
Reaction Measured in Solution, Calculated from
Time, min millimols G. C. , millimols
0 - 0. 12
19 4.06 4.73
30 4.65 5.44
60 4. 67 5. 60
120 5.50 6.19
240 5. 58 6. 37
480 5.86 6.55
1473 6.43 6.83
The calculated values parallel the measured values but are about 0. 7
millimol higher, in most instances.
62
-------
TABLE II
RATE OF CATALYZED
Chloride
Reaction
Time, Min.
0
19
30
60
120
240
480
1473
Zinc in Copper in
Solution Solution
g g
-
.381
.450
.431
.569
.569
.608
.688
-
.0010
.0008
.0003
< .0002
<.0002
<.0002
<.0003
in
Solution
g
.038*
.182
.203
.204
.233
.236
.246
.266
ZINC REDUCTION
OF DDT AT 25°C
Analysis, %,
PH
2.58
4.22
4.43
4.61
4.72
4.98
5.36
5.56
DDEt
-
37. 3
42.8
44.8
54.6
58.1
60.6
65. 7
DDMU
-
3.9
3.9
4.9
4.0
4.1
3.8
3.9
DDMS
0.4
4.1
5.3
5.3
7.1
6.9
8.8
8.9
of Component
DDE
1.5
0.6
0.1
0.1
0.1
0.1
0.1
0.1
DDD
0.4
42.4
46.1
43.5
33.2
29.3
25.0
19.5
DDT
97.7
11.1
0.6
0.2
0.1
0.1
0.2
0.3
^Presumed to result from CuCl- added to form couple.
-------
CATALYZED REDUCTANTS OTHER THAN ZlNC
Degradation of DDT Using Aluminum-Copper System
The marked increase in the reduction of DDT by the zinc-copper couple,
compared to zinc alone, suggested that a reexamination of the efficacy
of other metal reductants should be made, using these metals as a
copper couple. In these tests 1 g of DDT was reacted with 1 g of the
metal-copper couple (1 meq of aq. CuCl2 added to form couple) in a
solution of 20 ml acetone and 10 ml 1. 5 N acid; both acetic and sul-
furic acids were examined. The samples were reacted for 90 hr at
25QC.
When an aluminum-copper couple reductant was employed, two in-
teresting results were obtained. The analysis of the sample indicated
that only about 15% of the sample responded to the gas chromatograph,
and that of that sample about 34% was converted to DDEt when acetic
acid was used, and 64% to DDEt when sulfuric acid was the acid source.
The data follow:
Analysis, %, after Reaction
for 90 hr at 25°C
Acetone Soluble Retention Acidified with
Component Time, min Acetic Acid Sulfuric Acid
DDEt 7.7 4.8 9.2
9.8 2.3 0.7
11.6 0.2 0.1
12.4 0.2
DDMU 13. 0 0.8 0.6
DDMS 14.2 0.2 0.2
DDE 15.2 1.5 1.4
DDD 17.8 4.0 2.2
DDT 20.8 0.2 0. 1
14.3 14. 5
Because of the apparently high recovery of DDEt from the reaction
carried out in sulfuric acid, as well as the very low sample balance,
the experiment was repeated us'lng. larger quantities. In this test,
five-fold larger quantities were used and the reaction was carried out
for 47 hr at 25°C. This analysis showed that of the acetone soluble
material, 61% was DDEt, but that the acetone soluble fraction accounted
for only 5. 3% of the total sample. Undecomposed DDT represented only
0. 3% of the initial sample, and DDD 0. 1% of the initial sample; all of
these materials are readily soluble in acetone. However, this larger
sample showed a voluminous precipitate which could only be partially
accounted for by the unreacted aluminum-copper couple. The preci-
pitate was insoluble in ethanol and hexane, as well as acetone, but
the major portion (other than unreacted reductant couple) was found
64
-------
to be soluble in warm benzene. When extracted and recrystallized, a
product with a melting point of 267°C was obtained. The benzene ex-
tract weighed 86. 2% of the initial weight of DDT.
The infra-red analysis showed the presence of C-C1 bonds, but no car-
bonyl or phenolic OH. It was hypothesized that the compound might be
tetra(p-chlorophenyl)-tetrachlorobutane, formed by reductive coupling
of two DDT molecules:
Cl
Elemental analysis is consistent with this hypothesis.
Analysis: _C_ || Cl
Theor, C28H18Clg 52. 6 2.82 44. 5
Found 51.8, 51.2 3.0, 2.6 42.7, 43.0
The sample was also examined by nuclear magnetic resonance spectros-
copy, using CDC^/CH^C^ and hexamethyl phosphoramide as the sol-
vents. The spectrum exhibits an aromatic pattern and a slightly broa-
dened methinic hydrogen singlet whose relative areas are consistent
with the hypothesized structure.
An examination of the literature reveals that the hypothesized compound
has been prepared, and indeed has been synthesized from DDT. Insec-
ticidal properties were claimed for the compound by Bernimolin in 1949
(Reference 39), but this finding was subsequently shown to be incorrect
by Riemschneider (Reference 40). This finding was important because
Reimschneider had claimed that chlorinated hydrocarbons with a melting
point >200°C and a molecular weight >430 should not have insecticidal
properties because of reduced lipoid solubility. The material used in
these studies had been prepared by reducing DDT with hydrogen in the
presence of a palladium catalyst (Reference 41). The reported melting
point of 1, 1, 4, 4-tetra(p-chlorophenyl)-2, 2, 3, 3-tetrachlorobutane of
65
-------
270° (Reference 40) compares well with the value of 267° obtained in
this study. The tetrachlorobutane derivative does not give a gas chro-
matographic response under the conditions employed in this study.
It thus appears that aluminum -copper couple has almost completely
degraded DDT (99. 7%), giving a trace (0. 1%) of DDD, and the major
product 86. 2% (equivalent to 95% DDT) of the tetra(p-chlorophenyl)-
tetrachlorobutane. This reductant offers a different approach to
pesticide degradation in that a product with apparently very low lipoid
solubility can be produced by this technique; it would also be expected
that the water solubility of this product would be much less than DDT.
The concept of pesticide deactivation by reduced lipoid solubility may
deserve further study.
Degradation of DDT Using Iron- Copper System
Reduced iron powder plus copper was also examined. One gram of
DDT was reacted with 1 g of iron-copper couple (1 meq of aq CuCl2
added to form couple) in a solution of 20 ml acetone plus 10 ml 1. 5
N acid; both acetic and sulfuric acids were examined. The reactions
were allowed to proceed for 90 hr at 25°C; the analyses of the acetone-
soluble components are as follows:
Acetone-Soluble
Component
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time,
Analysis, %, after Reaction
for 90 hr at 25QC
Acidified with
mn
7.7
9.8
13. 0
14. 0
15.4
17.8
20.8
Acetic Acid
7.0
-
0. 9
1.4
9.4
57.3
23.9
Sulfuric Acid
1.5
2.6
0. 5
0. 2
4.5
8.2
82.6
Although the reaction proceeded to substantial breakdown of DDT to
DDD when the acetic acid was used, the iron reduction does not appear
to be as efficient as the zinc. However, some discrepancies in the
material balance suggested additional insoluble product such as that
described for the aluminum couple above.
The test using acetic acid was repeated. After removing the acetone-
soluble components (equivalent to 12% of the original DDT), the solid
residue was extracted with warm benzene. Evaporation of the benzene
left a crystalline solid with a melting range of 265-267°C; a mixed melt-
ing point determination with authentic 1, 1, 4, 4-tetra(p-chlorophenyl)-
2, 2, 3, 3 -tetrachlorobutane showed no depression. The benzene extract
weighed 57. 6% of the initial weight of DDT (equivalent to 64% DDT).
66
-------
Although the Fe- Cu couple gives substantial degradation of DDT forming
the tetrachlorobutane derivative as the major product, it did not appear
to be as effective as the Al« Cu couple in this test.
Degradation of DDT Using Magnesium-Copper Couple
Magnesium was re-evaluated as a reductant using added copper. One
gram of DDT was reacted with 1 g magnesium-copper couple (1 meq.
aq. CuCl2 added to form couple) in a solution of 20 ml acetone and
10 ml 1. 5 N acid; both acetic and sulfuric acids were examined. The
samples were reacted for 90 hr at 25°C. The results follow:
Analysis, %, after Reaction
for 90 hr at 25°C
Com.- Retention Acidified with
ponent Time, min Acetic Acid Sulfuric Acid
3.8 <0. 1
DDEt 7.7 4. 3 2. 1
10. 2 <0. 1 <0. 1
11.7 - <0. 1
DDMU 12. 9 0. 7 0. 6
DDMS 14. 0 2. 1 0.3
DDE 15.4 1.7 2. 9
DDD 17.8 13.2 5.5
DDT 20.8 77.9 88.6
The Mg« Cu couple gave limited reduction of DDT. There were no dis-
crepancies in the material balance.
Degradation of DDT Using Cadmium-Copper Couple
Cadmium was also examined as a reductant, because of its close simi-
larity to zinc. One gram of DDT was reacted with 1 g cadmium-copper
couple (1 meq. aq. CuCl2 added to form couple) in a solution of 20 ml
acetone and 10 ml 1. 5 N acid; again both acetic and sulfuric acids were
examined. The tests were of 90 hr duration at 25°C. The test results
follow:
67
-------
Analysis, %, after Reaction
for 90 hr at 25°C
Com- Retention Acidified with
ponent Time, min Acetic Acid Sulfuric Acid
3.8 <0.1 <0.1
6.5 0.4 <0.1
DDEt 7.7 59.8 28.0
9.8 0.8 <0.1
11.7 <0.1 <0.1
DDMU 12.9 3.2 0.9
DBMS 14.0 7.3 3.0
DDE 15.2 0.4 2.9
ODD 17.8 10.1 5.1
DDT 20.6 18.0 60.2
Although the Cd-Cu couple gives substantial degradation of DDT, it
does not appear to be as effective as the Zn- Cu reductant.
Mechanics of Reductive Degradation - Use of Zinc-Silver Couple
Tests in which a zinc-copper couple, or other metal-copper couples,
were tested as reductants have been described. The use of these
couples has resulted in more rapid and more complete reduction of
DDT to DDEt or to tetra(p-chlorophenyl)-tetrachlorobutane. However,
it had not been determined whether the copper was a specific catalyst
for these reactions or whether other metals chemically similar to copper
would also serve to accelerate the reduction of DDT. In a comparison,
the couple formed by the addition of silver ion to zinc dust was examined
as the reductant. In this test 1 g of DDT in 20 ml acetone was added to
1 g technical grade zinc dust, and the couple was formed by adding 1 meq
of AgNO3 solution. The solution was then acidified with 10 ml of 1. 5 N
acetic or sulfuric acid. The results of the analyses of products after
24 hr reaction at 25°follow. Data from a similar test with the Zn« Cu
couple are given for comparison. These analyses represent the assay
of the acetone soluble fractions.
Analysis, %, after Reaction for 24 hr at 25°C
Com-
ponent
DDEt
DDMU
DDMS
DDE
DDD
DDT
Retention
Time, Min
6.8
7.8
9.8
10.6
11.9
12.8
14.0
15.6
17.8
21.0
Zn- Ag
HOAc
_
55.5
1.0
_
0.2
9.7
7.2
2.5
23.9
-
Zn. Ag
HZS04
_
68.4
0.7
_
0.2
11.2
4.3
2.5
12.1
0.7
Zn» Cu
HOAc
1.1
66.5
-
0.5
0.1
3.5
8.4
0.1
19.7
0.1
68
-------
A deficiency in the material balances of the Zn. Ag tests suggested the
formation of an acetone-insoluble product. Consequently, the Zn> Ag
acetic acid test was repeated and the acetone-insoluble residue was
extracted with warm benzene. Evaporation of the benzene left a
crystalline solid, 0. 102 g, melting in the range 226-228°C, which
is as yet unidentified. The acetone-soluble portion (composed of
DDEt, DDD, and DDMS) corresponded to 43% of the DDT used in the
test.
In another test, the use of a couple formed by the combined addition
of iron and copper salts to zinc dust was examined in an effort to fur-
ther improve the efficacy of the catalyst. However, the activity was
approximately the same as that obtained when the zinc-copper couple
was used. The analytical results are comparable with those of the
Zn. Cu reductant given in the preceding tabulation.
69
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SECTION VII
DEGRADATION OF DDT IN SOIL
An initial series of tests were made to determine whether the zinc re-
duction of DDT could be carried out in the presence of an organic soil
mix. In these initial tests, three samples were compared. In the first,
the reaction of 1 g of zinc with 1 g of DDT in 30 ml of the dilute acetic
acid-acetone medium was carried out. In the second test, 1 g of DDT
-F 30 ml of the solvent medium was reacted with 10 g of soil mix (no
zinc was used), and in the third test, 1 g of DDT, 1 g of zinc and 10 g
of the soil mix were reacted in the solvent. The soil mix was a com-
mercial^ outdoor planting mix and consisted of redwood humus and nitro
humus. * The samples after reaction were washed through fritted-glass
filters with 100 ml of acetone. Further treatment of the organic mix in
a Soxhlet extraction device revealed that no additional DDT nor degra-
dation products were extracted. The results of analyses of the filtrates
follow:
Analysis, %, after Reaction
for 24 Hr. at 25°C
Reductant:
Zn Zn + Soil Soil(Control)
Component
DDEt
DDMU
DDMS
DDE
ODD
DDT
Retention
Time, Min
7.0
7.8
10.8
12.0
12.5
13.0
14.0
15.6
18.0
21.0
<0.2
30. 3
<0.2
<0.2
0.4
5.8
29.1
34.1
0.6
41.1
0.4
<0.2
6.4
12.8
0.4
38.4
0.5
6.4
3.5
89.6
The degradation of DDT proceeded in approximately the same manner in
the presence of the soil mix as it did without the organic material. Clearly,
the soil mix has produced no significant diminution of the degradation re-
action.
Although the preceding results show that the DDT reduction by zinc was
not adversely affected by the presence of an organic planting mix, it
remained to be established that the reaction could be satisfactorily
carried out in soil. An initial problem was the selection of a represen-
tative soil to use as a test medium.
Discussions with the Department of Agriculture, Soil Conservation Service
representatives in Riverside, California, led to the selection of a Greenfield
* Kellogg Gro - Mule h
71
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Sandy Loam as an appropriate representative soil for California agricul-
ture, this soil being found both in Southern California alfalfa and grain
lands as well as produce and cotton fields of the San Joaquin Valley of
Central California. Samples suitable for the laboratory study were ob-
tained from a site recently characterized in an as yet unpublished soil
survey (Reference 42). The characteristics of the test soil are given in
Table III.
The means for practically carrying out the degradation of DDT in soil
requires careful consideration. With the establishment that a small
particulate reductant was the preferred mode, the geometrical or statis-
tical factors related to practical dissemination of a pesticide and reduc-
tant can be considered.
The separate addition of the pesticide and reductant to the soil is likely
to produce a system whereby the materials are not sufficiently close to
effectively react. However, the dissemination of a spray in which the
pesticide particle and the reductant are physically attached gives good
opportunity for reaction, and indeed degradation of DDT by Zn«Cu
couple in soil has been shown by this technique. If a DDT spray were
applied to a field at a rate of 1 Ib/acre, the number of pesticide particles
per unit area and the mean distance between particles can be calculated.
In this calculation, five pesticide particle sizes are shown. Insecticide
dusts generally range from 1 to 10 p- in diameter. In a recent paper,
Himel (Reference 43) indicated that 20 p- was an optimum size for insecti-
cide spray droplets. A 20 p- droplet containing 1% solids (pesticide) if
dried down to a single particle would theoretically yield a 4. 3/± sphere.
Similarly, a 100M droplet, typical of boom sprayers and spray blowers
(Reference 44), when dried to 1% of its volume would yield a 21. 6 p-
particle (although it is more likely that several smaller particles would
be formed). A 100^- particle is also shown in the calculations as an
extreme value. The results of the calculations follow:
Pesticide
Particle
Dia, M
1
4.3
10
21.6
100
Particle
Density,
P article s/cm^
3 x
6x
3 x
3 x
10
10
10
1. 3 x 10"
Mean Distance
Between
Particles, p-
2.8
25
88
280
2800
Mean Distance
Between Particles,
Particle Diameters
2.8
5.7
8.8
13
28
Commercial zinc and aluminum powders approximately 5 p- in diameter
are available, and indeed most of the studies with zinc dust have used a
nominal Sp. dia. material. Hence, the reductant particle and an elemental
pesticide particle of roughly the same size might be expected in field
treatment. Since in random distribution the distance between particles is
about 25p- , the likelihood of diffusion and reaction is small. Hence, it
was believed that the best opportunity for reaction would lie in the use of
an integrated particle of reductant coated with or in physical proximity to
the pesticide. This approach has received major attention. It has been
found that 5p. zinc dust suspensions could be readily sprayed with an air
blast atomizer.
72
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TABLE in
SELECTED CHARACTERISTICS OF GREENFIELD SANDY LOAM
USED IN SOIL STUDIES
Size Distribution, %
Sand 2-0.05 mm 79.8
Silt 0.05 -0.002 mm 14.4
Clay <0.002 mm 5.8
Size Distribution, Sand
Very coarse 1-2 mm 18. 8
Coarse 0.5-1 mm 24. 9
Medium 0. 25 - 0. 5 mm 12.7
Fine 0.1 -0.25mm 17.1
Very fine 0. 05 - 0. 1 mm 6. 3
Gravel (>2 mm), % 2.0
Moisture, %, held at tension, bar
1/10 12.3
1/3 8.3
15 2.5
Saturation 21.9
PH
Saturated paste 6. 4
1/10 soil-water suspension 6.8
Cation exchange capacity (NaOAc)
Meq/100 g soil 5.2
Extractable'cations, meq/100 g soil
Ca 3.1
Mg 1.0
H 2.0
Na 0.2
K 0.4
Base Saturation, % 70. 0
Organic Carbon, % 0. 55
73
-------
The degradation of DDT in soil was examined by this technique. In the
initial series, soil in 2 sq. ft. flats was treated with DDT at the rate
of 1 Ib DDT/acre. Three samples were treated in an initial test. In
one test, a suspension of the DDT (emulsifiable concentrate) and zinc-
copper couple was sprayed onto the soil, followed by acidification with
dilute acetic acid. In the second test, a solution of sulfamic acid was
used to acidify the reaction. In the third test, the DDT was deposited
onto zinc dust particles, and the material was then applied to the soil.
Reaction was then initiated by acidifying with an acetic acid spray.
Specifically, the DDT in acetone solution was slurried with zinc powder
and the couple formed by addition of Cud? solution. The suspension was
then dried, and suspended in water to which Triton X-100 surfactant had
been added. This suspension was then sprayed onto the soil. The three
samples were exposed to an out-of-doors atmosphere for 4 days and were
then extracted and analyzed. The test flats were subjected to an unex-
pected heavy rain (~ 2. 5 in.) so some DDT may have been washed away
in this test.
However, it is evident that significant reduction occurred in the third
sample, where a better opportunity for reaction was likely, according
to the above calculation. The dissemination of the pesticide and re-
ductant where contact occurs by chance (flats 1 and 2) led to significantly
less degradation of the DDT, giving only a trace of the product DDEt.
The results for the principal products follow:
Analysis, %, after 4 days out-of-doors exposure*
Spray DDT + Zn- Cu Particles
Retention DDT-Zn-Cu
Product Time, Min +HOAc + Sulfamic Acid Particle
DDEt 7.8 trace trace 21.4
12.0 7.0 7.4 5.1
DDE 15.4 27.3 26.2 27.0
DDD 17.8 10.2 5.4 9.0
DDT 20.8 55.6 61.1 10.7
29.4 - - 20.8
Following these tests, a confirmatory test was run employing the system
whereby the DDT was formed into an integral particle with the zinc-copper
couple and the dispersed DDT-reductant was sprayed onto the soil. Three
samples were examined, after 4 days, 7 days and 14 days out-of-doors
exposure. Specifically, 0.05 g DDT (1 Ib/acre on 2 sq ft flat) in acetone
solution was added to 1 g of Zn-Cu couple, the solvent was removed,
forming the DDT-coated reductant couple. The DDT-reductant particles
were then dispersed in water to which a surfactant had been added to aid
dispersal (Triton X-100), and the material was sprayed onto the soil
using an air-blast type atomizer. The acidity was supplied by spraying
the soil with dilute (0. 5N) acetic acid. Results of the assay of the principal
products after 4 days out-of-doors exposure follow:
* Temperature range: daily maxima 60-87°F, daily minima 48-58°F
Average radiant energy (Univ. Calif. Riverside Station) 495 gm cal/cm*
range 69-656
74
-------
Product Analysis, %
DDEt 35.4
DDE 20.3
ODD 24. 7
DDT 10.1
The results after 7 days and 14 days are in general agreement with these
results, although severe background interferences from the soil fractions
have made a precise quantitation difficult. It is important to note, however
that about 90% of the DDT has been destroyed, giving DDEt as the princi-
pal product. An adjustment of the acidity, providing the small but re-
quisite acidity at the reaction site, is expected to remove the DDE found
in this sample. It is expected, too, that the DDD will be consumed on
continued reaction. Although the 7 day and 14 day results are impossible
to quantitate because of interferences, it does appear that the amount
of DDEt present may be decreasing with time. This may suggest a
leaching or evaporation of this product. This result must be carefully
determined in further experiments.
75
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SECTION VIII
REACTIONS IN WATER
Reduction of DDT in Water
The application of the reductive technique for the degradation of DDT
in waters was considered in a series of experiments. One potential
application of the reductive degradation technique is with the effluent
of a DDT plant in which a stream containing 100-1000 ppm of DDT may-
be discharged at a nominal temperature of 77°C.
In a test of the zinc-copper reductive system, 1 g of recrystallized DDT
as a 25% emulsifiable concentrate was added to 2 1 of water. Then zinc-
copper couple prepared by the addition of 1 meq CuC^ to 1 g technical
zinc powder was transferred to the reaction flask with 10 ml of acetone,
and the suspension was made acid with 1 ml of concentrated sulfuric
acid (solution approximately 0. 018 N in t^SO^.); the reaction was car-
ried out with stirring for 1 hr at 75-77°C. The results of the assay
follow:
Retention Analysis, %, after 1 hr Reaction
Component Time, min at 75-77°C
DDEt 7.8 75.3
11.8 0.4
12.8 3.3
DDMS 13.8 10.5
15.0 1.2
ODD 17. 6 9. 3
DDT 20.8 <0. 2
This test indicated that the 1 hr reaction reduced the DDT level from an
initial value of 421 ppm to about 1 ppm with nearly complete conversion
to DDEt. Additional reaction time could be expected to reduce the DDT,
DDD, and DDMS levels to even lower values.
In further tests of this reaction, a comparison was made between a
sample reduced with zinc dust, a sample in which equivalent acidity
was produced by the addition of HC1 rather than E^SO^, and a test in
which technical grade DDT (1 g) was dissolved in 5 ml of chlorobenzene,
rather than being introduced as the emulsifiable concentrate. The Zn« Cu
reductant prepared as above was employed when the DDT was added to
chlorobenzene, and when the solution was made acid with HC1. The re-
sults follow:
77
-------
Com-
ponent
DDEt
DDMU
DBMS
DDD +
o, p'-DDT
DDT
Retention
Time, min
5.6
6.4
7.8
11. 0
12. 0
12.8
14.0
15. 0
17.8
21. 0
Analysis, %, after 1 hr Reaction at 75-78°C
Zn HC1 Chlorobenzene
Reductant Acidity Soln. of DDT
63.0
0. 2
0.2
5.5
8. 6
0.8
17.7
3.8
0. 1
80.4
0. 1
2.4
8.7
0.6
7.7
0.6
0.4
79.0
0.2
0.2
2.2
4.0
6.4
7. 1
These data again illustrate the importance of the use of the zinc-copper
couple, compared to reduction with zinc alone. Reduction was efficient
with both HC1 acidity and the chlorobenzene addition of technical DDT;
indeed, both of these conditions appear to give slightly greater conver-
sion to DDEt with less DDD or DDMS intermediate products.
Atomic absorption analyses for zinc in the waters reveals a zinc level
relatively proportional to the extent of reaction.
Reactants
DDT emuls, Zn- Cu, H2SC>4
DDT emuls, Zn- Cu, HC1
Tech. DDT in chlorobenzene, Zn. Cu,
DDT emuls, Zn,
Zinc in Solution,
% of Zn added
H-SO.
94
70
72
60
A series of tests were initiated in order to obtain information on the
rate of reduction of DDT in water with the zinc-copper couple. In these
tests, a two-liter sample of water was made to about 500 ppm with the
emulsifiable DDT, 1 g of the Zn« Cu couple was added, and the solution
made 0. 018 N in HC1. The K^actants were stirred continuously during
the reaction. Periodically, 100 ml samples were withdrawn, extracted
with 85% hexane-15% methylene chloride and assayed for DDT and de-
gradation products by gas chromatography. The aqueous phase was
analyzed for zinc and copper by atomic absorption. The results of
the gas chromatography assays follow:
78
-------
Com- Retention Assay, %, after Reaction, hrs, at 23 C
Time, min
7.8
9.8
11.6
12.8
14.0
15.0
16.0
17.8
21. 0
1/4
9.7
-
-
1.3
0.5
1.7
-
6.7
80.3
33. 2
-
<0. 1
1.5
2.7
0.8
-
21.4
40.5
2
43. 5
-
<0. 1
1.8
4.7
0.3
0. 1
31.5
18. 0
4
53.5
0. 1
0. 1
1.7
4.5
0.2
0. 2
30.5
9.0
24
49.8
0.4
0.2
2.3
4.6
0.4
0.2
34.9
7.3
175
61.6
1.3
1.3
2.9
2.4
1. 1
-
19.7
9.2
DDEt
DDMU
DDMS
DDD
DDT
Analysis of the aqueous phase for soluble zinc and copper yielded the
following results:
Reaction Soluble Zinc, Soluble Copper,
Time, hrs ppm ppm
1/4 145 2. 0
1 257 2. 2
2 347 2. 5
4 415 5. 1
8 485
The soluble zinc assay results appear to reasonably fit a first-order
reaction rate equation.
While the test shows that substantial degradation of the DDT to DDEt
occurs in 4 hr at ambient temperature, the observation that the re-
action has not gone to completion suggests that an improvement in
either method of contacting the DDT and reductant (e. g. , packed bed),
or a change in reaction conditions (increased reductant or change in
pH) may be necessary for improved efficiency of the reaction.
Reduction of DDT Plant Waste Samples
Other tests were conducted with waste effluent from DDT manufacturing
plants. In the first test, a process stream containing about 16% solids
was treated with the zinc-copper couple. The assay of the material*
before treatment follows (minor peaks are neglected):
*Also contains 16% particulate matter, chlorosulfonic acids, and other
waste material, some of which are apparently reactive with the zinc-
copper couple.
79
-------
Component Concentration, mg/1
p,p' DDT 394
o,p' DDT 181
p, p1 DDE 497
o, p' DDE 44
In this test, a 2 jH sample of the waste material was treated with 1 g
of Zn. Cu couple. The sample was brought to pH 2. 1 (sulfuric acid)
and the reaction was carried out at 50°C (the temperature at which it
is held in the plant). The assay for the major peaks follows:
Assay, mg/JL, after Reaction, hrs, at 50 C
~0 174 I 2 4 7 24
0 19 19 23 19 20 22
* r
P»p'
o,P'
P»P'
P.P1
P.P1
-DDEt
-DDE
-DDE
-DDD
-DDT
V
+
+
/
o,p'
o, p'
-DDD
-DDT
0
44
497
181
394
52
36
380
113
262
— ^
56
40
498
166
298
56
41
484
161
283
~ *
73
41
541
177
264
64
41
446
120
296
65
46
552
180
292
These tests reveal several interesting points. First, the appearance
of the product bis(p-chlorophenyl)ethane (p, p'-DDEt), and apparently
also the o, p1 isomer, in all samples after 15 min or longer reaction
indicates strongly that the desired degradation of DDT can be achieved
in the crude plant effluent, although the conditions for effective reac-
tion must be established from further studies. Secondly, the lack of
complete destruction of DDT suggests that the reagent was consumed
early in the reaction, or was in some manner inactivated by the mate-
rial in the crude waste effluent. The large amount of DDE (bis(chloro-
phenyl)-dichloroethylene) did not appear to have been substantially re-
duced under the conditions employed. The large amount of solids in
the samples made extraction and handling difficult, factors undoubtedly
responsible for the larger -than -de sired scatter in the analyses. The
gas chromatographic analyses were made on concentrates of hydro-
carbon extracts from the waters; no attempt was made to clean up the
samples by column chromatography, etc. , before analysis.
A second sample was treated using a larger quantity of reagent. In
this test, 10 g of reductant was used per 2 1. sample; other conditions
remained the same.
80
-------
Assay,
0
130
-
75
746
65
-
mg/j0, after Reaction time,
hrs, at 50°C
1/4 6
262 115
53 143
170 95
480 449
39 41
20 61
Product
p,p'-DDT
p, p'-DDEt
p, p'-DDD + o, p'-DDT
p,p'-DDE + o, p'-DDD
o, p'-DDE(?)
o, p'-DDEt(?)
Substantially greater production of the principal products p,p'- and
o, p'-DDEt were shown in these tests, although complete consumption
of the DDT was not achieved. The substantial reduction in the peak
ascribed to p, p'-DDE and o, p'-DDD suggests substantial reduction
of these components. It was further observed that the character of
the black mass changed with continued reaction, and indeed extraction
of the samples was somewhat easier as the reaction proceeded. It
would appear that the continued reaction may have resulted in some
reduction of the large amount of solids present in this crude stream.
The high solids and attendant handling problems again resulted in
larger-than-desired sample-to-sample scatter.
A low concentration DDT plant waste effluent was also examined. A
2. 5jfi sample was reacted at 75°C with 1 g Zn. Cu couple in a stirred
flask. Sulfuric acid was used to adjust pH to 2. 1, initially. Samples
were withdrawn periodically, extracted with 85% hexane-15% methylene
chloride, concentrated and analyzed.
Assay, mg/j2, after Reaction time, hrs at 75 C
0 T/4 2 7
p, p'-DDT
p, p'-DDEt
o, p'-DDEt(?)
p, p'-DDD + o, p'-DDT
p, p'-DDE + o, p'-DDD
0.90
0. 03
0. 14
0.06
0.84 1.20
0.22 0.28
0. 10
0. 10
0. 11
2.53
0.53
0.24
These results show that the DDT was being converted to the principal
product DDEt. The increasing amount of DDEt with continuing reaction
may indicate further reaction and extraction of DDT attached to par-
ticulate matter which did not show up in the initial analysis. The
p, p'-DDEt produced after 7 hrs reaction is equivalent to 3. 6 ppm
p, p'-DDT in the initial sample.
Effect of pH on Reduction of DDT in Water
The tests described previously in this section have been carried out at
a pH of about 2. It had not been established that this was the optimum
pH; consequently, additional tests were made in the range pH = 1. 0 to
81
-------
pH - 5. 0. The reactions were run in 2J0 distilled water in a 3JLbeaker,
with a magnetic stirring bar to provide agitation. The pH-meter elec-
trodes were suspended in the reaction mixture and pH was controlled
within +_ 0. 1 units by adding 1. 5 N H^SCXj. from a buret during the run.
DDT (1. 00 g) was introduced as an emulsifiable concentrate in xylene
solution. One gram Zn° Cu couple was added at zero time and the en-
tire mixture was extracted with 85% hexane-15% methylene chloride
after 2 hr reaction at 25°C. The gas chromatographic analyses follow:
Analysis, %, after Reaction for 2 hr at 25 C
pH of Mixture
Product pH 1. 0 pH 2. 0 pH 3. 0 pH 4. 0 pH 5. 0
DDEt 27.2 44.0 27.7 10.4
DDMU 0.5 1.8 1.1 0.7
DDMS 0. 7 4.7 1.2
DDE 0.5 - 0.8 1.1 1.5
DDD 9.7 31.5 26.8 23.5 5.6
DDT 61.4 18.0 42.4 64.3 92.9
Reduction of DDT in Water Using a Zinc Column
The degradation of DDT in water would be facilitated if the contami-
nated water could be treated by passing it through a bed of the re-
ductant. To demonstrate feasibility, a glass tube 37 mm ID x 600 mm
was filled with a mixture of 250 g Zn- Cu couple dispersed in 750 g of
fine spherical glass beads; DDT (1. 00 g) in 2J0 of 10% aqueous acetic
acid at 25°C was passed through the reductant-filled tube during a
period of 3 hr. Effluent was collected and analyzed for products.
The effluent samples contained only traces of DDT and reduction
products. The column was first drained, then 500 ml acetone was
passed through. The acetone extracted 0. 26 g organic material having
the following composition:
Retention Analysis,
Component Time, min %
DDEt 7. 8 50. 1
DDMS 14. 0 2. 5
15.0 9.8
DDE 15. 6 0. 9
DDD 18. 0 36. 7
DDT 21.0
These results show that the Zn« Cu couple is effective as a column pack-
ing in reducing DDT, and further that the reduction products are mainly
held in the column.
82
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SECTION IX
CONTROLLED DELAYED REACTION TECHNIQUES
Although the major effort on Contract 14-12-596 has been involved in
the examination of means to effectively degrade DDT to a form harm-
less to life, limited experimentation has been -undertaken in an effort
to effectively delay the degradation reaction in a controlled manner
so that the pesticide can exercise its pest control function. Two basic
approaches were investigated. In one, the reaction delay was intro-
duced by applying a slowly-soluble coating to the reductant particle,
thus delaying the reaction until the coating had been dissolved. This
is the basic technique commonly used with the "controlled-release"
fertilizers (Reference 1). The second basic technique makes use of
a slow secondary reaction to provide an essential material for the
DDT reduction reaction.
Several types of coatings have been investigated. Zinc-copper couple
particles which are initially coated well enough so that the zinc par-
ticles will not react with dilute acid have been prepared.
One coating undergoing evaluation involves the encapsulation of the
zinc-copper couple with a thin trimethyl silyl layer. In this prepara-
tion, a sample of the zinc-copper couple was mixed with bis(tri-
methylsilyl) trifluoroacetamide; the material was then reacted to the
trimethyl silyl coating by heating at 80-90° for 1 hr, and the material
was dried by tumbling after standing for 2 days. The particles when
viewed under the microscope were found to be uniformly coated with
a thin white layer of the coating. The coating in one experiment was
about 3% by weight. When these particles were placed into dilute hy-
drochloric acid (pH 2. 5), no bubbling was noted in 2-1/2 hours, while
uncoated or poorly coated particles would react vigorously under these
conditions.
Several experiments were carried out using coatings of waxes. In one
experiment, a suspension of zinc dust in microcrystalline wax-benzene
solution was diluted with methanol and the suspension sprayed onto a
plastic-film collector. The collected "spray-dried" particles were
microscopically well-coated with a layer of about 0. 5ft thickness
(~9% wax by weight) and the particles did not react with dilute acid.
However, clumping was evident; a variation in the conditions to allow
the wax coatings to harden before collection should lead to well-
dispersed coated particles.
The precipitation of microcrystalline wax onto the surface of zinc
powder also led to the production of material non-reactive to dilute
acid but which was severely clumped. In this test, a wax-benzene
83
-------
suspension of the zinc powder was precipitated by adding methanol and
water. Each clump appeared to contain about 100 5/i zinc particles.
A phase-separation procedure for precipitation of wax onto zinc par-
ticles was also examined. This procedure also led to the production
of particles which were microscopically well-coated with microcrys-
talline wax, and which would not react with dilute hydrochloric acid.
However, the particles were clumped into masses containing 100 or
more zinc particles. In this test, a 5% solution of microcrystalline
wax in 1:1 benzene-ethanol solution was prepared with a 2-1/2% sus-
pension (w/w) of zinc dust. A 1:1 water-acetone solution was slowly
added with stirring until a white precipitate of the wax could first be
seen (11 cc of water-acetone solution added to 40 ml of benzene-
ethanol solution of the wax). The coated particles were separated
by filtration.
In other tests, zinc dust particles were fluidized by blowing air through
the bed of the zinc dust and either a wax solution in benzene or a hy-
drocarbon oil (SAE 30 oil) dissolved in benzene was sprayed onto the
particles. In neither case was the coating sufficiently impermeable
to stop reaction with dilute acid.
Tests were also carried out in which paraffin wax and sulfur coatings
were applied but in neither case were the coatings sufficiently uni-
form so that reaction of coated zinc with dilute acid would not occur.
In one test, coating with a paraffin wax was achieved by layering the
molten wax on water and dropping the zinc particles through the wax
layer; the particles would then harden in the water and could be col-
lected. The wax was kept molten (~75°C) with a heating tape attached
to the cylinder holding the wax and water. The addition of surfactant
was found necessary to reduce the water-paraffin interfacial tension
so that gravity penetration of the interface occurred.
Thin sulfur coatings were prepared by slurrying zinc particles with
a solution of sulfur in carbon disulfide and removing the solvent. A
small reaction of the zinc with dilute acid was obtained, indicating
incomplete coating. Sulfur coatings were thought to be promising
since Powell (Reference 1) showed sulfur-coated urea gave a useful
controlled-release fertilizer. However, the fertilizer coating pro-
cess involved the use of molten sufur and application of this process
to zinc would be expected to lead to a reaction with the reductant
particle.
It appears that several methods are available for relatively simply
applying a thin coating of wax or silicone to zinc particles which is
sufficiently impermeable so that reaction with dilute acid does not
occur. These coatings are all very slowly soluble, or can be eroded
from the surface, so that the zinc can be exposed for reaction after
84
-------
a given period of time. The delay time can be controlled by varying
the coating thickness. However, the important problem is in estab-
lishing the requisite coating thickness to give the desired reaction
delay.
The second general type of delay reaction is that in which a secondary
reaction is used to generate an essential reactant for the reduction
reaction. The concept that was investigated makes use of the slow
oxidation of sulfur to provide the requisite acidity in the delayed re-
action. Initial tests of this concept were made in which a mix of sulfur,
DDT and zinc dust-copper couple were exposed to an out-of-doors en-
vironment and the degradation of DDT was checked. A small amount
of DDT degradation (^5%) producing DDEt as a product was noted after
2-4 weeks' exposure. In another series of tests of this concept, a
humectant (glycerol) was added to keep the reaction moist. No DDEt
was found after 2 weeks' exposure of these samples. In this series
of tests, 1 g of DDT as a 25% emulsifiable concentrate was mixed
with 1 g of Zn« Cu couple and 2 g of sulfur flowers in 10 ml of acetone.
The slurry was mixed with 10 ml of 10% glycerol in ethanol and evapo-
rated to dryness.
85
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SECTION X
EVALUATION OF DELAYED ACTION DEGRADATION OF DDT
An examination was made of the combined system whereby the reduc-
tant particle with a coating thought to provide a reaction delay was
treated with DDT and sprayed onto soil. Samples were analyzed after
4 days, 1 week, and 2 weeks out-of-doors' exposure.
In this test, zinc-copper couple particles (nominal 5fJ. diameter) were
coated with a trimethyl-silyl coating by the process described pre-
viously. A DDT solution in acetone was added to the silyl-coated
reductant and the DDT-reductant suspension was dried. The DDT-
coated reductant was then dispersed in water containing Triton X-100
surfactant and sprayed onto soil. The samples were prepared with 50
mg DDT/2 sq ft flat (1 Ib/acre) with 1 g of the reductant being used
per flat. The acidity was provided by spraying each soil flat with
20 ml of 10% acetic acid. The soil flats contained 1800 g of the
Greenfield sandy loam soil (see Section VII for description) to which
3% of the organic planting mix had been added. The results from
these tests follow:
Analysis, %, after Out-of-Doors
Retention Exposure, Days
Product Time, min 4 7 14
DDEt 8.0 50.9 56.3 23.4
12. 0 7. 0 5. 9 5. 1
13.6 1.8 1.7
15.2 <0. 9 <0.8
DDE 15.6 15.8 17.6 14.6
DDD 18.4 8.8 6. 7
19.5 8.8 4.2 3.2
DDT 21.0 7.0 3.4 6.3
30. 0 - 4. 2 38. 7
Several significant results were obtained from these tests. Although
the coating did not provide tlte desired delay, it is clear that the coated
reductant DDT particle will react with substantially complete destruc-
tion of DDT (DDT 93 to 96. 6% destroyed in these tests). Although the
principal product appears to be bis(p-chlorophenyl)ethane)(DDEt), a
decrease in this material was shown after 2 weeks' exposure.
As was mentioned earlier in this report, an apparent decrease in DDEt
on out-of-doors exposure may represent vaporization of the material
or leaching from the soil; the determination of the persistence of this
material in the environment will require careful study. The 14-day
87
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sample showed a substantial amount of material with a. 30 min gas chro-
matographic retention time. It is not known if this material represents
a decomposition product of DDT, or whether a decomposition product of
the coating was responsible for this peak.
A microscopic examination was made of DDT-coated reductant particles
that had been exposed to the out-of-doors environment for 4 days. While
the freshly-coated reductant particles have a white coating, these par-
ticles after exposure had turned black. Some fragments of siliceous
coating were also observed. It would then appear that either a faulty
coating was applied, that a reaction had occurred which destroyed the
coating, or that the coating could be substantially removed in 4 days
on soil. Although it was thought that the material initially tested was
impervious to 2 hr exposure to dilute acid, additional tests indicated that
the coating was imperfect as shown by reaction with dilute acid.
88
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SEC TION XI
DEGRADATIVE REDUCTION OF CHLORINATED PESTICIDES
AND CHLORINATED BIPHENYLS
The mildly acid reduction technique discovered for DDT has also been
examined for the applicability to other chlorinated pesticides and to the
degradation of polychlorinated biphenyls. Complete or substantial re-
duction was achieved in each case.
Three series of tests were carried out. In the first, reduction of a
series of chlorinated pesticides was attempted using zinc powder as the
reductant. In this series of tests, the materials toxaphene, lindane,
methoxychlor, dieldrin, Kelthane, chlordane, and Perthane were used.
In a second series of tests, the zinc-copper couple was employed for
the reduction of toxaphene, chlordane, dieldrin, endrin, aldrin and
heptachlor. In each of these tests, 1 g of the pesticide dissolved in 20
ml of acetone was reacted with 1 g of the reductant (zinc dust, or zinc
dust-copper couple), and the solution was acidified with 10 ml of 10%
acetic acid, so that the solution was 0. 5 N in acetic acid. The reactions
were carried out for 21-22 hours at 25°C. In the third series of tests,
the catalyzed zinc reduction of some polychlorinated biphenyls (PCB's)
was investigated. For these tests, 1 g of the PCB was dissolved in 20 ml
of acetone and reacted with 1 g of zinc-copper couple for 24 hours at
25°C. The solution was acidified with 10 ml of 1. 5 N sulfuric acid.
Analysis of the products of all tests was made by gas chromatography.
The results of these tests will be grouped according to general type of
material and the data for each substance discussed.
CHLORINATED HYDROCARBONS RELATED TO DDT
Kelthane - The major peak occurred at a retention time of 24. 4 min, with
trace amounts of materials with 9.8, 15.0, 18.4 and 20.8 min retention
also being present. Following treatment with zinc reductant, the major
peak at 24. 4 min disappeared, as did the trace peak at 18. 4 min. The
small peak at 9.8 min decreased 10-fold, while the 15 min peak increased
4-fold and the 20. 8 min peak 6-fold. A major product peak at 7. 6 min
appeared which is presumed to represent DDEt (since Kelthane is a
hydroxy-DDT, the degradation might be presumed to follow the same
route as DDT). The area of the 7. 6 min peak corresponds exactly with
that expected for the conversion of Kelthane to DDEt. A significant
product peak at 12.5 min was also observed, as well as trace peaks at
6. 5, 9.9 and 10.8 min.
Methoxychlor - The major peak at 25. 7 min in unreacted methoxychlor
was completely removed on zinc reduction, and a new product peak at
10. 6 min appeared. Moderate peaks at 20. 7 and 24. 2 min were also ob-
served in the unreacted standard; zinc reduction removed the 20. 7 min
peak completely and reduced the 24. 2 min peak to less than 1/4 of the
initial area. Peaks appeared at 19. 3 and 22.0 min, apparently repre-
senting the conversion of the 20. 7 and 24. 2 min materials.
89
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Perthane - The major peaks in unreacted Perthane were found at 2.4,
15. 3 and 17. 3 min. After zinc reduction, the 2.4 min peak disappeared
and the 15. 3 and 1 7. 3 min peaks decreased somewhat in size. A
moderate peak at 19. 6 min in the unreacted standard disappeared after
reduction, as well as a minor peak at 12. 6 min. A minor peak at 3. 6 min
decreased to about 1/4 of the initial area after reduction, while another
peak representing a trace product at 13. 6 min was unaffected. Product
peaks with 6.4 and 7. 3 min response times appeared.
HEXAC HLOROC YC LOHEXANE
Lindane - The lindane standard gave a major peak at 4. 2 min with a
minor 1. 5 min peak also being shown. After zinc reduction, both peaks
disappeared.
CHLORINATED CYCLODIENE PESTICIDES
Aidrin - Aldrin is a hexachloro-hexahydro-endo, exo-dimethano-
naphthalene. The unreacted aldrin sample gave a major peak at 8. 9 min
with minor response at 3.0 and 5. 1 min. After reaction with the zinc-
copper couple, the 8. 9 min peak was reduced to about one-third of the
initial area; the 3. 0 min peak disappeared, and the 5. 1 min minor peak
decreased substantially in area. Substantial product peaks with response
times of 6. 4 and 7. 3 min appeared.
Dieldrin - Dieldrin results from the epoxidation of aldrin. The gas
chromatographic analyses of unreacted dieldrin, and samples following
zinc and catalyzed zinc reduction, are given in Figure 4.
The principal peak from unreacted dieldrin had a gas chromatographic
response time of 14. 2 min; minor peaks (impurities in the commercial
product)were shown at 2. 8, 5.0, 7.2, 8.4, 15.0, 16. 5 and 21. 1 min.
Treatment with the zinc reductant decreased the major peak to 83% of
the initial value, with the formation of new peaks, representing de-
composition products, at 11.4 and 12. 7 min. The minor peaks with
2. 8, 16. 5 and 21. 1 min retention time disappeared, while those with
5. 0, 7. 2 and 8. 4 min retention appeared unaffected.
When the zinc-copper couple was used, the 14. 2 min peak, apparently
representing the major component of dieldrin, was reduced to 28% of
the initial area. The minor peaks at 2.8, 5.0, 15. 0, 16. 5 and 21. 1 min
disappeared, and the 8.4 min peak decreased to about one-fifth of its
initial area. The same product peaks as observed with zinc reduction
were found, and the product peak area for the zinc-copper couple, com-
pared to the zinc reductant, was 4. 7-fold larger at 12. 8 min and 6.4-fold
larger at 11.5 min; the 12. 8 min peak is 3- to 4-fold larger than the
11.4 min peak.
90
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Figure No. 48 Gas Chromatographic Analyses of Dieldrin,
and Dieldrin Following Reduction by Zinc
or Catalyzed Zinc
-------
Endrin - This pesticide is the endo-endo isomer of dieldrin. The major
peak with unreacted endrin was found with a 15. 3 min response time,
with somewhat smaller peaks at 17.0 and 21.2 min. After reaction with
the zinc-copper reductant, the 15. 3 min major peak was reduced to about
10% of its initial area and new product peaks at 12. 5 and 13. 8 min were
shown. Trace quantities of product material with 6. 3, 17. 4, 20. 7 and
21. 5 min retention time were also found.
Chlordane - Technical chlordane consists of about 60-75% octachlora-
hexahydro-methanoindene, with about 25 to 40% heptachloro-, hexachloro-,
and enneachloro-compounds. The standard (unreduced) sample gave a
number of gas chromatographic peaks, with no single peak giving a
major response. The peaks in order of decreasing height occurred at
11.6, 12.7, 6.9, 8.4, 6.1, 9.8 and 17.0 min. The gas chromatographic
results are in general agreement with those of Saha and Lee (Reference
45), who reported 14 peaks in the chlordane gas chromatographic
record.
Following reduction with the zinc and zinc-copper couple reductants,
significant changes in the chromatograms were observed. These
chromatograms are shown in Figure 5. and the results maybe sum-
marized.
Retention Time, Peak Area (oC Concentration) for Reduced
Min Sample as Compared to Unreacted Standard
Zinc Reductant Zn- Cu Reductant
11.6 <25% <10%
12. 7 -60% ~ 0
6.9 0 0
8.4 -25% ~0
6. 1 little change little change
9.8 -75% -60%
17.0 -10% 0
15.0 (new large re-
ductant peak
formed)
It is thus obvious that substantial reduction of chlordane has been
achieved, the peak area (proportional to concentration) appearing to
have been reduced to 10% or less (indicating ~90% or greater reduction)
for the four largest peaks in the chlordane structure.
Heptachlor - This compound is a heptachloro -tetrahydro -endometha-
noindene, and hence is related in structure to chlordane. The gas
chromatographic analyses of unreacted heptachlor, and heptachlor
reduced with the zinc-copper couple, are shown in Figure 6. The
heptachlor standard gave major peaks at 7. 3 and 12. 0 min, with trace
amounts responding at 5. 2, 13.0 and 13. 7 min.
92
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?
» • ..
Figure No0 5e Gas Chromatographic Analyses of Chlordane,
and Chlordane Following Reduction by Zinc
or Catalyzed Zinc
93
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UMW
m i- M
;;
Figure No. 6. Gas Chromatographic Analyses of Heptachlor,
and Heptachlor Following Reduction by
Catalyzed Zinc
94
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After reaction with the zinc-copper couple, the major peak at 7. 3 min
was reduced to 2% of the unreacted value, and the 12. CT min product was
reduced to 10% of the initial value; the 7. 3 min peak was about 4. 4-fold
larger initially than the 12. 0 min peak and therefore must be the major
component. The minor peak at 13. 7 min disappeared after treatment
with the reductant, but the 5.2 and 13.0 min peaks increased in area.
The 5. 2 min product was 4-fold greater and the 12. 0 min material
25-fold greater after reduction; it appears probable that these peaks
represent decomposition products.
CHLORINATED CAMPHENES
Toxaphene - Toxaphene is produced by chlorinating camphene to 67-69%
chlorine (about 8 chlorine atoms/camphene molecule).
The gas chromatographic traces for unreacted toxaphene, and toxaphene
reduced either with zinc, or zinc-copper couple, are given in Figure 7.
The standard (unreduced) sample gave a very complex gas chromoto-
graphic curve with the principal peaks, in order of decreasing height,
being observed at i6. 3, 21.2, 19.5, 18. 0 and 15. 1 min.
When the zinc reductant was used, all of these peaks disappeared and
a series of new peaks developed with retention times of 2 to 10 min.
The use of the zinc-copper couple reductant resulted in the formation
of several peaks with retention times of less than 4 min, with es-
sentially no response at longer retention times. It is clear from these
results that the use of either the zinc or zinc-copper couple appeared
to destroy the initial toxaphene structure, and that the zinc-copper
reductant appeared to give products with shorter gas chromatographic
retention times than the zinc reductant; the products obtained with the
zinc-copper couple are presumably more volatile or smaller molecules
than those obtained from zinc reduction.
EXTENT OF CHLORINATED PESTICIDE REACTION
These data show clearly that all of the chlorinated pesticides tested were
substantially or completely degraded by the zinc or zinc-copper couple
reducing systems after 21-4u: at 25°C. However, neither the extent of
degradation nor the degradation products have been identified.
In an effort to establish the extent of reaction, the soluble chloride was
extracted from the products of the reaction of the Zn- Cu couple with
toxaphene, dieldrin, aldrin, endrin, chlordane and heptachlor. In
addition, the reacted zinc in solution was determined by atomic ab-
sorption. The chloride was analyzed by a micro-potentiometric titra-
tion technique.
The water soluble chloride results follow:
95
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Figure Noe 1, Gas Chromatographic Analyses of Toxaphene,
and Toxaphene Following Reduction by Zinc
or Catalyzed Zinc
-------
Pesticide
toxaphene
chlordane
dieldrin
heptachlor
endrin
aid r in
Soluble
Chloride, g
0.425
0.205
0.106
0.169
0. 141
0.123
%of
Theoretical Chloride
61.6
29.6
19.0
25.3
24.8
21.0
These results show a substantial removal of chloride from toxaphene
( >60%), but a much smaller amount of chloride released from the
other pesticides investigated. However, molecular changes can be
made without the release of soluble chloride, and the zinc results
suggest complete reaction of the pesticides.
Soluble
Zinc
Pesticide Equiv. x 10
-2
Theoretical
Chloride
Equiv. x 10 "2
toxaphene
chlordane
dieldrin
heptachlor
endrin
aldrin
2.18
1.93
1.64
1.81
1.49
1.66
1.94
1.95
1.58
1.87
1.61
1.64
Ratio:
Soluble Zn
Tfaeor. Cl
1.12
0.99
1.04
0.97
0.93
1.01
It may be concluded that all of the chlorinated pesticides examined
have been substantially degraded by the reductive degradation tech-
nique. However, the chemically stable cyclodiene pesticides such
as dieldrin are expectedly more stable than the chlorinated camphenes
(toxaphene) or the closer relatives of DDT (Kelthane, methoxychlor).
The general applicability of the reductive degradation technique for
chlorinated pesticides is nevertheless shown.
POLYCHLORINATED BIPHENYLS (PCB'S)
PCB's - The PCB's are a series of polychlorinated biphenyls and
terphenyls chlorinated to contain 20 to 68% chlorine.
formula would be (biphenyl), (Reference 46).
The general
x = possible chlorine sites
These materials are used extensively for industrial purposes such as
heat transfer fluids, printing inks, hydraulic fluids, dielectrics, pro-
tective coatings, etc. , and hence find their way as industrial waste into
rivers, lakes and estuaries.
97
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Three samples were examined. The samples and their basic com-
position follow:
Basic Chlorine,
Material Structure %
Aroclor 1268 biphenyl 68
Aroclor 1248 biphenyl 48
Aroclor 1232 biphenyl 32
The results of the reduction of each of these samples can be described.
Aroclor 1268- The gas chromatographic structure of this compound
is complex, with at least 8 peaks being shown in unreacted Aroclor 1268.
This finding is in general agreement with Reynolds (Reference 47) and
Risebrough, et al (Reference 48); Reynolds reported as many as 14
peaks in Aroclor chromatographic analyses. However, upon reaction
with the zinc-copper couple for 24 hr at 25 C, a significant reduction
of many of these peaks was observed.
Peak Area (oC Concentration)
Retention Unreacted Reduced with
Time, Min Standard Zn- Cu Couple
22.1 0.11 0.11
24.5 0.22 0.14
26.1 0.07 0.09
28.9 1.00 0.58
31.3 0.47 0.44
32.8 0.18 0.12
35.7 1.15 0.64
37.9 0.28 0.25
It is thus apparent that the two major peaks (28. 9 and 35. 7 min) have
been reduced by 42 and 45%, indicating significant reaction. Reduction
in the area of the peaks at 24. 5 and 32. 8 min was also observed, while
no significant change appeared to be observed in the small peaks at
22. 2, 26.1, or the moderate sized peaks at 31. 3 and 37. 9 min. It is
believed that a modification of reaction conditions will provide more
extensive degradation of this material.
Aroclor 1248 - The gas chromatographic trace of this compound ap-
pears to be more complex than Aroclor 1268, at least 16 peaks being
observed in the trace of the unreacted compound. The chromatographic
structure is highly complex, with many of the peaks not being completely
resolved, so no effort was made to integrate the curve. However, the
unreacted sample analysis and the results after reduction with the zinc-
copper couple can be compared. The peaks will be listed in the order of
decreasing height.
98
-------
Peak Area(cC Concentration)
Retention of Reduced Sample
Time, Min. Compared to Unreacted Standard
8.5 ~ Same
11.6 ~ o
6.7 ~ 10%
9.3 o
5.0 ~ 10%
7.1 o
9.8 o
12. 6 ~ Same
5.6 o
13.4 < 25%
3.8 _- 0
2. 7 < 33%
29. 8 Large Product Peak Appeared
1 • 7 Small Product Peak Appeared
It is thus obvious that many of the peaks were completely, or nearly
completely, removed indicating that many of the i someric forms have
been effectively degraded by the reductant couple. Again, modification
of the reducing conditions is expected to lead to more substantial deg-
radation of this material.
Aroclor 1232 - Similar to Aroclor 1248, a complex gas chromato-
graphic trace with 15 peaks was obtained with unreacted Aroclor 1232.
The structure after reaction of the compound with the Zn- Cu reductant
can be qualitatively compared. The peaks again will be listed in the
order of decreasing height.
Peak Area (oC Concent ration)
Retention of Reduced Sample
Time, Min. Compared to Unreacted Standard
1.7 ~ Same
2.3 ~ Same
3.6 ~ 33%
1.1 ~ 50%
2.6 , ~ 25%
4.9 ~ Same
6.6 ~ 50%
3.2 ~ 33%
5.4 ~ 50%
7.0 ~ 50%
8.3 ~ Same
9.2 ~ 33%
9.6 ~ 33%
11.4 Larger (Product Peak?)
12.4 - Same
99
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Again it appears that many of the peaks have been reduced sub-
stantially in area, and it is believed that more complete reduction
can be achieved. The very complex nature of the gas chromato-
graphic trace has made the peak area comparison very difficult.
100
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SECTION XII
ANALYSIS OF STUDIES
The studies summarized in the preceding section had as their objective
the determination of the feasibility of a concept of controlled destruc-
tion of field-applied pesticides such as DDT. It will be the objective
of this section to attempt to analyze these data and determine whether
feasibility has been established.
The degradation studies have led to two basic systems for destruction
of DDT, with at least three apparently practical reductant systems.
Major emphasis was put on the catalyzed zinc reducing system. This
process has been shown to reduce DDT to the principal product DDEt
in reasonable times at room temperature. The product DDEt appears
to be a safe product to the environment on the basis of acute toxicity
data; it is believed that the product will not exhibit the reproductive
effects shown by DDE (and DDT), but this remains to be demonstrated.
A major question in determining the practicality of the degradation of
a field-applied pesticide is concerned with the means for carrying out
the reaction in the field. While many reactions can be carried out in
the laboratory, the practical application to the field may be unduly
difficult or impossible. In Section VII it was shown that the best
opportunity for reaction would appear to involve the formation of an
integral particle of DDT and the reductant. The separate application
of the pesticide and the degradative treatment would require a mi-
gration or diffusion of a soluble species (e. g. , emulsified DDT) to
the particulate reductant, and the probability of this occurring for
all of the pesticide droplets is very low. However, by forming the
reductant and pesticide into an integral particle, the probability of
reaction is made much larger and, as has been demonstrated, a
90-95% destruction of the DDT in soil was achieved in 4 days out-
of-doors' exposure. A second advantage may be seen in the integral
particle approach. Effective reduction appears to require a mildly
acidic condition. However, the integral particle concept will allow
the acidity to be added only at the point of reaction, rather than being
spread over the field, where an approximate pH 2 condition might
lead to plant damage as well as requiring an excessive quantity of
acid.
It would be well in considering the integral particle concept to de-
termine whether DDT dispersed in this form would be effective as
a pest control agent. LaMer and Hochberg (Reference 49) investi-
gated the killing properties of carefully controlled DDT aerosols on
mosquitoes and flies and concluded on the basis of aerodynamic cap-
ture, settling velocity, and related factors that a 5-10 micron aerosol
101
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was to be preferred. It therefore appears that the size of the particle
produced in the integral particle concept is in the approximate size
range for optimal pest control action; the size is in line also with more
recent studies by Himel (Reference 43), suggesting an approximate 20
micron insecticide aerosol as being optimal.
Although major effort was expended in investigating the catalyzed zinc
reductant system, the more recent results using catalyzed aluminum
or iron reductants offer a new and potentially attractive approach to
pesticide degradation. The approach is basically to produce a high
molecular weight degradation product which is not lipoid soluble.
Hence the material would presumably not be accumulated by life
forms in fatty tissues. Further advantages of this potential process
include a sharp decrease in the calculated amount of reductant metal
required, and the release of different metal ions as reduction products.
Some of the factors involved in a comparison between the three reduc-
tant systems can be tabulated:
Principle:
Zn« Cu
Couple
Remove chlorine
to form non-toxic
product
Al-Cu
Couple
Forms insoluble
non-reactive
product
Fe- Cu
C ouple
Forms in-
soluble,
non-re active
product
Theoretical:
equiv. reductant/
mol DDT
Theo. Cost*
cents/lb DDT
Theor.
Ib metal ion/lb
DDT
C one entr ati on
Effect
5.5
0.28
Has been shown
effective at 1
ppm DDT in
water
1. 0
0. 025
Probably free-
radical mecha-
nism; may re-
quire concen-
tration for re-
action in water
0. 2
0.052
Same as
ALCu
couple
*Based on zinc dust at $0. 20/lb, Al powder at $0. 40/lb, Fe powder at
$0. 04/lb.
102
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The use of the aluminum and iron reductants would appear to offer no
environmental problems, and indeed the salts produced would probably
hydrolyze and the insoluble hydrous oxides be precipitated. The copper
catalyst appears to be reduced to the insoluble metallic form and would
offer no contamination problem.
The use of a zinc reductant can be further analyzed on the basis that
soluble zinc chloride would be formed. If it is assumed that DDT is
applied to a field at 1 Ib/acre, then 0. 276 Ibs of zinc is theoretically
required to react with it. If all of the zinc is soluble and were released
at the time of an irrigation equivalent to 1 in. of rain, or an equivalent
rain, and the zinc were washed into a reservoir or river with no dilu-
tion of the soluble salt, then 1. 2 mg/1 of zinc would be found. In prac-
tice, it is believed that because of water stream dilution, salt adsorp-
tion, rate of release, etc. , the amount of soluble zinc found in the
water would be much lower than 0. 1 mg/1.
The zinc ion which might be introduced into the water from the use of
the reductive degradation process for waste water treatment can be
similarly examined. If a million gallon per day water source is treated,
the theoretical zinc ion in the water as a function of the DDT level would
be as follows:
DDT level, Zinc ion in water, mg/1,
mg/1 calculated, for 1 MOD stream
1.0 0.3
0. 1 0. 03
0.01 0.003
The environmental effect of the soluble zinc resulting from DDT degra-
dation can be further analyzed.
The zinc content of water from the preceding calculations is much lower
than the 5 mg/1 permissible criteria for water supplies (Reference 50).
However, it appears that lower zinc concentrations are desired if damage
to the fish population is to be avoided.
Recent studies by Brungs (Reference 51) indicate a decreased egg pro-
duction rate of the fathead minnow when the zinc concentration of water
is raised from 0. 03 to 0. 18 mg/1. In another study, Crandall and Good-
night (Reference 52) found that 2. 3 mg/1 of zinc ion had a deleterious
effect on guppy growth and mortality.
Other studies indicate the complex nature of the toxic effect of zinc to
fish. Skidmore (Reference 53) reports the toxic effect of zinc is de-
pendent upon the species, age, acclimatization, hardness of the water,
dissolved oxygen concentration, and temperature. Similarly, Mount
(Reference 54) found that there was a relationship of pH and hardness
103
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to the zinc toxicity to minnows, the toxicity being greater at a pH of 8
and hardness of 50 ppm than at pH 6, hardness 200 ppm. The most
severe toxic effect reported in the Skidmore paper involved a referenced
test where only 46% of rainbow trout fry survived 28 days in water con-
taining 0. 01 mg/1 of zinc ion. This level is well below the zinc level
commonly found in natural waters in this country. As an example,
O'Connor, Renn and Wintner report the average zinc level in a series
of Maryland rivers was 0. 05 mg/1 and the observed zinc levels fall in
the range 0. 015 to 0. 095 mg/1 (Reference 55). These levels appear
representative of other areas of the country, according to citations in
this paper. In contrast, the Mount paper lists median tolerance limits
for the fathead minnow to zinc ion from 6. 2 mg/1 to 35. 5 mg/1, depen-
ding on pH and hardness. *
These data do not give a clear answer as to whether the use of the zinc
reductant would offer an environmental problem to fish. Potential
treatment applications of DDT plant wastes may well involve low-
volurne, high-concentration streams from which the zinc salt may be
precipitated (as hydroxide, carbonate, phosphate) as well as exten-
sively diluted before being wasted. Hence the concentration of zinc
ion entering the waters may be very low. Similarly, the soluble zinc
salts in agricultural run-off may be very low because of adsorption,
dilution, etc.
An important aspect of any program of development and evaluation of
the zinc reduction technique for degradation of field-applied pesticides
would be the measurement of the soluble zinc ion in the run-off waters.
The development of the catalyzed aluminum or iron reductant systems
would not appear to offer problems of fish toxicity under reasonable
conditions of use.
Although the insecticidal properties of the combined reductant-DDT
particle have not been determined, it would appear that the action of
the DDT should not have been affected.
In summary, it appears that the basic process for DDT degradation is
effective, that a practical means for particle dissemination and reac-
tion has been discovered, that the reactions are economically feasible,
and that the products produced by one or both of the basic processes
are expected to be harmless to life forms unless conditions resulted
in sufficient zinc ion build-up to damage fish. In short, it is believed
that the feasibility of the degradative process has been demonstrated.
"""Mount points out that his data are in disagreement with most published
work, but further states that this would appear to be because of his
use of a flow-through test system, which keeps precipitated zinc in
suspension, rather than the static test system employed by others.
It should be noted that the flow-through system would appear to be
a much better simulation of real-life behavior.
104
-------
The feasibility of reaction delay techniques can also be examined. Two
basic processes were suggested for delaying the reductive reaction, one
involving the slow solubility of a coating, the other the delayed genera-
tion of an essential ingredient for the reaction.
The use of slowly-soluble coatings such as microcrystalline wax should
provide a coating that can be readily and cheaply applied. The reaction
delay period should be controllable through the coating thickness. The
background of experience in controlled-action fertilizers suggests that
this process can be readily developed for practical use, although the
precise definition of coating thickness to delay the reaction for a given
time must be established from further studies. The effect of erosion
by soil particles with wind movement, etc. , must be established also.
Although little data has been obtained as yet on the delay technique in-
volving the slow oxidation of sulfur to provide the requisite acidity,
the concept has merit because it would provide a means for generating
the acidity at the reaction site. Soil sulfur is both a relatively cheap
material and one used extensively for agricultural purposes so that no
deleterious effect on the plant would be expected. A major problem
with this concept would appear to be in devising means to control the
reaction to give a stated delay time; the coating technique would appear
to be more readily adaptable to delay time regulation.
Although the test of the combined degradation process and delayed
action technique did not give the requisite reaction delay because of
a faulty coating, the observed 90-95% DDT degradation using the in-
tegral particle of DDT and coated reductant indicates strongly that
the reaction will go in the predicted manner, given an initially im-
pervious coating.
A further factor in establishing the feasibility of the generalized con-
cept of controlled destruction of DDT is concerned with the method of
dissemination of the material. It has been shown that the integral
DDT-reductant particle can be effectively sprayed from a conventional
air-blast atomizer. Therefore it would appear that little difficulty
should be experienced in disseminating the material from spray units
now used. Since the size range is similar, no major problems are
envisioned in formulating controiled-degrading DDT dusts.
Although this feasibility effort has been directed mainly to the appli-
cation of DDT to the field, it is believed that the efforts described in
this report show that waste treatment of DDT in water can also be
feasible, as well as the application of the reductive degradation
technique to other chlorinated pesticides and the polychlorinated
biphenyls (PCB's).
105
-------
In summary, it is believed that the studies described in this report
demonstrate clearly that a controlled destruction of field-applied DDT
is a feasible process, that the degradation can be accomplished in
soil, and that the process appears to be economically practical.
The limited studies also show the general application of the process
to the treatment of other chlorinated pesticides, and the PCB's
(polychlorinated biphenyls) industrial pollutants. The potential for
reductive treatment of waste water laden with DDT was also shown.
106
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SECTION XIII
ACKNOWLEDGMENTS
The help of Mr. Earl Shade, U. S. Department of Agriculture Soil
Conservation Service, Riverside, California; Dr. James Pomerening
and Mr. George Schmitz of the Soil Science Department of California
State Polytechnic College, Pomona; and Mr. L. E. Francis of the
Agricultural Extension Service, University of California, in locating
and obtaining the soil samples is appreciated.
The solar radiant energy data for the out-of-doors testing was pro-
vided through the courtesy of Mr. Joseph Orlando of the Department
of Horticultural Science, University of California, Riverside. Other
weather data has been supplied by various members of the Weather
Bureau Staff, Los Angeles.
The discussions with Dr. L. F. Stickel and Dr. E. Dustman of the
Patuxent Wildlife Research Center, and Dr. R. Schoettger, Dr.
B. T. Johnson and Dr. D. Stalling of the Fish Pesticide Research
Lab, Columbia, Missouri, have been helpful in assessing toxic
effects.
The support of the project by the Federal Water Quality Administration
and the help provided by Dr. H. P. Nicholson, Project Officer, and
Dr. G. W. Bailey of the Southeast Water Lab is acknowledged with
sincere thanks.
107
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SEC TION XIV
REFERENCES
1. R. Powell, Controlled Release Fertilizers, Noyes Development
Corp. , Park Ridge, N. J. , 1968.
ii
2. P. Muller, ed. , The Insecticide Dichlorodiphenyl-trichloroethane
and Its Significance. I. Physicfi and Chemistry of DDT-Insecticides,
Vol I, Basel, Stuttgart, Birkhauser Verlag, 1955, pp. 53-89.
3. J. Forrest, O. Stephenson, and W. A. Waters, "Chemical
Investigations of the Insecticide 'DDT' and Its Analogues. Part 1.
Reaction of 'DDT' and Associated Compounds, " J. Chem. Soc. ,
1946, 333-339
4. S. J. Cristol and H. L. Haller, "The Chemistry of DDT - A
Review," Chem. Engr. News, 23, 2070-2076(1945).
5. H. L. Haller, P. D. Bartlett, N. L. Drake, S. J. Cristol, et al,
"The Chemical Composition of Technical DDT, " J. Am. Chem.
Soc., 6_7, 1591-1602(1945).
6. E. E. Fleck and H. L. Haller, "Catalytic Removal of Hydrogen
Chloride from Some Substituted oC-Trichloroethanes, " J. Am. Chem.
Soc., 66_, 2095 (1944).
7. M. A. Malina, A. Goldman, L. Trademan and P. B. Polen,
"Deactivation of Mineral Carriers for Stable Heptachlor-Dust
Formulations,"!. Agr. Food Chem. , 4, 1038-1042 (1956).
8. F. M. Fowkes, et al, "Clay-Catalyzed Decomposition of Insecticides, "
J. Agr. Food CHemT, 8_, 203-210 (I960).
9. A. R. Mosier, W. D. Guenzi, and L. L. Miller, "Photochemical
Decomposition of DDT by a Free-Radical Mechanism, " Science,
164, 1083-1085 (1969).
10. H. F. Beckman and P. Berkenkotter, "Gas Chromatography of the
Reduction Products of Chlorinated Pesticides, " Anal. Chem. , 35,
242-246 (1963).
11. R. Miskus, "DDT," in G. Zweig, ed. , Analytical Methods for
Pesticides, Plant Growth Regulators, an3 Food Additives, Vol. 2,
Insecticides, New York, Academic Press, 1964, pp. 97-107.
12. I. Hornstein, "Use of Granulated Zinc Columns for Determining
Chlorinated Organic Insecticides, " J. Agr. Food Chem. , 5, 37-39
(1957). -
109
-------
REFERENCES - Continued
13. E. Romano, "DehalogenationofChlorinated.OrganicInsecticid.es
by Reduction in Acid Medium. " Annali delli Sper. Agrar (Rome),
4, 1145-1157 (1950). (CA 45 6787 i (1951)).
14. S. J. Cristol, "A Kinetic Study of the Dehydrohalogenation of Sub-
stituted 2, 2-Diphenylchloroethanes Related to DDT," J. Am. Chem.
Soc. , 6T_, 1494-1498(1945).
15. K. A. Lord, "Decomposition of DDT 1:1:1-Trichloro-2:2-di-(4-
chlorophenyl)-ethane by Basic Substances, " J. Chem. Soc., 1948,
1657-1661.
16. O. Grummitt, A. Buck and J. Stearns, "Di-(p-chlorophenyl)-acetic
Acid," J. Am. Chem. Soc., 6J7, 156(1945).
17. C. M. Menzie, "Metabolism of Pesticides, " U.S. Dept. of Interior,
Bureau of Sport Fisheries and Wildlife, Washington, D.C. , Special
Scientific Report - Wild Life No. 127, July 1969.
18. D. P. N. Satchell and R. S. Satchell, "Quantitative Aspects of the
Lewis Acidity of Covalent Metal Halides and their Organo Deriva-
tives, " Cherr^Rev^, 69, 251-278 (1969).
19. G. W. Bailey, J. L. White, and T. Rothberg, "Adsorption of
Organic Herbicides by Montmorillonite: Role of pH and Chemical
Character of Adsorbate, " Soil Sci. Soc. Amer. Proc. , 32,
222-233 (1968).
20. A. G. Oblad, T. H. Millikan, Jr., and G. A. Mills, "Chemical
Characteristics and Structure of Cracking Catalysts," Adv.
Catalysis, 3_, 199-247 (1951).
21. F. G. A. Stone, "Stability Relationships Among Analogous Molecular
Addition Compounds of Group III Elements, " Chem. Rev. , 58, 101-
129 (1958). ~~
22. A. R. Bader, "Unsaturated Phenols. IV- Crotylphenols, " J. Am.
Chem. Soc., 7% 6l64-6l67 (1957).
23. W. N. Axe, U.S. Pat. 2, 412, 595(CA 41_, 1701d (1947)).
24. E. E. Fleck and H. L. Haller, "Compatibility of DDT with Insecti-
cides, Fungicides, and Fertilizers, " Ind. Eng. Chem. , 37, 403-
405 (1945).
25. H. A. Benesi, "Acidity of Catalyst Surfaces. I. Acid Strength from
Colors of Adsorbed Indicators," J. Am. Chem. Soc., 78, 5490-
5494 (1956).
110
-------
REFERENCES - Continued
26. C. S. Marvel, et al, "Reduction Activation of Emulsion Copoly-
merization of Butadiene and Styrene: The Benzoyl Peroxide -
Ferrous Pyrophosphate System, " J. Polymer Sci. , 3, 128-137
(1948).
27. W. C. White and T. R. Sweeney, "The Metabolism of 2, 2 Bis(p-
chlorophenyl) 1, 1, 1 -Trichloroethane (DDT). I. A Metabolite from
Rabbit Urine, Di(p-chlorophenyl) Acetic Acid; Its Isolation, Identi-
fication and Synthesis, " U.S. P.H.S. Public Health Reports, 60
67-71 (1945).
28. O. Grummitt, A. Buck and A. Jenkins, "1, l-Di-(p-Chlorophenyl)-
1, 2, 2, 2-tetrachloroethane, " J. Am. Chem. Soc. , 67, 155-156
(1945).
29. W. F. von Oettingen, "The Halogenated Aliphatic, Olefinic, Cyclic,
Aromatic, and Aliphatic-Aromatic Hydrocarbons Including Halo-
genated Insecticides, Their Toxicity and Potential Dangers, "
U.S. Public Health Service Publication 414 (1955).
30. M. I. Smith, H. Bauer, E. F. Stohlman, R. D. Lillie, "The
Pharmacologic Action of Certain Analogues and Derivatives of
DDT," J. Pharmacol & Expt'l Therap. , 88, 359-365(1946).
31. P. S. Larson, G. R. Hennigar, J. K. Finnegan, R. B. Smith, Jr. ,
and H. B. Haag, "Observations on the Relation of Chemical
Structure to the Production of Adrenal Cortical Atrophy or Hyper-
trophy in the Dog by Derivatives of 2, 2-Bis-(p-Chlorophenyl)-l,
1-Dichloroethane (DDD, TDE). " J. Pharmacol & Expt'l Therap.,
115, 408-412 (1955).
32. F. A. Cobey, I. Taliaferro and H. B. Haag, "Further Observations
on Effect on Plasma 1 7-OH-Corticosteroids in the Dog of Deri-
vatives of 2, 2-Bis-(p-Chlorophenyl)-l, 1-Dichloroethane (DDD, TDE),"
Proc. Soc. Expt'l Med. Biol. , 97, 491-494 (1958).
33. R. L. Metcalf, Organic Insecticides, Their Chemistry and Mode of
Action, Inter science, New York, 1955.
34. M. C. Bowman, M. S. Schechter, and R. L. Carter, "Behavior of
Chlorinated Insecticides in a Broad Spectrum of Soil Types, " J.
Agr. Food Chem., L3, 360-365(1965). ~
35. L. F. Fieser and M. Fieser, Reagents for Organic Synthesis,
Wiley, New York, 1967. ~~
36. W. E. Parham, ed., Organic Syntheses, Vol. 44, Wiley, New York
1964, p. 32.
Ill
-------
REFERENCES - Contunued
37. J. D. Roberts, ed. , Organic Syntheses, Vol. 41, Wiley, New York,
1961, pp. 72-73.
38. A. H. Blatt, ed. , Organic Syntheses, Coll. Vol. 2, Wiley,
New York, 1943, pp. 185-186.
39. J. Bernimolin, "Insecticidal Activity of 1, 1, 4, 4-Tetra(p-
chlorophenyl)-2, 2, 3, 3-Tetrachlorobutane, " J. Amer. Chem. Soc. ,
71, 2274-2275 (1949).
40. R. Riemschneider, "No Insecticidal Activity of 1,1, 4, 4-Tetra-
(p-chlorophenyl)-2, 2, 3, 3-Tetrachlorobutane, " J. Am. Chem.
Soc., 73, 1374-1375(1951).
41. K. Brand and W. Bausch, "Reduction of Organic Halocompounds
and Compounds of the Tetraarylbutane Series. X. Compounds
of the Tetraarylbutane Series. " J. Prakt Chem. , 127, 219-239,
(1930).
42. U.S. Department of Agriculture, Soil Conservation Service,
"Soil Survey of Western Riverside County, California, " in
preparation.
43. C. M. Himel, "The Optimum Size for Insecticide Spray Droplets, "
J. Econ. Entomol. 62, 919-925(1969).
44. W. Ebeling, "Analysis of the Basic Processes Involved in the
Disposition, Persistence, and Effectiveness of Pesticides, "
Residue Reviews, ^3, 35-163 (1963).
45. J. G. Saha and Y. W. Lee, "Isolation and Identification of the
Components of a Commercial Chlordane Formulation. " Bull.
Environ. Contam. Toxicol. , 4_, 285-296 (1969).
46. Monsanto Chemical Co. , Technical Bulletin No. O/PL-311A,
"Aroclor. "
47. L. M. Reynolds, "Polychlorobiphenyls (PCB's) and Their Inter-
ference with Pesticide Residue Analysis, " Bull. Environ. Contam.
Toxicol., 4, 128-143(1969).
48. R. W. Risebrough, P. Reiche, and H. S. Olcott, "Current Pro-
gress in the Determination of the Polychlorinated Biphenyls. "
Bull. Environ. Contam. Toxicol. , 4_, 192-201 (1969).
49. V. K. LaMer and S. Hochberg, "The Laws of Deposition and the
Effectiveness of Insecticidal Aerosols, " Chem. Rev., 44, 341 -352,
(1949).
112
-------
REFERENCES - Continued
50. Federal Water Pollution Control Administration, "Water Quality
Criteria, " Washington, D. C. , April 1968.
51. W. A. Brungs, "Chronic Toxicity of Zinc to the Fathead Minnow,
Pimephales promelas Rafinesque, " Trans. Amer. Fish Soc. , 98,
-------
REFERENCES - Continued
63. H. S. Mosher, M. R. Cannon, E. A. Conroy, R. E. Van Strien
and D. P. Spalding, "Preparation of Technical DDT," Ind. Eng.
Chem. , 38^ 916-923(1946).
64. M. N. Shchukina, "Chlorination and Bromination of Acetaldehyde
and Lower Homologs, " Zhur Obshchei Khim. (J. Gen. Chem.), 18,
1653-1662 (1948).
114
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SECTION XV
PATENTS AND PUBLICATIONS
Patent applications are being prepared for the significant findings on
this program. Technical papers describing the findings on the che-
mistry of DDT will be prepared by the authors of this report.
115
-------
SECTION XVI
GLOSSARY
CHEMICAL FORMULAS OF PESTICIDES AND DEGRADATION PRODUCTS
LJ
ci-c-ci
Cl
2, 2 bis(p-chlorophenyl)-!, 1, 1-trichloroethane
ODD (TDE)
H / — \
C-/O/"CI
CI-C-CI
H
2, 2 bis(p-chlorophenyl)-!, 1-dichloroethane
DDMS
CI-C-H
H
2, 2 bis(p-chlorophenyl)-l-chloroethane
H-C-H
rt
1, 1 bis(p-chlorophenyl) ethane
DDE
CI-C-CI
2, 2 bis(p-chlorophenyl)-!, 1-dichloroethylene
DDMU (TDEE) d
2, 2-bis(p-chlorophenyl)-l-chloroethylene
DDNU
v—
H-C-H"
1, l-bis(p-chlorophenyl) ethylene
*Coding of compounds used by Menzies, "Metabolism
of Pesticides, " (Reference 17).
117
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GLOSSARY
CHEMICAL FORMULAS OF PESTICIDES AND DEGRADATION PRODUCTS
DDA
H
•r OH
Cl
bis(p-chlorophenyl)acetic acid
DBP
Cl
4, 4'-dichlorobenzophenone
DDM
Cl
bis (p-chlorophenyl)me thane
DCSt
Cl
Cl
trans 4, 4'-dichlorostilbene
DPEt
1, 1-diphenyle thane
5
'H-C-H
H
TPEt H-C Q-t
(°) (g)
1, 1, 2, 2-tetraphenylethane
;i
TTTB
(Q) a g lOJ
H-C-—C—C—C-H
rfti ci di rgi
^T
\o)
ci
1, 1, 4, 4-tetra(p-chlorophenyl)-2, 2, 3, 3-tetrachlorobutane
118
-------
GLOSSARY
CHEMICAL FORMULAS OF PESTICIDES AND DEGRADATION PRODUCTS
Kelthane
C-C1
Cl
1, l-bis(p-chlorophenyl)-2, 2, 2-trichloroethanol
Methoxychlor
Cl
2, 2-bis(p-methoxyphenyl)-l, 1, 1-trichloroe thane
Perthane
H
2, 2-bis(p-ethylphenyl)- 1, 1-dichloroe thane
HCI
Lindane
Cl H
7-1, 2, 3, 4, 5, 6-hexachlorocyclohexane
Cl
Toxaphene
Chlorinated Camphene
119
-------
GLOSSARY
CHEMICAL, FORMULAS OF PESTICIDES AND DEGRADATION PRODUCTS
Aldrin
C| H
1, 2, 3, 4, 10, 10-Hexachloro-l, 4, 4a, 5, 8, 8a-hexahydro- 1, 4-endo, exo-
5, 8-dimethanonaphthalene
Chlordane
a
a H,
1,2,4, 5, 6, 7, 8, 8-Octachloro-2, 3, 3a, 4. 7, 7a-hexahydro-4, 7-methanoindene
CJ H
Dieldrin
H
H
1, 2, 3, 4, 10, 10-Hexachloro-6, 7-epoxy-l, 4, 4a, 5, 6, 7, 8, 8a-octahydro-
1, 4-endo, exo-5, 8-dimethanonaphthalene
Endrin
1, 2, 3, 4, 10, 10-Hexachloro-6, 7-epoxy-l, 4, 4a, 5, 6, 7, 8, 8a-octahydro-
1, 4, -endo, endo-5, 8-dimethanonaphthalene
Heptachlor
Cl.
1, 4, 5, 6, 7, 8, 8-Heptachloro-3a, 4, 7, 7a-Tetrahydro-4, 7-endomethanoindene
120
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SECTION XVII
APPENDIX A
PRODUCT ISOLATION, IDENTIFICATION AND CHARACTERIZATION
An important technical problem in this investigation was the identifi-
cation of the degradation products. Two generalized approaches were
used in this study. First, degradation samples were split into frac-
tions by chromatographic or other means and the separate fractions
characterized by such techniques as infrared, nuclear magnetic reso-
nance, and elemental analyses. Secondly, where degradation processes
could be predicted, compounds were procured or synthesized for anal-
ysis and comparison with the gas chromatograph results.
Gas Chromatography Analyses
The analytical chemistry of the DDT and its degradation products was
accomplished by a gas chromatography technique. The analyses were
made with a Perkin Elmer Model 880 gas chromatograph, using a dual
flame detector in conjunction with an electron capture detector. The
chromatographic column was made of stainless steel 1/8 in. O. D. by
7 ft long. The column packing was 2% SE-30 (methyl silicone gum
rubber) on Chromasorb Q (100-120 mesh). Operating conditions in-
cluded argon carrier gas at 30 cc/min, injection block temperature
165°C, column temperature programmed from 140 to 235°C at a rate
of 2°C/min. The sample volume injected was Iftl. Standardization
curves for products of decomposition or reaction were prepared so
that quantitative reduction of the gas chromatographic data could be
achieved.
The gas chromatographic retention times were obtained for a number
of possible degradation products as an aid in identifying the materials
obtained on reductive decomposition of DDT. The results of these
measurements follow:
Retention
Material Source Time, min
1, 1-diphenylethane Synthesized 1. 7
1, 1-diphenylethylene Aldrich 1. 9
1, 2-diphenylethane Aldrich 2.0
trans-stilbene Aldrich 4. 0
bis(p-chlorophenyl)methane Eastman 5. 7
121
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Material
bis (p-chlorophenyl)e thane
4, 4'-dichlorobenzophenone (DBP)
4, 4'-dichlorobenzhyd.ro!
o,p'-DDMS
1, l-bis(p-chlorpphenyl)-
2-chloroethylene (DDMU) or (TDEE)
o, p'-DDE
2, 2-bis(p-chlorophenyl)-
1-chloroethane (p,p'-DDMS)
trans-4, 4'-dichlorostilbene (DCSt)
p, p'-DDE
o, p'-DDD
m,p'-DDD
p, p'-DDD
o, p'-DDT
p,p'-DDT
1, l-bis(p-chlorophenyl)-2, 2, 2-
trichloroethanol-1 (Kelthane)
1, 1, 2, 2-tetraphenylethane
tetraphenylethylene
p-chlorobenzoic acid
1, 1, 4, 4-tetra(p-chlorophenyl)-
2, 2, 3, 3-tetrachlorobutane
DDA
Source
Synthesized
Eastman
Pfaltz &: Bauer
Synthesized
Synthesized
Aldrich
Isolated from
DDT reduction
Synthesized
Aldrich
Aldrich
Aldrich
Aldrich
Aldrich
Eastman re-
cryst.
Rohm & Haas,
recryst.
Pfaltz &: Bauer
Aldrich
Eastman
Isolated from
DDT reduction
Aldrich
Retention
Time, min
7.8
9.8
11.3
12. 0
13. 0
13.5
14. 0
14.2
15. 6
15.9
17. 1
17.8
18. 1
21. 0
24.4
26.3
26. 5
not observed
in 47 min.
not observed
in 60 min.
not observed
in 60 min.
122
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Product Isolation Using Thin -Layer Chromatography
Good results were obtained by a technique involving thin-layer chroma-
tography of the degradation samples, physical separation of the bands,
elution of the sample from the chromatography support onto KBr discs,
and analysis by infrared spectrometry.
The technique employed either Al^Og or Kieselguhr plates (with added
AgNC>3), using a 25 0/x thick coating on 2 x 7-7/8 in. glass plates. In
one test, 30 p.1 of a sample employing 29. 1% AlC^ catalyst was placed
on a Kieselguhr plate and the bands developed with n-heptane solvent,
A total of 15 bands were formed. These bands were then scraped from
the chromatoplate and placed in small glass capillary tubes. Approxi-
mately 1 ml of acetone was then used to elute material from the Kiesel-
guhr onto KBr powder. The KBr was then vacuum dried to remove the
solvent, formed into a disc and examined in a Beckman IR-5 spectro-
meter, using micro-optics. Two major products were identified from
these samples. In one, strong bands assigned to p-phenyl groups,
halogens, and the C-CHj grouping suggest the presence of bis(p-
chlorophenyl)ethane. In another, the bands for the carboxyl group,
the p-phenyl grouping and halogens indicate the presence of DDA.
In other tests samples, in which the protonated montmorillonite and
the acid-form ion exchange resin were used as decomposition catalysts,
were examined. In both cases, strong DDT bands and weak DDE bands
were obtained by the thin-layer chromato graphic method, in agreement
with the gas chromatographic results.
Additional studies were conducted by the thin-layer chromatography
technique in an effort to characterize the products of the zinc reduction
of DDT. Analyses of samples of DDT reduced with the Zn-(NH4)2 SO4 -
96% ethanol system showed three significant bands, with Rp values of
0. 65, 0. 42 and 0. 28. These three bands were separated, and the
material was eluted from the alumina substrate with cyclohexane and
analyzed by uv spectrometry.
The uv spectra strongly suggested that the first band (R^ 0. 65) was
bis(chlorophenyl)ethane (DDEt), the second peak was tentatively iden-
tified as 2, 2-bis(p-chlorophenyl)-l-chloroethane (DDMS), and the Rp
0. 28 band appeared to be DDD. These observations would tend to con-
firm the postulated consecutive reaction system DDT — >DDD - >DDMS
- >DDEt, where the three aliphatic chlorines in DDT are reduced
stepwise.
Isolation and Identification of Reaction Products
A significant study was made with the products from a reaction in which
5 g of DDT was reduced with Zn (5 g) in refluxing (NH4)2SO4- 95%
ethanol. The reaction was carried out for 8 hrs.
123
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When a portion of the sample was evaporated to dryness, extracted with
benzene to remove inorganic salts, and crystallized from pentane, small
needle-like crystals were observed (on the side of the dish) which had a
melting point of about 45-50°C (the crystals were wet with an oil which
made a precise melting point difficult). A sample of the fine crystals
was prepared in a KBr pellet for infra-red analysis which yielded the
following significant bands:
Wave Number, X
3000
2900
1750
1670
1480
1085
1010
820
805
766
-1
Assignment
-CH3
-CH2
para-phenyl
- CH
di- substituted aromatic
and C-C1 bonding
Band Strength
weak
weak
weak
weak
strong
strong
medium
medium
The spectra suggested bis(p-chlorophenyl)ethane was the product.
A sample of bis(p-chlorophenyl)ethane was prepared, therefore, for
comparison. It was prepared by the method of Geigy (Reference 56).
A mixture of chlorobenzene and aluminum chloride was saturated with
HC1 gas and reacted with acetaldehyde at -10°C. The material was then
steam distilled to remove the excess chlorobenzene, the residue was
dissolved in ether and the product distilled. The infrared spectra of
this material appeared to match the spectra of the crystals taken from
the DDT-Zn reduction reaction mix. Hence, it may be concluded that
bis(p-chlorophenyl)ethane appears to be a product of the reductive de-
gradation of DDT.
Ultraviolet spectra of the prepared bis(p-chlorophenyl)ethane and the
crystals from the reaction mix also agreed. The spectra were also in
agreement with those published by Keller, et al, for bis(p-chlorophenyl)
ethane (Reference 57).
Since DDEt is an important product of the reductive degradation of DDT,
it was important to establish the solubility of the material in evaluating
its disposal in a waste treatment process.
124
-------
Solubility estimates were made by shaking crystals of the material in
water (double-distilled water), then removing excess DDEt by centri-
fuging at 44000 xg for 2 hr. A gas chromatographic analysis of the
water indicated solubility may be as high as 10 mg/1 (ppm).
Further treatment of the crystalline mass from the DDT-Zn reduction
reaction mix with Freon 113 was found to dissolve the body of crystals
and on cooling, crystals melting at 175°C were obtained. The Beilstein
test indicated that some chlorine was present in the material.
An examination of the literature indicates the possible identity of this
material. Forrest, Stephenson and Waters (Reference 58) found that
DDT boiled in ethanol solution with zinc and concentrated HC1 yielded
three products, DDD, bis(p-chlorophenyl)ethane, and 4, 4'-dichloro-
stilbene. The listed melting point of the dichlorostilbene is 174-178°,
in good agreement with the melting point obtained for this material
(175°C). It was further found that the material discolored bromine,
in agreement with the results of Forrest, et al, yielding crystals with
a melting point of 226°; Forrest reported a melting point of 229° for
the dibromo-dichlorostilbene, in reasonable agreement with the value
obtained. It was concluded that 4, 4'-dichlorostilbene is a reaction
product of the zinc reduction of DDT.
Forrest, et al, suggest a degradation route for DDT that appears to
be compatible with observed results. Dehalogeiiation of the DDT to
produce DDD and l-chloro-2, 2-bis(p-chlorophenyl)ethane would be
followed by a molecular rearrangement of the following type to produce
the stilbene derivative.
CHp
/v....,- vv-v \—/
4, 4' -Dichlorostilbene
The reaction of DDT with GrTgnard reagent has been shown by Awe and
Reinecke (Reference 59) to produce 4, 4-dichlorostilbene, the amount
of the stilbene increasing as the amount of the organo magnesium halide
increased.
The dichlorostilbene had a retention time of 14. 2 min as measured by
gas chromatography. This peak occurred frequently in reduced DDT
samples, especially when reaction was forced by heating. However,
other data suggested that DDMS, the monochloroethane derivative of
DDT, had a similar retention time.
125
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Additional studies were made in an effort to define the composition of
the 14 min gas chromatographic peak.
One series of tests was made with the products of a zinc-DDT reaction
after 21 days at 25°C. The sample contained 46. 7% of a material having
a 14 min retention time. The solvent was evaporated and the inorganic
salts separated with Freon 113. An attempted crystallization from pen-
tane yielded about 1% of a crystalline product with a melting point of 180°.
A mixed melting point with authentic trans 4, 4'-dichlorostilbene gave no
melting point depression.
The oil remaining (0. 615 g from reaction of 1 g DDT) was transferred
to a micro still and several fractions were separated for attempted
crystallization. Gas chromatographic analyses were made on the sepa-
rate fractions.
Still conditions:
Bath temperature, °C 115-120 115-120 118-121
Pressure, mm 0.06-0.07 .065 .07
Gas chromatographic analyses:
DDEt, % 59.3 29. 9 8.2
14 min peak, % 28.9 51.7 63.1
Although enrichment was shown on distillation, crystallization experi-
ments did not yield the pure 14 min product.
Tests were also conducted with a series of "forced" reactions. In the
first set, DDT, DDD and DDE were reacted with zinc-ace tone-ace tic
acid at reflux temperature (62°C) for 24 hours. The analyses of the
products obtained from these reactions follow:
Com- Retention Analysis, %, after Reaction for 24 hr at 62 C
ponent Time, min DDT DDD DDE
6. 8 4. 1 0. 1
DDEt 7.8 45.2 30.2
12.0 0.2 0.2
DDMU 13. 0 4. 5 - 1. 9
DDMS 14. 0 43. 3 68. 3
DDE 15.6 - - 98.1
DDD 17.8 2.7 1.2
DDT 21. 0
126
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The reaction mix from the DDD reduction was evaporated and the in-
organic salts separated by means of Freon 113. Concentration then
gave 0. 17 g of 4, 4'-dichlorostilbene and 3.45 g of a colorless oil. The
oil was fractionated into three fractions. A 1. 37 g fraction having an
approximate boiling point of 140-143°C at 0. 1 mm pressure yielded
crystals which on gas chromatographic analysis were shown to contain
92. 9% of the 14-min peak material. The crude material was crystal-
lized from cold hexane to give a product having 95% 14 min peak. The
melting point was 49-50° (corrected). Elemental analysis yielded the
following values:
Calcd. for DCSt, C^H^Cl^ % C = 67. 48 % H = 4. 02 % Cl = 28. 51
Calcd. for DBMS, C^H^l : % C = 58. 88 % H = 3.88 % Cl = 37. 24
Found: 57.3 3.54 35.5
58.3 3.56
58.9 3.72
Therefore, the 14 min peak was assigned to the mono-chloroethane de-
rivative, DBMS.
Synthesis of Postulated DDT Reduction Products
1, 1-Diphenylethane was synthesized from styrene and benzene by the
method of Spilker and Schade (Reference 60).
1, l-Bis-(p-chlorophenyl)-2-chloroethylene (TDEE or DDMU) was
prepared by the alkaline hydrolysis of DDD using the method of Haller,
et al, (Reference 61).
The establishment of 2, 2-bis(p-chlorophenyl)- 1 -chloroethane (DDMS)
as a reaction product would be aided by a comparison with the spectral
and chromatographic behavior of authentic material. Accordingly, an
effort was made to synthesize a small amount of this material.
Hamada, et al (Reference 62) have described the condensation of chloro-
benzene with chloroacetaldehyde in the presence of concentrated sulfuric
acid to produce DDMS. Their procedure was modified to correspond
with conditions that were found by Mosher (Reference 63) to give maximum
yields of DDT.
Chloroacetaldehyde (0. 1 mole) plus chlorobenzene (0. 44 mole) was
mixed with 220 g 98% H2SO4 at 4°C. Additional acid (220 g of 101%
H2SO4.) was added over a period of 4 hrs with stirring while main-
taining the temperature below 5°C. The reaction was carried out in
a 500 ml round-bottomed flask having four indentations that served as
baffles to increase turbulence. Stirring was continued for an additional
4 hrs at 4°C and the product was extracted with four 100 ml portions of
hexane at 50°C.
127
-------
The hexane solution was washed with 4% Na^CO^, followed by water,
and the hexane was allowed to evaporate in an air stream. A four gram
portion of the oily residue (16 g) was distilled using a short-path micro
still. The bulk of the material distilled in the range 140-150°C/0. 1
mm Hg. Gas chromatography indicated a mixture of two materials with
retention times of about 12 and 14 minutes. Further analysis shows that
the 14 min peak is 2-chloro-l, 1 -bis(4-chlorophenyl)ethane and the 12
min peak is the corresponding ortho-para isomer: l-(2-chlorophenyl)-
l-(4-chlorophenyl)-2-chloroethane.
The chloroacetaldehyde used in this reaction was prepared by chlori-
nation of acetaldehyde at 16-18°C using 0.4 mol Cl£ per mol of alde-
hyde (Reference 69). The resulting product was fractionated and
material boiling in the range 80-85°C/750 mm Hg was used for con-
densation with chlorobenzene.
128
-------
BIBLIOGRAPHIC: Aerojet-General Corp. , Investigation of Means for Con-
trolled Self-Destruction of Pesticides, Final Report FWQA Contract No.
14-12-596, June, 1970, 128 pp.
ABSTRACT: Laboratory studies demonstrated the feasibility of controlled
destruction of chlorinated pesticides such as DDT. The concept com-
prised (1) means to degrade DDT to a harmless form, and (2) methods
to delay the reaction for given pest-control action.
Chemical methods for degrading DDT were screened and reduction was
selected as the most promising technique. Destruction of DDT, without
forming DDE as a product, was demonstrated by mildly acidic reduction
with zinc powder. The principal product is bis(p-chlorophenyl)ethane,
DDT with all three aliphatic chlorines removed; a material stated to be
"void of the neurotoxic effects of DDT, " Catalysis of the reaction re-
sulted in complete destruction of DDT in 1 hr at 25°C and conversion to
bis(chlorophenyl)ethane in 4-8 hrs. Catalyzed aluminum or iron reduc-
tion of DDT produced tetra{p-chlo«ophenyl)tetrachlorobutane, reportedly
lipoid insoluble.
A 90-95% destruction of DDT in soil in 4 days was demonstrated with
spray-applied, integral, catalyzed zinc-DDT particles (5-micron).
ACCESSION NO.
KEY WORDS:
Pesticide Degradation
DDT
Reduction
Encapsulation
Soil
Water
Chlorinated Pesticides
Polychlorinated Biphenyls
(over)
BIBLIOGRAPHIC: Aerojet-General Corp, , Investigation of Means for Con-
trolled Self-Destruction of Pesticides, Final Report FWQA Contract No.
14-12-596, June, 1970, 128 pp.
ABSTRACT: Laboratory studies demonstrated the feasibility of controlled
destruction of chlorinated pesticides such as DDT. The concept com-
prised (1) means to degrade DDT to a harmless form, and (2) methods
to delay the reaction for given pest-control action.
Chemical methods for degrading DDT were screened and reduction was
selected as the most promising technique. Destruction of DDT, without
forming DDE as a product, was demonstrated by mildly acidic reduction
with zinc powder. The principal product is bis(p-chlorophenyl)ethane,
DDT with all three aliphatic chlorines removed; a material stated to be
"void of the neurotoxic effects of DDT. " Catalysis of the reaction re-
sulted in complete destruction of DDT in 1 hr at 25°C and conversion to
bis(chlorophenyl)ethane in 4-8 hrs. Catalyzed aluminum or iron reduc-
tion of DDT produced tetra(p-chlorophenyl)tetrachlorobutane, reportedly
lipoid insoluble.
A 90-95% destruction of DDT in soil in 4 days was demonstrated with
spray -applied, integral, catalyzed zinc-DDT particles (5-micron).
Reaction delay can be achieved with wax or silicone reductant coatings
which are slowly dissolved or eroded, or possibly slow air oxidation of
sulfur. Coatings were produced which stopped zinc -acid reaction. A
test of combined reductant - delayed action technique was made using
(over)
ACCESSION NO.
KEY WORDS:
Pesticide Degradation
DDT
Reduction
Encapsulation
Soil
Water
Chlorinated Pesticides
Polychlorinated Biphenyls
BIBLIOGRAPHIC: Aerojet-General Corp. , Investigation of Means for Con-
trolled Self-Destruction of Pesticides, Final Report FWQA Contract No.
14-12-596, June, 1970, 128 pp.
ABSTRACT: Laboratory studies demonstrated the feasibility of controlled
destruction of chlorinated pesticides such as DDT. The concept com-
prised (1) means to degrade DDT tq a harmless form, and (2) methods
to delay the reaction for given pest-control actf&*x
Chemical methods for degrading DDT were screened and reduction was
selected as the most promising technique. Destruction of DDT, without
forming DDE as a product, was demonstrated by mildly acidic reduction
with zinc powder. The principal product is bis(p-chlorophenyl)ethane,
DDT with all three aliphatic chlorines removed; a material stated to be
"void of the neurotoxic effects of DDT. " Catalysis of the reaction re-
sulted in complete destruction of DDT in 1 hr at 25°C and conversion to
bis(chlorophenyl)ethane in 4-8 hrs. Catalyzed aluminum or iron reduc-
tion of DDT produced tetra(p-chlorophenyl)tetrachlorobutane, reportedly
lipoid insoluble.
A 90-95% destruction of DDT in soil in 4 days was demonstrated with
spray-applied, integral, catalyzed zinc-DDT particles (5-micron).
Reaction delay can be achieved with wax or silicone reductant coatings
which are slowly dissolved or eroded, or possibly slow air oxidation of
sulfur. Coatings were produced which stopped zinc-acid reaction. A
test of combined reductant - delayed action technique was made using
(over)
ACCESSION NO.
KEY WORDS:
Pesticide Degradation
DDT
Reduction
Encapsulation
Soil
Water
Chlorinated Pesticides
Polychlorinated Biphenyls
-------
silanized, catalyzed zinc (5 microns)-DDT particles sprayed onto soil.
Although faulty coating prevented the desired delay, 90-95% decompo-
sition of DDT was obtained.
Effective reductive degradation of chlorinated pesticides dieldrin, en-
drin, aldrin, chlordane, toxaphene, Kelthane, methoxychlor, Per thane
and lindane, and selected polychlorinated biphenyls was shown.
Degradation of DDT in water was demonstrated, a 421 mg/1 DDT sus-
pension being reduced to 1 ppm after 1 hr reaction at 75°C.
silanized, catalyzed zinc (5 microns)-DDT particles sprayed onto soil.
Although faulty coating prevented the desired delay, 90-95% decompo-
sition of DDT was obtained.
Effective reductive degradation of chlorinated pesticides dieldrin, en-
drin, aidrin, chlordane, toxaphene, Kelthane, methoxychlor, Perthane
and lindane, and selected polychlorinated biphenyls was shown.
Degradation of DDT in water was demonstrated, a 421 mg/1 DDT sus-
pension being reduced to 1 ppm after 1 hr reaction at 75°C.
silanized, catalyzed zinc (5 microns)-DDT particles sprayed onto soil.
Although faulty coating prevented the desired delay, 90-95% decompo-
sition of DDT was obtained.
Degradation of DDT in water was demonstrated, a 421 mg/1 DDT sus-
pension being reduced to 1 ppm after 1 hr reaction at 75°C.
-------
Accexiiioti Number
Subject [-'it-It "!-.
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Aerojet-General Corporation, El Monte, California,
Environmental Systems Division
Title
Investigation of Means for Controlled Self-Destruction of
Pesticides
1 Q Authorfs)
Sweeny, Keith H.
Fischer, James R.
16
21
Project Designation
FWQA Contract No.
14-12-596
Note
22
Citation
23
Descriptors (Starred First)
^Pesticide Removal, *DDT, ^Reduction (Chemical), Chlorinated
Hydrocarbon Pesticides, Soil Environment, Waste Water Treatment
25
Identifiers (Starred First)
^Pesticide Degradation, Polychlorinatedbiphenyls.
27 Abstract Laboratory studies demonstrated the feasibility of controlled destruction of
chlorinated pesticides such as DDT. The concept comprised (1) means to degrade DDT
to a harmless form, and (2) methods to delay the reaction for given pest-control action.
Chemical methods for degrading DDT were screened and reduction was selected as
the most promising technique. Destruction of DDT, without forming DDE as a product,
was demonstrated by mildly acidic reduction with zinc powder. The principal product is
bis(p-chlorophenyl)ethane, DDT with all three aliphatic chlorines removed; a material
stated to be "void of the neurotoxic effects of DDT. " Catalysis of the reaction resulted
in complete destruction of DDT in 1 hr at 25°C and conversion to bis(chlorophenyl)ethane
in 4-8 hrs. Catalyzed aluminum or iron reduction of DDT produced tetra(p-chlorophenyl)-
tetrachlorobutane, reportedly lipoid insoluble. Reductive degradation of dieldrin, endrin,
aldrin, chlordane, heptachlor, toxaphene, and selected polychlorinated biphenyls was
also shown.
A 90% destruction of DDT in laboratory soil was shown in 4 days by this technique.
Degradation of DDT in water was demonstrated also, a 421 mg/1 suspension being re-
duced to 1 ppm after 1 hr reaction at 75°C.
Reaction delay can be achieved with wax or silyl coatings which are slowly dissolved
or eroded. Coatings were produced which stopped zinc-acid reaction.
Abstractor
Keith H. Sweeny
Institution
Aero jet-General Corporation
WR:I02 (REV. JULY 1969)
WRSIC
SEND TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C 20240
* GPO: 1969-359-33'
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