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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 in laboratory studies 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. 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% decomposition 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/l DDT suspension being reduced to 1 ppm after 1 hr reaction at 75°C.

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insecticides biodegradation ddt (insecticide)

National Agricultural Library - United States of America