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 25C 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/l suspension being reduced to 1 ppm after 1 hr reaction at 75C. Reaction delay can be achieved with wax or silyl coatings which are slowly dissolved or eroded. Coatings were produced which stopped zinc-acid reaction. (Author) |