Abiotic transformation of DDT in aqueous solutions

Significant concentrations of chlorinated pesticides such as 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its two main transformation products, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) are still present in soil and sediment systems more than 30 years after DDT use was banned in the United States. DDT enters waterways via the runoff from industrial point sources, agricultural lands and atmospheric deposition. We evaluated zero-valent iron (Fe0), ferrous sulfide (FeS), as well as combining them with hydrogen peroxide (H2O2) as viable treatment technologies for degrading DDT in an aqueous solution. Treatment of DDT with Fe0 and FeS resulted in approximately 88% and 56% transformation of DDT within 150 h, respectively. DDE production was insignificant in all systems. The DDT removal was slower with FeS than with Fe0, but the amounts of DDD and DDE produced did not exceed baseline. Treatment with a 1:1 mixture of Fe0–FeS removed about 95% of the added mass of DDT within 4 days and generated significant amounts of DDD and minor amounts of DDMU. When small amounts of H2O2 were introduced halfway through the Fe0 and FeS treatment times, the mass of DDT decreased by 87% and 96%, respectively, within 2 days. Our results demonstrate that mixtures of Fe0–FeS in combination with H2O2 can be used for rapid and efficient removal of DDT from aqueous solutions.