DDT, DDD, AND DDE DECHLORINATION BY ZERO-VALENT IRON

Traditionally, destruction of DDT [1,1,1-trichloro-2,2-bis(p-chlorophe nyl)ethane] for environmental remediation required high-energy process es such as incineration. Here, the capability of powdered zero-valent: iron to dechlorinate DDT and related compounds at room temperature wa s investigated. Specifically, DDT, DDD [1,1-dichloro-2,2-bis(p-chlorop henyl)ethane], and DDE [2,2-bis(p-chlorophenyl)-1,1-dichloroethylene] transformation by powdered zero-valent iron in buffered anaerobic aque ous solution was studied at 20 degrees C, with and without the presenc e of nonionic surfactant Triton X-114. The iron was successful at dech lorinating DDT, DDD, and DDE. The tares of dechlorination of DDT and D DE were independent of the amount of iron, with or without surfactant. The rates with surfactant present were much higher than without. Init ial first-order transformation rates for DDT, DDD, and DDE were determ ined. For example, the initial first-order rate of DDT dechlorination was 1.7 +/- 0.4 and 3.0 +/- 0.8 day(-1) or, normalized by the specific iron surface area, 0.016 +/- 0.004 and 0.029 +/- 0.008 L m(-2) h(-1), without and with surfactant, respectively. A mechanistic model was co nstructed that qualitatively fit the observed kinetic data, indicating that the rate of dechlorination of the solid-phase (crystalline) reac tants was limited by the rate of dissolution into the aqueous phase.