Factors influencing the dechlorination of organo-chlorine pesticides in soils of a contaminated site by zero-valent iron

Experiments were constructed using conventional granular zero-valent iron particles as a reducing agent to study the characteristics and the factors influencing the reductive dechlorination of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in soils from a former pesticide-manufacturing site. The results showed that zero-valent iron can effectively promote the reductive dechlorination for both HCHs and DDTs. The dechlorination rate of organochlorine pesticides was strongly influenced by the factors, such as the adding dosages of iron powder, the reaction time, with or without the surfactant, the initial pH value of the contaminated soil, and so on. The reductive dechlorination of HCHs and DDTs proceeded at different rates with the variation of the zero-valent iron dosage. The residual concentrations of DDTs were greater than those of HCHs after the reaction of the reductive dechlorination. The degradation rate of HCHs and DDTs with surfactant present were much higher than without. The reaction was favored if the initial pH was acidic.