Remediating pesticide contaminated soils using solvent extraction

Abstract

AbstractBench‐scale solvent extraction studies were performed on soil samples obtained from a Superfund site contaminated with high levels of p,p′‐DDT, p,p′‐DDD, p,p′‐DDE and toxaphene. The effectiveness of the solvent extraction process was assessed using methanol and 2‐propanol as solvents over a wide range of operating conditions. It was demonstrated that a six‐stage methanol extraction using a solvent‐to‐soil ratio of 1.6 can decrease pesticide levels in the soil by more than 99% and reduce the volume of material requiring further treatment by 25 times or more. The high solubility of the pesticides in methanol resulted in rapid extraction rates, with the system reaching quasi‐equilibrium state in 30 minutes. The extraction efficiency was influenced by the number of extraction stages, the solvent‐to‐soil ratio, and the soil moisture content.Various methods were investigated to regenerate and recycle the solvent. Evaporation and solvent stripping are low cost and reliable methods for removing high pesticide concentrations from the solvent. For low concentrations, GAC adsorption may be used. Precipitating and filtering pesticides by adding water to the methanol/pesticide solution was not successful when tested with soil extracts.