Effect of Nonionic Surfactant Tween 80 on Enhanced Solubilization of DDTs from Contaminated Site Soil

Surfactant enhanced soil washing is considered to one of the effective approaches to remove hydrophobic organic compounds from contaminated soils. Batch experiments were performed to study effects of the environment-friendly surfactant Tween 80 on solubilization and elution of DDTs from soil samples taken from a pesticide contaminated site at southern Jiangsu Province. Effects of total 9 concentration levels of Tween 80 at the range of 0～10 000 mg·L-1 were investigated in this study. The results showed that Tween 80 enhanced desorption and solubilization of DDTs from the soil remarkablely. Concentrations of DDTs in surfactant extracts followed the order:4,4'-DDT4,4'-DDD 2,4'-DDD2,4'-DDT. Desorption and solubilization of DDTs from soil at different concentrations of Tween 80 could be described by exponential decay function. Tween 80 removed significant amount of DDTs from the soil. About 72% DDTs were removed by Tween 80 at solu-tion concentration of 10 000 mg·L-1,which led to a decrease in DDTs concentration in the soil from 2 780 mg·kg-1 to 778 mg·kg-1. At lower Tween 80 concentration of 8 000 mg·L-1,removal rate of DDTs(66.7%)was a bit lower than but still comparable to the treatment of Tween 80 at 10 000 mg·L-1. Most of the Tween 80 (up to 72% for 8 000 mg·L-1 treatment)left in the soil could be removed by deionized water,which indicated less environmental and ecological risk associated with Tween 80 in the soil. Soil washing with surfactant solution of Tween 80 at 8 000 mg·L-1 ,in combination with other remediation technologies,could be one of the promising solutions to DDTs contaminated soils.