Behavior of chlorpyrifos and 3,5,6-trichloro-2-pyridinol (TCP) in a sodium-dodecyl sulphate-electrokinetic soil washing system

Abstract

Chlorpyrifos (CPF) is widely used around the world as an insecticide to control various insect pests. Numerous studies have shown that CPF and its main metabolite, 3,5,6-trichloropyridinol (TCP) are potential contaminants of soils and water resources. In this work an electro-kinetic soil washing treatment with alternating polarity (EKSW-AP) using the anionic surfactant SDS (4 times CMC) in the washing solution was studied as a possible strategy for CPF remediation in soils. The experiments were performed in two types of soils applying an electric field between the electrodes of 1 V cm−1 during 15 days of operation. The main results of this work showed that SDS does not improve the possibility of mobilization of CPF and TCP in the EKSW-AP treatment, due to the low remaining concentration after its adsorption on soils. In the reference systems, without current application, the recovery of CPF was close to 100% of the added mass whereas in the EKSW-AP systems recoveries reached values near to 80%. Kinetic studies performed in untreated soils revealed only the formation of TCP without any other degradation product. Therefore, EKSW-AP process likely favored the degradation of both compounds CPF and TCP, with the formation of another more polar by-product that was obtained in the collector wells. The results of this study showed that the EKSW-AP with the application of SDS does not significantly alter the physicochemical properties of the soils.