Carbon nanotube amendment for treating dichlorodiphenyltrichloroethane and hexachlorocyclohexane remaining in Dong-ting Lake sediment - An implication for in-situ remediation.

Abstract

Organochlorine pesticides (OCPs) were largely sprayed on the floodplain soils before the project of Returning Farmland to Lake in China, which caused contamination of sediment in Dong-ting Lake with dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) and posed threats to human health and other organisms. In this study, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) at different concentrations of 0.058, 0.145 and 0.29wt% were used to manage residual DDTs and HCHs in Dong-ting Lake sediment. The efficacy was assessed by DDTs and HCHs deriving from the aqueous equilibrium experiment and uptake in semipermeable membrane devices (SPMDs). Desorption experiment and the quiescent flux experiment were conducted as well. The results showed that DDTs and HCHs were released from sediment. The p, p'-DDT was desorbed less readily than its metabolites and similarly α-HCH was desorbed less easily than other HCH isomers from sediment. Carbon nanotubes had great effects on treating DDTs and HCHs. The effectiveness of carbon nanotube amendment was dependent on type, dose and sediment-sorbent contact time In addition, carbon nanotubes being sprinkled on the surface of sediment as a cap and being injected into sediment as a mixture were considered as two effective ways to prevent DDTs and HCHs being released from sediment. Carbon nanotubes can be potentially useful as sorbents in in-situ remediation.