Influence of mixed-surfactant on reductive dechlorination of trichloroethylene by zero-valent iron

Abstract

Mixed nonionic and cationic surfactants were used to enhance the reductive dechlorination rate of trichloro- ethylene (TCE) with zero valent iron (ZVI). Among tested combinations of four cationic and three nonionic surfactants, a mixed surfactant system of hexadecyl-trimethyl ammonium (CTAB) and Brij30 at a mixing ratio of 1 : 1 with 0.5 critical micelle concentration (CMC) exhibited the highest reaction rate constant, 0.0269 h −1 ; the dechlorination rate constant of TCE with ZVI in the absence of surfactant was 0.0206 h −1 . The effect of this mixed surfactant on the reductive dechlorination of TCE was investigated using ZVI in a column to simulate field conditions. Unlike batch tests, column tests of the mixed surfactant system exhibited higher and lower TCE removal as compared to a nonionic and a cationic surfactant system, respectively. Consequently, if surfactants are applied for surfactant-enhanced aquifer remediation (SEAR), the performance of a permeable reactive barrier (PRB) system using ZVI to remove the residual TCE in ground- water might be affected by surfactant types; thus, the application should be carefully considered.