Abstract
To learn the effects of coexisting surfactants on the rates and pathways of the reductive dechlorination of chloroethylenes by zerovalent iron powder, we investigated the effects of two anionic, one cationic and two nonionic surfactants on the decomposition of tetrachloroethylene (PCE), trichloroethylene (TCE), and cis-1, 2-dichloroethylene (c-DCE). The decomposition rates of c-DCE were the slowest among these three compounds for all the solution systems. The decomposition rates of PCE were faster than those of TCE in pure water and in two anionic surfactants contained solution systems, whereas the rates were almost similar when the solution contained cationic or two nonionic surfactants. Analysis of the reaction products showed that the decomposition reactions were controlled by both β-elimination and hydrogenolysis. The concentration profiles of the starting compound and the reaction products as function of time were simulated using the decomposition rate constants of these compounds. The reactions proceeded mainly via β-elimination when the solution contained cationic or nonionic surfactants, whereas the contributions of β-elimination and hydrogenolysis were almost similar when the solution contained no surfactant or anionic surfactants.
