Trichloroethylene and tetrachloroethylene reduction in a metallic iron-water-vapor batch system

The reduction of trichloroethylene (TCE) and tetrachloroethylene (PCE) was examined in an anaerobic batch vapor-water system containing metallic iron. Concentrations of the parent compounds and products (some of which went on to react further) were determined at discrete time intervals during the reactions by analysis of the headspace vapor. cis-1,2-Dichloroethylene, 1,1-dichloroethylene, vinyl chloride, methane, chloroacetylene, acetylene, ethylene, ethane, and C3-5 alkenes and alkanes were observed as products from both compounds. Trichloroethylene was also observed from the reduction of PCE. The masses of unreacted polychlorinated ethylenes sorbed on the iron surface were significant based upon previously determined sorption isotherms, and were incorporated in carbon and chloride recovery estimates. Final carbon and chlorine recoveries of 76% and 104%, respectively, were obtained after a 92% loss of the initial TCE. After the loss of 74% of the initial PCE, the final carbon and chlorine recoveries were 90% and 118%, respectively. Reaction pathways, which include both hydrogenolysis and reductive beta-elimination, are proposed to account for the observed products.