Reductive Dehalogenation of Trichloroethylene with Zero-Valent Iron:  Surface Profiling Microscopy and Rate Enhancement Studies

Abstract

Mechanistic aspects of the reductive dehalogenation of trichloroethylene using zerovalent iron are studied with three different surface characterization techniques. These include scanning electron microscopy, surface profilometry, and atomic force microscopy. It was found that the pretreatment of an iron surface by chloride ions causes enhancement in the initial degradation rates. This enhancement was attributed to the increased roughness of the iron surface due to crevice corrosion obtained by pretreatment. The results indicate that the "fractional active site concentration" for the reactive sorption of trichloroethylene is related to the number of defects/abnormalities present on the surface of the iron. This was elucidated with the help of atomic force microscopy. Two possible mechanisms include (1) a direct hydrogenation in the presence of defects acting as catalyst and (2) an enhancement due to the two electrochemical cells operating in proximity to each other. The result of this study has potential for further research to achieve an increase in the reaction rates by surface modifications in a practical scenario.