Reductive dechlorination of tetrachloroethylene in soils by Fe(II)-based degradative solidification/stabilization

Fe(II)-based degradative solidification/stabilization (DS/S) is a modification of conventional solidification/stabilization (S/S) that uses Fe(II) as a reducing agent for chlorinated organics while immobilizing inorganic contaminants. Feasibility of the Fe(II)-based DS/S technology in treating soils contaminated with tetrachloroethylene (PCE) was tested in this study. The results of the PCE degradation experiments conducted in the presence of a humic acid suggest that natural organic matter would not significantly interfere with the degradative reaction by the Fe(II)-containing reactive species in DS/S systems. Solid-phase degradation experiments showed that the DS/S technology could effectively treat PCE in soils without substantial production of chlorinated intermediates. A pseudo-first-order rate law reasonably described degradation kinetics. The half-lives of PCE ranged from 13 to 335 days, which are within time spans allowable for typical in-situ DS/S application. Trichloroethylene (TCE) was the only chlorinated product observed in the solid-phase experiments, and its presence was generally transitory with the amount being less than 7% of the initial amount of PCE on a molar basis. A surface reaction appears to control observed PCE degradation kinetics rather than mass transfer to the reactive surface.