Chemical oxidation of trichloroethylene with potassium permanganate in a porous medium

The extent of oxidation of dissolved-phase and pure-phase trichloroethylene (TCE) by potassium permanganate (KMnO4) in a sandy aquifer matrix and the impact of reaction products (H+ and MnOx) on pH, metal ion leaching and permeability of the aquifer medium near TCE source zones during KMnO4 flushing were investigated using laboratory-scale column experiments. The results of three column experiments indicated that KMnO4 Completely dechlorinated TCE, evidenced by similar to 100% chloride recovery, when TCE was present in dissolved phase or pure phase in the aquifer matrix. Two other column experiments were conducted to investigate the impact of H+ and MnOx on the aquifer medium near TCE source zones. KMnO4 flushing of the aquifer medium with residual pure TCE showed significant decreases in the pH levels (e.g. from 6.7 to similar to 2.0) of the column effluents, and large quantities of MnOx precipitates were retained in the columns. The decrease in the pH levels in the columns led to an increase in the iron content of the column effluents. Two bromide tracer tests indicated that MnOx precipitates reduced approximately 20% of the pore space in the columns. In addition, characterization of MnOx by X-ray diffraction (XRD) and infrared (IR) spectroscopy demonstrated that the TCE-KMnO4 reaction yielded birnessite-type manganese oxide. (C) 2002 Elsevier Science Ltd. All rights reserved.