Phase-transfer catalysis applied to the oxidation of nonaqueous phase trichloroethylene by potassium permanganate

The use of potassium permanganate to oxidize chlorinated solvents has been demonstrated as an effective process for treating nonaqueous phase liquids in ground-water systems. This study evaluates the effectiveness of phase-transfer catalysts (PTCs) in enhancing the degradation rate. PTCs work by transferring permanganate ion into the nonaqueous phase when it initiates oxidative decomposition. We studied the oxidation of trichloroethylene (TCE) by potassium permanganate, conducting kinetic batch experiments in conjunction with three PTCs that varied in terms of their extraction constants and molecular structures. Using the same batch technique, we examined whether PTCs could enhance the aqueous solubility of TCE. Solubilization could also increase oxidation rates in the aqueous phase. Rates of TCE oxidation in solutions containing the PTCs and a blank were estimated separately by measuring chloride concentration and W-Vis absorbance in the aqueous phase. The enhanced rate of TCE destruction by the PTCs was reflected by an increase in the rate of consumption of permanganate ion and production of chloride ion. There was no tendency for the PTCs, however, to solubilize TCE in the aqueous phase. Therefore, the PTCs increased the rate of TCE decomposition by catalyzing permanganate oxidation in the organic phase. This study suggests that there is significant potential for testing this scheme under field conditions. (C) 2000 Elsevier Science B.V. All rights reserved.