TCE oxidation efficiency by potassium permanganate for contaminated soil remediation

Abstract

This paper presents trichloroethylene (TCE) removal efficiencies from soilpolluted matrix based on batch oxidation experiments with potassium permanganate, at laboratory scale. The influence of KMnO4 dose and the reaction time on TCE degradation were evaluated, taking into account: chloride ions generated and residual TCE in aqueous phase. The soil sample was CAHfree topsoil having the following main characteristics: pH = 7.5, humus 3.3% d.w., 2 g TCE/ kg d.w. (addition of TCE analytical reagent), 58 mg Cl- /kg d.w., 55 g Fe/kg d.w., 29 mg Pb/kg d.w. Batch tests were performed in slurry system (soil:distilled water weight ratio of 1:10), continuous stirring. Solid oxidant KMnO4 was added in the range of 4.75 g/kg d.w. (stoichiometric amount) – 220 g/ kg d.w. and reaction times were two hours, 2 days and 4 days each of them corresponding to at least two different oxidant doses. Potassium permanganate reacts with both soil organic matrix and TCE. Trichloroethylene oxidation efficiency depends on the oxidant dose and oxidation/solubilization of soil organic matrix. The conversion of organic chlorine from TCE to ionic form increased with oxidant dose. Over 60 g KMnO4/kg d.w. soil is need to obtain TCE degradation efficiency higher than 90%. At the same time, the organic load (COD, TOC) in aqueous phase increases due the solubilization of humic mater. MnO2 generated in the oxidation-reduction processes remains in the soil bulk.