Degradation efficiencies and mechanisms of trichloroethylene (TCE) by controlled-release permanganate (CRP) oxidation

Control-release KMnO4 (CRP) technology has been recently developed as an improved, highly efficient option for treating dissolved contaminant plumes of trichloroethylene (TCE) in the groundwater. In this paper, the preparation of potassium permanganate encapsulated with stearic acid by oil phase separation method and the control-release mechanism of the encapsulated permanganate in the degradation of TCE were studied. At 1:3 of the mass ratio of KMnO4 solid to stearic acid, solid KMnO4 could be loaded by stearic acid completely and only 30.9% KMnO4 was released into water from CRP after 240 h with well-controlled release efficiency. The influence of the initial TCE concentration, pH value, and inorganic oxidation agent on the release efficiency of CRP and the ICE decontamination by CRP oxidation were also investigated. Comparative study between raw permanganate and CRP has been performed to clarify the priority of control release technology in reducing the non-selective consumption of oxidant and improving the oxidation efficiency for remediation of TCE in groundwater. The experiments show that CRP could minimize non-selective consumption and self-losses, which improved the oxidant efficiency and decreased the amount of oxidant needed. The oxidant efficiency of CRP increased by 1.7-fold compared with that of aqueous KMnO4. CRP showed the well-controlled release property and high removal efficiency of TCE. The molar ratio between released KMnO4 and removed ICE ranged about 2.98-5.96, which is a little higher than the stoichiometric requirement of 2:1. CRP could be used to control TCE pollution in groundwater over a large pH range. Complete dechlorination can be achieved by oxidation when the mass ratio of release KMnO4 to TCE exceeds 3:1. (C) 2012 Elsevier B.V. All rights reserved.