Phase-transfer catalysis enhanced remediation of trichloroethylene polluted groundwater by potassium permanganate

Abstract

ABSTRACT As one of the remediation reagents, potassium permanganate (KMnO4) is injected to the aquifer, degrading trichloroethylene (TCE) by chemical oxidation. This study investigated the kinetics of TCE degradation by series of batch experiments, as well as the influence of medium size. Moreover, phase-transfer catalyst (PTCs), such as pentyltriphenylphosphonium bromide (PTPP) and sodium hexametaphosphate (SHMP) were used for enhancing oxidation. The batch experimental results showed that in the absence of PTC, the removal efficiency of TCE was 36.14% and 86.79% within 4 and 30 min, respectively. However, the removal rate of TCE was up to 67.48% and 49.90% within 4 min for 15 mol% PTPP- and SHMP-added system, respectively. The results indicated that PTPP and SHMP promoted the depletion of to oxidize DNAPL TCE, but its effectiveness varied with the addition ratio of PTPP or SHMP. Its promotion was more remarkable when PTC added with a higher proportion. The alleviation of MnO2 by phosphates (, and ) or PTC in the presence of media was qualitatively investigated. Results showed that the content of MnO2 in the dissolved phase during the same reaction period decreased by PTC. Moreover, and SHMP have apparent beneficial effects of reducing MnO2 formation. The presence of aquifer media has a pH buffer and a negative influence on the reaction between TCE and the oxidant; moreover, as particle size of media decreased, the negative effect increased.