Enhanced mineralization of 2,4-dichlorophenol by ozone in the presence of trace permanganate: effect of pH

摘要

Ozonation of 2,4-dichlorophenol (DCP) in the presence of permanganate has been investigated at various levels of pH. Compared with only 40% in single ozonation, by catalytic ozonation the total organic carbon removal efficiency reached almost 95%. It has been shown that the addition of 0.5 mg L~(-1) MnO_4~- (based on manganese content) greatly accelerated the mineralization of DCP when the initial pH was below 8.5. Under these conditions MnO_4~- was reduced to Mn~(2+), which enabled homogeneous catalysis to take place. When the initial pH was above 10.1, the MnO_4~- was reduced to MnO_2, which did not promote mineralization of DCP by ozone under either neutral or alkaline conditions. Under acidic conditions, however, the addition of MnO_2 greatly enhanced DCP mineralization, the mechanism being that MnO_2 was reduced to Mn~(2+) which is a highly effective homogeneous catalyst for ozonation.