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

Abstract

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 MnO₄ ⁻ (based on manganese content) greatly accelerated the mineralization of DCP when the initial pH was below 8.5. Under these conditions MnO₄ ⁻ was reduced to Mn²⁺, which enabled homogeneous catalysis to take place. When the initial pH was above 10.1, the MnO₄ ⁻ was reduced to MnO₂, which did not promote mineralization of DCP by ozone under either neutral or alkaline conditions. Under acidic conditions, however, the addition of MnO₂ greatly enhanced DCP mineralization, the mechanism being that MnO₂ was reduced to Mn²⁺ which is a highly effective homogeneous catalyst for ozonation.

Keywords:

• catalytic ozonation
• permanganate
• pH
• mineralization

Acknowledgments

This work was supported by the Project for Creative Research at Zhejiang Academy of Agricultural Sciences, by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y507284), and by the National Natural Science Foundation of China (Grant No. 20907045).