Heterogeneously catalyzed binary oxidants system with magnetic fly ash for the degradation of bisphenol A

Abstract

Bisphenol A is one of the typical endocrine chemicals that can be found in many different kinds of water bodies. A heterogeneously catalyzed H2O2/peroxydisulfate system coupled with magnetite supported on coal fly ash was investigated for the degradation of bisphenol A. The activity tests results showed that the bisphenol A (50 mg/L) degradation efficiency of 60 min in the binary oxidants system can be significantly enhanced from 16.7% to 100% after the addition of catalyst ([oxidants]0 = 20 mM, [H2O2]0/[PDS]0 = 4, [Catalyst] = 2 g/L, pH = 5, T = 25 °C), while the oxidation process can be affected by solution pH, catalyst surface properties and oxidant ratios. Based on the results of quenching experiments, it was proposed that in a binary system, there were 3 radicals including hydroxyl radical, sulfate radical and superoxide radical possibly responsible for the bisphenol A degradation, and either radical may predominate over the other two depending on the adsorption behaviors on the catalyst surface as well as the radicals’ inter-conversions. The stability and reusability analysis of catalyst were carried out in 7 sequential batch studies. The negligible concentration of dissolved Fe ion in first 4 runs illustrated the dominant role of heterogeneous process, while the gradually leached Fe ion in following runs demonstrated the involvement of homogeneous process. The findings of this study strongly suggest that the heterogeneous binary oxidant system is a promising treatment technology for the abatement of bisphenol A, while the suitable oxidant ratio and solution pH are essential for making the most of the radicals.