Enhanced oxidation of bisphenol A by permanganate in the presence of epigallocatechin gallate: Kinetics and mechanism

Accelerated oxidation of emerging contaminants by permanganate (PM) in the presence of reducing reagents or ligands was reported in previous studies. Epigallocatechin gallate (EGCG) is a novel reagent used in water treatment, with simultaneous reducing and chelating ability. Therefore, EGCG was applied to enhance PM oxidation of bisphenol A (BPA) in this study, and showed a better performance than sulfite, hydroxylamine, EDTA, and citrate. The impacts of molar ratio of PM/EGCG, pH, dissolved oxygen, alkalinity, and natural organic matters on the performance of PM/EGCG process were investigated. The results demonstrated that optimum molar ratio of PM/EGCG was at 1:0.1, and EGCG significantly enhanced PM oxidation at pH 5-8. Dissolved oxygen and alkalinity showed inhibitory impacts on BPA degradation in PM/EGCG process, while natural organic matters have no obvious impact on the performance of PM/EGCG process. Formation of reactive Mn intermediates was confirmed using quenching experiments (with pyrophosphate) and UV-vis full scan spectra, indicating that reactive Mn intermediates were the predominant reactive species responsible for BPA degradation in PM/EGCG process. Overall, our study provides a novel and environmentally friendly alternative for enhancement of PM oxidation.