Bisphenol AF degradation by persulfate activation based on Mn3O4@BiOI composite catalyst

Catalyst activation of persulfate (PS) offers unique advantages for the treatment of endocrine-disrupting chemicals (EDCs) in wastewater. In this study, Mn3O4@BiOI composite catalysts were prepared using a hydrothermal synthesis method. The catalytic performance of the catalysts toward the activation of the reactive species produced by persulfate (PS) activation was investigated, as well as the subsequent Bisphenol AF (BPAF) degradation by these reactive species. The results indicate that Mn3O4@BiOI exhibits the highest efficiency in removing BPAF from water at a doping ratio of Mn3O4 of 50%. The maximal catalyst dosage that promotes the BPAF degradation effect is 300 mg/L, and higher amounts inhibited the positive outcome; furthermore, acidic conditions also inhibited BPAF degradation. Furthermore, BPAF degradation was influenced by the presence of different anions: a certain concentration of HCO3−, the effect is promoted, the presence of Cl− and SO42− inhibits the BPAF degradation process, and NO3− has a weaker impact on BPAF degradation within the Mn3O4@BiOI/PS system. Singlet oxygen (1O2), superoxide radicals (•O2−), hydroxyl radicals (•OH) and sulfate radicals (SO4•−) are the primary active species generated in the Mn3O4@BiOI/PS system, was detected by free radical quenching assay and electron paramagnetic resonance (EPR). Based on X-ray Photoelectron Spectroscopy (XPS) analysis, these four active oxygen species act together to promote the oxidative decomposition of BPAF. Among them, SO4•−, •OH, and 1O2 play crucial roles. During the catalytic process, active substances are produced via the oxidation–reduction of Mn(IV)/Mn(III)/Mn(II) and Bi(V)/Bi(III), and oxygen vacancies (OVs) are also important in promoting the removal of organic pollutants.