In recent years, the Fenton-like (Fe2+-PMS/PS) advanced oxidation technology of persulfate activated by ferrous ions has been increasingly developed, but the difficulty of Fe3+ reduction, which stops the reaction, still restricts its large-scale application. In this study, it was found that when some organic compounds represented by bisphenol A (BPA) were mixed with Fe3+ and pristine TiO2, some surface structures could broaden the light response range of TiO2, capture visible light, and transfer the photoelectrons to Fe3+ through TiO2 for reduction, so as to achieve an infinite cycle of Fe3+/Fe2+. According to the above principle, a BPA-TiO2-Fe3+-PS composite system under visible light was constructed to degrade BPA, and its catalytic performance, catalytic mechanism, and influencing factors were discussed. The results showed that the system had outstanding catalytic performance, the degradation efficiency of BPA (50 mg·L-1) reached 93.1%, and the mineralization efficiency reached 70% within 60 min. At the same time, it verified that the system could reduce Fe3+ by the authigenic photoelectron of bisphenol A, and the steady-state concentration of Fe2+ obtained by 60 min reduction was 3.5 μmol·L-1. The main active oxidizing species in the system were sulfate radicals (SO4-[KG-*2/3]·) and hydroxyl radicals (·OH), of which the contribution rate of·OH was more than 60%. An appropriate increase in TiO2, Fe3+, and PS dosage and light intensity could improve the degradation effect. The system had the best treatment efficiency under weak acid conditions, and the degradation efficiency reached 96.5%. It also had a good effect under neutral conditions. CO32-, H2PO4-, and SO42- had a certain inhibitory effect on the system.
Keywords: Fe3+reduction; advanced oxidation of persulfate; bisphenol A; electron transfer; visible light catalysis.