New insight into the mechanism of peroxymonosulfate activation by Fe3S4: Radical and non-radical oxidation

Sulfamethoxazole (SMX) degradation was investigated through peroxymonosulfate (PMS) activation by the synthesized flower-like Fe3S4, which showed the best performance with the highest reaction stoichiometric efficiency (7.9%). 99% of SMX (2 mg/L) was eliminated from reaction solution during 30 min with 20 mg/L Fe3S4 and 0.1 mM PMS. The main reactive oxygen species (ROS) involved in the contaminant decomposition were investigated through quenching experiments, electron paramagnetic resonance, and X-ray photoelectron spectroscopy characterization. In addition to the typical sulfate radical (SO4•-) and hydroxyl radical (HO•), it should be noted that non-radical singlet oxygen (1O2) was generated and participated in the catalytic oxidation of compounds. The degradation of SMX in the PMS alone system through non-radical pathway and in the Fe3S4/PMS system by both radical and non-radical pathways were proposed according to the detected intermediates. The ecotoxicity of SMX and its by-products were evaluated through the quantitative structure–activity relationship (QSAR) analysis. The present study provided new insight into the mechanism of organic compound removal by ROS including radical and non-radical in Fe3S4/PMS system.