Mechanistic insight into the generation of high-valent iron-oxo species via peroxymonosulfate activation: An experimental and density functional theory study

The generation of high-valent iron-oxo species via the activation of peroxymonosulfate (PMS) by Fe-N moieties has shown promise for selective degradation of contaminants, but the underlying electron-transfer mechanism remains unclear. To fill this gap, we here investigated the generation of high-valent iron-oxo species using hemin as a model Fe-N moiety-containing activator of PMS and used density functional theory (DFT) calculation to gain mechanistic insights from a molecular level. The results showed that hemin had great reactivity for the target contaminant-bisphenol A degradation; around 100% degradation was achieved after reaction for 30 min. Radicals including hydroxyl radicals, sulfate radicals, and superoxide anion radicals and singlet oxygen did not contribute to the degradation. Instead, FeV = O was the dominant reactive species that was revealed by the generation of dimethyl sulfone from dimethyl sulfoxide oxidation. The selectivity of FeV = O was demonstrated by the negligible inhibitory effects of common anions. The chemical bond and Mulliken charge analyses consistently suggested that the electron transfer from hemin led to the cleavage of O-O bond and the activation of PMS. Although we do not point out the exact pathway for the generation of FeV = O, the results from this study are expected to deepen the understanding of the interaction between PMS and Fe-containing porphyrin materials and the generation of high-valent iron-oxo species.