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, Fe V  = O was the dominant reactive species that was revealed by the generation of dimethyl sulfone from dimethyl sulfoxide oxidation. The selectivity of Fe V  = 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 Fe V  = 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.