Iron porphyrin-TiO2 modulated peroxymonosulfate activation for efficient degradation of 2,4,6-trichlorophenol with high-valent iron-oxo species

Developing efficient catalysts with low cost and environmental friendliness for peroxymonosulfate (PMS) activation attracts broad interest. In this study, TiO2-hemin was prepared by immobilizing hemin on TiO2 using a ball milling method, demonstrating 126.9-fold enhanced catalytic degradation efficiency compared with unsupported hemin in the PMS activation system, with 92.9% of 2,4,6-trichlorophenol (2,4,6-TCP) removed in 10 min. The superior performance is attributed to the strong interaction between TiO2 and hemin, which induces the redistribution of the electron density of hemin molecules. In the TiO2-hemin/PMS system, sulfate radicals (SO4•-), hydroxyl radicals (•OH), singlet oxygen (1O2), and superoxide radicals (O2•-) were identified, which only played a minor role in the elimination of 2,4,6-TCP. Instead, high-valent iron-oxo species were proposed and identified as the primary active species. This study provides a facile strategy to enhance the activity of the biomimetic catalyst and offers insight into the catalytic mechanism of iron porphyrin with PMS activation.