Development of Fe-doped g-C3N4/graphite mediated peroxymonosulfate activation for degradation of aromatic pollutants via nonradical pathway

A new composite catalyst, i.e., Fe doped g-C3N4/graphite (Fe-CN/G), was successfully constructed to activate peroxymonosulfate (PMS) for efficient phenolic compounds (i.e., p-chlorophenol, 4-CP) degradation in the pH range of 3-10. The optimized Fe-CN/G, i.e., Fe-3.75-CN/G(5.0), was fabricated at the dosage of 3.75 mmol FeCl3 center dot 6H(2)O, 5.0 g dicyandiamide, and 5.0 mmol glucose. Fe complexed in the nitrogen pots of Fe-3.75-CN/G(5.0) was demonstrated to be the primary active site for PMS activation, and the introduction of graphite favored the exposure of more accessible active sites in Fe-3.75-CN/G(5.0), suggesting a synergistic effect between the Fe and graphite of Fe-3.75-CN/G(5.0) on 4-CP degradation. Multiple experiments confirmed that sulfate radical (SO4 center dot(-)), hydroxyl radical (HO center dot), singlet oxygen (O-1(2)) and superoxide radical (O-2 center dot(-)) exerted negligible contribution on 4-CP degradation. The in-situ Fe K-edge X-ray absorption near-edge structure (XANEX) analysis revealed a redox cycle of Fe in PMS/Fe-3.75-CN/G(5.0), suggesting the formation of high-valent iron-oxo species ( Fe-IV=O) was responsible for 4-CP degradation. In addition, PMS/Fe-3.75-CN/G(5.0) exhibited acceptable degradation of 4-CP in the presence of coexisting anions and natural organic matters (NOM). We believe this study provides new insights into the design and development of Fe-based heterogeneous catalysts for PMS-based wastewater treatment. (C) 2019 Elsevier B.V. All rights reserved.