Fe-g-C3N4/reduced graphene oxide lightless application for efficient peroxymonosulfate activation and pollutant mineralization: Comprehensive exploration of reactive sites

To overcome the shortcomings of homogeneous Fe ion activating peroxymonosulfate (PMS), such as high pH-dependence, limited cycling of Fe(III)/Fe(II) and sludge production, graphite carbon nitride (g-C 3 N 4 ) is chosen as a support for Fe ions, and reduced graphene oxide (rGO) is employed to facilitate the electron transfer process, thereby enhancing catalysis. Herein, a ternary catalyst, Fe-g-C 3 N 4 /rGO, is first applied under lightless condition for PMS activation , which exhibits ideal performance for contaminant mineralization. 82.5 % of the total organic carbon (TOC) in 100 mL of 5 mg/L bis -phenol A (BPA) was removed within 20 min by the optimal catalyst named 30%rFe 0.2 CN, which shows a strong pH adaptability over the range of 3–11 compared with a common Fenton-like system. Moreover, the highly stable Fe-g-C 3 N 4 /rGO/PMS catalytic system resists complex water matrices, especially those with high turbidity . To unveil the mechanism of PMS activation and pollutant degradation , the physicochemical properties of the as-prepared catalysts are comprehensively characterized by multiple techniques. The Fe(III) contained in both the Fe-N group and α-Fe 2 O 3 component of 30%rFe 0.2 CN not only directly reacts with PMS to produce sulfate radicals ( SO 4 − ) and hydroxyl radicals ( OH), but also combines with PMS to form the essential [Fe(III)OOSO 3 ] + active complex, thereby generating superoxide radicals ( O 2 − ) and singlet oxygen ( 1 O 2 ). Among the various reactive oxidizing species, 1 O 2 plays an important role in pollutant removal , which is additionally generated by the C O moiety of the catalyst activating PMS as well as PMS self-oxidation, indicating the dominance of the non-radical pathway in the pollutant degradation process. Due to the advantages of high efficiency, wide pH adaptability and stability, the proposed lightless Fe-g-C 3 N 4 /rGO/PMS catalytic system represents a promising avenue for practical wastewater purification.