Sulfite activation by C3N5 under visible light for metronidazole removal: Performance and mechanism

In response to the current demand for the development of efficient and stable photocatalysts for sulfite (S(IV)) activation, this study introduces C 3 N 5 to activate S(IV) under visible-light (VL) irradiation and elucidates the mechanism of the VL/C 3 N 5 /S(IV) system to degrade organic pollutants. The k obs value for the removal of metronidazole in the VL/C 3 N 5 /S(IV) system reached 0.07245 min −1 in 12 min. Subsequently, the activation mechanism of S(IV) and the generation of reactive species were studied. The results indicate that the excellent degradation performance of the VL/C 3 N 5 /S(IV) system is due to the generation of carriers in C 3 N 5 under visible light. The S(IV) reacts with photogenerated holes, producing •SO 4 - and •OH in a chain reaction. This study not only broadens the application scope of C 3 N 5 as a photocatalyst but also presents a novel S(IV) activation strategy, enriching the understanding of S(IV) activation mechanisms.