Heat-Assisted Visible Light Catalytic PMS for Diclofenac Degradation: Mn-Doped g-C₃N₄ Catalysts and Synergistic Catalytic Mechanism

Different manganese salt precursor-doped g-C₃N₄ catalysts prepared by the mixed calcination method were applied in the heat-assisted visible light catalytic peroxymonosulfate (PMS) activation (Heat/Vis/PMS) system for the degradation of diclofenac (DCF). Under this Heat/Vis/PMS system, the CN-Mn-S catalyst using MnSO₄ as the manganese salt precursor showed the optimal DCF degradation efficiency (96.9%) with the fastest reaction rate (0.1607 min⁻¹). Besides, with the advantages of large specific surface area, high Mn₃O₄ generation, and good visible light absorption performance, CN-Mn-S catalyst also maintained excellent catalytic activity after five cycles. Electron paramagnetic resonance (EPR) analysis revealed that the generation of active species with relatively high contribution to DCF degradation, including generation of superoxide anion (O₂·⁻) and singlet oxygen (¹O₂), were significantly increased in the CN-Mn-S/Heat/Vis/PMS system. Meanwhile, combined with the analysis of influence factor experiments and the DCF degradation characteristics, the CN-Mn-S/Heat/Vis/PMS system was able to maintain excellent DCF degradation ability in complex environments. This work provides a new idea for the application of PMS in real environment. Graphical Abstract: (Figure presented.)