Development of Peroxymonosulfate Catalytic System and Photoenzymatic Catalytic System Utilizing Zn-Doped g-C ₃ N ₄ for the Degradation of Methylene Blue in Water

The excessive discharge of wastewater containing methylene blue (MB) has caused certain adverse effects on human health and daily life. This highlights the urgent need for the development of safe and environmentally friendly methods of degradation. In this study, two catalytic systems based on Zn-doped g-C 3 N 4, namely, ZCN-1%/PMS and ZCN-1%/LC, were constructed for efficient activation of peroxymonosulfate (PMS) and increased laccase stability. Experimental results show that Zn-doped g-C 3 N 4 shows much better photocatalytic activity, combined with good enzyme immobilization ability. At a catalyst dosage of 0.2 g/L, both systems were able to remove more than 97% of MB (0.2 g/L) in 30 and 60 min of irradiation, respectively. Quenching experiments and electron paramagnetic resonance (EPR) analysis further revealed singlet oxygen ( 1 O 2 ) and superoxide radicals (O 2 •– ) as the main active species in the ZCN-1%/PMS and ZCN-1%/LC systems, respectively. Based on these results, the catalytic mechanisms of the two systems are systematically elucidated in this paper. This work not only proposes new methods for PMS activation and Photoenzymatic Synergistic Catalysis but also offers feasible technical strategies for treating MB-contaminated wastewater.