Photothermal-Enhanced Degradation of Metronidazole by ZIF-67-Derived Cobalt Sulfide Activating Peroxymonosulfate Under Simulated Sunlight

Metronidazole (MNZ), a refractory nitroimidazole antibiotic, poses significant environmental risks due to its persistence in aquatic systems. In this study, a hollow-structured ZIF-67-derived CoS (ZD-CoS) catalyst was synthesized to activate peroxymonosulfate (PMS) under simulated sunlight for MNZ degradation. The ZD-CoS/PMS system achieved 91.0% MNZ removal within 10 min under light irradiation, exhibiting a kinetic rate 2.4 times faster than that in the dark, which was attributed to the photothermal effect enhancing radical generation. The mechanistic study elucidated that the degradation of MNZ was driven by the collective contribution of reactive species, namely SO 4 − ˙, ˙OH, 1 O 2 , and O 2 − ˙. This synergistic effect was primarily facilitated by the Co 2+ /Co 3+ redox cycle, which served as the core mechanism for PMS activation. Furthermore, the degradation pathways of MNZ were elucidated through LC–MS analysis, indicating processes including hydroxylation, ring cleavage, and oxidation. The catalyst also demonstrated excellent stability over four cycles with low cobalt leaching (< 0.15 mg/L). This work provides a solar-driven, catalytic solution for antibiotic wastewater treatment and offers mechanistic insight into the degradation process.