Nitrogen-Stabilized Fe–Co Nanoclusters Supported on Mushroom-Residue-Derived Porous Carbon for Peroxymonosulfate Activation Toward Sulfadiazine Degradation

Addressing the environmental persistence and ecotoxicological risks of the antibiotic sulfadiazine (SDZ) in water bodies is a pressing concern. In this study, nitrogen-stabilized Fe–Co nanoclusters supported on mushroom-residue-derived N-doped porous carbon (FeCo/NPC-800) were fabricated via a dicyandiamide-assisted pyrolysis strategy and used to activate peroxymonosulfate (PMS) for SDZ degradation. Synchrotron radiation X-ray absorption fine structure measurements and quantitative fitting indicated the coexistence of metal–heteroatom and metal–metal coordination, consistent with ultrasmall, structurally disordered Fe/Co-containing domains anchored to the N-doped carbon matrix. The FeCo/NPC-800/PMS system achieved an SDZ removal efficiency of 91.2% within 60 min, confirming that FeCo/NPC-800 can effectively activate PMS under the tested conditions. Radical-quenching experiments and electron spin resonance analysis identified sulfate and hydroxyl radicals, with sulfate radicals appearing to make the larger contribution under the tested conditions. Degradation intermediates collected at 10 and 40 min were analyzed by liquid chromatography–mass spectrometry, and three main transformation pathways were proposed: amino oxidation followed by sulfur dioxide extrusion, sulfur–nitrogen bond cleavage, and pyrimidine-ring opening. These findings provide insights into biomass-derived, nitrogen-stabilized bimetallic carbon catalysts for PMS-based treatment of refractory antibiotic contaminants.