Dual-metal-catalyzed Fenton-like reaction on CdxZn1-xS @biochar: Mechanistic insights into sulfide-metal interactions for water purification

This study presents a sludge-derived biochar (BC)-supported Cd-Zn bimetallic sulfide composite (Cd x Zn 1-x S@BC) as a novel dual-functional platform for robust peroxymonosulfate (PMS) activation. The composite material achieves electronic modulation through Zn-induced charge redistribution, which simultaneously accelerates direct electron transfer processes and enhances sulfur vacancy concentration to promote reactive oxygen species (ROS) generation. The biochar matrix further enhances pollutant enrichment and PMS adsorption energy through hierarchical pores while mediating electron shuttling between the catalyst and PMS. Simultaneously, a synergistic catalytic stabilization mechanism was revealed: Zn promotes bimetallic valence cycling to prevent cadmium over-oxidation while simultaneously enhancing metal surface passivation, achieving a 62.8 % reduction in Cd leaching. Optimized Cd x Zn 1-x S@BC (Cd/Zn = 0.5:0.5) exhibits exceptional performance, degrading 92 % of tetracycline (TC) within 30 min. It demonstrates pH tolerance (3–11), anti-interference against coexisting ions, and retains > 85 % efficiency in real wastewater matrices. This work establishes a dual-engineering strategy coupling bimetallic synergy and biochar integration for adaptive oxidation systems in water remediation.