Unlocking endogenous silicon in N-doped swine manure biochar through Si–O–C interface engineering for enhanced peroxymonosulfate activation

Bisphenol A (BPA) pollution severely threatens aquatic ecology and human health, and peroxymonosulfate (PMS)-based advanced oxidation processes are efficient for refractory organic pollutant remediation. Our previous study realized the in-situ synthesis of nitrogen-doped swine manure biochar (NBC) for enhanced PMS catalysis, yet abundant endogenous silicon in swine manure remains inert as SiO 2 and fails to contribute to catalysis, restricting the full resource utilization of livestock waste. Targeting this bottleneck, we herein develop a facile ball-milling coupled with HF etching strategy to activate intrinsic silicon on NBC without exogenous dopants. This approach converts inert SiO 2 into reactive Si–O–C interfacial sites while preserving the original nitrogen-doped carbon framework, yielding a Si modified biochar (Si-NBC). Benefiting from the synergistic effect of Si–O–C bridges and inherent nitrogen active sites, the optimized Si-NBC achieves 98% BPA removal within 20 min and 42% total organic carbon mineralization, with a rate constant 18-fold higher than pristine NBC. It performs robustly across pH 3–9, tolerates common coexisting anions, and maintains removal above 90% for 72 h in a continuous-flow reactor. Mechanistic investigations reveal a synergistic non-radical regime: singlet oxygen, generated at C–C and graphitic N sites, dominates the oxidative process, while an electron-transfer pathway, mediated by graphitic N and Si–O–C bridges, accelerates interfacial charge shuttling. Degradation intermediates exhibit markedly reduced ecotoxicity compared to parent BPA. By leveraging in-situ interfacial engineering of biomass-derived carbons, this work both valorizes the underutilized silicon in livestock waste and establishes a mechanistic rationale for the design of high-performance, eco-friendly PMS catalysts.