Highly dispersed Co-N anchored on waste-derived biochar for enhanced peroxymonosulfate activation toward ciprofloxacin degradation: Non-radical processes-dominated oxidation mechanism

Waste-derived biochar (BC) has emerged as a promising, cost-effective, and environmentally sustainable material for wastewater treatment. In this study, we developed an enhanced biochar derived from gold passion fruit shells (PFS) co-doping with cobalt and nitrogen (CoN-PFSBC), which substantially improved its catalytic performance for peroxymonosulfate (PMS) activation, enabling efficient removal of ciprofloxacin (CIP) from aqueous solutions. The CIP removal efficiency of CoN-PFSBC was critically dependent on both the pyrolysis temperature and the cobalt-to-nitrogen doping ratio. Among the various formulations evaluated, 4 %Co3N1-PFSBC-800 demonstrated superior PMS activation capabilities, achieving approximately 99 % CIP degradation with a degradation rate constant of 0.1129 min-1 within 60 min and 68.1 % total organic carbon (TOC) removal within 90 min. The system exhibited remarkable stability and effectiveness across a broad pH range (3-9), underscoring its adaptability to diverse environmental conditions. Integrated radical scavenging experiments with electron paramagnetic resonance (EPR) spectroscopic analysis revealed that CIP degradation proceeds through a dualpathway mechanism involving both radical-mediated and non-radical processes, with singlet oxygen (1O2) and high-valent cobalt-oxo species (Co(IV)) identified as the predominant reactive species. Systematic investigation of the degradation pathways coupled with ecotoxicological assessment of transformation byproducts demonstrated the effective detoxification capability of this catalytic system, showing progressive reduction in acute toxicity throughout the degradation process. This study provides new insights for the high-value utilization of agricultural waste and antibiotic pollution control.