Catalytic degradation of phenol by PMS activated with potassium oxalate-urea synergistically modified corn cob biochar

The catalytic performance of biochar for peroxymonosulfate (PMS) activation strongly depends on its modification strategy, yet the relationship between structural regulation and activation mechanism remains insufficiently clarified. In this study, corn cob-derived biochar was synergistically modified using potassium oxalate activation and urea-assisted nitrogen doping to enhance surface defects and electronic properties for PMS activation toward phenol removal. The modified catalyst (K-NBC) exhibited a significantly increased specific surface area, approximately 36 times higher than that of pristine biochar. The effects of initial pH, PMS concentration, catalyst dosage, and phenol concentration were systematically evaluated. Radical quenching experiments, electron paramagnetic resonance (EPR), and electrochemical analyses suggested that free radicals, likely including O2•-, and non-radical electron-transfer pathways jointly contributed to phenol removal. Density functional theory (DFT) calculations and GC–MS/MS analysis were further employed to propose possible transformation pathways, and the ecotoxicity of detected intermediates was predicted using ECOSAR. This study provides insights into the rational design of defect-engineered and nitrogen-functionalized biochar catalysts for PMS-based advanced oxidation processes in water treatment.