One-step preparation of Co3O4-modified sludgebiochar as peroxymonosulfate activator for enhancing the removal of sulfamethoxazole

High-performance transition metal/carbon composites are critical determinants for peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). This study developed a novel Co 3 O 4 -modified sludge biochar (Co/SBC) composite through an eco-friendly one-pot synthesis approach without acid/alkaline washing pretreatment of SBC, demonstrating exceptional PMS activation capacity for sulfamethoxazole (SMX) degradation. Comprehensive characterization revealed that Co 3 O 4 integration substantially enhanced the number of metal active sites and oxygen-containing functional groups. The optimized 3Co/SBC achieved 90.26% SMX removal ( k obs = 0.0591 min −1 ) within 60 min at a low PMS dosage (0.2 mM), outperforming the SBC/PMS and PMS systems by 2.67–5.18 times. Mechanistic investigations identified synergistic redox cycles (Co(II)/Co(III)), graphitic N, and C O groups as dominant active centers. Radical quenching tests and electron paramagnetic resonance analysis verified degradation pathways involving radical pathway (especially SO 4 •− ) and non-radical pathway ( 1 O 2 and direct electron transfer) in the 3Co/SBC/PMS system. This work provided a novel green synthesis strategy for fabricating transition metal/carbon composites that exhibit high performance in activating PMS, which achieved the dual roles of sludge waste resource utilization and environmental remediation. • Co 3 O 4 /sludge biochar was prepared by one-step preparation without acid or alkaline. • The system exhibited remarkable degradation efficiency at ultralow PMS dosage. • The Co 3 O 4 modification increased the metal active sites and C O group content. • SO 4 •− and 1 O 2 were the main active ingredients for SMX removal. • The system facilitated the resourceful utilization of municipal waste sludge.