Mechanism of dual-pathway peroxymonosulfate activation via Co-N coordination-regulated broad-pH-adaptive carbon aerogel for ciprofloxacin degradation.

Ciprofloxacin(CIP) exhibits persistent stability in aquatic environments, rendering conventional treatment methods inefficient. In this study, a dual-functional material system integrating adsorption and catalysis was constructed through rational design of transition metal-doped carbon aerogels. Utilizing chitosan as the carbon source, Co@CsCA materials were synthesized via sol-gel method followed by high-temperature carbonization. Nitrogen doping controlled the Co-N coordination structure, while hierarchical channels stabilized active sites through localized confinement effects. Characterization revealed that Co@CsCA possesses an ultra-high specific surface area (195.85 m/g) and a mesopore-dominant structure (pore size: 5.26 nm), with cobalt coexisting in multivalent states (Co/Co/Co, verified by XPS). Performance tests demonstrated that the Co@CsCA/PMS system achieved 87.1 % CIP degradation within 60 min (20 mg/L) across pH 3-11, significantly outperforming Fe/Cu systems (<70 % at pH 5). The material maintained 91.8 % activity retention after five consecutive cycles. Mechanistic studies indicated dominance of the SO/OH radical pathway under acidic conditions (51.9 % contribution via EPR quenching experiments), while the non-radical pathway predominated (70 %) under alkaline conditions. This dual-path synergy effectively overcomes the pH limitations of conventional catalysts. DFT calculations revealed that the Co-N site exhibited stronger PMS adsorption energy (-2.865 eV) than the Fe-N structure (-1.959 eV), with the piperazine ring (HOMO distribution) and quinolone ring (Fukui index f> 0.1) identified as key attack sites. Thirty-five intermediates were detected by LC-MS, and ECOSAR toxicity assessment confirmed reduced toxicity during degradation. This work provides novel materials and strategies for wide-pH-adaptive deep treatment of highly toxic antibiotic pollutants.