[Degradation of SMX with Peracetic Acid Activated by Nano Core-shell Co@NC Catalyst]

Peracetic acid (PAA), as a new oxidant, has attracted increasing attention in the treatment of refractory organic pollution in sewage. In this study, the nano core-shell Co@NC catalyst was prepared via etching and used to activate PAA to degrade sulfamethoxazole (SMX) in sewage. The results indicated that the degradation rate of SMX reached 98%, and its reaction rate constant was 0.80 min^-1 under optimal conditions (catalyst dosage=0.02 g·L^-1, PAA concentration=0.12 mmol·L^-1, pH=7, SMX concentration=10 μmol·L^-1). With the increase in PAA concentration and core-shell Co@NC dosage, the degradation efficiency of SMX increased. The study found that the core-shell Co@NC/PAA system had the best degradation effect on SMX under near-neutral conditions (pH 6.0-8.0), and both acidic and alkaline environments were not conducive to SMX degradation. HCO₃^- and humic acid showed significant inhibition on the degradation of SMX, whereas Cl^- showed weak inhibition. In addition, through a free radical quenching experiment and electron paramagnetic resonance (EPR) detection, acetoxy radical (CH₃CO₂CO₃·) were the main active species for the degradation of organic pollutants in the system. Transformation products (TPs) of SMX were analyzed by U-HPLC-Q-Exactive Orbitrap HRMS, and a possible degradation path of SMX was proposed. At the same time, the catalyst recycling experiment showed that the nano core-shell Co@NC catalyst had good stability and reusability.