The efficient degradation of sulfisoxazole by singlet oxygen (¹O₂) derived from activated peroxymonosulfate (PMS) with Co₃O₄-SnO₂/RSBC

Co₃O₄-SnO₂/rice straw biochar (RSBC) was prepared for the first time via calcining oxalate precipitation precursor dispersed on the surface of RSBC and used as a catalyst for activating PMS to degrade sulfisoxazole (SIZ). The results demonstrated that Co₃O₄-SnO₂/RSBC possessed much better catalytic performance than Co₃O₄, Co₃O₄-SnO₂, Co₃O₄/RSBC, and SnO₂/RSBC, which is ascribed to the synergy of Co₃O₄, SnO₂ and RSBC. Approximately 98% of SIZ (50 mg/L) was decomposed by PMS (1 mmol/L) activated with Co₃O₄-SnO₂/RSBC (0.1 g/L) within 5 min. The optimal degradation efficiency of SIZ was realized at the initial pH 9. Co₃O₄-SnO₂/RSBC also displayed remarkable stability and reusability, and the degradation rate of SIZ maintained over 90% even after the fifth recycle run. The electron paramagnetic resonance (EPR) technique and quenching experiments proved singlet oxygen (¹O₂) to be the main reactive oxygen species (ROS) responsible for the SIZ decomposition in the Co₃O₄-SnO₂/RSBC/PMS system. On the basis of the characterization analysis, the identification of the ROS and the SIZ degradation products, the possible mechanism and pathways of the SIZ degradation by a combination of PMS and Co₃O₄-SnO₂/RSBC were further proposed. This study provides not only a new insight into non-radical mechanism for the heterogeneous activating PMS over Co₃O₄-SnO₂/RSBC to degrade organic pollutants but also an eco-friendly synthetic route for exploring novel and efficient catalysts.