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.