Mechanistic Insights into Sulfamethazine Degradation by Defect-Rich MnO₂-Activated Peracetic Acid

Manganese (Mn)-based oxides, mainly MnO2, have garnered significant attention in catalytic applications due to their superior redox properties and structural flexibility. However, their saturated coordination structure presents challenges in achieving an enhanced performance. Herein, a defective MnO2 catalyst (MnO2-D) was constructed, and for the first time, it was proven to effectively activate peracetic acid (PAA) for the complete degradation of sulfamethazine (SMT). Compared to MnO2 with a saturated coordination structure (i.e., the perfect MnO2 structure, MnO2-P), the MnO2-D catalyst exhibited a higher surface electron density and abundant surface oxygen vacancies (OVs), significantly improving its catalytic activity. Experimental evidence revealed that the OVs and Mn3+ on the surface of MnO2-D were considered as the primary active sites and that the MnO2-D/PAA system followed a singlet oxygen (1O2)-dominated nonradical pathway. The MnO2-D catalyst can maintain its activity with minimal interference from inorganic anions, humic acid, varying pH levels, and real water environments. In addition, the MnO2-D/PAA system was efficient in mitigating the toxicity of SMT and eliminating diverse micropollutants. This work presents an enhancement strategy for constructing defect-rich metal oxide catalysts to advance future water treatment technologies.