Efficient degradation of sulfadiazine using FeMn bimetallic heterogeneous catalysts: Performance, mechanism, DFT calculations, and product toxicity assessment

Bimetallic oxide-based materials show potential in the degradation of antibiotics in wastewater. In this study, a core–shell MIL@ZIF-Mn was synthesized through hydrothermal and coprecipitation methods to serve as a heterogeneous catalyst to activate peroxymonosulfate (PMS) in the degradation of sulfadiazine (SDZ). Findings revealed that MIL@ZIF-Mn effectively suppresses salt interference, achieving nearly 100 % degradation of SDZ within 40 min. Additionally, MIL@ZIF-Mn exhibited excellent recyclability, maintaining a degradation efficiency of 79 % even after 5 cycles. The catalyst also demonstrated effective SDZ degradation across a broad pH range (3−11). Electron paramagnetic resonance (EPR) and quenching experiments confirmed that the main active species involved were hydroxyl radicals (·OH) and singlet oxygen (¹O₂). Density functional theory (DFT) calculations confirmed that the formation energy of FeMn=O is lower than that of Fe=O and Mn=O. Moreover, the FeMn dual-active sites facilitate O-O bond cleavage by elongating the O-O bond in PMS and reducing the energy barrier. Liquid chromatography-mass spectrometry (LC-MS) and toxicity assessment software tools (T.E.S.T.) confirmed that the toxicity of intermediate products formed during the degradation of SDZ is significantly lower than that of SDZ itself. Therefore, this research offers crucial perspectives for the logical creation of effective heterogeneous catalysts.