Developing efficient and sustainable catalysts for advanced oxidation processes (AOPs) to remove endocrine-disrupting compounds remains a critical challenge. In this study, a defect-engineered MnFe2O4@SBC composite was synthesized by loading spinel MnFe2O4 onto sewage sludge-derived biochar (SBC) prepared at different calcination temperatures, and applied for efficient periodate (PI) activation toward bisphenol A (BPA) degradation. The catalytic performance exhibited a volcano-type dependence on calcination temperature, with MnFe2O4@SBC-750 achieving the highest BPA removal efficiency (98.6% within 30 min). Structural characterization revealed that MnFe2O4@SBC-750 possessed an optimized carbon structure with a balance between defect sites and graphitized domains. Mechanistic investigations demonstrated that multiple reactive oxygen species, including •OH, O2•−, IO3• and 1O2, were involved in BPA degradation. LC-MS analysis identified key transformation intermediates and proposed degradation pathways, while toxicity assessment confirmed reduced ecological risks after treatment. Density functional theory (DFT) calculations indicated that MnFe2O4@SBC significantly enhanced PI adsorption and activation by promoting interfacial electron transfer and elongating the I-O bond in IO4−. Notably, MnFe2O4@SBC-750 exhibited the strongest electron transfer capability, attributed to the optimal regulation of defect density and graphitization degree, which facilitated π-d electronic coupling at the MnFe2O4-SBC interface. Overall, this work elucidates the critical role of defect regulation in spinel biochar-based catalysts for oxidant activation and provides a sustainable strategy for converting sewage sludge into high-performance catalysts for water purification.
Yan et al. (2026) studied this question.