Activation of peroxymonosulfate by MnFe2O4@BC composite for bisphenol A Degradation: The coexisting of free-radical and non-radical pathways

In this study, novel metallic oxide catalyst MnFe2O4@biochar composite was synthesized by sol-gel pyrolysis loading of MnFe2O4 on biochar, and then used to activate peroxymonosulfate (PMS) to degrade bisphenol A (BPA). Characterization results demonstrated that the Fe and Mn oxide particles were homogeneously distributed on the surface of biochar, which avoided the aggregation of metal oxides. The strong magnetism of the composite was conducive to recycling during practical application. In the PMS system activated by MnFe2O4@biochar composite, the removal rate and mineralization rate of 20 mg/L BPA reached 100% and 95.9% within 30 min, respectively. The quenching experiments and electron paramagnetic resonance (EPR) study verified the coexistence of free-radical and non-radical pathways in the MnFe2O4@biochar/PMS system, with O-2(center dot-) as the dominant active species, followed by singlet oxygen (O-1(2)). The catalytic degradation process could adapt a wide pH range from weak acid to the alkaline matrix and showed negligible influence by anions and humic acid. The characterization results confirmed the synergistic effect of the bimetal, proving that the introduction of biochar and second metal source into iron-based catalyst played an important role in the composite. Overall, the MnFe2O4@biochar showed promising performance in activating PMS for organic pollutant degradation in water with high stability and safe performance.