Effect of MnFe2O4 loading on photocatalytic performance of BiVO4 for levofloxacin degradation with or without peroxydisulfate

Bismuth vanadate (BiVO4) has been regarded as a promising catalyst used for water purification under solar light irradiation, but its performance and reusability needs to be further strengthened. Herein, magnetic MnFe2O4 nanoparticles were uniformly distributed on BiVO4 surface to form a MnFe2O4/BiVO4 composite catalyst, and the effect of MnFe2O4 loading on photocatalytic performance of BiVO4 with or without peroxydisulfate (PDS) was investigated. Unexpectedly, the constructed Type-II MnFe2O4/BiVO4 heterojunction exhibited inferior photocatalytic activity compared to pure BiVO4 in the degradation of levofloxacin (LVF), which could be attributed to the diminished oxidative capacity of holes (h+). With the assistance of PDS, magnetic MnFe2O4 enhanced the photocatalytic activity and reusability of BiVO4 toward LVF degradation, as the MnFe2O4/BiVO4 heterojunction facilitated charge transfer and collaboratively boosted PDS activation through dual pathways (photo-generated electron and Fe/Mn activation) under visible light illumination. Under photocatalytic PDS activation by the optimized MnFe2O4/BiVO4-20 composite (0.5 g L-1), 84.12 % LVF (10 mg L-1) degradation was achieved after 120 min, consistent with second-order reaction kinetics (k = 0.00431 L mg-1 min-1). Magnetic MnFe2O4/BiVO420 exhibited remarkable stability and could be easily recovered, sustaining a high efficiency (86.76 %) even after five cycles of repeated use. Mechanism analysis attested that the free radical (O2 center dot-, center dot OH and SO4 center dot-) and non-free radical (h+ and 1O2) oxidation pathways mutually led to LVF degradation in Vis/MnFe2O4/BiVO4-PDS system. The ecological toxicity of LVF in water can be effectively mitigated through treatment with the Vis/MnFe2O4/ BiVO4-PDS oxidative system.