Kinetics and mechanism of enhanced norfloxacin degradation by Fe3O4@La-BiFeO3 based on weak magnetization and efficient charge separation

Abstract

Improving the yield of reactive oxygen species and inhibiting the recombination of photogenerated e- and h+ have been reliable strategies to accelerate the rate-limiting step for nano photocatalytic materials. A novel magnetic Fe3O4@La-BiFeO3 composite with variable molar ratios was successfully synthesized via a facile hydrothermal method for the photo-Fenton-like degradation of norfloxacin (NOR) under visible light irradiation. The comprehensive characterization of the crystal phase purity, morphological structure and elemental composition of the catalyst confirmed the formation of a heterojunction structure between Fe3O4 and La-BiFeO3. The effects of the composite molar ratio, initial pH, catalyst addition, and H2O2 concentration on the degradation efficiency were investigated. 20% Fe3O4@La-BiFeO3 showed the best catalytic activity with 93.8% removal of NOR after 60 min of reaction and the pseudo-first-order rate constant was 0.05952 min−1, attributed to the synergistic interaction of the photocatalytic and Fenton-like processes. The excellent stability and recyclability of the catalyst ensured the catalytic reactions continued to occur efficiently. The appropriate amount of Fe3O4 reduced the band gap of the catalyst, and the introduction of a weak magnetic field accelerated the transfer of electrons between interfaces, effectively restrained the recombination of photogenerated e-/h+ and directly enhanced the yield of ·OH and O2·-. This work not only realized the preparation of a heterogeneous photo-Fenton-like catalyst with high application potential for the degradation of antibiotics, but also provided new prospects for designing efficient catalysts on the basis of theoretical guidance.