Highly efficient activation of sulfite by oxygen vacancies-enriched ZnCe0.4Fe1.6O4 for methylparaben degradation

The exploitation of a novel catalyst was of great significance for sulfate radical-based advanced oxidation processes (AOPs) using sulfite as the precursor of sulfate radical. Herein, oxygen vacancies-enriched ZnCe0.4Fe1.6O4 was prepared and applied to activate sulfite for the degradation of methylparaben (MeP). ZnCe0.4Fe1.6O4 showed superior catalytic activity than that of ZnFe2O4, allowing an 85.2 % removal efficiency of MeP within 60 min. The initial pH showed a significant effect on the catalytic performance, and about 92.1 % of MeP could be removed at pH of 9.56 in ZnCe0.4Fe1.6O4/sulfite system. The quenching experiments and EPR tests verified SO4− and OH were the main reactive oxygen species (ROS) in ZnCe0.4Fe1.6O4/sulfite system. The catalytic mechanism was elucidated further by X-ray photoelectron spectroscopy (XPS) analysis of ZnCe0.4Fe1.6O4 before and after the reaction. The recycles of Zn2+/Zn3+, Fe2+/Fe3+ and Ce3+/Ce4+ were the key factor for the activation of sulfite, and oxygen vacancies on catalyst surface promoted the activation of sulfite. The degradation intermediates of MeP were determined by a liquid chromatography-mass spectrometer (LC-MS) and the degradation pathway was proposed. The reusability of ZnCe0.4Fe1.6O4 was evidenced by the recycling experiments. In addition, ZnCe0.4Fe1.6O4/sulfite system exhibited excellent applicability in treating other organic contaminants.