Oxygen vacancies induced by Zn2+ doping initiated ozone decomposition to produce more reactive oxygen species for effective degradation of norfloxacin using Cu1-xZnxFe2O4 catalyst

To promote the electron circulation and enhance the stability of the catalyst, Cu_1-xZn_xFe₂O₄ (x = 0, 0.2, 0.5, 0.8) catalysts with abundant oxygen vacancies were synthesized using sol-gel combustion method. The effects of catalyst dosage, ozone concentration and initial solution pH on catalytic degradation efficiency of norfloxacin (NOR) were investigated. The morphology and structure of the catalysts were analyzed and its catalytic ozonation mechanisms was explored. The results showed that Cu_0.2Zn_0.8Fe₂O₄ catalyst was black nanoparticle powder with good stability and agglomeration. Removal efficiency of NOR could reach the highest value of 92 % and the k_obs of first-stage reaction was 0.0752 min⁻¹ under O₃ concentration of 3.4 mg·L⁻¹, initial pH 7 and catalyst dosage of 0.1 g·L⁻¹ in Cu_0.2Zn_0.8Fe₂O₄/O₃ system. Removal efficiency of NOR was slight decreased by 4.56 % after 5 cycles of the catalyst. Zn²⁺, as an “inert” dopant, reshaped the local electronic environment and surface properties of CuFe₂O₄ through unique electronic regulation and structural stability in redox reaction, ultimately achieving a significant improvement in catalytic ozonation efficiency. Zn²⁺ occupied Cu²⁺ sites in the crystal structure and blocked the pathway of Cu as electron acceptor in the reduction process, forming Zn-O-Fe bimetallic bonds and leading to lattice deformation and the generation of more O_V in the catalyst. The surface hydroxyl groups formed by O_V adsorption were active sites for O₃ decomposition to produce ∙OH, ∙O₂^- and ¹O₂. Among them, ∙O₂^- and ¹O₂ were dominant reactive oxygen species for effective degradation of NOR.