Charge-engineered 2D layered magnetic Cl-CaFe2O4/g-C3N4 catalyst for catalytic ozonation of norfloxacin: performance, mechanism and ecotoxicological assessment

Antibiotics, as a new pollutant, posed a great threat to human health and environment. Ozone catalytic oxidation is a promising technology for the removal of antibiotics, but it faced the challenges in the preparation of high-efficient catalysts. In this study, Cl-CaFe 2 O 4 /g-C 3 N 4 (CCFO/CN) was synthesized by the sol-gel method. Its structure and catalytic performance, and the toxicity and degradation products of NOR were analyzed. The results showed that CCFO/CN catalysts could form compact lamellar structure with loose pores, and Cl-CaFe 2 O 4 (CCFO) was embedded into the g-C 3 N 4 interlayer through bridging, which reduced electronic localization and extended π conjugated system. Cl − promoted the reduction of Fe 3+ to Fe 2+ through lattice modification, defect engineering and energy band modulation. The highest degradation efficiency of NOR was up to 91.79 % using catalytic ozonation and was 1.62-fold higher than that using single ozonation. Removal efficiency of NOR only decreased by 4.61 % after five consecutive cycles of CCFO/CN. Nitrogen-containing groups of g-C 3 N 4 as Lewis bases and metal cations of CCFO as Lewis acid formed metal-N coordination bond, which contributed to the improvement of structural stability of CCFO/CN. Cl − doping created a strong built-in electric field at the interface and drove electron transfer from g-C 3 N 4 to CCFO through II heterojunction. CCFO/CN had low adsorption energy, large charge transfer capacity and excellent O 3 activation properties according to density-functional theory (DFT). NOR was degraded under the synergism of adsorption and catalytic ozonation according to quenching experiments and EPR analysis, and the toxicity of NOR was significantly reduced.