Highly stable and efficient calcined γ-Al 2 O 3 catalysts loaded with MnO x -CeO x for the ozonation of oxytetracycline

Catalytic ozonation with supported metal oxides is a promising strategy for addressing refractory pollutants in wastewater. In this study, γ-Al O supported MnO -CeO catalysts (MC , MC , and MC ) obtained at different calcination temperatures (400 °C, 550 °C, and 700 °C) were applied as effective catalysts for ozonation and explored the feasibility of the treatment of oxytetracycline (OTC) wastewater. Comparatively, the MC possessed the highest molar ratios of Mn /Mn (1.60) and Ce /Ce (0.96), the largest surface area (273.8 m g ) with a petal-shaped structure, and most abundant surface hydroxyls (3.78 mmol g ). These physicochemical characteristics benefited the surface reaction and resulted in the acceleration of ozone decomposition, electron transfer, and •OH generation, thereby improving the catalyst's adsorption ability and catalytic activity. The combination with MC increased the OTC and COD removal of the ozonation process from 59.1% and 29.0% to 94.7% and 83.3% in 25 min, respectively. By employing electron paramagnetic resonance (EPR) and radical quenching experiments, it was verified that •OH species generation promoted the mineralization of OTC. The possible degradation pathways of OTC were investigated through mass spectrometry, and the route consisted of dehydration, deamination, and demethylation. Moreover, during a 12-day continuous experiment, MC catalyst exhibited excellent reusability and catalytic stability, with COD removal efficiencies above 80%.