Preparation of Ce-MnOX/γ-Al2O3 by high gravity-assisted impregnation method for efficient catalytic ozonation

In this study, Ce-MnOX/γ-Al2O3 was prepared by the facile high gravity-assisted impregnation method for catalytic ozonation of nitrobenzene, and a three-level and seven-factor orthogonal test was used to optimize the preparation parameters. The catalyst prepared by impregnating γ-Al2O3 in 0.24 M solution at a Ce/Mn molar ratio of 3:7, a rotational speed NR of 1000 rpm, a liquid flow rate QR of 80 L/h, and a calcination temperature T of 500 °C showed the best catalytic activity. The HRTEM results showed that the active components were highly dispersed on the surface of Ce-MnOX/γ-Al2O3 with wt% of Mn and Ce being 2.08 and 2.86, respectively. The catalytic performance showed that the nitrobenzene removal was accelerated in Ce-MnOX/γ-Al2O3 with the TOC removal of 98.3% within 20 min, which was superior to the single ozonation. The EPR and electrochemical analysis showed that Ce-MnOX/γ-Al2O3 had more oxygen vacancies, higher electron transfer capacity and lower charge transfer resistance, which was beneficial for the dissociation of ozone. Radical quenching results showed that ·O2− and ·OH were the main reactive oxygen species for the mineralization of nitrobenzene. Raman spectra and FT-IR analysis showed that oxygen vacancies and surface hydroxyl groups can act as the active sites for the decomposition of ozone into *O22− and *O2−. XPS analysis also indicated that the redox couples of Ce(IV)/Ce(III) and Mn(IV)/Mn(III) and oxygen vacancies had a synergistic effect on the decomposition of ozone into reactive oxygen species, thus improving the catalytic activity of Ce-MnOX/γ-Al2O3.