Characterization of a Doped MnO₂Al₂O₃ Catalyst and its Application Inmicrobubble Ozonation for Quinoline Degradation

The process of catalytic ozonation shows promise for the degradation of refractory contaminants. A doped MnO₂/Al₂O₃ catalyst was prepared and utilized to achieve catalytic microbubbles ozonation for quinoline degradation. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis show that the active component, MnO₂ (spherical, approximately 30–50 nm in diameter) dispersed well in the porous Al₂O₃ support. X-ray photoelectron spectroscopy (XPS) indicated that the oxidation state of the MnO₂ was Mn⁴⁺, which was consistent with the results of the XRD analysis. It was confirmed that the crystal form was α-MnO₂. Characterization of the MnO₂/Al₂O₃ catalyst was conducted, and the optimal content of MnO₂, its calcination temperature, and the duration of the process was determined. It was confirmed that the optimal content of MnO₂ was 8% of the catalyst, and the optimum calcination temperature and duration were 500°C and 4 h, respectively. The highest removal efficiencies of 95% and 65% for quinoline and TOC, respectively, were achieved after 90 min of catalytic ozonation at an ozone dose of 135.0 mg/L. In addition, catalytic ozonation of quinoline by microbubbles of ozone (66.7 μm average diameter) showed 10% higher degradation efficiency than that using normal-sized aerated ozone.