Heterogeneous catalytic ozonation for highly efficient mineralization of phenol with La-modified Ce/γ-Al2O3

In this study, La-Ce/gamma-Al2O3 materials for the catalytic ozonation of phenol were prepared by impregnation. In order to analyze the physicochemical properties, BET, SEM, XRD, XPS, and FTIR were used to characterize the catalysts. The removal performance of phenol under different reactive conditions (catalyst dosage, initial pH value, initial phenol concentration, and ozone concentration) was investigated, and the possible catalytic oxidation mechanism and conversion pathway of phenol were proposed through the analysis of ROS and intermediates in solution. The results indicated that the conversion rate of 2.5% La-Ce/gamma-Al2O3 increased by 20.53% within 20 min compared with ozonation alone. Moreover, the CO2 mineralization rate was more than twice that of ozonation alone within 250 min, reaching 92.53%, and superior CO2 mineralization was maintained after repeated use. The CO2 mineralization rate of phenol after adding 3 g/L 2.5% La-Ce/gamma-Al2O3 catalyst reached almost 100%, and could be maintained in a solution with a wide pH range of 3 9.5. From the characterization results, it could be seen that the 2.5% La-Ce/gamma-Al2O3 catalyst obtained higher adsorbed oxygen and hydroxyl species content than gamma-Al2O3 and Ce/gamma-Al2O3. In the process of phenol catalyzed ozonation, the center dot O-2(-) species in the solution were deduced to be the key ROS.