Heterogeneous catalytic ozonation for highly efficient mineralization of phenol with La-modified Ce/γ-Al<sub>2</sub>O<sub>3</sub>

Abstract

In this study, La-Ce/γ-Al<sub>2</sub>O<sub>3</sub> 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/γ-Al<sub>2</sub>O<sub>3</sub> increased by 20.53% within 20 min compared with ozonation alone. Moreover, the CO<sub>2</sub> mineralization rate was more than twice that of ozonation alone within 250 min, reaching 92.53%, and superior CO<sub>2</sub> mineralization was maintained after repeated use. The CO<sub>2</sub> mineralization rate of phenol after adding 3 g/L 2.5% La-Ce/γ-Al<sub>2</sub>O<sub>3</sub> 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/γ-Al<sub>2</sub>O<sub>3</sub> catalyst obtained higher adsorbed oxygen and hydroxyl species content than γ-Al<sub>2</sub>O<sub>3</sub> and Ce/γ-Al<sub>2</sub>O<sub>3</sub>. In the process of phenol catalyzed ozonation, the •O<sub>2</sub>ˉ species in the solution were deduced to be the key ROS.