Synergistic effect of Fe and Ce on Fe doped CeO2 for catalytic ozonation of amoxicillin: Efficiency evaluation and mechanism study

Abstract

A Fe-doped CeO2 was fabricated for catalytic ozonation of Amoxicillin (AMX), and the catalytic mechanisms were explored in this study. Under optimal conditions (the initial solution pH of 7.0, FC-0.3 dosage of 0.5 g/L, O3 dosage of 4 mg/min), the AMX and TOC removal by the optimal material (FC-0.3, at Fe/Ce atomic ratio of 0.3) reached 98.1 % at 24 min and 55.2 % at 36 min, respectively. Improved the AMX mineralization efficiency by 3.7 times. The experiments and theoretical calculation reveal the mechanisms of promoted catalytic ozonation by FC-0.3: 1) Highly abundant surface-active sites (i.e., –OH) enabled the adsorption of H2O and O3, which was favorable to the generation of reactive oxygen species (ROS) and improved the reaction probability for ROS and contaminants. 2) The synergistic effect between Ce4+/Ce3+ and Fe3+/Fe2+ redox couples accelerated the electron transfer and formation of ROS. More than 42 % of •OH was generated in the presence of FC-0.3, and the •OH, •O2− and 1O2 were the main ROS that contributed to AMX degradation. The surface OH groups played a key role in the catalytic ozonation. The oxygen vacancies (OVs) played an important role in electron transfer, Ce and Fe were the active sites of electrons transfer following the sequence of (Ce3+ + Fe2+) → (Ce4+ + Fe3+) → (Ce3+ + Fe2+) redox reaction. The degradation pathway investigation and toxicity evaluation revealed that some more toxic intermediates were generated during the ozonation process, and sufficient mineralization is required to meet safe discharge. This study provides reference for the synthesis of new catalysts and insight into the reaction mechanisms in the heterogeneous catalytic ozonation process.