Preparation of LMO@FC catalysts and degradation of tetracycline by catalytic ozonation

Abstract

Developing efficient catalysts with good stability holds great significance for better applying catalytic ozone oxidation in advanced wastewater treatment. Therefore, we designed a novel catalyst of LaMnO3-loaded foam ceramics (LMO@FCs) for catalytic ozonation of tetracycline hydrochloride (TCH) in water. The LaMnO3 (LMO) active components were uniformly loaded on the foam ceramics (FCs) to form an LMO@FC catalyst with mesoporous structure. The total organic carbon (TOC) removal rate by ozonation with LMO@FCs was 2.13 times that of ozone alone. After five repeated uses, the removal rate of TCH and TOC reached more than 99 % and 51.3 %, respectively. The conversion of ozone to reactive oxygen species (ROS) increased with the growth of initial pH. When pH reached zero point of charge (pHpzc), the ozone adsorption on the catalyst surface decreased, leading to the worst degradation efficiency. The Mn3+/Mn4+ and lattice oxygen (OL2−) and surface hydroxyl radical (·OH) were distributed on the catalyst surface. ·OH, superoxide anion (·O2−), and singlet oxygen (1O2) coexisted in the process of ozonation catalyzed by LMO@FCs. The surface ·OH of the catalyst was the catalytic active site. The electrostatic balance between Mn3+ and Mn4+ and the oxidation-reduction between O2− and O2 also played a crucial role in catalytic activity. The TCH experienced a series of reactions in the O3/LMO@FCs process, such as hydroxylation, demethylation, ring-opening oxidation and defunctionalization, and finally was mineralized into CO2, H2O, and NH4+. These results demonstrated that LMO@FCs are promising catalysts for catalytic ozonation of pharmaceutical wastewater treatment.