Ce-doped LaMnO3-δ perovskite as an efficient ozonation catalyst for the degradation of high-concentration phenol wastewater

Abstract

In this study, a series of La1−xCexMnO3-δ (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) perovskites with different Ce doping ratios were synthesized by the citrate sol-gel method for catalytic ozonation degradation of phenol at high concentration. Among them, the La0.9Ce0.1MnO3-δ catalyst showed the best catalytic performance, increasing COD removal nearly three times compared with ozonation alone. The COD removal of the catalysts was 0.1 > 0.3 > 0 > 0.5 > 0.7 > 0.9 > 1.0, which corresponded to COD removal of 67.56 %, 58.12 %, 57.94 %, 53.68 %, 52.18 %, 49.19 %, and 39.24 %, respectively. SEM, BET, and XRD characterized the structural performance of the catalysts. The two critical parameters of catalyst dosage and pH were also optimized. Simultaneous reproducibility experiments demonstrated the good reusability of the catalyst. In addition, the catalytic degradation mechanism was investigated by the qualitative and quantitative detection of free radicals, EPR, fluorescence detection, XPS and TPD/TPR tests, which indicated that the surface hydroxyl groups, oxygen vacancies, and Mn(Ⅲ)/Mn(Ⅳ) and Ce(Ⅲ)/Ce(Ⅳ) redox pairs on the surface of the catalysts were the potential active sites for the decomposition of ozone to ROSs. The doping of Ce can effectively increase the number of active sites and promote the electron cycling process, thus generating large amounts of •OH and O2-•, effectively mineralizing phenol.