?-Al2O3 doped with cerium to enhance electron transfer in catalytic ozonation of phenol

Ozone decomposition into free radicals, which can be facilitated by enhancing electron transfer between ozone and catalyst, is an important segment in catalytic ozonation. We doped cerium uniformly on γ-Al2O3 with an impregnation–calcination method to enhance electron transfer in catalytic ozonation of phenol in aqueous solution. The removal efficiency of phenol is raised from 39.7% by ozonation alone to 46.3% by catalytic ozonation with Ce/Al2O3 in 50 min reaction. A higher Ce3+/Ce4+ ratio in Ce/Al2O3 witnesses a higher electron transfer rate in catalytic ozonation and thus a higher degradation efficiency of phenol, illustrating that the activity of Ce/Al2O3 depends on the valence state of Ce. The electron transfer cycle is formed by the electron donation from Ce3+ to ozone molecule and the electron acceptance of Ce4+ from adjacent lattice oxygen. After getting the electron, the ozone molecule is decomposed to generate free radical of ·OH on the surface of Ce/Al2O3. The continuous flow experiments exhibit a stable and high catalytic activity of Ce/Al2O3 for catalytic ozonation, implying the feasibility in practical application. © 2020 Elsevier Ltd