The Studies On Preparation And Characterization Of Cerium Based Catalyst And Its Catalytic Ozonation Properties

Ozonation technology as an important aspect of advanced oxidation technology, especially heterogeneous catalytic ozonation technology, which has a wide application in the field of water treatment. As the most universal industrial organic pollutants, phenolic wastewater has enormous amount and a lot of damage, which is mainly derived from gas, petrochemical and pharmaceutical industries. In this thesis, heterogeneous phase catalytic ozonation system has been established and synthesized a series of Al₂O₃ supported catalyst for further treatment of phenol simulated wastewater. A immersion precipitation strategy was used to synthesize a one-component metal oxide CeO_x/Al₂O₃. To further improve the performance of the catalyst, Auxiliary metal Mn was introduced and composite metal oxides Mn CeO_x/Al₂O₃ as a catalyst for catalytic ozonation. Then, we optimized the preparation conditions of these two kinds of catalysts and characterized this prepared catalysts. In addition, its catalytic ozonation performance and mechanism were further explored.The preparation conditions of CeO_x/Al₂O₃ catalysts were studied and we used statistical analysis software of Design Expertv8.0.5b for designing experiments. The optimized preparation technology was as follows: 380 °C of calcination temperature, 3.87 hours of calcination time, 0.7mol/L impregnation concentration and the predict removal rate of 92.4724%. In heterogeneous catalytic ozone system, the prepared catalysts were applied to the treatment of phenol for 30 min under optimized conditions and the initial concentration of phenol was 100mg/L. The results demonstrated that the actual removal rate of phenol was 91.05%. The prepared catalyst was characterized by BET, SEM,TEM, XRD, XPS and FT-IR. The results showed that the catalyst is uniformly dispersed mesoporous structure, multi-lacuna and arge specific surface area. In the catalyst CeO_x/Al₂O₃, elements Ce exist in two main valence state and Ce3+ and Ce4+ has synergistic effect. Compared with the carrier A1₂O₃, the catalyst surface has richly hydroxyl groups, which is much favorable to improve catalytic performance.On the basis of the one-component catalyst, we selected three assistants Ti, Cu and Mn in order to further improve the catalytic performance of catalysts. The Mn CeO_x/Al₂O₃ showed highest catalytic activity. According to preliminary results, the optimized preparation conditions of Mn CeO_x/Al₂O₃ catalysts were studied and we used statistical analysis software of Design Expertv8.0.5b for designing experiments. The optimized preparation technology was as follows: 0.7 of molar ratio, 382 °C of calcination temperature, 3.7 hours of calcination time. Three parallel experiments was designed to verify accurate and reliable of the prediction model. The results demonstrated that the average removal rate was 99.01%. The prepared catalyst was characterized by BET, XRD, XPS, SEM and FT-IR. The results showed that the catalyst surface had more evenly cerium owning to the load of manganese. Also, the catalyst had the advantages of complex mesoporous structure, multi-channel and larger surface area. Manganese oxides were formed MnO2 and Mn2O3. Compared with the single component catalyst, the composite metal oxides catalyst surface had richer hydroxyl groups. The excellent catalytic performance could be attributed to the synergistic effects between manganese and cerium species.In addition, some important parameters for the influence of catalytic ozonation of phenol, such as, reaction temperature, ozone dosage, catalyst dosage, initial concentration and initial pH in degradation of phenol were further studied. Compared with the carrier A1₂O₃, the surface of catalyst CeO_x/Al₂O₃ has richly hydroxyl groups after loading the metal element of Ce. In addition, the surface of catalyst Mn CeO_x/Al₂O₃ shows more hydroxyl groups when import the element of Mn. The Mn CeO_x/Al₂O₃ reveal the best catalytic performance. During the process of experiment, we put in t-ButOH alchol of 50 mg/L for inhibiting hydroxyl radicals. The results demonstrated that removal rate of the phenol targeted pollutant shown significant inhibition. High concentrations of t-ButOH was prominently inhibited the generate of ?OH and the degradation of phenol. Therefore, based on the above results, we further indirectly demonstrated that the ozone oxidation system of CeO_x/Al₂O₃ and MnCeO_x/Al₂O₃ followed ?OH action mechanism.