Preparation Of Ce/ZrOx Catalyst And Study Of Its Microwave-Assisted Photocatalytic Oxidation Efficiency Of DMP In Water

Microwave radiation could improve the efficiency and shorten reaction time of photocatalytic process, which was particularly suitable for degradation of high concentration recalcitrant pollutants in water. In this work, a novel catalyst Ce/ZrOx responded to both microwave and ultraviolet light was prepared. And the microwave-assisted photocatalytic oxidation of dimethyl phthalate (DMP) withCe/ZrOx catalyst was set up. The influence parameters of the reaction were studied and optimized. The mechanism of the reaction and the synergistic effect between microwave and ultraviolet light were discussed on these bases. Ce/ZrOx was prepared via surfactant assisted precipitation-hydrothermal method. The factors of preparing Ce/ZrOx were optimized by the removal efficiency of DMP in the microwave-assisted photocatalytic process: Ce:Zr molar ratio was 2%, pH=9, the dosage of CTAB was 0.3g, ZrOCl₂·8H₂O concentration was 0.4mol/L, hydrothermal reaction time and temperature were 12h and 160℃, respectively. The crystal size was 9.9nm. Oxygen vacancies existed on the surface of the catalyst. Zr existed as different valences (+3,+4) at the surface of the catalyst, while Ce existed as +4 valence mainly. The specific surface area of Ce/ZrOx was about three times as large as ZrOx. The catalyst was rich in mesopore with smaller pore size and larger pore volume as result of Ce doping.DMP was degraded as target substance by microwave-assisted photocatalytic process catalyzed by Ce/ZrOx. The influence of conditions such as the dosage of Ce/ZrOx, initial pH, microwave power, reaction time, initial DMP concentration, flow velocity of peristaltic pump and H2O2 were discussed on the removal efficiency of DMP. Taking saving chemical agent and energy into consideration, the optimal parameters of pre-treating 100mg/L DMP wastewater were: dosage of Ce/ZrOx 2.0g/L, without initial pH regulation, microwave power 300W, reaction time 12 min, flow velocity of peristaltic pump 6mL/s and without H2O2.Under these conditions, DMP could removed over 80%. The catalyst activity remained steady after being used for 6 times. It attested that DMP was degraded via the combined effects of hydroxyl radical indirect oxidation and photogenerated hole direct oxidation by the influence of adding tert-butyl alcohol and detecting intermediates of the DMP degradation. By comparison of different processes, it showed that microwave and ultraviolet light coupled efficiently, existing a significant synergistic effect between these two electromagnetic fields.