Synthesis And Properties Of Magnetically Separable Photocatalysts

As a kind of commonly used photocatalysts, TiO2has the advantages of non-toxic, steady, cheap and no pollution, etc. However, its relatively wide band gap limits the usage of visible light and it is difficult to recycle the TiO2powders from water after treatment, which raises the cost. Considering this shortcomings, composite Bi2O3to increase the utilization of visible light and give magnetism to the photocatalysts are used to modify TiO2.Fe3O4was prepared by a solvothermal method, while TiO2, Fe34/TiO2composite photocatalysts were synthesized by a sol-gel method. Effects of doping amount of Fe3O4, calcination temperature, calcination time were investigated emphatically. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and diffuse reflectance spectroscopy (DRS). The photocatalytic degradation of MO (methyl orange) with the prepared photocatalysts was studied under UV light illumination. The experiment results show that the best doping ratio of Fe3O4is5%, the best calcination temperature is400℃and the best calcination time is2h; The best dosage of photocatalysts is lg/L and the best pH is3. Besides, the removal rate drops with the rise of initial concentration.In order to improve the utilization of visible light, the Fe3O4/TiO2/Bi2O3composite photocatalysts were synthesized by a sol-gel method. Effects of doping amount of Bi2O3, calcination temperature, calcination time were investigated emphatically. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The photocatalytic degradation of MO (methyl orange) with the prepared photocatalysts was studied under simulated sunlight illumination. The experiment results show that the best doping ratio of Bi2O3is2%, the best calcination temperature is400℃and the best calcination time is1h; The best dosage of photocatalysts is lg/L and the best pH is3. Similar to the two-phase composites photocatalysts, the removal rate drops with the rise of initial concentration. For the repeated experiments, the removal rate drops slightly with the cycle times. XRD analysis shows that all the photocatalysts obtained are anatase crystal. TEM analysis reveals that Fe3O4and TiO2formed a core-shell structure. DRS results reveal that the optical absorption of all composite photocatalysts exhibits a red-shift. TiO2, Fe3O4and Bi2O3exist mainly as separate phases in the Fe3O4/TiO2/Bi2O3composite photocatalysts based on XPS analysis. Experiments indicated that the MO degradation rate with the Fe3O4/TiO2/Bi2O3photocatalysts was higher than that with pure TiO2, obviously.