Magnetically Separable P25/ZnFe₂O₄ Composite: Preparation And Photocatalytic Properties

Degussa P25 is commercially obtained TiO₂ nanoparticles, and is widely used as photocatalyst to removal of organic pollutants through advanced oxidation processes, due to its good performance, low cost, low toxicity and chemical stability. However, When P25 powder is applied as suspensions, it is difficult to recover and reuse after water treatment. Therefore immobilization of P25 on the magnetic carriers is a promising method, because they could be easily recovered in the magnetic field. In this thesis, submicrometer-sized ZnFe₂O₄ magnetic microsphere is not only used as the magnetic support of P25 to get magnetically separable TiO₂, but also as the inorganic sensitizer of TiO₂ to improve photocatalytic activity of P25.The P25/ZnFe₂O₄ composited photocatalyst (donated as PZ) was prepared by reflux of P25 and ZnFe₂O₄ in ethanol and then calcination of the P25/ZnFe₂O₄ composites at 450 oC. The composited photocatalyst PZ was characterized by XRD, SEM, FT-IR, and VSM respectively. The photocatalytic properties of PZ were evaluation by photodegradation of Rhodamine B. The results showed that 33%PZ (the content of P25 in the composite catalyst is 33%) was super-paramagnetic with the saturation magnetization of 30.2 emu/g, and was easily be recovered in external magnetic field. The total recovery rate of 33% PZ was 93.7% after five times reused in the photodegradation of Rhodamine B in sunlight, and the degradation rate of Rhodamine B was more than 95% in the each recycle experiment.The photocatalytic activity of PZ was seriously influenced by the resources of light. Under UV irradiation, ZnFe₂O₄ could significantly enhance the photocatalytic activity of P25, and the photocatalytic activity of 75% PZ was better than pure P25. Under visible light, though pure P25 did not exhibit photocatalytic activity, the photocatalytic activity of 33%PZ was significant. The photocatalytic activity of PZ was best in sunlight.2. The potocatalytic activity of P25/ZnFe₂O₄ composite catalyst was significantly affected by the different preparation methods such as reflux of P25 and ZnFe₂O₄ in water and then calcination, direct grinding of P25 and ZnFe₂O₄ but not calcination, grinding of P25 and ZnFe₂O₄ and then calcination, and so on. The results showed that P25/ZnFe₂O₄ composite catalyst which was prepared by reflux of P25 and ZnFe₂O₄ in ethanol and then calcination had the highest photocatalytic activity.