Preparation Of Modiifed TiO₂and Its Photocatalytic Performance

Photocatalytic technology for refractory wastewater pretreatment has many advantages,including a wide application range, no secondary pollution, degradation and mineralization oforganic pollutants completely, less energy consumption and easy to implement. As a majorsemiconductor photocatalyst, TiO2has attracted extensive interest. Currently, TiO2powderand TiO2thin film coated on the grass, ceramics, etc. are applied widely. As transparent orsemitransparent solid, TiO2aerogels particles are almost transited by the ultraviolet lightcompletely which can excite the surface and internal TiO2molecule to release holes andelectrons. Furthermore, because of the small particles in the quantum scale, the holes andelectrons generated when TiO2aerogels irradiated with ultraviolet light are not recombinedeasily, that greatly improved the photocatalytic activity. So TiO2aerogels will become thematerial photocatalytic on account of its important application prospect in solar energyconversion, photocatalysis and other fields.Although TiO2aerogels exhibit remarkable photocatalytic activity, the followingproblems exist in photocatalytic process. TiO2aerogels, possessing broad band gap of3.2eV,can only use UV with shorter wavelength and high energy, but can not make full use of solarenergy. Fe3+doped TiO2aerogels can absorb light in the visible region to increase theexcitation activity. In order to conquer these questions, TiO2aerogels doped with Fe3+areprepared at low temperature and constant pressure using ionic liquid(IL) assisted sol-gelmethod. Our works are as follows:(1) TiO2aerogels were prepared at low temperature and constant pressure using ionicliquid ([C6mim] Br) assisted sol-gel method. What we did in this part was to find the impactof aging time and aging temperature on the structure and catalytic properties of TiO2aerogels.Experimental results showed that the optimum conditions for the aging temperature was60℃and aging time was72h. The crystal structure of TiO2aerogels were assigned to theanatase form of TiO2as a unique phase. Under optimum conditions, TiO2aerogels showedanatase crystalline form, a high specific surface area and high photocatalytic activity. (2) Fe3+-TiO2aerogels were prepared by sol-gel method which similar to the process ofthe pure ones, only Fe (NO3)3·9H2O was added into the solution as source of Fe3+. We hadresearched the effect of the amount of Fe3+on the structure and catalytic properties of TiO2aerogel. The optical absorption properties of pure TiO2aerogels and TiO2aerogels doped withFe3+were tested with UV-vis diffuse reflectance spectra. Un-doped TiO2had no absorption inthe visible region, however, Fe3+-TiO2aerogels showed a red shift of absorption edge and anincrease in the visible light region. Furthermore, there was a remarkable peak at480nmapproximately that would enhance the photocatalytic activity.(3) Prepared Fe3+-TiO2aerogels samples’ degradation experiments of reactive brilliantblue solution showed that compared with P25and pure TiO2, Fe3+-TiO2aerogels revealedhigher photocatalytic activity. Aerogels prepared with n(Ti4+): n(Fe3+)=1:0.03had the highestphotocatalytic activity whether under ultraviolet of95.7%or visible light of97.2%,respectively.