Preparation And Photocatalytic Activity Of TiO₂-based Spherical Materials

TiO₂ has been the most promising photocatalytic material because of its high photosensitive efficiency, stability and low cost. However, TiO₂ can only absorb ultraviolet light（3%⁵% of the solar spectrum）, and small size TiO₂ particles need separation progress as the photocatalyst, which will cause the photocatalyst to lose. In this thesis, the obtained TiO₂ photocatalyst can be recycled easily. Meanwhile, a new characterization mean was used to illustrate the light absorbability of TiO₂ from another point of view. The main contents of this thesis are as follows:By using the hydrothermal method and the solvothermal method, 3D hollow millimetre-scaled TiO₂ beads were obtained. TBOT（tetrabutyl titanate） and amberlite IRA-900 resin were as the TiO₂ precursor and the hard template, respectively. The influences of the impregnation times and the calcination progress on the morphology, crystalline phase and composition of the 3D hollow millimetre-scaled TiO₂ beads have been studied. The catalytic activity was investigated by the degradation of the organic dye. The results showed that the 3D hollow millimetre-scaled TiO₂ beads enable their straightforward separation from the reaction mixture after completely degrading the dye. In order to extend the light response of TiO₂ catalyst to the visible region, the composite of the carbon and TiO₂ were realized by changing the calcination temperature of the above solvothermal method. The average size of TiO₂ nanoparticles is smaller than 10 nm and the crystalline structure is fine. The sample with calcination at 400℃ for 2 h showed strong visible light absorption between 330-550 nm. This is beneficial to the electron transport at the surface of the catalyst, and reduces the photo-generated electron hole recombination. The catalyst with calcination at 400℃ for 2h had better visible light catalytic degradation ability.A series of mesoporous TiO₂/C beads were synthesized by one-pot method. Amberlite IRA-900 resin and potassium titanium oxide oxalate dihydrate were used as carbon and titanium precursors, respectively. The dispersed TiO₂ nanoparticles were limited in the channel of the mesoporous carbon. The crystal phase composition was decided by the carbonization temperature, and the TiO₂ crystal transformation was inhibited by the activated carbon. The Meso-TiO₂/C samples were the mixture of anatase and rutile with the carbonization temperature at 900℃. The anatase was completely transformed to rutile with the carbonization temperature at 1100℃. During the carbonization progress, the size of the beads decreased greatly, and partial pores of the IRA-900 disappeared and other mesopores generated by the expansion of gases during the carbonization. The activated carbon and the TiO₂ nanoparticles exhibited the synergistic effect during the degradation progress of MO pollutants in water The mesoporous channel was beneficial to the transmission of the dye.Transmission of the synthesized Meso-TiO₂/C samples was measured using two visible-infrared band spectral radiation characteristics measuring equipments. From the measurement results the spectral absorption ability of the samples were analyzed. the radiation properties of the samples were obtained adopting single particle size hypothesis and using the measurement data with the MIE scattering theory and K-K relation. This illustrated that the absorption of visible light was the best. For 1.31-25mm infrared complex refractive index, n and k both increased with the carbonization temperature rising. For 0.3-2.5mm complex refractive index, n and k of Meso-TiO₂/C-900-2 were the largest. n values of Meso-TiO₂/C-1100-1 were relatively smaller, but the k values were the largest except Meso-TiO₂/C-900-2. By the quantitative analysis of the absorption ability of the visible-infrared spectral radiation, the different visible-light catalytic activities of the Meso-TiO₂/C were discussed.