Preparation, Characterization And Photocatalytic Activities Of Bi₂WO₆ And TiO₂ By Doping And Loading Photocatalysts

At present, TiO₂-doped or design a new type of visible light response photocatalyst, which can improve the utilization of sunlight, is an important research subject in photocatalysis field. Meantime, TiO₂ immobilized to solve the problem of separation and recycling is also currently the research hot spots. In this dissertation, research was carried out for the hot spots.Firstly, Bi-doped TiO₂ photocatalysts were prepared by doping bismuth nitrate through a sol-gel method. The catalyst samples were characterized by XRD,FTIR,TEM,XPS,UV-Vis to obtain the structure, crystal form and surface state. Rodamiine-B (RhB) was used in the study of photocatalytic properties. The results showed that appropriate amount of bismuth nitrate doped TiO₂ did not change the crystal structure of TiO₂, Bi in the form of oxides (+5, and 3-x) embedded into the TiO₂ lattice, and Bi doped TiO₂ photocatalytic activity was better than P-25.Secondly, Bi, C and N codoped TiO₂ were prepared by sol-gel method using bismuth nitrate and urea as dopants. The structure and surface state of photocatalysts were characteries by various characterization instruments. The photocatalytic properties of photocatalysts were studied. The results showed that C and N could replace the oxygen atoms to form Ti-C and Ti-N bonds in TiO₂ lattice by adding urea. Bi also doped into the TiO₂ which existes two valences of +3 and +5. Two kinds of oxides of Bi₂O₃ and Bi2O5 embedded into the TiO₂ lattice. When the Bi amount is fixed, the doping of urea has an optimal value in co-doped samples.Thirdly, Bi₂WO₆ was prepared by a typical hydrothermal synthsis. Bi₂WO₆ precursors at different crystallization time were characterized and the reaction mechanism was discussed. NaOH was used to adjust the pH of the precursor suspensions, and the effects of the pH on the crystalline shape and morphology of the samples were studied. When 5% mass fraction of aqueous ammonia instead of the NaOH was used to adjust the pH of the precursor suspension, a flower-like crystal Bi₂WO₆ was obtained. The phase composition and morphology were disscussed and the photocatalytic activity of samples was evaluated.Finally, based on the unique absorbent characters and three-dimensional network structure of polyacrylate (PAA) superabsorbent polymer, TiO₂ (P-25) nanoparticles were loaded on PAA to synthesise a photocatalytic TiO₂/PAA nanocomposite by an aqueous solution polymerisation method. The results showed that TiO₂ nanoparticles dispersed evenly in PAA superabsorbent, where TiO₂ reacted with PAA by–OH. The coexistence of anatase and rutile phase in TiO₂/PAA contributed to improve the photocatalytic activity of the photocatalyst. The influence of preparation conditions including the concentrations of initiator, crosslinker and monomer, the degree of neutralisation, the TiO₂ dosage and the illumination time on the decolorisation rate of MO were investigated in detail. The TiO₂/PAA photocatalyst had excellent degradability resistance and reproducibility.