Preparation And Application Of High Active Metal/nonmetal Co-doped Nano-sized TiO₂ In Visible Light

Nanocrystalline titanium dioxide finds a broad field of realized and potential applications in the areas of photocatalysis. Selective doping of the crystalline matrix has been proved to be an efficient route to improve the photocatalytic activity of nano-TiO₂ when it is doped with various metal captions. The difficulty of recovery, steadiness and inactivation can be resolved by immobilization. The quantum efficiency of immobilized-TiO₂ is lower than that of suspended-TiO₂ with same TiO₂ mass using the traditional substrates. At present, the substrates, which have some specific properties such as high specific surface area for high-adsorption, are regarded as better. The double functions of photocatalysis and adsorption can come true with high efficiency simultaneously.The aim of this dissertation is to initiate the research of the metal ion and the non-metal ion modification and support onto AC of photocatalyst and the decolorization of Methylene blue aqueous solution and seek after optimal condition and general degradation rules, by which we look forward to building up the base for further research.The Nano-TiO₂ powders are modified by metallic ions (Fe) and nonmetallic ions(S), thus the Nano-TiO₂ powders which metallic ions and nonmetallic ions are doped, and metallic/nonmetallic ions co-doped, are synthesized. The structure of the co-doped Nano-TiO₂ powders is characterized by Laser Sizer, XRD, SEM and FTIR. Finally, the photocatalytic activities of Nano-TiO₂ powders are tested by degradation of methyl blue solution. The results indicate that the best conditions of preparation of co-doped Nano-TiO₂ powders are as follows: the ratio of TiCl4 toH2O is 1:3 in precursors, the ammonia is a depositing reagent, the calcination temperature is 400℃and calcination time is 2 h. The final Nano-TiO₂ crystal is anatase and the average size of Nano-TiO₂ powders is in the range of 10～30nm. The average size of Nano-TiO₂ increases and the rutile appears with increasing temperature. The average size, crystal and photocatalytic activity are impacted by the doping method, element type and content of doped ions. It's found that there is a prefect doping content for different elements. For Photo-degradation of methyl blue solution in visible light, catalytic activity of co-doped nanoerystalline is higher than the single-doped TiO₂ powder because co-doping elements played a good synergistic effect to promote the improvement of its photodegradation activity.The best doping ratios are as follows: S:Ti = 1:1,Fe:Ti = 0.0005:1,S: Fe:Ti = 1:0.0005: 1. TiO₂ particles loaded on active carbon (AC), is adsorbed on the surface of AC uniformly, which keep fine in particle size and firm in fixity. TiO₂ is loaded on the AC resolve the problem that TiO₂ particles are difficult to be recovered.The reaction of photocatalytic degradation for Methylene blue is not simple and in conformity with the first order appearance kinetics law with the concentration range between 2 mg/L and 7mg/L. The appearance rate constant of the reaction decreases with the increase of initial concentration of Methylene blue in water.