Preparation And Characterization Of Visible Light-activated Fe, F Doped NanoTiO₂ Sol

Recently, the photocatalytic technology has developed rapidly in the control of environmental pollution, sterilization and disinfection, and so on. Organic or inorganic pollutants can be decomposed to simple nontoxic substances, such as CO₂ and H₂O at room temperature by employing various photo catalysts with solar energy. Such processes can be carried out under mild reaction conditions with simple equipments. The photo catalytic technology is superior to the traditional catalytic or adsorption technologies in this way. Because of its high chemical stability, environment-friendliness, and relatively economy, TiO₂ is widely used as photo catalysts. However, TiO₂ is a large band gap semiconductor and becomes active mainly by irradiating with ultraviolet light, which is only 4% of the solar energy. Therefore, many efforts have been made to dop TiO₂ in order to improve its photo catalytic activity in the visible light region. Doping TiO₂ with metal or nonmetal ions can effectively reduce the band gap of TiO₂, and make TiO₂ respond to the visible light.In this paper,TiO₂ was prepared through a peroxide process and a modified precipitation-sol method at low temperature. Its pH value was neutral and could be preserved very well. After having been saved about 1 year, the phenomenon of precipitation or gel did not appear. The experiments of adsorbed water was carried out and showed that the prepared titanium dioxide hydrosol had a good hydrophilic property. On this basis the Nano-TiO₂ sol was doped by ions and nonmetallic ions F-, and the Nano-TiO₂ sol with Fe³⁺,F^-, metallic/nonmetallic ions were synthesized. The chemical structure and properties of the nano TiO₂ were characterized by FTIR, XRD, TEM and Spectrophotometer respectively. In this paper, solution of methylene blue was used to simulated organic wastewater, and pure and doped nano-titanium dioxide’s activity as photocatalyst was studied respectively in the photocatalytic degradation.The average size, crystal type, the extended range of visible light absorption and photocatalytic activity were influenced by the doping method, element type and content of doped ions. And compared to the pure titanium dioxide sol, the particle size of the single-doped decreased, the particle size of the co-doped increased; The doping contributed a higher proportion of anatase titanium dioxide; The absorption spectrum of the doped nano-titanium dioxide had a marked expansion in the visible region, photocatalytic activity had been significantly improved, and the order of the photocatalytic activity from low to high was: pure titanium dioxide, fluorine-doped, iron-doped, fluorine/iron co-doped.