The Research Of Metal Ion Doping In Nano-TiO₂ And Photocatalytic Activity

Along with worsening of the environmental quality of the earth, people have been attaching more and more attention on environmental protection. Some traditional treating methods for wastewater had following shortcomings: large amounts of byproduct complicate after processing and bring second pollution and the application was limited. The photocatalytic oxidation technique of TiO₂ has been paid more and more attention for the advantage of less energy cost, mild reaction condition, easy operation, less secondary pollution. The nano-TiO₂ powders and films which are coated on glass were prepared with TNB as raw material by the sol-gel process. We have concentrated on the gelatin time and photocatalytic activity impacted by the water volume and ethanol volume, and studied the relationship between the crystal type of nano-TiO₂ powders and the calcining temperature. The experiments showed that the most suitable process conditions should be controlled as follows: the molar ratio of TNB, water, ethanol and acetic acid was 1:4:14:7, the calcining temperature was 550℃and the calcining time was 1 hour. The experiments showed that the crystal type of nano-TiO₂ would be transformed from anatase to rutile as the calcining temperature climbed. On the above condition ,the ratio of anatase and rutile was 8:2. Metal ions as Fe³⁺ and Pb²⁺ were selected with different molar ratio doping in TiO₂ to study the photocatalyst doping in this paper. The experiments showed that the most suitable process conditions should be controlled as follows: the molar ratio of Fe³⁺ and Ti was 0.05%, the calcining temperature was 550℃; the molar ratio of Pb²⁺ and Ti was 3%, the calcining temperature was 650℃. The experiments of methylene blue photocatalytic degradation showed that the photocatalytic activity could be greatly improved with the dope of Fe³⁺ and Pb²⁺. The porous nano-TiO2 thin films were prepared on glass substrates by sol--gel method. The absorbed wavelength of TiO₂ was enhanced with the dope of Fe³⁺. The effect of Fe³⁺ on the crystal structures and photocatalyic activities of TiO₂ was investigated by XRD, AFM.It is shown that the change temperature of anatase to rutile of Fe³⁺-doping TiO₂ was lower than pure TiO₂, Moreover, the crystallite size of TiO₂ was increase. Doping Fe³⁺ in TiO₂ enhanced the photocatalyic activity of TiO₂ for phenol. This paper also discussed degrading methylene blue under different conditions: the joined quantity of TiO2, the illumination time, the concentration of methylene blue and the air supply. The experiments showed that the most suitable process conditions should be controlled as follows: the joined quantity of TiO2 was 0.3g/L, the illumination time was 2 hours,the concentration of methylene blue was 1×10-5mol/L and the air supply was 1.5L/min. The investigation on dynamics of photocatalytic degradation for methylene blue showed that it was all in agreement with one order dynamics model whether pure TiO2, Fe3+ doped and Pb2+ doped nano-TiO2 used as photocatalysts.