Preparation Of Nanosized Titanium Dioxide Thin Films Materials And Study On Its Photocatalytic Performance

has been considered to be an important photocatalytic material due to its many advantages such as high efficiency, low cost, non-toxicity, and good chemical stability. Compared with suspended TiO2powder as photocatalyst for water treatment, immobilized TiO2thin film does not need to be separated after water purification. Therefore, the film type of TiO2photocatalyst has been paid more attention. In this dissertation, TiO2thin films have been prepared by a dip coating sol-gel method. The photocatalytic performances of TiO2thin films have been systematically investigated. The main research work and conclusions can be summarized as follows:In this dissertation, The Ti sol is composed of titanium isopropoxide, absolute ethyl alcohol, de-ionized water, acetyl acetone and Tween-20. Tween-20, as a kind of surfactant r, is used to modify TiO2films. The properties of the as-prepared TiO2films have been characterized by XRD, SEM, UV-visible spectrometer and BET. The effect of important preparation parameters, including the molar ratio of H2O/titanium isopropoxide, pH of the sol, calcinations temperature, the dip coating speed and number, on the structure and photocatalytic activity of the as-prepared TiO2films are investigated. The experimental results show that TiO2films is obtained under the conditions of acid sol, H20/titanium isopropoxide molar ratio of7:1,20℃of reaction temperature,33mm·s-1of dip-coating peed, which has good light transmission and UV absorbance. And TiO2particles attached to the surface of glass uniformly.The photocatalytic properties of TiO2thin films have been studied using methylene blue as a model pollutant in water. Some important factors that may affect photocatalytic properties of TiO2films in the reactor have been analyzed. A comparative study on photocatalytic properties of immobilized TiO2films with suspended TiO2particles has been discussed. And the stability of the film has been analyzed. The conclusions are as follows: adding Tween-20into Ti sol can obviously increase photocatalytic efficiency of TiO2thin films; the increase of photo catalytic dose, water, coating cycle all can improve the photo catalytic efficiency and have the best value;. With the enhancement of calcinations temperature, the degradation rate of methylene blue increases firstly and then decreases, the optimum temperature is450℃; our experimental results have confirmed that photocatalytic activity of TiO2thin film is less than that of suspended TiO2powders. In addition, the photocatalytic degradation rate of methylene blue by TiO2films under ultraviolet light radiation is higher than that under visible light radiation; increasing initial concentration of methylene blue can lead to the decrease in the degradation rate of methylene blue. The stability of the as-prepared TiO2thin films is good.The photocatalytic oxidation kinetics of TiO2films on the degradation methylene blue has been studied and analyzed. The conclusions are as follows:the reaction kinetics constant can be enhanced by increasing catalyst loading until the optimum catalyst loading can be reached; with the increase of initial concentration, the photocatalytic rate constant decreases; the pH value of solution is an important factor for the influence of photocatalytic rate constant, it seems that adding HNO3or NH3-H2O into the reaction liquid can lead to the enhancement in the reaction rate constant. In addition, with the increase of the amount of water in the sol, the reaction rate constant increases; there is also optimum calcinations temperature (i.e.,450℃) for the highest reaction rate constant. The photocatalytic oxidation of methylene blue by the TiO2films can be described by a Langmuir-Hinshelwood (L-H) model. It can be found that the photocatalytic oxidation reaction of methylene blue belongs to a first-order reaction.