Study On Degradation Of Formaldehyde Gas In Visible Light By Nanometer Titanium Dioxide Fabric

Nano titanium dioxide is non-toxic and can be reused, enabling pollutants more thoroughly degraded without secondary pollution. Formaldehyde has been widely used in industrial material. Thus the air pollution caused by formaldehyde is also becoming more and more serious. It is a very promising method to purify the formaldehyde in air by nano titanium dioxide. However, the application of titanium dioxide in the treatment of formaldehyde pollution is restricted by some problems. First, the photocatalytic activity of nano TiO₂ is too low. Second, nano TiO₂ can be only activitied by UV-light. Third, the photocatalytic process is easily influenced by the reaction conditions. In this paper, we mainly do reaches on these problems.Nano TiO₂ was prepared by sol-gel method. The composite photocatalytic material of cotton fabric loaded TiO₂ （TiO₂/CT） were prepared by two dip and two rolling technique. The effect of four conditions （the concentration of butyl titanate, alcohol dosage, reaction time, reaction temperature） on the photocatalytic properties of TiO₂/CT was investigated by single factor variable method. The methylene blue was used as the target to test the activity of the composite photocatalytic material under the UV lamp of main wavelength of 254nm. We found that the best preparation process was:concentration of butyl titanate=9.1%,Ⅴ（alcohol）/Ⅴ（TBT）=0.5, reaction time= 120min, reaction tempreture= 60℃.Ag and Fe doped nano titanium dioxide were prepared respectively. Glass fiber supported Ag doped nano titanium dioxide （Ag-TiO₂/GF） and glass fiber supported Fe doped titanium dioxide （Fe-TiO₂/GF） were prepared respectively by impregnation and calcination. The surface morphology of glass fiber fabric was observed by scanning electron microscope （SEM）. And the absorption properties of the composite material were investigated by UV-Vis diffuse reflectance spectra. The formaldehyde gas was used as the target to test the activity of the composite photocatalytic material under high pressure mercury lamp. It was found that the surface of the glass fiber was significantly changed after loading. The addition of different proportion of Fe and Ag made the absorption properties of the catalytic materials different. The greater the metal element was, the stronger the absorption ability of the catalytic material was. The addition of Fe and Ag can enhance the purification ability of the catalyst under visible light. But the amount of these elements was not better to add more. Among them the best Ag content was 1.5%, and the best doping amount of Fe was 1%.The effects of initial concentration of formaldehyde, light intensity, and loading number on the purification efficiency of formaldehyde under visible light were studied. The experimental results showed that with the increase of the initial concentration of formaldehyde, the purification of formaldehyde first got better and then worse. When the initial concentration of formaldehyde was 94μg/L, the purification effect of the catalyst was the best. With the increase of light intensity, the purification rate of formaldehyde increased gradually. When the distance between the reaction vessel and the light source were 20cm and 80cm respectively, the purification effects had a difference of 40%. When the load number was twice, the catalytic performance of the material was the best.