| As typical pollutant in indoor air,formaldehyde has great harm to human health and has a long latent period.Therefore,it has of great significance to study the technology for removal of indoor formaldehyde of efficient and continuous.TiO2 photocatalytic can effectively remove formaldehyde without secondary pollution.It is the most promising environmental purification technology at present.However,TiO2 has a narrow photoresponse range and high recombination rate of photocarrier carrier.And due to the small size of nano Ti02,the degradation efficiency of gas-solid reaction is poor,and the powders are easily lost and difficult to recover,which limits its large-scale application.On the other hand,although wallpaper is widely used for indoor decoration,but as an ornament,the functionality of wallpaper is single.Based on this,TiO2 was modified for improving the photocatalytic eff-iciency in this thesis,and combined with wallpaper to degrade indoor formaldehyde,which enhance the practicability of wallpaper,and improve indoor air quality,protect human health.The main work and conclusions are as follows:First,the N-doped mixed-crystal Ti02(N-Ti02)was prepared by the sol-gel method.Using formaldehyde gas as the pattern pollutant and daylight lamp as the light source.The effect of N-Tio2 for degrade formaldehyde gas was investigated by changing different volume ratio of nitric acid V(H/W),the molar ratio of urea to tetrabutyl titanateM(U/T)and the subsequent heat treatment temperature.The results of comprehensive analysis showed that the optimal synthesis conditions as follows:the V(H/W)was 0.1,the M(U/T)was 3,and the subsequent heat treatment temperature was 170 ℃.The N-TiO2 prepared under this condition was coated on the wallpaper and the degradation rate of formaldehyde gas reached 78%within 6 hours.Secondly,N-doping of commercially available mixed-crystal TiO2(P25)was modified by hydrothermal method.The effect of N-P25 for degradation of formaldehyde gas was investigated by changing the hydrothermal reaction temperature,the hydrothermal reaction time and the M(N/Ti).The results of comprehensive analysis showed that the optimal synthesis conditions of N-P25 as follows:the hydrothermal reaction temperature was 150 ℃,the hydrothermal reaction time was 20 hours,and the M(N/Ti)was 18.The N-P25 prepared under this condition was coated on the wallpaper and the degradation rate of formaldehyde gas reached 87%within 6 hours.Finally,the technological conditions of coating photocatalyst on wallpaper were discussed.The photocatalytic wallpapers prepared by different processes were comprehensive compared in physical properties and photocatalytic properties,and the optimum process was selected.The effects of photocatalytic wallpapers for degrade formaldehyde gas by changing light source,photocatalyst coating amount,and initial concentration of formaldehyde were investigated,as well as the photocatalytic decay period of the wallpaper.The dynamic model of Langmuir-Hinshelwood was established,and the results showed that under the conditions of different initial concentration of formaldehyde,the photocatalytic degradation of formaldehyde by photocatalytic wallpaper was basically consistent with the first-order reaction kinetics of L-H. |
