Catalytic Degradation Of Formaldehyde By Nano-titanium Dioxide Supported On Nano-fibers

In recent years,with the continuous development of urbanization and industrialization,the problem of environmental pollution has become increasingly serious.Titanium dioxide photocatalyst has attracted much attention of people because of its good chemical stability,non-toxicity and low cost.However,there are some shortcomings in the process of photocatalytic degradation,such as small contact area,easy agglomeration,difficult separation,low photon utilization efficiency and so on.These disadvantages can be improved by loading the titanium dioxide on carriers with high specific surface.This paper mainly includes three aspects:(1)In this paper,nanocrystals were prepared by hydrothermal method using tetrabutyl titanate as raw material and diethanol amine as surfactant.The optimum conditions for preparing titanium dioxide by hydrothermal reaction were determined by varying reaction temperature,reaction time and PH value of solution.At the same time,the size of titanium dioxide particles was characterized by XRD.The degradation efficiency of formaldehyde by titanium dioxide catalysts under different wavelengths irradiation and light intensity was measured.And the effect of the number of times of use on the catalytic activity of titanium dioxide was also discussed.The results show that the prepared titanium dioxide is anatase type.When hydrothermal reaction temperature is 200 ℃,reaction time is 8 hours and PH is 4,the catalytic efficiency of titanium dioxide is the best.The catalytic activity is best under irradiation of violet light having a wavelength of λ = 365 nm.When the light intensity increases,the degradation rate increases and then reaches saturation.(2)In this paper,nano-polyacrylonitrile fibers and prepared titanium dioxide were used as raw materials to prepare composite catalysts by impregnation method.The degradation of formaldehyde by composite catalysts prepared under different soaking time and temperature conditions was investigated.At the same time,the effects of loading amount of titanium dioxide,initial concentration of formaldehyde,different light intensity on the results and the reusability of the composite catalyst after loading were investigated.Experimental results show that the composite catalyst has stronger ability to eliminate formaldehyde.When the impregnation time is 12 h,the temperature is 60 ℃,and the initial concentration of formaldehyde is 1.8 mg/m3,the best one is obtained.The degradation effect was enhanced with the increase of light intensity.The degradation of formaldehyde was affected by the number of times of use.After 6 times of reuse,it remained at about 60%.(3)In this paper,binders were used to modify PAN nanofibers/nano-titanium dioxide catalysts to improve their weak bonding.The effects of the amount of binder,the number of loading layers,the initial concentration of formaldehyde and the number of rubbing times on the degradation rate of formaldehyde were investigated.Meanwhile,the catalytic effect of Ti O2 catalyst,PAN nanofiber supported titanium dioxide catalyst and PAN nanofiber/nano titanium dioxide/chitosan catalyst on formaldehyde were compared.The results show that the catalytic efficiency is improved by using chitosan as binder,but the catalytic efficiency is decreased when the chitosan is too much.The number of layers is 4 layers,and the initial concentration of formaldehyde is 1.7mg/m3,which has the best catalytic efficiency.The number of washes and uses has an effect on the catalyst,but the effect is still good.