Preparation Of TiO₂ And Degradation Of Photocatalytic Formaldahyde From Water By TiO₂

The nanometer TiO₂ has been the focus of photocatalyst studies because of its non-poisonous feature high activity,security,stability,low cost and other advantages.The application is extremely good.Electron-hole pairs wil be generated upon excitation by light with energy equal to or greater than the bandgap of TiO₂. Since the strong oxidative pwer of the photogenerated holes makes it possible to oxidize most of the organic pollutants and to transform some of the toxic inorganic pollutants into harmless forms as well,photocatalysis of TiO₂ is significant for environmental remediation. At present,the nanometer TiO₂ is often used as a catalyst for the organic pollution. Formaldehyde is a kind of colorless toxic substance and it can do harm to our body and warmedblooded animal. It has carcinogenic and teratogenic effects Formaldehyde in the water is the main environmental pollutants from industrial waste water.This research aimed at removal of formaldehyde from water using photocatalysis and nano-TiO₂ and metal ion doped nano-TiO₂ ,that were prepared by a sol-gel method. The oxidation and reduction capability of the thin film have been studied comprehensively from some important factors of the photocatalytic formaldehyde decomposition in the reaction and different TiO₂ film were prepare.With the help of X-ray diffraction(XRD),after a series of experiments with using the new photoreactor which was built by ourselves,we studied many facators affecting the photocatalytic activity of TiO₂ films.More information was provided to optimize TiO₂ film photocatalyst and its may be helpful for further study of photocatalytic mechanisms. Some results are as follows.(1) TiO₂ and co-doping TiO₂ with metal ions were synthesized with the acetic acid and the acetylacetone as the inhibitor by sol-gel method . Under such conditions,the degradation rate can be enhanced that the catalysts using the acetylacetone as the inhibitor performed and under 600℃roast temperature,the TiO₂ was best. The XRD shows that the TiO₂ film wa made up mauly by rutile type and little anatase type.(2) The oxidation and reduction capability of the thin film have been studied comprehensively from some important factors of the photocatalytic formaldehyde decompose in the reaction, such as in acidic condition and alkaline condition,the initial concentration of formaldehyde,the smaller size of catalyst particles,the existences of churn dasher and air-breather,the quality proportion of anatase type and rutile type,etc. After 380nm UV irradiation, the results show that the pH of the aqueous solution is 7;the initial concentration of formaldehyde is 20 mg/L;the size of catalyst is 180 head with the existences of churn dasher and air -breather, the quality proportion of anatase type and rutile type is 1: 1,ratio of the solution is 5gTiO₂/L ,under such conditions,the degradation rate can be enhanced to about 96.72% when TiO₂ film was used.(3) The oxidation and reduction capability of the co-doping TiO₂ film with metal ions as Cu²⁺,Ni²⁺,Pb²⁺,Zn²⁺,Fe³⁺ have been studied comprehensively from some important factors of the photocatalytic formaldehyde decompose in the reaction, the results show that TiO₂ photocatalysts co-doped with Pb²⁺ can gain the best degradation efficiency and the degration can be enhanced to 99.23%.(4) Discuss and analysis the the mechanism of the photocatalysis degradation of formaldehyde by using TiO₂. According to the reaction process and results the possible reaction process of formaldehyde degradation can be speculated.These results maybe helpful to design and construct photocatalyst which using to decompose formaldehyde with high activity.