Preparation of Modified TiO2 PhotoAcatlyst and Photocatalytics Degradation of Formaldhyde

　　Preparation of Modified TiO2 PhotoAcatlyst and Photocatalytics Degradation of Formaldhyde
　　As the pollution of formaldehyde(HCHO)is worsening in indoor.A number of studies related to the removal of HCHO have been carried out for several decades.In these methods,photocatalytic oxidation has been widely attracted.TiO2 is close to being an ideal photocatalyst in several respects:nontoxic,low cost,high stability, strong oxidizing.But the photocatalytic degradation is inefficiency because of their own limitation.So this work have used rare earth to compound with TiO2 in order to improve photocatalytic activity of TiO2.In this paper,the CeO2/TiO2 compound powders with Ti/Ce molar ratios from 1./0.8 to 1/2.5 were prepared by solid state process.The properties of Block Neodymium magnets compound powders including crystal structure,the properties of spectral absorption,the electronic structure and chemical state of surface were analyzeded and characterized by means of DSC-TGA,XRD,UV-Vis,XPS,PL,FT-IR etc.the Ag/CeO2/ TiO2 compound powders with were prepared by solid state process.The properties of compound powders were analyzeded and characterized by the experiments of photocatalytic degradation in formaldehyde.The results of experiment have proved that:1)The crystal phase of the powders sintered at 800℃were still anatase.This implied that the phase transition of TiO2 could be inhibited by doping CeO2,and the phase transition temperature of TiO2 was improved;
　　2)In the compound powders,as the valence states of Ti or Ce have been changed,the surface oxygen vacancies and adsorption oxygen were increased,and the concentration of hydroxyl of the compound powders were increased;3)The results of FT-IR demonstrated that the surface of CeO2/TiO2 compound powders easilier absorbs water than that of pure TiO2,and contains a large number of hydroxyl;4)The wavelength absorption threshold of TiO2 doped with CeO2 was red-shift to 450nm,and enhanced the absorption of visible light;5)Appropriate content of Ce could decline the intensity of PL spectra,as TiO2 with CeO2 molar ratio of 1:1.5,the PL spectra intensity is the weakest.But increased the molar ratio of TiO2 and CeO2,the PL spectra intensity was increased. http://www.999magnet.com   The results of photocatalytic degradation of formaldehyde shown:1)The degrading rate of formaldehyde by the CeO2/TiO2 powders was 82.4%.It was 2.3 times than that of P25,which is obviously higher than P25 under the common daylight lamp;2)The degrading rate of formaldehyde by the Ag/CeO2/TiO2 powders was 95.91%.after degradation of six days,the concentration of formaldehyde is 0.02 mg/l,which is below the national standard value,the efficiency is obviously higher than CeO2/TiO2 and P25 under the common daylight lamp.The best parameters obtained by the experiment of photocatalytic degradation of formaldehyde:the molar ration of TiO2 and CeO2 was 1:1.5;the sintering temperature was 500℃;the sintering time was 2.5 h,the humidity was about 53±3 %RH,the optimal quantity of formaldehyde was 0.5 ml(1%),the amount of photocatalyst was 5 g.At the same time,we found that the effect of reaction temperature wasn’t obviously in the process of the photocatalytic degradation.In this work,we generally adopted the temperature about 15-40℃.By investigate the doping effect of CeO2 and Ag/CeO2 in TiO2,the results of this work indicated that the absorption of visible light could be enhanced,and the utilization of sunlight could be improved in TiO2 doped with CeO2 and Ag/CeO2,the degrading rate of formaldehyde could be improved under the visible light