The Experimental Research On The Degradation Of Indoor Formaldehyde By Photocatalysis Of La-doped TiO₂ Film

Formaldehyde, one of the main indoor airborne pollutants, is considered as dubious carcinogen by WHO and EPA and become a focus that people play more and more attentions to.In many ways to treat with the organic pollution of indoor air, nanometer TiO₂ photocatalysis technology is a purificatory measure which possess quite developmental potential in recent year. However photocatalytic activity of TiO₂ and the efficiency of visible light use need to be improved. The purpose of this paper is improving photocatalytic activity of TiO₂ and the efficiency of visible light use by doping with La, and using La-doped titanium dioxide photocatalysis films to treat with formaldehyde of indoor air.In this paper, La-doped titanium dioxide photocatalysis films loaded on the face of glass were studied, and the optimum doping conditions were confirmed through a group of orthogonal test. The La-doped TiO₂ films prepared by Sol-Gel method on the basis of the optimum doping conditions were loaded on the face of glass and ceramic tile by dip-coating method separately and were loaded on gypsum board by powder-sintering method, and photocatalytic activity of TiO₂ films loaded on these building materials was studied. The crystalline properties and surface morphologies of TiO₂ films were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM). In this paper, the factors of La-doped TiO₂ films photocatalytic activity such as light source (wavelength and illuminance), initial concentration of formaldehyde were discussed. At last, the renewable ability and the load-fastness of La-doped TiO₂ films and the visible light transmittance of La-doped TiO₂ film glass were investigated.The results indicated that:â‘ In this experiment,through a group of orthogonal test, the optimum doping conditions of La-doped TiO₂ films loaded on the face of glass were as follows: PEG 0.03at%, La³⁺ 0.3at%, the best doping mode: doped on a bottom layer.â‘¡The XRD and SEM tests showed that the prepared TiO₂ was presented to be anatase . The particle size is about 20nm, and distributing equably.â‘¢The La-doped TiO₂ thin films displayed well photocatalytic activity when used to deal with formaldehyde. Shorter wavelength conduced to better photocatalytic activity; The photocatalytic activity showed a growth trend with the increase of the illumination intensity; In a range of formaldehyde's low-concentration, the degradation efficiency increased as the initial-concentration grew; Further more, the doped of La³⁺ increased the response of TiO₂ to visible-light. Even under the irradiation of incandescence-light, the La-doped TiO₂ thin films can display some kind of photocatalytic activity.â‘£In this experiment, the TiO₂ thin films loaded on the face of glass and the TiO₂ thin films loaded on the face of ceramic tile were prepared by the same preparation technology,but the photocatalytic activity and the increased range of photocatalytic activity of the TiO₂ thin films loaded on the face of glass were different from that of the TiO₂ thin films loaded on the face of ceramic tile. This shows that the photocatalytic activity of the TiO₂ thin films prepared by Sol-Gel method and dip-coating method has some connection with substrates type and the increased range of photocatalytic activity of the TiO₂ thin films depends on the interaction effect between ion-doped and substrates.⑤The La-doped TiO₂ thin films loaded on the face of glass have good photocatalytic activity , renewable ability and load-fastness, in addition , La-doped TiO₂ film glass has good visible light transmittance, which can meet actual needs. Therefore, La-doped TiO₂ film glass used in interior decoration can play a role in purifying indoor air.