Experimental Research On The Degradation Of Indoor Benzene By Photocatalysis Of Iron-doped TiO₂ Film

Most of the materials used in decorating contain formaldehyde, volatile organic compounds and some other things which are bad to people's health. Those compounds emit continually, and cause the indoor air quality (IAQ) decline heavily; Along with the popularization of air-condition system, on the one hand people enhance the airproof and the heat insulation of buildings, on the other hand they decrease the standard of least fresh air. The consistency of indoor pollutant grows for not been diluted by the fresh air, and make the IAQ deteriorate badly. How to improve the IAQ, and supply a healthy indoor environment, it has become a focus that people pay more and more attentions to.People should be most care about the organic pollution of indoor air, which mainly contains the formaldehyde, benzene and its'homologs. At present, the main ways to treat with the organic pollution of indoor air include biological techniques, physical techniques, and chemical techniques. Photocatalysis is a new chemical technique which comes up these years. Under the effect of photocatalyst (titanium dioxide), pollutants were decompounded into some harmless substance, like CO2 and H2O. This technique is an indoor air purifying mean which have the best develop future, for its'gentle react condition, little secondary pollution and less cost for run, especially for it is possible to use daylight as the light source.However, using TiO₂-photocatalytic technique to purify indoor air is still beginning. It needs to be improved in some aspects, including how to increase the electron production of TiO₂, how to enhance the efficiency of visible light use,how to improve the method to load catalyst, and how to treat with the mid-productions.The iron-doped TiO₂-photocatalytic film was prepared by the improved Sol-Gel method, and the optimum parameters were confirmed through a group of orthogonal test. The iron-doped TiO₂ film prepared with the optimum parameters was loaded on the faces of enamel tiles and active carbon fiber (ACF),the surface morphologies and crystalline properties were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM). The photocatalytic activity of the iron-doped TiO₂ film was studied through experiments, and the factors such as light source, initial concentration of benzene, and airflow were discussed. At last, the serviceable abilities of TiO₂-photocatalytic films were investigated, including the renewable ability and the load-fastness.The results indicated that:Each parameter has some influence to the thin film's phocatalytic activity while the improved Sol-Gel method was adopted to prepare the iron-doped TiO₂ thin film. Through a group of orthogonal test, the optimum parameters are as follows: PEG 1.2 wt%, Fe³⁺ 0.05wt%, calcine time 2.0 hrs, and calcine temperature 500℃.The XRD and SEM tests showed that the prepared TiO₂ was mostly presented to be anatase and rutile. The particle size is about 28.5nm, and distributing equably. The iron-doped TiO₂ thin film displayed well photocatalytic activity when used to deal with the benzene pollutant. Light sources which have the potential to produce O3 conduce to better activity; Shorter wavelength conduces to better photocatalytic activity; The photocatalytic activity shows a non-linear growth trend as the increase of the illumination intensity; in a range of benzene's low-concentration, The degradation efficiency increases as the initial-concentration grows; And the airflow has some influence to the degradation efficiency-highest when airflow comes face to the thin film, and lowest when airflow comes from back of thin film; Further more, the doped of Fe³⁺ increased the response of TiO₂ to visible-light. Even under the irradiation of incandescence-light, the iron-doped TiO₂ thin film can displays some kind of photocatalytic activity.Loading TiO₂ to the surface of ACF has little affect to the ACF's absorption active-sites, on the contrary, the traits of ACF and TiO₂ can make up the short of each other and lead to a better degradation efficiency of benzene pollutant, and the secondary pollution can be avoided.Both enamel tiles and ACF loaded TiO₂ thin films have good renewable ability and load-fastness, the serviceable abilities are favorable. At the end of this thesis, an indoor air purify instrument based on the ACF/TiO₂ was designed. It is considered to be feasible that at the beginning after ornamenting, using ACF/TiO₂ air purify instrument have a great effect on dealing with the indoor air pollution, after a period of time, just only the enamel tiles can keep the indoor air cleaning.