Study On Application Of Photocatalytic Method To Remove Organic Contaminant In Indoor Air

The micro-size particles of TiO2 oxide used as photocatalyst were prepared by TiCl4 hydrolysis. The property characterization and activity evaluation of TiO2 were performed. The effects of pH value and calcination temperature on the catalyst particle size, crystal form and transition temperature from anatase to rutile were also examined. Agglomeration state of the powder was improved greatly through hot dipping with absolute alcohol or freeze-drying the gelatinous precipitate, almost no hard agglomerate formed. The effects of the water dosage, pH value and alkalify mode in the preparation process on the photocatalytic activity of TiO2 were examined, and the optimum preparation conditions were also determined by orthogonal design.The micro-size particles of TiO2 doped with transition metal Co and rare earth element Ce were prepared. The property characterization and activity evaluation of doped TiO2 were also performed. The grain growth of TiO2 can be checked by doping Co and Ce, and doping Co has greater check action. The doped TiO2 has higher activity than pure one, and the changes of photocatalytic properties relate to doping mode and dopants. The activity of photocatalyst doped by coprecipitation is higher than that of by mechanical blend. Among them, the catalyst doped with Co has higher activity than the one doped with Ce. The transition from anatase to rutile can be accelerated by doping Co, but the effect of doping Ce on the transition is not obvious.TiO2 film supported on glass plate and particles on activated carbon and medicinal stone "maifanshi" (MFS) were prepared by sol-gel method, and the scanning electron microscope (SEM) characterization and activity evaluation of the catalysts were also performed. Experimental results show that the supported TiO2 film can not be used in gas-phase photocatalytic system because of the poor adsorptivity. The supported catalysts on activated carbon and MFS have better adsorptivity, so the activity in gas-phase photocatalytic reaction of benzene is higher than that of unsupported TiO2.The effects of use level of catalyst, contact area, light intensity, initial benzene concentration and moisture content on gas-phase photocatalytic degradation reaction of benzene were examined, and a possible photocatalytic degradation mechanism was inferred. It is proved by combining reference conclusions that the photocatalytic degradation reaction of benzene in gas-phase has different reaction mechanism under different reaction conditions.Kinetic equation of gas-phase photocatalytic reaction of benzene was established and verified. The reaction rate constant and adsorption equilibrium constant in the equation were determined by means of initial concentration method. The mathematical model of gas-phase photocatalytic reactor was established, and the analytic and numberical results under unstable state conditions were obtained. Because the real changes of reaction rate constant during different reaction step were considered, experiment and model had almost identical results. The air purifier with photocatalytic action was made up, and purification ability was evaluated in high concentration system of benzene. Experimental results show that the purifier have powerful purification ability, it was still able to keep very good purification effect in the destructive test in high concentration system of benzene.