The Preparation And Photocatalytic Performance Of TiO₂-based Composite Photocatalyst

The photocatalytic technology is a new technology in the field of environmental pollution control because of low cost,relatively mild reaction conditions and high efficiency of degradation of pollutants.The researchers have been paid more attentions to the semiconductor photocatalysts.However,the photocatalytic activity of most of the semiconductor photocatalysts is unsatisfactory because of narrower absorption spectrum and the easy recombination of electrons and holes.The researchers prepared many new photocatalysts by doping method,surface sensitization method,recombination method.In this paper,TiO₂/ZnO microsphere was prepared.TiO₂/CaSO₄ whisker composite was prepared by a carrier of CaSO₄ whisker.The photocatalytic properties of two photocatalysts were studied on different light sources.Then using odium copper chlorophyllin to sensitize two photocatalysts.Their photocatalytic effects on methylene blue solution,Cr⁶⁺solution and Lake water were studied on ultraviolet or visible light.The main results are as follows:1)TiO₂/ZnO microsphere,TiO₂ microsphere and ZnO microsphere were prepared by sol-gel method and hydrothermal synthesis method.The samples were characterized by SEM and XRD.The effects of different TiO₂ content to photocatalytic performance of TiO₂/ZnO microsphere were studied.The results showed that when the mass ratio of TiO₂ to ZnO was 1:1,the photocatalytic performance of TiO₂/ZnO microsphere was better.The effects of reaction pH on the photocatalytic activity of TiO₂/ZnO microsphere were investigated.The results showed that the degradation efficiency of methylene blue solution was higher when the reaction pH was 8,and the maximum decolorization rate of methylene blue solution was 85%after 180 minutes.The reduction effect of Cr⁶⁺solution was better when the reaction pH was 2.The maximum removal rate of Cr⁶⁺solution was 72%after 120 minutes.The photocatalytic performances of TiO₂/ZnO microsphere,TiO₂ microsphere and ZnO microsphere were compared on ultraviolet or visible light.The results showed that whether on ultraviolet or visible light,the photocatalytic performance of TiO₂/ZnO microsphere is better than those of TiO₂ microsphere and ZnO microsphere.2)TiO₂/CaSO₄ whisker composite was synthesized by sol-gel method and hydrothermal method.The samples were characterized by SEM and XRD.The results of photocatalytic experiments showed that when the mass ratio of TiO₂ to CaSO₄whiskers is 1:1,the photocatalytic performance of TiO₂/CaSO₄ whisker composite is better.And the photocatalytic activity of TiO₂/CaSO₄ whisker composite is better than that of TiO₂ powder catalyst.In the photocatalytic experiment of TiO₂/CaSO₄ whisker composite,the degradation effect of methylene blue solution was better when the reaction pH was 8.And the decolorization rate of methylene blue solution reached 77%after 180 minutes.The reduction effect of Cr⁶⁺solution was better when the reaction pH was 2.And the removal rate of Cr⁶⁺can reach 69%after 120 minutes.The photocatalytic performance of TiO₂/CaSO₄ whisker composite on ultraviolet light is better than that on visible light.3)Using odium copper chlorophyllin to sensitize TiO₂/ZnO microsphere and TiO₂/CaSO₄ whisker composite.Samples were characterized by UV-Vis.The results of photocatalytic experiments showed that the photocatalytic performance of the sensitized samples was better.And the photocatalytic activity of the sensitized samples on visible light was better than that on ultraviolet light.The results of photocatalytic experiments of lake water showed that the concentration of NH₃-N and COD in lake water decreased obviously after photocatalytic experiments.The concentration of NH₃-N can be reduced to 0mg/L and the concentration of COD can be reduced to 12.92mg/L after the photocatalytic experiments by sensitized TiO₂/ZnO microsphere.The photocatalytic effect of the sensitized photocatalysts of in lake water on visible light was better than that on ultraviolet light.It has practical value in the field of water environmental pollution control.