Preparation Of TiO₂-based Photocatalyst And Its Application In Cement-based Materials

As a new type of semiconductor material,TiO₂has the advantages of cheap price,no toxicity,simple preparation process,good chemical stability,and high photocatalytic activity,which makes TiO₂used in various fields.However,due to the large band gap of TiO₂,its photocatalytic reaction can only occur in the ultraviolet region,and the electron-hole pairs generated by TiO₂during the photocatalytic reaction are easy to recombine.In this paper,the TiO₂photocatalyst was prepared through the following three aspects,so that the spectral response range of the TiO₂photocatalyst expanded to visible light,and the TiO₂photocatalyst was applied to cement-based materials.?1?TiO₂/metakaolin composite powders with different calcination temperature and different TiO₂loading was prepared by using uniform precipitation method with raw materials of metakaolin,Ti?SO₄?₂and urea.The crystal structure and morphology of TiO₂/metakaolin composite powders were investigated by XRD and SEM,and its photocatalytic activity of the as-prepared sample was evaluated by degradation of methyl orange under simulated sunlight.The TiO₂/metakaolin composite powders with high catalytic performance was studied.Combined with cement stone surface,a cement-based material with photocatalytic properties was prepared.?2?Using iron sulfate,titanium sulfate,urea,and polyethylene glycol as raw materials,nano-Fe/TiO₂composite powders was prepared by co-precipitation-uniform precipitation method,and the structure and morphology of nano-Fe/TiO₂composite powders were characterized by XRD and SEM.The photocatalytic activity was studied using simulated sunlight as the light source and methyl orange as the target degradation product.A cement-based material with photocatalytic properties was prepared by combining nano-Fe/TiO₂composite powder with high catalytic performance and the surface of cement stone.?3?The TiO₂/g-C₃N₄composite materials were prepared by a uniform precipitation method and the structure and morphology were characterized for g-C₃N₄and TiO₂/g-C₃N₄composites by XRD and SEM.The photocatalytic activity of the as-prepared sample was evaluated by degradation of methyl orange under simulated sunlight.The composite materials with high catalytic performance was combined with the cement stone surface to obtain the photocatalytic cement stone.According to experimental studies,it is concluded that:?1?The photocatalytic performance of the TiO₂/metakaolin composite powders calcined at 500°C is the best,and the degradation rate reaches 93.39%under simulated sunlight for 4 h,and when the concentration of Ti?SO₄?₂is 0.3 mol/L and 0.5 mol/L,the photocatalytic effect of the obtained TiO₂/metakaolin composite powders is better.The impurity elements in metakaolin extends the photocatalytic reaction range of TiO₂to the visible region.The calcination temperature is 500?,and the concentration of titanium sulfate is 0.3 mol/L,40%TiO₂/metakaolin composite powders replaces the TiO₂/metakaolin cement-based material prepared by cement.Catalytic degradation of methyl orange solution under simulated sunlight conditions can reach 70%the above.?2?Fe-doped TiO₂composite powders with Fe content of 0.6%and 0.9%have strong photocatalytic performance.Under simulated light conditions?500 W xenon lamp?,the methyl orange solution can be degraded,and it can reach 90%or more in 2 hours.The activity is high.The Fe doped TiO₂composite powder with 0.6%Fe still has good photocatalytic performance after three cycles.The degradation rate of 0.6%Fe-doped TiO₂cement-based material can reach 72.5%in 7 hours under the condition of simulating sunlight to degrade methyl orange solution.?3?The TiO₂/g-C₃N₄composite materials prepared at 300?and 400?have a strong heterojunction,and N-doped TiO₂was produced at 500?.The best photocatalytic activity of TiO₂/g-C₃N₄composite materials was obtained at 400?,and the degradation rate reached 91%under simulated sunlight for 60 min.By fitting calculation,it was found that the photocatalytic rate of TiO₂/g-C₃N₄composite materials obtained at 400?is fastest.The cement stone combined with the TiO₂/g-C₃N₄composite materials obtained at 400?still has good catalytic degradation performance,and the degradation rate can reach more than 90%under simulated sunlight for 240 minutes.