Preparation And Photocatalytic Properties Of TiO₂/Fly Ash Cenospheres Catalytic Material

Pure TiO₂ has attracted much attention of researchers because of its good stability,non-toxicity and low cost.However,there are some deficiencies in practical application.For examples,the photo-generated electron-hole pairs can recombine easily before photocatalysis takes place;its photocatalytic efficiency is low;photocatalyst is difficult to recycle.In view of the above problems,cenosphere-supported La-doped TiO₂/grapheme oxide composite photocatalyst was synthesized,effectively inhibiting electron-hole recombination in photocatalytic process.The photocatalytic efficiency of TiO₂ is enhanced and at the same time the recycle of photocatalyst is realized.In this paper,TiO₂ doped with transition metal elements,rare earth elements,nonmetallic elements and graphene-based composite materials were prepared by sol-gel method,and the photocatalytic activities were investigated.The results show that TiO₂ doped with La or composite with graphene oxide?GO?can significant improve the photocatalytic activity of pure TiO₂.So the effect of the doping concentration of La and the compound amount of graphene oxide on the photocatalytic property was studied.From the XRD characterization of La-TiO₂,it can be learned that La doping can reduce the grain size of TiO₂.The room-temperature photoluminescence?PL?spectra displayed that La doping can inhibit electron-hole recombination.UV-Vis diffuse reflectance spectra showed that La doping can narrow the band gap of sample,causing a red shift in the UV-Vis absorption spectrum.When the mole ratio of La/Ti is 0.50%,the photocatalytic activity is the best.Through the research on the characterization of TiO₂/GO,it can be found that CGO can narrow the band gap of TiO₂,thus increasing the absorbance of the sample in the visible range and promoting the utilization of solar energy.In addition,the electron-hole recombination of TiO₂/GO can also be reduced.When the concentration of GO-composite solution is 0.50%,the photocatalytic activity is the best.Based on the study of La-doped TiO₂ and TiO₂/GO,0.50%La-TiO₂/?0.50%?GO were prepared by sol-gel method,and the photocatalytic activity was investigated.The result shows that photocatalytic performance is better than that of 0.50%La-TiO₂ and TiO₂/?0.50%?GO.The fly-ash-cenospheres-supported photocatalyst was prepared by dipping and fluidized bed spray coating method,and the photocatalytic activity was studied.The results show that The photocatalytic performance of fly-ash-cenosphere-supported 0.50%La-TiO₂/?0.50%?GO prepared by fluidized bed spray coating method for the degradation of methylene blue is comparable to that of powder photocatalyst.The mass density of sample is between 0.70 g·cm-3?0.95 g·cm-3,so it can floate on the water and easy to recovery.The photocatalytic performance of fly-ash-cenosphere-supported 0.50%La-TiO₂/?0.50%?GO prepared by fluidized bed spray coating method for the degradation of two secondary effluent of petrochemical enterprise were studied.And the effects of photocatalyst additive amount and reaction time on the degradation experiment were studied.The results show that when the photocatalytic material adding amount is 4 g·L-1 and reaction time is 1 h,the COD of the wastewater decreases from 65 to 21 mg·L-1.