Study On Preparation And Doping Of TiO₂ Photocatalyst

Wit h industr y deve lopment and populatio n expans ion, safet y of water resources is becoming an issue concerned to all the people,w hile the serio us water pollut ion has intens ified the dema nd for water resources. Photocatalyt ic degradation of pollutants in water has been suggested as an effective method to solve water pollut ion problems. TiO₂ semiconductor has attracted extens ive attent ion from researchers because of its chemica l stabilit y, low-cost, thorough degradat ion in the hazardous organic polluta nt and non- toxic it y. However, TiO₂ se miconductor cannot be used wide ly d ue to its narrow absorptio n range of spectra, the low ut ilizatio n rate of sunlight and the low quantum e ffic iency. The doping modificat ion of TiO₂ can broaden its scope of spectral response and improve its quant um e ffic ie ncy, whic h is an important met hod to increase the acit ivit y o f photoca talys is. In this paper, we stud ied the optimum preparat ion condit io ns of TiO₂ by sol- gel method, narrowed its band gap and improved the photocatalyt ic perfor mance by controlling the morpho logy. The effect of rare earth e leme nt doping on crystal structure, photoche mical properties and photocatalytic activity of TiO₂ was studied. The main results are as follows:?1? TiO₂ powder was prepared by sol- gel method. In the so l- gel process, tera- n- butyl t itanate?TN B? is used as raw mater ia l, ethano l as solvent and glacia l acetic ac id as chelat ing a gents. Four factors and the ir e ffects on ge lat ion t ime and photocatalyt ic act ivit y on degradatio n of met hyl orange are invest igated, name ly, the amount of ethano l added, the amount of water added, the amount of glac ia l acet ic acid added and pH. Meanwhile, the influe nces of s inter ing te mperature and time on photocatalyt ic acit ivity of TiO₂ have also been invest igated. The opt ima l preparation cond itons are as follows : n?C₂H₅ OH?/n?Ti?OBu?₄? = 15; n?H₂O?/n?Ti?OBu?₄? = 4; n?CH₃COOH?/n?Ti?OBu?₄? = 1; pH = 3; baked at 500? for 1 h.?2? The rodlike TiO₂ was synthes ized by sol- ge l met hod, calc inated at 600? for 1 h. The band gap of as-prepared rodlike TiO₂ is narrowed. The influences of the concentrat ions of met hyl orange and catalyst on the degradation rate were invest igated. The rodlike TiO₂ exhib its enhanced photocatalys is performa nce. When the concentrat ions of catalyst and met hyl orange are 0.4 g·d m^-3 and 10 mg·d m^-3, the degradation rate of methyl orange for rodlike TiO₂ reaches 95.7% after irridation for 1 h, while the degradation rate for grainy TiO₂ is just 74%.?3? The photocatalyt ic activit y of La, Ce, Pr and Sm doped TiO₂ were studied systemat ica lly. The research results show that the introductio n of La, Ce, Pr and Sm can increase the phase inversio n te mperature of TiO₂ fro m anatase to rutile, and t here are changes at d ifferent le ve ls toward longer wavele nght hs in absorption band edge. It is fo unded that doped ele ment and its concentrat ion ha ve great effect on photocatalyt ic acit ivit ies of TiO₂, the degradatio n of methyl orange is better wit h RE³⁺- TiO₂ catalyst tha n wit h pure TiO₂. There is an opt imum rare earth ion doping amount for degradatio n of methyl orange, the optimum doping amo unt for La, Ce, Pr and Sm is 1.5%, 0.5%, 0.2% and 0.2%, respectively. We invest igated the stabilit y of photocatalys is for RE3 +- TiO₂ catalysts, the results show t hat the stability o f photocatalys is for RE³⁺- TiO₂ catalysts are, in order, 0.2%Sm- TiO₂, 0.2%Pr- TiO₂, 0.5%Ce-TiO₂, TiO₂, 1.5%La- TiO₂.