Studies On The Preparation And Modification Of Photocatalytic Activity Of Titania By Hydrothermal Method

Titania has been widely used in the fields of environmental protection, solarenergy conversion, sunscreen cosmetics, textile, paint, rubber, et al due to theadvantages of high photocatalytic activity, toxic-free and low cost. In some fields thedisadvantages of the low quantum efficiency and the wide energy-band-gap which canonly utilize a small fraction of the solar energy restrict the application of titania forlarge-scale production. And in other fields the durability especially the light-stableability of titania needs to be strengthened.Based on different requirements in different fields and the application forlarge-scale production metatitanic acid (intermediate product in industry) was used asthe raw material and studies on the preparation of titania and modification ofphotocatalytic activity were carried out by hydrothermal method. Through themodification of titania photocatalytic activity can not only be promoted but also beinhibited.1. Studies on the Preparation of Nano-titania and Their Isoelectric PointsNano-titania powders were synthesized at different temperatures from 150 to200℃ for different hours from 2 hours to 8 hours by hydrothermal method usingmetatitanic acid as reactant. Through the characterizaton of XRD and TG , thecondition of 200℃ and 6 hours was selected as reaction condition in the laterhydrothermal experiments.Nanometer titania powders were synthesized in different pH conditions byhydrothermal method at 200℃ for 6h. Powders were characterized by Zetapotential,XRD and TEM.The crystal structures of the powders are all anatase. Isoelectric points of thepowders prepared in hydrothermal conditions of pH 1,3,5,11,13 are 5.5.Isoelectricpoints of the powders prepared in hydrothermal conditions of pH 7,9 are 4.5.The pHof the acid solution in hydrothermal conditions decreased after reaction, but the pH ofthe alkaline solution increased after reaction. iABSTRACT2. Studies on the Preparation of Sb2O3-doped TiO2 Nanopowders byHydrothermal Method and the Inhibition of Their Photocatalytic ActivitiesThe method for the evaluation of the photocatalytic activity of the titaniapowders was determined. The synthesized powder with a mass of 100 mg was mixedwith 100 mL rhodamine B with a concentration of 4.0mg·L-1. The aqueous suspensionwas irradiated by ultraviolet ray for 30 minutes.Two kinds of Sb2O3-doped TiO2 (Sb2O3:TiO2=0.070~0.35mol%) nanopowderswere prepared by hydrothermal method at 200℃ for 6h. The first kind ofSb2O3-doped TiO2 was synthesized by using titania and antimony trichloride asreactants. The second kind of Sb2O3-doped TiO2 was synthesized by using metatitanicacid and antimony trichloride as reactants. The Sb2O3-doped TiO2 powders werecharacterized by XRD, SEM, EDS, TG, IR and the diameter of the particles was alsoevaluated by Scherrer equation.EDS characterization shows that Sb2O3 exists in Sb2O3-doped TiO2. Thecrystalline of all samples is anatase in XRD patterns. The doping of Sb2O3 can inhibitthe particle growth of the second kind of Sb2O3-doped TiO2 when the crystalline ofmetatitanic acid is changed into anatase TiO2. The photocatalytic activities ofSb2O3-doped TiO2 were characterized by photodegradation of rhodamine B. Thephotocatalytic activity of Sb2O3-doped TiO2 was effectively suppressed by the dopingof Sb2O3. When Sb2O3:TiO2 is 0.21%, the photocatalytic activity of Sb2O3-doped TiO2is the lowest. The photocatalytic activity of the second kind of Sb2O3-doped TiO2 islower than the first.3. Studies on the Preparation of Composite Semiconductors and the Enhancementof Their Photocatalytic Activities.Two kinds of SnO2/TiO2 (Sn:Ti =1.0~9.0mol%) nanopowders were prepared byhydrothermal method at 200℃ for 6h. The first kind of SnO2/TiO2 was made byusing titania and tin tetrachloride as reactants. The second kind of SnO2/TiO2 wasmade from tin tetrachloride and metatitanic acid which converts to anatase TiO2during hydrothermal process. Samples were characterized by...