Studies On Preparation And Doping Of Titanium Dioxide

Heterogeneous photocatalytic oxidation by semiconductor catalyst is one of a few advanced oxidation processes. Due to high oxidation potential for the species such as hydroxyl radials (·OH) generated from irradiated catalyst, recalxitrant and toxic pollutants can be efficiently decompoded to H₂O, CO₂.Titanium dioxide (TiO₂), especially its anatase phase, is one of the most promising photocatalysts because of its high photocatalytic activity, high chemical stability, low cost and non-toxicity. However, the application of anatase only limit to UV (wavelength<387nm ) photocatalysis. It is of great significance to endow TiO₂ photocatalyst with a visible-light response. Thus, the solar energy can be utilized as the light source in photocatalytic reaction. Since last decade TiO₂ has been endowed with visible-light response by doping with some transition mental ions or mental oxide. Unfortunately, there are some disadvantages for TiO₂ doping with mental ions, including thermal instability and easiness from carrier charge recombination center. This thesis is to study the preparation, characterization and catalytic properties.TiO₂ is synthesized by sol-gel, sol-combustion, sol-emulsion- combustion, steatric acid system sol-gel method. The photocatalyst prepared by steatric acid system sol-gel method show highest photocatalysis under ultraviolet ray. Rutile own 62% percent and better mixing effect. It have the same photocatalysis as P25 produced by Degussa.Fe³⁺x/ZnO_y-TiO₂ nanoparticles are prepared from butyl titanate (Ti (Bu) 4) using sol-combustion, sol-gel, steatric acid system sol-gel method. The result show that 1%Fe/20%ZnO-TiO₂ prepared by Sol- combustion is the better photocatalyst. In the sunlight, the methylic orange declined degradation efficiency of the solution is up to 94% after 60 min. After the solution of methyl orange is illuminated for 40 min with the sun light as light source, the degradation efficiency of 1.5%ZnFe₂O₄-TiO₂ is up to 98.8%..La³⁺,Ce⁴⁺,Eu³ and La³⁺+Eu³⁺, Ce⁴⁺+Eu³⁺doped nano-titania is synthesized by sol-gel method. The experimental results indicate that: La,Eu doping in TiO₂ could improve its photocatalytic efficiency. Also, the efficience of codoping is better than single doping TiO₂. Ce⁴⁺have little influence to photocatalyti. 1%La+1%Eu codoped TiO₂ degrade methyl orange, pH=3.0, the degradation ratio of methyl orange come up to 98.5% in sunshine about 40 min. The Photocatalytic activity of co-doped La³⁺1%+Eu³⁺1% nanosized titania was studied by degradation methyl orange, PH=3.0, the degradation ratio of come up to 99% in sunshine about 50 min.Preparation of palygorskite supported titanium dioxide is mixtured titanium dioxide that is prepared by sol-combution with palygorskite that is purified from separation wiht Na(PO₃). palygorskite supported with TiO₂ is prepared by dryed at 200 °C from the suspension of palygorskite and TiO₂ powder. The result of XRD show that particles belong to anatse structure and rutile structure, the proportion of palygorskite and titanium dioxide is 6:1.The photocatalytic activity is evaluated in methyl orange under the sunlight .the result show that the activity was best when the content of power was 1.0g and the activity is superior to that of pured titanium dioxide power. The degradation ratio of palygorskite supported with TiO₂ come up to 90% in sunshine about 20 min.