Study On Nanometer-TiO₂ Film Immobilized On The Wire Netting And Photocatalytic Application

Titanium dioxide has been known as an excellent photocatalytic material.Most organic pollutants which are difficultly decomposed through chemical and biological methods can be degraded into CO₂,H₂O and other small inorganic molecules by titanium dioxide.Furthermore,there are lower cost,good chemical stability and high photocatalytic activity of titanium dioxide,so it has promising application in environment protection,such as air purification,wastewater treatment,antibacterial, self-cleanness and so on.The technique of TiO₂ photocatalytic oxidation is one of the focuses in the field of environment protection in around the world.There are many disadvantages by use of aqueous suspensions of TiO₂ in practical applications,such as easily deactivated,agglomerated,difficultly separated,and will produce secondary pollution.Some researchers are exploring the technique that immobilizing nanometer TiO₂ on the surface of carriers.The main purpose of the paper was to study a kind of preparation technique of titanium dioxide photocatalyst which will easily be renewed, not be agglomerated and with high photocatalytic activity.The research contents are as follows:1.With tetrabutyl titanate(Ti(OC₄H₉)₄) as the precursor,ethanol(C₂H₅OH) as the solvent,diethanolamine(NH(C₂H₅O)₂) and acetylacetone(CH₃COCH₂COCH₃) as stable reagent,the influencing factors and the mechanism of TiO₂ sol-gel process was studied.The results show that changes of the ratio of some ingredients have a great effect on stability of sol.The optimal molar ratio of reactants in TiO₂ sol system is:Ti(OC₄H₉)₄:H₂O:C₂H₅OH:NH(C₂H₄OH)₂:AcAc=1:5:25:1:0.3.Under the experimental condition,TiO₂ sol is more stable,and could be stored for a relatively long time.2.Nanometer titanium dioxide photocatalytic films immobilized on the stainless steel wire netting were prepared by sol-gel and dip-coating methods.The crystal phase,grain size and surface morphology of the films were characterized and analyzed by XRD,FTIR and other modern testing techniques.With azo dye as the degradation target,the factors which affect the photocatalytic activity of immobilized titanium dioxide films were investigated in detail,such as the calcination temperature, coating times,initial concentration of azo dye,pH value of solution,light sources and so on.The results indicate that there is high photocatalytic activity when the films coated five times and calcined at 600～700℃for 2 hours.The decolorization rate of azo dye is 99.07 percent as initial concentration of azo dye equal to 27 mg/L and illuminated for 3 hours by Uv-light.3.In ordor to increase the photocatalytic activity,the metal ion doping method has been used to modify the immobilized titanium dioxide films.The results show that dopping metal ions of Ag⁺ or Zn²⁺ may improve the photocatalytic activity.The optimum doping concentration of Ag⁺ and Zn²⁺ is 1%(molar ratio between metal iron and Ti).The films coated five times appear excellent photocatalytic activity when calcined at 700℃for 2 hours.XRD spectrum show that doping metal ions of Ag⁺ or Zn²⁺ would inhibit the anatase transforming into the rutile in different extent.4.The photodegradation reaction kinetics of azo dye has been studied.The experiment show that the reaction accords with Langmuir-Hinshelwood kinetics equation.The reaction rate constant is proportional to initial concentration of azo dye. The reaction rate constant of Ag⁺-TiO₂ film is the biggest,and the half-life is the least.