Preparation And Application Of TiO₂ With Visible Light Catalytic Activity

Photocatalytic oxidation is a new technology studied in the last two decades.It is original and promising to treat dyeing wastewater with photocatalytic oxidation,which has been studied a lot both at home and abroad.Dyeing wastewater also can be purified by this method.It is able to transform organic compounds into H₂O,CO₂ and mineral acid thereby destroy the pollutants.TiO₂ is representative because of its high chemistry stability,ability to resist light corrosion,nontoxic property,and low capital, high photocatalysis activity which could induce and accelerate some endothermic reactions on the surface of TiO₂ which is radiated by the light.To obtain a more efficient utilization of solar or indoor light,some attempts were made to extend the absorption range of titanium dioxide into the visible-light region by the introduction of a donor level by doping or surface modification.And artificial zeolite was used to immpbilze TiO2.In this study,the main research work and innovation include:1.A series of nitrogen and ZnFe₂O₄ co-doping TiO₂ nanoparticles were prepared by precipitation processing.Effects of the variation of ZnFe2O₄-dopant,calcination temperature,the amount of ethanol and ammonia on photocatalytic degradatibility were then respectively investigated.And the best preparation condition under simulant sunlight was obtained.The co-doped nano-titania was characterized with XRD and TEM techniques.The results indicated that the iron-doped nano-titania with an average diameter of 15nm contained anatase as the main phase and rutile phase.It was found that the ferric ion dopant of a proper concentration promoted the photocatalytic property of the TiO₂ nanoparticles.The photodegradation rate of methyl orange under simulant sunlight was near upon 80%.2.A series of nitrogen and Ce co-doping TiO₂ nanoparticles were prepared by precipitation processing and characterized and explained by XPS and XRD techniques. Effects of the variation of Ce-dopant,calcination temperature,the amount of ethanol and ammonia on photocatalytic degradatibility were then respectively investigated. And the best preparation condition under ultraviolet radiation was obtained.The results indicated that the Ce doping is favorable to enhancing the absorption of visible and UV light of nano-TiO₂.It suggested that Ce doping increases the photocatalytic activity of nano-TiO₂,and has the optimum content of Ce in Ce/TiO₂ existed.The results showed that the decolorizing efficiency of methyl orange can reach 99.0%by using Ce doping 0.05%(molar fraction)in Ce/TiO₂ as heterogeneous photocatalyst,with initial concentration of methyl orange is 20 mg·L -1,amount of catalyst = 0.100 g,pH=6.4, ultraviolet illumination time = 40min.3.Prepared the TiO₂/zeolite and the N,Fe co-doped TiCVzeolite immobilized photocatalyst.Compared with N,Fe co-doped TiO₂ nanoparticles catalyst,the immoblized catalyst showed higher catalytic properties.The results showed that the methyl orange degradation rate of immoblized catalyst under UV increased 9%.After repeated use of the catalysts will have deactivation phenomena.After the inactivation, photocatalyst can be regenerated by a means of 'washing - roasting - ultraviolet light exposure',which can basically resumed its catalytic oxidation capacity,and makes its life longer.Zeolite immobilized catalyst not only facilitate recovery,but also has durable activity.After six repeat photocatalytic degradation of regenerated experiments, the results can be attained about 80%.The research results indicated that the immobilized nanoparticle TiO₂ with high photocatalytic activity under various light sources can be synthesized by doping with nitrogen or co-doping with nitrogen and other element.The preparation method has some merits,such as simple,high efficiency,and easily to operate.These research work has some theoretical and practical value on the application of TiO₂ photocatalytic oxidation technology in pollutants decomposition.