Studies On The Fabrication And Properties Of Photocatalytic Activity Of Doping Nano-TiO₂

Govern-technology of the organic pollution in water environment is becoming one of focal points which domestic and foreign environment worker pay more attention to.The photo-catalytic degradation to organic pollutant has the broad prospect.At present,doping the metallic ion technology is possible to make the Fermi level drift upward,the surface potential barrier change high,the space charge area change narrowly,and separate the photo-production electron-hole obtains effectively,so it enhance the photochemical catalysis performance.However,the method of doping metallic ion into nano-TiO₂ was in the exploration.The products made by impregnation method and the sol-gel method have the properties of high purity,controlling the reaction process easily,operating simply,and so on. This paper used the impregnation method and the sol-gel method to dope Fe³⁺,Cr³⁺,Cu²⁺, Ce³⁺,La³⁺ into nanometer TiO₂,and studied the influence factors to the degradation of 8-aniline-a-naphthalene sulfonic acid and caffeine and their dynamic equations.The results are as follows:(1) The impregnation method uses physical adsorption to dope metallic ion into nano-TiO₂, under the best experimental conditions,the photochemical catalysis active order of nanometer TiO₂ is:La³⁺＞Ce³⁺＞Fe³⁺;Photochemical catalysis activities of multi-combinations doping is lower than that of alone doping,the latter lies in doping the metallic ion after the nanometer TiO₂ takes shape.Because doping mutually ions compete the adsorption position on catalysts surface to decrease the organic matters adsorption,the catalytic activity of the multi-combinations doping are reduced.(2) The sol-gel method uses chemical reaction to dope metallic ion into TiO₂,under the best experimental conditions,the photochemical catalysis active order of nanometer TiO₂ is: Cr³⁺＞La³⁺＞Ce³⁺＞Fe³⁺＞Cu²⁺;among these ions,the combination doping of Cr³⁺,La³⁺ and Fe³⁺ have highest photo-catalysis activities.Because Cr³⁺ and Fe³⁺ have full filling electronic configuration or partly filling electronic configuration,they are easy to release or catch the electrons,and lengthen the life of photo-production electron- hole.Doping La³⁺ into TiO₂ causes the crystal lattice distortion,forming the oxygen vacancy,and it enhances the catalytic activity. (3) Under the same conditions,contrasting of photo-catalysis activity of different methods to prepartion nanometer-TiO₂,the sol-gel method has the highest,the impregnation method is the second,they are better than commodity nanometer TiO₂ and self-made nanometer TiO₂.(4)In this paper,we studied the process of using nanometer TiO₂ photo-catalysis to degrade 8-aniline-a-naphthalene sulfonic acid and caffeine which are difficult to degrade,the results show that they conform to the L-H equation,and follow to first-order decay kinetics.For 8-aniline-a-naphthalene sulfonic acid,the constant of action k=0.2003mg(L^*min)^-1, adsorption constant K=0.074Lmg^-1,4hours' degradation rate is 89.2%;For Caffeine, constant of action k=0.1003mg(L^*min)^-1,adsorption constant K=0.0274Lmg^-1,4hours' degradation rate is 73.2%.These methods to produce nanometer TiO₂ provide the experimental foundation for doping metallic ion into nanometer TiO₂ on industry.It has important practical and therosity significance.