Study On Preparation And Application Of N-doped Nano-TiO₂

It is considered that nano titanium dioxide is the most potential environmentalmaterial in environmental treatment field because of many advantages, such as higherphotocatalytic activity,untoxicity,steady chemistry character,cheapness and so on.This paper aimed to improve on the disadvantages of wider band gap and reclaimingdifficulty of nano titanium dioxide and speed industrialized application bynitrogen-doping and loading on kaolinite. It had been prepared that bothnano-titanium dioxide (N-doped nano-TiO₂) and Nitrogen-doped titanium dioxideloaded on kaolinite (N-doped nano-TiO₂/kaolinite) with photocatalytic activity undervisible-light. The reactive process and mechanism of degradation to azo-dye andpesticide wastewater were also researched by the photocatalysts. The summing-up isas follows:1. It were researched that preparating and condition of the pohotocatalysts. Thecomposite system was prepared with sol-gel technique. The optimization processparameters of N-doped nano-TiO₂ were: Ti(OC₄H₉)₄-CH₃CH₂OH-N(CH₂CH₂OH)₃-H₂O-NH₃=1:15:2.5:15:5 for the ratio of mole number of the sol precursor.The N-doped nano-TiO₂ was prepared by hydrolyzation in 60℃and then calcinationat 500℃for 4h. The optimization process parameters of N-doped TiO₂/kaolinite were:Ti(OC₄H₉)-4-CH₃CH₂OH-N(CH₂CH₂OH)₃-NH₃·H₂O=1:30:2.5:5 for the ratioof mole number of the sol precursor. The N-doped nano-TiO₂/kaolinite was preparedwith 6 percent of the kaolinite mass concentration, by hydrolyzation in 50℃,dryingat 70℃and then calcination at 500℃for 4h.2. The sample was characterized and analysed on crystal and molecularconfigurations and surface appearances by XRD,FTIR,Raman and SEMtechnologies. The results indicated that kaolinite surface was uniformly covered withTiO₂ particles with high crystallization of anatase phase. Nitrogen replaced oxygen ofTiO₂ and made up of Ti-N chemical bond. Under certain temperature, nitrogencumbered phase change of TiO₂ from anatase to rutile.3. The degradation and decoloration to azo-dye wastewater were studied.N-doped nano-TiO₂ and N-doped nano-TiO₂/kaolinite were adopted to dispose wastewater and the experiment results showed when the initial absorbance of azo-dyewastewater was 0.200, the catalyst concentration was 0.25 g/L and the UV-lightirradiation time was 50 min, the decoloration rate were 99.3 percent,99.0 percent anddegradation rate of COD were 98.6 percent,97.8 percent. Compared with N-dopednano-TiO₂, N-doped nano-TiO₂/kaolinite not only shortened degradation time, butalso was propitious to reclaim and recycle.4. The degradation to O,O-dimenthyl-O-2,2-dichlorovinyl phsphate (DDVP) wasstudied under UV-light and simulant solar-light. When initial concentration of DDVPwas 10 mg/L and catalyst concentration was 0.2 g/L, the degradation was researched.With UV-light irradiation on DDVP for 50 min by N-doped nano-TiO₂/kaolinite, thedegradation rate was 97.4 percent. Reaction rate was accelerated by adding certainoxidant into reaction system. The pH value of the solution influenced the degradationrate. The degradation performance was better in acidic and alkalescent conditionsthan neutral condition.Nano-TiO₂/kaolinite and N-doped nano-TiO₂/kaolinite were adopted to degradedDDVP under Xe-light irradiation for 150 min, and the degradation rate wererespectively 51.3 percent and 93.4 percent. The results indicated N-dopednano-TiO₂/kaolinite behade photocatalytic activity under both UV-light andvisible-light.