Study On The Synthesis, Characterization And Photocatalystic Properties Of Ag And N Codoped Supported Titanium Dioxide Nanoparticles

With the development of industry, more and more drainage volume of azo dye wastewaters enter into water through different kinds of ways, which made serious pollution in water enviroment. The azo dye wastewaters are complicated in constitution, deep in color and difficult to be degraded. TiO2semiconductor photocatalytic oxidation is a new-style pollution treating approach in degradating dyeing waste water, whose virtues are high treatment efficiency, operating condition controlling easily, simple technics equipment, low price, no toxicity and chemical stability, etc. However TiO2as photocatalyst has two major problems. Firstly its photo quantum yield value is also very low due to its photo-excited electron-hole pairs easily recombining. Secondly TiO2as a high surface area powder is easily to agglomerate and difficultly to recover from solution. This paper aimed at enhancing the photocatalysis properties of nano-TiO2and reovered from solution.The major work includes the following aspects:(1) The photocatalytic activity of samples was influenced greatly by processing parameter using tetra-n-butyl titanate as the precursor, acetic acid as the hydrolyzed inhibitor and ethanol as solvent. The L9(34) Orthogonal Design experimental results show that the optimum hydrolysis temperature is V [Ti(OC4H9)4]:V (HAC):V (H2O):V (C2H5OH)=3:2:5:14, calcining temperature is450℃and the sequence of each influcing factor is:dosage of wate＞calcining temperature＞amount of nitric acid＞dosage of ethanol. Under the UV lamp, the methyl orange degradation rate by Pure TiO2sample under the optimal preparation condition is26.4%within1h. Pure TiO2were analysis by cyclic voltammogram curves, the result was consist with photodegradation.(2) The Ag-TiO2、N-TiO2、Ag-N-TiO2powders were prepared by sol-gel method, AgNO3as Ag source and urea as nitrogen source. Under the guidance of the theoretical calculation, The samples were characterized by XRD、TEM and EDS. Furthermore, in order to test the photocatalytic activity of the samples, degradation was investigated under the UV lamp. The samples were analysis by cyclic voltammogram curves. The results showed that, the samples were of anatase TiO2and doping of Ag and N inhibited the transformation from the anatase to rutile phase. The photocatalytic activity of TiO2was improved by doping with appropriate content Ag or N. The optimal doped molar fraction of two kinds of transition metal ions both were0.05percent. Compare to single-doped TiO2, photocatalytic activity of TiO2could be improved further by co-doping. This was ascribed to the fact that there was a cooperative action in the two doped elements. Under the UV lamp, the methyl orange degradation rate by0.05%Ag-TiO2、0.05%N-TiO2、0.05%Ag-0.05%N-TiO2sample under the optimal preparation condition is50.0%、41.3%、62.6%within1h. which is higher than that of pure TiO2(26.4%) under the same experimental condition. The result of analysis by cyclic voltammogram curves was consist with photodegradation.(3) The TiO2/SiO2photocatalysts were prepared using sol-gel technique in this work. This research uses the ion doping to modify TiO2on base of investigating TiO2supported on SiO2photocatalyst, selected metal Ag and nonmetal N has prepared the adulterating TiO2/SiO2by using the sol-gel method, and characterized by FTIR、XRD、TEM and EDS. Furthermore, in order to test the photocatalytic activity of the samples, degradation was investigated under the UV lamp. The samples were analysis by cyclic voltammogram curves. The results showed that, there is a Ti-O-Si bond between TiO2grains and SiO2matrix. The photocatalytic activity of TiO2was improved by supported on SiO2. The optimal supported fraction of SiO2was40percent. Under the UV lamp, the methyl orange degradation rate by40%TS、0.05%Ag-40%TS、0.05%N-40%TS、0.05%Ag-0.05%N-40%TS sample under the optimal preparation condition is41.9%、59.5%、46.3%、73.6%within1h, which is higher than that of pure TiO2(26.4%) under the same experimental condition. The removal rate of methyl orange solution over Ag,N co-doped TiO2/SiO2was higher than that of Ag or N single doping. Because of the SiO2is not semiconductor, the result of analysis by cyclic voltammogram curves were not consist with photodegradation.(4) γ-Fe2O3was coated on the titanium dioxide surface directly via sol-gel technology. In this study SiO2layer as isolation between γ-Fe2O3layer and TiO2layer, prepared composite photocatalytic material TiO2/SiO2/γ-Fe2O3. Selected metal Ag and nonmetal N have prepared the adulterating TiO2/SiO2/γ-Fe2O3by using the sol-gel method. The samples were characterized by XRD、TEM and VSM. Furthermore, in order to test the photocatalytic activity of the samples, degradation was investigated under the UV lamp. The results showed that, XRD patterns show that the diffraction peaks of TiO2are agree with the characteristic peaks of anatase TiO2in standard line to ensure the efficiency of the catalyst. TEM pattems show monodispersed nanocatalyst with typical core-shell structrue was successfully obtained. The magnetic photocatalyst particles were easily separated and recovered using magnetic separation. The photocatalytic activity of TiO2was improved by supported on SiO2/γ-Fe2O3. The optimal supported fraction of SiO2/γ-Fe2O3were40percent. Under the UV lamp, the methyl orange degradation rate by40%TSF、0.05%Ag-0.05%N-40%TSF sample under the optimal preparation condition is42.2%、74.3%within1h, which is higher than that of pure TiO2(26.4%) under the same experimental condition.