Research On Synthesis And Modification Of Nano Titanium Dioxide For Photo-Catalyst Materials

This paper mainly consisted of two sections, review and experiments.The structural characteristics, photo-catalyzing mechanisms, synthesis methods,modification methods, applications and development of nano TiO₂ materials werereviewed in the review section. The synthesis of nano TiO₂ and ferric-doped nanoFe-TiO₂ prepared by precipitation and co-precipitation methods was described in theexperiments section, in which titanium tetrachloride and ammonia were acted as rawmaterials, iron nitrate nonahydrate was acted as doping reagent, and anhydrous ethanolwas acted as solvent, respectively. Anhydrous ethanol, sodium dodecyl sulfonate, andpolyvinylpyrrolidone were used to disperse intermediate products in the process of thesynthesis. Effects of reaction conditions on crystal types, morphology, and particle sizeof the materials were systematically discussed, and the effects of reaction conditions onthe disciplinarians of UV-Vis absorption spectrums in the materials were also discussed.The primary research contents were introduced as follows:The second chapter: titanium tetrachloride and iron nitrate nonahydrate in variousqualities were put into anhydrous ethanol, getting the different solutions in Fe/Ti molarratios. The precipitations of relevant constituents were gained, in which ammonia wasutilized to adjust pH of ferric/titanium solutions. Then the precipitations were aged atroom temperature before they were washed by anhydrous ethanol and dried, in whichthe dry ferric/titanium gel was obtained. Finally, the nano Fe-TiO₂ was obtained bycalcining the dry gel. Meanwhile, the pure nano TiO₂ was synthesized on the samereaction conditions. The iron doping contents, calcination temperatures, and calcinationtimes were altered to observe the effects of reaction conditions on the crystal types,morphology and UV-Vis absorption spectrums of the obtained products. It wasdemonstrated that the nano Fe-TiO₂ which was prepared by calcining dry gel (Fe/Timolar ratio was 3.8%) at 800℃for 6 h was better dispersive particles which possessedmixed crystal structure, the absorption edge of the nano Fe-TiO₂ was shifted to thevisible light region most compared with the pure nano TiO₂ according to the UV-Visabsorption spectrum.The third, fourth chapter: The surfactants powder of sodium dodecyl sulfonate andpolyvinylpyrrolidone with certain amounts were put into the anhydrous ethanol solutions which were comprised of titanium tetrachloride and iron nitrate nonahydratein various qualities, mixed round, then the precipitations of relevant constituents weregained, in which ammonia was utilized to adjust pH of ferric/titanium solutions. Theprecipitations were aged at room temperature before they were washed by distill waterand dried, the dry gel dispersed by suffactants was get. Finally, the nano Fe-TiO₂ wasgained by calcining the dry gel. The iron doping contents, the suffactants amounts,calcination temperatures, and calcination times were altered to observe the effects ofreaction conditions on the crystal types, morphology and UV-Vis absorption spectrumsof the obtained products. It was demonstrated that polyvinylpyrrolidone could promotethe decentralization of products, while sodium dodecyl sulfon-ate could not facilitate thedecentralization of products evidently. The absorption edge of the nano Fe-TiO₂ whichwas prepared by calcining dry gel (Fe/Ti molar ratio was 0.38%-3.8%) at 400℃for 3h was shifted to the visible light region most compared with pure nano TiO₂ accordingto the UV-Vis absorption spectrum.The fifth chapter: The pure nano TiO₂ (anatase) which was acted as precursor wasput into NaOH solution and mixed round to form a suspension, then the suspension wasput into the sealed autoclave and dealt with hydrothermal treatment. The concentrationsin NaOH solution, hydrothermal temperatures, and hydrothermal times were altered toobserve the effects of reaction conditions on the crystal types and UV-Vis absorptionspectrums of products. It was demonstrated that the band gap energy of the obtainedproduct which was prepared by the pure TiO₂ by hydrothermal treatment at 150℃for 1d in a solution of 8 mol/L NaOH was reduced obviously compared with that of thepure nano TiO₂, but the absorption of the obtained product in the visible light regionafter 400 nm was slender. The morphology changes of the hydrothermal products couldnot promote the absorption edge shifting to the visible light region.The sixth chapter: The ferric/titanium solution (the molar ratio= 37.9% in Fe/Ti)in which titanium tetrachloride and iron nitrate nonahydrate were acted as raw materialswas put into anhydrous ethanol, the precipitation of relevant constituent was gained inwhich ammonia was utilized to adjust pH of ferric/titanium solutions. It was testifiedthat the Fe-TiO₂ products possessed impurity phases. The calcination temperatures werealtered to observe the effects of temperatures diversification on the crystal types andUV-Vis absorption spectrums of the obtained products. The absorption edge of theFe-TiO₂ with impurity phases was shift to visible light range remarkably compared with that of the pure nano TiO₂. The spectrum absorption of the Fe-TiO₂ containing impurityphases was very strong in the visible light region, namely the presence of impurityphases in the Fe-TiO₂ enhanced the absorption of the products in the visible light regiongreatly.The obtained intermediate products and materials were characterized by XRD,UV-Vis, SEM, TEM, DSC-TGA, IR, Raman, and FL/PL.