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Layered tantalum tungstate -based catalyst modified pillared study

Author: XuBaiHuan
Tutor: LinBiZhou
School: Huaqiao University
Course: Materials Science
Keywords: Tantalum tungstate Peel - heavy accumulation Doping modification Pillared Photocatalytic
CLC: O643.36
Type: PhD thesis
Year: 2011
Downloads: 33
Quote: 0
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Abstract


The problem of environmental pollution caused by toxic organic compounds has become a major problem restricting the development of human civilization today. Eliminate environmental pollution need to consume a lot of energy, bring greater the impact of increasingly depleted energy issues, the photocatalytic degradation technology is considered to be one of the most potential ways to solve this problem, therefore, the research and development The high-performance photocatalyst materials has become a major topic of widespread concern in the international community. To this end, the thesis focuses on how to effectively use this critical 43% of visible light in solar, modified pillared layered LiTaWO 6 catalytic materials prepared tantalum tungstate-based composite photocatalyst. Consider LiTaWO 6 is a low specific surface area, non-porous material, and organic pollutants is generally large composite catalyst introduced in the mesoporous structure in tantalum and tungsten acid group, it is necessary to meet the reactants and products in the Two key need to spread rapidly in the pore mesoporous structure and catalytic activity of visible light of a thesis. In this thesis, the means of XRD, TG, SEM, UV-Vis, IR, BET, XPS and surface potential of characterization of the composite structure of the catalyst, nature study, and discuss its photocatalytic performance. Specific studies are as follows: 1. Using high-temperature solid-phase method successfully synthesized doped the tantalum the Tungstate Li 1 3x the Ta -x the Co. x WO 6 of Li 2x Ta 1-x RE x WO 6 (RE = Nd, Pr, Er). Li 2 CO 3 the Ta 2 O 5 the WO 3 , Co The (CH 3 COO) 2 · 4H 2 O and rare earth oxides as raw materials, preparation of a series of different doped calcined at 900 ° C miscellaneous content layered tantalum, tungsten the the acid doped material Li 1 3x the Ta 1-x Co x WO 6 and the of Li 1 Ta 2x 1-x RE x WO 6 . XRD, UV-Vis diffuse scattering spectrum, XPS, BET, such as the composition of the material, structure, and optical absorption properties and metal ion doping characterized; photocatalytic activity was evaluated by degradation of methylene blue on its . Research results show that the the cobalt doping improves the photocatalytic activity of layered tantalum tungstate-based photocatalyst, and rare earth doping can not be achieved of tantalum tungstate catalytic activity visible light, but largely methylene blue-violet outside light photocatalytic activity, which, RE doping molar content of 0.5% doped sample, the highest degradation activity of methylene blue. The the experimental obtained Li 1 3x the Ta -x Co x the WO 6 or Li 1 2x Ta 1-x the RE x WO protonated product H 6 nucleotide exchange 3x the the TA 1-x Co x . WO 6 , ultrasonic disintegration with TBAOH reaction, successfully peeled into a single molecular layer, the peeling rate of 90 %. ζ potential measurement and analysis showed that at a pH of 5 1 1 within the scope of the surface ζ potential of substantially constant (-61 -63mV), the sol is relatively stable, its isoelectric point at pH = 1. Peel using a modified heavy accumulation of technology successfully prepared mesoporous structure Co-TaWO 6 intercalation materials. At room temperature, the ultrasonic vibration, tantalum, tungsten acid monolayers with cobalt acetate reaction, successfully prepared cobalt intercalated tantalum tungstate composite. XRD analysis showed its layer spacing increments of only 0.3 nm, but N 2 adsorption isotherm - desorption analysis showed that the sample exists 4.1 nm mesoporous peak than the table plot for 34 m 2 g -1 . Thermal analysis showed that the pillared composite material has good thermal stability. UV-Vis diffuse scattering spectroscopy, infrared spectroscopy, XPS test intercalation composite primary interaction between objects, the UV-Vis absorption edge redshifts. The research results show that the degradation of methylene blue under visible light, cobalt-doped material of Li 3x Ta 1-x the Co. x WO < visible light photocatalytic activity sub> 6 compared to cobalt intercalation significantly improved layered tantalum tungstate-based catalyst. Its activity is further enhanced because the combined the material structural characterization of the results of reasonable discussion. Peel using a modified heavy accumulation of technology successfully prepared with mesoporous structure the REO y- TaWO 6 (RE = Nd, Pr, Er) intercalation materials. Sonicated at 60 ° C, tantalum, tungsten acid monolayers with rare earth sol reaction, the successful preparation of a rare earth intercalation tantalum tungstate composites. XRD analysis showed that the interlayer spacing in increments of 0.45 nm; the the N 2 adsorption isotherm - desorption analysis showed that the sample exists 4.1 nm mesoporous peak, more than 50 Table plot < sup> 60 m 2 g -1 ; thermal analysis showed that the pillared composites have better thermal stability; UV-Vis diffuse scattering spectrum , infrared spectroscopy, XPS test results show that the interaction between the the intercalation composite main, object, resulting in the UV-Vis absorption edge slight red shift, but did not, and the visible region; methylene blue catalytic degradation studies have shown that, with rare earth doped samples Li 1 2x the Ta -x the RE x WO 6 , rare earth intercalation failed to achieve tantalum tungstate photocatalytic activity of visible light, but it can greatly improve the photocatalytic activity under ultraviolet light. 4 in the preparation of synthetic Li 2x Ta 1-x , the RE x the WO 6 and Co-TaWO, 6 binary composite systems based on improved stripping heavy accumulation of technology successfully prepared for the first time the mesoporous structure Co-the Ta 1-x RE x < / sub> the WO 6 (RE = Nd or Er) ternary complex intercalation materials. I.e. at ambient temperature, under ultrasonic vibration, the reaction of the rare-earth-doped layer of tantalum and tungsten acid nanosheet cobalt acetate, prepared by Co-Ta 1-x RE x WO < sub> 6 composite intercalation materials. The structural characterization of XRD, TG, UV-Vis, IR, BET, SEM, XPS and other materials, and its photocatalytic degradation of methylene blue visible light. The results show that, with the of Li 1 2x the Ta -x RE x WO 6 and Co-TaWO 6 binary composite systems compared, Co-Ta 1-x RE x the WO 6 composite intercalation materials with more high visible photocatalytic activity, wherein the RE-doped molar content of 0.5%, Co-Ta 1-x RE x WO 6 The photocatalytic activity of the composite intercalation material is best. Further enhance its activity and RE doping content on the catalytic activity of the reasons for a reasonable discussion. As of Co-Ta 1-x RE x WO 6 composite system comparison the preparation synthetic Li 1 3x < / sub> Ta 1-x Co x WO 6 and the REO y- TaWO 6 binary composite systems based on improved stripping heavy accumulation technology successfully prepared mesoporous structure the REO y- Ta 1-x Co x the WO 6 (RE = Nd or Er) ternary complex intercalation material. Its material structure characterization and evaluation of its photocatalytic degradation of methylene blue. The research results show that, due to the quantum size effect, the modified method failed to achieve layered tantalum tungstate matrix composites photocatalysis under visible light, however the REO y- Ta 1-x Co x WO 6 UV photocatalytic activity of the composite intercalation material is superior to the REO y- TaWO 6 binary complex system, which is doped with cobalt molar content of 0.5% the photocatalytic activity of the best. 5 by stripping - heavy accumulation of technology and sol-gel technology combined successful preparation of SnO 2 - and Ta 1-x Co x WO 6 and SnO 2 - Ta1-xNdxWO 6 pillared composite by XRD, N 2 and other adsorption isotherm - desorption analysis showed that the layer spacing in increments of 2.05 nm, the plot than table for 90 m2 / g exist 4.0 nm mesoporous peaks. Thermal analysis show that the thermal stability of the pillared composite. UV-Vis diffuse scattering spectroscopy, infrared spectroscopy, XPS test results show that, SnO 2 - Ta 1-x Co x WO 6 and SnO 2 - Ta1-xNdxWO 6 pillared composite main object of strong interaction between the UV-Vis absorption edge redshifts , O 1s binding energy increased. Degradation of methylene blue visible light that SnO 2 - Ta 1-x Co x WO 6 and SnO 2 - the Ta1-xNdxWO 6 Pillared composite material has higher photocatalytic activity.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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