| Solar energy is a kind of huge and renewable energy source, and rational use of solar energy is one of important approaches to achieve green and sustainable development. Selective light transmitting material can transmit part of the sunlight selectively, such as visible light, so as to realize the adjustment and use of the solar energy transmittance. Transparent conductive material is a kind of selective light transmitting material. Tungsten bronze as a new-type of transparent conductive material, has appropriate band gap(2.4 ~ 2.8 e V) and high concentration of free electrons. As compared with the conventional transparent conductive materials, such as ATO, ITO, FTO, etc, tungsten bronze which possesses many advantages such as low cost, non-toxic and strong selective light-transmitting ability, has become one of the current research hotspots.Among the many preparing methods of tungsten bronze, hydrothermal method employs water as the solvent, and inorganic salt as the reaction material. The preparation process is environmental friendly, and the dispersibility of the product is very good. Also the subsequent use is very convenient, hydrothermal method has a natural advantage in the preparation of green energy in nanomaterials. This issue employed a simple hydrothermal method to prepare tungsten bronze nanocrystallines, and studied the effects of precipitating agent, doping elements on the phase, microstructure, adsorption and optical properties of the product. The main research details and conclusions are as follows:(1) With ammonium tungstate((NH4)10W12O41·5H2O) as tungsten source, citric acid(C6H8O7·H2O) as stabilizer, Hydrazine hydrochloride(N2H4·2HCl) as reducing agent, hydrochloric acid(HCl) as precipitant, ammonium tungsten bronze((NH4)xWO3) nanomaterials was synthesized by one step hydrothermal method, and the effect of concentration of HCl on the nanocrystals was studied. Experimental results show that pure hexagonal(NH4)xWO3 nano-rods with a [001] preferential growth direction could be obtained with HCl concentration below 7.67 mg·m L-1. Higher HCl concentration results in the formation of WO3·H2O(9.86 mg·m L-1) and(NH4)10W12O41(12.05 mg·m L-1). Adsorption experimental results show that the(NH4)xWO3 nanocrystals have excellent adsorption ability for methylene blue(MB, simulated organic dye pollutants). The average cycle adsorption removal ratios of the MB aqueous in 10 mg·L-1 could reach ~ 85%; while the removal ratio of the MB aqueous in 40 mg·L-1 is ~ 80%. Further more, the organic dye methylene blue which adsorbed on the surface of(NH4)xWO3 could be simply removed after heating at 250 oC for 2 h in air, and the heated nanocrystals still exhibit good adsorption ability for MB in aqueous solution. The average removal ratios of the MB aqueous in 10 mg·L-1 could reach ~ 90%.(2) Based on the optimum acid content, molybdenum materials was added to the reaction mixture. The effect of two different sources of molybdenum and the molybdenum content on the morphology and optical properties of the synthesized product was researched. Experimental results show that the molybdenum content almost has no influence on the morphology of the nanocrystals which synthesized with ammonium molybdate as the molybdenum source, all of the product are short rods. The morphology of the nanocrystals synthesized with sodium molybdate as the molybdenum source changes from short rod into similar lamellar gradually. The near infrared shielding ability of the product of doping molybdenum has increased a little. Taking the ammonium molybdate doping for instance, the infrared transmittance at 858 nm of the sample with Mo/W(mol) = 3:5 is 1.78%, and the visible transmittance at 422 nm is 47.2%. With sodium molybdate as the molybdenum source, the infrared transmittance of the sample with Mo/W(mol) = 1:5 at 866 nm is 2.6%, and the visible transmittance at 414 nm is 47.4%. Zeta potential results show that the sample synthesized with ammonium molybdate as the molybdenum source has a better stability.(3) Based on the optimum acid content, then palladium chloride aqueous solution(0.01 g·m L-1) was added to the prepared tungsten bronze dispersion. Taking advantage of the reducing ability of tungsten bronze to in-situ loaded nano palladium particles, the influence of the palladium content on the morphology, photocatalysis and adsorption properties of the product was studied. Experimental results show that the color of the nanocrystals changed from blue to pale yellow after palladium loaded, charactering that the tungsten had been oxided. Microstructure analysis shows that palladium particles not only load on nanorods, but also exist as nanoparticles with homogeneous precipitation. The sample of loaded palladium barely has catalytic property. However, it possesses excellent adsorption ability. The cycle adsorption removal ratios of methylene blue in the concentration of 10 mg·L-1 are 85 ~ 98% of the loaded palladium sample, the product of Pd-2wt.% has the best cycling adsorption performance, the removal ratios stabilize in 95 ~ 98%. The product of unloaded palladium and Pd-1wt.% has the similar adsorption capacity, while the single adsorption removal ratio of methylene blue in the concentration of 40 mg·L-1 is 31.96 mg·g-1 and 32.12 mg·g-1 respectively. |
PDF Full Text Request