Preparation And Properties Of Oxysilicate Titanium Sodium-like Nanotubes

In the past few years,the investigationes on titanosilicates have been fouced on a lot.There are so many combination-mode in the form of silicate.Among them,the combination-mode that SiO4 tetrahedron and TiOn?n=5,6?polyhedron are so popular.There are three kinds of titanosilicates:microporous materials,layered materials,dense materials in term of the different connection modes of SiO₄ tetrahedron and TiOn polyhedron.Dense materials included Natisite typically have been successfully applied in the fields of catalysising,ion exchanging and separating processes.However,most researches carried on are foucsed on the synthetic methods with that few researches on the micromorphology and performance of dense materials.For this point,the micromorphology of the material is taken as the research focus,and the nanotubes material is prepared and doped to explore the structure and properties of the nanotubes material.In this thesis,TiO2-SiO2 is taken as a precursor,while CTAB?cetyltrimethyl ammonium bromide?as an assistant to prepare the Na₂TiSiO₄ nanotubes with Q⁰ structure by the mean of hydrothermal.Then,base on impregnation,by adding ammonium metavanadate to precursor to prepare TiO2-VOx-SiO2 composite oxide.After that the V-doped Na₂TiSiO₄ nanotubes with Q⁰ structure are prepared by an effective hydrothermal process.In addition,Al₂O₃ is mixed into Na₂O,TiO₂ and SiO₂ by sol-gel method to prepare Na₂O-Al₂O₃-TiO₂-SiO₂ composite oxide.XRD,SEM,TEM,BET,EDS,ICP,IR,Raman and other methods were used to characterize and test the morphology,structure and properties of the above nanotubes.The results show that the formation of Q⁰ structure of Na2Ti?V?OSiO4 nanotubes is attributed to the crimping mechanism.The nanotube parameters are:inner diameter 4.890 nm to 5.700 nm,outer diameter 7.960 nm to 9.600 nm,crystal plane spacing 0.360 nm to 0.450 nm,wall spacing 0.630 nm to 0.667 nm and 3-5walls.V-doped nanotubes have larger specific surface area and higher surface Zeta potential,and V⁴⁺substitutes for Ti⁴⁺,resulting in the existence of Si⁴⁺respectively.It lies in two chemical coordination environments,Ti-O-Si and V-O-Si.The test characterization confirmed that the Na2O-Al2O3-TiO2-SiO2 nanotubes are amorphous composite oxides,and the formation mechanism is the crimping mechanism.Na₂TiSiO₄ nanotubes,V-Na₂TiSiO₄ nanotubes and Na₂O-Al₂O₃-TiO₂-SiO₂ nanotubes were used to adsorb hydrogen and uranyl ions respectively.The maximum hydrogen adsorption capacities were 100.43 mL/g,299.35 mL/g and 299.14 mL/g,and the maximum uranium adsorption capacities were 373.84 mg/g,393.70 mg/g and 321.02 mg/g,respectively.The adsorption efficiency in the 3mg/L uranyl ion sea salt solution was more than 90%.After 5 adsorption-desorption experiments,the adsorption capacity was still above 200 mg/g.Experiments have confirmed that the mechanism of adsorption of uranyl ions by nanotubes is two mechanisms of surface electrostatic adsorption mechanism and Na⁺replacement mechanism.