Preparation And Properties Of Titanium-oxide Based Lithium Ionic Sieves By Using Polymer Tubes As A Template

In recent years, with the growing market demand for lithium, extracting lithium from liquid lithium resources especially salt lakes has become the main direction of development of lithium industry. There are many salt lakes in China, and lithium resources are very rich in brine of salt lakes, but it is difficult to separate lithium due to its low content, wide distribution, and other accompanying alkali metals, alkaline earth metal cations etc.. Compared with other lithium-extraction methods, adsorption has obvious advantages, but the poor stability and low adsorption capacity performance of lithium ion sieves limit their further application. So it is urgent to develop cheap and efficient adsorbent materials for lithium ions. In this thesis, three kinds of titanium oxide ion sieves were prepared by using polymer nanotubes as the template, and their adsorption behaviors to lithium ions were studied. The main contents are as follows :1?The precursor of the lithium ionic sieve Li₂TiO₃@CNT was obtained by using the sol-gel method and subsequent pyrolysis carbonization.In which, tetrabutyl titanate and lithium hydroxide were used as raw materials, and polymer nanotubes were acted as the template and carbon source. Then, lithium ions of the precursor were removed by hydrochloric acid, getting the ionic sieve of TiO₂@CNT. The equilibrium adsorption capacity of TiO₂@CNT to Li⁺ was 32 mg/g in LiCl-LiOH solution, and the adsorption process was fitted very well by Langmuir isotherm equation and pseudo-second order kinetic equation. But the carbon nanotubes in the composites can adsorb many kinds of metal ions, leading to the low adsorption capacity and poor selectivity of the ionic sieve TiO₂@CNT.2?CNT in TiO₂@CNT affected obviously the adsorption capacity and selectivity of the ion sieve, so the pure Li₂TiO₃ nanotubes were prepared by the calcination at lower temperature in air.Then, the ionic sieve TiO₂ nanotubes were obtained by washing off the lithium ions in hydrochloric acid. The equilibrium adsorption capacity of ion sieve TiO₂ nanotubes to Li⁺ was 35.5 mg/g in LiCl-LiOH solution, and the adsorption process was more suitable for the Langmuir isotherm equation and pseudo-second order kinetic equation. The ionic sieve TiO₂ nanotube has excellent selectivity to Li⁺ in high ratio magnesia lithium brine by adsorption experiment for simulation of the salt lake brine in Xinjiang. Compared to the ion sieve TiO₂@CNT, the selectivity of the ion sieve TiO₂ nanotubes has been greatly improved.3?During the process of Li⁺ removal in acid, TiO₂ nanotubes easily collapse, leading to the poor stability of the tubular ion sieve. Thus, we changed the preparation conditions of the precursor, we successfully obtained the H₂TiO₃ nanoparticles by the calcination at higher temperature in air and washing in acid. The equilibrium adsorption capacity of ion sieve H₂TiO₃ nanoparticles to Li⁺ was 49.9 mg/g in LiCl-LiOH solution, and the adsorption process was more suitable for the Langmuir isotherm equation and pseudo-second order kinetic equation. The ionic sieve H₂TiO₃ nanoparticles has excellent selectivity to Li⁺ in high ratio magnesia lithium brine by adsorption experiment for simulation of the salt lake brine in Xinjiang. Compared to TiO₂@CNT and TiO₂, the adsorption capacity of the ion sieve H₂TiO₃ has been greatly improved. Moreover, it has good stability and selectivity, which has potential application in extracting lithium from sea water or salt lakes.