Preparation And Adsorption Properties Of Titanium Based Lithium Ion Sieves Modified By Lithium Nitrate

Lithium and its compounds are regarded as"important strategic resources in the21st century"and widely used in various fields of industry.In recent years,mineral lithium resources have been increasingly exhausted,and liquid lithium resources have not been effectively developed and utilized.The adsorption method has a great advantage in extracting low concentration lithium resources,among which the most promising adsorbent is titanium lithium ion sieves.In this thesis,the titanium-based lithium ion sieves has been modified for its insufficient adsorption capacity and adsorption rate.The main contents and results are organized as follows:Firstly,lithium nitrate was used as a lithium source for the synthesis of titanium lithium ion sieves,and the synthetic products were characterized.The synthesis temperature was optimized,and the adsorption performance of lithium ion sieves was tested,and the pickling and adsorption mechanism were analyzed.It was found that lithium nitrate could be calcined with anatase Ti O₂ at the optimal temperature of 500℃to form lithium metatinate,which was obtained by pickling 0.2mol·L^-1 hydrochloric acid solution at the optimal temperature of 25℃.The crystal has the shape of irregular cube.Putting it in the lithium hydroxide solution with the concentration of 2 g·L^-1 for24 h,and the adsorption amount could reach 33.65 mg·g^-1.Moreover,the adsorption amount would increase with the increase of the concentration of lithium hydroxide,and finally tend to be stable.The modified titanium lithium ion sieves were synthesized by using a mixed lithium source,and the optimum mixing ratio was determined.The crystal form,particle size and specific surface area of the synthesized products were analyzed.The adsorption effect of the modified lithium ion sieves before and after modification were tested,and the ion selectivity and stability of the modified lithium ion sieves were characterized.It is found that the modified lithium ion sieve has a smaller particle diameter of 434.5 nm and a larger specific surface area of 49.15 m²·g^-1.When the addition ratio of lithium nitrate is 0.9,the mixing effect is the best.The lithium ion sieves have good lithium ion selectivity and regeneration performance.After 5adsorption-desorption cycles,the adsorption capacity remains stable.The adsorption is fitting with the Langmuir isothermal model and the pseudo-second order kinetic equation.It is revealed that adsorption process conforms to the monomolecular and chemical adsorption,and the adsorption rate was controlled by the internal diffusion of particles.This lithium ion sieves have a high adsorption rate,which can reach adsorption equilibrium at 4 h,and its pseudo-second-order kinetic constant can reach 0.2762 g·（mg·h）^-1,which is higher than other solid reaction synthesis of lithium metatinate.The above research provides the lithium ion sieves with faster adsorption rate and better performance for the effective utilization of liquid lithium resources.