Study On The Preparation Of Ti-Based Lithium Ion Sieve And Its Property

Lithium and its compounds are widely used in the fields of national economy and national construction.The reserves of liquid lithium resources in our country is big while the lithium content is low.The traditional methods are not suitable for extracting lithium from salt-lake brine,it is necessary to find a new adsorbent to extract the lithium from salt-lake brine in ion exchange and adsorption method.In this paper,the preparation and adsorption properties of monoclinic lithium ion sieve were investigated.The process of elution,the adsorption properties and the application of the ion sieves in the brine were characterized,respectively.The details are as follows:?1?The precursor of lithium ion sieve was synthesized by a solid-phase reaction with Li₂CO₃ and TiO₂ as the raw materials.The effect of the roasting temperature,the roasting time and the molar ratio of Li2CO3/TiO2 on the synthesis of precursor were investigated,respectively.The structure and surface morphology of the sample were characterized by XRD?X-ray diffraction?and SEM?scanning electron microscope?.The results indicated that the optimal synthesis conditions of monoclinic crystal of Li2TiO3 were n?Li2CO3/TiO2?=1.05,heating rate 4?/min and baking at 850?for 5 h.?2?The precursor?LTO?was eluted by hydrochloric acid or sodium persulfate solution with different concentrations?0.2,0.5,0.8 and 1.0 mol/L?.The influence of different eluent on the desorption-adsorption process was investigated.The results showed that the precursor could be eluted completely with hydrochloric acid elution at room temperature for 4 h;the above mentioned products?H?-TO could reach adsorption equilibrium within 100 min in a mixed solution with isopyknic 0.1 mol/L LiCl and 0.1 mol/L LiOH;the extraction of lithium was close to equilibrium within 30 min with sodium persulfate as eluent and the product?Na?-TO could reach adsorption equilibrium within 50 min in a mixed solution with isopyknic 0.1 mol/L LiCl and 0.1 mol/L LiOH.The adsorption process followed pseudo secondary dynamics model.The kinetic parameters of ion sieve prepared by sodium persulfate were superior to that of hydrochloric acid.The morphology and crystal structure of LTO,?H?-TO?or?Na?-TO?and?Li?-TO were alike and only the crystal cell parameters changed regular along with theextraction/insertion of Li⁺.?3?The adsorption process of ion sieve prepared by 0.5 mol/L hydrochloric acid and 0.8mol/L sodium persulfate solution was studied in the simulated concentrated seawater and salt lake brine.The lithium adsorption quantity and the influence of coexisting ions in the two kinds of solution were investigated.The results showed that the ion sieve prepared by hydrochloric acid had good selectivity for Li⁺and the adsorption amount was influenced by the coexisting ions in the solution;the ion sieve prepared by sodium persulfate solution had good selectivity and the coexisting ions in the solution had little influence on the adsorption amount of the ion sieve.The distribution coefficient of Li⁺and the separation factor of K⁺,Na⁺and Mg²⁺of the ion sieve eluted by 0.8 mol/L sodium persulfate solution were greater than hydrochloric acid.Ion sieve kept maximum selectivity for Li⁺during the experiment as the number of cycle increased.