Preparation And Modification Of Titanium-based Lithium Ion Sieves

The development of modern lithium resources has a history of more than one hundred years.From the initial extraction of lithium from ore,it has been discovered that the content of lithium in salt lake brine is not low,accounting for about 70%to 80%of the global lithium resources,and has gradually replaced the extraction of lithium from ore.Instead,extract lithium from salt lake brine.There are many methods for extracting lithium from salt lake brines.Among them,the ion-sieve adsorption method is a relatively green and promising method for extracting lithium.However,due to the low lithium content in salt lake brines in my country,the element ratio of magnesium to lithium is high.Most of the lithium ion sieves are not high in adsorption rate and stability,so it is necessary to modify the lithium ion sieves to improve their performance.This paper mainly studies the preparation process of titanium-based lithium ion sieve（layered structure）to improve the performance and stability of adsorption and elution.The specific research contents are as follows:1.Use anatase titanium dioxide as the titanium source,lithium carbonate as the lithium source,and anhydrous ethanol as the dispersion medium.After drying,use a muffle furnace to obtain a lithium ion sieve precursor（Li₂TiO₃）using a high-temperature solid phase method.The obtained precursor is verified by a series of characterization tools such as XRD and SEM to verify the ratio of each element,and the comparison and exploration of the three performance factors of lithium extraction rate,titanium dissolution rate and lithium adsorption capacity are finally obtained.The optimal conditions for the synthesis and preparation of lithium ion sieve adsorbent precursor lithium metatitanate（Li₂TiO₃）are as follows:the molar ratio of lithium to titanium is 2.1,the calcination temperature is850℃,and the calcination time is 10 h.2.Lithium ion sieve adsorbent（H₂TiO₃）is prepared by eluting the precursor（Li₂TiO₃）using hydrochloric acid as the eluent.Under the same preparation conditions,explore the effects of different pickling temperatures,different hydrochloric acid concentrations and different pickling times on the performance of the adsorbent.The best pickling conditions are finally obtained:the pickling temperature is set to 65℃,the hydrochloric acid concentration is set to 0.5 mol·L^-1,the pickling time is set to 24 h,and the solid-to-liquid ratio is 1:100.When the lithium ion sieve adsorbent is prepared under this condition,the extraction rate of lithium can reach 86.15%,and the dissolution rate of titanium is 0.23%.3.Add lithium nitrate to the raw materials as a lithium source,weigh a certain amount of raw materials into a beaker,add absolute ethanol as a dispersant,mix well and dry to obtain a mixture,and then put the mixture into the muffle furnace The modified lithium ion sieve adsorbent precursor is obtained after high-temperature roasting in the medium.Through characterization and performance testing of the precursors before and after modification,an appropriate amount of lithium nitrate used as a lithium source can be used to improve the extraction rate of lithium and the adsorption rate of lithium.4.The preparation conditions of the lithium ion sieve adsorbent precursor and the preparation conditions of the lithium ion sieve adsorbent are fixed.This experiment focuses on exploring the adsorption performance and cycle performance of the lithium ion sieve adsorbent in LiOH and Li Cl solutions.With the increase of adsorption time and temperature,the adsorption capacity of lithium increases,which is 36.78 mg·g^-1 in LiOH solution and 30.16 mg·g^-1 in Li Cl solution at equilibrium.5.Simulate the adsorption of lithium ion sieve adsorbent in complex salt lake brine,explore the adsorption performance of lithium ion sieve adsorbent,the selectivity and separation of ions and the final cycle performance.With the increase of the adsorption time,the adsorption capacity also increases.When the adsorption time is 48h,the adsorption capacity is 20.131 mg·g^-1;with the increase of the number of cycles,the adsorption capacity gradually increases,and it increases to 29.24 mg·g^-1 after the sixth cycle.As the number of cycles increases,the dissolution loss rate of titanium gradually decreases,and the final dissolution loss rate of titanium will stabilize at about 1.3%.The lithium ion sieve adsorbent has high selectivity for lithium ions.As the number of cycles increases,the selectivity of the lithium ion sieve adsorbent to ions increases,and the adsorption of lithium is more favorable.