Preparation And Adsorption Properties Of Lithium Titanium Ion Sieve Composites

At present,lithium and its salts are widely used in medical treatment,ceramics,batteries and other aspects,especially the rapid development of the new energy industry,resulting in increasing consumption of lithium,and then the global demand for lithium resources is increasing,but because of the global ore lithium technology is difficult,It has been unable to meet the needs.In comparison,the adsorption method is a promising technology for lithium extraction.The lithium extraction technology mainly includes manganese ion screen and titanium,ion screen.Due to the existence of manganese ion screen adsorbent is not stable enough and the dissolution loss rate is large,while titanium ion screen adsorbent is concerned because of low dissolution loss rate and high selectivity.Therefore,this paper mainly studies the titanium-based ion sieve adsorbents,which are doped with rare earth elements,added with soft templating agents and coated with pretreated carbon nanotubes to improve the adsorption performance of titanium-based ion sieve adsorbents.The ion sieve precursor doped with rare earth element La³⁺ was prepared by sol-gel method,and the final doped ion sieve Li₄Ti_5-xLa_xO₁₂（X=0,0.01,0.02,0.03）was obtained by pickling.The concentration,adsorption kinetics,selectivity and cyclic stability of Li₄Ti_5-xLa_xO₁₂ were analyzed.The results show that:after the acid pickling lithium removal experiment,the subsequent acid pickling lithium removal experiment should be earried out in 0.1 mol/L hydrochloric.acid solution to maximize the leaching rate of Li⁺ and the loss rate of Ti⁴⁺ should not be higher than 1%.When doping amount X=0.01 and calcination temperature is 800℃,the crystal structure and morphology of the doped ion sieve are relatively good.The adsorption kinetics curve of the doped ion sieve is fitted,and the fitting results show that the doped ion sieve is more in line with thepseudo-second-order kinetics.Finally,in a single solution the selectivity of the doped ion sieve to lithium ions is much higher than that of other of the ion sieve is ideal.Lithium-titanium ion sieves with soft templating agents were prepared by the templating method with the addition of soft templating agents（CTAB）..TG-DTG,XRD,SEM,contact Angle and selectivity were discussed.The results show that the thermogravimetric curve analysis shows that CTAB decomposes in the form of gas during the roasting process,which does not affect the performance of the lithium titanium ion sieve;The lithium-titanium ion sieve precursor added with 0.1 g CTAB still has a spinel structure,a more complete crystal form,and a lamellar surface morphology;the contact Angle experiment shows that the contact angle of the lithium titanium ion sieve is less than 90°,which has good hydrophilicity,indicating that the adsorbent and adsorption solution can fully contact,which is conducive to the adsorption of the adsorbent.In the mixed solution,from the perspective of the adsorption partition coefficient,the preferential adsorption order of heavy metal ions is Li⁺>>Na⁺>K⁺>Ca²⁺>Mg²⁺;except for Li⁺,the separation coefficients of other ions（αLiMe）are all greater than 1,indicating that the lithium titanium ion sieve has high selectivity to Li⁺.Using the coating method,using the pretreated carbon nanotubes and butyl titanate,lithium acetate and chelating agent glacial acetic acid as raw materials,the composite ion sieve H₄Ti₅O₁₂@CNT was prepared by sol-gel.SEM,TEM,FTIR and XRD were studied.The results show that:After characterization analysis,compared with untreated carbon nanotubes,the pretreated carbon nanotubes introduced a large number of functional groups-COOH and-OH,which effectively improved their dispersion in aqueous solution or ethanol,facilitating the subsequent adsorption experiments of composite materials.After roasting and pickling at different temperatures,the samples roasted at 700℃ are more suitable.The structure of composite ion sieve is relatively stable,and the acid washing treatment cannot affect its structural integrity;The saturated adsorption capacity of lithium ion adsorbed by the composite ion screen for the first time was as high as 32.32 mg/g.After the adsorption cycle experiment,it still remained at 30.68 mg/g,which is only reduced by 5.1%.