Study On The Technology Of Extracting Lithium From Brine By Superconducting Magnetic Adsorption

Lithium and its compounds have a wide range of applications.In recent years,with the continuous development of new energy industry in China,the demand for lithium is also increasing rapidly.There are abundant lithium resources in salt lake brine in China,but the development of lithium extraction industry in salt lake is limited with the problems of many associated ions,high Mg/Li and low grade of lithium.At present,adsorption method is considered as one of the potential technique-lithium extraction technologies for salt lake brine with high Mg/Li.In this work,amagnetic titanium series adsorbent and a magnetic aluminum series adsorbent are proposed to study their lithium adsorption performance.Combined with the superconducting magnetic separation technology,the lithium extraction of old brine after extracting potassium from a salt lake in Mahai Lake area,Qinghai Province is studied.Firstly,a kind of magnetic titanium adsorbent Li₂Ti O₃@Si O₂@Fe₃O₄ with high adsorption capacity,low dissolution loss and strong magnetism was prepared by high temperature solid-state method.It was characterized by XRD,SEM and VSM.The results showed that n(Ti/Li)=2 and n(Ti/Fe)=7,The magnetic adsorbent with good performance can be prepared by calcining at 800?for 8 hours.The particle size distribution of the adsorbent is between 5-15?m and the specific saturation magnetization is 17.68 emu/g.The solid-liquid separation can be realized under the action of permanent magnet block.The adsorption process of magnetic titanium adsorbent in lithium solution conforms to the quasi second-order dynamic model.Freundlich isothermal adsorption model was used to fit the theoretical saturated adsorption capacity of 22.53 mg/g.With 0.25 M hydrochloric acid and desorption at 50?for 4h,the desorption rate of lithium ion in the magnetic titanium adsorbent can reach 96%,titanium loss 0.14%,iron loss 0.09%,and the regeneration ability of the adsorbent is strong.When the solid-liquid ratio of the adsorbent is 1:40 and the adsorbent is adsorbed for 4 hours,it can adsorb 98.2%of lithium in brine.The selectivity of lithium in brine is=2126.6,which is much greater than that of other ions in brine.After 20 cycles of brine adsorption and acid desorption,the loss of magnetic titanium adsorbent is 7.2%,and97.08%of lithium in brine can still be removed.When the magnetic induction intensity of the superconducting magnetic separator is 2.0T,the separation chamber adopts the steel mesh medium,and the cross-section velocity of the medium is 7 cm/s,the collection rate of the magnetic titanium adsorbent is 99.5%.Secondly,magnetic aluminum adsorbent(MASA)is mainly 35-80?m,the average particle size is 50.3?m,and the specific saturation magnetization is 10.78 emu/g.When the magnetic induction intensity of the superconducting magnetic separator is 2.0T,the separation chamber is made of steel mesh medium,and the cross-section velocity of the medium is 10 cm/s,the collection rate of the magnetic titanium adsorbent is 99.5%.When the solid-liquid ratio of the adsorbent is 1:10,and the adsorption time is 4 hours,the lithium removal rate of masa can reach 99.6%,and the lithium selectivity of Masa is=206.6,which is better than other ions in brine.After washing salt with 500 ml fresh water and desorbing with 1.5L tap water for 15 min,Li⁺:0.285 g/L and Mg²⁺:0.570 g/L in the desorbing solution were concentrated 1.75 times as much as that in the original brine,the ratio of Mg/Li was reduced from 664:1 to 2:1,the recovery of Li was 81%,and the recovery of Li in the whole process was 81%.After 100 cycles of adsorption and desorption of magnetic adsorbent in the superconducting magnetic separation system,the loss of adsorbent is 8.9%,but without significant loss of MASA activity,the lithium ion in 90.6%brine can be adsorbed,and the lithium rich desorption solution with stable quality can be obtained.