Method for recovering lithium from lithium-containing solution

1 . A method for recovering lithium from a lithium-containing solution, comprising:

(1) precipitating lithium from the lithium-containing solution by a) or b):

a) regulating the lithium-containing solution by adjusting a pH value of the lithium-containing solution to 5-6, mixing the regulated lithium-containing solution with a meta-aluminate solution, and standing for aging, to obtain a precipitation solution containing a first precipitate of Li(OH)·2Al(OH) 3 ·nH 2 O, wherein n=1-3;

during the adjusting of the pH value of the lithium-containing solution, collecting carbon dioxide produced by the lithium-containing solution and injecting the collected carbon dioxide produced by the lithium-containing solution into an alkaline solution to obtain a carbonate; and

regulating the precipitation solution by adjusting a pH value of the precipitation solution to 6-7, and performing filtering and washing on the regulated precipitation solution, to obtain a precipitate of Li a X·2Al(OH) 3 ·nH 2 O and a first filtrate, wherein X represents an anion of an acid solution used in the adjusting of the pH value of the precipitation solution, and a=1 or 2; or

b) mixing the lithium-containing solution with a meta-aluminate solution to obtain a first mixture, regulating the first mixture by adjusting a pH value of the first mixture to 5-7, standing for aging, and performing filtering and precipitating on the regulated first mixture after the aging, to obtain a precipitate of Li a X·2Al(OH) 3 ·nH 2 O and a first filtrate, wherein X represents an anion of an acid solution used in the adjusting of the pH value of the first mixture, n=1-3, and a=1 or 2; and

during the adjusting of the pH value of the first mixture, collecting carbon dioxide produced by the lithium-containing solution and injecting the collected carbon dioxide produced by the lithium-containing solution into an alkaline solution to obtain a carbonate;

(2) desorption of lithium: mixing the precipitate of Li a X·2Al(OH) 3 ·nH 2 O with water in a mass ratio of 1:1 to 1:50 to obtain a second mixture and stirring the second mixture at 20-60° C. for 1-24 hours, and filtering the second mixture to obtain a lithium adsorbent of (1−m)Li a X·2Al(OH) 3 ·nH 2 O and a first Li a X-containing filtrate, wherein m=0.1-0.9;

(3) precipitation of lithium: evaporating and concentrating the first Li a X-containing filtrate to obtain a concentrated first Li a X-containing filtrate, adding a carbonate into the concentrated first Li a X-containing filtrate to obtain a third mixture, and stirring the third mixture, and performing filtering and washing on the third mixture, to obtain a precipitate of Li 2 CO 3 , wherein a molar ratio of lithium in the first Li a X-containing filtrate to a carbonate ion in the carbonate is 1.05:2 to 1.3:2; and

(4) adding the lithium adsorbent to the first filtrate, and performing filtering and washing on the first filtrate to obtain a second precipitate of Li a X·2Al(OH) 3 ·nH 2 O ; and

performing the desorption of lithium on the second precipitate to obtain a lithium-desorbed filtrate, and precipitating lithium from the lithium-desorbed filtrate.

2 . The method according to claim 1 ,

wherein the adding the lithium adsorbent to the first filtrate comprises stirring the first filtrate with the lithium adsorbent at 20-60° C. such that a lithium ion is adsorbed in the first filtrate.

3 . The method according to claim 1 , wherein the acid solution comprises one of sulfuric acid, hydrochloric acid, nitric acid, or acetic acid.

4 . The method according to claim 1 , wherein a D50 particle size of the lithium adsorbent is 20-100 μm.

5 . The method according to claim 1 , wherein the first Li a X-containing filtrate is evaporated and concentrated to obtain a concentration of lithium of 15-25 g/L.

6 . The method according to claim 1 , wherein in step (3), the carbonate is added into the concentrated first Li a X-containing filtrate at 50-90° C.

7 . The method according to claim 1 , wherein the alkaline solution comprises NaOH or KOH, and the carbonate comprises Na 2 CO 3 or K 2 CO 3 .

8 . The method according to claim 1 , wherein in step (1) a) or step (1) b), the lithium-containing solution is mixed with the meta-aluminate solution in a molar ratio of Li:Al of 1.05:2 to 1.3:2.

9 . The method according to claim 1 , wherein in step (3), a second filtrate is obtained when obtaining the precipitate of Li 2 CO 3 , and the method further comprises: adding the second filtrate to the lithium-containing solution.

10 . The method according to claim 1 , wherein the filtering is performed under a negative pressure of 0.04-0.07 MPa, and a mesh number of a filter medium for the filtering is 300-5000.