Methods for treating lithium-containing materials
The disclosure relates to methods for preparing lithium hydroxide. For example, such methods can comprise mixing a lithium-containing material with an acidic aqueous composition optionally comprising lithium sulfate and thereby obtaining a mixture; roasting the mixture under suitable conditions to obtain a roasted, lithium-containing material; leaching the roasted material under conditions suitable to obtain a first aqueous composition comprising lithium sulfate; submitting the first aqueous composition comprising lithium sulfate to an electromembrane process under suitable conditions for at least partial conversion of the lithium sulfate into lithium hydroxide and to obtain a second aqueous composition comprising lithium sulfate, the electromembrane process involving a hydrogen depolarized anode; optionally increasing concentration of acid in the second aqueous composition; and using the second aqueous composition comprising lithium sulfate as the acidic aqueous composition optionally comprising lithium sulfate for mixing with the lithium-containing material and to obtain the mixture.
1. A method for preparing lithium hydroxide and recovering lithium sulfate, said method comprising:
mixing a lithium-containing material with an acidic aqueous composition comprising sulfuric acid and optionally comprising lithium sulfate and thereby obtaining a mixture;
roasting said mixture to obtain a roasted, lithium-containing material;
leaching said roasted material under conditions suitable to obtain a first aqueous composition comprising lithium sulfate;
submitting said first aqueous composition comprising lithium sulfate to an electromembrane process under suitable conditions for at least partial conversion of said lithium sulfate into lithium hydroxide and to obtain a second aqueous composition comprising lithium sulfate, said electromembrane process involving a hydrogen depolarized anode;
increasing concentration of acid in said second aqueous composition by removing water from said second aqueous composition by heating said second aqueous composition so as to cause a substantially selective precipitation of lithium sulfate monohydrate and to obtain a third aqueous composition;
recovering said lithium sulfate monohydrate by separating said lithium sulfate monohydrate from said third aqueous composition; and
using said third aqueous composition comprising lithium sulfate as said acidic aqueous composition for mixing with said lithium-containing material and to obtain said mixture.
2. The method of claim 1 , wherein the acid in said acidic aqueous composition is present in a stoichiometric excess of from about 10% to about 100%, based on the amount of lithium in said lithium-containing material.
3. The method of claim 1 , wherein the acid in said acidic aqueous composition is present in a stoichiometric excess of from about 10% to about 40%, based on the amount of lithium in said lithium-containing material.
4. The method of claim 1 , wherein said mixture is roasted at a roasting temperature of from about 200° C. to about 300° C.
5. The method of claim 1 , wherein said lithium-containing material is a lithium-containing ore.
6. The method of claim 5 , wherein said lithium-containing ore comprises β-spodumene.
7. The method of claim 1 , wherein said lithium-containing material further comprises a leachable metal impurity and said first aqueous composition comprising lithium sulfate is further treated under conditions suitable to remove at least a portion of said leachable metal impurity from said first aqueous composition comprising said lithium sulfate.
8. The method of claim 1 , wherein said method further comprises reusing said lithium sulfate monohydrate with said first aqueous composition comprising lithium sulfate in said electromembrane process.
9. The method of claim 1 , wherein said second aqueous composition is heated at a temperature of about 110° C. to about 130° C.
10. The method of claim 9 , wherein said second aqueous composition is heated under reduced pressure or under vacuum.
11. The method of claim 1 , wherein an acid in said acidic aqueous composition is H 2 SO 4 .
12. The method of claim 1 , wherein said electromembrane process comprises a two-compartment monopolar or bipolar membrane electrolysis process and during said two-compartment monopolar or bipolar membrane electrolysis process LiOH current efficiency is at least substantially maintained at a value of about 65% to about 85%.
13. The method of claim 1 , wherein said partial conversion occurs at a conversion of about 30 to about 60%.
14. The method of claim 1 , wherein said partial conversion occurs at a conversion of about 45 to about 55%.
15. The method of claim 1 , wherein said electromembrane process is a two-compartment membrane electrolysis process.
16. The method of claim 15 , wherein said electromembrane process comprises generating hydrogen at a cathode thereof and recovering said hydrogen for feeding said hydrogen depolarized anode.
17. The method of claim 1 , wherein said roasted lithium-containing material is leached with water to obtain said first aqueous composition comprising said lithium sulfate.
18. The method of claim 1 , wherein said lithium sulfate monohydrate is separated from said third aqueous composition by a solid-liquid separation carried out at a temperature of about 15° C. to about 130° C.
19. The method of claim 1 , wherein during said electromembrane process, the pH of said first aqueous composition is acidic.
20. The method of claim 1 , wherein during said electromembrane process, the pH of said first aqueous composition is basic.