Processes and systems for preparing lithium carbonate
There are provided processes comprising submitting an aqueous composition comprising lithium sulphate and/or bisulfate to an electrolysis or an electrodialysis for converting at least a portion of said sulphate into lithium hydroxide. During electrolysis or electrodialysis, the aqueous composition is at least substantially maintained at a pH having a value of about 1 to about 4; and converting said lithium hydroxide into lithium carbonate. Alternatively, lithium sulfate and/or lithium bisulfate can be submitted to a first electromembrane process that comprises a two-compartment membrane process for conversion of lithium sulfate and/or lithium bisulfate to lithium hydroxide, and obtaining a first lithium-reduced aqueous stream and a first lithium hydroxide-enriched aqueous stream; and submitting said first lithium-reduced aqueous stream to a second electromembrane process comprising a three-compartment membrane process to prepare at least a further portion of lithium hydroxide and obtaining a second lithium-reduced aqueous stream and a second lithium-hydroxide enriched aqueous stream.
1. A process for preparing lithium carbonate, said process comprising:
submitting an aqueous composition comprising lithium sulphate to an electrolysis or an electrodialysis under conditions suitable for converting at least a portion of said lithium sulphate into lithium hydroxide, wherein during said electrolysis or said electrodialysis, said aqueous composition comprising lithium sulphate is at least substantially maintained at a pH having a value of about 1 to about 4; and
converting said lithium hydroxide into lithium carbonate,
wherein converting said lithium hydroxide into lithium carbonate is carried out by:
reacting an aqueous composition comprising said lithium hydroxide with CO 2 by sparging said CO 2 into said composition, said sparging being carried out while pH is at least substantially maintained at a value of about 10 to about 12.5, thereby obtaining a slurry comprising said lithium carbonate;
inserting at least a portion of said slurry into a clarifier and obtaining a supernatant comprising lithium bicarbonate and a solid comprising said lithium carbonate;
separating said solid from said supernatant; and
heating said supernatant at a temperature of at least about 85° C. so as to at least partially convert said lithium bicarbonate into lithium carbonate.
2. The process of claim 1 , wherein said aqueous composition comprising lithium sulphate is submitted to the electrolysis.
3. The process of claim 2 , wherein during said electrolysis, said pH is at least substantially maintained at a value of about 2 to about 4.
4. The process of claim 1 , wherein said aqueous composition comprising lithium sulphate is submitted to an electrolysis and said electrolysis is carried out in a three-compartment membrane electrolysis cell by introducing said aqueous composition comprising lithium sulphate into a central compartment, an aqueous composition comprising lithium hydroxide into a cathodic compartment, and generating an aqueous composition comprising sulphuric acid in an anodic compartment.
5. The process of claim 4 , wherein during said electrolysis said aqueous composition comprising lithium hydroxide is at least substantially maintained at a concentration of about 35 to about 70 g/L.
6. The process of claim 1 , wherein during said electrolysis or electrodialysis, temperature of said aqueous composition comprising lithium sulphate is at least substantially maintained at a value of about 20 to about 80° C.
7. The process of claim 6 , wherein during said electrolysis or electrodialysis electrical current is at least substantially maintained at a density of about 400 to about 3000 A/m 2 .
8. The process of claim 7 , wherein during said sparging, said pH is at least substantially maintained at a value of about 10.5 to about 11.5.
9. The process of claim 8 , wherein said supernatant is heated at a temperature of about 90° C. to about 100° C.
10. The process of claim 9 , wherein during said process said supernatant, when being heated, is at least substantially maintained at a Li concentration of about 3 to about 5 g/L.
11. The process of claim 8 , wherein during said electrolysis or electrodialysis said aqueous composition comprising lithium hydroxide is at least substantially maintained at a concentration of about 40 to about 60 g/L.
12. The process of claim 8 , wherein said aqueous composition comprising lithium sulphate is submitted to the electrolysis.
13. The process of claim 1 , wherein during said electrolysis or electrodialysis electrical current is at least substantially maintained at a density of about 400 to about 2000 A/m 2 .
14. The process of claim 1 , wherein during said electrolysis or electrodialysis electrical current is at least substantially maintained at a density of about 400 to about 600 A/m 2 .
15. The process of claim 1 , wherein during said sparging, said pH is at least substantially maintained at a value of about 10.5 to about 12.0.
16. The process of claim 15 , wherein said supernatant is heated at a temperature of about 85° C. to about 105° C.
17. The process of claim 16 , wherein said sparging is carried out at a temperature of about 15 to about 30° C.
18. The process of claim 16 , wherein during said process said supernatant, when being heated, is at least substantially maintained at a Li concentration of about 2 to about 6 g/L.
19. The process of claim 15 , wherein during said electrolysis or electrodialysis said aqueous composition comprising lithium hydroxide is at least substantially maintained at a concentration of lithium hydroxide of about 30 to about 70 g/L.
20. The process of claim 1 , wherein during said process said supernatant, when being heated, is at least substantially maintained at a Li concentration of about 1 to about 10 g/L.