Preparation of lithium carbonate from lithium chloride containing brines

1. A method of preparing lithium carbonate from a lithium chloride-rich stream, the method comprising the steps of:

supplying a geothermal brine solution containing lithium chloride and silica to a silica removal step to produce a silica-lean lithium chloride-containing solution, wherein the silica removal step is operable to remove at least a portion of silica present in the geothermal brine solution;

processing the silica-lean lithium chloride-containing solution through a lithium chloride capture step to obtain a lithium chloride-containing feed solution, wherein the lithium-chloride containing feed solution further comprises divalent ions;

contacting the lithium chloride-containing feed solution with an ion removal medium to remove at least a portion of the divalent ions present in the lithium chloride-containing feed solution and produce a purified lithium chloride-rich stream having a reduced concentration of the divalent ions relative to the lithium chloride-containing feed solution;

processing the purified lithium chloride-rich stream in an electrochemical cell to produce a lithium hydroxide-rich solution;

contacting the lithium hydroxide-rich solution with carbon dioxide to produce a product stream comprising lithium carbonate; and

separating the product stream to produce a lithium carbonate stream and a recycle stream, wherein the recycle stream is supplied to the electrochemical cell;

wherein the recycle stream is acidified to a pH less than 4 prior to supplying the recycle stream to the electrochemical cell.

2. The method of claim 1 , wherein the ion removal medium is a chelating ion exchange resin.

3. The method of claim 1 , wherein the lithium chloride capture step comprises contacting the silica-lean lithium chloride-containing solution with an intercalated lithium adsorbent.

4. A method of preparing lithium hydroxide from a lithium chloride-rich stream, the method comprising the steps of:

supplying a geothermal brine solution containing lithium chloride and silica to a silica removal step to produce a silica-lean lithium chloride-containing solution, wherein the silica removal step is operable to remove at least a portion of silica present in the geothermal brine solution;

processing the silica-lean lithium chloride-containing solution through a lithium chloride capture step to obtain a lithium chloride-containing feed solution, wherein the lithium-chloride containing feed solution further comprises divalent ions;

contacting the lithium chloride-containing feed solution with an ion removal medium to remove at least a portion of the divalent ions present in the lithium chloride containing feed solution to produce a purified lithium chloride-rich stream having a reduced concentration of the divalent ions relative to the lithium chloride-containing feed solution; and

processing the purified lithium chloride-rich stream in an electrochemical cell to generate lithium hydroxide;

wherein the silica removal step comprises oxidizing the geothermal brine solution using an oxidizing agent, and, after oxidation, adjusting the pH to a range from 5 to 6 to form precipitated compounds, wherein the precipitated compounds comprise silica;

wherein the purified lithium chloride-rich stream is acidified to a pH less than 4 prior to processing the purified lithium chloride-rich stream in the electrochemical cell.

5. The method of claim 4 , wherein the ion removal medium is an ion exchange resin.

6. The method of claim 5 , wherein the ion exchange resin is a chelating resin.

7. The method of claim 4 , wherein the lithium chloride capture step comprises contacting the silica-lean lithium chloride containing solution with an intercalated lithium adsorbent.

8. The method of claim 4 , wherein the electrochemical cell comprises an anode, a cathode, and a semi-permeable membrane separating an anode chamber and a cathode chamber.

9. The method of claim 8 , wherein the semi-permeable membrane is a semi-permeable cation selective membrane.

10. The method of claim 4 , wherein the electrochemical cell comprises a current density between 500 and 10,000 A/m 2 .

11. The method of claim 4 , wherein the step of processing the purified lithium chloride-rich stream in the electrochemical cell comprises operating the electrochemical cell at a temperature between 60° C. and 100° C.

12. The method of claim 4 , wherein the silica removal step comprises contacting the geothermal brine solution with activated alumina or aluminum chloride.

13. The method of claim 4 , further comprising concentrating the purified lithium chloride-rich stream prior to the step of processing the purified lithium-chloride rich stream in the electrochemical cell.