# US 12,000,013 B2 · Caustic conversion process > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,000,013 B2 - Document ID: US12000013B2 - Status: Granted - Kind: B2 - Application number: 17/262,449 - Filed: 2019-07-24 - Published: 2021-06-17 - Granted: 2024-06-04 - Earliest claimed: 2018-07-24 - Assignees: Australian Nuclear Science and Technology Organisation; Lithium Australia Limited - Applicants: Lithium Australia Nl; Australian Nuclear Science and Technology Organisation - Inventors: Andrew Napier; Christopher Griffith - Web page: https://patentgrep.com/patent/US12000013B2 ## CPC - C22B 26/12: Obtaining lithium - C22B 1/00: Preliminary treatment of ores or scrap - C22B 3/08: Sulfuric acid {, other sulfurated acids or salts thereof} - C22B 3/10: Hydrochloric acid {, other halogenated acids or salts thereof} - C22B 3/12: in inorganic alkaline solutions - C22B 3/22: by physical processes, e.g. by filtration, by magnetic means {, or by thermal decomposition} (treatment or purification of solutions by liquid-liquid extraction C22B3/26) - C22B 3/44: by chemical processes (treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42) - Y02P 10/20: Recycling - C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract The disclosure relates to processes for extracting lithium from an uncalcined lithium-bearing silicate and recovering a lithium salt therefrom. A slurry of the uncalcined lithium-bearing silicate and a caustic solution is heated in an autoclave to provide a Li-rich sodalite phase. The Li-rich sodalite phase is leached with a dilute acid to produce a lithium-rich pregnant liquor. Various subsequent processes to treat the lithium-rich pregnant liquor to recover a lithium salt, such as lithium phosphate, lithium carbonate, lithium sulphate or lithium hydroxide, are described. ## Claims ### Claim 1 A process for extracting lithium from an uncalcined lithium-bearing silicate comprising: a) heating a slurry of the uncalcined lithium-bearing silicate and a caustic solution in an autoclave to produce a Li-rich sodalite phase; and b) leaching the Li-rich sodalite phase with a dilute acid having a pH of 2-6 to produce a lithium-rich pregnant liquor. ### Claim 2 (depends on 1) The process according to claim 1, further comprising treating the lithium-rich pregnant liquor to recover a lithium salt from the lithium-rich pregnant liquor. ### Claim 3 (depends on 1) The process according to claim 1, wherein the slurry has a solids content ≤25 wt %. ### Claim 4 (depends on 1) The process according to claim 1, wherein the caustic solution comprises from 30%-60% w/w NaOH or 30-60 wt % KOH. ### Claim 5 (depends on 1) The process according to claim 1, wherein the slurry is heated to a temperature from 200° C. to 350° C. in the autoclave and for a period from 1 to 6 hours. ### Claim 6 (depends on 1) The process according to claim 1, wherein after heating said slurry to produce a Li-rich sodalite phase, the process further comprises diluting said slurry with water to 10-30% w/w NaOH or 10-30% w/w KOH. ### Claim 7 (depends on 6) The process according to claim 6, wherein the Li-rich sodalite phase is separated from the diluted slurry and the separated Li-rich sodalite phase is washed one or more times to remove residual diluted caustic solution. ### Claim 8 (depends on 7) The process according to claim 7, wherein the separated dilute caustic solution is treated with lime to produce insoluble calcium aluminates and calcium silicates. ### Claim 9 (depends on 1) The process according to claim 1, wherein leaching the Li-rich sodalite phase with dilute acid is performed at a temperature from 20-80° C. and for a period from 30 minutes to 24 hours. ### Claim 10 (depends on 1) The process according to claim 1, wherein the dilute acid comprises HCl or H2SO4. ### Claim 11 (depends on 1) The process according to claim 1, wherein a slurry of the Li-rich sodalite phase and dilute acid has a solids content ≤50 wt %. ### Claim 12 (depends on 1) The process according to claim 1, wherein the lithium-rich pregnant liquor comprises from 5-25 g/L Li. ### Claim 13 (depends on 2) The process according to claim 2, wherein the lithium salt comprises lithium carbonate, lithium hydroxide, lithium phosphate or lithium sulfate. ### Claim 14 (depends on 2) The process according to claim 2, wherein prior to treating the lithium-rich pregnant liquor to recover the lithium salt, the process further comprises removing impurities from the lithium-rich pregnant liquor. ### Claim 15 (depends on 14) The process according to claim 14, wherein the removing impurities from the lithium-rich pregnant liquor comprises increasing the pH of the lithium-rich pregnant liquor to pH >10 by adding a base thereto and separating precipitates containing the impurities by filtration. ### Claim 16 (depends on 15) The process according to claim 15, wherein after removing impurities from the lithium-rich pregnant liquor, the process further comprises softening said liquor by decreasing the calcium content thereof to less than 25 ppm. ### Claim 17 (depends on 16) The process according to claim 16, wherein the softening comprises adding alkali metal carbonate or alkali metal phosphate to the lithium-bearing solution to produce calcium precipitates comprising calcium carbonate or apatite and separating said calcium precipitates. ### Claim 18 (depends on 13) The process according to claim 13, wherein treating the lithium-rich pregnant liquor to recover lithium carbonate, lithium phosphate or lithium sulfate comprises: contacting the lithium-rich pregnant liquor with carbon dioxide or adding a carbonate salt to the lithium-rich pregnant liquor to produce lithium carbonate solids and a barren lithium solution; or adding a phosphate salt to the lithium-rich pregnant liquor to produce lithium phosphate solids and a barren lithium solution; or treating the lithium-rich pregnant liquor to recover lithium sulfate comprises evaporating the lithium-rich pregnant liquor to produce lithium sulfate solids and a barren lithium solution. ### Claim 19 (depends on 18) The process according to claim 18, wherein the barren lithium solution is separated and recycled.