US-12623912-B2 - Lithium carbonate recovery process

US12623912B2US 12623912 B2US12623912 B2US 12623912B2US-12623912-B2

Abstract

A process for the recovery of lithium carbonate from a solution ( 1 ) containing a mixture of lithium sulfate and lithium hydroxide, the process comprising the precipitation of lithium carbonate ( 3 ) from the solution ( 1 ) containing a mixture of lithium sulfate and lithium hydroxide through the addition of carbon dioxide ( 2 ).

Inventors

Mark Daniel Urbani
Gary Donald Johnson
Nicholas John VINES

Assignees

Cornish Lithium plc

Dates

Publication Date: 20260512
Application Date: 20220401
Priority Date: 20210401

Claims (6)

1 . A process for the recovery of lithium carbonate from a solution containing a mixture of lithium sulfate and lithium hydroxide, the process comprising the steps of: a) Precipitation of lithium carbonate from a solution containing lithium sulfate and lithium hydroxide through the addition of carbon dioxide; b) Solid liquid separation and optionally washing of the precipitated lithium carbonate to recover a liquor containing lithium sulfate; c) Recycle of the liquor to a subsequent step to convert lithium sulfate to lithium hydroxide; d) Purification of the lithium carbonate by pulping in water and addition of carbon dioxide to produce lithium bicarbonate solution; e) Solid liquid separation of the lithium bicarbonate solution to remove insoluble impurities; f) Heating the lithium bicarbonate solution to strip carbon dioxide and re-precipitate lithium carbonate; and g) Solid liquid separation, drying and packing of the purified lithium carbonate product.
2 . The process of claim 1 , wherein the lithium carbonate precipitation step a) is operated at atmospheric pressure.
3 . The process of claim 1 , wherein the lithium carbonate precipitation step a) is operated in a temperature range of: a. between ambient to about 100° C.; b. greater than about 50° C.; or c. between about 50° C. to 100° C.
4 . The process of claim 1 , wherein the lithium carbonate precipitation step a) occurs over a residence time of about 2 hours.
5 . The process of claim 1 , wherein the lithium carbonate precipitation step a) achieves a precipitation extent of about 90% of the stoichiometric mass of lithium hydroxide contained in the solution containing both lithium sulfate and lithium hydroxide.
6 . The process of claim 1 , wherein the lithium carbonate precipitation step a) comprises the addition of in excess of stoichiometric carbon dioxide addition.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 371 U.S. National Phase of International Application No. PCT/AU2022/050297, filed Apr. 1, 2022, which claims priority to Australian Provisional Patent Application No. 2021900980, filed Apr. 1, 2021. The entire disclosures of the above applications are incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to a process for the recovery of lithium carbonate from solutions containing lithium sulfate and lithium hydroxide. More particularly, the process of the present invention is intended to allow the recovery and separation of lithium carbonate from solutions containing sulfate anions. The process of the present invention consists of a novel combination of operating steps, one or more of which may have been used commercially, in other combinations and for other purposes, in mineral processing and hydrometallurgical processes. BACKGROUND ART The major sources of commercially mined lithium have historically come from brine solution and hard rock spodumene containing ores. For processes that recover lithium from hard rock ores, the conventional approach is to convert alpha spodumene to beta spodumene by high temperature (>800° C.) decrepitation. The conversion enables chemical attack and subsequent extraction of lithium using sulfuric acid. Post a series of impurity removal stages, lithium, which is present in solution as soluble lithium sulfate, is subsequently recovered as lithium carbonate through the addition of sodium carbonate as a precipitation reagent. The addition of sodium carbonate produces a slurry containing lithium carbonate precipitates from solution and sodium sulfate resides largely in the liquor. After separation of lithium carbonate by solid liquid separation, sodium sulfate is recovered from solution by a double crystallisation process. Recovery of sodium sulfate is necessary for this process to provide an outlet for sodium in the process. The first stage of sodium sulfate recovery involves the crystallisation of a hydrous sodium sulfate, commonly termed Glauber's salt, and by forced cooling of the liquor. To afford acceptable recoveries of sodium sulfate, the liquor must be cooled, generally to <10° C. The resultant slurry is subjected to solid liquid separation and washing to enable the recovery of lithium in the liquor. The second stage involves the melting of Glauber's salt and crystallisation of anhydrous sodium sulfate at elevated temperature. The resultant slurry is subject to solid liquid separation, and the residue is dried and packaged. The recovery of lithium carbonate through this process is both operating and capital cost intensive. Of more significant concern is the potential oversupply of sodium sulfate as the demand for lithium chemicals increases. The inability to store sodium sulfate, which is highly water soluble, may potentially inhibit the use of sodium carbonate as a precipitation reagent for lithium carbonate. In International Patent Application PCT/AU2020/050090, a process is described in which a solution containing lithium sulfate is reacted with lime and aluminium hydroxide, in which sulfate precipitates in the form of ettringite. The resulting liquor consists of a solution containing lithium hydroxide and lithium sulfate. The conversion of separation of lithium hydroxide from lithium sulfate is conducted via direct crystallisation of lithium hydroxide monohydrate. Although the crystallisation stage is selective, sulfate is the main contaminant in the product. Several purification processes are required to produce a saleable lithium product. The purification processes require precipitation reagents and evaporative crystallisation. The recovery process of the present invention has as one object thereof to substantially overcome the problems associated with the prior art or to at least provide a useful alternative thereto. The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia or any other country or region as at the priority date of the application. Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. DISCLOSURE OF THE INVENTION In accordance with the present invention there is provided a process for the recovery of lithium carbonate from a solution containing a mixture of lithium sulfate and lithium hydroxide, the process comprising the precipitation of lithium carbonate from the solution containing a mixture of lithium sulfate and lithium hydroxide through the addition of carbon dioxide. Preferab