WO2024064996A1

WO2024064996A1 - Recovery of lithium sulfate

Info

Publication number: WO2024064996A1
Application number: PCT/AU2023/050910
Authority: WO
Inventors: Neil Michael Edwin Ireland; Mark Daniel Urbani
Original assignee: Renewable Metals Pty Ltd
Current assignee: Renewable Metals Pty Ltd
Priority date: 2022-09-27
Filing date: 2023-09-21
Publication date: 2024-04-04
Anticipated expiration: 2025-03-27
Also published as: TW202419401A

Abstract

The invention relates to a method for the recovery of lithium sulfate from an aqueous solution comprising lithium sulfate and ammonium sulfate, the method comprising: concentrating the aqueous solution and forming a lithium ammonium sulfate (LiNH₄SO₂) precipitate in the aqueous solution; separating the lithium ammonium sulfate precipitate from the solution; and decomposing the lithium ammonium sulfate precipitate to form solid lithium sulfate.

Description

RECOVERY OF LITHIUM SULFATE

Field

[0001] The present invention relates to a method for the recovery of lithium sulfate, a nonlimiting disclosure of which includes the recovery of lithium sulfate from solutions generated from the treatment of lithium bearing ores and concentrates including electronic waste, such as Li-ion batteries.

Background

[0002] The volume of rechargeable Li-ion batteries used worldwide has been growing rapidly in recent years and is set for further expansion with the emerging markets of electric vehicles and mass electric power storage. As the demand for Li-ion batteries increases, so does the demand for the metal/metal oxide components that are used in these batteries. The rapid increase in demand for some of these metals, such as cobalt, has put pressure on the sustainable supply of such resources. This has caused the cost of such metals to rapidly increase. There is a need to recycle the components present in batteries.

[0003] Most developments in battery recycling processing involve dissolution of the metals and subsequent separation and concentration of the metals by way of solvent extraction. Typically, pH control is required in the solvent extraction stage. For those processes utilising sulfuric acid or ammonia/ammonium sulfate in the leach and ammonia as pH control in the solvent extraction circuits, the liquor will contain ammonium sulfate. When extracting metals with conventional solvent extraction reagents, lithium is typically the least selective. Therefore, after recovery of valuable metals nickel, cobalt, manganese and copper, the resultant liquor, that is relatively free of these valuable metals, contains lithium sulfate and ammonium sulfate.

[0004] To date, there is no commercially practiced process for the selective recovery of lithium sulfate from a solution containing lithium sulfate and ammonium sulfate.

[0005] International Patent Application PCT/IL2012/050435 (WO 2013/065050 Al) discloses a process for the selective solvent extraction of lithium from solutions containing other monovalent cations using an extracting organic solution comprising at least one organic diluent, at least one phosphine oxide and at least one proton donating agent under alkaline conditions. [0006] The process of PCT/IL2012/050435 requires the addition of an alkali to increase the pH during extraction, then the final filtrate requires acidification to recover water soluble organic reagents. When operating using ammonia, since it is a weak base, the ammonia consumption associated with operating with high pH is significant. Since there is a requirement to acidify the raffinate, which contains a high concentration of free ammonia, the acid consumption required to acidify the raffinate is also significant. The high ammonia and sulfuric acid consumption produces a significant concentration of ammonium sulfate, which must be removed from the process which then requires crystallisation, drying and bagging.

[0007] It is an object of the invention to address at least one shortcoming of the prior art and/or provide a useful alternative.

[0008] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

Summary of Invention

[0009] In a first aspect of the invention, there is provided a method for the recovery of lithium sulfate from an aqueous solution comprising lithium sulfate and ammonium sulfate, the method comprising: concentrating the aqueous solution and forming a lithium ammonium sulfate (LiNHiSCh) precipitate in the aqueous solution; separating the lithium ammonium sulfate precipitate from the solution; and decomposing the lithium ammonium sulfate precipitate to form solid lithium sulfate.

[0010] In an embodiment, the step of decomposing the lithium ammonium sulfate precipitate forms an off-gas comprising ammonia and one or more sulfur oxides.

[0011] In one form of the above embodiment, the method further comprises recovering ammonia and one or more sulfur oxides in the off-gas. Preferably, the step of recovering the ammonia and one or more sulfur oxides in the off-gas comprises: contacting the off-gas with an aqueous adsorbent solution in a wet scrubber to adsorb the ammonia and one or more sulfur oxides to form an aqueous liquor comprising ammonia and one or more sulfur oxides. Preferably, the aqueous adsorbent solution comprises an oxidant e.g., to oxidise the one or more sulfur oxides to sulfate. In a non-limiting disclosure, the oxidant is selected from the group consisting of: air, oxygen, hydrogen peroxide, and combinations thereof.

[0012] In one form of the above embodiment, the method further comprises reacting ammonia and one or more sulfur oxides in the aqueous liquor to form ammonium sulfate. Preferably, the step of reacting ammonia and one or more sulfur oxides to form ammonium sulfate comprises: subjecting the aqueous liquor to an evaporative crystallisation process to precipitate the ammonium sulfate. More preferably, the method further comprises separating the precipitate of ammonium sulfate from the aqueous liquor. It is preferred that the evaporative crystallisation process is carried out at elevated temperature (e.g. greater than ambient temperature, such as greater than 30 °C or greater than 40 °C or greater than 50 °C) and at atmospheric pressure or less.

[0013] In an embodiment, the decomposing step comprises heating the lithium ammonium sulfate to a temperature in the range of from about 250 °C to 1300 °C. Preferably, the temperature is up to about 860 °C. The decomposing step is preferably carried out in a kiln.

[0014] In an embodiment, the step of concentrating the aqueous solution comprises: subjecting the aqueous solution to an evaporative crystallisation process. It is preferred that the evaporative crystallisation process is carried out at elevated temperature (e.g. greater than ambient temperature, such as greater than 30 °C or greater than 40 °C or greater than 50 °C) and at atmospheric pressure or less.

[0015] In an embodiment, the step of separating the lithium ammonium sulfate precipitate from the solution comprises: subjecting the aqueous solution containing the lithium ammonium sulfate precipitate to a solid-liquid separation process to provide a solid containing stream comprising the lithium ammonium sulfate precipitate and a liquid stream. It is preferred that the solid-liquid separation step is carried out in a centrifuge.

[0016] In one form of the above embodiment, the liquid stream is substantially saturated with Li⁺ and/or NH4⁺. By substantially saturated it is meant that the liquid stream contains Li⁺ and/or NH₄ ⁺ at the saturation concentration or within 1% of the saturation concentration. [0017] In one form of the above embodiment, the method further comprises recycling the liquid stream as a component of the aqueous solution at or prior to the step of concentrating the aqueous solution.

[0018] In an embodiment, prior to the concentrating step, the method further comprises: obtaining the aqueous solution from a process comprises leaching lithium containing electronic waste.

[0019] In an embodiment, the aqueous solution is substantially free of Co, Cu, Ni, and Mn. By substantially free it is meant that the concentration of each of Co, Cu, Ni, and Mn is 100 mg/L or less. Preferably, the concentration is 80 mg/L or less. Even more preferably, the concentration is 60 mg/L or less. Most preferably, the aqueous solution contains no Co, Cu, Ni, and Mn or the concentration of Co, Cu, Ni, and Mn is below a detectable level.

[0020] In a second aspect of the invention there is provided a method for recovering lithium in the form of lithium sulfate from electronic waste comprising one or more lithium compounds, the method comprising: leaching the electronic waste with a leach solution to provide a leachate comprising Li ions; wherein the leachate comprises ammonium ions and sulfate ions and/or the leachate is subjected to one or more treatment steps which introduce a source of or ammonium ions and/or sulfate ions into the leachate; subjecting the leachate to the method according to the first aspect of the invention and/or embodiments and/or forms thereof, wherein the leachate is fed to the concentrating step as the aqueous solution.

[0021] In a third aspect of the invention, there is provided a lithium sulfate product produced according to the method of the first or second aspects of the invention and/or embodiments and/or forms thereof.

[0022] In a fourth aspect of the invention, there is provided a method for the recovery of lithium sulfate from a feed stream, the feed stream being a solution containing lithium sulfate and ammonium sulfate, the method comprising:

(i) passing the feed stream to an evaporative crystallisation stage to concentrate the solution such that the solution is saturated and a double salt of ammonium sulfate and lithium sulfate is crystallised;

(ii) separating the product of step (i) to provide a liquor and a solid residue;

(iii) returning the liquor, with any contained lithium sulfate and ammonium sulfate, to a precedent process (such as the evaporative crystallisation stage) to recover further lithium sulfate and ammonium sulfate or use ammonium sulfate as a reagent; and

(iv) passing the solid phase of step (iii) to a step in which energy is imparted to the solids, wherein the solids are heated to decompose the ammonium sulfate whereby ammonia and sulfur oxides report to a gas phase and lithium sulfate report to a solid phase.

[0023] In an embodiment, the method further comprises: absorption of the ammonia and sulfur oxide gasses of step (iv) in a liquor; and returning the liquor of step (v) to a precedent process for re-use or subjecting the liquor to oxidation then evaporative crystallisation to recover ammonium sulfate.

[0024] In an embodiment, the evaporative crystallisation stage is conducted at elevated temperature and/or under vacuum up to atmospheric pressure.

[0025] In an embodiment, the separation of solids and liquors is conducted using a centrifuge.

[0026] In an embodiment, the step in which solids are heated is conducted in a kiln. Preferably the heating stage is conducted in the range 250 °C to 1300 °C.

[0027] In an embodiment, off-gas recovered from the kiln is absorbed in water. The resulting liquor contains ammonium and sulfur species.

[0028] In an embodiment, the resulting liquor is directed to a battery recycling process.

[0029] In an embodiment, the resulting liquor is oxidised with an oxidant, including, but not limiting to air, oxygen, hydrogen peroxide etc. An oxidant may be required e.g., to oxidise various sulfur species (e.g., SOx) to sulfate. The oxidised liquor is subjected to evaporative crystallisation to recover ammonium sulfate.

[0030] In a fifth aspect of the invention, there is provided a method for the recovery of lithium sulfate from a feed stream, the feed stream being a solution containing lithium sulfate and ammonium sulfate, the method comprising: (i) passing the feed stream to an evaporative crystallisation stage to concentrate the solution such that the solution is saturated and a double salt of ammonium sulfate and lithium sulfate is crystallised;

(iii) returning the liquor, that may contain lithium sulfate and ammonium sulfate, to a precedent process to recover further lithium and ammonium sulfate or use ammonium sulfate as a reagent;

(iv) passing the solid phase of step (ii) to a device that imparts energy to the solids, such as a kiln, wherein the solids are heated to decompose the ammonium sulfate in which ammonia and sulfur oxides reside in the gas phase and lithium sulfate remains in the solid phase;

(v) absorption of the ammonia and sulfur oxide gasses in a liquor; and

(vi) returning the liquor from (v) to a precedent process for re-use or subjecting the liquor to oxidation then evaporative crystallisation to recover ammonium sulfate.

[0031] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief Description of Drawings

[0032] Figure 1 is a flow sheet depicting a method for the recovery of lithium sulfate in accordance with the present invention.

Description of Embodiments

[0033] The invention broadly relates to a method of recovering lithium sulfate from a solution that comprises lithium ions, ammonium ions, and sulfate ions, such as a solution containing lithium sulfate and ammonium sulfate. The inventors have found that such a solution can be concentrated beyond the saturation point of a lithium ammonium double salt (LiNFUSCU) to precipitate this lithium ammonium double salt. This precipitate can then be recovered from solution by solid-liquid separation processes known to those skilled in the art, and then thermally decomposed to form a solid lithium sulfate product and to produce ammonia and sulfur oxide off-gases. [0034] In preferred forms of the invention, the ammonia and sulfur oxide off-gases may be recovered and reacted together to form ammonium sulfate. The ammonium sulfate can likewise be recovered for use or as a vendible product.

[0035] The method of the invention is particularly useful for the recovery of lithium sulfate from spent Li-ion batteries, preferably as high purity sulfate. The process is particularly applicable to processes that include the use of ammonia, for example (i) during leach of the Li- ion battery waste to form a lithium containing liquor, or (ii) as pH control during the process, for example during the leach process or in various metal recovery or solvent extraction stages of the process, such that the lithium containing liquor also contains ammonium sulfate.

[0036] Figure 1 is a process flow diagram in accordance with an embodiment of the invention. In Figure 1 there is shown a method for the recovery of lithium sulfate from a feed stream containing lithium sulfate and ammonium sulfate. The method of Figure 1 illustrates the recovery of a lithium sulfate product 6 and an ammonium sulfate product 15. Whilst Figure 1 illustrates a process for recovery of both lithium sulfate and ammonium sulfate, the skilled person appreciates that the invention can be carried out without recovery of ammonium sulfate.

[0037] In the embodiment illustrated in Figure 1 a feed stream 1 is subjected to an evaporative crystallisation step 100, for example using a forced circulation crystalliser, to crystallise lithium ammonium sulfate double salt and produce a condensate 2. A resulting slurry 3 is subjected to a solid liquid separation step, for example in centrifuge 110. A resultant centrate 5, which contains soluble lithium and ammonium sulfates, is directed to the evaporative crystallisation step 100 for the recovery of those compounds. Wet solids 4 are directed to a step 120, for example a heating step employing a kiln, in which energy is imparted to the solids, and in which the double salt is decomposed to recover a solid lithium sulfate 6 and an off-gas 7 containing ammonia and sulfur oxides. The heating stage is, for example, conducted in the range 250 °C to 1300 °C.

[0038] The off-gas 7 is contacted with water 8 and hydrogen peroxide 9 in an off-gas scrubbing or absorption step 130, for example utilising an absorber. Ammonia and sulfur oxides contained in the off-gas 7 are solubilised in water and unsaturated sulfur oxides are oxidised with hydrogen peroxide 9 to produce soluble ammonium sulfate, each in turn being contained in scrub liquor 10. Scrub liquor 10, is then directed to evaporative crystallisation stage 140, for example using a forced circulation crystalliser, and ammonium sulfate crystallised from solution.

[0039] Crystalliser discharge slurry 12 is subjected to solid liquid separation step 150, for example utilising a centrifuge. The resultant centrate 14, which contains soluble ammonium sulfate, is directed to the off-gas adsorber 130, for recovery of ammonium sulfate. Wet solids 13 from the solid liquid separation step 150 are directed to a dryer 160 for production of dry ammonium sulfate 15.

[0040] As can be seen with reference to the above description, the method of the present invention is understood to be particularly useful for the recovery of lithium sulfate from spent Li-ion batteries when ammonia is used as a reagent.

[0041] Modifications and variations such as would be apparent to the skilled addressee are considered to fall within the scope of the present invention.

Example

[0042] 3.0 kg of a solution containing 15g/L Li as lithium sulfate and 360g/L ammonium sulfate was heated to evaporate water. A total of 1.04 kg of water was evaporated in which crystals of LiNELSCh were formed. The resultant slurry was filtered. A total of 131g of solids containing 5.64 wt% Li was recovered. The filtrate contained 20.0 g/L Li.

[0043] The solids were batch calcined at 550 °C for 4 hours. The final product contained 12.4 wt% Li. Pure lithium sulfate contains 12.6% Li.

[0044] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. A method for the recovery of lithium sulfate from an aqueous solution comprising lithium sulfate and ammonium sulfate, the method comprising: concentrating the aqueous solution and forming a lithium ammonium sulfate (LiNH4SO2) precipitate in the aqueous solution; separating the lithium ammonium sulfate precipitate from the solution; and decomposing the lithium ammonium sulfate precipitate to form solid lithium sulfate.

2. The method of claim 1, wherein the step of decomposing the lithium ammonium sulfate precipitate forms an off-gas comprising ammonia and one or more sulfur oxides.

3. The method of claim 2, wherein the method further comprises recovering ammonia and one or more sulfur oxides in the off-gas.

4. The method of claim 3, wherein the step of recovering the ammonia and one or more sulfur oxides in the off-gas comprises: contacting the off-gas with an aqueous adsorbent solution in a wet scrubber to adsorb the ammonia and one or more sulfur oxides to form an aqueous liquor comprising ammonia and one or more sulfur oxides.

5. The method of claim 4, wherein the aqueous adsorbent solution comprises an oxidant.

6. The method of claim 5, wherein the oxidant is selected from the group consisting of: air, oxygen, hydrogen peroxide, and combinations thereof.

7. The method of any one of claims 4 to 6, wherein the method further comprises reacting ammonia and one or more sulfur oxides in the aqueous liquor to form ammonium sulfate.

8. The method of claim 7, wherein the step of reacting ammonia and one or more sulfur oxides to form ammonium sulfate comprises: subjecting the aqueous liquor to an evaporative crystallisation process to precipitate the ammonium sulfate.

9. The method of claim 8, wherein the method further comprises separating the precipitate of ammonium sulfate from the aqueous liquor.

10. The method of any one of the preceding claims, wherein the decomposing step comprises heating the lithium ammonium sulfate to a temperature in the range of from about 250 °C to 1300 °C.

11. The method of any one of the preceding claims, wherein the step of concentrating the aqueous solution comprises: subjecting the aqueous solution to an evaporative crystallisation process.

12. The method of any one of the preceding claims, wherein the step of separating the lithium ammonium sulfate precipitate from the solution comprises: subjecting the aqueous solution containing the lithium ammonium sulfate precipitate to a solid-liquid separation process to provide a solid stream comprising the lithium ammonium sulfate precipitate and a liquid stream.

13. The method of claim 12, wherein the liquid stream is substantially saturated with Li⁺ and/or NH

14. The method of claim 12 or 13, wherein the method further comprises recycling the liquid stream as a component of the aqueous solution at or prior to the step of concentrating the aqueous solution.

15. The method of any one of the preceding claims, wherein prior to the concentrating step, the method further comprises: obtaining the aqueous solution from a process comprises leaching lithium containing electronic waste.

16. The method of any one of the preceding claims, wherein the aqueous solution is substantially free of Co, Cu, Ni, and Mn.

17. A method for recovering lithium in the form of lithium sulfate from electronic waste comprising one or more lithium compounds, the method comprising: leaching the electronic waste with a leach solution to provide a leachate comprising Li ions; wherein the leachate comprises ammonium ions and sulfate ions and/or the leachate is subjected to one or more treatment steps which introduce a source of or ammonium ions and/or sulfate ions into the leachate; subjecting the leachate to the method of any one of claims 1 to 16, wherein the leachate is fed to the concentrating step as the aqueous solution.

18. A lithium sulfate product produced according to the method of any one of the preceding claims.

19. A method for the recovery of lithium sulfate from a feed stream, the feed stream being a solution containing lithium sulfate and ammonium sulfate, the method comprising:

(iii) returning the liquor, with any contained lithium sulfate and ammonium sulfate, to a precedent process to recover further lithium sulfate and ammonium sulfate or use ammonium sulfate as a reagent; and

20. A method for the recovery of lithium sulfate from a feed stream, the feed stream being a solution containing lithium sulfate and ammonium sulfate, the method comprising:

(v) absorption of the ammonia and sulfur oxide gasses in a liquor; and