Lithium extraction

Abstract

An embodiment provides a process for extracting lithium ions, comprising providing a lithium-rich leachate formed from leaching a lithium-containing mineral with an alkaline substance or solution, and reducing a pH of the lithium-rich leachate with an acid to form a lithium-containing solution. The process may also include subjecting the lithium-containing solution to osmotically assisted reverse osmosis (OARO) to increase a concentration of lithium ions and overall salinity forming a concentrated lithium-containing solution, and contacting the concentrated lithium-containing solution with a lithium-selective sorbent to extract lithium ions from the lithium-containing solution to form a lithium-depleted waste brine. The waste brine from the sorbent may be used as a draw solution in the osmotically assisted reverse osmosis. The process may also include desorbing the extracted lithium ions from the lithium-selective sorbent to form a lithium ion-containing solution.

Description

[0001] Lithium Extraction

[0002] Technical Field

[0003] The disclosure relates to the field of lithium extraction and purification processes, such as use of direct lithium extraction.

[0004] Background

[0005] The global demand for lithium has increased dramatically in recent years, driven by the rapid growth of electric vehicles and renewable energy storage systems. This surge in demand has put pressure on existing lithium production methods, highlighting the need for more efficient and sustainable extraction techniques. Traditional lithium extraction processes, particularly those involving hard rock mining of spodumene ores, are energy-intensive and often environmentally disruptive.

[0006] Conventional methods for extracting lithium from spodumene typically involve high-temperature conversion of a-spodumene to p-spodumene, followed by sulfuric acid roasting. This process requires temperatures of around 1100°C for the conversion step, resulting in substantial energy consumption and associated carbon emissions. Furthermore, the acid leaching and subsequent purification steps which rely heavily on reagent addition generate large volumes of waste. This process typically has a carbon footprint several times larger than evaporative method used for processing lithium-containing brines (e.g., Atacama salt flat brine).

[0007] Alternative approaches, such as direct lithium extraction (DLE) technologies, have shown promise in addressing some of these challenges, particularly for brine resources. However, adapting these technologies for use with hard rock ores has proven difficult due to the complex mineralogy and high impurity content of the leach solutions. Additionally, the high sodium content in some leach solutions poses a challenge for efficient lithium recovery and purification. Lithium sorbents are a very common direct lithium extraction technology; however, this approach favours high salinity as a high concentration of competing ions (e.g., sodium, potassium) will reduce the strong hydration layer associated with lithium. The mitigation of the hydration layer will facilitate its binding to the lithium sorbent material. As such, salinities as high as 300 to 400 g / L are necessary to achieve the highest sorbent capacity values.The lithium from a-spodumene can be effectively leached through a high temperature reaction with either concentrated sodium hydroxide / calcium oxide solutions or molten sodium hydroxide. The addition of CaO drives the equilibrium reaction to form NaCaHSiC which helps to libertate LiOH. A common feature with both methods is that the treated spodumene needs to be washed with water to effectively leach the lithium from the spodumene and then neutralised with acid solution. This addition of water and neutralisation solution results in a significant dilution of the resulting brine stream which leads to reduced lithium sorbent capacity.

[0008] Summary

[0009] An embodiment provides a process extracting lithium ions from lithium-containing minerals, comprising:

[0010] providing a lithium-rich leachate formed from leaching a lithium-containing mineral with an alkaline substance or solution;

[0011] reducing a pH of the lithium-rich leachate with an acid to form a lithium-containing solution;

[0012] subjecting the neutralised lithium-containing solution to osmotically assisted reverse osmosis (OARO) to increase a concentration of lithium ions and overall salinity forming a concentrated lithium-containing solution;

[0013] contacting the concentrated lithium-containing solution with a lithium-selective sorbent to extract lithium ions from the neutralised lithium-containing solution to form a lithium-depleted waste brine;

[0014] using the waste brine from the sorbent as a draw solution in the osmotically assisted reverse osmosis; and

[0015] desorbing the extracted lithium ions from the lithium-selective sorbent to form a lithium ion-containing solution.

[0016] Reducing the pH of the lithium-rich leachate may include reducing a pH <9. The pH may be reduced to a vale ranging from 5 to 9. Reducing the pH of the lithium-rich leachate may be termed “neutralisation”.

[0017] An embodiment provides a process extracting lithium ions from lithium-containing minerals, comprising:

[0018] providing a lithium-rich leachate formed from leaching a lithium-containing mineral with an alkaline substance or solution;

[0019] neutralising the lithium-rich leachate with an acid to form a neutralised lithium-containing solution;subjecting the neutralised lithium-containing solution to osmotically assisted reverse osmosis (OARO) to increase a concentration of lithium ions and overall salinity forming a concentrated lithium-containing solution;

[0020] contacting the concentrated lithium-containing solution with a lithium-selective sorbent to extract lithium ions from the neutralised lithium-containing solution to form a waste brine;

[0021] using the lithium-depleted brine effluent from the sorbent as a draw solution in the osmotically assisted reverse osmosis; and

[0022] desorbing the extracted lithium ions from the lithium-selective sorbent to form a lithium ion-containing solution.

[0023] The lithium-containing mineral may be a-spodumene. The spodumene may be a-spodumene and / or p-spodumene. The alkaline solution used for leaching may comprise sodium hydroxide and / or calcium hydroxide / oxide. The acid used for reducing the pH of the lithium-rich leachate may be hydrochloric acid or sulfuric acid. The osmotically assisted reverse osmosis may be performed using a semi-permeable reverse-osmosis type membrane at a pressure up to 20 bar.

[0024] The lithium-selective sorbent used in the process may comprise an ion exchange resin and / or a material that can intercalate lithium ions. The process may further include subjecting the waste brine to electrodialysis to generate sodium hydroxide and hydrochloric acid / sulfuric acid after its use as the draw solution. Desorption of the extracted lithium ions may involve using an eluent solution.

[0025] The process may include adjusting the pH of the lithium-containing solution prior to the osmotically-assisted reverse osmosis process. The concentration of lithium ions in the concentrated lithium-containing solution resulting from a feed side of the OARO is typically higher than in the neutralised (i.e. >5 pH <9) lithium-containing solution. Specifically, the concentration of lithium ions in the concentrated solution before contacting with the lithiumselective sorbent may be at least 400 ppm, while the concentration in the waste brine after contacting with the sorbent may be up to 80 ppm. The waste brine resulting from the end stage of the draw side of the OARO may have a lower osmotic pressure than the lithium-containing solution.

[0026] The process may further involve subjecting the lithium ion-containing solution to nanofiltration to remove multivalent ions, which may be performed at a pressure ranging from 5 bar to 20 bar. The nanofiltration may remove ions including Ca2+, Mg2+, Fe3+, Mn2+, Mn3+, Mn4+, and Al3+.Additional steps may include subjecting the lithium ion-containing solution resulting from desorption of the sorbent to reverse osmosis to further increase the concentration of lithium ions, potentially to at least 1000 ppm. The process may also include subjecting the lithium ioncontaining solution to electrodialysis to form lithium hydroxide and hydrochloric acid, which may be performed using a bipolar membrane electrodialysis cell. The lithium hydroxide formed by the electrodialysis may have a purity of at least 95%.

[0027] The osmotically assisted reverse osmosis step may involve multiple stages arranged in series, configured to progressively increase the concentration of lithium ions in the lithium-containing solution. The waste brine from the sorbent process may then be used as a draw solution in at least one stage of the multiple stages, which may comprise at least three stages and may be operated at different pressures. The process may also include recycling a portion of the concentrated lithium-containing solution from a later stage to an earlier stage of the multiple stages of osmotically assisted reverse osmosis.

[0028] An embodiment provides a system for extracting lithium ions, comprising:

[0029] a leaching unit configured to leach a lithium-containing mineral with an alkaline substance or solution to produce a lithium-rich leachate;

[0030] a neutralisation unit configured to reduce a pH of the lithium-rich leachate with an acid to form a lithium-containing solution;

[0031] an osmotically assisted reverse osmosis unit configured to subject the lithium-containing solution to osmotically assisted reverse osmosis to increase a concentration of lithium ions and overall brine salinity to form a concentrated lithium-containing solution; a sorbent unit comprising a lithium-selective sorbent configured to contact the concentrated lithium-containing solution to extract lithium ions and desorb the extracted lithium ions to produce a lithium ion-containing solution; and

[0032] a brine recirculation system configured to use lithium-depleted brine from the sorbent unit as a draw solution in the osmotically assisted reverse osmosis unit.

[0033] The leaching unit may be configured to operate at a temperature above 200°C. The system may include a filtration unit for removing solid residues from the lithium-rich leachate. The neutralisation unit may be configured to adjust the pH of the lithium-rich leachate to a range of 5 to 9 and / or to remove impurities precipitated from the lithium-containing solution.

[0034] The osmotically assisted reverse osmosis unit may comprise a semi-permeable membrane and may be configured to operate at a pressure up to 20 bar. It may include multiple stages arranged in series to progressively increase the lithium concentration, potentially achieving aconcentration of at least 400 to 1000 ppm in the concentrated solution. The unit may also use spiral-wound membrane or hollow-fibre modules.

[0035] The sorbent unit may comprise various types of sorbents including ion exchange resins, lithium aluminium layered double hydroxide sorbents, lithium manganese oxide sorbents, and / or lithium titanium oxide sorbents. It may be configured to operate in a continuous flow mode and may include multiple columns arranged in parallel for simultaneous adsorption and desorption processes. The unit may use a dilute lithium chloride solution as a stripping solution for desorption, with a concentration ranging from 50 to 250 ppm and may operate at a temperature between 40°C and 80°C during desorption. The stripping solution may prevent decomposition of lithium-aluminium layered double hydroxide sorbents to aluminium hydroxide during desorption.

[0036] The waste brine recirculation system may comprise a pump configured to circulate the waste brine to the osmotically assisted reverse osmosis unit. The brine recirculation system may be configured to recycle at least a portion of the lithium-depleted brine which contains sodium hydroxide and / or calcium hydroxide / oxide to a regeneration unit for initial alkaline digestion of new lithium-containing mineral.

[0037] The system may include a polishing unit for removing multivalent ions from the lithium-containing solution. The polishing unit may comprise an ion exchange resin selective for multivalent ions. The multivalent ions may include Ca2+, Mg2+, Fe3+, Mn2+, Mn3+, Mn4+, and Al3+.

[0038] The system may include a reverse osmosis unit for further concentrating the solution, and an electrodialysis unit for producing lithium hydroxide and hydrochloric acid. The reverse osmosis unit may be configured to increase the concentration of lithium ions to at least 1000 ppm. The system may further include a first electrodialysis unit configured to process the lithium-containing solution to produce lithium hydroxide and hydrochloric acid. The first electrodialysis unit may be configured to produce lithium hydroxide with a purity of at least 95%. The first electrodialysis may be configured to recycle the produced hydrochloric acid to the neutralisation unit. The system may further comprise a second electrodialysis unit configured to process the waste brine from the draw side of the osmotically assisted reverse osmosis unit to produce sodium hydroxide and hydrochloric acid. The second electrodialysis unit may be configured to recycle the produced hydrochloric acid back to the neutralisation unit and / or the recycle the sodium hydroxide to the leaching unit. The first electrodialysis unit and second electrodialysis unit may each comprise a bipolar membrane electrodialysis cell.One or embodiments of the process and / or system may provide an efficient method for extracting and purifying lithium from lithium-containing minerals, with particular advantages in handling high sodium concentrations and reducing energy requirements through the innovative use of osmotically assisted reverse osmosis, waste brine recirculation and reagent recycling.

[0039] Brief Description of the Drawings

[0040] Embodiments will now be described, by way of example only, with reference to the accompanying non-limiting drawings, in which:

[0041] Figure 1 is a schematic diagram of an embodiment of a system for processing a lithium solution.

[0042] Figure 2 is a schematic diagram of an embodiment of a lithium extraction and purification system.

[0043] Figure 2a is a schematic diagram of an embodiment of a system for processing a lithium-containing solution.

[0044] Figure 3 is a schematic diagram of an embodiment of a system for processing a lithium chloride solution.

[0045] Figure 4 is a schematic diagram of an embodiment of a system for processing a lithium-containing solution.

[0046] Detailed Description

[0047] The present disclosure relates to a system and process for extracting and purifying lithium from lithium-containing materials. One or more embodiments may provide an efficient and economical method for producing high-purity lithium compounds suitable for use in various applications, including battery production. Embodiments utilise a combination of leaching such as alkaline leaching, pH reduction (also termed “neutralisation”), osmotically assisted reverse osmosis, and selective adsorption to extract and concentrate lithium ions from lithium-containing materials.

[0048] As used herein, the term "lithium-containing mineral" may refer to any naturally occurring or processed mineral that contains lithium in a form that can be extracted through leaching or other chemical processes. The lithium-containing mineral may include various lithium-bearing silicate minerals, lithium-bearing phosphate minerals, or lithium-bearing pegmatite minerals. In some embodiments, the lithium-containing mineral may comprise spodumene. In some embodiments, the lithium-containing material may comprise a-spodumene, a mineral commonly found in lithium-rich ores. In some embodiments, the lithium-containing mineralmay comprise a-spodumene that is processed directly without conversion to p-spodumene. In some embodiments, the lithium-containing mineral may comprise p-spodumene. In some embodiments, the lithium-containing mineral may comprise a mixture of a-spodumene and p-spodumene. The lithium-containing mineral may also include other lithium-bearing minerals such as lepidolite, petalite, amblygonite, or eucryptite.

[0049] In an embodiment, the process begins with an alkaline leaching step, where the lithium-containing mineral is treated with an alkaline solution. The alkaline solution may comprise sodium hydroxide and / or calcium hydroxide / oxide. In some embodiments, molten sodium hydroxide may be used for the leaching process, which can enhance the extraction efficiency.

[0050] Following the alkaline leaching, the resulting lithium-rich leachate undergoes a pH adjustment step where the pH is reduced and form a lithium-containing solution. The pH adjustment may be performed using an acid, which in some embodiments may comprise hydrochloric acid or sulfuric acid. This pH adjustment step prepares the solution for subsequent processing stages. In some embodiments, pH adjustment includes neutralising the lithium-rich leachate.

[0051] The lithium-containing solution is then subjected to osmotically assisted reverse osmosis, which concentrates the lithium ions in the lithium-containing solution and increases the overall brine salinity which increases the sorbent capacity. This concentrated solution is then processed using a lithium-selective sorbent to extract and purify the lithium ions. The lithiumselective sorbent may comprise an ion exchange resin and / or a material that can intercalate lithium ions, allowing for efficient separation of lithium from other ions present in the solution. Lithium-depleted brine effluent from the sorbent can also be used as a draw solution in the osmotically assisted reverse osmosis.

[0052] The system and process of one or more embodiments are designed to be versatile and can be adapted for different lithium-containing solutions. For example, the process may be used to extract and purify lithium from solutions containing lithium chloride (LiCI) or lithium sulfate (□2804). This flexibility allows the system to be applied to various lithium sources and production requirements. By combining these various steps and components, one or more embodiments may provide a comprehensive solution for lithium extraction and purification, addressing the growing demand for high-purity lithium compounds in the global market.

[0053] Figure 1 illustrates a system 10 for processing a lithium-containing solution. The system 10 comprises several components arranged in a specific configuration to process a lithium hydroxide solution 12. The lithium hydroxide solution 12 may be formed from leaching alithium-containing mineral with an alkaline solution. In some embodiments, the lithium-containing material may comprise a-spodumene and / or p-spodumene. The alkaline solution may comprise a significant amount sodium hydroxide and / or calcium hydroxide / oxide which are derived from alkaline roasting / digestion of spodumene.

[0054] The lithium hydroxide solution 12 is first treated in a neutraliser 14 to reduce a pH of the lithium-rich leachate to form a lithium-containing solution. This step of pH reduction typically reduces a pH of the lithium-containing solution to range from 5 to 9, such as 6-8. Accordingly, the step of pH reduction to have a pH ranging from 5 to 9 may also be referred to “neutralisation”. It should be appreciated that the term “neutralisation” and its variants such as “neutralise”, “neutralised”, “neutralising” and so on does not require the pH to be at or close (e.g. ±0.1) to 7, and that any pH within a predefine range, such as 5-9, falls within the scope of the term “neutralisation”. The purpose of adjusting the pH of the lithium-rich leachate is to drop the pH below an upper threshold limit to allow for and / or assist with further processing. Throughout this disclosure, the terms “reduce a pH” and “neutralise” and its variants are used interchangeable unless context makes it clear otherwise.

[0055] The neutraliser 14 is configured to adjust the pH of the lithium hydroxide solution 12 by adding an acid to neutralise the alkaline solution. The neutraliser 14 may adjust a pH of the lithium hydroxide solution 12 to range from about 5 to about 9. In some embodiments, the acid may comprise hydrochloric acid or sulfuric acid.

[0056] Following the neutraliser 14, the neutralised lithium-containing solution is passed into an osmotically assisted reverse osmosis (OARO) unit 16. The OARO unit 16 is configured to concentrate the lithium in the solution by subjecting the neutralised lithium-containing solution to osmotically assisted reverse osmosis. This osmosis process helps to increase the concentration of lithium ions and form a concentrated lithium-containing solution.

[0057] The concentrated solution from the OARO unit 16 is then passed into a sorbent unit 18. The sorbent unit 18 comprises a lithium-selective sorbent configured to contact the concentrated lithium-containing solution to extract lithium ions from the concentrated solution. The lithium-depleted brine effluent formed following extraction of lithium ions from the concentrated lithium-containing solution can be considered as forming a waste solution or waste brine that is used as a draw solution 22 that is utilised in the OARO unit 16. Unless context make clear otherwise, the terms “waste solution” and “waste brine” in respect to the solution formed following extraction of lithium ions from the concentrated lithium-containing solution and theterm “lithium-depleted brine effluent” can be used interchangeable. The draw solution 22 may form part of a waste brine recirculation system.

[0058] In some embodiments, the lithium-rich leachate produced from alkaline leaching of spodumene may have a relatively low lithium purity due to the presence of sodium ions derived from the alkaline digestion process. In alkaline leaching of spodumene, the resulting leachate typically has a high sodium to lithium ratio, for example in the range of 60:1 to 100:1. In some cases, the Na / Li ratio may be approximately 60:1. In some cases, the Na / Li ratio may be approximately 70:1. In some cases, the Na / Li ratio may be approximately 80:1. In some cases, the Na / Li ratio may be approximately 90:1. In some cases, the Na / Li ratio may be approximately 100:1. The Na / Li ratio may range from 60:1 to 90:1. The Na / Li ratio may range from 60:1 to 80:1. The Na / Li ratio may range from 70:1 to 100:1. The Na / Li ratio may range from 80:1 to 100:1. These high Na / Li ratios may be comparable to those found in salt flat or lake brines. As lithium represents a dilute species relative to sodium in the feed solution, the removal of lithium by the sorbent unit 18 may not substantially affect the overall salinity of the brine. This characteristic may make the lithium-depleted brine well-suited for use as the draw solution 22, as its osmotic pressure remains similar to that of the concentrated lithium-containing solution exiting the OARO unit 16.

[0059] In some embodiments, the osmotically assisted reverse osmosis (OARO) unit 16 may comprise a spiral-wound membrane module. The spiral-wound membrane module may include a flat sheet membrane wrapped around a perforated central collection tube. The membrane may be separated by spacer materials to create feed and permeate channels. The spiral-wound configuration may allow for a high membrane surface area to be packed into a compact volume, potentially increasing the efficiency of the OARO process. In operation, the feed solution may flow axially along the membrane envelope, while the permeate may flow radially towards the central collection tube.

[0060] The spiral-wound membrane module in the OARO unit 16 may be designed to withstand the operating pressures required for the osmotically assisted reverse osmosis process. The module may incorporate feed spacers to promote turbulence and reduce concentration polarisation, which may enhance the overall performance of the OARO unit 16. The materials used in the spiral-wound membrane module may be selected for their compatibility with the lithium-containing solutions and their resistance to fouling. In some embodiments, the membrane material may be a thin-film composite optimised for lithium ion retention while allowing water to pass through.In some embodiments, the osmotically assisted reverse osmosis (OARO) unit 16 may comprise a hollow fibre membrane module. The hollow fibre membrane module may include an assembly of hollow fibre membranes bundled together. The feed flows internally through the hollow fibres and the permeate flows through the void space between the fibres in the bundle. The hollow fibre membrane bundle configuration may allow for a high membrane surface area to be packed into a compact volume, potentially increasing the efficiency of the OARO process.

[0061] The hollow fibre membrane bundle module in the OARO unit 16 may be designed to withstand the operating pressures required for the osmotically assisted reverse osmosis process. The module may incorporate feed spacers to promote turbulence and reduce concentration polarisation, which may enhance the overall performance of the OARO unit 16. The materials used in the hollow fibre membrane bundle module may be selected for their compatibility with the lithium-containing solutions and their resistance to fouling. In some embodiments, the membrane material may be a thin-film composite optimised for lithium ion retention while allowing water to pass through.

[0062] In an embodiment, the OARO unit 16 may operate at pressures ranging from 10 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 19 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 18 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 17 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 16 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 15 bar. The OARO unit 16 may operate at pressures ranging from 10 bar to 14 bar. The OARO unit 16 may operate at pressures ranging from 11 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 12 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 13 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 14 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 15 bar to 20 bar. The OARO unit 16 may operate at pressures ranging from 16 bar to 20 bar. The OARO unit 16 may operate at pressures of at least 10 bar. The OARO unit 16 may operate at pressures of at least 11 bar. The OARO unit 16 may operate at pressures of at least 12 bar. The OARO unit 16 may operate at pressures of at least 13 bar. The OARO unit 16 may operate at pressures of at least 14 bar. The OARO unit 16 may operate at pressures of at least 15 bar. The OARO unit 16 may operate at pressures of at least 16 bar. The OARO unit 16 may operate at pressures up to 20 bar. The OARO unit 16 may operate at pressures up to 19 bar. The OARO unit 16 may operate at pressures up to 18 bar. The OARO unit 16 may operate at pressures up to 17 bar. The OARO unit 16 may operate at pressures up to 16 bar. The OARO unit 16 may operate at pressures up to 15 bar. The OARO unit 16 may operate at pressuresup to 14 bar. The specific pressure used may depend on factors such as the concentration of the feed solution, desired recovery rate, and membrane characteristics. For solutions with higher total dissolved solids (TDS), pressures towards the upper end of this range may be employed. In some embodiments, the pressure may be adjusted dynamically during operation to optimise performance and energy efficiency.

[0063] In some embodiments, the concentrated lithium-containing solution produced by the OARO unit 16 may have a significantly higher lithium concentration compared to the initial neutralised solution in part due to an increase in the overall salinity. The concentration process may result in a lithium content of at least 1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 500-1000 ppm in the concentrated solution prior to contacting the lithiumselective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 600-1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 700-1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 800-1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 900-1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 1000-1500 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 1000-2000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 1000-2500 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of 1000-3000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18.

[0064] The concentration process may result in a lithium content of at least 500 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 600 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 700 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 800 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18.The concentration process may result in a lithium content of at least 900 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of up to 1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 1000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 1500 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 2000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 2500 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. The concentration process may result in a lithium content of at least 3000 ppm in the concentrated solution prior to contacting the lithium-selective sorbent in the sorbent unit 18. This increased concentration may enhance the efficiency of the subsequent sorption process.

[0065] After the concentrated lithium-containing solution contacts the lithium-selective sorbent in the sorbent unit 18, the resulting brine, termed 'processed brine' given it has been processed by the sorbent unit 18, may have a substantially reduced lithium content. In an embodiment, the concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 80 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 75 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 70 ppm. The concentration of lithium ions in the processed brine after contacting with the lithiumselective sorbent may be up to 65 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 60 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 55 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be up to 50 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be at least 50 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be at least 55 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be at least 60 ppm. The concentration of processed ions in the treated brine after contacting with the lithiumselective sorbent may be at least 65 ppm. The concentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be at least 70 ppm. Theconcentration of lithium ions in the processed brine after contacting with the lithium-selective sorbent may be at least 75 ppm.

[0066] The difference in lithium concentration between the concentrated solution and the processed brine may reflect the efficiency of the lithium extraction process. The substantial decrease in lithium content from at least 400 ppm to up to 80 ppm may suggest a high lithium recovery rate by the sorbent unit 18. This concentration differential may also contribute to the effectiveness of using the processed brine as a draw solution 22 in the OARO unit 16, as it may have a slightly lower osmotic pressure due to the removal of lithium compared to the incoming concentrated lithium-containing solution.

[0067] Using the processed brine as a draw solution 22 in the OARO unit 16 may enhance overall efficiency of the system 10 by reducing the feed pressure requirements due to a decrease in the transmembrane osmotic gradient. Additionally, recycling the processed brine as a draw solution 22 may help minimise water consumption and reduce waste volume. In some embodiments, this circular use of processed brine may also contribute to lowering operational costs by decreasing the need for additional chemicals or draw solution pre-treatment. The processed brine may have a higher salinity than the feed solution, which can improve the performance of the OARO process. Utilising the processed brine in this manner may allow the OARO unit 16 to operate at lower pressures compared to conventional reverse osmosis, potentially reducing energy requirements. Furthermore, this approach may enable higher recovery rates of lithium from the feed solution.

[0068] In some embodiments, a flow ratio between the feed solution and the draw solution 22 in the OARO unit 16 may be configured to optimise the concentration process. The flow ratio may be a 1:1 flow ratio, wherein the volumetric flow rate of the feed solution entering the OARO unit 16 is substantially equal to the volumetric flow rate of the draw solution 22. In some cases, the flow ratio between the feed solution and the draw solution 22 may range from 0.8:1 to 1.2:1. The flow ratio may range from 0.9:1 to 1.1:1. The flow ratio may range from 0.95:1 to 1.05:1. In some embodiments, maintaining a 1:1 flow ratio may help to balance the mass transfer across the membrane and maintain a relatively constant salinity differential along the length of the membrane module. The feed solution and the draw solution 22 may be directed in a counter-current flow. A 1:1 flow ratio in a counter-current configuration may allow the osmotic pressure difference across the membrane to be kept relatively uniform throughout the OARO unit 16, which may reduce localised concentration polarisation effects. For example, when the OARO unit 16 includes hollow fibre membrane(s), the feed flows inside the hollow fibers and the draw flows countercurrent on the outside of the hollow fibers. In this way thepressure differential across the membrane can be kept to a minimum along the length of the fiber thus reducing the pump pressure (and required power required). In some embodiments, the 1:1 flow ratio may simplify process control and reduce the complexity of the system by eliminating the need for intermediate closed-loop sweep streams that would otherwise require periodic adjustment to maintain steady-state conditions. The flow ratio may be adjusted based on factors such as the desired concentration factor, membrane characteristics, and the specific composition of the lithium-containing solution.

[0069] The sorbent unit 18 is also configured to desorb the extracted lithium ions to produce a lithium chloride solution 20. For example, once the sorbent in the sorbent unit 18 reaches a defined lithium ion absorption threshold, the absorbed lithium ions are desorbed using a desorbing solution to form a purified lithium chloride solution 20. The lithium chloride solution 20 can form the extracted and concentrated lithium product.

[0070] The sorbent unit 18 may operate under various conditions to optimise the sorption and desorption of lithium ions. During the sorption process, the concentrated lithium-containing solution may flow through the sorbent unit 18 at a controlled rate to allow sufficient contact time between the solution and the sorbent material.

[0071] The sorption process may be conducted at temperatures ranging from 20°C to 70°C. The sorption process may be conducted at temperatures ranging from 20°C to 55°C. The sorption process may be conducted at temperatures ranging from 20°C to 50°C. The sorption process may be conducted at temperatures ranging from 20°C to 45°C. The sorption process may be conducted at temperatures ranging from 20°C to 40°C. The sorption process may be conducted at temperatures ranging from 20°C to 35°C. The sorption process may be conducted at temperatures ranging from 20°C to 30°C. The sorption process may be conducted at temperatures ranging from 25°C to 60°C. The sorption process may be conducted at temperatures ranging from 30°C to 60°C. The sorption process may be conducted at temperatures ranging from 35°C to 60°C. The sorption process may be conducted at temperatures ranging from 40°C to 60°C. The sorption process may be conducted at temperatures ranging from 45°C to 60°C. The sorption process may be conducted at temperatures ranging from 50°C to 60°C. The sorption process may be conducted at temperatures ranging from 55°C to 60°C. The sorption process may be conducted at temperatures of at least 20°C. The sorption process may be conducted at temperatures of at least 25°C. The sorption process may be conducted at temperatures of at least 30°C. The sorption process may be conducted at temperatures of at least 35°C. The sorption process may be conducted at temperatures of at least 40°C. The sorption processmay be conducted at temperatures of at least 45°C. The sorption process may be conducted at temperatures of at least 50°C. The sorption process may be conducted at temperatures of at least 55°C. The sorption process may be conducted at temperatures up to 60°C. The sorption process may be conducted at temperatures up to 55°C. The sorption process may be conducted at temperatures up to 50°C. The sorption process may be conducted at temperatures up to 45°C. The sorption process may be conducted at temperatures up to 40°C. The sorption process may be conducted at temperatures up to 35°C. The sorption process may be conducted at temperatures up to 30°C. In an embodiment, the sorption process may be conducted at 40°C. In an embodiment, the sorption process may be conducted at 50°C. In some embodiments, the pH of the solution may be adjusted to optimise lithium adsorption, typically within a range of 6 to 8.

[0072] For desorption with a lithium-aluminium layered double hydroxide sorbent, the lithium-loaded sorbent may be treated with a desorbing solution to release or desorb the adsorbed lithium ions. The desorbing solution may be a dilute warm lithium chloride solution with a concentration ranging from 50 to 250 ppm. In some embodiments, the desorbing solution may have a lithium chloride concentration of 75 ppm, 100 ppm, 150 ppm or 200 ppm. Alternatively, an acidic solution may be used for desorption, particularly with lithium manganese oxide (LMO) or lithium titanium oxide (LTO) ion exchange sorbents. In such embodiments, hydrochloric acid with concentrations ranging from 0.05 to 0.5 M may be used.

[0073] The desorption process may be carried out at elevated temperatures to enhance the efficiency of lithium release. The desorption temperature may range from 40°C to 80°C. In some embodiments, the temperature may be at least 40°C. The desorption temperature may range from 40°C to 80°C. The desorption temperature may range from 40°C to 75°C. The desorption temperature may range from 40°C to 70°C. The desorption temperature may range from 40°C to 65°C. The desorption temperature may range from 40°C to 60°C. The desorption temperature may range from 40°C to 55°C. The desorption temperature may range from 40°C to 50°C. The desorption temperature may range from 45°C to 80°C. The desorption temperature may range from 50°C to 80°C. The desorption temperature may range from 55°C to 80°C. The desorption temperature may range from 60°C to 80°C. The desorption temperature may range from 65°C to 80°C. The desorption temperature may range from 70°C to 80°C. The desorption temperature may range from 75°C to 80°C. The desorption temperature may be at least 45°C. The desorption temperature may be at least 50°C. The desorption temperature may be at least 55°C. The desorption temperature may be at least 60°C. The desorption temperature may be at least 65°C. The desorption temperature may be at least 70°C. The desorption temperature may be at least 75°C. The desorption temperaturemay be up to 80°C. The desorption temperature may be up to 75°C. The desorption temperature may be up to 70°C. The desorption temperature may be up to 65°C. The desorption temperature may be up to 60°C. The desorption temperature may be up to 55°C. The desorption temperature may be up to 50°C. In some embodiments, the temperature may be adjusted based on factors such as the specific sorbent material used and the desired desorption rate. The temperature may be adjusted based on factors such as the specific sorbent material used and the desired desorption rate.

[0074] The sorbent unit 18 may operate in a batch or continuous mode. In a continuous operation, multiple columns may be used in parallel, allowing for simultaneous sorption and desorption processes. The sorbent material may be regenerated after each desorption cycle for reuse in subsequent sorption cycles. In some embodiments, the sorbent unit 18 may include additional components such as pumps, valves, and heat exchangers to control the flow rates, pressures, and temperatures of the solutions. Monitoring and control systems may be incorporated to optimise the sorption and desorption processes based on factors such as solution composition, flow rates, and sorbent capacity.

[0075] In some embodiments, the sorbent capacity of the lithium-selective sorbent in the sorbent unit 18 may be influenced by the overall salinity of the concentrated lithium-containing solution. Higher salinity levels may destabilise the hydration layers typically associated with lithium ions, which may facilitate improved binding of lithium to the sorbent material. As an example, for lithium-aluminium layered double hydroxide sorbents, an increase in salinity from approximately 60 g / L to approximately 120 g / L may result in an increase in sorbent capacity from approximately 1.5 mg / g to approximately 1.9 mg / g. Typically, the sorbent capacity increase as the salinity increases. For example, in some cases, the sorbent capacity may increase from approximately 1.55 mg / g to approximately 1.88 mg / g when the salinity is increased from approximately 60 g / L to approximately 120 g / L. This improvement in sorbent capacity may correspond to a reduction in the required column size of approximately 17%. In some embodiments, the OARO unit 16 may be configured to achieve salinity levels that provide improved sorbent capacity in the sorbent unit 18. The relationship between salinity and sorbent capacity may vary depending on the specific sorbent material used and the composition of the lithium-containing solution.

[0076] The lithium chloride solution 20 produced by the sorbent unit 18 may have a concentration of lithium ions that is significantly higher and purer than the initial lithium hydroxide leachate solution 12. In some embodiments, the concentration of lithium ions in the lithium chloride solution 20 may range from 1000 ppm to 10,000 ppm. The exact concentration may dependon factors such as the efficiency of the OARO unit 16 and the performance of the lithiumselective sorbent in the sorbent unit 18.

[0077] The lithium chloride solution 20 may have a pH in the range of 5 to 9. The solution may contain primarily lithium and chloride ions, with reduced levels of impurities compared to the initial lithium hydroxide solution 12. In some embodiments, the lithium chloride solution 20 may have a purity of at least 90%, with respect to other metal ions. The solution may have a lower concentration of sodium, potassium, magnesium, and calcium ions compared to the initial leachate. The specific gravity of the lithium chloride solution 20 may range from 1.01 to 1.20, depending on the concentration of lithium chloride.

[0078] In some embodiments, the lithium chloride solution 20 may contain trace amounts of other elements, such as boron, silicon, or aluminium, at concentrations typically below 100 ppm. The presence and concentration of these trace elements may vary depending on the source material and the efficiency of the purification process.

[0079] A waste brine flow 24 from the OARO unit 16, which typically includes the draw solution 22, forms a waste brine 28 which may be isolated and discarded or directed back into the system 10.

[0080] In some embodiments, the waste brine 28 may be subjected to conventional reverse osmosis to recover water. The waste brine 28, having a lower salinity compared to the concentrated lithium-containing solution on the feed side, may be amenable to processing by conventional reverse osmosis, such as that operating at pressures up to approximately 70 to 80 bar. The recovered water from the waste brine 28 may be utilised within the system 10 for various purposes. In some cases, the recovered water may be used for washing steps associated with the lithium sorbent in the sorbent unit 18. In some embodiments, the recovered water may be used to prepare the desorbing solution for releasing adsorbed lithium ions from the lithiumselective sorbent. For example, the recovered water may be used to prepare the dilute lithium chloride stripping solution employed during desorption of lithium-aluminium layered double hydroxide sorbents. This recovery and reuse of water from the draw side effluent may reduce the overall water consumption of the system 10 and contribute to improved process efficiency.

[0081] The system 10 may provide a continuous flow process where each component plays a specific role in the extraction and concentration of lithium from the initial lithium hydroxide solution 12.Figure 2 illustrates a process 100 for extracting and purifying lithium from spodumene. The process 100 incorporates components from system 10, and like features are described with like references.

[0082] The process 100 begins with spodumene leaching 108 in a leaching unit. During spodumene leaching 108, a-spodumene may be treated with an alkaline solution to produce the lithium hydroxide solution 12 with calcium and sodium impurities derived from the lithium extraction process from spodumene. The spodumene leaching 108 may be configured to operate at a temperature above 200°C. For example, the temperature may range from 200°C to 330°C. In some embodiments, the spodumene leaching 108 may be performed at temperatures between 220°C and 280°C. The temperature may be selected based on factors such as the specific composition of the spodumene ore, concentration of sodium hydroxide and / or calcium oxide / hydroxide, desired reaction kinetics, and energy efficiency considerations. In some embodiments, higher temperatures within this range may lead to faster leaching rates, while lower temperatures may be more energy efficient. The spodumene leaching 108 may also be conducted under pressure in some implementations, with pressures potentially ranging from 1 to 50 bar. The combination of elevated temperature and pressure may enhance the extraction of lithium from the spodumene ore in some embodiments.

[0083] In some embodiments, molten sodium hydroxide leaching may be employed for the extraction of lithium from a-spodumene. This process may involve heating sodium hydroxide to its melting point, which occurs at approximately 318°C, to create a molten state. The molten sodium hydroxide is then brought into contact with the lithium-containing material. Following the molten sodium hydroxide leaching, the resulting mixture may be cooled and diluted with water to form the lithium hydroxide solution 12. The use of molten sodium hydroxide leaching may be beneficial for processing refractory lithium-containing materials that are resistant to conventional aqueous leaching methods.

[0084] In some embodiments, a filtration unit may be used to remove solid residues from the lithium-rich leachate produced during spodumene leaching 108. The filtered leachate may then be directed to the neutraliser 14, the osmotically assisted reverse osmosis unit 16 and sorbent unit 18 to form the lithium chloride solution 20 as described for system 10.

[0085] Figure 2a illustrates a multi-stage osmotically assisted reverse osmosis (OARO) unit 16 for processing a lithium-containing solution. The OARO unit 16 comprises multiple stages arranged in series, including a first OARO stage 16a, a second OARO stage 16b, and a third OARO stage 16ca. These stages are configured to progressively increase the concentrationof lithium ions in the lithium-containing solution as it passes through the OARO unit 16. The neutraliser 14 feeds the neutralised lithium-containing solution into the first OARO stage 16a. Each OARO stage may comprise a semi-permeable membrane through which water can pass, but lithium ions and other dissolved solids are retained. The waste brine flow 24, which has a slightly lower osmotic pressure than the neutralised lithium-containing solution, is used as a counter-current flow draw solution 22 in at least one stage of the OARO unit 16.

[0086] A first conduit 21a allows the partially concentrated lithium-containing solution to flow from the first OARO stage 16a to the second OARO stage 16b. Similarly, a second conduit 21b connects the second OARO stage 16b to the third OARO stage 16ca, and a third conduit 21c directs the concentrated lithium-containing solution from the third OARO stage 16ca to the sorbent unit 18. The draw solution 22 flows in the opposite direction to the lithium-containing solution through the OARO unit 16. A first draw flow connection 22a allows the draw solution 22 to flow from the second OARO stage 16b to the first OARO stage 16a. A second draw flow connection 22b connects the third OARO stage 16ca to the second OARO stage 16b, and a third draw flow connection 22c directs the processed bring from the sorbent unit 18 back to the third OARO stage 16ca. The first draw flow connection 22a, second draw flow connection 22b and third draw flow connection 22c may form part of a waste brine recirculation system. The waste brine recirculation system may include one or more pumps to pump the waste brine through the system 100.

[0087] In some embodiments, each stage of the OARO unit 16 may be operated at different pressures. This pressure differential between stages may help to optimise the concentration process and energy efficiency of the system. The pressure in each stage may be adjusted based on factors such as the concentration of the lithium-containing solution and the osmotic pressure of the draw solution 22.

[0088] The OARO unit 16 may be configured to achieve a lithium concentration of at least 400 ppm in the concentrated lithium-containing solution by the time it reaches the sorbent unit 18. This concentration may be achieved through the progressive concentration of the lithium-containing solution as it passes through each stage of the OARO unit 16. In some embodiments, a portion of the concentrated lithium-containing solution from a later stage, such as the third OARO stage 16ca, may be recycled back to an earlier stage, such as the first OARO stage 16a or the second OARO stage 16b. This recycling may help to further increase the overall concentration of lithium ions in the solution and improve the efficiency of the OARO process.The multi-stage configuration of the OARO unit 16 may allow for a more efficient concentration process compared to a single-stage system. By using multiple stages, the system can achieve higher concentration factors while potentially reducing the overall energy consumption of the process.

[0089] In some embodiments, each stage of the OARO unit 16 may be configured to achieve a salinity increase of approximately 10 g / L. For example, a single-stage OARO process operating at an applied pressure of 20 bar may change the salinity of an initial 50 g / L feed solution to approximately 56.6 g / L, representing a salinity differential of approximately 11.3 g / L. In some cases, the OARO unit 16 may operate at pressures less than 20 bar to achieve a salinity increase of approximately 10 g / L per stage. In some embodiments, the salinity increase per stage of the OARO unit 16 may range from 5 g / L to 20 g / L. The salinity increase per stage may range from 5 g / L to 15 g / L. The salinity increase per stage may range from 5 g / L to 12 g / L. The salinity increase per stage may range from 8 g / L to 20 g / L. The salinity increase per stage may range from 8 g / L to 15 g / L. The salinity increase per stage may range from 10 g / L to 20 g / L. The salinity increase per stage may range from 10 g / L to 15 g / L. The salinity increase per stage may range from 12 g / L to 18 g / L. The salinity increase per stage may be at least 5 g / L. The salinity increase per stage may be at least 8 g / L. The salinity increase per stage may be at least 10 g / L. The salinity increase per stage may be at least 12 g / L. The salinity increase per stage may be up to 20 g / L. The salinity increase per stage may be up to 18 g / L. The salinity increase per stage may be up to 15 g / L. The specific salinity increase achieved in each stage may be selected based on factors such as the applied pressure, membrane type, desired overall concentration factor, and energy efficiency considerations.

[0090] In a multi-stage configuration, the cumulative effect of these salinity increases may result in a substantial overall concentration of the lithium-containing solution. For instance, a neutralised lithium-containing solution entering the first OARO stage 16a at an initial salinity of approximately 60 g / L may be progressively concentrated through successive stages, with each stage contributing an incremental salinity increase. By the time the solution exits the final stage, such as the third OARO stage 16c, the salinity may have increased to approximately 90 g / L or higher, depending on the number of stages employed. In some embodiments, the OARO unit 16 may comprise additional stages beyond the three stages illustrated, with each additional stage contributing a further salinity increase of approximately 10 g / L. The specific salinity values achieved at each stage may vary based on factors such as the applied pressure, membrane characteristics, flow rates, and the composition of the feed and draw solutions.In some embodiments, the multi-stage OARO configuration may provide process stability benefits. The counter-current flow arrangement between the feed solution and the draw solution 22 may avoid the need for intermediate closed-loop sweep streams that would otherwise require periodic adjustment to maintain steady-state conditions. In configurations employing closed loops, the salinity of sweep streams may vary over time as reverse osmosis membranes do not exhibit complete salt rejection, which may necessitate periodic addition of salt or water to maintain steady-state conditions. By using the lithium-depleted brine effluent from the sorbent unit 18 directly as the draw solution 22 in a counter-current arrangement, in some embodiments the system 100 may operate without such closed loops. The combination of the counter-current flow arrangement and the small salinity differential across the membrane may contribute to stable operation of the OARO unit 16. The absence of closed loops may simplify process control and reduce the complexity of the system 100. In some cases, this configuration may reduce the need for monitoring and adjustment of intermediate stream compositions, which may lower operational requirements.

[0091] In the embodiment shown in Figure 2, the lithium chloride solution 20 is subjected to nanofiltration in a nanofiltration unit 110 to remove multivalent ions. A nanofiltration membrane may be used. The nanofiltration unit 110 may also use an iminodiacetate ion exchange resin to remove Al and / or Fe impurities. Additionally, a sulfonate ion exchange resin may be used to remove other multivalent impurities. The multivalent ions may include Ca2+, Mg2+, Fe3+, Mn2+, Mn3+, Mn4+, and Al3+. The removal of these ions may be achieved by passing the lithium-rich solution flow 20 through a nanofiltration membrane or a series of nanofiltration membranes. The nanofiltration process may be performed under various operating conditions, such as different pressures, temperatures, and flow rates, to optimise the removal of multivalent ions and the recovery of lithium ions. The nanofiltration unit 110 can be considered as defining a polishing unit configured to remove non-lithium species from the lithium chloride solution 20.

[0092] In some embodiments, the nanofiltration unit 110 may be operated at a pressure ranging from 5 bar to 20 bar. The pressure may be selected based on factors such as the specific nanofiltration membrane used, the composition of the lithium-rich solution flow 20, and the desired lithium recovery rate. The nanofiltration process may be configured to achieve a lithium recovery rate of at least 90%, thereby maximizing the amount of lithium that can be recovered from the lithium-rich solution flow 20.

[0093] The nanofiltration unit 110 may include one or more nanofiltration membranes arranged in various configurations. In some embodiments, the nanofiltration unit 110 may comprise asingle-stage nanofiltration system with one or more membrane modules connected in parallel. In other embodiments, the nanofiltration unit 110 may utilise a multi-stage configuration with membrane modules arranged in series to achieve higher rejection of multivalent ions. The nanofiltration unit 110 may also incorporate feed and permeate pumps to control flow rates and pressures. The unit may also feature cleaning-in-place systems to periodically clean the membranes. Pressure vessels, piping, valves, and instrumentation may be included to direct and monitor fluid flows through the nanofiltration process. In some embodiments, the nanofiltration unit 110 may utilise spiral-wound membrane elements or hollow fiber membrane modules depending on the specific application requirements.

[0094] The nanofiltration unit 110 may operate under various conditions to optimise the removal of multivalent ions and produce a purified lithium solution.

[0095] The operating pressure of the nanofiltration unit 110 may range from 5 bar to 20 bar. The operating pressure may range from 5 bar to 18 bar. The operating pressure may range from 5 bar to 16 bar. The operating pressure may range from 5 bar to 14 bar. The operating pressure may range from 5 bar to 12 bar. The operating pressure may range from 5 bar to 10 bar. The operating pressure may range from 5 bar to 8 bar. The operating pressure may range from 7 bar to 20 bar. The operating pressure may range from 9 bar to 20 bar. The operating pressure may range from 11 bar to 20 bar. The operating pressure may range from 13 bar to 20 bar. The operating pressure may range from 15 bar to 20 bar. The operating pressure may range from 17 bar to 20 bar. The operating pressure may be at least 5 bar. The operating pressure may be at least 7 bar. The operating pressure may be at least 9 bar. The operating pressure may be at least 11 bar. The operating pressure may be at least 13 bar. The operating pressure may be at least 15 bar. The operating pressure may be up to 20 bar. The operating pressure may be up to 18 bar. The operating pressure may be up to 16 bar. The operating pressure may be up to 14 bar. The operating pressure may be up to 12 bar. The operating pressure may be up to 10 bar. In an embodiment, the operating pressure may be 10 bar. In an embodiment, the operating pressure may be 15 bar.

[0096] The temperature of the lithium-rich solution flow 20 entering the nanofiltration unit 110 may be maintained between 20°C and 60°C. The temperature may range from 20°C to 55°C. The temperature may range from 20°C to 50°C. The temperature may range from 20°C to 45°C. The temperature may range from 20°C to 40°C. The temperature may range from 20°C to 35°C. The temperature may range from 20°C to 30°C. The temperature may range from 25°C to 60°C. The temperature may range from 30°C to 60°C. The temperature may range from 35°C to 60°C. The temperature may range from 40°C to 60°C. The temperature may rangefrom 45°C to 60°C. The temperature may range from 50°C to 60°C. The temperature may range from 55°C to 60°C. The temperature may be at least 20°C. The temperature may be at least 25°C. The temperature may be at least 30°C. The temperature may be at least 35°C. The temperature may be at least 40°C. The temperature may be at least 45°C. The temperature may be at least 50°C. The temperature may be at least 55°C. The temperature may be up to 60°C. The temperature may be up to 55°C. The temperature may be up to 50°C. The temperature may be up to 45°C. The temperature may be up to 40°C. The temperature may be up to 35°C. The temperature may be up to 30°C. In an embodiment, the temperature may be 40°C. In an embodiment, the temperature may be 50°C.

[0097] The pH of the feed solution may be adjusted to a range of 2 to 8 to enhance the rejection of multivalent ions while allowing monovalent lithium ions to pass through the membrane. In some embodiments, the pH may be controlled by adding small amounts of acid or base to the feed solution.

[0098] The flow rate through the nanofiltration unit 110 may be adjusted based on the concentration of the feed solution and desired recovery rate. Typical cross-flow velocities may range from 0.1 to 2 m / s to minimise concentration polarisation and fouling of the membrane surface. In some embodiments, the nanofiltration unit 110 may operate in a continuous mode, with a portion of the feed solution being recirculated to maintain a constant concentration factor.

[0099] During nanofiltration in the nanofiltration unit 110, the lithium recovery rate may range from 50% to 90%. The lithium recovery rate may range from 50% to 85%. The lithium recovery rate may range from 60% to 90%. The lithium recovery rate may range from 65% to 90%. The lithium recovery rate may range from 70% to 90%. The lithium recovery rate may range from 75% to 90%. The lithium recovery rate may range from 80% to 90%. The lithium recovery rate may range from 85% to 90%. The lithium recovery rate may be at least 50%. The lithium recovery rate may be at least 55%. The lithium recovery rate may be at least 60%. The lithium recovery rate may be at least 65%. The lithium recovery rate may be at least 70%. The lithium recovery rate may be at least 75%. The lithium recovery rate may be at least 80%. The lithium recovery rate may be at least 85%. The lithium recovery rate may be at least 90%. The lithium recovery rate may be at least 95%. The lithium recovery rate may be at least 98%. The lithium recovery rate may be at least 99%.

[0100] The nanofiltration membranes used in the nanofiltration unit 110 may have a molecular weight cut-off (MWCO) ranging from 200 to 1000 Daltons, allowing for effective separation of monovalent lithium ions from larger multivalent ions. The specific membrane characteristicsmay be selected based on the composition of the lithium-rich solution flow 20 and the desired purity of the final product.

[0101] In some embodiments, the nanofiltration unit 110 may incorporate a cleaning cycle to maintain membrane performance. This may involve periodic flushing with cleaning solutions to remove accumulated foulants and scale. The frequency and duration of cleaning cycles may be adjusted based on the feed water quality and observed membrane performance.

[0102] The nanofiltration unit 110 may include or be replaced by an ion exchange resin system to adsorb multivalent ions from the lithium-rich solution. The ion exchange resin may be a sulfonate, iminodiacetate, aminomethylphosphonic acid functionlised polystyrene / divinylbenzene resin. In an embodiment, the sulfonated resin may be a strong acid cation exchange resin.

[0103] The ion exchange resin may be packed in a column or a series of columns. The lithium-rich solution may be passed through the ion exchange resin column at a controlled flow rate. As the solution flows through the resin, multivalent ions such as Ca2+, Mg2+, and Al3+are selectively adsorbed by the resin, while allowing monovalent lithium ions to pass through.

[0104] The ion exchange process may be operated in a continuous or batch mode. In a continuous mode, multiple columns may be used in parallel, allowing for simultaneous adsorption and regeneration processes. The flow rate through the ion exchange columns may be adjusted based on factors such as the concentration of multivalent ions in the feed solution and the desired purification level.

[0105] After a certain period of operation or when the ion exchange capacity is exhausted, the resin may need to be regenerated. The regeneration process may be performed by flushing the resin with sulfuric acid or hydrochloric acid. The concentration of the sulfuric acid or hydrochloric used for regeneration may range from 1% to 10% by weight. The regeneration process may be carried out at ambient temperature or at elevated temperatures up to 60°C.

[0106] During regeneration, the sulfuric or hydrochloric displaces the adsorbed multivalent ions from the resin, restoring its ion exchange capacity. The displaced ions and excess acid may be collected as a waste stream, which may be further treated or disposed of according to environmental regulations.The regenerated ion exchange resin may then be rinsed with deionised water to remove any residual acid before being put back into service. This regeneration process may allow for multiple cycles of use, enhancing the efficiency and cost-effectiveness of the purification process.

[0107] In an embodiment, the ion exchange system may be used in combination with nanofiltration membranes. The ion exchange resin may serve as a pre-treatment step to remove the bulk of multivalent ions, followed by nanofiltration for final polishing of the lithium-rich solution. This combined approach may extend the life of the nanofiltration membranes and improve the overall efficiency of the multivalent ion removal process.

[0108] Following nanofiltration in the nanofiltration unit 110, the lithium chloride solution 20 may be subjected to reverse osmosis in a reverse osmosis unit 112 to further increase the concentration of lithium ions. The use of reverse osmosis on the lithium chloride solution 20 is intended to result a sufficiently high lithium concentration to allow for an efficient subsequent electrodialysis process. The reverse osmosis unit 112 may operate under various conditions to optimise the concentration of lithium ions in the lithium chloride solution 20. In some embodiments, the operating pressure of the reverse osmosis unit 112 may range from 20 bar to 300 bar. The operating pressure may range from 20 bar to 250 bar. The operating pressure may range from 20 bar to 200 bar. The operating pressure may range from 20 bar to 150 bar. The operating pressure may range from 20 bar to 100 bar. The operating pressure may range from 40 bar to 300 bar. The operating pressure may range from 60 bar to 300 bar. The operating pressure may range from 80 bar to 300 bar. The operating pressure may range from 100 bar to 300 bar. The operating pressure may range from 200 bar to 300 bar. The operating pressure may be at least 20 bar. The operating pressure may be at least 50 bar. The operating pressure may be at least 100 bar. The operating pressure may be at least 150 bar. The operating pressure may be at least 200 bar. The operating pressure may be at least 250 bar. The operating pressure may be up to 300 bar. The operating pressure may be up to 250 bar. The operating pressure may be up to 200 bar. The operating pressure may be up to 150 bar. The operating pressure may be up to 100 bar. In an embodiment, the operating pressure may be 60 bar. In an embodiment, the operating pressure may be 80 bar. The pressure may be adjusted based on factors such as the concentration of the feed solution, desired recovery rate, and membrane characteristics.

[0109] The temperature of the solution entering the reverse osmosis unit 112 may be maintained between 20°C and 45°C. In some embodiments, the temperature may be controlled to enhance membrane performance and prevent scaling.The conventional reverse osmosis process may be configured to increase the TDS concentration to at least 50 g / L. The TDS concentration may range from 50 g / L to 300 g / L. The TDS concentration may range from 50 g / L to 250 g / L. The TDS concentration may range from 50 g / L to 200 g / L. The TDS concentration may range from 50 g / L to 150 g / L. The TDS concentration may range from 50 g / L to 100 g / L. The TDS concentration may range from 100 g / L to 300 g / L. The TDS concentration may range from 150 g / L to 300 g / L. The TDS concentration may range from 200 g / L to 300 g / L. The TDS concentration may range from 250 g / L to 300 g / L. The TDS concentration may be at least 100 g / L. The TDS concentration may be at least 150 g / L. The TDS concentration may be at least 200 g / L. The TDS concentration may be at least 250 g / L. The TDS concentration may be at least 275 g / L. The TDS concentration may be up to 300 g / L. The TDS concentration may be up to 275 g / L. The TDS concentration may be up to 250 g / L. The TDS concentration may be up to 225 g / L. The TDS concentration may be up to 200 g / L. In an embodiment, the TDS concentration may be 200 g / L. In an embodiment, the TDS concentration may be 250 g / L. Following treatment in the reverse osmosis unit 112 a lithium concentration in the lithium chloride solution 20 may be at least 1000 ppm. Conventional reverse osmosis may be limited to about 80 bar, which corresponds to a lithium chloride concentration of about 60 g / L to 70 g / L.

[0110] The reverse osmosis unit 112 may employ high-rejection membranes specifically designed for lithium concentration. These membranes may have a nominal salt rejection rate of 99% or higher. In some embodiments, thin-film composite membranes may be used due to their high selectivity and durability. The flow rate through the reverse osmosis unit 112 may be adjusted to achieve the desired concentration factor. In some embodiments, the unit may operate with a recovery rate ranging from 50% to 90%, depending on the feed solution concentration and target lithium concentration.

[0111] The reverse osmosis unit 112 may incorporate a multi-stage configuration to achieve higher concentration factors. In some embodiments, a two-pass or three-pass system may be employed, with each pass further concentrating the lithium chloride solution 20. To minimise membrane fouling and scaling, the reverse osmosis unit 112 may include a pretreatment system. This system may involve the use of antiscalants, pH adjusters, or additional filtration steps to remove potential foulants from the feed solution.

[0112] The reverse osmosis unit 112 may operate in a continuous mode, with provisions for periodic membrane cleaning and maintenance. In some embodiments, clean-in-place (CIP) systems may be integrated to allow for regular membrane cleaning without disassembly of the unit.Monitoring and control systems may be incorporated in the reverse osmosis unit 112 to continuously track parameters such as pressure, flow rate, conductivity, and pH. These systems may allow for real-time adjustments to optimise performance and ensure consistent product quality.

[0113] In the embodiment shown in Figure 2, the reverse osmosis unit 112 is positioned downstream of the nanofiltration unit 110. However, different arrangements of the nanofiltration unit 110 and the reverse osmosis unit 112 can be used, as is described with reference to Figure 3 and Figure 4.

[0114] Figure 3 illustrates a system 100a for processing a lithium chloride solution 20. The system 100a is a variant of the system 100 described earlier, and like references are used to describe like features. The system 100a comprises the nanofiltration unit 110, the reverse osmosis unit 112, and the electrodialysis unit 114. In this configuration, the nanofiltration unit 110 and the reverse osmosis unit 112 are arranged in a parallel configuration, allowing for iterative processing and concentration of the lithium chloride solution 20.

[0115] In system 100a, the lithium chloride solution 20 enters the nanofiltration unit 110. The nanofiltration unit 110 processes the lithium chloride solution 20 and produces a waste water stream and a primary flow 126. The primary flow 126 is directed towards the electrodialysis unit 114. A branched flow 128 extends from the primary flow 126 and carries a portion of the solution from the nanofiltration unit 110 to the reverse osmosis unit 112. The reverse osmosis unit 112 further concentrates the solution, and a return flow 130 allows for the return of the concentrated solution from the reverse osmosis unit 112 back to the primary flow 126. This bidirectional, parallel flow between the nanofiltration unit 110 and the reverse osmosis unit 112 allows for iterative processing and concentration of the solution.

[0116] The arrangement of the reverse osmosis unit 112 relative to the nanofiltration unit 110 using the branched flow 128 and return flow 130 may provide several advantages. In some embodiments, this configuration may allow for more flexible control over the concentration process. The branched flow 128 may be adjusted to divert a larger or smaller portion of the solution to the reverse osmosis unit 112 based on the desired final concentration or the current composition of the solution.

[0117] The combined primary flow 126, which includes the return flow 130 from the reverse osmosis unit 112, is then directed to the electrodialysis unit 114 for further processing.Figure 4 illustrates a system 100b for processing a lithium-containing solution. The system 100b is a variant of system 100 and 100a and like references are used to describe like features. In system 100b, the sorbent unit 18 receives input from the osmotically assisted reverse osmosis unit 16. The nanofiltration unit 110 receives the output from the sorbent unit 18 and produces a waste water output 100b and a flow directed towards the reverse osmosis unit 112. The waste water output may contain impurities removed during the nanofiltration process. The reverse osmosis unit 112 is located downstream of the nanofiltration unit 110 and is connected to the sorbent unit 18 by a return flow 132. This configuration allows a purified and concentrated lithium chloride solution to be returned to the sorbent unit 18 for further processing.

[0118] The flow of solution through the sorbent unit 18, nanofiltration unit 110 and reverse osmosis unit 112 operates in a cyclic manner, with the nanofiltration unit 110 and reverse osmosis unit 112 working together to process the solution to remove multivalent ions and increase salinity, respectively, which is then treated by the sorbent unit 18. The return flow 132 may allow for more efficient use of the sorbent material by exposing it to a more concentrated lithium solution. In some embodiments, this configuration may improve the overall lithium recovery rate of the system. The sorbent unit 18 feeds back into the nanofiltration unit 110, creating a closed loop. The cyclic nature of this configuration may offer advantages in terms of process control and optimisation. By allowing multiple passes through the sorbent unit 18, nanofiltration unit 110, and reverse osmosis unit 112, the system may be able to achieve higher purity and concentration levels for the lithium chloride solution 20. The lithium chloride solution 20 represents the end product of this process.

[0119] Now referring back to Figure 2, following processing in the nanofiltration unit 110 and / or reverse osmosis unit 112, the purified and / or concentration lithium chloride solution 21 may then be directed to an electrodialysis unit 114. The electrodialysis unit 114 converts the concentrated lithium chloride solution 21 to lithium hydroxide 116 and hydrochloric acid 118. The electrodialysis unit 114 may use a bipolar membrane electrodialysis cell. The lithium hydroxide 116 produced by the electrodialysis unit 114 may have various properties that make it suitable for further processing or use in industrial applications. For example, in some embodiments, the lithium hydroxide 116 may be used directly in battery manufacturing processes or other industrial applications that require high-purity lithium hydroxide. The lithium hydroxide 116 may have a purity of at least 95%, 98%, 99%, 99.5%, 99.9%, 99.95% or 99.99%. The lithium hydroxide 116 may be further processed to produce lithium hydroxide monohydrate crystals. This crystallisation process may involve evaporation, cooling, or a combination of both.The hydrochloric acid 118 produced by the electrodialysis unit 114 may be recycled back to the neutraliser 14. The recycling of hydrochloric acid 118 produced by the electrodialysis unit 114 back to the neutraliser 14 may reduce the need for fresh acid input, potentially lowering raw material costs and minimising waste generation, contributing to a more environmentally friendly operation with a smaller chemical footprint.

[0120] In system 100, the waste brine 28 may be subjected to electrodialysis in an electrodialysis unit 120 to generate sodium hydroxide 124 and hydrochloric acid 122. The sodium hydroxide 124 generated by the electrodialysis unit 120 may be recycled for use in the spodumene leaching 108. Similarly, the hydrochloric acid 122 may be used in the neutraliser 14, creating a closed-loop system that may help to minimise waste and improve efficiency.

[0121] The use of osmotically assisted reverse osmosis in combination with selective lithium adsorption may allow for efficient concentration and extraction of lithium ions from leach solutions. The multi-stage osmotically assisted reverse osmosis configuration may enable progressive concentration of lithium, while the waste brine recirculation system helps reduce energy requirements by utilising the waste brine as a draw solution. The waste brine recirculation may be configured to direct at least a portion of the waste brine to a regeneration unit for sodium hydroxide and / or hydrochloric acid recovery. This feature may reduce chemical consumption and waste generation, contributing to the overall sustainability of the process. Further, by utilizing waste brine as a draw solution and incorporating reagent recovery systems, one or more embodiments of the process and / or system may minimise waste generation and reduce the consumption of fresh chemicals.

[0122] In the claims that follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the disclosure.

[0123] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

[0124] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present disclosure.

Claims

Claims1. A process for extracting lithium ions, comprising:providing a lithium-rich leachate formed from leaching a lithium-containing mineral with an alkaline substance or solution;reducing a pH of the lithium-rich leachate with an acid to form a lithium- containing solution;subjecting the lithium-containing solution to osmotically assisted reverse osmosis (OARO) to increase a concentration of lithium ions and overall salinity forming a concentrated lithium-containing solution;contacting the concentrated lithium-containing solution with a lithium-selective sorbent to extract lithium ions from the lithium-containing solution to form a lithium- depleted waste brine;using the waste brine from the sorbent as a draw solution in the osmotically assisted reverse osmosis; anddesorbing the extracted lithium ions from the lithium-selective sorbent to form a lithium ion-containing solution.

2. The process of any one of claims 1, wherein the lithium-containing mineral comprises spodumene.

3. The process of any one of claims 1 to 2, wherein the alkaline solution comprises sodium hydroxide and / or calcium hydroxide / oxide.

4. The process of any one of claims 1 to 3, wherein the acid used to reduce the pH of the lithium-rich leachate comprises hydrochloric acid or sulfuric acid.

5. The process of any one of claims 1 to 4, wherein the osmotically assisted reverse osmosis is performed using a semi-permeable membrane at a pressure up to 20 bar.

6. The process of any one of claims 1 to 5, wherein the lithium-selective sorbent comprises an ion exchange resin and / or a material that can intercalate lithium ions.

7. The process of any one of claims 1 to 6, further comprising subjecting the waste brine to electrodialysis to generate sodium hydroxide and hydrochloric acid after use as the draw solution.

8. The process of any one of claims 1 to 7, wherein desorbing the extracted lithium ions includes using an eluent solution.

9. The process of any one of claims 1 to 8, further comprising adjusting the pH of the lithium-containing solution prior to the osmotically-assisted reverse osmosis.

10. The process of any one of claims 1 to 9, wherein a concentration of lithium ions in the concentrated lithium-containing solution resulting from a feed side of the OARO process is higher than a concentration in the lithium-containing solution.

11. The process of any one of claims 1 to 10, wherein a concentration of lithium ions in the concentrated lithium-containing solution before contacting with the lithiumselective sorbent is at least 400 ppm, and a concentration of lithium ions in the waste brine after contacting with the lithium-selective sorbent is up to 80 ppm.

12. The process of any one of claims 1 to 11, wherein the waste brine resulting from an end stage of a draw side of the OARO has a lower osmotic pressure than the lithium- containing solution.

13. The process of any one of claims 1 to 12, further comprising subjecting the lithium ioncontaining solution to nanofiltration to remove multivalent ions.

14. The process of claim 13, wherein the nanofiltration is performed at a pressure ranging from 5 bar to 20 bar.

15. The process of claim 13 or 14, wherein the nanofiltration removes ions including Ca2+, Mg2+, Fe3+, Mn2+, Mn3+, Mn4+, and Al3+.

16. The process of any one of claims 1 to 15, further comprising subjecting the lithium ioncontaining solution to reverse osmosis to increase a concentration of lithium ions.

17. The process of any one of claims 1 to 16, wherein the reverse osmosis increases the concentration of lithium ions to at least 1000 ppm.

18. The process of any one of claims 1 to 17, further comprising subjecting the lithium ioncontaining solution to electrodialysis to form lithium hydroxide and hydrochloric acid.

19. The process of claim 18, wherein the electrodialysis is performed using a bipolar membrane electrodialysis cell.

20. The process of claim 18 or 19, wherein the lithium hydroxide formed by the electrodialysis has a purity of at least 95%.

21. The process of any one of claims 1 to 20, wherein subjecting the lithium-containing solution to osmotically assisted reverse osmosis comprises using multiple stages of osmotically assisted reverse osmosis.

22. The process of claim 21, wherein the multiple stages of osmotically assisted reverse osmosis are arranged in series.

23. The process of claim 21 or 22, wherein the multiple stages of osmotically assisted reverse osmosis are configured to progressively increase the concentration of lithium ions in the lithium-containing solution.

24. The process of any one of claims 21 to 23, wherein the waste brine is used as a draw solution in at least one stage of the multiple stages of osmotically assisted reverse osmosis.

25. The process of any one of claims 21 to 24, wherein the multiple stages of osmotically assisted reverse osmosis comprise at least three stages.

26. The process of any one of claims 21 to 25, wherein the multiple stages of osmotically assisted reverse osmosis are operated at different pressures.

27. The process of any one of claims 1 to 26, further comprising recycling a portion of the concentrated lithium-containing solution from a later stage to an earlier stage of the multiple stages of osmotically assisted reverse osmosis.

28. A system for extracting lithium ions, comprising:a leaching unit configured to leach a lithium-containing mineral with an alkaline substance or solution to produce a lithium-rich leachate;a neutralisation unit configured to reduce a pH of the lithium-rich leachate with an acid to form a lithium-containing solution;an osmotically assisted reverse osmosis unit configured to subject the lithium- containing solution to osmotically assisted reverse osmosis to increase a concentration of lithium ions and overall brine salinity to form a concentrated lithium- containing solution;a sorbent unit comprising a lithium-selective sorbent configured to contact the concentrated lithium-containing solution to extract lithium ions and desorb the extracted lithium ions to produce a lithium ion-containing solution; anda brine recirculation system configured to use lithium-depleted brine from the sorbent unit as a draw solution in the osmotically assisted reverse osmosis unit.

29. The system of claim 28, wherein the lithium-containing material comprises a- spodumene.

30. The system of claim 28 or 29, wherein the alkaline solution comprises sodium hydroxide and / or calcium hydroxide / oxide.

31. The system of any one of claims 28 to 30, wherein the leaching unit is configured to operate at a temperature above 200°C.

32. The system of any one of claims 28 to 31 , further comprising a filtration unit configured to remove solid residues from the lithium-rich leachate.

33. The system of any one of claims 28 to 32, wherein the acid comprises hydrochloric acid and / or sulfuric acid.

34. The system of any one of claims 28 to 33, wherein the neutralisation unit is configured to adjust the pH of the lithium-rich leachate to a range of 5 to 9.

35. The system of any one of claims 28 to 34, wherein the neutralisation unit is configured to remove impurities precipitated from the lithium-containing solution.

36. The system of any one of claims 28 to 35, wherein the osmotically assisted reverse osmosis unit comprises a semi-permeable membrane.

37. The system of any one of claims 28 to 36, wherein the osmotically assisted reverse osmosis unit is configured to operate at a pressure up to 20 bar.

38. The system of any one of claims 28 to 37, wherein the osmotically assisted reverse osmosis unit comprises multiple stages arranged in series.

39. The system of any one of claims 28 to 38, wherein the multiple stages are configured to progressively increase the concentration of lithium ions in the lithium-containing solution.

40. The system of any one of claims 28 to 39, wherein the osmotically assisted reverse osmosis unit is configured to achieve a lithium concentration of at least 400 ppm in the concentrated lithium-containing solution.

41. The system of any one of claims 28 to 40, wherein the osmotically assisted reverse osmosis unit comprises a spiral-wound membrane module or hollow-fiber membrane module.

42. The system of any one of claims 28 to 41, wherein the sorbent unit comprises an ion exchange resin, a lithium aluminium layered double hydroxide sorbent, a lithium manganese oxide sorbent and / or a lithium titanium oxide sorbent.

43. The system of any one of claims 28 to 42, wherein the sorbent unit is configured to operate in a continuous flow mode.

44. The system of any one of claims 28 to 43, wherein the sorbent unit comprises multiple columns arranged in parallel to allow simultaneous adsorption and desorption processes.

45. The system of any one of claims 28 to 44, wherein the sorbent unit is configured to use a dilute lithium chloride stripping solution for desorption of lithium ions.

46. The system of claim 45, wherein the dilute lithium chloride solution has a concentration ranging from 50 ppm to 250 ppm.

47. The system of any one of claims 28 to 46, wherein the sorbent unit is configured to operate at a temperature between 40°C and 80°C during desorption.

48. The system of any one of claims 28 to 47, wherein the waste brine recirculation system comprises a pump configured to circulate the waste brine to the osmotically assisted reverse osmosis unit.

49. The system of any one of claims 28 to 48, wherein the brine recirculation system is configured to recycle at least a portion of the lithium-depleted brine which contains sodium hydroxide and / or calcium hydroxide / oxide to a regeneration unit for initial alkaline digestion of new lithium-containing mineral.

50. The system of any one of claims 28 to 49, further comprising a polishing unit configured to remove multivalent ions from the lithium-containing solution produced by the sorbent unit.

51. The system of claim 50, wherein the polishing unit comprises an ion exchange resin selective for multivalent ions.

52. The system of claim 50, wherein the polishing unit is configured to remove ions including Ca2+, Mg2+, Fe3+, Mn2+, Mn3+, Mn4+, and Al3+.

53. The system of any one of claims 28 to 52, further comprising a reverse osmosis unit configured to concentrate the lithium-containing solution produced by the sorbent unit.

54. The system of claim 53, wherein the reverse osmosis unit is configured to increase the concentration of lithium ions to at least 1000 ppm.

55. The system of any one of claims 28 to 54, further comprising a first electrodialysis unit configured to process the lithium-containing solution to produce lithium hydroxide and hydrochloric acid.

56. The system of claim 55, wherein the first electrodialysis unit is configured to produce lithium hydroxide with a purity of at least 95%.

57. The system of claim 55 or 56, wherein the first electrodialysis unit is configured to recycle the produced hydrochloric acid to the neutralisation unit.

58. The system of any one of claims 28 to 57, further comprising a second electrodialysis unit configured to process the lithium-depleted brine from a draw side of theosmotically assisted reverse osmosis unit to produce sodium hydroxide and hydrochloric acid.

59. The system of claim 58, wherein the second electrodialysis unit is configured to recycle the produced hydrochloric acid back to the neutralisation unit and / or recycle the sodium hydroxide to the leaching unit.

60. The system of any one of claims 55 to 59, wherein the first electrodialysis unit and / or second electrodialysis unit each comprise a bipolar membrane electrodialysis cell.

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