Apparatus, device, and method for selective lithium extraction and direct conversion to lithium hydroxide

Abstract

The present disclosure reports apparatus, devices, and methods for selectively extracting lithium from complex lithium-containing feed streams and converting it directly to lithium hydroxide. The apparatus, devices, and methods of the present disclosure utilize an ionomeric material that is amenable to forming into an anion exchange layer that is ultra-thin and having little capacity for ion retention. Despite its ultra-thin application, the anion exchange layer has sufficient permselectivity to facilitate water splitting when coupled with a permselective cation exchange layer, such that electrochemical interventions can modulate the alkalinity and / or pH environment in proximity to the cation exchange layer. The cation exchange layer comprises a sorbing agent that selectively binds and releases lithium ions under specific alkalinity and / or pH conditions. The low ion-retention properties of the ionomeric material attenuate challenges associated with the formation of lithium salt mixtures during direct lithium hydroxide production.

Description

APPARATUS, DEVICE, AND METHOD FOR SELECTIVE LITHIUM EXTRACTION AND DIRECT CONVERSION TO LITHIUM HYDROXIDERELATED APPLICATION

[0001] This application claims priority under applicable laws to United States provisional application No. 63 / 578,785 filed on August 25, 2023, the content of which is incorporated herein by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates to the field of selective lithium extraction and direct conversion to lithium hydroxide. More particularly, the present disclosure relates to bipolar membrane apparatuses, electrically regenerated ion exchange devices, and methods for selective lithium extraction from complex lithium-containing feed streams and conversion thereof to lithium hydroxide by a single-step process.BACKGROUND

[0003] Lithium is a strategic element with widespread applications in next generation technologies. Lithium and lithium compounds are used in the glass, enamel, and ceramic industry, lubricants, light-weight alloys, pharmaceutical products, and batteries. Global demand for lithium is rising exponentially due to the use of lithium-ion batteries in electric or hybrid vehicles, grid-scale energy storage, and portable electronic devices. Projections indicate that between 12 and 20 million metric tons of lithium production will be required to meet global demand through the year 2100.

[0004] Lithium is primarily found in three different types of deposits: (i) pegmatites (e.g., lepidolite, petalite, and / or spodumene); (ii) hydrothermally altered clays; and / or (iii) continental brines (e.g., salar, petrochemical, and / or geothermal brines). When processed for lithium production, all three deposit types produce complex lithium- containing feed streams. For example, their lithium contents can vary widely, the spectrum of other ions they can contain is diverse, and they are often mixed with exogenous chemicals. These complexities can make efficient lithium recovery a challenge - one that is often compounded by remote and / or harsh operating conditions, restrictions on water use, and / or strict regulatory requirements. Direct lithium extraction (DLE) technologies are being developed to selectively extract lithium from complex lithium-containing feed streams. DLE technologies typically produce dilute streams of lithium chloride that are concentrated and eventually converted to lithium carbonate through refining processes that are optimized to provide stable, transportable, and / or salable lithium carbonate material.

[0005] In the context of the applications listed above, lithium carbonate is often further converted to lithium hydroxide for additional processing. For example, in battery production, lithium carbonate is typically converted to lithium hydroxide that is then used in the production of cathode materials (e.g., lithium nickel manganese cobalt oxides (NMC) and lithium iron phosphate (LiFePCk or LFP)). This refining sequence has the potential to satisfy at least some of the current and future lithium demand, but it is inherently inefficient. Accordingly, there is an unmet need for the development of new apparatus, devices, and methods for selectively extracting lithium from complex lithium- containing feed streams and converting it directly to lithium hydroxide.SUMMARY

[0006] The present disclosure reports bipolar membrane apparatus, devices, and methods for selectively extracting lithium from complex lithium-containing feed streams and converting it directly to lithium hydroxide. The bipolar membrane apparatus, devices, and methods of the present disclosure utilize an ionomeric material that is amenable to forming an anion exchange layer that is ultra-thin and having little capacity for ion retention. Despite its capacity for ultra-thin application, the anion exchange layer can provide sufficient permselectivity to facilitate water splitting when coupled with a permselective cation exchange layer, such that electrochemical interventions can modulate the alkalinity and / or pH environment in proximity to the cation exchange layer. The cation exchange layer comprises a sorbing agent that selectively binds and releases lithium under specific alkalinity and / or pH conditions. Taken together, the ultra-thin anion exchange layer and the thicker cation exchange layer form an asymmetric bipolar membrane apparatus (asymmetric-BPMA) that can be deployed in electrochemical devices and methods for selectively extracting lithium from complex lithium-containing feed streams. The asymmetric-BPMAs of the present disclosure are well suited to direct conversion to lithium hydroxide, as the low ion-retention properties of the ionomeric material attenuate challenges associated with the formation of lithium salt mixtures (e.g., mixtures of lithium hydroxide with lithium chloride and / or lithium sulfate), which limit the applicability of conventional anion exchange materials in the present context. By wayof example, the present disclosure reports comparative results for an asymmetric-BPMA in accordance with the present disclosure versus a previously disclosed bipolar membrane apparatus (BPMA), wherein the asymmetric-BPMA of the present disclosure provides a lithium hydroxide product stream with lower anionic impurity concentrations. The comparative results also evidence the potential for a faster lithium desorption rate, improved desorption efficiency, a lower power requirement for desorption, and / or a lower effective current requirement for the asymmetric-BPMA of the present disclosure relative to the previously disclosed BPMA.

[0007] An aspect of the present disclosure relates to an asymmetric bipolar membrane apparatus for producing lithium hydroxide from a complex lithium-containing feed stream, the asymmetric bipolar membrane apparatus comprising: a cation exchange layer comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative values of the lithium ion binding coefficient and the hydrogen ion binding coefficient are alkalinity dependent or pH dependent; and an anion exchange layer comprising an ionomeric material; wherein the cation exchange layer and the anion exchange layer are coupled and configured for hydraulic communication, and wherein the cation exchange layer and the anion exchange layer are sufficiently permselective to facilitate electrochemical interventions that modulate the alkalinity or pH in proximity to the cation exchange layer.

[0008] Another aspect of the present disclosure relates to an electrically regenerated ion exchange (ERIX) device for producing lithium hydroxide from a complex lithium- containing feed stream, the ERIX device comprising: a flow path from an inlet of the ERIX device to an outlet of the ERIX device; a first electrode in proximity to the flow path; a second electrode in proximity to the flow path; andan asymmetric bipolar membrane apparatus within an electric field defined by the first electrode and the second electrode, wherein the asymmetric bipolar membrane apparatus comprises: a cation exchange layer comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an anion exchange layer comprising an ionomeric material; wherein the cation exchange layer and the anion exchange layer are coupled and configured for hydraulic communication, and wherein the cation exchange layer and the anion exchange layer are sufficiently permselective to facilitate electrochemical interventions that modulate the alkalinity or pH in proximity to the cation exchange layer in response to perturbations in the electric field.

[0009] Another aspect of the present disclosure relates to a method for producing lithium hydroxide from a complex lithium-containing feed stream, the method comprising: uptaking lithium ions from the complex lithium-containing feed stream into an asymmetric bipolar membrane apparatus by flowing the complex lithium- containing feed stream through the bipolar membrane apparatus and applying a forward bias across an electrode pair to induce an electric field within the bipolar membrane apparatus, wherein the bipolar membrane apparatus comprises: a cation exchange layer that is permselective and that comprises a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an anion exchange layer that is permselective and that comprises an ionomeric material;releasing lithium ions from the bipolar membrane apparatus to a lithium hydroxide stream by flowing an ion capture stream through the asymmetric bipolar membrane apparatus and applying a reverse bias across the electrode pair.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings and description provided herein, similar reference numerals may indicate similar components. For sake of simplicity and clarity, not all drawings contain references to all the components and features, and references to some components and features may be found in only one drawing. Components and features of the present disclosure which are illustrated in other drawings can be readily inferred therefrom.

[0011] Figure 1 shows a schematic cross-sectional representation of a two-layer asymmetric bipolar membrane apparatus (asymmetric-BPMA) in accordance with an embodiment of the present disclosure. The asymmetric-BPMA comprises a cation exchange layer (CEL) and an ionomeric anion exchange layer (AEL).

[0012] Figure 2 shows a schematic cross-sectional representation of a modified asymmetric-BPMA in accordance with an embodiment of the present disclosure. The modified asymmetric-BPMA has three layers: a CEL, an ionomeric AEL, and a secondary CEL. The secondary CEL is selective for monovalent ions.

[0013] Figure 3 shows a schematic cross-sectional representation of a modified asymmetric-BPMA in accordance with an embodiment of the present disclosure. The modified asymmetric-BPMA has four layers: an ionomeric AEL, a secondary CEL, a secondary AEL, and a CEL assembled in accordance with the present disclosure. The secondary CEL is selective for monovalent ions.

[0014] Figure 4A shows a schematic cross-sectional representation of an asymmetric-BMPA in accordance with an embodiment of the present disclosure. Figure 4B and Figure 4C show expansions of specific components of the asymmetric-BMPA.

[0015] Figure 5A shows a flow diagram of an electrically regenerated ion exchange (ERIX) device set in a forward bias configuration, as used during an adsorption cycle, with a plurality of asymmetric-BMPAs. Figure 5B shows the chemistry and ionic flow diagram for a single asymmetric-BMPA, as used during an adsorption cycle.

[0016] Figure 6A shows a flow diagram of an ERIX device set in a reverse bias configuration, as used during a desorption cycle, with a plurality of asymmetric-BMPAs. Figure 6B shows the chemistry and ionic flow diagram for a single asymmetric-BMPA, as used during a desorption cycle.

[0017] Figure 7A shows membrane exchange capacities of specific ion concentrations, as determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) measurements, over time for an ERIX device featuring an asymmetric-BMPA in accordance with an embodiment of the present disclosure. Figure 7B shows an expansion of an absorption and desorption cycle.

[0018] Figure 8A and Figure 8B show membrane exchange capacities of specific ion concentrations, as determined by ICP-OES measurements, over time for an ERIX device featuring an asymmetric-BMPA in accordance with an embodiment of the present disclosure versus a previously disclosed ERIX device.

[0019] Figure 9 shows repeated use cycles of an ERIX device featuring an asymmetric- BMPA in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION

[0020] The following detailed description and examples are illustrative and should not be interpreted as further limiting the scope of the present disclosure. On the contrary, it is intended to cover all alternatives, modifications, and equivalents that can be included as described by the present description. Objects, advantages, and other features of the apparatus, devices, and methods will be more apparent and better understood by those skilled in the art upon reading the following non-restrictive description and references made to the accompanying drawings.

[0021] Membranes are a form factor used in ion exchange technologies to capture and release target ions under specific electrochemical conditions. Ion exchange may rely on the use of bipolar membranes to facilitate the passage or repulsion of specific ions. This process of ion capture, commonly referred to as "adsorption” or "uptake”, may be achieved by chemical association to a specific component within the membrane. The release of target ions, commonly referred to as "desorption” can be achieved chemically, through the addition of specific chemicals in solution such as acids or bases.

[0022] The term "bipolar membrane apparatus” (BPMA) is used throughout the present disclosure to refer to combinations of at least two individual membranes of opposing charge density and / or polarity, which may be used to facilitate ion exchange. Those skilled in the art who have benefited from the teachings of the present disclosure will appreciate that the selection of material for each membrane may vary as required, according to use case or intended application. The term "polarity” is defined within the present disclosure as the charge of a material, e.g., negative, positive, partially negative, and / or partially positive. A conventionally designed BPMA combines: a cation exchange layer (CEL) generally made of an electronically neutral substrate with fixed negatively charged groups (such as sulfonate, carbonate, and / or phosphate groups), which facilitate the passage of cations through the membrane while inhibiting anionic product crossover; an anion exchange layer (AEL) is generally made of an electronically neutral substrate with fixed positively charged groups (such as sulfonium, phosphonium, and / or quaternary ammonium groups), which facilitate the passage of anions through the membrane while inhibiting cationic product crossover; and an interface region (also called "interfacial layer” or "bipolar junction”) in which the CEL and AEL are in contact.

[0023] In the context of the present disclosure, the terms "permselective” and "permselectivity” relate to a material’s ability to limit ion migration from dissipating current across a membrane barrier and / or a material’s ability to maintain an electric potential across a membrane barrier (such as between layers in a BPMA). Inclusion of inorganic sorbent materials, as with those selective to adsorbing lithium outlined within the present disclosure, within a membrane may provide for suitable permselectivity. In contrast, pure inorganic sorbent materials (e.g., metal oxide complexes) may not provide sufficient permselectivity and / or may inhibit the performance of the electrically regenerated ion exchange (ERIX) device by increasing resistance and overall power requirements. Those skilled in the art who have benefited from the teachings of the present disclosure will appreciate that materials and / or experimental parameters (e.g., binder compositions and swelling temperature) may impact, permselectivity, resistance, and power requirements.

[0024] In the context of the present disclosure, the CEL and the AEL may be referred to with "organic” or "inorganic” prefixes to indicate their chemical composition. Various types of organic and inorganic ion exchange functionalities are known to those skilled in the art, such as those described in the PCT patent application published under number WO 2022 / 236415 Al, the contents of which is herein incorporated by reference.

[0025] The use of BPMA in ERIX devices is commonly deployed for purification applications such as water treatment, chemical recovery, and / or aqueous extraction processes. In general, application of electrical current to ERIX devices can drive water splitting as a means for in-situ production of protons and hydroxide ions. The term "water splitting” is defined within the present disclosure as the separation of water into its constituent ions, hydrogen ions (H+) and hydroxide ions (OH-). Those skilled in the art will appreciate that the terms "hydrogen ions” and "hydroxide ions” have a variety of synonyms, which may be used interchangeably in the present disclosure (e.g., "protons”). In the context of the present disclosure, water splitting may occur by electrolytic reactions and / or chemical reactions. By modifying the individual properties of the membrane layers, a BPMA may be configured to recover or exclude specific ions. In the case of direct lithium extraction (DLE), for example, a BPMA may be used to adsorb lithium ions from a complex lithium-containing feed solution (e.g., dilute brines, concentrated salt process streams, and / or leachates). Lithium ions can then be desorbed to obtain a purified lithium solution wherein the lithium concentration may vary, depending on the process. Those skilled in the art will appreciate that the lithium may also be recovered under different forms (e.g., colloidal form, paired with an available ion, chelated, etc.). A purified lithium solution generated from a DLE process will often comprise a dilute salt solution (e.g., an aqueous stream containing lithium chloride, lithium sulfate, lithium carbonate, or a mixture of at least two thereof), commonly referred to as an "eluate”. The application of electrical current to facilitate water splitting allows for the regeneration of the membranes. In other words, the application of electrical current to facilitate water splitting allows for the membranes to return them to their original state. Following the above example: where lithium ions have displaced cations in the CEL during adsorption cycles, water splitting may generate new hydrogen ions in concentrations sufficient to displace lithium ions during desorption cycles. Used in this manner, ERIX devices may allow for continuous, selective capture of desirable chemical species from a complex mixture of chemical species, and control of theadsorptive and desorptive capabilities by manipulation of the electrical components of the device.

[0026] Previously disclosed ERIX devices have shown that BPMA may be configured for selective lithium extraction from a complex lithium-containing feed stream - specifically, to produce a lithium eluate (e.g., a dilute solution containing lithium chloride, lithium sulfate, lithium carbonate, or a combination thereof). These eluates tend to require additional processes (e.g., chemical transformation, and / or purification) before a salable material is obtained.

[0027] Within the context of the present disclosure, an alternative ERIX device configuration is proposed for direct lithium hydroxide production. The ERIX devices of the present disclosure utilize an asymmetric bipolar membrane apparatus (asymmetric- BMPA) in pursuit of: (i) improved efficiency; (ii) improved product purity; and / or (iii) broader tolerance to complex feed streams. In the asymmetric-BPMA of the present disclosure, the use of an ionomeric material comprising a homogenous polymer with evenly distributed charges in place of conventional AEL may allow for a substantially thinner application. As those skilled in the art who have benefited from the teachings of the present disclosure will appreciate, the significant reduction in the size of a membrane layer may substantially reduce energy requirements in ERIX devices. In the specific case of the asymmetric-BMPA of the present disclosure, the thickness of the ionomeric AEL may be about one sixth that of a conventional AEL, while still providing sufficient permselectivity for effective device function. At the same time, the ionomeric AEL may allow facile hydroxide ions migration while greatly reducing propensity for other anion retention, as the uniform ionomer structure and thin application reduces inclusion spaces (e.g., pores, and / or channels) where disadvantageous ions (e.g., chloride, and sulfate ions) may be physisorbed during adsorption cycles, and not retained to any significant degree by chemisorption (relative to total physisorption). In the context of the present disclosure, the term "physisorbed” refers to weak bonding associations such as dipole- induced attraction, hydrogen bonding, and / or Van der Waals attractions. In the context of the present disclosure, the term "chemisorbed” or "chemisorption” refers to strong bonding that may result from the formation of distinct chemical bonds between ions and the membranes. In the context of the present disclosure, the use of ionomeric materials may lead to decreased anion retention, which may provide a higher purity product stream during ERIX desorption cycles. In this way, the asymmetric-BPMA of the presentdisclosure utilize the unique properties of ionomeric AEL to efficiently and directly produce lithium hydroxide.

[0028] An aspect of the present disclosure relates to an asymmetric-BPMA for producing lithium hydroxide from a complex lithium-containing feed stream, the asymmetric-BPMA comprising: a CEL comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative values of the lithium ion binding coefficient and the hydrogen ion binding coefficient are alkalinity dependent or pH dependent; and an AEL comprising an ionomeric material; wherein the CEL and the AEL are coupled and configured for hydraulic communication, and wherein the CEL and the AEL are sufficiently permselective to facilitate electrochemical interventions that modulate the alkalinity or pH in proximity to the CEL.

[0029] In the context of the present disclosure, the term "proximity” is used to describe the relative distance between the CEL and AEL within a singular asymmetric-BPMA, as well as the relative distance of specific chemical species within one layer relative to the second layer (e.g., a description of distance between hydroxide anions within the AEL and the boundary to the CEL). As those skilled in the art will appreciate, bipolar membrane functionality is defined by designs minimizing any space (including, but not limited to: cavities, vacuoles, channels, pores, or any combination thereof). If contact between the layers is reduced in any way, the efficiency of water splitting will be negatively impacted. In such devices where there is no direct contact between both AEL and CEL, water splitting may not be used to generate ions within the membrane, and exogenous chemicals may be used instead.

[0030] In an embodiment of the present disclosure, the CEL is configured such that: (i) lithium ions may be replaced by hydrogen ions; (ii) the inorganic substrate has substantial binding capacity for lithium ions; (iii) the inorganic material is stable between the minimum and maximum pH values reached during ERIX device operation; and (iv) the CEL can be processed into sheets (e.g., less than approximately 0.5 mm thick, asdetermined by scanning electron microscopy (SEM) or using a micrometer) to provide higher device membrane surface area per device volume.

[0031] In an embodiment of the present disclosure, the AEL comprises an unmodified anionic ionomer material. The anionic ionomer material may be selected as required for its specific use case. For example, in devices where durability and robustness are desirable, such that the asymmetric-BPMA may tolerate a wider range of complex feed solutions, the anionic ionomer material should support a wide range of pH (e.g., Aemion*™). In alternative applications where pH sensitivity is of less concern, anionic ionomer materials with less broad applicability may be selected (e.g., Fumasep™ FAPQ- 375, pH range 0-10; Neosepta™ ACN, pH range 0-8).

[0032] In an embodiment of the present disclosure, the AEL is a pre-fabricated or a commercial ionomer sheet that may be assembled into an asymmetrical-BPMA directly. Specific consideration must be given to the AEL thickness. Increasing the thickness of the AEL decreases the chance of wearing and degradation over time, though this improvement will also provide a larger bulk material for physisorption of disadvantageous anions.

[0033] In an embodiment of the present disclosure, the AEL is prepared from its composite materials by ink formulation.

[0034] In an embodiment of the present disclosure, the AEL has a thickness that is about 15% of that of the CEL. In another embodiment of the present disclosure, the AEL can have a thickness in the range of from about 10 pm to about 100 pm, as determined by SEM or using a micrometer. For example, the AEL can have a thickness in the range of from about 10 pm to about 90 pm, or from about 10 pm to about 80 pm, or from about 10 pm to about 70 pm, or from about 10 pm to about 60 pm, or from about 10 pm to about 50 pm, or from about 10 pm to about 40 pm, or from about 10 pm to about 30 pm, or from about 10 pm to about 20 pm, or from about 20 pm to about 90 pm, or from about 30 pm to about 80 pm, or from about 40 pm to about 80 pm, or from about 50 pm to about 80 pm, or from about 60 pm to about 80 pm. In some embodiments, the AEL has a thickness in the range of from about 60 pm to about 80 pm. In some other embodiments, the AEL has a thickness in the range of from about 10 pm to about 40 pm. Those skilled in the art will appreciate that thinner membranes may require direct fabrication at time of use, by a methodology that is amenable to producing extremely thin films (e.g., inkformulation). A thinner ionomeric AEL may allow for a reduction in disadvantageous anion retention by presenting less overall bulk material in which said disadvantageous anions may be physisorbed.

[0035] In an embodiment of the present disclosure, the CEL may include a polymer binder. The polymer binder may be any material having the necessary properties for membrane fabrication and use. A material’s ability to maintain cohesion or contact between the ion exchange layers, while in the presence of brine or water, without substantial delamination, degradation, and / or dissolution during a process run may be useful with respect to selection criteria. pH tolerance may also be a useful selection criterion, with preference for materials able to tolerate a wide range of pH (between 1 and 14) during normal operation. A preferred method of preparing the asymmetric- BPMAs of the present disclosure is to select a melt processible (i.e., application of heat at temperatures between about 30 °C and about 80 °C to form a flowable fluid followed by cooling to form a solid and / or rigid material) polymer with a chemically stable backbone. Any compatible melt processible polymer is contemplated. Non-limiting examples of melt processible polymers include saturated polyolefins such as polypropylene (PP) and polyethylene (PE), unsaturated polyolefins, such as polystyrene (PS), polyvinyl difluoride (PVDF), and copolymers thereof. Those skilled in the art will recognize that other polymers and / or fabrication methods may be suitable for example casting from solvents, or direct synthesis of organic ion exchange membranes with subsequent chemical functionalization.

[0036] In an embodiment of the present disclosure, the CEL comprises a sorbing agent, including but not limited to, an inorganic metal oxide, a crown ether, a metalorganic framework (MOF), or a combination thereof.

[0037] The binding coefficient of a target ion and / or hydrogen refers to its ability to bind to a sorbing agent. The binding coefficient associated with a target ion and sorbing agent or hydrogen and sorbing agent depends on a number of factors, including but not limited to, the chemical structure of the sorbing agent, functional molecules attached to the sorbing agent, the current density applied to the sorbing agent and / or the target ion or hydrogen, the material of the sorbing agent, the concentration of the solution containing the target ion and / or hydrogen, the pore size of the sorbing agent for binding the target ion, the type and characteristics of the target ion, and a combination thereof.The binding coefficient may be a physical and / or chemical property of the sorbing agent specific to a target ion. A sorbing agent may have binding coefficients for each type of target ion (e.g., lithium ions, cobalt ions, nickel ions, aluminum ions, etc.) it binds to.

[0038] In the context of the present disclosure, having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the lithium ion binding coefficient is less than or equal to the hydrogen ion binding coefficient may facilitate elution of lithium ions via a regeneration reaction such as shown in Rxn. 4.

[0039] In the context of the present disclosure, the term "coupled” may be used to describe two objects that are physically, chemically, and / or electromagnetically connected. Ideally, the CEL and AEL are coupled in the asymmetric-BPMA, such that there is continuous contact, no cavities or occlusions, and / or reliable hydraulic communication between the two layers. In the context of the present disclosure, the term "hydraulic communication” refers to the migration and / or movement of fluid from a first layer to a second layer - either directly or indirectly.

[0040] In an embodiment of the present disclosure, the AEL may be coupled to the CEL by casting. In an embodiment of the present disclosure, the AEL may be coupled to the CEL by additional means, such as spray coating, spin coating, or drop casting. Those skilled in the art who have benefited from the teachings of the present disclosure will appreciate that the means by which the AEL and CEL are coupled may be more effective in specific use cases. For example, spin coating may produce a homogenous AEL layer but at high loss of material, which may be effective at the laboratory-scale but is often unattainable during prototyping and pilot design.

[0041] In the context of the present disclosure, the lithium hydroxide produced may be in solution form, in suspension form, in colloidal suspension form, in slurry form, in precipitated form, or other dispersion forms. In an embodiment of the present disclosure, the lithium hydroxide produced is a dilute aqueous stream containing at least about 100 ppm lithium hydroxide in water, at least about 500 ppm lithium hydroxide in water, or at least about 750 ppm lithium hydroxide in water. Those skilled in the art will appreciate that, dilute aqueous solutions containing lithium hydroxide may undergo conversion to lithium carbonates (e.g., lithium bicarbonate, and / or lithium carbonate) in the presence of dissolved carbon dioxide.

[0042] An aspect of the present disclosure relates to an ERIX device for producing lithium hydroxide from a complex lithium-containing feed stream, the ERIX device comprising: a flow path from an inlet of the ERIX device to an outlet of the ERIX device; a first electrode in proximity to the flow path; a second electrode in proximity to the flow path; and an asymmetric-BPMA within an electric field defined by the first electrode and the second electrode, wherein the asymmetric-BPMA comprises: a CEL comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an AEL comprising an ionomeric material; wherein the CEL and the AEL are coupled and configured for hydraulic communication, and wherein the CEL and the AEL are sufficiently permselective to facilitate electrochemical interventions that modulate the alkalinity or pH in proximity to the CEL in response to perturbations in the electric field.

[0043] In the context of the present disclosure, the electric field may be controlled by (i) current control, and / or (ii) voltage control. In the case of current control, the polarity of the ERIX device is reversed from adsorption to desorption cycles. Without being bound to any particular theory, the current used in each cycle is dependent on the chemistry occurring within the asymmetrical-BPMA (e.g., mass transport to the interface) and the total change in current required to operate the device will result from the combinatory effect of all active chemistries, and the rate at which the equilibria involved may change. Such changes may lead to a relative change in resistance across the device, which may require operational adjustment to the applied device current to continue operation. For example, the initial desorption operation begins at low resistance, but increases over time. The rate at which lithium ions are replaced with hydrogen ions may change, resulting in less productive water splitting and a need to increase current to maintain lithium desorption. Alternatively, by using voltage control, an ERIX device may beoperated in such a way as to avoid water splitting by maintaining a voltage less than the critical value required (e.g., less than approximately 3 V). While this is undesirable for use in the adsorption and desorption cycles described above, it may be used in alternative applications (e.g., electrodialysis).

[0044] In an embodiment of the present disclosure, the ERIX device comprises two electrodes. The ERIX device may also comprise a plurality of electrodes.

[0045] In the context of the present disclosure, a dual electrode system was selected for technological demonstration, as a means of performing ERIX device testing in a simplified case. It should be clear to those skilled in the art that this is not the singular nor preferred implementation of the asymmetrical-BMPA ERIX device, and that variable electrode configuration may be designed for any ERIX device to support changes in application, including, but not limited to: changes in scale, or for improvements in efficiency (e.g., increase the overall rate of water splitting, to adjust individual voltages per individual asymmetrical-BPMA stack).

[0046] In an embodiment of the present disclosure, the first electrode and the second electrode are made of the same material (e.g., iridium oxide coated titanium, platinum coated titanium) such that the electrode polarity may be reversed, as required for alternating cycles of adsorption and desorption, while maintaining the same effectivity of each electrode regardless of the cycle. Those skilled in the art will appreciate that certain functionality may be better enhanced with variable and non-matching electrode materials, and that there is no inherent requirement for matched materials to operate the ERIX devices within the present disclosure. Non-limiting examples of additional materials include stainless steel and nickel.

[0047] In an embodiment of the present disclosure, the electrodes are modified with nickel foam, for example, to increase the surface area of the electrodes. Those skilled in the art who have benefited from the teachings of the present disclosure will appreciate that increasing the surface area of the electrodes will increase water splitting.

[0048] In an embodiment of the present disclosure, the first electrode, relative to the ERIX device flow path inlet, may be modified with an alternative material specifically designed to promote hydrogen gas evolution. An increasing rate of hydrogen evolution may also result in an increasing rate of hydroxide ion generation, which may increase therate of adsorption of target ions in the CEL. Such a device may have increased power requirements, however, and may result in a loss of overall process efficiency.

[0049] In the context of the present disclosure, electrodes that are positioned "in proximity to” a flow path may be directly in the flow path, adjacent to the flow path, or acting on the flow path (with respect to their electric field) from a distance. Those skilled in the art who have benefited from the teachings of the present disclosure will understand how electric field parameters change as a function of distance and orientation. In an embodiment of the present disclosure, the first electrode is positioned in proximity to the inlet to the ERIX device. In an embodiment of the present disclosure, the second electrode is positioned in proximity to the outlet of the ERIX device. In an embodiment of the present disclosure, the electrodes are concentric. In an embodiment of the present disclosure, the electrodes are oriented in-line with the flow path. In an embodiment of the present disclosure, the electrodes are oriented irrespective of the flow path.

[0050] In an embodiment of the present disclosure, a complex lithium-containing feed stream may be a synthetic brine (e.g., an aqueous mixture of salts such as sodium sulfate, lithium sulfate, potassium sulfate, sodium chloride, potassium chloride, lithium chloride, or any combination thereof), or a natural salar brine.

[0051] In an embodiment of the present disclosure, the flow path is linear and staggered, such that the complex lithium-containing feed solution traverses from the inlet to the outlet of the ERIX device, and the passage between membranes alternates from one side of the device to the other. Additional embodiments include flow paths that are non-linear, concentric, and / or spiral.

[0052] In an embodiment of the present disclosure, the total flow path through the ERIX device may be recirculated, such that the processed complex lithium-containing feed solution is captured and transferred to the device inlet for further processing. In these cases, the complex lithium-containing feed solution may be processed as many times as required to continually capture target ions while continually removing impurities. For example, the complex lithium-containing feed solution may be processed 5 times, 10 times, or 20 times.

[0053] In an embodiment of the present disclosure, the inlet and outlet of the ERIX device are configured such that the complex lithium-containing feed solution may be introduced without restriction.

[0054] In an embodiment of the present disclosure, the inlet and outlet of the ERIX device are configured such that any gas produced during water splitting (e.g., hydrogen gas, and / or oxygen gas) may be allowed to diffuse out of the system before contact with the first asymmetric-BPMA.

[0055] Without being bound to any particular theory, when sufficient voltage is applied to the ERIX device comprising an asymmetric-BMPA within the present disclosure, and that ERIX device contains a mixed ion solution, water splitting, and concurrent ion migration may occur. Depending on the current directionality, this process may occur in two ways. Water splitting may occur under "forward bias”, wherein the cathode is proximal to the first AEL and the anode is proximal to the final CEL. Under forward bias, water may be split at the electrode surface while salt species may move into the membranes. Alternatively, water splitting may occur under "reverse bias”, wherein the anode is proximal to the AEL, and the cathode is proximal to the CEL, and water is split along the interface surface between the membranes. During the adsorption phase in an ERIX device comprising an asymmetric-BMPA, water splitting may occur (in part) at the first electrode (e.g., relative to the device flow path), generating hydroxide ions (0H_w.s) and hydrogen gas. Transition of hydroxide ions into the CEL may allow them to interact directly with the sorbing agent. For example, in the case of specific lithium metatitanate species within the CEM, migration of hydroxide ions resultant of water splitting may allow for the proton in titanate to be removed, due to the high binding force between hydroxide and hydrogen atoms under the local pH and / or alkalinity conditions. Concurrently, lithium ions in mixed brine solution may be drawn across the CEL and complex with the titanate which, after nearby accumulation of hydroxide ions, may have available binding sites previously occupied by hydrogen ions. This process is described below in Rxn. 1. Those skilled in the art who have benefited from the teachings of the present disclosure will appreciate that, while the examples shown are specific to one titanate species, similar reactivity is to be expected for similar titanates including H2TiO3. While the individual mechanisms may differ, the process by which a basic or alkaline species abstracts a hydrogen ion may be similar. These specific mechanisms have been omitted for brevity and clarity. The process by which in-membrane water splitting occurs togenerate the hydrogen ions necessary to displace lithium ions may be the same in each of the specific titanate cases.Adsorption:

[0056] Rxn. 3 describes the capture of a lithium ion during adsorption using titanic acid as the CEM sorbing agent.

[0057] Once adsorption is complete, the polarity of the electrodes may be reversed to regenerate the sorbing agent and release lithium ions back into solution. Water splitting at the membrane interface generates the necessary excess hydrogen ions to displace lithium ions (Rxn. 4) as well as the desired hydroxide ions to form lithium hydroxide (Rxn. 5).

[0058] In an embodiment of the present disclosure, the adsorption phase is influenced by the generation of hydroxide ions via water splitting.

[0059] In an embodiment of the present disclosure, the adsorption phase is influenced by the alkalinity of the complex lithium-containing feed stream (e.g., high concentration of sodium bicarbonate). In this case, with a pH approximately equal to 6.5, and no active water splitting occurring during the adsorption phase (that is, no current applied to the system), the bicarbonate may be sufficiently alkaline to deprotonate the titanate species.

[0060] In cases where the mixed brine contains higher ion concentrations, the ERIX device may become overwhelmed due to bulk salt intrusion into the asymmetric-BMPA. At this point, resistivity will drop, and when it becomes too low there may not be sufficientvoltage to allow water splitting during desorption. Lacking the ability to perform water splitting within the asymmetric-BMPA, the first electrode may be utilized to produce hydroxide ions via cathode electrolysis at the ERIX device inlet. This process is outlined in Rxn. 4.

[0061] In an embodiment of the present disclosure, the desorption stage is executed with an ion capture fluid flush. In this case, the ERIX device is optimized through the use of the asymmetric-BMPA ionomeric AEL layer. The thinner layer design and reduction feed material ions significantly decrease the time and volume required to flush the asymmetric-BMPA with an ion capture stream. Similarly, when the device is used in a process with other equipment (e.g., a reverse osmosis unit and / or a filtration unit) the operational requirements of both power and water may be minimized. Flushing may be performed with or without cell power.

[0062] In an embodiment of the present disclosure, during the regeneration stage, the electrode polarity is reversed relative to the desorption stage. The feed solution for regeneration may be purified water, tap water, local water, process water, effluent from a prior regeneration stage, or a combination thereof.

[0063] An aspect of the present disclosure relates to a method for producing lithium hydroxide from a complex lithium-containing feed stream, the method comprising: uptaking lithium ions from the complex lithium-containing feed stream into an asymmetric-BPMA by flowing the complex lithium-containing feed stream through the asymmetric-BPMA and applying a forward bias across a pair of electrodes to induce an electric field within the asymmetric-BPMA, wherein the asymmetric- BPMA comprises: a CEL that is permselective and that comprises a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an AEL that is permselective and that comprises an ionomeric material;releasing lithium ions from the asymmetric-BPMA to a lithium hydroxide stream by flowing an ion capture stream through the asymmetric-BPMA and applying a reverse bias across the electrode pair.

[0064] In an embodiment of the present disclosure, forward bias is applied to effect adsorption, during which the voltage is constant, the resistance is determined by the number of asymmetrical-BPMAs used within the ERIX device, and water splitting occurs primarily at the ERIX device electrodes.

[0065] In an embodiment of the present disclosure, the ERIX device voltage during adsorption, as measured across the entire device, is approximately 3 V or less. During this cycle the current (and current density) may be constant.

[0066] In an embodiment of the present disclosure, reverse bias is applied to effect desorption, wherein the voltage achieved is dependent on: (i) the initial concentration of the complex lithium-containing feed solution, and (ii) the number of ions adsorbed (chemically or physically) by the asymmetrical-BPMA. As those skilled in the art who have benefited from the teachings of the present disclosure will appreciate, the voltage during desorption is variable and increases over time as less ions are present within the asymmetrical-BPMA. Similarly, the total voltage required is dependent on the AEL and CEL surface area, such that increasingly higher voltages will be required during desorption as membrane surface area increases in larger asymmetrical-BMPAs.

[0067] In an embodiment of the present disclosure, the ERIX device resistance during desorption, as defined across the entire device, is up to and including 100 V.

[0068] In an embodiment of the present disclosure, the equivalent time adsorption to desorption may be in the range of from about 1 hour to about 10 hours. For example, the adsorption and desorption cycles may be in the range of from about 1 hour to about 3 hours, or from about 2 hours to about 5 hours, or from about 3 hours to about 6 hours.

[0069] In an embodiment of the present disclosure, the adsorption cycle time and desorption cycle time may be different.

[0070] The duration of the cycles may be dependent on one or more factors, including but not limited to: complex feed solution composition (e.g., lithium concentration, specific chemical impurity profile), ERIX device size (e.g., total number of membranes, membranesize, rate of water splitting), and operational parameters (e.g., flow rate, applied current relative to device resistance, and product stream purity). For these reasons, it may be necessary to operate the asymmetrical-BPMA device for an adsorption cycle time that may differ from the desorption cycle time.

[0071] In an embodiment of the present disclosure, the complex lithium-containing feed stream may be degassed prior to its introduction into the asymmetrical-BPMA ERIX device. As those skilled in the art may appreciate, dissolved carbon dioxide will slowly convert aqueous lithium hydroxide into lithium carbonate. Accordingly, it may be advantageous to substantially remove carbon dioxide from the solution prior to adsorption, for example, by physical (e.g., nitrogen gas sparge, or freeze-pump-thaw (FPT) cycling with nitrogen gas) or by chemical (e.g., precipitation) means.

[0072] Figure 1 shows a schematic representation of a two-layer asymmetric-BPMA 100 in accordance with an embodiment of the present disclosure. The asymmetric-BPMA 100 comprises an inorganic CEL 102 and an ionomeric AEL 104. The inorganic CEL 102 and the ionomeric AEL 104 are coupled for hydraulic communication at an interface 106. During operation, salt formation may occur at the interface 106 as a result of cations migrating across the inorganic CEL 102 and anions migrating across the ionomeric AEL 104. In particular, lithium hydroxide salt may form in solution as a result of lithium ions migrating across the inorganic CEL 102 and hydroxide ions migrating across the ionomeric AEL 104. Also, because the inorganic CEL 102 and the ionomeric AEL 104 are sufficiently permselective to facilitate electrochemical interventions in the presence of an electric field, water splitting may occur at interface 106 to produce protons and hydroxide ions thereby modulating the alkalinity or pH in proximity to the inorganic CEL 102.

[0073] Salt formation at the interface 106 may correlate with adsorption as described above, whereby cations are drawn into the inorganic CEL 102, and anions are drawn into the ionomeric AEL 104. Without being bound to any particular theory, the accumulation of anions at the interface 106 may create a local pH gradient or increased local alkalinity thereby increasing the loss of protons from inorganic CEL 102. This occurrence may facilitate lithium ion binding within the inorganic CEL 102. In the ionomeric AEL 104, retention of anions may be significantly limited, compared to conventional ion-exchange devices, as the homogenous physical structure, charge distribution, and / or thinapplication of the ionomer may attenuate retention of chloride ions, sulfate ions, and / or other non-hydroxide ions.

[0074] Conversely, water splitting at the interface 106 may correlate with desorption as described above, whereby the generated protons migrate outward through the inorganic CEL 102 and generated hydroxide ions migrate outward through the ionomeric AEL 104. By increasing the concentration of protons moving into the inorganic CEL 102, the sorbing agent may preferentially bind hydrogen and release lithium according to their relative binding coefficients under the governing pH or alkalinity regime. This may result in lithium ions being released into the solution.

[0075] Figure 2 shows a schematic representation of an asymmetric-BPMA 200 in accordance with an embodiment of the present disclosure. The asymmetric-BPMA 200 has three layers: an inorganic CEL 202, an ionomeric AEL 204, and an organic CEL 206. The inorganic CEL 202 and the ionomeric AEL 204 are permselective, and they are coupled for hydraulic communication at an interface 208 such that the asymmetric-BPMA 200 may function as described with respect to asymmetric-BPMA 100 in regard to salt formation and / or water splitting. In asymmetric-BPMA 200, the organic CEL 206 is coupled to inorganic CEL 202 at an interface 208. The organic CEL 206 may serve a variety of purposes such as providing monovalent ion selectivity ( / .e., allowing passage of sodium and lithium ions, while attenuating the passage of calcium and magnesium ions). In the asymmetric-BPMA 200, the organic CEL 206 can be configured to avoid unduly lowering overall device efficiency and / or inhibiting the desired water splitting processes.

[0076] Figure 3 shows a schematic representation of an asymmetric-BPMA 300 in accordance with an embodiment of the present disclosure. A conventional organic CEL 341 and a conventional organic AEL 342 are inserted directly between an inorganic CEL 311 and an ionomer AEL 321. The device membranes are oriented such that a) each individual membrane is adjacent to a membrane of opposing polarity, such that each membrane pair 302. 303, and 304 each form a bipolar membrane unit; b) three individual interstitial boundaries 306. 307, and 308 exist where water splitting may occur; and c) the inorganic CEL 311 and ionomeric AEL 321 are external. Those skilled in the art may appreciate that additional water splitting would increase the local concentration of hydroxide ions, thereby further promoting adsorption of lithium ions from the solution.By ensuring the organic AEL 342 is internal, its contact with complex solutions is limited, and the chances for retention of disadvantageous anions is significantly reduced.

[0077] Figures 4A-C show schematic perspective representations of an ERIX device in accordance with an embodiment of the present disclosure. The ERIX device comprises a plate-and-frame construction. An example of such a device is outlined within Figure 4A, where a plurality of asymmetric-BMPAs is contained between two electrodes 403 and 404. In an embodiment of the present disclosure, electrode 403 is the electrode positioned proximal to the ERIX device inlet and marks the beginning of the device solution flow path. A cross-sectional expansion is described in Figure 4B, depicting the membranes (AEL 413 and CEL 414) with their individual approximate relative thicknesses. A further cross-sectional structural expansion, as depicted in Figure 4C, describes an embodiment of the present disclosure wherein the asymmetric-BMPA subunit comprises: an AEL 413 at the edge of the subunit proximal to the ERIX device inlet; the AEL 413 is coupled to the CEL 414; a thin mesh spacer 425 is used to support the CEL 414; a thick mesh spacer 426 is used to allow complex lithium-containing feed solutions to contact the asymmetric-BMPA surfaces; and a gasket 427, is used to prevent direct contact between membrane subunits. So configured, the asymmetric-BMPA subunits are assembled in a plurality as shown in example Figure 4A.

[0078] Figure 5A and Figure 5B, taken together, depict a cross-sectional flow diagram and a cross-sectional ion path diagram, respectively, for an asymmetric-BMPA ERIX device during an adsorption cycle. Similarly, Figure 6A and Figure 6B, taken together, depict a cross-sectional flow diagram and a cross-sectional ion path diagram, respectively, for the asymmetric-BMPA ERIX device during a desorption cycle. These diagrams describe an example device configuration in accordance with specific embodiments of the present disclosure.

[0079] In Figure 5A, the ERIX device 501 is configured with the first electrode 511 at the device inlet stream 521, and the first electrode is negatively polarized (cathode). The second electrode 512 is positioned at the device outlet stream 522, and the second electrode is positively polarized (anode). Between these electrodes are placed a plurality of individual asymmetric-BMPAs (e.g., 531) in accordance with an embodiment of the present disclosure, each of which is comprised of an inorganic CEL 532 and organic anionic ionomer layer 533. By establishing a current across the device, water splittingmay occur at the first electrode 511. So configured, the ERIX device 500 is capable of performing an adsorption cycle.

[0080] The ionic flow during adsorption cycles is described in Figure 5B. A singular asymmetric-BMPA is shown to represent the ERIX device 502, with the remaining membrane plurality omitted for simplicity (as denoted by the caesura 503). Water splitting at the first electrode is described (504) and generates an excess of hydroxide ions 514 that may then permeate into the asymmetric-BMPA ionomeric AELs (533). As this occurs, as proposed, the resultant recombination with CEL (532) hydrogen ions allows for lithium cations 513 to move out of the solution and be captured within the CEL.

[0081] In Figure 6A, ERIX device 601 is configured with the first electrode 611 at the ERIX device inlet stream 621, and the first electrode is positively polarized (anode). The second electrode 612 is positioned at the ERIX device outlet stream 622, and the second electrode is negatively polarized (cathode). Between these electrodes are placed a plurality of asymmetric-BMPAs (e.g., 631) in accordance with an embodiment of the present disclosure, each of which comprised an inorganic CEL 632 and organic anionic ionomer layer 633. So configured, the ERIX device 600 is capable of performing a desorption cycle.

[0082] The ionic flow during desorption cycles is described in Figure 6B. A singular asymmetric-BMPA is shown to represent the ERIX device 602, with the remaining ERIX asymmetric-BMPAs for simplicity omitted (as denoted by the caesura 603). Water splitting occurs at the membrane boundary (604), and generates OH- 614, which moves freely back out through the AEL and into the solution. The hydrogen ions generated move into the CEL and displace lithium ions 613 in the sorbing agent, allowing said lithium ions to move into the solution.

[0083] All other aspects of the ERIX device described in Figure 5A, Figure 5B, Figure 6A, and Figure 6B are similarly constructed. The asymmetric-BMPA plurality has identical physical arrangement, with the electrode (511 and 611) facing the first AEL (e.g., 533 and 633), with the second electrode facing the last CEL (e.g., 534 and 634). The flow path is staggered through the asymmetric-BMPAs, and those skilled in the art will appreciate that such a flow path is a singular example of a multitude of solution flow arrangements (e.g., spiral flow) that could be achieved in a similar plate-and-frame device, or alternative ion exchange devices (e.g., cartridge). In the presence of complexlithium-containing feed solutions, the asymmetric-BMPA layers maintain sufficient permselectivity. Within the context of the present disclosure, "sufficient permselectivity” indicates that each layer is repelling ions of identical polarity while allowing ions of opposing polarity to move across the respective layer towards the water splitting boundary. Under these conditions, the operating voltage is maintained at less than about 3 V.

[0084] Example 1: Preparation and analysis of archetypal CEL compositions

[0085] Table 1 summarizes two CEL compositions (referred to as alpha and beta, respectively), each based on a binary mixture of lithium titanate and a polyolefin binder. The CEL compositions were prepared by mixing the noted quantities in 50 cc Brabender® plastic processing equipment and then pressing the mixtures into thin slabs using a hot press.

[0086] Table 1: Archetypal CEL material compositions

[0087] It was determined that the Beta composition had sufficient structural integrity to form into 0.100 mm sheets that were 15 cm wide and 15 cm tall. The Alpha composition flowed more readily, and it provided thinner sheets of the same dimensions (0.030 mm). The swelling and specific resistance of the Alpha composition and the Beta composition were determined, and the results are summarized in Table 2. The specific resistances achieved were determined to be suitable for incorporation into asymmetric-BPMAs as described in Example 2.

[0088] Table 2: Archetypal CEL material propertiesExample 2: Preparation of archetypal asymmetric-BPMA

[0089] Commercial anionic ionomeric materials may be purchased for use as AELs, for example, the anionic ionomeric materials may be supplied as pre-cut sheets or rolls (e.g., Aemion*™). As those skilled in the art may appreciate, where available the anionic ionomeric material component(s) may also be sourced to develop specifically sized AELs by processing the ionomer sheets in-house. In such cases, as those skilled in the art may appreciate, such solution-based preparation may require an appropriate methodology for generating thin films (e.g., ink formulation, spin coating).

[0090] With a given AEL and CEL appropriately sized for the intended ERIX device (170 x 125 mm) both materials may be placed within an aluminum shim with a target thickness = 0.012 mm, having the AEL placed on top of the CEL. Both materials are then laminated together using: (i) a hot press: 118 °C at 2’000 lbs for 2 mins, followed by 118 °C at 40’000 lbs for 5 secs; and then (ii) a cold press: 20 °C at 20’000 lbs for 1 min. The asymmetrical- BPMAs were subsequently swollen in a hot water bath, 90 °C for 30 mins.Example 3: Assessing ion exchange capacity for an archetypal asymmetric-BPMA

[0091] Figure 7A and Figure 7B show examples of membrane exchange over time for an archetypal asymmetric-BPMA as assembled into an ERIX device in accordance with the present disclosure and as generally described in the PCT patent application published under number WO 2022 / 236415 Al, the contents of which is herein incorporated by reference. The data was collected using a synthetic brine, and the asymmetric-BPMA stack was shown to consistently cycle through all present species (lithium, sodium, potassium, and sulfate) through each of the adsorption-desorption cycles. In Figure 7A, the capacity is represented graphically by total membrane exchange (mg / L) of ions over time, with adsorption 712 denoted by a negative exchange value and desorption 713 denoted by a positive exchange value. Figure 7B, depicts an expansion of an absorption and desorption cycle 721. The desorption cycle shows an exponential drop in sodium and potassium (723, combined), and sulfur (724). Without being bound to any particular theory, the exponential profile and rapidly decreasing concentration may be considered consistent with removal of physisorbed elements (e.g., chemical species that are loosely bound either (a) on the membrane surface, (b) within the polymer binder porous channels, or (c) on the surface of the sorbing agent). The elution profile for lithium (722), conversely, shows a sustained concentration. Those skilled in the art may appreciate that such a profile is rate determined, whereby loss of lithium from the membrane can onlybe achieved after the completion of a necessary secondary process, in this case water splitting at the membrane surface. Lithium that is chemisorbed directly into the sorbing agent structure can be removed by the sustained generation of hydrogen ions. Control of the lithium elution rate in this manner allows for rapid removal of physisorbed impurity species followed by consistent elution of lithium. In the absence of the anionic impurities (in the present disclosure, sulfate) the lithium ions in solution will preferentially undergo salt formation with available hydroxide ions produced via water splitting.Example 4: Comparative testing against a Previous Disclosure

[0092] To evaluate the performance of the asymmetric-BMPA of the present disclosure, a similar plate-and-frame ERIX device was constructed using a BPMA with an identical CEL and conventional AEL. This alternative device was constructed as per the parameters outlined in the PCT patent application published under number WO 2022 / 236415 Al.

[0093] To assess performance characteristics of the asymmetric-BMPA ERIX device, a comparative best in class ERIX ion-exchange (IEX) devices. Identical ERIX configurations, using the same plate-and-frame assembly, identical membrane area (170 x 125 mm), and operated under the same conditions for a) adsorption; 40 minutes, 30 mL / min flow rate, current set to 1.5 A, and b) desorption; 90 minutes, 30 mL / min flow rate, to analyze the same synthetic brine comprised of 2000 mg / L Li+, 5000 mg / L Na+, and 5000 mg / L K+ using identical eluent (150 mg / L Li+, prepared from LiO H-H2O). Table 3 highlights performance results for both devices.Table 3: Head-to-head Comparison 1

[0094] The ERIX device comprising the asymmetric-BMPA shows a faster lithium desorption rate, a higher total lithium desorbed, and a lower anionic impurity concentration at the end of the desorption cycle; this device also shows a lower powerrequirement for desorption, with a lower effective current. Figure 8 shows an excerpt of the membrane exchange desorption data for each device, side by side. Graph 801 displays the data for the present disclosure, and Graph 802 displays the data for the previously disclosed ERIX device. The curves are notably different in their lithium desorption values 811 and 812, respectively, where the ERIX device comprising the asymmetric-BMPA is shown to desorb a significantly larger amount of lithium. Similarly, the loss of disadvantageous sulfate is immediately exponential in the asymmetric-BMPA case and is below detection levels before desorption is complete, whereas the previously disclosed ERIX device shows sulfate at the highest concentration of any ionic species (822) when desorption is stopped.Example 5: Recycling Experiments

[0095] To evaluate sustained performance of the asymmetric-BMPA ERIX device, a high concentration synthetic brine was used with a device configured exactly as per Example 4 where the brine was introduced to the system only once, and the depleted brine produced during desorption was recycled back to the device inlet for the subsequent adsorption cycle. As noted in Figure 9, the competing cations (sodium and potassium 922) are shown to decrease linearly in the recycled depleted brine, and at a faster rate than lithium cations 921, which suggests a higher degree of physisorption for both ions and a greater selectivity (and specific chemisorption) for lithium. Lithium desorption 931 is maintained at the highest rate of any ion and is consistent through all cycles indicating sustained elution performance of the plurality of asymmetrical-BPMAs. Sulfate absorption is omitted for clarity, as its concentrations are significantly higher than all other ions, but its rapid desorption (933, overlapping with sodium and potassium 923) is shown and suggests that sulfur has little to no retention within the system.

[0096] While particular aspects of the subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein.

[0097] All technical and scientific terms and expressions used herein have the same definitions as those commonly understood by the person skilled in the art when relating to the present technology. The definition of some terms and expressions used herein is nevertheless provided below for clarity purposes.

[0098] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims are generally intended as "open” terms (e.g., the term "comprising” should be interpreted as "including but not limited to”,” the term "having” should be interpreted as "having at least,” the term "has” should be interpreted as "has at least,” etc.). For the purposes of the present disclosure, the expression "consisting of” is considered to be a preferred embodiment of the term "comprising”. If a group is defined hereinafter to include at least a certain number of implementations, it is also to be understood to disclose a group, which preferably consists only of these implementations. As used herein, the term "and / or” includes any and all combinations of one or more of the associated listed items.

[0099] It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one” and "one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a” or "an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases "one or more "or "at least one” and indefinite articles such as "a” or "an” (e.g., "a” and / or "an” should typically be interpreted to mean "at least one” or "one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).

[0100] Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense onehaving skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense of one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, etc.).

[0101] It will be further understood by those within the art that typically a disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase "A or B” will be typically understood to include the possibilities of "A” or “B” or "A and B.”

[0102] With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise.

[0103] Throughout this application, the terms "in an embodiment”, "in one embodiment”, "in an embodiment”, "in several embodiments”, "in at least one embodiment”, "in various embodiments,” and the like, may be used. Each of these terms, and all such similar terms should be construed as "in at least one embodiment, and possibly but not necessarily all embodiments,” unless explicitly stated otherwise. Specifically, unless explicitly stated otherwise, the intent of phrases like these is to provide non-exclusive and non-limiting examples of implementations of the subject matter.

[0104] The term of degree "substantially”, as used herein means a reasonable amount of deviation of the modified term such that the end result is not significantly changed. Theterm "substantially” should be construed as including a deviation of ±5% of the modified term if this deviation would not negate the meaning of the term it modifies. The terms of degree "about” and "approximately” should be construed as including a deviation of ±20%. Other terms of degrees should be construed as including a deviation of ±5% of the modified term.

[0105] When a range of values is mentioned herein, the lower and upper limits of the range are, unless otherwise indicated, always included in the definition. When a range of values is mentioned in the present application then all intermediate ranges and subranges, as well as individual values included in the ranges, are intended to be included.

[0106] The mere statement that one, some, or may embodiments include one or more things or have one or more features, does not imply that all embodiments include one or more things or have one or more features, but also does not imply that such embodiments must exist. It is a mere indicator of an example and should not be interpreted otherwise, unless explicitly stated as such.

[0107] When trade names are used herein, it is intended to independently include the tradename product and the active ingredient(s) of the tradename product.

[0108] Those skilled in the art will appreciate that the foregoing specific exemplary membranes and / or devices and / or methods are representative of more general processes and / or devices and / or technologies taught elsewhere herein, such as in the claims filed herewith and / or elsewhere in the present application.

Claims

CLAIMS1. An asymmetric bipolar membrane apparatus for producing lithium hydroxide from a complex lithium-containing feed stream, the asymmetric bipolar membrane apparatus comprising: a cation exchange layer comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative values of the lithium ion binding coefficient and the hydrogen ion binding coefficient are alkalinity dependent or pH dependent; and an anion exchange layer comprising an ionomeric material; wherein the cation exchange layer and the anion exchange layer are coupled and configured for hydraulic communication, and wherein the cation exchange layer and the anion exchange layer are sufficiently permselective to facilitate electrochemical interventions that modulate alkalinity or pH in proximity to the cation exchange layer.

2. The asymmetric bipolar membrane apparatus of claim 1, wherein the cation exchange layer has a thickness of less than approximately 0.5 mm.

3. The asymmetric bipolar membrane apparatus of claim 1 or 2, wherein the sorbing agent of the cation exchange layer is selected from the group consisting of an inorganic metal oxide, a crown ether, a metal-organic framework (MOF), and a combination thereof.

4. The asymmetric bipolar membrane apparatus of any one of claims 1 to 3, wherein the cation exchange layer further comprises a polymer binder.

5. The asymmetric bipolar membrane apparatus of claim 4, wherein the polymer binder is a melt processible polymers selected from the group consisting of saturated polyolefins and unsaturated polyolefins.

6. The asymmetric bipolar membrane apparatus of any one of claims 1 to 5, wherein the anion exchange layer has a thickness that is about 15% of that of the cation exchange layer.

7. The asymmetric bipolar membrane apparatus of any one of claims 1 to 5, wherein the anion exchange layer has a thickness in the range of from about 10 pm to about 100 pm.

8. The asymmetric bipolar membrane apparatus of claim 7, wherein the anion exchange layer has a thickness in the range of from about 60 pm to about 80 pm.

9. The asymmetric bipolar membrane apparatus of claim 7, wherein the anion exchange layer has a thickness in the range of from about 10 pm to about 40 pm.

10. The asymmetric bipolar membrane apparatus of any one of claims 1 to 9, wherein the anionic ionomer material of the anion exchange layer is selected from the group consisting of Aemion+™, Fumasep™ FAPQ-375, and Neosepta™ CAN.

11. The asymmetric bipolar membrane apparatus of any one of claims 1 to 10, wherein the cation exchange layer and the anion exchange layer are coupled by casting.

12. The asymmetric bipolar membrane apparatus of any one of claims 1 to 10, wherein the cation exchange layer and the anion exchange layer are coupled by spray coating, spin coating, or drop casting.

13. The asymmetric bipolar membrane apparatus of any one of claims 1 to 12, wherein lithium hydroxide is in solution form, in suspension form, in colloidal suspension form, in slurry form, in precipitated form, or other dispersion forms.

14. The asymmetric bipolar membrane apparatus of any one of claims 1 to 12, wherein lithium hydroxide is a dilute aqueous stream containing at least about 100 ppm of lithium hydroxide in water, or at least about 500 ppm of lithium hydroxide in water, or at least about 750 ppm of lithium hydroxide in water.

15. An electrically regenerated ion exchange (ERIX) device for producing lithium hydroxide from a complex lithium-containing feed stream, the ERIX device comprising: a flow path from an inlet of the ERIX device to an outlet of the ERIX device; a first electrode in proximity to the flow path; a second electrode in proximity to the flow path; andan asymmetric bipolar membrane apparatus within an electric field defined by the first electrode and the second electrode, wherein the asymmetric bipolar membrane apparatus comprises: a cation exchange layer comprising a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an anion exchange layer comprising an ionomeric material; wherein the cation exchange layer and the anion exchange layer are coupled and configured for hydraulic communication, and wherein the cation exchange layer and the anion exchange layer are sufficiently permselective to facilitate electrochemical interventions that modulate alkalinity or pH in proximity to the cation exchange layer in response to perturbations in the electric field.

16. The ERIX device of claim 15, wherein the electric field is controlled by current and / or voltage.

17. The ERIX device of claim 15 or 16, wherein the first electrode and / or the second electrode are made of a material selected from the group consisting of iridium oxide coated titanium, platinum coated titanium, stainless steel, and nickel.

18. The ERIX device of any one of claims 15 to 17, wherein the first electrode and the second electrode are made of the same material.

19. The ERIX device of any one of claims 15 to 18, wherein the first electrode, relative to the ERIX device flow path from the inlet, is modified with an alternative material designed to promote hydrogen gas evolution.

20. A method for producing lithium hydroxide from a complex lithium-containing feed stream, the method comprising: uptaking lithium ions from the complex lithium-containing feed stream into an asymmetric bipolar membrane apparatus by flowing the complex lithium- containing feed stream through the bipolar membrane apparatus and applyinga forward bias across an electrode pair to induce an electric field within the bipolar membrane apparatus, wherein the bipolar membrane apparatus comprises: a cation exchange layer that is permselective and that comprises a sorbing agent having a lithium ion binding coefficient and a hydrogen ion binding coefficient, wherein the relative value of the lithium ion binding coefficient and the hydrogen ion binding coefficient is alkalinity dependent or pH dependent; and an anion exchange layer that is permselective and that comprises an ionomeric material; releasing lithium ions from the bipolar membrane apparatus to a lithium hydroxide stream by flowing an ion capture stream through the asymmetric bipolar membrane apparatus and applying a reverse bias across the electrode pair.

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