Method and system for metal extraction, purification and enrichment from waste mixture

Abstract

A process and a system for extracting one or more metals from an waste mixture are provided. The process comprises extracting one or more metals from an waste mixture comprising one or more recoverable metals using a metal extraction process and an organic solvent electrodialysis process. The processes comprising contacting the waste mixture with an organic solvent comprising a deep eutectic solvent (DES) for metal extraction to obtain a metal-containing feed solution; subjecting the metal-containing feed solution to electrodialysis to separate one or more metal ions from the metal-containing feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution.

Description

METHOD AND SYSTEM FOR METAL EXTRACTION, PURIFICATION AND ENRICHMENT FROM WASTE MIXTURECROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to the Singapore patent application no. 10202403017T filed on 27 September 2024, the contents of which are hereby incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] This application relates to a method and system for extracting one or more metals from a waste mixture. In particular, the application relates to a method and system for extracting one or more metals from a waste mixture comprising one or more recoverable metals using an organic solvent electrodialysis process.BACKGROUND

[0003] The rapid expansion of transportation electrification and consumer electronics has driven an unprecedented demand for battery production and other electronic components, leading to an increasing accumulation of electronic waste (e-waste). E-waste mixtures, which often include spent lithium batteries (LIBs), are rich in valuable and critical metals such as lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn). These metals are particularly important for lithium battery cathode materials such as lithium nickel manganese cobalt oxide (NMC), which offers a favorable balance of specific energy, structural stability, and thermal performance The demand for such metals is projected to increase more than tenfold between 2020 and 2050. Given the low current recycling rates, secondary mining from e-waste is critical for alleviating resource scarcity while minimizing the environmental impact of primary mining and improper disposal.

[0004] Current recycling approaches for e-waste include direct reuse, pyrometallurgy, and hydrometallurgy. While direct reuse seeks to preserve device or cathode structures, its applicability is limited. Pyrometallurgy is widely used but involves high energy input, harmful emissions, and costly downstream refining. Hydrometallurgy, which converts metals into ions in solution, offers relatively lower energy consumption and high recovery yields. However, it typically relies on strong inorganic acids (e g., sulfuric acid, nitric acid) or toxic organic solvents, resulting in wastewater generation, equipment corrosion, and ecological harm.

[0005] Deep eutectic solvents (DESs) have recently emerged as cost-effective, environmentally friendly alternatives for metal recovery from complex solid mixtures such as e-waste. Deep eutectic solvents are formed from hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) and can be prepared from inexpensive, safe precursors. Deep eutectic solvents exhibit tunability, biodegradability, and multifunctionality, serving both as extractants and reducing agents capable of breaking down metal-oxygen bonds without additional reagents. These features make deep eutectic solvents attractive for selective dissolution of valuable metals from e-waste.

[0006] Despite their potential, DES-based processes for e-waste recycling face several challenges. Conventional separation techniques, such as precipitation or solvent extraction, may result in co-precipitation or co-extraction of deep eutectic solvents components, thereby reducing the purity of recovered metals and altering solvent composition, which compromises reusability. In some cases, addition of external precipitants has been required to recover dissolved metals, which can reduce overall efficiency and contaminate the deep eutectic solvents. Electrodeposition has also been explored as a separation route, but this approach is limited by slow yield rates, high energy consumption, and restricted compatibility with complex waste matrices. These issues hinder the efficiency and sustainability of DES-based recovery processes when applied to e-waste.

[0007] Accordingly, there remains a need for a process and a system that enable efficient recovery of valuable metals from waste mixture comprising one or more recoverable metals, while addressing at least some of the problems described hereinabove, or at least to provide an alternative solution.SUMMARY

[0008] According to a first aspect of the present disclosure, a process for extracting one or more metals from a waste mixture is provided. The process comprises extracting one or more metals from a waste mixture comprising one or more recoverable metals using a metal extraction process and an organic solvent electrodialysis process. The processes comprises contacting the waste mixture with an organic solvent comprising a deep eutectic solvent (DES) for metai extraction to obtain a metal -containing feed solution; subjecting the metal -containing feed solution to electrodialysis to separate one or more metal ions from the metal -containing feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution.

[0009] In some embodiments, the step of electrodialysis comprises introducing the metalcontaining feed solution into an organic solvent electrodialysis unit, wherein the one or more metal ions are separated from the metal-containing feed solution by selective ions migration within the organic solvent electrodialysis unit.

[0010] In some embodiments, the organic solvent electrodialysis unit comprises one or more electrodialysis stacks, each of the electrodialysis stacks comprises an anode, a cathode, one or more anion exchange membranes (AEMs) and one or more cation exchange membranes (CEMs) arranged alternately, for selectively separating the one or more metal ions from the metal-containing feed solution.

[0011] According to a second aspect of the present disclosure, a system for extracting one or more metals from a waste mixture is provided. The system comprises a reaction tank forreceiving an organic solvent and a waste mixture comprising one or more recoverable metals for metal extraction to obtain a metal-containing feed solution; an organic solvent electrodialysis unit in fluid communication with the reaction tank, the organic solvent electrodialysis unit comprises one or more electrodialysis stacks comprising: an anode; a cathode; and one or more anion exchange membranes (AEMs) and one or more cation exchange membranes (CEMs) arranged alternately, for selective separation of one or more metal ions from the metal-containing feed solution, a first tank in fluid communication with the organic solvent electrodialysis unit, for receiving and discharging a metal recovery solution; and a second tank in fluid communication with the organic solvent electrodialysis unit and the reaction tank, for receiving a solution comprising the organic solvent from the organic solvent electrodialysis unit and discharging the solution containing the organic solvent to the reaction tank, thereby forming a closed-loop system.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Various embodiments of the present disclosure are described hereinbelow in the detailed description with reference to the following drawings:FIG. 1 is a schematic illustration of an organic solvent electrodialysis process for the recovery of one or more metals from an electronic waste mixture, in accordance with an embodiment of the present disclosure.FIG. 2A is a schematic illustration of the structure and configuration of the organic solvent electrodialysis unit in accordance with an embodiment of the present disclosure.FIG. 2B is a schematic illustration of a repeating unit of the organic solvent electrodialysis unit, illustrating ion migration under an applied electric field in a deep eutectic solvent (DES) and aqueous recovery streams (RS).FIGs. 3A to 3D are schematic illustrations of optional units that may be employed in the organic solvent electrodialysis process for enhancing the metal separation and purification. FIG. 3A isa schematic illustration of a centrifugation unit. FIG. 3B is a schematic illustration of a precipitation unit. FIG. 3C is a schematic illustration of an additional organic solvent electrodialysis unit, and FIG. 3D is a schematic illustration of a solvent / water extraction unit. FIG. 4 is a schematic illustration of a potential post-concentration unit that may be employed to increase concentration of the metal products in the metal recovery solution. FIG. 4(a) is a schematic illustration of a membrane filtration (nanofiltration or reverse osmosis) unit, while FIG. 4(b) is a schematic illustration of an electrodialysis stack.FIG. 5 is a schematic illustration of one exemplary embodiment of an organic solvent electrodialysis system for metal extraction, separation, purification and recovery from spent lithium batteries.FIGs. 6A to 6D shows the effectiveness of the organic solvent electrodialysis system as depicted in FIG. 5, for recovery of one or more metals from spent lithium batteries. FIG. 6A is a bar chart showing the results of metal recovery from a precipitation unit. FIG. 6B is a bar chart showing the results of metal recovery from water washing unit. FIG. 6C is a bar chart showing the results of metal recovery from the organic solvent electrodialysis unit. FIG. 6D is a bar chart showing a comparison of metal extraction between fresh and regenerated deep eutectic solvents via organic solvent electrodialysis.FIG. 6E is a bar chart showing the overall metal recovery efficiency of the system for spent lithium batteries.FIG. 7A is a plot showing the concentration profiles of Mn, Co, Ni, and Li in the DES during organic solvent electrodialysis operation.FIG. 7B is a plot showing the metal concentration profiles and lithium purity in the metal recovery solution.FIG. 7C is a plot showing the ion transport rates of Li, Mn, Co, and Ni across the CEM over time.FIG. 7D is a bar chart showing the selectivity of Li over other metals (Mn, Ni, and Co).FIG. 8A is a plot showing the lithium concentration in deep eutectic solvent over three electrodialysis cycles.FIG. SB is a bar chart showing the selectivity of lithium over manganese across three organic solvent electrodialysis cycles.FIG. SC is a graph showing the FTIR spectra of CEM before and after the organic solvent electrodialysis cycles and ageing tests.FIG. 8D a graph showing the FTIR spectra of AEM before and after the organic solvent electrodialysis cycles and ageing tests.FIG. 8E is a graph showing the FTIR spectra of fresh DES compared to recycled DES after cycling tests.FIG. 8F is a bar chart showing the resistance measurements of CEM before and after organic solvent electrodialysis cycles and ageing tests.FIG. 8G is a bar chart showing the resistance measurements of AEM before and after organic solvent electrodialysis cycles and ageing tests.FIG. 8H is a bar chart showing the performance of fresh and recycled DES for metal extraction from fresh cathode materials of lithium batteries (i.e., NMC532).FIG. 9A is a graph showing the transport rates of Li+(left y-axis) and Mn2+(right y-axis) in DES through CEM as a function of applied current density.FIG. 9B is a plot showing Li purity and Li / Mn selectivity as a function of current density.FIG. 9C is a graph showing the transport rates of choline ions (Ch+) as a function of current density.FIG. 9D is a graph showing the comparison between experimental and predicted transport rates of ions in DES phase through CEM in organic solvent electrodialysis process.FIG. 9E is a graph showing the transport numbers of Li+, Mn2+, Ch+, and proton ions (H O+) though CEM in SED.FIG. 9F is a bar chart showing the diffusion coefficients in a solution containing an organic solvent (Ds) and in the membrane(Dm) for Li, Mn, and Ch ions.FIG. 9G is a schematic illustration of the transport mechanism, illustrating the migration of Li+, Mn2+and Ch+in the DES phase and across the CEM.FIG. 10A is an SEM image of a pristine mCEM before the organic solvent electrodialysis operation.FIG. 10B is an SEM image of a pristine mAEM before the organic solvent electrodialysis operation.FIG. IOC is an SEM image of an mCEM after SED (solvent electrodialysis) cycling.FIG. 10D is an SEM image of an mAEM after SED cycling.FIG. 10E is an SEM image of an mCEM after aging in DES leachate.FIG. 1 OF is an SEM image of an mAEM after aging in DES leachate.FIG. 11A shows the EDX spectrum and elemental analysis results of a pristine mCEM.FIG. 11B shows the EDX spectrum and elemental analysis results of an mCEM after SED cycling.FIG. 11C shows the EDX spectrum and elemental analysis results of a pristine mAEM.FIG. 11D shows the EDX spectrum and elemental analysis results of an mAEM after SED cycling.DETAILED DESCRIPTION

[0013] The following detailed description is made with reference to the accompanying drawings, showing details and embodiments of the present disclosure for the purposes of illustration. Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments, even if not explicitly described in these other embodiments. Additions and / or combinations and / or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments

[0014] In the context of various embodiments, the articles “a”, “an” and “the” as used with regard to a feature or element include a reference to one or more of the features or elements.

[0015] In the context of various embodiments, the term “about” or “approximately” as applied to a numeric value encompasses the exact value and a reasonable variance as generally understood in the relevant technical field, e.g., within 10% of the specified value.

[0016] As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0017] As used herein, “comprising” means including, but not limited to, whatever follows the word “comprising”. Thus, use of the term “comprising” indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present.

[0018] As used herein, “consisting of’ means including, and limited to, whatever follows the phrase “consisting of’. Thus, use of the phrase “consisting of’ indicates that the listed elements are required or mandatory, and that no other elements may be present.

[0019] A detailed description of various embodiments will be described below with reference to the drawings.

[0020] Definitions

[0021] As used herein, the term “waste mixture” refers to a waste mixture comprising one or more recoverable metals. The waste mixture may originate from the manufacturing, use, processing, recycling, or discarding of metal-containing materials. Non-limiting examples include mixtures derived from discarded electronic and / or electrical equipment (e-waste), spent batteries, mining residues, metallurgical by-products, industrial effluents, brines, and pharmaceutical or chemical production wastes. The waste mixture may include solid waste, liquid waste, or a combination thereof.

[0022] As used herein, the term “electrodialysis unit” refers to an apparatus comprising at least one pair of ion-exchange membranes (i.e., an anion exchange membrane and a cation exchange membrane) arranged between electrodes, thereby defining at least one electrodialysiscell. A plurality of such cells may be stacked together to form an electrodialysis stack, which is also encompassed within the term “unit” as used herein. Unless otherwise specified, the expression “organic solvent electrodialysis unit” or “organic solvent electrodialysis process” refers to such an electrodialysis apparatus or process in which the feed solution contains the organic solvent medium, instead of water, as the principal solvent. The principal solvent in the feed solution (dilute) comprises an organic solvent or a mixture of non-aqueous solvents, including but not limited to, deep eutectic solvents, ionic liquids and other organic solvents including, but not limited to, ethylene glycol, polyethylene glycol, methanol, ethanol, and tri- n-butyl phosphate. In some cases, when the solvent in the feed solution (dilute) is a mixture of organic solvent and water, water does not act as the principal solvent.

[0023] The present disclosure relates to a process and a system for extracting one or more metals from waste mixtures. The process and system integrate organic solvent electrodialysis with an organic solvent-based metal leaching process to efficiently recover critical metals and noble metals from the waste mixtures. The process and system enable chemical-free, efficient, and highly selective separation and recovery of metals dissolved in organic solvent including deep eutectic solvent (DES). Consequently, the process and the system not only ensure efficient and selective metal recovery from waste mixtures but also enhance the reusability of the organic solvent within the waste recovery process.

[0024] In a first aspect, the process comprises extracting one or more metals from a waste mixture comprising one or more recoverable metals using a metal extraction process and an organic solvent electrodialysis process. The processes comprise the steps of: contacting the waste mixture with an organic solvent comprising a deep eutectic solvent for metal extraction to obtain a metal-containing feed solution; subjecting the metal-containing feed solution to electrodialysis to separate one or more metal ions from the metal -containing feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution

[0025] Deep eutectic solvent is a type of solvent made from a mixture of two or more components, with a melting point much lower than that of the individual components. The deep eutectic solvents employed in the present disclosure comprise metal-free and biodegradable substances, serving as hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). In various embodiments, the deep eutectic solvent comprises a hydrogen bond acceptor selected from the group consisting of quaternary ammonium salts such as choline chloride, tetrabutylammonium chloride, and guanidine hydrochloride, and non-ionic compounds including menthol, glycine, thymol and trioctylphosphine oxide; and a hydrogen bond donor selected from the group consisting of amides, carboxylic acids and alcohols, including urea, thiourea, glycerol, ethylene glycol, oxalic acid, lactic acid, citric acid, tartaric acid and thymol.

[0026] The composition of the deep eutectic solvent can be tailored according to the specific properties of the target metals to be recovered from different types of electronic waste mixtures. In some exemplary embodiments, a deep eutectic solvent comprising choline chloride (ChCl) and lactic acid (LA) may be employed for recovering lithium (Li) and manganese (Mn) from cathode material (lithium nickel manganese cobalt oxide (NMC)) in spent lithium-ion batteries. In these embodiments, the choline chloride and the lactic acid may be in a molar ratio of 1 :2. In other exemplary embodiments, a deep eutectic solvent comprising choline chloride and ethylene glycol in a molar ratio of 1:2 may be employed for extracting lead (Pb) from spent lead-acid batteries. In further exemplary embodiments, a deep eutectic solvent comprising guanidine hydrochloride and lactic acid in a molar ratio of 1 :2 may be employed for recovery of rare earth elements, such as neodymium, from end-of-life permanent magnets.

[0027] FIG. 1 is a schematic illustration of a process and a system 100 for extracting one or more metals from a waste mixture. The process initiates in a metal extraction unit 102 where the waste mixture containing metals 104 is mixed with the deep eutectic solvent 106 in a reaction tank 108. The parameters such as temperature, reaction time, stirring rate, and theweight ratio of the deep eutectic solvent to the waste mixture are controlled to optimize metal extraction efficiency and economic viability.

[0028] In certain embodiments, the temperature in the reaction tank 108 is adjusted from room temperature to 200°C, and the temperature is regulated by means of a heating jacket 110. The heating jacket may be supplied with a heat source selected from electricity, natural gas and industrial low-grade waste heat, or a combination thereof.

[0029] In certain embodiments, reaction time in the reaction tank 108 may range from 0.5 to 48 hours, depending on the properties of the waste mixture and the desired extraction efficiency. A stirrer 112 may be provided in the reaction tank 108 to agitate the waste mixture and the deep eutectic solvent at a stirring rate from 10 to 1000 rpm. The weight ratio of the deep eutectic solvent to the waste mixture may range from 1 :1 to 100: 1, expressed as kilograms of deep eutectic solvent per kilogram of waste mixture.

[0030] At least one sensor 114 is installed in the reaction tank 108 to monitor vital parameters of the reaction process, such as temperature, pH, and conductivity, to ensure optimal operation conditions. The deep eutectic solvent dissolves the target metals from the waste mixture, resulting in a metal-containing feed solution This solution discharges from the reaction tank 108 and feeds into an organic solvent electrodialysis unit 116.

[0031] The organic solvent electrodialysis unit 116 may comprise one or more electrodialysis stacks. The metal-containing feed solution is introduced into a feed solution (dilute) chamber 118 contained in the electroloysis stack, where the metal -containing feed solution undergoes electrodialysis to separate one or more target metal ions by selective ions migration within the organic solvent electrodialysis unit. Driven by an applied electric field, the target metal ions migrate through an ion exchange membrane within the electrodialysis stack 120 into an adjacent metal recovery solution (concentrate) chamber 122, in which a metal recovery solution 124 is recirculated to enrich the target metal ions originating from the feed solution (dilute) chamber 1 18. After a number of cycles, the enriched metal recovery solutionis collected and subjected to further processing to recover the one or more target metals. The residual deep eutectic solvent (DES) solution remaining in the feed solution (dilute) chamber 118 is discharged and recycled back via a pipeline 128 into the reaction tank 108, where it may be reused for extracting metals from subsequent batches of waste mixtures.

[0032] In various embodiments, the one or more target metals to be recovered are noble metals, critical metals or a combination thereof. In some embodiments, the noble metals are selected from the group consisting of gold, silver, platinum and palladium. In some embodiments, the critical metals are selected from the group consisting of lithium, manganese, cobalt, nickel, iron, aluminium, magnesium, sodium, copper, tin, antimony, bismuth, indium, gallium, and rare earth elements including neodymium, dysprosium, terbium, yttrium, and europium.

[0033] Any suitable metal recovery solution may be employed without departing from the scope of the present disclosure. Examples of metal recovery solutions, also known as stripping solutions, include, but are not limited to, acidic solutions such as hydrochloric acid (HC1), nitric acid (HNO3), or sulfuric acid (H2SO4). Alternatively, clean aqueous salt solutions may be employed, such as lithium salt solutions (e g., lithium chloride (LiCl), lithium sulfate (Li2SO4), lithium nitrate (LiNCh), etc.) for lithium recovery, cobalt(II) salt solutions (e.g., cobalt chloride (C0CI2), cobalt sulfate (CoSO4), cobalt nitrate (Co(NO3)2), etc.) for cobalt recovery, and other metal salt solutions for the recovery of respective metals. Alternatively, other solvents suitable for receiving the target metal ions to achieve high purity and concentration may be employed, including, but not limited to, deep eutectic solvents, ionic liquids, and other organic solvents including, but not limited to, ethylene glycol, polyethylene glycol, methanol, ethanol and tri-n- butyl phosphate The selection of the metal recovery solution is dependent on the one or more metals to be recovered and the downstream application requirements.

[0034] In some embodiments, the metal recovery solution 124 may be subjected to further processing through a post-concentration unit 126 to increase the concentration of the targetmetal ions (e.g., Li+, Co2+, Ni2+, Mn2+, etc), thereby ensuring that the concentrations meet the specific requirements for the final recovered metal products.

[0035] In some embodiments, the metal-containing feed solution from the reaction tank 108 may be subjected to one or more pretreatment steps prior to feeding into the organic solvent electrodialysis unit 116. The pretreatment steps may include, but are not limited to, sedimentation, centrifugation, filtration, and chemical precipitation. The purpose of these pretreatment steps is to remove insoluble solid residues and to selectively eliminate specific dissolved substances, such as organic compounds and impurity metals, thereby enhancing the efficiency and sustainability of the subsequent electrolysis process.

[0036] FIG. 2A is a schematic illustration of the structure and configuration of the organic solvent electrodialysis unit referred to in FIG. 1 The organic solvent electrodialysis unit 200 comprises one or more electrodialysis stacks 201. The electrodialysis stack 201 comprises an anode 202, a cathode 203, and four distinct types of chambers, namely, feed solution chambers 204, metal recovery solution chambers 205, mediating solution chambers 206, and electrode chambers 208, 208'. These chambers are separated by ion-exchange membranes, which consist of anion exchange membranes (AEM, 210) and cation exchange membranes (CEM, 212), alternately arranged within the electrodialysis stack 201 for selectively separating the one or more metal ions from the metal -containing feed solution. Depending on the scale of the organic solvent electrodialysis unit 200, the feed solution chamber (i.e., dilute chamber) and the metal recovery solution chamber (i.e., concentration chamber) adjacent to the feed solution chamber form a repeating unit 214 Multiple such repeating units may be arranged in the electrodialysis stack to achieve more ion transport within the same time period.

[0037] In various embodiments, the electrodialysis stack 201 comprises one or more feed solution chambers 204 configured to receive the metal-containing feed solution 216, each of the feed solution chambers being disposed between one AEM and one CEM. The electrodialysis stack 201 further includes one or more metal recovery solution chambers 205 configured toreceive the metal recovery solution 218, each of the metal recovery solution chambers being disposed between one AEM and one CEM, and positioned adjacent to the feed solution chambers 204. The electrodialysis stack 201 also comprises a first mediating solution chamber 206 disposed between a first pair of the AEM and the CEM, a second mediating solution chamber 206' disposed between a last pair of the AEM and the CEM, a first electrode chamber 208 disposed between the cathode and the one CEM adjacent the cathode, and a second electrode chamber 208' disposed between the anode and one CEM adjacent the anode.

[0038] Each of the mediating solution chambers 206, 206' is configured adjacent to a corresponding electrode chamber 208, 208' to prevent the target metal ions from leaking into the electrode chambers. Each of the mediating solution chambers shares the same CEM with the corresponding electrode chamber and shares the same AME with the corresponding metal recovery solution chamber positioned next to it. The mediating solution contains the same cation as the electrode solution, preferably free of divalent cations.

[0039] CEMs allow cations to migrate under applied electric field while blocking the passage of anions. Conversely, AEMs permit the transport of anions while preventing the passage of cations.

[0040] In some embodiments, the CEMs may be fabricated from perfluorinated sulfonic acid polymers, sulfonated polystyrene, sulfonated polyethylene, sulfonated poly(ether ether ketone), and the like. The AEMs may be formed from quaternary ammonium-functionalized polymers, such as quaternary ammonium-functionalized polystyrene, cross-linked polyethylene membranes incorporating quaternary ammonium groups, and polyvinyl chloride copolymers with quaternary ammonium functionalities. Furthermore, selective ion-exchange membranes, including monovalent selective CEMs or AEMs, may also be employed in the electrodialysis stack to achieve selective separation of specific metal ions or charged species from the metalcontaining feed solution. Monovalent selective CEMs may be employed to selectively separate monovalent cations, which preferably allow the transport of monovalent cations through themwhile retaining multivalent cations, large positively charged species, anions and neutral species / molecules. Monovalent selective AEMs may be employed to selectively separate monovalent anions, which preferably allow the transport of monovalent anions through them while rejecting multivalent anions, large negatively charged species, cations and neutral species / molecules.

[0041] In some embodiments, when an external electric field is applied to the organic solvent electrodialysis unit, monovalent ions in the one or more feed solution chambers selectively migrate through the adjacent CEM into the one or more metal recovery solution chambers, and multivalent ions in the one or more feed solution chambers are retained in the metal-containing feed solution.

[0042] In some embodiments, the metal-containing feed solution 216 is introduced into the feed solution chambers 204 through a feed solution pipeline 220. Other solutions such as the metal recovery solution 218, electrode solutions in the electrode chambers 208, and the mediating solution 222 are circulated through their respective chambers in each electrodialysis stack using pumps and corresponding pipelines.

[0043] As mentioned hereinabove, the selection of the metal recovery solution is dependent on the one or more metals to be recovered and the downstream application requirements. In some exemplary embodiments where lithium is to be recovered, the metal recovery solution 218 is an aqueous salt solution containing the target metal ions and corresponding anion ions, such as lithium chloride solution, lithium sulfate solution, lithium nitrate solution, or the like.

[0044] The electrode solution should be highly ionic conductive, chemically stable and non- reactive with the electrodes. In some embodiments, the electrode solution comprises sodium sulfate (Na2SO4), which is commonly employed as an electrode solution in electrodialysis process.

[0045] Mediating solution 222 is employed to prevent leakage of specific metal ions into the electrode solution and to protect the electrodes from alkaline scaling in the electrodialysisstack. The cations in the mediating solution 222 should be the same as those in the electrode solution, while the anions are aligned with those in the metal recovery solution or the metalcontaining feed solution. For example, the electrode solution may comprise a sodium sulfate (NazSCH) solution, and the mediating solution may comprise a sodium chloride (NaCl) solution. This arrangement ensures stable and efficient ion exchange in the electrode chamber 208.

[0046] n various embodiments, when driven by an applied electric field from an external power source 224, the positively charged target metal ions (depicted as spheres labelled “M” in FIG. 2A) in the metal-containing feed solution contained in the feed solution chamber 204 migrate towards the cathode 203. The positively charged target metal ions pass through the CEM 212, and concentrate in the metal recovery solution 218 contained in the metal recovery solution chamber 205. When a monovalent selective CEM is employed, only monovalent cation (e.g., Li+) will transport through the CEM while rejecting the majority of other species such as multivalent cations, large charged species, and anions. Conversely, the anions in the metalcontaining feed solution 216 contained in the feed solution chamber 204 move towards the anode 202, pass through the AEM 210, and enter either the metal recovery solution 218 in the metal recovery solution chamber 205 or the mediating solution 222 in the mediating solution chamber 206' for charge balance. The major components of the deep eutectic solvent are largely rejected by the ion exchange membranes and retained within the feed solution chamber 204. The metal recovery solutions in the metal recovery solution chambers 205 are recirculated via a pipeline 226 to enrich the target metal ions originating from the feed solution chamber 204. After a few cycles and upon reaching the desired recovery efficiency, the enriched metal recovery solution is discharged from the electrodialysis stack, collected and subjected to further processing to recover the one or more target metals from the enriched metal recovery solution. The solution containing the organic solvent with a lower metal content exits from the feed solution chambers 204 to be collected in a tank 228, ready to be recycled back into the systemor the metal extraction unit for use in subsequent metal extraction cycle, thereby forming a closed-loop recovery pathway for the process.

[0047] In some embodiments, the mediating solution 222 exiting from the mediating solution chambers 206 are recycled back into the electrodialysis stack via a pipeline 230.

[0048] The operating conditions of the organic solvent electrodialysis unit, including the solution circulation rate, applied current density (5-60 m A / cm2), and the duration that the deep eutectic solvent stays within the organic solvent electrodialysis unit, may be adjusted to meet the specific requirements of various application scenarios.

[0049] In various embodiments, the process may further include additional processes or technologies including, but not limited to, centrifugation, precipitation, one or more additional organic solvent electrodialysis units, and solvent / water extraction. In some embodiments, such processes or technologies are integrated into the metal recovery process to enhance the efficiency of metal extraction and to improve the purity of the final metal products recovered from different types of waste mixtures. In some embodiments, the one or more metals are recovered from the metal recovery solution by precipitation.

[0050] FIG. 3A is a schematic illustration of a centrifugation unit 301 that may be employed in the organic solvent electrodialysis process. Centrifugation may be employed for rapid and effective separation of the metal-containing feed solution from solid residues. Any suitable centrifugation speed may be employed for the separation. In some embodiments, the centrifugation speed ranges from 500 to 12,000 rpm. The centrifugation duration may range from 10 to 60 minutes.

[0051] FIG. 3B is a schematic illustration of a precipitation unit 302 that may be employed in the organic solvent electrodialysis process. The precipitation unit 302 may comprise a precipitation tank 303. After precipitation is completed, the resulting metal-containing precipitates may be discharged at the outlet indicated as 304. Precipitation involves introducing one or more reagents into electronic liquid waste to induce the formation of solid precipitatesof specific metals. Examples of suitable precipitation reagents include, but are not limited to, oxalic acid, ammonia, sodium hydroxide, sodium carbonate and ammonia carbonate. This method is advantageous due to its cost-effectiveness and simplicity and allows for selective recovery of metals while improving the purity of the recovered products by removing undesirable impurities.

[0052] FIG. 3C is a schematic illustration of an additional organic solvent electrodialysis unit 305. The unit may comprise an electrodialysis stack including at least one repeating unit 306. Metal recovery solutions are collected at point 307. By incorporating an additional organic solvent electrodialysis unit 305, the process may be configured to target different metals within the metal-containing feed solution by employing ion-exchange membranes with different selectivities, thereby enabling high performance in the separation and recovery of multiple metals.

[0053] FIG. 3D is a schematic illustration of a solvent / water extraction unit 308. The solvent / water extraction unit may comprise an inlet 309 for receiving water or other solvents and a metal extraction tank 310. Solid residues remaining after the extraction process may be discharged through a solid flow line 31 1 (shown as a dashed line), while the liquid containing the extracted metals may be discharged through a liquid flow line 312 (shown as a solid line). In this technique, water or other suitable solvent is employed to selectively dissolve certain metals from the solid residues remaining after deep eutectic solvent extraction, thereby obtaining an aqueous leachate 313. Such an approach maximizes resource utilization and reduces waste generation.

[0054] Each of these technologies may be tailored to meet the specific requirements of different types of waste mixtures and the desired metal recovery outcomes, thereby making the overall process more flexible and efficient. By combining one or more of these processes, the organic solvent electrodialysis process may be optimized to achieve higher purity levels in therecovered metals, thereby enhancing the efficiency and economic viability of metal recovery from both solid and liquid waste streams.

[0055] FIG. 4 is a schematic illustration of potential post-concentration units (corresponding to unit 126 in FIG. 1) that may be employed to increase the concentration of metal products in the metal recovery solution. The post-concentration unit may include, but is not limited to, a membrane filtration such as nanofiltration or reverse osmosis (as depicted in FIG. 4(a)), or an additional organic solvent electrodialysis unit (as depicted in FIG. 4(b)).

[0056] The membrane filtration may be employed for selective concentration of metal ions from solution by utilizing semi-permeable membranes. Both nanofiltration and reverse osmosis membranes may be employed, depending on the target metal ions to be recovered. Nanofiltration membranes typically have pore sizes ranging from 1 to 20 nm, which makes them suitable for concentrating multivalent metal ions (e.g., Mn2+, Co2and Ni2+) in the solution. Nanofiltration may be operated at pressures ranging from 3 to 30 bar (i.e., 3 x 105Pa to 3 x 10sPa). Reverse osmosis membranes, which operate at higher pressures of 10 to 80 bar (i.e. 1 x 106Pa to 8 x 106Pa), have a tighter pore size of less than 1 nm, allowing for concentration of nearly all metal ions. The nanofiltration and reverse osmosis membranes may be semi-permeable and composed of polymeric, ceramic, or other inorganic materials, such as carbon materials, metals, or metal alloys, as well as nanomaterials, such as graphene, graphene oxide, reduced graphene oxide, metalorganic frameworks, covalent organic frameworks, or the like. These membranes may be configured as integrally structured asymmetric membranes, thin-film composite membranes, orthin-film nanocomposite membranes. The membranes may be provided in various forms including, but not limited to, flat sheet membranes, tubular membranes, and hollow fiber membranes. Advantageously, the rejection rates of the nanofiltration and reverse osmosis membranes for the target metals are higher than 90%.

[0057] The additional organic solvent electrodialysis unit may be employed to further concentrate and purify the metal recovery solution. Ion-exchange membranes, including cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs), permit the migration of target metal ions from the dilute chamber to the concentrate chamber, thereby achieving a higher concentration of the target metals in the concentrated solution.

[0058] FIG. 5 is a schematic illustration of an exemplary embodiment of a system 500 which comprises the metal extraction unit 102 and the organic solvent electrodialysis unit 116 illustrated in FIG. 1, and which integrates additional processes and technologies such as centrifugation 502, precipitation 504 and solvent / water extraction process 506, for the extraction of metals from cathode materials 508 of spent lithium batteries 510. The cathode material used in this set-up is lithium nickel manganese cobalt oxide (LiNi0.5Mn0.3Co0.2O, NMC532), which includes nickel (Ni), cobalt (Co), and manganese (Mn). In this process, a deep eutectic solvent comprising choline chloride (ChCl) and lactic acid (LA) in a molar ratio of 1 :2 is used to extract the cathode materials.

[0059] In various embodiments, the cathode materials disassembled from spent lithium batteries are mixed with deep eutectic solvent 512 in a weight ratio of 90 kg / kg in the reaction tank 108 with stirring. The mixture is stirred at a temperature of 50 °C for 48 hours. In some embodiments, increasing the reaction temperature to 90 °C reduces the deep eutectic solvent to a solid material and in this form, the spent lithium batteries may be mixed with the solid material of the deep eutectic solvent in a weight ratio of 30 g of solid material to 1 g of spent lithium batteries, for a duration of 4 hours.

[0060] The spent lithium batteries and the deep eutectic solvent are mixed at a stirring speed of 30 to 100 rpm. After the metal extraction in the deep eutectic solvent is completed, centrifugation 502 is employed to separate the DES liquid leachate or the metal -containing feed solution from solid residues.

[0061] In some embodiments, the metal -containing feed solution may be fed directly into the organic solvent electrodialysis unit 116, as illustrated at reference numeral 514 in FIG. 5. In other embodiments, the metal-containing feed solution may be subjected to precipitation ina precipitation unit 504 prior to introduction into the organic solvent electrodialysis unit 116. Any suitable precipitating agent may be employed to selectively obtain the target metals in solid form 516. In one exemplary embodiment, manganese (Mn) is predominantly recovered in the solid precipitate from the precipitation unit 504.

[0062] The metal-containing feed solution is introduced into the feed solution chamber of the organic solvent electrodialysis unit. The solutions employed in the organic solvent electrodialysis unit include a metal recovery solution of LiCl aqueous solution (10-100 mmol / L), an intermediate solution of sodium chloride (NaCl) aqueous solution (10-300 mmol / L), and an electrode solution of sodium sulfate (ISfeSCL) aqueous solution (100-500 mmol / L). The applied current density ranges from 3 to 10 niA / cm2based on the effective area of the individual ion-exchange membrane in the electrodialysis stack. Two types of cationexchange membranes (CEMs) are utilized: 1) monovalent selective CEMs, which allow the passage of monovalent cations (such as Li ions) while rejecting the multivalent cations such as Mn and Co ions; and 2) standard CEMs, which permit all cations but exclude anions. Standard anion exchange membranes (AEMs), which allow anion passage while excluding cations, are also used. After selectively separating Li ions, the solution containing the organic solvent is recycled (as illustrated at reference numeral 518) for further metal extraction from a new batch of cathode materials from spent lithium batteries. After several cycles, Li ions accumulate in the metal recovery solution 124, while other multivalent ions mainly remain in the solution containing the organic solvent contained in the feed solution chamber of the electrodialysis stack. After every 3 to 5 cycles, a precipitation process using solid oxalic acid powder as precipitant is employed to precipitate the multivalent ions from the solution containing the organic solvent before it re-enters into the electrodialysis stack. The precipitant dosage is based on a molar ratio of oxalic acid to multivalent ions dissolved in the solution containing the organic solvent, which ranges from 1:1 to 2: 1, with a mixing duration ranging from 30 to 180 minutes and a settlement duration ranging from 30 to 60 minutes.

[0063] Nickel (Ni) remains in the solid residues after centrifugation of the metal-containing feed solution. Since the Ni-containing compounds present in the solid residues are water- soluble, they may be subsequently extracted by a water extraction process using, for example, deionized water. In some embodiments, deionized water 521 and the solid residues 522 are introduced into the solvent / water extraction unit 506 in a weight ratio of water to solid residues of 10:90, and for a duration of 4 to 24 hours for extraction. Aqueous leachate 520 is obtained and it may be further processed to recover nickel (Ni). The remaining residues 523 are discharged from the solvent / water extraction unit. Ultimately, critical metals, such as lithium (Li), manganese (Mn), nickel (Ni), and cobalt (Co), are recovered in three final products generated from the abovementioned process: lithium (Li) in the metal recovery solution, manganese (Mn) in the precipitate, and nickel (Ni) and most of cobalt (Co) in the aqueous leachate 520 from the water extraction process.

[0064] FIGS. 6A to 6E are bar charts showing the results of the process depicted in FIG. 5.

[0065] FIG. 6A is a bar chart showing the results of metal recovery from the precipitation unit. The bar chart shows that manganese (Mn) was predominantly recovered in the solid precipitate from the precipitation unit.

[0066] FIG. 6B is a bar chart showing the results of metal recovery from the water washing extraction unit. The bar chart shows that nickel (Ni) and cobalt (Co) were primarily recovered in the aqueous solution from the water washing extraction unit.

[0067] FIG. 6C is a bar chart showing the results of metal recovery from the electrodialysis unit The bar chart shows that lithium (Li) was recovered with high purity (of more than 95%) in the aqueous solution from the organic solvent electrodialysis unit.

[0068] FIG. 6D illustrates that the organic solvent electrodialysis process effectively regenerates deep eutectic solvent, and the regenerated deep eutectic solvent can achieve similar or even higher metal extraction amounts (especially for Ni, Mn, Li) compared to fresh deep eutectic solvent.

[0069] FIG. 6E shows the overall recovery efficiencies, defined as the percentage of each metal recovered in the three final products relative to their total amount in the original cathode material. The process achieves a recovery efficiency of over 90% for Li and approximately 60% for Mn, Ni, and Co from NMC532 cathode materials of spent lithium batteries. By running the deep eutectic solvent extraction and organic solvent electrodialysis separation for multiple cycles, it is expected that the recovery rate for all the metals from batteries could be even higher, for example, lithium (Li) recovery rate could be close to 99% to 100% and the recovery of cobalt (Co), nickel (Ni) and manganese (Mn) could be more than 90%.

[0070] In a second aspect, a system for extracting one or more metals from a waste mixture is provided. Referring to FIG. 1, the system comprises a reaction tank for receiving an organic solvent and a waste mixture comprising one or more recoverable metals for metal extraction to obtain a metal-containing feed solution; and an organic solvent electrodialysis unit in fluid communication with the reaction tank. The organic solvent electrodialysis unit comprises one or more electrodialysis stacks comprising an anode; a cathode; and one or more anion exchange membranes (AEMs) and one or more cation exchange membranes (CEMs) arranged alternately, for selective separation of one or more metal ions from the metal -containing feed solution. The system further comprises a first tank in fluid communication with the organic solvent electrodialysis unit, for receiving and discharging a metal recovery solution; and a second tank in fluid communication with the organic solvent electrodialysis unit and the reaction tank, for receiving a solution containing the organic solvent from the organic solvent electrodialysis unit and discharging the solution containing the organic solvent to the reaction tank, thereby forming a closed-loop system.

[0071] The system may further include a third tank in fluid communication with the organic solvent electrodialysis unit for discharging and receiving a mediating solution into and from the organic solvent electrodialysis unit.

[0072] In some embodiments, the one or more electrodialysis stacks further comprises one or more feed solution chambers, each of the feed solution chambers being disposed between one AEM and one CEM, and one or more metal recovery solution chambers, each of the metal recovery solution chambers being disposed between one AEM and one CEM and positioned adjacent to the feed solution chambers. The electrodialysis stack may further include a first mediating solution chamber disposed between a first pair of the AEM and the CEM, a second mediating solution chamber disposed between a last pair of the AEM and the CEM, a first electrode chamber disposed between the cathode and one CEM adjacent the cathode; and a second electrode chamber disposed between the anode and one CEM adjacent the anode.

[0073] In some embodiments, the system may further include one or more units configured to enhance metal separation and purification, wherein the one or more units are selected from the group consisting of: a centrifugation unit, configured to separate solid residues from the metal-containing feed solution; a precipitation unit, configured to form and collect metalcontaining precipitates; an additional electrodialysis unit, for further separation of the one or more metal ions from the metal -containing feed solution; and a solvent or water extraction unit, configured to extract the one or more metals from the solid residues.

[0074] In various embodiments, the organic solvent to be employed in the system of the present disclosure comprises a deep eutectic solvent.

[0075] In some embodiments, the organic solvent to be employed is selected from the group consisting of ionic liquids, and other organic solvents including, but not limited to, ethylene glycol, polyethylene glycol, methanol, ethanol and tri-n-butyl phosphate.

[0076] Various configurations of the system may be employed by tailoring the processes and technologies to meet the specific requirements of different types of waste mixtures and the desired metal recovery outcomes. Such configurational flexibility enables the system to achieve improved efficiency, higher purity levels of the recovered metals, and greater adaptability across diverse waste streams, thereby enhancing both sustainability and economic viability.

[0077] In some embodiments, the process of the present disclosure may be employed for use with other organic solvents, including ionic liquids, and other organic solvents including, but not limited to, ethylene glycol, polyethylene glycol, methanol, ethanol and tri-n-butyl phosphate. The selection of the solvent is based on the solubility and selectivity for the one or more metals to be extracted.

[0078] Tn various embodiments, the process comprises extracting one or more metals from a waste mixture comprising one or more recoverable metal using a metal extraction process and an organic solvent electrodialysis process, the processes comprise contacting the waste mixture with an organic solvent to obtain a metal -containing feed solution; subjecting the metalcontaining feed solution to electrodialysis to separate one or more metal ions from the metalcontaining feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution, wherein the organic solvent is selected from the group consisting of ionic liquids, and other organic solvents including, but not limited to, ethylene glycol, polyethylene glycol, methanol, ethanol and tri-n-butyl phosphate.

[0079] The present disclosure addresses existing limitations in the field of electronic waste recycling and metal recovery by providing a process that enables the effective utilization of deep eutectic solvents and other organic solvents, while enhancing overall process sustainability. A key innovation in the disclosed process is the application of organic solvent electrodialysis for both metal recovery and regeneration of deep eutectic solvents and other organic solvents, thereby enabling reuse of the solvents within the process. The process preserve the solvents integrity for repeated reuse, and this approach establishes a truly closed loop and sustainable pathway for metal recovery from waste mixtures. This regeneration step not only ensures high efficiency in metal recovery but also significantly improves solvents utilization and enhances the overall sustainability of the process. In addition, the deep eutecticsolvents, which are synthesized from economical and biodegradable materials, further reduces the environmental impact of the process.

[0080] The process and system of the present disclosure are versatile and adaptable. Such versatility and adaptability are achieved through the combined application of organic solvent electrodialysis and tailored deep eutectic solvent systems or other organic solvents systems. The organic solvent electrodialysis process enables selective metal separation and purification by employing different ion-selective exchange membranes. Additionally, by tuning the composition of the deep eutectic solvents and other organic solvents, and optimizing the operational parameters of the extraction process, the disclosed process and system allow for highly efficient recovery of specific target metals from a wide variety of waste materials. This adaptability renders the process highly effective for recovering metals from diverse solid and liquid waste streams, while achieving high extraction efficiency.

[0081] Further, the process and system of the present disclosure enable the selective recovery of metals and provide high-quality recovered metal products. The recovered metals may achieve high purity in the final products, benefiting from the high selectivity of the electrodialysis process for metal separation. Tn addition, the use of the deep eutectic solvents facilitates selective and sequential extraction of heavy metals from solid waste materials, thereby tailoring the process to specific recovery requirements. The high purity and selectivity of metal recovery may be further enhanced by integrating additional purification processes, such as precipitation, solvent / water extraction, or other suitable techniques. Such selective extraction not only increases overall efficiency, but also ensures that the recovered metals possess sufficient purity for high-value applications, thereby maximizing the utility and marketability of the recycled metal products.

[0082] The process and system of the present disclosure operate under mild and adaptable operating conditions. The operating conditions of the entire process are mild, with temperatures below 100 °C, at ambient pressure. These conditions may be easily adjusted and optimized toachieve higher performance in different scenarios. Additionally, the relatively low operating costs and reduced carbon footprint of the process make it an environmentally and economically sustainable option for metal recovery from waste materials.

[0083] The process and system of the present disclosure may be applied to several industries including, but not limited to, battery recycling industry, waste management in manufacturing industry, such as pharmaceutical industry, environmental remediation, and raw material suppliers.

[0084] In some embodiments, the disclosed technology provides a more sustainable and cost-effective process for recycling, for example, spent lithium batteries, which is particularly appealing to the rapidly growing electric vehicle market. By enabling the recovery of valuable metals such as lithium, nickel, manganese, and cobalt, the process supports the manufacture of new batteries and reduces the reliance on primary mining resources. This approach is consistent with global initiatives directed toward promoting a circular economy within the battery supply chain.

[0085] The disclosed technologies offer a sustainable approach for managing solid wastes in various manufacturing sectors, including the pharmaceutical industry. For example, the process and system of the present disclosure may be applied to recover valuable metals from spent catalysts used in pharmaceutical manufacturing. Such an application reduces waste generation and enables recycling of precious resources, thereby enhancing sustainability within industrial processes.

[0086] The process of the present disclosure may also be adapted for environmental remediation projects in which heavy metals are removed from contaminated sites. The selectivity and adaptability of the organic solvent electrodialysis process make it suitable for extracting specific contaminants efficiently, thereby minimizing environmental impact relative to conventional remediation methods. In addition, companies that supply metal materials may employ the disclosed technology to produce high-purity metals from recycled sources. Such anapproach not only enhances the value of their product offerings but also provides a competitive advantage by promoting sustainability within their operations.

[0087] To facilitate a better understanding of the invention, the following examples of specific embodiments are given. In no way should the following examples be read to limit or define the entire scope of the invention. One skilled in the art will recognize that the examples set out hereinbelow are not an exhaustive list of the embodiments of this inventionEXAMPLESExample 1

[0088] Leaching process of ternary cathode materials

[0089] NCM532 powder was added into a deep eutectic solvent comprising choline chloride (ChCl) and lactic acid (LA) with a molar ratio of 1 :2, at a liquid-to-solid weight ratio (L / S) of 30 g / g. The mixture was kept at a constant temperature of 90 °C with continuous stirring for 4 hours. ChCLLA (1 :2) deep eutectic solvent was selected as the leaching solvent for NMC532 due to its strong selectivity towards lithium, while minimizing the co-dissolution of cobalt and nickel, which were reprecipitated in solid residues during the leaching process. Although manganese was co-extracted, the overall selectivity of ChCkLA facilitates downstream lithium separation and enhances the potential for deep eutectic solvent reuse. The DES leachate was separated from residual solid through centrifugation (3700 rpm, Kubota Corporation) and collected for subsequent processing by SED. The metal concentrations in the DES leachates after the leaching of NMC532 were as follows: Mn (3.36 ± 0.94 g / kg), Li (2.15 ± 0.05 g / kg), Co (0.90 ± 0.42 g / kg), and Ni (0.35 ± 0.03 g / kg).Example 2

[0090] Organic solvent electrodialysis unit for metal separation

[0091] Using FIG. 2A to illustrate the process of this example, the organic solvent electrodialysis unit 200 employed in this example comprises an electrodialysis stack 201 including four types of chambers: namely, feed solution chambers 204 (al so referred to as dilutechambers), metal recovery solution chambers 205 (also referred to as concentrate chambers), mediating solution chambers 206, and electrode chambers 208. These chambers are alternately separated by CEMs 212 and AEMs 210. A feed solution chamber and a metal recovery solution chamber formed a repeating unit in the electrodialysis stack. To prevent target metal ions from leaking into the electrode chambers 208, mediating solution chambers 206 were positioned between the repeating unit and the electrode chambers. Tn this example, a lab-scale electrodialysis stack comprising two repeating units, two mediating solution chambers and two electrode chambers was used. The total active membrane area for ion transport was 7.065 cm2. 32 g of the DES leachate from spent lithium batteries was pumped into the feed solution chambers 204 using a gear pump (Leadfluid CT3000F, China) at a constant flow rate of 20 mL / min, while 30 mL of aqueous LiCl solution with an initial concentration of 0.03 M was supplied as the metal recovery solution into the metal recovery solution chambers 205, at a flow rate of 20 mL / min. The electrolyte (0.3 M Na2SOi) and mediating solution (0. 1 M NaCl) were recirculated through the electrode chambers 208, 208' and the mediating solution chambers 206, 206', respectively. Titanium with mixed metal oxide coating electrodes were employed as the cathode 203 and the anode 202.

[0092] Before the experiment, all the solutions were circulated through their respective chambers for 1 h to stabilize the solutions The electrodialysis stack was operated in a galvanostatic mode, regulated by a direct current power supply (A-BF SS-L303SPD, China), and the voltage was recorded every 5 mins. The pH and electrical conductivity of all the solutions were monitored by pH meters (Mettler Toledo, USA) and electrical conductivity meters (Thermo Scientific Orion Star A212, USA). Samples were collected from the reservoirs of each solution at specified time intervals The concentrations of critical metals (i.e., Li, Mn, Co, and Ni) in all the samples were measured by inductively coupled plasma optical emission spectrometry (ICP-OES, Avio 550 Max, PerkinElmer).

[0093] The performance of the organic solvent electrodialysis process using CEM was assessed by ion transport rate and selectivity, which are defined as follows:

[0094] The ion transport rate (J;) quantifies the efficiency of ion migration through the membrane, expressed in mol / m2 / h, and is calculated as:An;Ji“ A - At (1)

[0095] where Ji is the ion transport rate, Am is the number of moles of ion transported, A is the effective membrane area (m2), and At is the time interval (h).

[0096] The selectivity in this example refers to the preferential separation of Li+over other metal ions M (e.g., Ni2+, Co2+, Mn2+) enriched in the metal recovery solution chamber can be calcul ted as:

[0097] are the initial and final molar concentration of metal ions M, Li+in the aqueous metal recovery solution (mol / L), respectively, Vcis the volume (L); C^oand C^oare the initial concentration of M cation and Li+in the metal-containing feed solution (mol / kg).

[0098] The separation factor in this example evaluates the separation performance of Li+over the cationic deep eutectic solvent components (i.e., choline ions (Ch+)), which is defined as the ratio of Li to Ch+ion transport rate (mol / m2 / h), divided by the ratio of their initial concentrations in the metal-containing feed solution (mol / kg):Example 3

[0099] Integrated organic solvent electrodialysis system

[0100] The integrated organic solvent electrodialysis system developed in this example is designed to enable selective separation and recovery of metals from the metal-containing feed solution (DES leachates) obtained by mixing deep eutectic solvent with the waste mixture, while facilitating solvent reuse.

[0101] In the overall process illustrated in FIG. 2A, metals were first leached from disassembled NMC-type cathode materials into a ChCl:LA DES lixiviant. This was carried out by the process described in Example 1. The metal-containing leachate that was separated and collected was then introduced into the organic solvent electrodialysis unit of Example 2. As described in Example 2, the organic solvent electrodialysis unit consists of feed solution chambers, metal recovery solution chambers, mediating solution chambers, and electrode chambers, which were separated by alternatively arranged AEMs and CEMs.

[0102] Metal-containing leachates containing lithium and other transition metals were introduced into the feed solution chambers, while a dilute aqueous LiCl solution serves as the lithium recovery solution on the cathode side. A mediating solution is used to isolate the electrode chambers, preventing undesired species from reaching the electrodes and minimizing side reactions.

[0103] FIG. 2B illustrates an exemplary embodiment of the proposed ion transport mechanism Under an externally applied electric field, the monovalent lithium ions (Li+) selectively migrated through the CEM into the aqueous lithium recovery stream (RS). In contrast, multivalent transition metals (e.g., Mn2+, Co2+, Ni2+) were rejected by the CEM and retained in the solution containing the organic solvent. Anions (e g., Cl’) migrated through the AEM toward the anode side to maintain charge balance. The solution containing the organic solvent after the organic solvent electrodialysis process, depleted of lithium, was collected and reused for subsequent metal leaching cycles, establishing a closed-loop recovery pathway for the hydrometallurgy process for upcycling of spent lithium batteries.

[0104] Experimental results demonstrated the selective separation of lithium from the DES leachate using SED. As shown in FIG. 7A, the highest mass concentration of metal ions in the initial deep eutectic solvent before organic solvent electrodialysis operation was Mn, followed by Li, and low concentrations of Co and Ni. As the organic solvent electrodialysis process progressed, the concentration of Li+in the deep eutectic solvent dropped steadily with time. On the other hand, the concentration of the other metal ions (i .e., Mn, Co, Ni) remained almost constant in the deep eutectic solvent, indicating the high rejection of the CEM to these multivalent transition ions. Simultaneously, Li+concentration in the aqueous recovery solution increased from 0.21 mg / L to approximately 2 g / L over 48 hours, achieving over 99% Li+purity (FIG. 7B). The minimal Mn2+accumulation (less than 0.03 g / L) and the negligible Co2+and Ni2+in the final recovery solution after 48 hours of operation further demonstrate the high selectivity of Li separation by organic solvent electrodialysis from deep eutectic solvent.

[0105] In FIG. 7C and FIG. 7D, the transport rate of metal ions in the organic solvent electrodialysis process and the selectivity of Li over other metal ions were calculated. The Li+transport rate from the deep eutectic solvent to the aqueous recovery solution could reach about 0.20 to 0.29 mol / m2 / h (which is steadily decreased over time), significantly higher than Mn2+at around 0.40 x 10'3mol / m2 / h, indicating that Li+transport was more than 500 times faster than Mn2+The transport rates of Co2+and Ni2+were even lower at 0.3 x 10'4mol / m2 / h and 0.2 x 10'4mol / m2 / h (FIG. 7C). The selectivity can reach over 110 for Li+over Mn2+, around 310 for Co2+, and 450 for Ni2+, calculated at the end of the organic solvent electrodialysis experiments (FIG. 7D).

[0106] The CEM employed in this example can achieve selective permeation of monovalent ions and effectively reject multivalent ions in aqueous systems, mainly through a size-exclusion mechanism. The dense selective layer on the CEM is engineered with pore sizes that fall between the hydrated diameters of monovalent and multivalent ions. This configuration allows larger multivalent cations, such as Ni2+, Co2+, and Mn2+, to be effectively rejected due to theirgreater hydrated radii and significantly higher dehydration energy requirements. As a result, the membrane exhibited good selectivity toward smaller and less strongly hydrated monovalent ions like Li+in aqueous environments

[0107] This example extended the application of organic solvent electrodialysis with CEMs to deep eutectic solvent system. Despite the different physicochemical characteristics of ChCLLA deep eutectic solvent compared to conventional aqueous systems, such as higher viscosity and organic contents, lower dielectric constant and stronger ion-solvent interaction, the experimental results demonstrated that the size-exclusion function of the CEM remains effective in deep eutectic solvent environments, as evidenced by the high selectivity of the smaller Li+over the larger multivalent metal ions. Moreover, the transport of multivalent cations Ni2+, Co2+, and Mn2+through the CEMs from the deep eutectic solvent phase still requires partial desolvation to enter small membrane pores at the membrane interface. These cations, which typically exhibit stronger electrostatic interactions and higher coordination numbers with deep eutectic solvent components (e.g., chloride or lactate anions), are subject to substantial energy barriers when entering small membrane pores. This further restricts their transport compared to Li1, thereby enhancing the membrane selectivity As a result, the observed selectivity of Li+over multivalent ions in deep eutectic solvent is comparable to that in aqueous systems, demonstrating the adaptability of organic solvent electrodialysis for selective monovalent ion separation from deep eutectic solvent.Example 4

[0108] Solvent reusability and membrane stability tests

[0109] The regenerated deep eutectic solvent after organic solvent electrodialysis process were evaluated for reusability in metal extraction by leaching fresh NMC532, following the procedure described in Example 1. The resulting leachate was separated from the solid residues by centrifugation and analyzed for metal concentrations by ICP-OES.

[0110] The multicycle stability of ion exchange membranes was assessed using organic solvent electrodialysis with DES leachate as feed solution over three consecutive cycles without membrane replacement. Each cycle followed the conditions and procedures specified in the Examples 1 and 2 regarding the organic solvent electrodialysis for metal separation.

[0111] To assess the long-term chemical stability of CEM and AEM in deep eutectic solvent, aging tests were conducted by immersing both ion exchange membranes in ChCkLA DES leachate, which was obtained after metal extraction from NMC532, for up to one month. The resistance and the transport number of the ion exchange membranes before and after the stability tests were also measured. The structural changes in the ion exchange membranes were further analyzed using Fourier transform infrared (FT-IR) spectroscopy (IRPrestige-21, Shimadzu) with 45 scans recorded in the range of 4000-800 cm'1at a resolution of 4 cm'1. Surface morphology was characterized via field-emission scanning electron microscopy (FESEM, JEOL-7200F, Japan), and elemental composition on the membrane surface was analyzed using energy-dispersive X-ray spectroscopy (EDX, Oxford Instruments Aztec Standard X-max 50, UK).Example 5

[0112] Multi-ionic transport in organic solvent electrodialysis

[0113] A multi-ionic transport model was developed to simulate species transport in organic solvent electrodialysis process with metal-containing feed solution. Before simulation, experiments were conducted at various current densities ranging from 0.75 to 12 mA / cm2. These were below the limiting current density (LCD) of the organic solvent electrodialysis system using deep eutectic solvent as the feed solution, which was estimated to be above 40 mA / crn2, and which was experimentally determined in advance to ensure all simulations and measurements were conducted within the ohmic regime. Ion fluxes were measured over 10 hours of organic solvent electrodialysis operation for metals and ions from deep eutectic solvent (e g., Ch+and lactate (Lac') ions) Metal concentrations were measured by ICP-OES, andcholine and lactate ions were measured using a total nitrogen (TN) / total organic carbon (TOC) analyser (TOC-L, Shimadzu, Japan).

[0114] The mechanistic models based on the Nernst -Planck (NP) framework were employed to describe species transport through ion-exchange membranes from deep eutectic solvent phase to aqueous phase in each organic solvent electrodialysis repeating unit. These models account for both diffusion and electromigration of ionic species under steady-state and isothermal conditions. Concentration polarization effects in the liquid streams were also considered, using mass transfer correlations specific to our experimental setup.

[0115] In the solution phase (i.e., the boundary layer between the bulk solution and the membrane surface), the ion flux Ji,sis described as:where Di,sis the diffusion coefficient of ion i in the solution phase; dci,s / dx and d<t>s / dx are the ion concentration and electric potential gradients across the boundary layer, respectively; z, is the ion valency; F, R and T are the faraday constant, universal gas constant and absolute temperature, respectively.

[0116] The ion flux through the membrane phase, Jmcan be described as:where the Di,mis the diffusion coefficient of ion 1 in the solution phase; dci m / dx and dfm / dx are the ion concentration and electric potential gradients through the membrane, respectively; Under quasi-equilibrium and low-current conditions (i « ium), ion transport in the membrane can be simplified by neglecting the concentration gradient term as the ion transport is dominated by electromigration.

[0117] These models enabled the calculation of species-specific fluxes as a function of applied current densities. Under steady-state conditions, ion flux continuity across the solutionmembrane interface can be achieved withThe models were first calibrated by fitting to experimental ion flux data for critical ions such as Li+, Mn2+, Ch+, and Lac", obtained from bench-scale organic solvent electrodialysis experiments across a range of current densities. From this regression, diffusion coefficients in both the deep eutectic solvent and membrane phases were determined for each ion. This regression ensured that the model accurately reflects the observed ion transport behaviour under the conditions tested. These calibrated parameters were then used to simulate ion fluxes across the full current density range (0.2-15 mA / cm2), enabling the prediction of species-specific ion transport behaviours, selectivity, and transport numbers under different operating conditions.Example 6

[0118] Cycling performance of the organic solvent electrodialysis process

[0119] Cycling tests were conducted to evaluate the long-term stability and durability of the CEM and AEM used in the organic solvent electrodialysis_process with DES leachates. The membranes operated continuously across three organic solvent electrodialysis_cycles, with a cumulative duration exceeding 144 hours. As shown in FIG. 8A, lithium concentrations in the recovery solution increased consistently across all three cycles, reaching about 2 g / L by the end of each. A minor rise in manganese concentrations was observed during the second and third cycles, increasing from about 0.02 g / L in the first cycle to over 0.03 g / L, which resulted in a slight decline in lithium / manganese selectivity (FIG. 8B). Nevertheless, both membranes maintained high separation performance throughout the tests, with lithium purity in the recovery solution ranging from 98% to 99%..

[0120] The reduction in selectivity observed in later cycles might be ascribed to the prolonged membrane exposure to the harsh deep eutectic solvent environment with high organic content and low pH. Such conditions may induce gradual material degradation or theaccumulation of organic species on the membrane surface, potentially hindering ion transport. This was confirmed by SEM analysis (FIGs. 10A to 10F), which revealed that the used CEM developed a roughened surface with visible deposits (FIGs. IOC and 10E), in contrast to the smooth and uniform surface of the pristine membranes (FIG. 10A), suggesting progressive surface fouling or interaction with DES components over time.

[0121] In contrast, the mAEM membranes (FIGs. 10B, 10D and 10F) maintained relatively consistent surface morphology regardless of treatment condition, indicating greater surface stability in the presence of DES.

[0122] The surface chemistry of the membranes were further characterized by EDX spectroscopy. EDX analysis (FIGs. 11A to 11D) further confirmed a significant increase in surface carbon content on the used CEM (FIG. 11B) compared to the pristine one (FIG 11 A), implying the accumulation of deep eutectic solvent components such as choline compounds or other DES constituents. In comparison, no significant morphological or elemental changes were observed on the AEM before (FIG. 11C) and after the cycling tests (FIG. HD), indicating a minimal detectable surface change of AEM under the tested conditions.

[0123] To further evaluate the long-term chemical stability of the CEM and AEM in deep eutectic solvent, ageing tests were performed by submerging both membranes in ChCl:LA DES leachate, after metal extraction from NMC532, for a duration of up to one month. FTIR analysis was employed to investigate any changes in their chemical structures after cycling and ageing tests. As shown in FIG. 8C, the FTIR spectrum of the three CEM (pristine and the ones after cycling and ageing tests) exhibited strong, sharp peaks at 1010, 1040, 1 190, and 1235 cm ', corresponding to the -SOsH groups (S-phenyl and three n(S-O) modes) associated with the sulfonic acid functional groups responsible for the fixed charges in CEM. These results indicate that the functional groups on CEM can retain after cycling and ageing tests in deep eutectic solvent. In the FTIR spectrum of AEM (FIG. 8D), peaks between 1400-1800 cm1correspond to vibrations of C=O, C=C, C=N, N=O, and C-NO2, which are commonly associated with thequaternary ammonium functionalities present AEM. These peaks were still present on the spectrums of AEM samples after both the cycling and ageing tests, indicating that the functional groups in AEM remained chemically stable in the deep eutectic solvent. Meanwhile, a slight change was observed in the FTIR spectrum of the aged AEM after one-month immersion in DES leachate, with the emergence of a new peak in the 1000-1200 cm'1region, which can be attributed to C-O-C stretching vibrations. This may indicate potential interactions between lactic acid and the AEM during month-long exposure, possibly involving adsorption or surface modification.

[0124] The resistance of pristine, used and aged CEM and AEM were also measured and shown in FIG. 8F and FIG. 8G. Generally, a slight increase in resistance was observed for both CEM and AEM after the cycling test and ageing test. This may be attributed to the adsorption of organic components of deep eutectic solvent onto the membrane surface after prolonged exposure to the deep eutectic solvent, which may obstruct the ion exchange sites and increase resistance. Overall, despite minor degradation and surface deposition observed on both CEM and AEM after prolonged exposure to deep eutectic solvent, their ion exchange functions were largely retained, and these changes would not significantly affect their separation performance in the organic solvent electrodialysis process.

[0125] The chemical integrity and metal extraction performance of the deep eutectic solvent after regeneration by the organic solvent electrodialysis process were evaluated to assess its reusability. FIG. 8E shows the results of FTIR analysis of the recycled deep eutectic solvent from the organic solvent electrodialysis process. The absorbance peaks at 1450 cm'1, 1750 cm' and 3200 cm'1correspond to C-N stretching, -COOH vibration, and -OH vibration, respectively, indicating the formation of hydrogen bonds between the nitrogen in the amine group of choline chloride and the hydrogen from the carboxyl group in lactic acid (O=C-O- H---N). The presence of these peaks in both fresh and recycled DES spectrum confirms that no significant structural degradation occurred in the recycled DES after the organic solventelectrodialysis process. The performance of the recycled DES for metal extraction from NMC532 was further assessed and compared to fresh deep eutectic solvent (FIG. 8H). Metal extraction contents using the recycled DES were normalized against those of fresh DES The recycled DES demonstrated comparable metal extraction performance, with normalized lithium and manganese extraction values ranging from 0.95 to 1.2. These results demonstrated that the deep eutectic solvent regenerated by the organic solvent electrodialysis_process can be effectively reused for subsequent metal extraction cycles from cathode materials in spent lithium batteries.Example 7

[0126] Ions transport behaviours associated with metal separation in organic solvent electrodialysis process

[0127] In this example, the transport behaviors of different ions in deep eutectic solvent during the organic solvent electrodialysis process were investigated. The electromigration of ions in the deep eutectic solvent was investigated through both experimental and modeling studies on the effects of current density on ion transport rates, selectivity, and solvent stability in SED.

[0128] It should be noted that all current densities investigated in this example are within the LCD of the system The LCD was experimentally determined to be higher than 40 mA / cm2for this DES organic solvent electrodialysis system. Operating within this range ensures that ion transport remains within a stable regime, avoiding unwanted effects such as water splitting or excessive ohmic losses.

[0129] Organic solvent electrodialysis demonstrated high selectivity for lithium separation from other metals in deep eutectic solvent at all tested current densities. Li exhibited transport rates more than 100 times higher than Mn within the range of 0.75 to 12 mA / cm2(FIG. 9A). The Li transport rate increased with current density from 0.75 to 3 mA / cm2, reaching a plateau of approximately 0.3 mol / m2 / h at 6 and 12 mA / cm2. In contrast, the Mn transport rate initiallyrose at low current densities (0.75-3 mA / cm2) but dropped sharply to below 5 x 10'4mol / m2 / h at higher current densities. Consequently, high Li / Mn selectivity was obtained from SED, ranging from around 30 to over 100 at elevated current densities (FIG 9B). Selective lithium transport was also observed over other transition metals (e.g., Co, Ni), as shown in SI. As a result, the Li purity in the final aqueous recovery solutions were all higher than 95%, and reached 99% at high current densities (more than 6 mA / cm2).

[0130] Despite the advantages of higher current density for selective lithium separation, a significant loss of deep eutectic solvent components (i.e., choline cations and lactate anions) into the metal recovery solution was also observed. As shown in FIG. 9C, the transport rate of choline ions through the CEM increased noticeably with increasing current density. A similar trend was observed for lactate anions, which migrated from the metal-containing feed solution to the aqueous solution through the AEM, especially under high current density conditions. This loss of the deep eutectic solvent components could compromise the long-term stability and recyclability of the deep eutectic solvent, raising the cost of solvent replenishment. These findings suggested the necessity to optimize operating conditions to minimize solvent loss while maintaining high lithium separation efficiency.

[0131] To further understand ion transport behaviour, a theoretical model based on the Nemst-Planck equation was developed to predict the transport rates of key ions under varying current densities. The predicted transport rates of Li+, Mn2+and Ch+are shown as dashed lines with 95% confidence bands in FIG. 9A and 9C (R2>0.85). A direct comparison between predicted and experimental transport rates is presented in FIG. 9D. The model predictions for most ions closely match the experimental values over the tested range of current densities, validating the reliability of the model simulation. However, a notable deviation is observed for Mn2+at higher current densities (>6 mA / cm2). This could be attributed to the elevated pH (>3) of the deep eutectic solvent after electrodialysis at high current densities, which could potentially lead to the part of precipitation of Mn species We also observed thedeposition / precipitation on the membranes or in the feed solution chamber after the testing. Since the model assumes dissolved ionic species, it cannot account for this phase transformation, resulting in an overestimation of Mn transport at high current density. Nevertheless, given that the transport rate of Mn is inherently over 100 times lower than that of other ions (Li- and Ch+), this deviation has a negligible impact on the overall interpretation and prediction of the ion transport behaviours by the model.

[0132] Analysis of the transport numbers of major ions in the system further indicated that the energy efficiency of Li“ separation from the deep eutectic solvent by organic solvent electrodialysis was higher at lower current densities (e.g., less than 3 mA / cm2). The transport numbers of cations (including Li+, Mn2+, and Ch+), were determined both experimentally and theoretically, as shown in FIG. 9E. The transport number of H3O+at different current densities could also be calculated accordingly. The results reveal a decreasing trend in the transport numbers of metal ions (Li+and Mn2+) with increasing current density, while cations of the deep eutectic solvent components (Ch+and H3O+) exhibit the opposite behaviour. Specifically, the transport number of Li+declines from approximately 0.5 at 0.75 mA / cm2to around 0.1 at the high current density range (6 to 12 mA / cm2). In contrast, Ch+and H3O+increase to over 0.2 and around 0.7, respectively, at high current densities. This shift indicates that a greater proportion of the applied electric current is carried by ions other than Li" (the target ion) at elevated current densities, reducing the energy efficiency of lithium separation in the organic solvent electrodialysis process.

[0133] The different transport behaviours of Li", Mn2+, and deep eutectic solvent components in the organic solvent electrodialysis process resulted from their different diffusion coefficients in both the deep eutectic solvent phase and the CEM. The diffusion coefficients in deep eutectic solvent solution and ion exchange membrane (i.e., Dsand Dm) for the major ions in the system were obtained via modelling simulations, as shown in FIG. 9F. Among the three cations, their diffusion coefficients in the deep eutectic solvent phase follow the trend: Ch” >Li+»Mn2+, while in the membrane phase, the order shifts to: Li+» Ch+« Mn2’. The relatively high diffusion coefficient of Li+in both the deep eutectic solvent and membrane phases contributed to its relatively high transport rate across the CEM. This, in turn, accounted for the high selectivity of Li over other metal ions such as Mn2+, which exhibited the lowest diffusion coefficient in both phases. However, the diffusion coefficient of Li+in the deep eutectic solvent phase is only slightly higher than that in the membrane, which limited its transport rate at higher current densities due to the more severe membrane surface polarization. This results in a plateau in Li+transport rate beyond 3 mA / cm2. The plateau is also attributed to the relatively low concentration of Li+in the deep eutectic solvent compared to the deep eutectic solvent components such as Ch+. Despite the extremely low diffusion coefficient of Ch+in the membrane, which favoured Li7Ch+separation (separation factor around 20-30), the high concentration of Ch"(> 3 mol / kg) and fast diffusion of Ch+ions in the deep eutectic solvent enable their continuous increased transport rate with increasing current density.

[0134] The diffusion coefficients ofLi+, Miff, and Ch+in the ChCLLA deep eutectic solvent phase (Ds) are closely related to their specific interactions with the deep eutectic solvent matrix, including hydrogen bonding, coordination, and electrostatic interactions (as shown in FIG 9G). Li+exhibited a moderate diffusion coefficient in deep eutectic solvent (about 1.81 - I O'11nff / s), which was significantly lower than that in aqueous solution (about 1.03 x 10'9m2 / s). This can be ascribed to the strong and persistent coordination with chloride anions and hydrogen bond donors such as the hydroxyl and carboxyl groups of lactic acid. This results in the formation of well-structured, solvated complexes (e g., [Li C1XLAX]) that restrict its mobility within the deep eutectic solvent environment. Furthermore, MD simulations and NMR studies confirm that Li+experiences a structure-diffusion mechanism rather than vehicular diffusion, requiring higher activation energy for transport due to “hopping” between tightly bound solvation sites. Mn2+, having a higher charge density than Li“, could form even more strongly coordinated complexes with both CL and lactate anions. Its higher electrostatic field strength led to more extensivecoordination numbers and stronger hydrogen bonding with surrounding solvent molecules, forming large and slow-moving solvation shells. This resulted in the lowest observed diffusion coefficient among the three cations. In contrast, Ch”, although significantly larger in size, exhibited the highest diffusion coefficient in the deep eutectic solvent phase. This behaviour resulted from the lower charge density of Ch+ions carried and their relatively weaker coordination with Cl or lactic acid molecules. Their interaction with the deep eutectic solvent matrix was dominantly governed by weaker and more transient hydrogen bonds. As a result, Ch“ experiences a more fluid vehicular diffusion mechanism with minimal energy barriers, enabling faster mobility within the deep eutectic solvent environment.

[0135] The diffusion coefficient (Dm) of the cations in the monovalent-selective CEM can be attributed to the combined effects of size exclusion and Donnan-type partitioning behaviour. The limited diffusion of divalent and multivalent cations (such as Mn2+) through the CEM with dense selective layer was caused by both size and Donnan-type exclusion due to their larger hydrated radius and high charges compared to the monovalent ions. Although Ch+is monovalent, its large hydrodynamic radius and bulky quaternary ammonium structure hinder its transport through the dense selective layer, which is typically engineered to favour the permeation of small monovalent ions. On the other hand, Li+, the small monovalent ion, can more readily partition into and diffuse through the CEM, exhibiting the highest diffusion coefficient compared to Ch“ and Mn2+.

[0136] Accordingly, the present disclosure introduces organic solvent electrodialysis as an integrated solution for separating valuable metals from waste mixtures using deep eutectic solvent, while simultaneously enabling closed-loop deep eutectic solvent regeneration and reuse. The integration of organic solvent electrodialysis as a chemical-free, membrane-based approach provides an efficient and sustainable route for recovering both critical metals, noble metals and deep eutectic or other green solvents. This integrated strategy offers significantenvironmental and operational advantages, and with further optimization, may reduce production costs and improve long-term stability in large-scale applications.

[0137] All examples described herein, whether of apparatus, methods, materials, or products, are presented for the purpose of illustration and to aid understanding, and are not intended to be limiting or exhaustive. Modifications may be made by one of ordinary skill in the art without departing from the scope of the claimed invention

Claims

Claims1. A process for extracting one or more metals from a waste mixture, the process comprising: extracting one or more metals from a waste mixture comprising one or more recoverable metals using a metal extraction process and an organic solvent electrodialysis process, the processes comprising: contacting the waste mixture with an organic solvent comprising a deep eutectic solvent (DES) for metal extraction to obtain a metal -containing feed solution; subjecting the metal-containing feed solution to electrodialysis to separate one or more metal ions from the metal -containing feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution.

2. The process of claim 1, wherein the step of electrodialysis comprises introducing the metal-containing feed solution into an organic solvent electrodialysis unit, wherein the one or more metal ions are separated from the metal-containing feed solution by selective ions migration within the organic solvent electrodialysis unit3. The process of claim 2, wherein the organic solvent electrodialysis unit comprises one ormore electrodialysis stacks, each of the electrodialysis stacks comprises an anode, a cathode, one or more anion exchange membranes (AEMs) and one or more cation exchange membranes (CEMs) arranged alternately, for selectively separating the one or more metal ions from the metal-containing feed solution.

4. The process of claim 3, wherein the one or more electrodialysis stacks further comprises: one or more feed solution chambers configured to receive the metal-containing feed solution, each of the feed solution chambers being disposed between one AEM and one CEM; one or more metal recovery solution chambers configured to receive the metal recovery solution, each of the metal recovery solution chambers being disposed between one AEM and one CEM, and positioned adj cent to the feed solution chambers; a first mediating solution chamber disposed between a first pair of the AEM and the CEM; a second mediating solution chamber disposed between a last pair of the AEM and the CEM; a first electrode chamber disposed between the cathode and one CEM adjacent to the cathode; and a second electrode chamber disposed between the anode and one CEM adjacent to the anode.

5. The process of claim 4, further comprising: applying an external electric field to the organic solvent electrodialysis unit to cause monovalent ions in the one or more feed solution chambers to selectively migrate through the adjacent CEM into the one or more metal recovery solution chambers, while retaining multivalent ions in the one or more feed solution chambers in the metal-containing feed solution.

6. The process of claim 1 or 4, further comprising: collecting a solution containing the organic solvent separated from the metal -containing feed solution and recycling the solution containing the organic solvent back into the metalextraction step for subsequent metal extraction cycles, thereby forming a closed-loop recovery pathway for the process.

7. The process of claim 1, wherein the one or more metals are selected from the group consisting of noble metals, critical metals and a combination thereof.

8. The process of claim 7, wherein the noble metals are selected from the group consisting of gold, silver, platinum and palladium.

9. The process of claim 7, wherein the critical metals are selected from the group consisting of lithium, manganese, cobalt, nickel, iron, aluminium, magnesium, sodium, copper, tin, antimony, bismuth, indium, gallium, and rare earth elements including neodymium, dysprosium, terbium, yttrium, and europium.

10. The process of claim 1, wherein the metal recovery solution contains a solvent selected based on the one or more metals to be recovered, for dissolving the one or more metals extracted from the metal-containing feed solution.

11. The process of claim 1, wherein the one or more metals are recovered from the metal recovery solution by employing one or more steps selected from the group consisting of centrifugation, precipitation, solvent or water extraction or a combination thereof, and electrodialysis.

12. The process of claim 1, further comprising: subjecting the metal-containing feed solution to one or more pretreatment steps to remove solid residues or impurities prior to subjecting the metal-containing feed solution toelectrodialysis, wherein the one or more pretreatment steps are selected from the group consisting of sedimentation, centrifugation, filtration and chemical precipitation.

13. The process of claim 1, further comprising: subjecting the metal-containing feed solution to precipitation to obtain a solid precipitate prior to subjecting the metal -containing feed solution to electrodialysis; and recovering the one or more metals from the solid precipitate.

14. The process of claim 1, wherein the deep eutectic solvent comprises: a hydrogen bond acceptor selected from the group consisting of quaternary ammonium salts such as choline chloride, tetrabutyl ammonium chloride, and guanidine hydrochloride, and non-ionic compounds including menthol, glycine, thymol and trioctylphosphine oxide; and a hydrogen bond donor selected from the group consisting of amides, carboxylic acids and alcohols, including urea, thiourea, glycerol, ethylene glycol, oxalic acid, lactic acid, citric acid, tartaric acid and thymol.

15. The process of claim 1 or 14, wherein the deep eutectic solvent comprises choline chloride and lactic acid in a molar ratio of 1 :2.

16. A process for extracting one or more metals from a waste mixture, the process comprising: extracting one or more metals from a waste mixture comprising one or more recoverable metals using a metal extraction process and an organic solvent electrodialysis process, the processes comprising: contacting the waste mixture with an organic solvent to obtain a metalcontaining feed solution;subjecting the metal-containing feed solution to electrodialysis to separate one or more metal ions from the metal -containing feed solution; contacting the one or more metal ions with a metal recovery solution; and collecting the metal recovery solution and recovering the one or more metals from the metal recovery solution, wherein the organic solvent is selected from the group consisting of ionic liquids, and other organic solvents.

17. A system for extracting one or more metals from a waste mixture, the system comprising: a reaction tank for receiving an organic solvent and a waste mixture comprising one or more recoverable metals for metal extraction to obtain a metal-containing feed solution; an organic solvent electrodialysis unit in fluid communication with the reaction tank, the organic solvent electrodialysis unit comprises one or more electrodialysis stacks comprising: an anode; a cathode; and one or more anion exchange membranes (AEMs) and one or more cation exchange membranes (CEMs) arranged alternately, for selective separation of one or more metal ions from the metal -containing feed solution; a first tank in fluid communication with the organic solvent electrodialysis unit, for receiving and discharging a metal recovery solution; and a second tank in fluid communication with the organic solvent electrodialysis unit and the reaction tank, for receiving a solution containing the organic solvent from the organic solvent electrodialysis unit and discharging the solution containing the organic solvent to the reaction tank, thereby forming a closed-loop system.

18. The system of claim 17, further comprising: a third tank in fluid communication with the organic solvent electrodialysis unit for discharging and receiving a mediating solution into and from the organic solvent electrodialysis unit.

19. The system of claim 17, wherein the one or more electrodialysis stacks further comprises: one or more feed solution chambers, each of the feed solution chambers being disposed between one AEM and one CEM; and one or more metal recovery solution chambers, each of the metal recovery solution chambers being disposed between one AEM and one CEM, and positioned adj cent to the feed solution chambers; a first mediating solution chamber disposed between a first pair of the AEM and the CEM; a second mediating solution chamber disposed between a last pair of the AEM and the CEM; a first electrode chamber disposed between the cathode and one CEM adjacent the cathode; and a second electrode chamber disposed between the anode and one CEM adjacent the anode.

20. The system of claim 17, further comprising one or more units configured to enhance metal separation and purification, wherein the one or more units are selected from the group consisting of:a centrifugation unit, configured to separate solid residues from the metal -containing feed solution; a precipitation unit, configured to form and collect metal-containing precipitates; an additional organic solvent electrodialysis unit, for further separation of the one or more metal ions from the metal -containing feed solution; and a solvent or water extraction unit, configured to extract the one or more metals from the solid residues.

21. The system of claim 17, wherein the organic solvent comprises a deep eutectic solvent.

22. The system of claim 17, wherein the organic solvent is selected from the group consisting of ionic liquids, and other organic solvents.

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