Process for membrane-based recycling of battery material

Abstract

The present disclosure relates to methods for recovering metals from used lithium-ion batteries and related electronic wastes. The methods provide modular, inexpensive, and energy efficient means for recovering up to 99.9% pure lithium, nickel, cobalt, and manganese in the form of various oxides or salts, e.g., phosphates, sulfates, or hydroxides. The methods produce nearly zero waste, as many of the recovered waste products can be purified and / or recycled.

Description

PROCESS FOR MEMBRANE-BASED RECYCLING OF BATTERY MATERIALCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of U.S. Provisional Application No. 63 / 510,873 Filed June 28, 2023, which is hereby incorporated by reference it its entirety.FIELD OF THE DISCLOSURE

[0002] The disclosure relates generally to methods for the extraction and enrichment of metals from batteries and other forms of electronic waste.BACKGROUND

[0003] Lithium ion batteries (LIBs) are widely used for various energy storage applications, ranging from consumer electronics to national defense. The growing popularity of hybrid and electric vehicles has led to a significant growth in the demand for LIBs, and the metals such as cobalt (Co), nickel (Ni), and lithium (Li) are critical components in LIB manufacturing. The U.S. Energy Information Administration projects that light-duty battery electric vehicles (BEV) sales in the U.S. will reach 1.3-3.43 million by 2025. Global electric vehicles (EV) sales are expected to increase from 1.1 million in 2017 to 30 million by 2030. The current state of the U.S. battery supply chain is inefficient both from a processing and logistics standpoint. One of the main challenges for the U.S. is lack of production capacity for battery materials such as Co, Li, Mn and Ni.

[0004] In recent years, the widespread applications of LIBs in portable electronic devices and hybrid / electric vehicles is expected to generate millions of tons of end-of-life (EOL) LIBs in future years. Over 5 million metric tons of LIBs are expected to reach EOL by 2030 which raises serious environmental concerns. These scrap LIBs could provide a secondary source of the critical battery materials with cost-effective recovery and recycling. However, because the LIB industry lacks a clear path to large scale recycling, there are no established technologies for LIB recycling and reuse.SUMMARY

[0005] This application describes methods for the recovery of valuable metals including cobalt, nickel, and lithium from used, refuse, waste LIBs and other electronic waste. The methodsinvolve pre-processing of used, refuse, waste LIBs and other electronic waste in order to obtain an intermediate material enriched in cobalt, nickel, and lithium, followed by extraction of the desired metals from the enriched intermediate material. In existing processes, some non-target metals can interfere with metal extraction steps. The inventor has discovered that pre-processing used LIBs reduces the amount of non-target metals prior to extraction steps. By employing the pre-processing steps disclosed herein in combination with one or more metal extraction steps, the recovered metal yields are significantly greater than traditional extraction methods.

[0006] The method disclosed herein employs relatively small amounts of energy, chemicals, and labor. The solvent and extractant requirements, in particular, are relatively low compared to traditional methods. This reduces the need for large inventories and associated losses, and minimizes waste generation to the point of near-zero discharge. The method disclosed herein can be used to recover up to 99.9% pure lithium, nickel, cobalt, and manganese in the form of various oxides or salts, e.g., sulfates and hydroxides. The method disclosed herein provides a modular, energy-efficient, and relatively inexpensive way to recover metals from used LIBs, and produces nearly zero waste.

[0007] The recycled components recaptured through methods described herein may be used to meet the demands of individual constituent elements used in LIB manufacturing even when the LIB battery chemistry is different from the LIB battery chemistry of the LIB being recycled.

[0008] Some aspects of the present disclosure are directed to a method for recovering metals. In some aspects, the method comprises a dissolution step comprising contacting black mass with a first acidic solution to provide a first mixture and filtering the first mixture to collect a first filtrate and a first filter cake, a precipitation step comprising contacting the first filtrate with a first basic solution to provide a second mixture comprising at least precipitated metals aluminum and iron and filtering the second mixture to collect a second filtrate comprising unprecipitated metals and a second filter cake comprising at least precipitated metals aluminum and iron, an extraction step comprising contacting the second filtrate with a first organic phase comprising a first water- immiscible organic solvent and a first extractant to extract at least copper metal into the first organic phase, and a stripping step comprising contacting the first organic phase comprising at least copper metal with a first acidic strip solution to extract at least copper metal into the first acidic strip solution and provide a copper-enriched strip solution. Upon extraction of the secondfiltrate with the first organic phase comprising the first extractant, at least copper metal is extracted into the organic phase, leaving behind a copper-depleted solution. In some embodiments, the extraction step is performed to extract copper. In some instances, the amount of copper removed from the second filtrate is any one of, less than, greater than, or between 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 wt. %. In some aspects, the method further comprises adding a hydrogen peroxide solution to the first mixture. The hydrogen peroxide solution can have a hydrogen peroxide concentration ranging from 1% to 32% (vol. / vol.), preferably from 2% to 10% (vol. / vol.) of a 32% wt. / wt. standard hydrogen peroxide solution (34.01 g / mol). In some embodiments, the first extractant is a copper-selective extractant. In some embodiments, the copper-selective extractant is an extractant of the Acorga® line of extractants, including a modified aldoxime extractant, or a modified alsoxime:ketoxime extractant. In some instances, the first acidic strip solution comprises sulfuric acid. In some instances, the copper in the copper-enriched strip solution is primarily in the form of copper sulfate. In some aspects, the first basic solution can have a pH ranging from 11 to 15. In some instances, the first basic solution is added to the first filtrate until the first filtrate reaches a pH of about 2 to 7, preferably from about 3 to 5.

[0009] In some aspects, the method further comprises, after the stripping step, a second extraction step comprising contacting the copper-depleted solution with a second organic phase comprising a second water-immiscible organic solvent and a second extractant to extract metals into the second organic phase. In some embodiments, the second extractant is an organophosphorus extractant. In some aspects, the organophosphorus extractant is di-(2- ethylhexyl) phosphoric acid (D2EHPA). In some embodiments, the second extractant extracts at least manganese, iron, and aluminum into the second organic solvent, leaving behind a solution that is depleted in manganese, iron, and aluminum, and enriched in cobalt, lithium, and nickel. In some instances, the organic phase comprising the at least manganese, iron, and aluminum metals is contacted with a second acidic strip solution in order to extract the least manganese, iron, and aluminum metals into the second acidic strip solution. The at least manganese, iron, and aluminum metals can then be crystallized from the second acidic strip solution. In some instances, the second acidic strip solution comprises sulfuric acid. In some instances, the least manganese, iron, and aluminum metals are crystallized as sulfate salts.

[0010] In some aspects, the method further comprises a third extraction step comprising contacting the solution that is enriched in cobalt, lithium, and nickel with a third organic phase comprising a third water-immiscible organic solvent and a third extractant to extract at least cobalt metal into the third organic phase. In some embodiments, the third extractant is a phosphinic acidbased extractant. In some aspects, the phosphinic acid-based extractant is Cyanex 272, a dialkyl phosphinic acid extractant. In some aspects, the third extractant extracts at least cobalt metal into the third organic solvent. By extracting cobalt metal from the solution that was enriched in cobalt, lithium, and nickel, the solution becomes a cobalt-depleted solution that is enriched in lithium and nickel, i.e., a lithium- and nickel-enriched solution .

[0011] In some embodiments, the method further comprises a third stripping step comprising contacting the third organic phase comprising the at least cobalt metal with a third acidic strip solution to extract the at least cobalt metal into the third acidic strip solution. In some embodiments, after the third stripping step, the at least cobalt metal is crystallized from the third acidic strip solution. In some aspects, the third acidic strip solution comprises sulfuric acid. In some instances, the cobalt metal is crystallized as a sulfate salt. In some embodiments, the pH of the lithium- and nickel-enriched solution is increased in order to precipitate a nickel salt and provide a nickel -depl eted and lithium-enriched solution. By precipitating nickel from the lithium- and nickel-enriched solution, the solution becomes enriched in lithium and depleted in nickel. The pH of the lithium- and nickel-enriched solution can be increased to a pH value of between 8 and 14, preferably to a pH value of between 8.5 and 11. In some aspects, the precipitated nickel salt is collected from the nickel-depleted, lithium-enriched solution. The precipitated nickel salt can be collected from the nickel-depleted, lithium-enriched solution using methods commonly known to those of skill in the art, including filtration and decanting. In some embodiments, a lithium salt is precipitated from the nickel-depleted, lithium-enriched solution and the precipitated lithium salt is collected. In some aspects, the lithium salt is precipitated by increasing the pH of the nickel- depleted, lithium-enriched solution to a pH value of between 8 and 14, preferably to a pH value of between 8.5 and 10.5, and adding sodium phosphate or potassium phosphate to the nickel-depleted solution to precipitate lithium phosphate salt.

[0012] In some instances, the metals disclosed herein are in the form of metal salts. In some aspects, a metal counter-ion in solution can be switched to a different counter-ion. For example, the phosphate counter-ion of the lithium phosphate salt can be switched to a differentcounter-ion. In an exemplary process, the lithium phosphate salt is dissolved in an acidic solution and calcium hydroxide, magnesium hydroxide, barium hydroxide, lithium hydroxide or a combination thereof is added until a pH ranging between 8 and 14 preferably to a pH value of between 8.5 and 10.5, is reached to provide a solution comprising lithium hydroxide and precipitated calcium phosphate. In an alternative process, the lithium phosphate salt is dissolved in an acidic solution and calcium carbonate is added until a pH ranging between 8 and 14 preferably to a pH value of between 8.5 and 10.5, is reached to provide a solution comprising lithium carbonate and precipitated calcium phosphate. In some instances, the solution comprising lithium hydroxide and precipitated calcium phosphate or the solution comprising lithium carbonate and precipitated calcium phosphate is filtered to remove precipitated calcium phosphate, leaving a filtrate comprising lithium hydroxide, the lithium hydroxide filtrate can then be processed through a D2EHPA MSX membrane in order to remove any remaining calcium or other impurities.

[0013] Each extraction step and corresponding stripping step disclosed above can be performed using a membrane-based extraction process, or a membrane-free extraction process. One example of a membrane-free extraction process involves the use of a separatory funnel. Exemplary membrane varieties that can be used to perform a membrane-based extraction include hollow fiber membranes, tubular membranes, spiral-wound membranes, and plate and frame membranes.

[0014] In some aspects, a water-immiscible organic solvent employed in any step of the method disclosed herein, e.g. the first water-immiscible organic solvent, the second water- immiscible organic solvent, or the third water-immiscible organic solvent is selected from the group consisting of dichloromethane, carbon tetrachloride, chloroform, benzene, toluene, xylene, methylethylketone, ethyl acetate, methyl isobutyl ketone, diethyl ether, di-isopropyl ether, methyl / -butyl ether, tetrahydrofuran, pentane, hexane, heptane, kerosene, silicone oil, Isopar L, cyclohexane, their equivalents, and a combination of one or more thereof. In some aspects, a basic solution employed in any step of the method disclosed herein, e.g., the first basic solution, the second basic solution, or the third basic solution can be a solution of sodium hydroxide, a solution of potassium hydroxide, a solution of ammonium hydroxide, a solution of barium hydroxide, a solution of lithium hydroxide, or a combination thereof. In some aspects, a basic solution employed in any step of the method disclosed herein can comprise a pH ranging from 11 to 15. A basic solution employed in any step of the method disclosed herein can comprise a pH that is any oneof, less than, greater than, or between 1 1 .0, 1 1 .1, 1 1 .2, 1 1 .3, 1 1 .4, 1 1 .5, 11 .6, 11 .7, 11 .8, 11 .9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9, and 15.0. In some embodiments, an acidic strip solution employed in any step of the method disclosed herein, e.g., the first acidic strip solution, the second acidic strip solution, or the third acidic strip solution comprises hydrochloric acid, nitric acid, sulfuric acid, or a combination of one or more thereof. In some aspects, an acidic strip solution employed in any step of the method disclosed herein can comprise a pH ranging from 0 to 1.5. An acidic solution employed in any step of the method disclosed herein, for example, the first acidic solution, the first acidic strip solution, the second acidic strip solution, or the third acidic strip solution, can comprise a pH that is any one of, less than, greater than, or between 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, and 1.5.

[0015] Some aspects of the present disclosure are directed to a method for recovering metals, comprising forming a first mixture by contacting black mass with a first acidic solution and filtering the first mixture to collect a first filtrate and a first filter cake, contacting the first filtrate with a first organic phase comprising a first water-immiscible organic solvent and a copperselective extractant to extract at least copper metal into the first organic phase and provide a copper-depleted filtrate. Contacting the copper-depleted filtrate with a first acidic strip solution to extract metals into the first acidic strip solution to form a solution enriched with lithium, nickel, and cobalt. Contacting the solution enriched with lithium, nickel, and cobalt with a second organic phase comprising a second water-immiscible organic solvent and a cobalt-selective extractant to extract at least cobalt metal into the second organic phase and provide a cobalt-depleted solution that is enriched in lithium and nickel. In some instances, the method further comprises collecting cobalt from the second organic phase by contacting the second organic phase with an acidic strip solution to extract cobalt from the second organic phase into the acidic strip solution. In some aspects, the method further comprises increasing the pH of the cobalt-depleted solution that is enriched in lithium and nickel to precipitate nickel and collecting the nickel. In some embodiments, the method further comprises increasing a strip solution pH to a pH value of between 8 and 14 and adding sodium phosphate or potassium phosphate to the strip solution to precipitate lithium phosphate salt and collecting the lithium phosphate salt.

[0016] Some aspects of the present disclosure are directed to a method for recovering metals, comprising forming a first mixture by contacting black mass with a first acidic solution and filtering the first mixture to collect a first filtrate and a first filter cake; contacting the first filtrate with a first basic solution to form a second mixture comprising at least precipitated aluminum and iron metals and filtering the second mixture to collect a second filtrate comprising unprecipitated metals and a second filter cake comprising at least the precipitated aluminum and iron metals; contacting the second filtrate with a first organic phase comprising a first water- immiscible organic solvent and a first extractant to extract at least copper metal into the first organic phase and provide a copper-depl eted second filtrate; contacting the first organic phase comprising at least copper metal with a first acidic strip solution to extract at least copper metal into the first acidic strip solution and form a copper-enriched strip solution and a copper-depleted second filtrate; a second extraction step comprising contacting the copper-depleted second filtrate with a second organic phase comprising a second water-immiscible organic solvent and a second extractant to extract at least manganese, iron, and aluminum metals into the second organic phase and provide a solution that is depleted in manganese, iron, and aluminum and enriched in cobalt, lithium, and nickel; a second stripping step comprising contacting the second organic phase comprising the manganese, iron, and aluminum metals with a second acidic strip solution to extract the manganese, iron, and aluminum metals into the second acidic strip solution and form a solution enriched in cobalt, lithium, and nickel; a third extraction step comprising contacting the solution enriched in cobalt, lithium, and nickel with a third organic phase comprising a third water- immiscible organic solvent and a third extractant to extract at least cobalt metal into the third organic phase and form a solution enriched in lithium and nickel; a third stripping step comprising contacting the third organic phase comprising the cobalt metal with a third acidic strip solution to extract cobalt metal into the third acidic strip solution; removing the third acidic strip solution to provide a recovered metal product comprising cobalt; increasing the pH of the solution enriched in lithium and nickel to precipitate a nickel salt and provide a nickel-depleted solution ; collecting the precipitated nickel salt from the nickel-depleted solution; and increasing a nickel-depleted solution pH to a pH value of between 8 and 14 and adding sodium phosphate or potassium phosphate to the nickel-depleted solution to precipitate lithium phosphate salt.

[0017] Non-limiting examples of organic solvents used for the various extraction steps disclosed herein include, but are not limited to chlorinated hydrocarbon solvents such asdichloromethane, carbon tetrachloride, and chloroform, aromatic solvents such as benzene, toluene, and xylene, ketones such as methylethylketone, ethyl acetate, and methyl isobutyl ketone, ether solvents such as diethyl ether, di-isopropyl ether, and methyl / -butyl ether, naphthenic solvents such as cyclohexane, methylcyclopentane, and l-ethyl-2-methylcyclopentane, isoparaffinic solvents such as any solvent from the Isopar™ line of synthetic isoparaffinic solvents, heterocyclic solvents such as tetrahydrofuran, paraffinic solvents such as pentane, hexane, and heptane, kerosene, silicone oil, their equivalents, and mixtures thereof. An organic solvent can be used to reduce the concentration of an extractant, and affect stability of the extractant in order to improve the extractants useful life and improve mass transport of the metal ion-extractant complex. The composition of the mixture of these two organic types range from 20 / 80 to 60 / 40 vol / vol of extractant to diluent.

[0018] As used herein, “black mass” refers to a type of e-waste comprising used and / or unwanted lithium-ion batteries. After removing structural and other non-functional components from end-of-life batteries, a black mass mixture is left. Black mass comprises battery-functional metals, including lithium, manganese, cobalt and nickel, typically in the form of oxides and / or salts, and can include additional battery materials, including anode separators, binders, additives and battery packaging.

[0019] An extractant is defined as a compound or group of compounds that are used to extract a substance such as a metal or metal ion from a material or solution. The extractants employed herein can be temperature-dependent or temperature-independent extractants. The extractants employed herein can be pH-dependent or pH-independent extractants. Non-limiting examples of extractants useful in the present disclosure include, for example aldoxime and ketoxime extractants such as the Acorga® series of extractants, phosphinic acid based extractants such as the Cyanex® series of extractants, P-diketones such as acetylacetone, trifluoroacetylacetone, dibenzoylmethane, thenoyltrifluoroacetone (TTA or HTTA), quinolines such as 8-hydroxyquinoline (oxine), oximes and dioximes such as N-nitrosophenylhydroxylamine ammonium (cupferron), N-benzoyl-N-pheynlhydroxylamine (NBPHA), and N- furoylphenylhydroxylamine, dithizones, di-(2-ethylhexyl)phosphoric acid (D2EHPA), and mixtures thereof.

[0020] The use of the word “a” or “an,” when used in conjunction with the term “comprising” in the claims and / or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0021] Throughout this application, the term “about” is used to indicate that a value includes the inherent variation of error for the device, the method being employed to determine the value, or the variation that exists among the study subjects.

[0022] The terms “comprise,” “have” and “include” are open-ended linking verbs. Any forms or tenses of one or more of these verbs, such as “comprises,” “comprising,” “has,” “having,” “includes” and “including,” are also open-ended. For example, any method that “comprises,” “has” or “includes” one or more steps is not limited to possessing only those one or more steps and also covers other unlisted steps.

[0023] The above definitions supersede any conflicting definition in any reference that is incorporated by reference herein. The fact that certain terms are defined, however, should not be considered as indicative that any term that is undefined is indefinite. Rather, all terms used are believed to describe the disclosure in terms such that one of ordinary skill can appreciate the scope and practice the present disclosure.

[0024] It is specifically contemplated that any limitation discussed with respect to one embodiment of the disclosure may apply to any other embodiment of the disclosure. Furthermore, any composition of the disclosure may be used in any method of the disclosure, and any method of the disclosure may be used to produce or to utilize any composition of the disclosure.

[0025] Other objects, features and advantages of the present disclosure will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 illustrates pH-Dependent extraction of different metals by D2EHPA extractant from sulfate solutions.

[0027] FIGS. 2A-2B illustrate separation of non-critical materials from LIB black mass using D2EHPA in MSX system. FIG. 2A is a graph depicting feed solution concentration. FIG. 2B is a graph depicting strip solution concentration. Typically, the strip solution contained < 10 ppm of Li, Co, Ni.

[0028] FIGS. 3A-3E illustrate separation of non-critical materials from LIB black mass using D2EHPA in MSX system. FIG. 3A is a graph depicting feed solution concentration. FIG. 3B is a graph depicting strip solution concentration. FIG. 3C is a graph depicting cumulative impurity removal yield. FIG. 3D is a graph depicting impurity extraction rate. FIG. 3E is a graph depicting cumulative purity of cathode critical materials including Co, Ni, an Li.

[0029] FIG. 4 is a flow diagram depicting process steps according to some embodiments of the present disclosure.

[0030] FIG. 5 is a flow diagram depicting process steps according to some embodiments of the present disclosure.

[0031] FIG. 6 is a flow diagram depicting process steps according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0032] Lithium-ion batteries (LIBs), while first commercially developed for portable electronics, are now ubiquitous in daily life. LIBs are used in increasingly diverse applications, including electric cars, power tools, medical devices, smart watches, drones, satellites, and utilityscale storage.

[0033] In addition to lithium, LIBs employ other metals in their construction, including cobalt, nickel, and manganese. Despite the widespread use of LIBs, there is little to no mining in the U.S. for these metals, and only around 5% of LIBs used in the U.S. are recycled. End-of-life LIBs can be used as a secondary resource to recover and recycle battery materials, however, conventional LIB recycling technologies are complex, inefficient, and generate a lot of waste.

[0034] Embodiments of this disclosure describe a facile and efficient method for recycling LIB constituent metals, including lithium, cobalt, nickel, and manganese. The method is premised on the use of a pre-treatment step that removes unwanted black mass material in combination with one or more extractants to selectively remove or extract specific metals. The method is an energy-efficient, cost-effective and environmentally friendly process that can recover constituent elements with >99 wt.% purity from a wide range of spent LIB feedstocks.A. Extraction equipment

[0035] The methods disclosed herein can employ different types of membranes for metal extraction. The methods disclosed herein can also employ other extraction equipment, including flow-injection extraction, solid-supported liquid-liquid extraction, and separatory funnels. Nonlimiting examples of membrane configurations used for membrane extraction include hollow fiber membranes, tubular membranes, spiral-wound membranes, and plate and frame membranes. Nonlimiting examples of materials employed in extraction membranes include porous polytetrafluoroethylene, porous plastic membranes, sintered porous metal membranes, glass filter, ceramics filter, paper filter, various kinds of fibrous filters, and porous membranes obtained by expanding a thermoplastic crystalline polymer.

[0036] Hollow fiber membranes utilize a plurality of porous tubes or hollow fibers packed inside an outer shell. Each filament is typically flexible and narrow in diameter. The narrow tube diameter allows for flexibility and high total filtering surface area. Permeate flux in hollow fiber filter systems are much higher than that of tubular systems.

[0037] Tubular membranes are tube-like structures with porous walls. Tubular modules work through tangential cross-flow, and are generally used to process difficult feed streams such as those with high dissolved solids and / or high suspended solids. Tubular modules consist of a minimum of two tubes; the inner tube, called the membrane tube, and the outer tube, which is the shell. The feed stream goes across the length of the outer tube and is filtered in into the inner tube while concentrate collects at the opposite end of the outer tube.

[0038] Spiral-wound filtration membranes consist of membranes, feed spacers, permeate spacers, and a permeate tube. First, a membrane is laid out and folded in half with the membrane facing inward. Feed spacer is then put in between the folded membranes, forming a membrane sandwich. The feed spacer provides a space for water to flow between the membrane surfaces, and allows for uniform flow between the membrane leaves. A permeate spacer is attached to the permeate tube, and the membrane sandwich is attached to the permeate spacer. A subsequent permeate layer is laid down and sealed, and the process is repeated until all of the required permeate spacers have been attached to the membranes. The finished membrane layers then arewrapped around the tube creating a spiral shape. Feed travels through the flow channels tangentially across the length of the element. Filtrate will then pass across the membrane surface into the permeate spacer, where it is carried down the permeate spacer towards the permeate tube. The feed then becomes concentrated at the end of the element body. Spiral -wound elements come in multiple configurations with different spacers, membrane types, lengths, and diameters that allow it to fit multiple applications.

[0039] Plate and frame membrane systems utilize membranes laid on top of a plate-like structure, which in turn is held together by a frame-like support. For cross flow plate and frame membrane systems, fouling of the membrane is significantly less because the flow is tangential and does not require use of the cake filtration system. It works on the basic principles of cross flow where feed enters on one side of the plated membrane and retentate collects on the other end of the plate. Permeate travels through the membrane and collects on the inside of the supporting plate. Easy separation of solids from extracts and easy removal / cleaning of filter surfaces are the main advantages of plate and frame membrane systems.B. Examples

[0040] Typically, at the end of their life, different types of LIBs are shredded together which results in a black mass of varied composition with both desirable elements such as cobalt, manganese, nickel, and lithium, and undesirable elements such as iron (Fe), aluminum (Al), copper (Cu), and zinc (Zn). The non-metals such as carbon binders and graphite are removed from the black mass by leaching the metals in acid solution. Table 1 shows the metal composition of various industrial scrap LIB feedstocks, i.e., black mass, including three scrap samples that were collected from different leading LIB industrial recyclers and a recovered electric car battery. The scrap sample 1 was pretreated by the recycler to remove some of the undesired materials such as copper and organics. Scrap sample 2 was obtained with no pretreatment and shows the presence of various undesirable elements such as iron, aluminum, copper, and zinc. Scrap sample 3 was a black mass sample obtained from a recycler (Recycling Coordinators, Inc., Akron, OH).Table 1 Composition of various feedstocks obtained from LIB recyclers.

[0041] A more efficient pretreatment method was investigated to separate undesirable non-critical materials present in the mixed scrap LIB black mass including Fe, Cu, and Zn in addition to Al. Feasibility studies were carried out using distribution coefficient measurements to investigate the separation of non-critical metals from Li-ion battery metals present in the mixed scrap LIB feedstock using Di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant in the organic phase. D2EHPA can selectively extract iron, zinc, manganese, and copper below the feed pH of 3 whereas cobalt and nickel are extracted above the pH of 3 as shown by the dotted line in FIG. 1. Other extractants will have different extraction profiles, and therefore have different cation extraction vs. pH curve profiles. Therefore, it has the potential to effectively remove impurities such as Fe, Zn, Al, and Cu from LIB black mass. Although D2EHPA extracts Mn along with other impurities, it can be separated from other impurities and recovered as a product.

[0042] It was observed that undesirable metals including Cu, Fe, Zn, and Al can be selectively removed from the mixed scrap LIB black mass using a 1-2M H2SO4 strip solution within an operating pH range of 2-3. Additionally, D2EHPA was used to separate the non-critical materials from the battery materials including Fe, Cu, Zn, Al and Mn as a part of the pretreatment procedure. 98 wt.% of the battery materials were recovered with the developed pretreatment process using D2EHPA. This pretreatment process can serve as an alternative to the combined steps of Al extraction using concentrated NaOH and Cu extraction using an extractant.Example 1 Distribution coefficient studies: Removal of undesirable materials from mixed scrap LIB feedstock using D2EHPA

[0043] Cu, Al, Fe, Zn, and Mn can be separated from other desirable constituent elements including Co, Ni, and Li using solvent extraction with D2EHPA as the extractant in the organic phase incorporated in the pores of a hollow fiber support membrane. D2EHPA selectively extracts undesirable metals over critical battery materials within a pH range of 2-3. Distribution studies were carried out to determine the separation efficiency of D2EHPA, in addition to optimizing thepH range and strip solution concentration. For this purpose, a feed solution of a sample was prepared by dissolving 70 g of LIB black mass in 1 liter of H2SO4 solution. The undissolved carbon materials were filtered out. The composition of the resulted feed solution was Li = 2402 ppm; Co = 6332 ppm; Ni = 9647 ppm; Mn = 3230 ppm; Cu = 6449 ppm; Fe = 407 ppm; Al = 5599 ppm The extraction was conducted using four different concentrations of D2EHPA (30 vol.%, 40 vol.%, 50 vol.% and 60 vol.%) in Isopar-L. Four different feed pH values, 1, 2, 3, and 4, adjusted using ammonium hydroxide, were used for the extraction studies. Three different strip solution concentrations, 0.5M, IM, and 2M were used for extraction. For the extraction of undesirable metals from the sample, both organic phase and aqueous phase (2 mL each) were mixed together for 10 minutes followed by centrifugation of the mixture for another 10 minutes. The compositions of the feed before and after mixing with the organic phase, and the stripping solution after back extraction were measured using ICP-OES as shown in Tables 2 and 3 (0.5M), Tables 4 and 5 (IM), and Tables 6 and 7 (2M). Based on the distribution coefficient results, the optimal process parameters included a pH range of 2-3, strip solution concentration of 2M H2SO4, and an organic phase composition of 30% v / v D2EHPA in Isopar-L. This combination of parameters yielded results that were approximately 30% better than that of other parameter combinations.Table 2 Extraction of Al, Fe, Cu, Mn from LIB black mass in Sulfuric Acid with D2EHPA and 0.5M StripTable 3 Back Extraction Distribution Coefficient - 0.5M Sulfuric Acid StripTable 4 Extraction of Al, Fe, Cu, Mn from LIB black mass in Sulfuric Acid with D2EHPA and IM StripTable 5 Back Extraction Distribution Coefficient - IM Sulfuric Acid StripTable 6 Extraction of Al, Fe, Cu, Mn from LIB black mass in Sulfuric Acid with D2EHPA and 2M StripTable 7 Back Extraction Distribution Coefficient - 2M Sulfuric Acid StripExample 2 Removal of undesirable metals from mixed scrap LIB feedstock

[0044] The process disclosed herein demonstrated removal of undesirable metals from the mixed scrap LIB feedstock as a part of the pretreatment process using D2EHPA as the extractant in the organic phase. A feed solution was prepared by dissolving 60 g of scrap LIB material in 750 mL of 0.5M H2SO4. Undissolved carbon black was separated from the feed solution using vacuum filtration. 2 vol.% H2O2 was used as a reducing agent to convert partially reduced Co3+to the soluble Co2+valence state. The carbon additives present in the cathode material are insoluble in H2SO4 and were removed from the feed solution using vacuum filtration. A 250 mL solution of 3M sodium acetate buffer solution was used to stabilize the pH of the feed solution. A feed solution concentration of approximately 45 g / L spent cathode material was obtained. The extractant used was 30% v / v D2EHPA in Isopar L. The strip solution was 500 mL of 2M H2SO4. The initial pH of the feed solution was adjusted to 2.9 using ammonium hydroxide. In order to prevent the decrease in extraction rate overtime resulting from a decrease in pH as LIB materials are extracted, ammonium hydroxide was added to the feed solution intermittently to maintain a pH range of 2-3 over the duration of the run. D2EHPA selectively extracts undesirable metals including Cu, Al, Fe, and Zn along with Mn within a pH range of 2-3 while preventing the co-extraction of Co, Ni, and Li. 98% of Co, Ni, and Li in the original feed side was obtained. The change in the concentrations of all the metals in the feed and strip solutions is presented in FIGS. 2A-2B and FIGS. 3A-3E. The purity of the battery materials remaining in the feed solution is >99.5 wt.%.Example 3 General Procedure

[0045] Referring to Figure 4, a method for recovering metals can include the following steps. At step 410, a first mixture is formed by contacting black mass with a first acidic solution. The resulting mixture includes undissolved solids comprising metals to be collected at subsequent steps. At step 420, the first mixture is filtered to collect a first filtrate comprising the metals in salt form. At step 430, a second mixture is formed. The second mixture is formed by contacting thefirst filtrate with a first basic solution. The second mixture comprises precipitated metal salts. At step 440, the second mixture is filtered to collect a second filtrate comprising precipitated metal salts. At step 450, the second filtrate is contacted with a first organic phase comprising a first water-immiscible organic solvent and a first extractant to extract metals into the first organic phase. The first organic phase comprises the first organic solvent and metals that are coordinated or chelated to the first extractant.

[0046] Referring to Figure 5, the first organic phase from step 450 is contacted with a first acidic strip solution at step 510. Contacting the first organic phase with the first acidic strip solution extracts metals from the organic phase into the acidic strip solution and forms a metal-enriched strip solution. At step 520, the second filtrate solution from step 450 is contacted with a second organic phase comprising a second water-immiscible organic solvent and a second extractant to extract metals into the second organic phase. At step 530, the second organic phase is contacted with a second acidic strip solution. Contacting the second organic phase with the second acidic strip solution extracts metals from the second organic phase into the second acidic strip solution. At step 540, the second filtrate solution from step 520 is contacted with a third organic phase comprising a third water-immiscible organic solvent and a third extractant to extract metals into the third organic phase. At step 550, the third organic phase comprising the metals is contacted with a third acidic strip solution to extract metals into the third acidic strip solution.

[0047] Referring to Figure 6, the third acidic strip solution is removed from at step 610 to provide a recovered metal product comprising cobalt. At step 620, the pH of the second filtrate from step 540 is increased to precipitate nickel and provide a nickel-depleted solution. At step 630, the precipitated nickel salt is collected from the nickel-depleted solution. At step 640, the pH of the nickel-depleted solution is increased to a pH value of between 8 and 14, and sodium phosphate or potassium phosphate is added to the solution to precipitate a lithium phosphate salt. At step 650, the lithium phosphate salt is collected.Example 4 Metal Recovery Procedure

[0048] Black mass dissolution - A 1 liter solution of 2M nitric acid was prepared by adding 500 mL of deionized (DI) water into a 1 liter volumetric flask and adding 129 mb of 70% nitric acid. The flask was then filled to the 1 liter mark with DI water. The 2M nitric acid solution was transferred to a 4 liter beaker on a stirrer / hot plate and a stir bar was added to the beaker. 133 mLof hydrogen peroxide was added while stirring. 133 g of LIB black mass was then added and the liquid level on the beaker was marked.

[0049] A thermocouple attached to the hot plate was inserted into the beaker liquid. The hot plate temperature was set to 50 °C and stir rate was set to 400-450 rpm. As stirring began, the contents began to foam. The foam can be knocked down with a small amount of DI water squirted against the beaker inside wall or with a spatula. Once the beaker liquid temperature reached 50 °C, the temperature was increased to 65 °C. Once the beaker liquid temperature reached 65 °C and foaming subsided, the temperature was raised to 85 °C. DI water was added every 30 minutes in order to maintain the liquid level at the marked beaker location. The added DI water was used to wash away solids that collected on the beaker inside wall. After 5 hours of stirring at 85 °C and replenishing water, the hot plate was turned off while stirring was maintained. The beaker liquid (feed solution) was stirred until the liquid reached room temperature.

[0050] For solids filtration, a Buchner funnel was used to separate precipitated solids from the collected liquids (feed solution). The solids were dried and the mass of the dried solids was then measured.

[0051] Feed preparation with buffer - A 1 liter solution of acetate buffer was prepared by adding 250 mL of ammonium acetate to a 1 liter beaker on a hot plate. The solution was stirred at 400 rpm and a pH probe was placed into the solution. Acetic acid was added until a pH of 5.6 was reached. 150 mL of the acetate buffer solution was slowly added to the feed solution obtained during the dissolution step described above. A pH probe was then inserted into the combined feed solution and acetate buffer solution. The pH of the clear should combined feed solution and acetate buffer solution was 0.02-0.03.

[0052] Buffer solution was then added slowly until a pH of 0.5-0.6 was reached. After 5 minutes, buffer solution was added until a pH of 0.9-0.95 was reached. The clear solution began to turn cloudy, indicating the onset of precipitation. More buffer solution was added until the feed solution reached a pH of 1.5. A hose was affixed to the side arm of a 2 liter filtrate flask and the opposite end of the hose was connected to a vacuum pump. A Buchner funnel was placed on top of the filtrate flask and a 0.7 micron filter was placed inside the funnel. The vacuum pump was turned on and the feed solution was added to the Buchner funnel. The feed solution liquid waspulled through the filter into the flask and the precipitants were captured on the 0.7 micron filter. The vacuum was maintained until no more liquid dripped from the filter.

[0053] Strip preparation - 1 liter of a strip solution of IM sulfuric acid was prepared by adding 900 mb of DI water to a 1 liter volumetric flask. 54.3 mL of 98% sulfuric acid was then added to the flask, and additional DI water was added until the volume reached 1 liter. The strip solution was added to a 1 liter beaker and connected to an extraction unit.

[0054] Extraction operation - The extraction unit includes three consecutively-plumbed extraction modules. A feed solution passes through a first extraction module, a solution of a first extractant in a first organic solvent extracts copper from the feed solution, and the feed solution containing the remaining metals is fed to a second extraction module. A solution of a second extractant in a second organic solvent extracts manganese, iron, and aluminum from the feed solution, and the feed solution containing the remaining metals (Co, Li, Ni, Na, and trace amounts of Ca and K) is fed to a third extraction module. A solution of a third extractant in a third organic solvent extracts cobalt from the feed solution, and the cobalt / extractant solution are collected in order to isolate the cobalt. By externally adjusting and maintaining a certain cobalt concentration in the third feed solution, the nickel contamination in the strip is strongly suppressed. This ensures that during the evaporation and crystallization stage, nickel contamination levels are kept within battery -grade specifications. A feed solution containing the remaining metals (Ni, Li, Na, and trace amounts of Ca and K) is transferred to subsequent process steps.

[0055] A feed beaker was placed on a hot plate and an extraction unit discharge line and input tube were placed into the feed beaker. A temperature probe and a pH probe were placed into the feed beaker. The temperature was set to 25 °C and stir rate set to 300 rpm. A feed beaker pH control unit was set at 1.9. A dosing solution containing 200 mL of 15% ammonium hydroxide was prepared. An extraction unit pH control unit was set up to add ammonium hydroxide as required every 5-10 minutes to maintain pH within 0.1 pH units of the target pH. The extraction unit was turned on and operated at pH 1.9 for 30 minutes. The pH control unit was then set to 2.0 and the extraction unit was run for an additional 60 minutes. The pH control unit was then set to pH 2.5 and the extraction unit was run from 5 to 7 hours.

[0056] Copper (sulfate) crystallization - The first organic solvent from extraction with the first extraction module includes a copper-extractant chelate. This organic solvent is then treatedwith sulfuric acid. The copper is extracted into the aqueous sulfuric acid in the form of copper sulfate. The solution includes copper sulfate at a purity of approximately 99%. This high purity of extraction is the result of very tight pH controls, elimination of local pH effects, and precise contact time with the extractants, which enables the extractant within the pores to be highly selective for certain metal ions. The crystallization of CuSC is established by controlled evaporation of the water remaining water in solution at about 70-90 °C until supersaturation is reached. The evaporation flux and cooling rates can be adjusted so that a high yield of CuSO4 is removed from the solution.

[0057] The second organic solvent from extraction with the second extraction module includes Mn, Fe, Al, Ca, Cd, Zn and trace amounts of other metals. This organic solvent is then treated with sulfuric acid. The metals are extracted into the aqueous sulfuric acid in the form of sulfate salts. The mixed sulfate salt solution can be evaporated to crystallize these metal salts into solids in order to minimize water disposal volumes. The water from the mixed sulfate salt solution can be evaporated at a temperature of around 70-90 °C. The majority of water is removed and then rapidly cooled so that the vast majority of salts are crystallized and separated from the supernatant using a filter. The supernatant can then be reused for a subsequent black mass dissolution.

[0058] Cobalt (sulfate) crystallization - The third organic solvent from extraction with the third extraction module includes a cobalt-extractant chelate. This organic solvent is then treated with sulfuric acid. The cobalt is extracted into the aqueous sulfuric acid in the form of cobalt sulfate. The solution includes cobalt sulfate at a purity ranging from 92%-97%. Highly pure CoSO4 crystals are created using controlled evaporation of the remaining water in the solution until supersaturation is reached. The evaporation flux and cooling rates can be adjusted so that a high yield of CoSO4 is obtained from the solution. The CoSO4 obtained using this method is approximately 99% pure. Multiple stages of crystallization along with anti-solvent (a solvent in which the product is insoluble) additions can be used to increase the yield and / or purity. Any remaining co-containing solution can simply be reused in the third extraction described above in order to improve final cobalt yields.

[0059] Nickel leaching - The feed solution from the third extraction module described above contains the remaining metals (Ni, Li, Na, and trace amounts of Ca and K), and can be treated to precipitate NiOH with a very high degree of purity. The feed solution pH was raised to9 or higher by adding NaOH (s) until all the Ni precipitated out as NiOH. The resulting solution was washed using reverse osmosis (RO) water in order to remove the water-soluble metals such as Na, Ca, and K. The conductivity of the effluence was monitored conductivity change was minimal, indicating negligible amounts of Na, Ca, and K metals remained in solution. Solid NiOH was obtained and was dried at ambient temperature and pressure.

[0060] Lithium (phosphate) leaching - The output from the nickel leaching step above had substantially all of the Ni removed, resulting in a feed solution that was highly lithium-rich, with nearly all contaminants removed. Sodium phosphate (s) was added to the solution at a pH of between 8.5 and 10.5 in order to precipitate out LiaPCh. The resulting solution was rich in LiaPCh but also contained water-soluble metals such as Na, Ca, and K. This solution was washed using the same method described above for nickel leaching. The result was a highly pure LL3PO4 solid, and the phosphate anion can be exchanged for hydroxide or carbonate, as described below.

[0061] Conversion of LiaPCU into LiOH and / or Li2COa - Solid LiaPCM was dissolved in weak sulfuric acid and CaOH (s) was added to the solution at a pH or between 8.5 and 10.5 until the entire amount of LiaPCU was converted to LiOH. The Ca precipitated out as Ca2SO4. The Ca can be removed using a membrane with an organic extractant, one such extractant being D2EHPA. Alternatively, a carbonate salt, such as CaCOa can be used to convert the Li3PO4into LiaCOa.

[0062] Sea water reverse osmosis (SWRO) processing - Water recovered from any of the steps described above can be processed in order to remove sodium using reverse osmosis membranes. In particular embodiments, water recovered from the nickel and / or lithium washing steps described above are processed in order to remove sodium using reverse osmosis membranes. The SWRO-processed waste water will be highly concentrated with brine. This solution can be evaporated until the Na2SC>4 and / or NaOH is precipitated from the solution and disposed of as solid waste or sold as a product.Example 5 Concentration Effects

[0063] The concentration at which extraction steps are performed has an effect on extraction rate and the degree to which the desired metal is extracted. The data in Table 8 below depicts results for extractions performed with solutions of different starting feed solution cobalt concentrations, 4,550 ppm and 10,600 ppm. First extraction (cobalt ppm), second extraction (nickel ppm), and third extraction (lithium ppm) were measured over three different times, 1.5hours, 3.5 hours, and 5.5 hours on the two solutions of different starting cobalt concentrations (4,550 ppm and 10,600 ppm). The 10,600 ppm cobalt solution was labeled “concentrated” and the 4,550 ppm cobalt solution was labeled “unconcentrated”. In comparing extraction results of the 10,600 ppm concentrated starting solution to the 4,550 ppm unconcentrated starting solution, the data below demonstrates that employing a higher-concentration starting feed solution improves the separation of cobalt and nickel and cobalt and lithium of the extractive steps. For example, the Ni / Co ratio of the concentrated starting solution was significantly higher for each extraction duration (1.5, 3.5, and 5.5 hours) than for the unconcentrated starting solution. Similarly, the Li / Co ratio of the concentrated starting solution was significantly higher for each extraction duration than for the unconcentrated starting solution. These data indicate that the initial solution concentration can have a dramatic effect on extractive effectiveness. The initial solution concentration can be increased in order to increase extractive effectiveness.Table 8Example 6 Temperature Effects

[0064] The temperature at which extraction steps are performed has an effect on extraction rate and the degree to which the desired metal is extracted. The data in Table 9 below depicts results for extractions performed at different temperatures, 25 °C and 38 °C. The extractions were performed between the third organic phase and third acidic strip solution. The starting Cobalt concentrations for the 25 °C and 38 °C extractions were 10,600 and 11,100 ppm, respectively. After 1 hour of extraction time, the higher temperature extraction extracted greater than 4* the amount of Cobalt. The 2, 3, and 4 hour extraction times show a trend of increasing extractive effectiveness, with the 4 hour higher temperature experiment extracting greater than 4 / the amount of Cobalt than the lower temperature experiment. These data indicate that extraction temperature can have a dramatic effect on extractive rate. The extractions disclosed herein can be performed at temperatures greater than room temperature in order to increase extractive effectiveness. The extractions disclosed herein can be performed for different durations in order to increase extractive effectiveness.Table 9

Claims

CLAIMS1. A method for recovering metals, the method comprising: forming a first mixture by contacting black mass with a first acidic solution and filtering the first mixture to collect a first filtrate and a first filter cake; contacting the first filtrate with a first basic solution to form a second mixture comprising at least precipitated metals aluminum and iron and filtering the second mixture to collect a second filtrate comprising unprecipitated metals and a second filter cake comprising at least precipitated metals aluminum and iron; contacting the second filtrate with a first organic phase comprising a first water-immiscible organic solvent and a first extractant to extract at least copper metal into the first organic phase and provide a copper-depleted second filtrate; and contacting the first organic phase comprising at least copper metal with a first acidic strip solution to extract at least copper metal into the first acidic strip solution and form a copper-enriched strip solution and a copper-depleted second filtrate.

2. The method of claim 1, further comprising adding a hydrogen peroxide solution to the first mixture.

3. The method of claim 2, wherein the hydrogen peroxide solution comprises a hydrogen peroxide concentration ranging from 1% to 32% (vol. / vol) of a 32% wt. / wt. standard hydrogen peroxide solution.

4. The method of claim 1, wherein the first extractant is a copper-selective extractant.

5. The method of claim 1, further comprising, after the stripping step, a second extraction step comprising contacting the copper-depleted second filtrate with a second organic phase comprisinga second water-immiscible organic solvent and a second extractant to extract at least manganese, iron, and aluminum metals into the second organic phase and provide a solution that is depleted in manganese, iron, and aluminum, and enriched in cobalt, lithium, and nickel.

6. The method of claim 5, wherein the second extractant is an organophosphorus extractant.

7. The method of claim 6, wherein the organophosphorus extractant is di-(2-ethylhexyl) phosphoric acid.

8. The method of claim 5, further comprising a second stripping step comprising contacting the second organic phase comprising the at least manganese, iron, and aluminum metals with a second acidic strip solution to extract the at least manganese, iron, and aluminum into the second acidic strip solution.

9. The method of claim 8, further comprising a third extraction step comprising contacting the solution enriched in cobalt, lithium, and nickel with a third organic phase comprising a third water-immiscible organic solvent and a third extractant to extract at least cobalt metal into the third organic phase and provide a solution that enriched in lithium and nickel.

10. The method of claim 9, wherein the third extractant is a phosphinic acid-based extractant.

11. The method of claim 9, further comprising a third stripping step comprising contacting the third organic phase comprising the at least cobalt metal with a third acidic strip solution to extract at least cobalt metal into the third acidic strip solution.

13. The method of claim 11, further comprising increasing the pH of the solution that is enriched in lithium and nickel to precipitate a nickel salt and provide a lithium-enriched solution that is nickel-depleted.

14. The method of claim 13, further comprising collecting the precipitated nickel salt from the lithium-enriched solution.

15. The method of claim 14, further comprising precipitating a lithium salt from the lithium- enriched solution and collecting the precipitated lithium salt.

16. The method of claim 15, wherein precipitating a lithium salt comprises adding sodium phosphate or potassium phosphate to the lithium-enriched solution to precipitate lithium phosphate salt.

17. The method of claim 16, further comprising dissolving the lithium phosphate salt in an acidic solution and adding calcium hydroxide, magnesium hydroxide, barium hydroxide, lithium hydroxide or a combination thereof until a pH ranging between 8 and 14 is reached to provide a solution comprising lithium hydroxide and precipitated calcium sulfate.

18. The method of claim 1, wherein the extraction step and corresponding stripping step are performed in one of a hollow fiber membrane, a tubular membrane, a spiral-wound membrane, plate and frame membrane, and a separatory funnel.

19. A method for recovering metals, the method comprising: forming a first mixture by contacting black mass with a first acidic solution and filtering the first mixture to collect a first filtrate and a first filter cake; contacting the first filtrate with a first organic phase comprising a first water-immiscible organic solvent and a cobalt-selective extractant to extract at least cobalt metal into the organic phase and form a solution enriched in lithium, nickel, and cobalt; contacting the solution enriched with lithium, nickel, and cobalt with a second organic phase comprising a second water-immiscible organic solvent and a cobalt-selective extractant to extract at least cobalt metal into the second organic phase and forming a cobalt-depleted solution that is enriched in lithium and nickel.

20. The method of claim 19, further comprising collecting cobalt from the second organic phase by contacting the second organic phase with an acidic strip solution to extract cobalt from the second organic phase into the acidic strip solution.

21. The method of claim 19, further comprising increasing the pH of the cobalt-depleted solution to precipitate nickel and collecting the nickel.

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