Process for producing cobalt and / or nickel

Abstract

The present invention concerns a process for producing nickel and / or cobalt comprising the steps of: a) providing an aqueous metal sulfate feed solution comprising nickel and / or cobalt ions and impurities; b) separating a first part of impurities from the metal sulfate feed solution to obtain a raffinate; c) optionally subjecting the raffinate to an ion exchange treatment to remove a second part of impurities; and d) subjecting at least a portion of the optionally ion exchanged raffinate as electrolyte to electrowinning to produce nickel and / or cobalt.

Description

Process for producing cobalt and / or nickelField of the invention

[0001] The present invention is in the field of metal refining. More specifically, the present invention relates to a process for producing cobalt and / or nickel.Background of the invention

[0002] The market for cobalt, particularly in aerospace-grade cobalt cathodes and battery-grade cobalt sulfate crystals, is expected to see significant developments over the coming decade.

[0003] The aerospace industry is expected to grow due to increasing air travel demand and the development of new and more efficient aircraft engines. Cobalt metal is a vital component in the aerospace industry due to its exceptional properties. Cobalt is primarily used in the production of superalloys, which are essential for manufacturing critical components of jet engines, such as turbine blades, vanes, and combustion chambers. These superalloys, which can withstand extreme temperatures and stresses, ensure the reliability and efficiency of aircraft engines. Additionally, cobalt's magnetic properties are utilized in producing high-performance magnets for aerospace applications, further underscoring its importance in advancing aerospace technology and enhancing the performance and safety of modern aircraft.

[0004] Continued investments in defense, particularly in advanced aircraft and missile systems, will sustain demand for high-performance cobalt alloys.

[0005] The most significant driver for battery-grade cobalt sulfate is the growth of the electric vehicle market. Cobalt is a key component in lithium-ion batteries, which are widely used in EVs. Growing demand for renewable energy storage solutions also boosts the need for lithium-ion batteries, thereby increasing demand for cobalt sulfate.

[0006] Cobalt is usually extracted as a byproduct of copper mining from copper-cobalt ores. The ground ore is subjected to a leaching process where it is treated with sulfuric acid to dissolve cobalt and copper, forming a pregnant leach solution (PLS).

[0007] Solvent extraction is used to selectively remove copper from this PLS; after copper removal, the remaining solution contains cobalt, along with other impurities like magnesium, manganese, zinc, aluminium and iron. Magnesium oxide (MgO) is added to the cobalt-bearing solution to precipitate cobalt quantitively as an impure cobalt hydroxide intermediate. MgO is relatively inexpensive and readily available, making it a cost-effective reagent for large-scale operations generating an intermediate product with better filtration characteristics compared to the use of NaOH as a precipitant.

[0008] Unreacted or co-precipitated magnesium contaminates and significantly lowers the grade of the intermediate cobalt hydroxide and complicates production of high purity products like superalloy grade cobalt cathodes or battery grade cobalt sulfate crystals.

[0009] Most cobalt refining projects use techniques such as solvent extraction (SX) and ion exchange (IX), particularly when targeting battery grade cobalt sulfate or superalloy grade cobalt metal. Cobalt electrowinning traditionally requires <1 mg / L Zn, <1 mg / L Cu, and <150 mg / L Ni in the advance electrolyte and targets are even more strict, also for impurities like Mg and Ca, for battery grade products.

[0010] Organophosphorus-acid extractants are most widely used in refineries for purification of cobalt streams. Zinc, calcium, manganese and residual copper can be readily removed together with other trace impurities using D2EHPA with no or very limited loss of cobalt; Cyanex 272 can be used to separate cobalt from magnesium and nickel, thereby purifying the cobalt stream.

[0011] Sodium hydroxide can be used for pH control in these SX circuits; this reagent does not introduce any solids to the circuit but produces sodium-containing effluent streams that needs to be treated before being discarded. The majority of EV-battery materials refineries use sodium hydroxide as neutralizing agent; with an increase in the manufacture of EV-battery-material chemicals such as lithium hydroxide, nickel sulfate and cobalt sulfate it is forecasted that sodium sulfate from these refineries will saturate the market and it will become an environmental liability as this material cannot be permanently disposed of an industrial landfill due to its high solubility.

[0012] Achieving the magnesium specification in battery grade cobalt sulfate solution or crystals is problematic. Although Cyanex 272 demonstrates selectivity for cobalt over magnesium, the separation is not good enough to completely prevent magnesium extraction, even with the inclusion of a scrubbing step on the loaded organic phase.

[0013] The use of two different extractants on a single plant is potentially problematic as any crosscontamination might lead to loss of selectivity. Highly clarified solutions are also required as feed to solvent extraction units to avoid crud formation and the associated cost and complexity to remove this crud.

[0014] Also from a safety perspective, the use of solvent extraction in hydrometallurgical refineries is discouraged: the organic solvents used in solvent extraction processes are typically volatile and flammable. The presence of these solvents in large quantities increases the risk of fire and explosion, particularly in environments where there might be sources of ignition or high temperatures. Ensuring the safe use of solvent extraction involves implementing complex and costly safety systems, such as advanced ventilation, fire suppression systems, and continuous monitoring for solvent vapours. These systems need regular maintenance and stringent adherence to safety protocols, which increases operational complexity and costs.

[0015] Many organic solvents are toxic and pose significant health risks to workers through inhalation, ingestion, or skin contact. Organic solvents can be harmful to the environment if they are not properly managed. Spills or leaks can lead to soil and water contamination, which can have devastating effects on local ecosystems.

[0016] Metal impurities such as copper, iron, and zinc have high upgrading ratios in cobalt electrowinning and therefore have to be removed first.

[0017] Separation of manganese would be possible using solvent extraction with D2EHPA and cobalt could be separated from magnesium using solvent extraction with Cyanex 272 as described above and demonstrated in Figure 1 , generating (at least) stoichiometric amounts of Na2SO4, creating environmental liabilities.

[0018] The current invention provides a solution for at least one of the above-mentioned problems by providing a process for preparing high-purity nickel and / or cobalt metal as well as high-purity nickel and / or cobalt sulfate crystals, without using solvent extraction or limited solvent extraction.Summary of the invention

[0019] The inventors found that a cobalt and / or nickel refining process can be greatly simplified by performing an electrowinning step despite the presence of impurities in the electrolyte, because electrowinning is fairly forgiving with regard to the levels of elements such as magnesium, potassium and manganese in the electrolyte. Thereby the production of cobalt and / or nickel is improved as the need of extensive separation treatments is reduced. Thus, the invention concerns a process for producing nickel and / or cobalt, said process comprising the steps of: a) providing an aqueous metal sulfate feed solution comprising nickel and / or cobalt ions and impurities; b) separating a first part of impurities from the metal sulfate feed solution to obtain a raffinate; c) optionally subjecting the raffinate to an ion exchange treatment to remove a second part of impurities; d) subjecting at least a portion of the optionally ion exchanged raffinate as electrolyte to electrowinning to produce nickel and / or cobalt.Brief description of the Figures

[0020] Figure 1 describes a flow sheet as known in the prior art.

[0021] Figure 2 describes a flow sheet as known in the prior art.

[0022] Figure 3 describes a flow sheet according to an embodiment of the invention.

[0023] Figure 4 describes a flow sheet according to an embodiment of the invention.Detailed descriptionDefinitions

[0024] The verb “to comprise”, and its conjugations, as used in this description and in the claims is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded.

[0025] Reference to an element by the indefinite article “a” or “an” does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there is one and only one of the elements. The indefinite article “a” or “an” thus usually means “at least one”.

[0026] Reference to certain metals, e.g. nickel and cobalt, is not limited to any oxidation state. For instance, a reference to cobalt may refer to Co(V), Co(IV), Co(lll), Co(ll), Co(l) and Co0.

[0027] In the context of the present invention, the term “raw material feed” refers to one or more feedstocks that comprise any one or a combination of cobalt, nickel, manganese or lithium. Said materials may be included as such or may be included as a compound of the aforementioned metals, or as a mixture of compounds. In some embodiments, said raw material feed may comprise any one or combination of raw materials and recycled materials. Examples of raw materials include, but are not limited to, cobalt hydroxide intermediate precipitate (CHIP), mixed sulfide precipitates (MSP), mixed hydroxide precipitates (MHP), nickel sulfide concentrate and cobalt sulfide concentrate. Examples of recycled materials include, but are not limited to, spent cathode material, and material derived fromrecycled lithium-ion batteries or lithium-ion battery manufacturing scrap, collectively referred to herein as “black mass”.

[0028] In the context of the present invention, the term “CHIP” is to be considered as an abbreviation of the term “cobalt hydroxide intermediate precipitate”. Cobalt hydroxide intermediate is comprised primarily of cobalt and typically has a cobalt content of 25 wt.% to 40 wt.% relative to the total weight of said intermediate product. Typically, said cobalt hydroxide intermediate comprises a significant amount of nickel.

[0029] In the context of the present invention, the term “MHP” is to be considered as an abbreviation of the term “mixed hydroxide precipitate”. Mixed hydroxide precipitate (MHP) is a solid intermediate product of nickel metallurgy derived from processing laterite ores which contains primarily nickel and a minor amount of cobalt. Alternatively, or additionally, MHP may be obtained from cobalt and / or nickel containing materials produced as production waste during preparation of cathode materials or obtained from battery recycling processes.

[0030] In the context of the present invention, the term “organic phase” is to be understood as synonymous for the term “solvent” or “solvent mixture” and designates a liquid composition comprising one or more extractants, optionally diluents, and optionally one or more modifiers.

[0031] The term “extractant” or “extractant agent” is the active component in the organic phase that extracts the metal species to the organic phase by chemically binding with it and forming a metalextractant complex that is better soluble in the organic phase than in the aqueous phase.

[0032] The “diluent” is an organic molecule or usually a mixture of different organic molecules added to the organic phase to dilute the extractant and allow for dissolution of the metal complexes, improve the physical properties of the organic phase, e.g. phase separation phenomena, and decrease its cost, given that diluents are usually cheaper than extractants. Diluents are typically kerosene fractions and may be selected from aliphatic or aromatic hydrocarbons, naphthene or mixtures thereof. Preferably, the diluent is a kerosene-based petroleum fraction such as Escaid, Elixore, Shellsol, Isopar, etc.

[0033] The organic phase may also contain a “modifier”. A modifier is sometimes added to improve the solubility of the metal complexes into the organic phase, to alter the physical properties of the solvent such to avoid crud formations or third-phase formation as these phenomena are unwanted in solvent extraction. Modifiers can also be added to prevent chemical degradation of extractant or diluent. However, modifiers may impair the selectivity of the organic phase as these may participate in the complex formation of the metals with the extractant.

[0034] The term “loaded solvent” refers to the organic phase that comprises the extracted metals.

[0035] The term “cobalt solvent extraction” or “Co SX” refers to solvent extraction, wherein the organic phase has a high affinity for cobalt such that the bulk of the cobalt ends up in the loaded solvent instead of the raffinate. Cobalt solvent extraction is preferably not present in the process of the invention.

[0036] The term “nickel solvent extraction” or “Ni SX” refers to solvent extraction , wherein the organic phase has a high affinity for nickel such that the bulk of the nickel ends up in the loaded solvent instead of the raffinate. Nickel solvent extraction is preferably not present in the process of the invention.

[0037] The terms “aqueous solution” and “aqueous medium” are used interchangeably, and are used to refer to water-based solutions.

[0038] The term “ion exchange” refers to interchange of one species of ion present in an insoluble solid with another ion present in a solution. In the context of the present invention, the ion exchanger is a cationic exchanger.

[0039] The term “bleeding” refers to sacrificing part of a material to prevent accumulation of materials. The process of the present invention preferably encompasses bleeding. Bleeding is well known to the skilled person and involves sacrificing part of a material in a step, e.g. part of the mother liquor in the crystallizer or the electrolyte in the electrowinning. Sacrificing part of the material prevents the accumulation of impurities which is especially useful in continuous processes. Without bleeding accumulation of impurities occurs, because the feeds comprise impurities but the outputs are stripped from at least a part of the impurities, meaning that the impurities can partially remain in the mixture. Accumulation of impurities may lead to a variety of problems such as precipitation, change in viscosity, reduced effectiveness of separation, unwanted impurities in the end product etc. Thus, bleeding is preferably present.

[0040] The material discarded from bleeding is known as “bleed” or “bleed solution”. As bleeding discards the material from which the desired compound, i.e. nickel and / or cobalt, is produced, the bleed comprises a substantial amount of nickel and / or cobalt. Thus, it is preferred that bleeding is followed by recovery steps for recovering nickel and / or cobalt from the bleed. Typically, the recovered product is a commercial product and / or used upstream.

[0041] As used herein, “crystallization”, “crystallizing” or “crystallized” refers to the process of forming a crystal network that selectively and slowly formed from the metal in a solution, resulting in a pure crystalline compound (at least as indicated by x-ray diffraction). Typically, crystallization occurs in a crystallizer in which crystallized material is formed in a mother liquor from non-crystallized material.

[0042] The term “mother liquor” is well known to the skilled person and refers to the supersaturated solution of a crystallization process. Typically, the mother liquor refers to the solution obtained after filtration of the crystallization. In the context of the present invention, the term mother liquor may also refer to the liquid present in the slurry during the crystallization.

[0043] The term “battery-grade”, as used in “battery grade cobalt sulfate” refers to the quality, i.e. the level of impurities. Frequently, 99,9% purity is required. The exact specifications may very depending on the intended use and the specifications of the batteries, but this term is nevertheless well understood by a person skilled in the art.

[0044] The term “electrowinning” is a process where metals are recovered in an electrolytic cell. An aqueous solution containing metal sulfates is subjected to an electric potential, resulting in metal cations being drawn to the surface of the negative pole, the cathode where they are deposited as pure metal.

[0045] The terms “plates, squares, rounds and crowns” refer to different geometrical shapes of the metallic cathode material.

[0046] Unless stated otherwise, the electrode potentials are standard electrode potentials in volt relative to the standard hydrogen electrode at a temperature of 298.15 K, effective concentration of 1 mol / L for each aqueous species, and an absolute partial pressure of 1 .0 atm.The process of the invention

[0047] A first aspect of the present invention relates to a process for producing nickel and / or cobalt, said process comprising the steps of: a) providing an aqueous metal sulfate feed solution comprising nickel and / or cobalt ions and impurities; b) separating a first part of impurities from the metal sulfate feed solution to obtain a raffinate; c) optionally subjecting the raffinate to an ion exchange treatment to remove a second part of impurities; d) subjecting at least a portion of the optionally ion exchanged raffinate as electrolyte to electrowinning to produce nickel and / or cobalt.

[0048] The process of the present invention has the advantage that the electrowinning step is utilized despite the presence of impurities in the electrolyte, because electrowinning is fairly forgiving with regard to the levels of elements such as magnesium and manganese in the electrolyte. Thereby the production of cobalt and / or nickel is improved as the need for extensive and expensive separation treatments is reduced . Accordingly, the process of the present invention preferably does not comprise Cyanex solvent extraction.

[0049] The process of the present invention typically involves the use of a base in a variety of steps. It is especially preferred that KOH is used as base when possible. The use of KOH has the advantage that K2SO4 is produced as side product, while the traditional processes typically employ NaOH as base which results in Na2SO4 as side product. Surprisingly, the use of potassium does not interfere with the efficiency of the process and results in K2SO4, which is a much more valuable side product as compared to Na2SO4.

[0050] In a preferred embodiment, the process is used to produce nickel. In this embodiment, cobalt is part of the impurities. In this embodiment, any reference to “nickel and / or cobalt” thus refers to nickel. In another preferred embodiment, the process is used to produce cobalt. In this embodiment, nickel is part of the impurities. In this embodiment, any reference to “nickel and / or cobalt” thus refers to cobalt. In yet another preferred embodiment, the process is used to produce both cobalt and nickel. In this embodiment, any reference to “nickel and / or cobalt” thus refers to the combination of nickel and cobalt.

[0051] The process of the present invention may be a continuous process or a batch process. Alternatively, some steps of the process may be performed continuous and other steps may be performed batchwise. Preferably, the process of the present invention is a continuous process.

[0052] Typically, the aqueous metal sulfate feed solution of step a) comprises at least 50 wt.%, preferably 55 wt.%, more preferably 60 wt.% most preferably 70 wt.%, of the metal to be produced, i.e. nickel and / or cobalt, relative to the total metal content, and the total content of calcium, magnesium, zinc, cadmium, copper and manganese in the feed solution is at most 40 wt.%, preferably 30 wt.%, more preferably 20 wt.%, most preferably 10 wt.%, relative to the total metal content of the feed solution.

[0053] Preferably, the calcium content is 0.01 -5 wt.% relative to the total metal content, more preferably 0.025-2.5 wt.%, even more preferably 0.05-1 wt.%, most preferably 0.08-0.6 wt. %.

[0054] Preferably, the magnesium content is 0.5-30 wt.% relative to the total metal content, more preferably 1-25 wt.%, even more preferably 5-15 wt.%, most preferably 11 -13 wt. %.

[0055] Preferably, the zinc content is 0.05-10 wt.% relative to the total metal content, more preferably 0.1-5 wt.%, even more preferably 0.15-3 wt.%, most preferably 0.2-2 wt. %.

[0056] Preferably, the copper content is 0.00-15 wt.% relative to the total metal content, more preferably 0.01-10 wt.%, even more preferably 0.25-7.5 wt.%, most preferably 0.5-6 wt. %.

[0057] Preferably, the manganese content is 0.1 -35 wt.% relative to the total metal content, more preferably 1-30 wt.%, even more preferably 2-25 wt.%, most preferably 4-20 wt. %.

[0058] The aqueous metal sulfate feed solution of step a) may be obtained by reacting the raw material feed, preferably a metal hydroxide with sulfuric acid. In the embodiment in which nickel is produced, the aqueous metal sulfate feed solution is thus preferably obtained by reacting a nickel containing raw material feed, preferably nickel hydroxide, with sulfuric acid. In the embodiment in which cobalt is produced, the aqueous metal sulfate is thus preferably obtained by reacting a cobalt salt, preferably cobalt hydroxide, with sulfuric acid.

[0059] Preferably, the leached material is first discarded of iron and / or copper before being used as aqueous metal sulfate feed solution. Thus, in this embodiment the aqueous metal sulfate feed solution of step a) preferably comprises at most 0.1 wt.%, preferably 0.05 wt.%, more preferably 0.02 wt.%, most preferably 0.01 wt.% of copper relative to the total metal content and / or the aqueous metal sulfate feed solution of step a) comprises at most 0.1 wt.%, preferably 0.05 wt.%, more preferably 0.02 wt.%, most preferably 0.01 wt.% iron relative to the total metal content.

[0060] Iron removal is well known to the skilled person. Typically, iron and aluminium are removed concomitantly by increasing the pH. The pH may be increased by any base such as a slaked lime (CaO), NaOH, KOH etc. Preferably, the base is slaked lime or KOH. Preferably, the iron content is after iron removal at most 100 mg / L, more preferably at most 10 mg / L, most preferably 1 mg / L.

[0061] Copper removal is also well known to the skilled person and can be removed by chemical precipitation, neutralization, adsorption on different adsorbents, cementation or a combination of these methods. Cementation is a spontaneous electrochemical reaction of the metal ion to its elemental metallic state with the consequent oxidation of a sacrificial metal. As cementation agent, metallic cobalt, nickel or iron can be used. Alternatively, copper can be removed by pH increase, ion exchange or sulfide precipitation. Preferably, the copper content is after copper removal at most 100 mg / L, more preferably at most 10 mg / L, most preferably 1 mg / L.

[0062] Alternatively, the aqueous metal sulfate feed solution of step a) may be obtained by dissolving impure CoSO4 crystals.

[0063] In step b) a first part of impurities are removed from the aqueous metal sulfate feed solution to obtain a raffinate. Typically, the first part of impurities comprises zinc. Insofar as copper was not removed prior to step b), or only partly removed prior to step b), the separation step b) preferably removes copper. In an especially preferred embodiment, the separation involves an ion exchange treatment. This embodiment has the advantage that the process is devoid of any solvent extraction treatment, meaning that the process is less harmful to the environment, less waste products are produced, less dangerous to the workers and overall more safe. Preferably, the ion exchange treatment is used to remove copper and / or zinc.

[0064] Removal of copper via ion exchange treatment is known to the skilled person. Ion exchange treatment for removing copper has been described in CN106399687 and CN109881006, both incorporated by reference. Typically, removal of copper via ion exchange treatment concerns the use of iminodiacetic acid based, bis-picolylamine based or aminomethyl phosphonic acid based resins.

[0065] Similarly, the removal of zinc via ion exchange treatment is known to the skilled person, ion exchange treatment for removing zinc has been described in EP2960209, incorporated by reference. Typically, removal of copper via ion exchange treatment concerns the use of iminodiacetic acid based or aminomethyl phosphonic acid based resins. Preferably, the copper content is after copper removal at most 100 mg / L, more preferably at most 10 mg / L, most preferably 1 mg / L.

[0066] It is especially preferred that an ion exchange treatment is used to remove copper and zinc concomitantly. In another preferred embodiment, copper and zinc are removed consecutive.

[0067] Typically, the raffinate obtained from this ion exchange treatment comprises cobalt, magnesium, manganese, and nickel. Preferably the raffinate comprises:- 60-85 wt.% of nickel and / or cobalt relative to the total metal content;- 5-30 wt.% of magnesium relative to the total metal content;- 4-20 wt.% of manganese relative to the total metal content.

[0068] Preferably, the ion exchange treatment removes 0.1-15 g / L of copper, preferably 0.2-12 g / L, more preferably 0.3-10 g / L, most preferably 0.5-7 g / L, and / or 0.1-10 g / L of zinc, more preferably 0.2-5 g / L, most preferably 0.25-2.5 g / L.

[0069] In another preferred embodiment, the separation of step b) is achieved by solvent extraction. Typically, the solvent extraction comprises:- subjecting the aqueous metal sulfate feed solution to a solvent mixture to obtain a loaded solvent comprising the first part of impurities and an aqueous phase comprising metal sulfate;- separating the aqueous phase from the loaded solvent to obtain the raffinate.

[0070] The SX in this embodiment is used to remove impurities instead of extracting cobalt and / or nickel (e.g. using Cyanex 272 to extract cobalt). In other words, the majority of the cobalt and / or nickel are in the raffinate instead of the loaded solvent. According to this preferred embodiment, only a marginal amount of cobalt and / or nickel are present in the loaded solvent and may be recovered in a subsequent step. As Co / Ni SX is avoided, the process is further optimized as less salt is necessary to regenerate cobalt and / or nickel from the loaded solvent.

[0071] Preferably, the solvent extraction comprises an alkyl phosphorus-based extractant. More preferably, the alkyl phosphorus-based extractant is an alkylphosphoric acid-based extractant. Most preferably, the alkylphosphoric-based extractant is di(2-ethylhexyl)phosphoric acid.

[0072] Typically, the solvent extraction (SX) removes the impurities calcium, zinc and / or manganese. Thus, it is preferred that the loaded solvent comprises calcium, zinc and / or magnesium. Preferably, the raffinate comprises- 75-99 wt.% of nickel and / or cobalt relative to the total metal content, more preferably 80-95 wt.%, even more preferably 82-90 wt.%;- 0.5-30 wt.% of magnesium relative to the total metal content, more preferably 1 -15 wt.%, even more preferably 5-15 wt.%.

[0073] The use of solvent extraction in step b) instead of ion exchange has the benefit that at least a part of the manganese is removed. Thus, preferably the raffinate, in the embodiment in which step b) concerns solvent extraction (SX), comprises at most 0.1 wt.% of manganese, more preferably 0.05 wt.%, most preferably 0.01 wt.%.

[0074] Preferably, the raffinate obtained from SX comprises at most 20 wt.% of potassium, more preferably 10 wt.%, most preferably 5 wt.%.

[0075] Preferably, the solvent extraction removes 0.005-10 g / L of copper, preferably 0.01 -5 g / L, more preferably 0.05-2.0 g / L, most preferably 0.5-1 g / L; 0.01 -40g / L of manganese, preferably 0.05-20 g / L, more preferably 0.1 -10 g / L, most preferably 0.5-5 g / L, and / or 0.01-10 g / L of zinc, more preferably 0.05- 5.0 g / L, most preferably 0.1 -2.0 g / L.

[0076] Solvent extraction is well known and can typically be described as follows: n (R-H)org+ (Mn+)aq~ (Rn-M)org + n (H+)aq

[0077] Herein, R-H is the solvent in acidic form, Mn+is the metal to be extracted, e.g. manganese, calcium, zinc etc, and n is the oxidation state of the metal. In order to shift the equilibrium to the right and thereby maximizing the extraction of the metal, a neutralizer is preferably added.

[0078] Typically, sulfuric acid is used during the solvent extraction as acid and the neutralizer preferably comprises a base selected from NaOH or KOH. More preferably, the neutralizer comprises KOH.

[0079] In an especially preferred embodiment, the solvent extraction also removes a part of the nickel and / or cobalt. Thus, in this preferred embodiment the loaded solvent comprises nickel and / or cobalt, preferably the loaded solvent comprises 0.01 -70 wt.% of nickel and / or cobalt relative to the total metal content of the loaded solvent, more preferably 0.1 -50 wt.%, most preferably 1 -25 wt.%.

[0080] Extraction of nickel and / or cobalt to the loaded solvent may be achieved by using a certain quantity of solvent mixture, preferably the extraction of cobalt and / or nickel is achieved by using an O / A[Impurities] ratio as defined as follows: O / A = r xmlimpurities / gqueous phase[Extraction] r x mo^extraction / ^solvent

[0081] Herein, O / A is the organic to aqueous phase ratio, [impurities] is the molar sum of the metal impurities per litre. Preferably, the sum of the impurities is defined as the sum of calcium, zinc and / or manganese. Herein, [extraction] is the concentration of M2+slots, i.e. available binding sites, on the solvent. Hereby, a molextraction is defined by the amount of mol M2+the active component can extract. For instance, if two molecules of active component bind to one Zinc(ll) ion, 1 mol of active component per liter is equal to 0.5 molextraction per liter.

[0082] The parameter r determines the excess of solvent applied to extract the desired metal cobalt and / or nickel vs the sum of the impurities, defined as the sum of calcium, zinc and / or manganese, i.e. r = 1 means that the total amount of M2+that can be extracted equals the total amount of impurities. Thus, in this embodiment r > 1. Preferably, r is 1.01 -10, more preferably r is 1.1-5, most preferably r = 1 .5-2.

[0083] This embodiment has the advantage that a loaded solvent comprising nickel and / or cobalt can be used to generate very pure nickel and / or cobalt. As the solvent mixture used in step b) typically has a low affinity to nickel and / or cobalt, as the bulk of the nickel and / or cobalt remains in the raffinate, the nickel and / or cobalt present in the loaded solvent can easily be removed from the loaded solvent byreplacing it with a metal with a higher affinity to the extractant. Hence, in this embodiment, the process preferably further comprises: m) stripping the loaded solvent of nickel and / or cobalt sulfate by subjecting the loaded solvent to an aqueous metal salt solution, thereby obtaining an aqueous nickel and / or cobalt sulfate solution and a loaded solvent stripped from nickel and / or cobalt sulfate, wherein the solvent has a higher affinity for the metal of said metal salt than for nickel and / or cobalt, preferably the salt is manganese and / or zinc sulfate.

[0084] The resulting nickel and / or cobalt sulfate solution is very pure, preferably the nickel and / or cobalt solution comprises 3-10 wt.%, more preferably 4-10 wt.%, most preferably 5-10 wt.% of nickel and / or cobalt relative to the total weight content. Due to the high purity of the solution, the nickel and / or cobalt sulfate solution can be subjected to crystallization in order to produce nickel / and or cobalt sulfate crystals with a high purity. More preferably, the nickel and / or cobalt sulfate crystals have a battery grade purity.

[0085] The solvent mixture may be recovered from the loaded solvent obtained from step m) by treating the loaded solvent with an acidic solution to remove the impurities.

[0086] Thus, in a preferred embodiment the process further comprises: n) recovering the solvent mixture for solvent extraction by treating the loaded solvent obtained from step m) with an acidic solution to remove the impurities from the loaded solvent; and / or o) crystallizing the aqueous nickel and / or cobalt sulfate solution to obtain crystallized nickel and / or cobalt sulfate.

[0087] Typically, the crystallization of nickel and / or cobalt sulfate in step o) is done by crystallizing the uncrystallized nickel and / or cobalt sulfate to form a crystallized nickel and / or cobalt sulfate in a mother liquor, said mother liquor comprising a remaining uncrystallized nickel and / or cobalt sulfate. The crystallized nickel and / or cobalt sulfate is then separated from the mother liquor to obtain nickel and / or cobalt sulfate crystals. The mother liquor is preferably bled in order to prevent accumulation of impurities.

[0088] In an alternative preferred embodiment, the separation of step b) concerns solvent extraction, but the amount of solvent mixture is such that no or at most a negligible amount nickel and / or cobalt is extracted by the solvent mixture.

[0089] Step c) concerns an optional ion exchange treatment in order to remove a second part of the impurities. Step c) is typically present if the process of the present invention is used to produce either nickel or cobalt. Step c) may also be used to remove other impurities such as copper, cadmium, zinc. Preferably, step c) is present, and the process of the present invention produces cobalt and the second part of impurities comprises nickel, or alternatively the process of the invention produces nickel and the second part of the impurities comprises cobalt.

[0090] Removing nickel from a cobalt solution via ion exchange is known to the skilled person. Herein, it is preferred that the ion exchange treatment is a iminodiacetic acid, bis-picolylamine or aminomethyl phosphonic acid based Ion exchange.

[0091] The alternative, i.e. removing cobalt from a nickel solution via ion exchange, is also known to the skilled person. Herein, it is preferred that the ion exchange treatment is a Cyanex 272-impregnated ion exchange treatment.

[0092] The ion exchanged raffinate obtained from step c), preferably comprises:- 80-90 wt.% of cobalt relative to the total metal content;10-20 wt.% of magnesium relative to the total metal content, or- 80-90 wt.% of nickel relative to the total metal content.10-20 wt.% of magnesium relative to the total metal content.

[0093] More preferably, the ion exchanged raffinate further comprises:2-25 wt.% of manganese relative to the metal content and / or1-25 wt.% of potassium relative to the total metal content.

[0094] Preferably, the ion exchange removes 0.01 -35 g / L of impurities, more preferably 0.1-20 g / L of impurities, most preferably 1 -10 g / L of impurities.

[0095] In an alternative preferred embodiment, the process of the invention produces nickel or cobalt, but optional step c) is absent and instead an ion exchange treatment is utilized prior to step b) to remove nickel or cobalt.

[0096] In step d), at least a part of the raffinate, said raffinate optionally being ion exchanged in step c), is used as electrolyte in electrowinning to produce nickel and / or cobalt as reduced metal, i.e. Co(0) and / or Ni(0). Typically, electrowinning involves passing an electrical current from an inert anode through an electrolyte so that metal, i.e. nickel and / or cobalt, is deposited on the cathode. As the electrolyte of the present invention comprises nickel and / or cobalt sulfate, nickel and / or cobalt are present in oxidation state 2. Thus, the following electrochemical reactions may be present at the cathode:- E°h= -0.236 V-E°h= -0.28 V- 2H+(aq) + 2 e ^ H2(g) E°h= 0 V

[0097] On the anode, the following electrochemical reaction is typically present:- H2O (I) -> 2H+(aq) +1 / 2O2(g) + 2e- E°h= 1 .23 V.

[0098] The remaining impurities present in the electrolyte are preferably sodium, potassium, magnesium and manganese. As the elements of these impurities are less noble than nickel and cobalt, they will not be deposited on the cathode which is evident from electrode potential of the reduction reactions associated with these impurities:Na+(aq) + e - Na° (s) E°h= -2.71 VK+(aq) + e - K° (s) E°h= -2.93 V- Mg2+(aq) + 2e_— Mg° (s) E°h= -2.37 V- Mn2+(aq) + 2e_Mn° (s) E°h= -1.18V

[0099] Therefore, electrowinning can effectively be used to produce nickel and / or cobalt despite the impurities being present that typically would have been removed via solvent extraction.

[0100] The electrolyte preferably comprises magnesium, manganese and / or potassium, preferably magnesium in a concentration of 1 -20 wt.% relative to the total metal content, manganese in aconcentration of 2-20 wt.% relative to the total metal content, and / or potassium in a concentration of I Q- 30 wt.% relative to the total metal content.

[0101] In a preferred embodiment, the content of magnesium, manganese and potassium is a concentration of 20-60 wt.%, more preferably 30-50 wt.%, most preferably 35-45 wt.% relative to the total metal content.

[0102] Preferably the electrolyte comprises magnesium in a concentration of 0.1 -20 g / L, manganese in a concentration of 1-25 g / L and / or potassium in a concentration of 10-20 g / L.

[0103] Surprisingly, despite the presence of impurities of magnesium, manganese and / or potassium in the above-mentioned amounts, the electrowinning step still effectively produces nickel and / or cobalt.

[0104] As the total amount of impurities will accumulate over time in the electrolyte, the electrolyte is preferably bled.General recovery of bleed

[0105] Bleeding may be used in various steps of the process of the present invention including but not limited to electrowinning and crystallization. Below various methods for recovering nickel and / or cobalt from bleed in general are given.

[0106] In a preferred embodiment, bleed may be basified to obtain nickel and / or cobalt hydroxide. Any suitable base may be used for basifying nickel and / or cobalt sulfate, preferably the base is selected from NaOH, KOH, LiOH or NH4OH more preferably the base is KOH. As the solubility product of nickel and / or cobalt hydroxide is much lower than the salts of the impurities, precipitation can be used to separate nickel and / or cobalt hydroxide from the impurities. Nickel and / or cobalt hydroxide are already a commercially valuable product as such, but it may also be used as base in an upstream step, for instance as neutralizer in step b) in the embodiment step b) involves solvent extraction.

[0107] In another preferred embodiment, bleed may be reacted with a sulfidizing agent to obtain NiS and / or CoS. Any suitable sulfidizing agent may be used such as H2S, NaHS, Na2S, K2S, (NH^S, Li2S or KHS. Sulfides which are insoluble under the described conditions such as CuS, are not considered a suitable source of sulfides or sulfidizing agents according to the invention. Thus, preferably, the bleed is reacted with a sulfidizing agent in an acidic aqueous medium to obtain a slurry comprising a solid phase comprising nickel and / or cobalt sulfide and an aqueous phase comprising one or more impurities; and the solid phase can then be separated from the aqueous phase by means known to the skilled person, such as filtration. The solid phase comprising NiS and / or CoS is already a commercially valuable product, but the NiS and CoS may also be converted into NiSO4 and / or CoSO4. Conversion from sulfide into sulfate may be achieved by oxidation in an aqueous medium. The aqueous medium comprising NiSO4 and / or CoSO4 can then be optionally subjected to an ion exchange treatment to further purify the NiSO4 and / or CoSO4 if required. The optional ion exchanged aqueous solution of NiSO4 and / or CoSO4 can then be subjected to a crystallizer to obtain pure NiSO4 and / or CoSO4 crystals. The mother liquor in the crystallizer may be bled as well, the bleed obtained from this step may be used upstream, preferably this bleed is added to the bleed which reacts with the sulfidizing agent.

[0108] In yet another preferred embodiment, bleed may be used directly upstream.

[0109] In an especially preferred embodiment, the process of the invention further comprises: e) bleeding a part of the electrolyte in step d) to obtain a bleed solution.

[0110] Preferably, the bleed solution comprises:- 40-80 wt.% of nickel and / or cobalt relative to the total metal content;1-20 wt.% of magnesium relative to the total metal content;

[0111] More preferably, the bleed solution further comprises:- 2-20 wt.% of magnesium relative to the total metal content;- 2-20 wt.% of manganese relative to the total metal content; and / or- 5-30 wt.% of potassium relative to the total metal content.

[0112] In a preferred embodiment, the bleed solution has a nickel and / or cobalt concentration of at least 1 g / L less than the incoming electrolyte, i.e. the optionally ion exchanged raffinate, more preferably this difference is 2-30 g / L, even more preferably the difference is 3-20 g / L, most preferably the difference is 4-10 g / L.

[0113] Preferably, the bleed solution comprises at least 20 g / L of nickel and / or cobalt, more preferably 30-60 g / L, even more preferably 40-50 g / L, most preferably 42-46 g / L. Bleeding such a high amount of electrolyte has the advantage that battery-grade nickel and / or cobalt can be obtained from electrowinning despite the high concentrations of impurities.

[0114] The bleed solution may be subjected to any one of the general bleed recovery methods described above. In an especially preferred embodiment, the bleed solution is subjected to steps f) and g) described below.Step f) and step q)

[0115] Preferably, the process of the invention further comprises: f) treating the bleed solution of step e) with a sulfidizing agent in an acidic aqueous medium, thereby obtaining a slurry comprising a solid phase comprising nickel and / or cobalt sulfide, and an aqueous phase comprising one or more impurities; and g) separating the solid phase from the aqueous phase.

[0116] Sulfidizing agents are known to the skilled person, the sulfidizing agent converts nickel and / or cobalt sulfate into nickel and / or cobalt sulfide. In a preferred embodiment, the sulfidizing agent is selected from H2S, NaHS, KHS and combinations thereof.

[0117] Separating the solid phase from the aqueous phase is well known by the skilled person and typically involves filtration.

[0118] The solid phase comprising nickel and / or cobalt sulfide is already a commercially valuable product and may thus be one of the end products of the process of the invention. Alternatively, the nickel and / or cobalt sulfide may be converted back into nickel and / or cobalt sulfate, preferably by leaching the solid residue with a mineral acid, more preferably H2SO4, thereby obtaining a cobalt- and / or nickel- bearing solution.

[0119] In a preferred embodiment the process of the invention further comprises:h) dissolving the solid phase obtained from step g) under oxidative conditions to obtain an aqueous solution of cobalt and / or nickel sulfate. i) optionally subjecting said aqueous solution to a purification step, preferably the purification step is ion exchange; j) subjecting the optionally purified aqueous solution to crystallization to form a mother liquor comprising crystallized nickel and / or cobalt sulfate and uncrystallized nickel and / or cobalt sulfate; k) separating the crystallized nickel and / or cobalt sulfate from the mother liquor; l) bleeding the mother liquor and introducing the bleed in an upstream step, preferably the bleed is introduced in the electrolyte of step d) or in the acidic aqueous medium of step f).

[0120] It is especially preferred that the step h) involves the use of O2 or Ch, more preferably O2. Most preferably, step h) involves autoclave leaching using O2. Step h) typically involves separation of the aqueous solution comprising nickel and / or sulphate from the insoluble solids that remain after the oxidation.

[0121] Preferably, the nickel and / or cobalt sulfate crystals have a battery grade purity.

[0122] In a preferred embodiment, a second part of the raffinate obtained from step b) or the ion exchanged raffinate obtained from step c) is not used in electrowinning but used to obtain a nickel and / or cobalt salt. Accordingly, the process of the present invention preferably further comprises: p) subjecting a second portion of the optionally ion exchanged raffinate to crystallisation to form crystallized nickel and / or cobalt sulfate in a mother liquor, the mother liquor comprising uncrystallized nickel and / or cobalt sulfate; q) separating the crystallized nickel and / or sulfate from the mother liquor.

[0123] Preferably, the process further comprises: r) bleeding the mother liquor to obtain a bleed solution.

[0124] Preferably, the bleed solution comprises 100 - 220 g / L of nickel and / or cobalt, more preferably 110 - 180 g / L, most preferably 120 - 170 g / L.

[0125] The bleed solution may be subjected to any one of the preceding recovery steps. It is especially preferred that the process further comprises: s) treating the bleed solution of step r) with a sulfidizing agent in an acidic aqueous medium, thereby obtaining a slurry comprising a solid phase comprising nickel and / or cobalt sulfide and an aqueous phase comprising one or more impurities; and t) separating the solid phase from the aqueous phase.

[0126] The bleed solution preferably comprises 100-220 g / L of nickel and / or cobalt, more preferably 110-180 g / L, most preferably 120-170 g / L.

[0127] In an alternative embodiment, the bleed solution obtained from step e) is basified to obtain a nickel and / or cobalt hydroxide. Nickel and / or cobalt hydroxide can be separated from impurities such as magnesium by precipitation. Preferably, the nickel and / or cobalt hydroxide is used in an upstream process, more preferably the nickel and / or cobalt hydroxide is used during pre-leaching. In this embodiment, it is especially preferred that the basifying agent is KOH.Preferred processes

[0128] Preferably, the process of the present invention involves bleeding the electrolyte, in other words it is preferred that the process comprises steps a), b), d), e). It is especially preferred that sulfidization is used to recover nickel and / or cobalt from the bleed solution, i.e. it is preferred that the process comprises steps a), b), d), e), f) and g).

[0129] In an especially preferred embodiment, the process of the invention comprises steps a), b), c), d), e), f), g), h), i), j), k) and I). In another preferred embodiment, the process of the invention comprises steps a), b), d), e), f), g), m), n) and o). In yet another preferred embodiment, the process ofthe invention comprises steps a), b), c), d), e), f), g), m), n) and o). In another preferred embodiment, the process of the invention comprises steps, a), b), c), d), e), f), g), p), q), r), s).

[0130] It is especially preferred that the bleed solution of step r) is mixed with the bleed solution of step e) before and / or during treatment with a sulfidizing agent. In other words, it is preferred that step s) is step f), and step t) is step g).

[0131] The invention is exemplified by the two embodiments depicted in Figures 3-4.Detailed description of the Figures

[0132] Figure 3 depicts the process of the invention according to a first preferred embodiment, in particular it depicts the following process for producing cobalt: a) providing an aqueous metal sulfate feed solution comprising cobalt ions and impurities; in particular by: a1 . leaching raw material feed comprising Co(OH)2with H2SO4 and SO2; a2. removal of impurities, e.g. iron precipitation b) separation of a first part of impurities from cobalt to obtain a raffinate, in particular by subjecting the aqueous metal sulfate solution to ion exchange to remove copper and zinc; c) the raffinate is subjected to ion exchange to remove a second part of impurities, i.e. nickel, from cobalt; d) the ion exchanged raffinate is then subjected as electrolyte to electrowinning to produce Co0cathodes; e) a part of the electrolyte is bled to obtain a bleed solution, which advantageously prevents magnesium and manganese accumulation; f) a part of the bleed solution is treated with a sulfidizing agent in an acidic aqueous medium, to obtain a slurry comprising a solid phase comprising nickel and / or cobalt sulfide, and an aqueous phase comprising one or more impurities; and f1 . another part of the bleed solution is used in the leaching step a1 . g) the solid phase is separated from the aqueous phase by filtration; g1 . herein an additional side product is produced by reacting the MnSO4 of the aqueous phase with KOH and CO2 to precipitate MnCOs; h) the solid phase obtained from step g) is dissolved under oxidative conditions to obtain an aqueous solution of cobalt sulfate; i) the aqueous cobalt sulfate solution is subjected to ion exchange to remove copper, zinc and manganese;j) the ion exchanged aqueous solution is subjected to crystallization to form a mother liquor comprising crystallized cobalt sulfate and uncrystallized cobalt sulfate; k) the crystallized cobalt sulfate is separated from the mother liquor; l) the mother liquor is bled and mixed with the bleed stream from step f).

[0133] Figure 4 depicts the process of the invention according to a second preferred embodiment, in particular it depicts the following process for producing cobalt: a) providing an aqueous metal sulfate feed solution comprising cobalt ions and impurities; in particular by: a1 . leaching a Co(OH)2 feed with H2SO4 and SO2; a2. impurity removal, e.g. iron and copper; a3. nickel removal by ion exchange; b) separation of a first part of impurities from metal sulfate feed solution to obtain a raffinate, in particular by D2EHPA solvent extraction to obtain a raffinate comprising cobalt sulfate and a loaded solvent comprising impurities and cobalt sulfate; d) subjecting the raffinate as electrolyte to electrowinning to produce Co0cathodes; e) bleeding the electrolyte to obtain a bleed solution; f) reacting the bleed solution with H2S in an acidic aqueous medium, to obtain a slurry comprising a solid phase comprising nickel and / or cobalt sulfide, and an aqueous phase comprising one or more impurities; g) separating the solid phase from the aqueous phase; m) stripping the loaded solvent of cobalt sulfate by subjecting the loaded solvent to an acidic aqueous MnSCM solution, thereby obtaining an aqueous cobalt sulfate solution and a loaded solvent stripped from cobalt sulfate; n) recovering the solvent for solvent extraction by treating the loaded solvent obtained from step m) with a sulfuric acid solution to remove the impurities from the loaded solvent;0) crystallizing the aqueous nickel and / or cobalt sulfate solution in a mother liquor to obtain crystallized cobalt sulfate;- separating the crystallized cobalt sulfate from the mother liquor; bleeding part of the mother liquor and adding the bleed solution to step f).

Claims

CLAIMS1 . A process for producing nickel and / or cobalt, said process comprising the steps of: a) providing an aqueous metal sulfate feed solution comprising nickel and / or cobalt ions and impurities; b) separating a first part of impurities from the metal sulfate feed solution to obtain a raffinate; c) optionally subjecting the raffinate to an ion exchange treatment to remove a second part of impurities; d) subjecting at least a portion of the optionally ion exchanged raffinate as electrolyte to electrowinning to produce nickel and / or cobalt.

2. The process according to claim 1 , wherein the aqueous metal sulfate solution of step a) is obtained by reacting a raw material feed, preferably a metal hydroxide, with sulfuric acid.

3. The process according to claim 1 or 2, wherein step c) is present.

4. The process according to claim 3, wherein- cobalt is produced and the second part of impurities comprises nickel, or nickel is produced and the second part of impurities comprises cobalt.

5. The process according to any one of the preceding claims, wherein the electrolyte comprises magnesium, manganese and / or potassium.

6. The process according to claim 5, wherein the electrolyte comprises magnesium in a concentration of 0.1-20 g / L, manganese in a concentration of 1 -25 g / L and / or potassium in a concentration of I Q- 20 g / L.

7. The process according to any one of the preceding claims, whereby the feed solution of step a) comprises cobalt in an amount of at least 60 wt.% relative to the total metal content of the feed solution and whereby total content of calcium, magnesium, zinc, copper, cadmium and manganese in the feed solution is at most 40 wt.% relative to the total metal content of the feed solution.

8. The process according to any one of the preceding claims, the process further comprising: e) bleeding a part of the electrolyte in step d) to obtain a bleed solution.

9. The process according to claim 8, the process further comprising: f) treating the bleed solution of step e) with a sulfidizing agent in an acidic aqueous medium, thereby obtaining a slurry comprising a solid phase comprising nickel and / or cobalt sulfide, and an aqueous phase comprising one or more impurities; andg) separating the solid phase from the aqueous phase.

10. The process according to claim 9, the process further comprises: h) dissolving the solid phase obtained from step g) under oxidative conditions to obtain an aqueous solution of cobalt and / or nickel sulfate; i) optionally subjecting said aqueous solution to a purification step, preferably the purification step is ion exchange; j) subjecting the optionally purified aqueous solution to crystallization to form a mother liquor comprising crystallized nickel and / or cobalt sulfate and uncrystallized nickel and / or cobalt sulfate; k) separating the crystallized nickel and / or cobalt sulfate from the mother liquor; l) bleeding the mother liquor and introducing the bleed in an upstream, preferably the bleed is introduced in the electrolyte of step d) or in the acidic aqueous medium of step f).

11. The process according to any one of the preceding claims, wherein the separation of step b) is ion exchange and wherein the first part of impurities comprises copper and zinc.

12. The process according to any one of claims 1 -10, wherein the separation in step b) is a solvent extraction, said solvent extraction comprises:- subjecting the aqueous metal sulfate feed solution to a solvent mixture to obtain a loaded solvent comprising the first part of impurities and an aqueous phase comprising metal sulfate, and- separating the aqueous phase from the loaded solvent.

13. The process according to claim 12, wherein the loaded solvent comprises 1 -25 wt.% of nickel and / or cobalt relative to the total metal content of the loaded solvent.

14. The process according to claim 12 or 13, wherein sulfuric acid is added during the solvent extraction and a neutralizer comprising KOH is present during the solvent extraction.

15. The process according to any one of claims 12-14, wherein the solvent extraction is a alkylphosphorus-based extraction, preferably a di(2-ethylhexyl)phosphoric acid extraction, and the first part of impurities comprises calcium, zinc and / or manganese.

16. The process according to any one of claims 12- 15, wherein the loaded solvent obtained from the solvent extraction also comprises nickel and / or cobalt sulfate, and the process further comprising: m) stripping the loaded solvent of nickel and / or cobalt sulfate by subjecting the loaded solvent to an aqueous metal salt solution, thereby obtaining an aqueous nickel and / or cobalt sulfate solution and a loaded solvent stripped from nickel and / or cobalt sulfate, wherein the solvent has19 a higher affinity for the metal of said metal salt than for nickel and / or cobalt, preferably the salt is manganese and / or zinc sulfate.

17. The process according to claim 16, the process further comprising: n) recovering the solvent for solvent extraction by treating the loaded solvent obtained from step m) with an acidic solution to remove the impurities from the loaded solvent; and / or o) crystallizing the aqueous nickel and / or cobalt sulfate solution to obtain crystallized nickel and / or cobalt sulfate.

18. The process according to any one of the preceding claims, further comprising: p) subjecting a second portion of the optionally ion exchanged raffinate to crystallisation to form crystallized nickel and / or cobalt sulfate in a mother liquor, the mother liquor comprising uncrystallized nickel and / or cobalt sulfate; q) separating the crystallized nickel and / or sulfate from the mother liquor.

19. The process according to claim 18, further comprising: r) bleeding the mother liquor to obtain a bleed solution.

20. The process according to claim 19, further comprising: s) treating the bleed solution of step r) with a sulfidizing agent in an acidic aqueous medium, thereby obtaining a slurry comprising a solid phase comprising nickel and / or cobalt sulfide and an aqueous phase comprising one or more impurities; and t) separating the solid phase from the aqueous phase.21 . The process according to claims 9 and 20, wherein the bleed solutions of step e) and step r) are mixed before and / or during treatment with a sulfidizi ng agent.

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