Methods for metal sulfidation

Abstract

The present invention provides a method for producing metal sulfides containing nickel and / or cobalt, the method comprising the steps of: i. forming an aqueous metal sulfate solution by reacting sulfuric acid with a raw material feed containing nickel and / or cobalt in water; ii. crystallizing the metal sulfate from the aqueous metal sulfate solution to form crystalline metal sulfate in a mother liquor containing uncrystallized metal sulfate; iii. separating the crystalline metal sulfate from the mother liquor; iv. reacting at least a portion of the uncrystallized metal sulfate with hydrogen sulfide in an acidic aqueous medium to obtain a slurry consisting of a solid phase containing a metal sulfide precipitate and an aqueous phase containing one or more impurities and sulfuric acid; and v. separating the solid phase and the aqueous phase.

Description

Technical Field

[0001] The present invention relates to a method for processing a metal-containing feed comprising at least one Ni compound and / or at least one Co compound, the feed further comprising impurities. Background Technology

[0002] Nickel is an important industrial metal, primarily used in stainless steel production, non-ferrous corrosion-resistant alloys, electroplating, and alloy steel. High-purity nickel is essential for developing various applications. Nickel with a purity higher than 98% can be obtained from refined nickel ore resources such as nickel sulfide and nickel oxide ores. These ores typically also contain a certain amount of iron. Additionally, cobalt is an important industrial metal, mainly used in alloys, battery materials, catalysts, and pigments.

[0003] The decreasing availability of high-purity nickel resources necessitates new methods and refineries for purifying nickel-containing materials. Similarly, cobalt sources are constrained by limited natural occurrences and their primary origin in politically unstable regions. Such nickel and cobalt refineries will require high-capacity and high-efficiency methods to produce the required quantities and high purity of elemental nickel and / or cobalt, or nickel and / or cobalt compounds. Among other methods, the sulfidation of Ni and / or Co from laterite nickel ore or spent battery materials is considered one of the more promising routes.

[0004] In this regard, Liu S. et al. provided an efficient method for robustly recovering Ni from laterite ore via H2 reduction using sodium thiosulfate (Na2S2O3) as a promoter. It was found that a Ni content of 9.97% and a Ni recovery rate of 99.24% were achieved at 1100 °C using 20 wt% Na2S2O3. (Liu S. et al. (2021), A Robust Recovery of Ni From Laterite Ore Promoted by Sodium Thiosulfate Through Hydrogen-Thermal Reduction, Front. Chem. 9:704012. doi: 10.3389 / fchem.2021.704012.)

[0005] CN 113 802 002 discloses a method for recovering valuable metals from lithium batteries via a wet process. According to this method, waste lithium battery powder is selectively leached under pressure and with the introduction of hydrogen sulfide gas, allowing Mn, Li, and Al metal ions to enter the first-stage leaching solution. Nickel, cobalt, copper, and iron exist as sulfides in the first-stage leaching residue. Only a small amount of sulfuric acid is consumed in this process. The pH of the first-stage leaching solution is then adjusted to remove aluminum and manganese. After the first-stage leaching process, the method requires a complex purification procedure to obtain high-purity Ni.

[0006] However, new methods are needed to provide nickel and / or cobalt with high purity and efficiency for energy and materials applications. Summary of the Invention

[0007] This invention provides a solution to at least one of the aforementioned problems by providing a method for treating metal-containing feedstocks according to claim 1. The sulfidation reaction in step iv. of this method is advantageously carried out in the presence of an inorganic acid. This inorganic acid can be added as is or can be generated in situ by the reaction of NiSO4, NiCl2, CoSO4, or CoCl2 with a sulfiding agent such as hydrogen sulfide in an aqueous reaction medium. Advantageously, according to such an embodiment, the total amount of Co and / or Ni in the aqueous medium increases, which allows for improved recovery efficiency. The process is robust enough to handle Co and / or Ni-containing solutions from impure waste streams. In a particularly preferred embodiment, the inorganic acid is generated in situ by introducing effluent containing NiSO4 or CoSO4 obtained from a NiSO4 crystallization unit, a CoSO4 crystallization unit, or a mixed sulfate crystallization unit, respectively. Detailed Implementation

[0008] Unless otherwise defined, all terms used in this disclosure (including technical and scientific terms) have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. Further guidance, including terminology definitions, is provided to better understand the teachings of this invention. As used herein, the following terms have the following meanings:

[0009] As used herein, “a,” “the,” and “the” refer to both a single referent and multiple referents, unless the context clearly specifies otherwise. For example, “compartment” refers to one or more compartments.

[0010] As used herein, the term "about" when referring to measurable values ​​such as parameters, quantities, durations of time, etc., is intended to cover variations of + / -20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and even more preferably + / -0.1% or less, as well as variations deviating from the specified value within which such variations are suitable for implementation in the disclosed invention. However, it should be understood that the value referred to by the modifier "about" is itself specifically disclosed.

[0011] As used herein, “comprising,” “having,” and “consisting of” are synonymous with “including” or “containing” and are terms that include or are open at the end value, specifying the presence of subsequent items such as components, and do not exclude or preclude the presence of other non-referenced components, features, elements, members, or steps known in the art or disclosed herein.

[0012] Numerical ranges expressed by endpoints include all numbers and fractions contained within that range, as well as the endpoints expressed. All percentages should be understood as weight percentages abbreviated as “weight%” or volume percentages abbreviated as “volume%”, unless otherwise defined or unless the different meaning is obvious to a person skilled in the art from its use and the context in which it is used. Unless otherwise specified, the weight % of an element or compound is calculated relative to the dry weight of the compound or a composition containing said element or compound.

[0013] In the context of this invention, the term "raw material feed" refers to one or more raw materials comprising any or a combination of nickel, cobalt, manganese, or lithium. In some embodiments, the raw material feed may comprise any or a combination of raw materials and recycled materials. Examples of raw materials include, but are not limited to, mixed hydroxide precipitates (MHP), mixed sulfide precipitates (MSP), nickel sulfide concentrates, cobalt sulfide concentrates, nickel laterite, nickel matte, or nickel iron. Examples of recycled materials include, but are not limited to, waste cathode materials and materials derived from recycled lithium-ion batteries or lithium-ion battery manufacturing waste (collectively referred to herein as black matter).

[0014] In the context of this invention, the term "MHP" is considered an abbreviation for the term "Mixed Hydroxide Precipitate." Mixed Hydroxide Precipitate (MHP) is an intermediate product in nickel metallurgy obtained by processing laterite ore, which primarily contains nickel and a small amount of cobalt. MHP is a solid product typically prepared by extracting nickel and cobalt from laterite ore. Alternatively or otherwise, MHP can be obtained from nickel- and / or cobalt-containing hydroxide materials generated as production waste during the preparation of cathode materials or obtained from battery recycling processes.

[0015] In the context of this invention, the term "CHIP" is considered an abbreviation for "cobalt hydroxide intermediate precipitation". Cobalt hydroxide intermediates are primarily composed of cobalt and typically have a cobalt content of 25% to 40% by weight relative to the total weight of the intermediate product. Typically, CHIPs contain a significant amount of nickel. CHIPs are known to contain very small amounts of impurities, which makes them attractive for the methods according to the invention.

[0016] In the context of this invention, the term "solid metal-containing feed" specifically refers to the solid metal-containing feed fed into step iv. of the method, which comprises MHP products, CHIP products, or mixtures of two or more MHP products and two or more CHP products, or mixtures of one or more MHP products and one or more CHIP products. Preferably, the metal-containing feed comprises at least one Ni compound and / or at least one Co compound. Preferably, the Ni compound and the Co compound are included as Ni(II) compounds and as Co(II) compounds, respectively. However, the included Ni compound and the Co compound may also be in higher oxidation states such as 3+ or 4+, or the metal-containing feed may comprise a mixture of Ni and / or Co compounds in 2+ oxidation states and in 3+ and / or 4+ oxidation states.

[0017] In the context of this invention, the term "continuous process" is considered to be a process in which the resulting solution has a substantially constant composition. Specifically, a continuous process is a process in which the resulting solution has a constant composition within a range considered normal process variation. More specifically, the resulting solution has a composition in which the concentration of each component is within + / - 20% or less, preferably + / - 10% or less, more preferably + / - 5% or less, and even more preferably + / - 3% or less of its average concentration. In a preferred embodiment, the invention provides a continuous process operating under steady-state conditions.

[0018] In the context of this invention, the term "aqueous medium" is used for aqueous solutions. Aqueous media are advantageous for handling reactor contents, such as mixing or pumping. Aqueous media may already contain some other components that participate in the reaction, or those components may be added later. The aqueous medium may particularly contain inorganic acids.

[0019] Preferably, inorganic acids such as sulfuric acid or hydrochloric acid are fed intermittently or gradually into the process according to the invention. The solid metal-containing feed can also be fed intermittently or gradually into the process. However, the solid metal-containing feed is preferably fed only in the initial stage of the process.

[0020] The sulfiding agent used in the sulfidation reaction of step iv. should obviously be readily reactive with Co and / or Ni oxide. Therefore, a suitable sulfiding agent should preferably be at least partially soluble in an aqueous medium. Preferably, the sulfiding agent, such as H₂S or NaHS, is fed into the process according to the invention at a substantially constant concentration and flow rate. Preferably, the feed rate of the sulfiding agent into the process is controlled within a range of + / -20% or less, preferably + / -10% or less, more preferably + / -5% or less, and even more preferably + / -3% or less.

[0021] In a first aspect, the present invention provides a method for producing a metal sulfide comprising nickel and / or cobalt, the method comprising the steps of:

[0022] i. To form an aqueous metal sulfate solution by reacting sulfuric acid with a raw material feed containing nickel and / or cobalt in water;

[0023] ii. Crystallizing the metal sulfate from the aqueous metal sulfate solution to form crystalline metal sulfate in a mother liquor containing uncrystallized metal sulfate;

[0024] iii. Separating the crystallized metal sulfate from the mother liquor;

[0025] iv. Reacting at least a portion of the amorphous metal sulfate with a sulfiding agent (preferably hydrogen sulfide) in an acidic aqueous medium to obtain a slurry consisting of a solid phase containing a metal sulfide precipitate and an aqueous phase containing one or more impurities and sulfuric acid; and

[0026] v. Separate the solid phase and the aqueous phase to obtain an aqueous phase and a solid phase containing metal sulfides.

[0027] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the aqueous medium in step iv. further comprises a solid metal-containing feed containing a nickel compound and / or a cobalt compound. Preferably, the solid metal-containing feed is provided as a solid or as a slurry (i.e., a solid in the aqueous medium). Preferably, the solid metal-containing feed consists of MHP material and / or CHIP material. In one embodiment, the raw material feed consumed in step i. may have the same composition as the solid metal-containing feed. In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, the method further comprising adding a basic salt of Li, Na, K, Ca, Mg, Al, Fe, B, Mn, W and / or U to the aqueous medium in step iv. Suitable basic salts are, but are not limited to, MHP, CHIP, Mn carbonate, Mg oxide, waste battery materials, etc.

[0028] The sulfidation reaction in step iv. produces an inorganic acid that can be advantageously used to simultaneously leach impurities from a solid metal-containing feed. For example, Na or K impurities can be leached with sulfuric acid to produce water-soluble Na or K sulfates, respectively. This inorganic acid can also be added as is to stimulate the leaching of impurities, or it can be produced in situ by the reaction of NiSO4, NiCl2, CoSO4, or CoCl2 with a sulfiding agent such as hydrogen sulfide in an aqueous reaction medium according to one or more of the following reactions:

[0029]

[0030] Similarly, phosphates, nitrates, etc., of Ni and / or Co can be used to generate inorganic acids in situ. When NiSO4 or NiCl2 is contacted with H2S, sulfide metals such as NiS and / or CoS precipitate, and inorganic acids, namely sulfuric acid or hydrochloric acid, are generated in situ, respectively. Advantageously, according to such an embodiment, the total amount of Co and / or Ni in the aqueous medium increases, which allows for improved recovery efficiency. The process is robust enough to handle Co and / or Ni-containing solutions from impure waste streams. In a particularly preferred embodiment, inorganic acids are generated in situ by introducing effluents containing NiSO4 or CoSO4 obtained from a NiSO4 crystallization unit, a CoSO4 crystallization unit, or a mixed sulfate crystallization unit, respectively.

[0031] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the metal sulfide precipitate obtained in step iv. is subsequently leached with acid and / or with an oxidizing agent to regenerate hydrogen sulfide, and wherein the regenerated hydrogen sulfide is used in step iv.

[0032] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the uncrystallized metal sulfate reacts with hydrogen sulfide in step iv. at a temperature between 25°C and 80°C, preferably between 40°C and 80°C, and more preferably at about 60°C.

[0033] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the uncrystallized metal sulfate reacts with hydrogen sulfide at atmospheric pressure in step iv.

[0034] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein at least a portion of the amorphous metal sulfate reacts with hydrogen sulfide in step iv. in an acidic aqueous medium at a pH between 1.5 and 10, preferably between 1.5 and 6, and more preferably between about 3 and 6. Preferably, the acidic aqueous medium comprises sulfuric acid.

[0035] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein, prior to step ii., the amount of impurities in the aqueous metal sulfate solution is reduced by precipitation, ion exchange, and / or extraction of impurities from the solution. Preferably, at least a portion of the mother liquor obtained in step iii. is alkalized to form an alkaline metal salt. Preferably, the alkaline metal salt is used in one or more of the above-described precipitation, ion exchange, and extraction steps, such as for preparing an extractant preloaded with nickel and / or cobalt.

[0036] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein step iv. comprises reacting the solid metal-containing feedstock with a sulfiding agent in an aqueous medium at a pH between 1.5 and 10, thereby obtaining a slurry comprising a solid phase rich in Ni and / or Co and an aqueous phase comprising one or more water-soluble salts of Li, Mn, Mg, Al, Fe, Ca, B, Na and / or U. The pH of the aqueous medium can be controlled by adding an inorganic acid such as sulfuric acid or hydrochloric acid. Preferably, the invention provides a method wherein the solid metal-containing feedstock is first reacted with a sulfiding agent in step iv. at a pH between 3.0 and 10, and wherein the pH of the aqueous medium is subsequently reduced to below 3.0. First sulfidation at pH up to 10 is advantageous because sulfidation proceeds kinetically faster at higher pH levels, preferably between 6.5 and 8.0. Furthermore, at higher pH levels, impurities such as Na, Mg, and Ca may have already been removed from the feedstock. It has been found that lowering the pH to below 3.0, preferably below 2.5, during the second sulfidation step is beneficial for dissolving all impurities such as Fe, Al, Si, and U. More preferably, the pH of the aqueous medium is lowered to a value between 1.5 and 2.5. It is also possible to further lower the pH to below 1.5. Preferably, the sulfidation reaction in step iv. is carried out in a closed reactor to avoid the release of harmful gases. Preferably, the reactor exhaust gas is recirculated back into the reactor feed.

[0037] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the volume ratio φ of inorganic acids in the aqueous medium with a pH between 3 and 10 to inorganic acids in the aqueous medium with a pH below 3.0 is... AC It is between 0.0 and 0.95. Preferably, the ratio φ AC The ratio φ is between 0.10 and 0.95, and more preferably, the ratio φ is... AC It is approximately 0.80, 0.85, 0.90 or 0.95, or any value in between.

[0038] Therefore, it is also desirable to provide a method for selectively leaching impurities such as Li, Mg, and Mn from feed materials containing Ni and / or Co. Other impurities typically contained in such solid metal feeds include, but are not limited to, Al, Fe, Ca, B, Na, and U. Other impurities such as, but not limited to, Zn and Cu do not form water-soluble salts under the conditions of this method and therefore tend to remain in the solid phase. Such impurities can be separated from the Ni and / or Co in refining processes according to the prior art. Furthermore, organic carbon present in the metal feed can be washed out as a water-soluble compound and collected in the aqueous phase.

[0039] Typically, refining process flow diagrams for Ni and / or Co MHP and / or CHIP refining rely on the extraction of impurities such as Mn and Mg from solution. The method of the present invention provides an alternative means of removing Mg and Mn from Ni.

[0040] Other elements removed by forming water-soluble salts include Al, Fe, U, Na, B, Ca, and U. Many other impurities that may be present in the feed material, such as F, W, Si, P, C, K, Fe, Cl, and SO4, will be collected in the aqueous phase. Other impurities such as Cu, Zn, Pb, and Cd will be reported as solid residues. The generation of solid residues containing Mn-depleted Co sulfides and / or Ni offers several advantages for hydrometallurgical refining processes. It makes the process more intensive because Mn does not dilute the Ni- and / or Co-containing solution and avoids the need for Mn separation, for example, by solvent extraction.

[0041] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein the solid phase obtained in step ii., comprising Ni(II) sulfide and / or Co(II) sulfide, is leached with an acid and / or an oxidizing agent such as, but not limited to, O2 or Cl2. This yields a high-purity Ni salt solution and / or Co salt solution, while the sulfiding agent can be regenerated and recycled to step iv. of the method of the invention. Acid leaching of NiS and CoS results in the formation of Ni salt and Co salt, respectively, and in the formation of H2S. For example, the reaction of NiS with sulfuric acid results in the formation of NiSO4 and H2S, the latter of which can be advantageously recycled as a sulfiding agent in step iv. Similarly, the reaction of NiS with oxygen and HCl or with chlorine results in the formation of NiCl2 and S. S can be advantageously reduced to provide a sulfiding agent such as H2S, which can be recycled as a sulfiding agent in step iv.

[0042] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in the aqueous medium is first reacted with the vulcanizing agent in step iv. at a pH between 3.0 and 4.5. It has been found that lower pH favors the leaching of impurities from the solid metal-containing feed and rapid process kinetics. However, vulcanization at excessively low pH does not have sufficient selectivity. The inventors have discovered that optimal process conditions are obtained when the first vulcanization reaction is carried out at a pH of about 3.0 to 4.5. Preferably, the first vulcanization step is carried out for a processing time of 2 to 16 hours, more preferably 4 to 12 hours, and more preferably 4 to 10 hours.

[0043] In a preferred embodiment, the present invention provides a method according to a first aspect thereof, wherein after reacting the metal-containing feed at a pH between 3.0 and 10, the pH of the aqueous medium is lowered to a pH between 1.5 and 3.0. It has been found that lowering the pH favors faster process kinetics. It has also been found that lowering the pH to below 1.5 further improves the removal of impurities, however, it does not adequately compensate for the cost of inorganic acid consumption in the method. The inventors have found that optimal process conditions are obtained when the second sulfidation reaction is carried out at a pH of about 2.0 to 3.0, most preferably at a pH of 2.1, 2.2, 2.3, 2.4, or 2.5 or any value therebetween. Preferably, the second sulfidation step is carried out for a processing time of 0.5 hours to 8 hours, more preferably 1 hour to 4 hours, more preferably 1 hour, 2 hours, 3 hours, or 4 hours or any period therebetween.

[0044] A multi-step approach is advantageous, in which the majority of the process is carried out at a pH between 3.2 and 6.0, or even between 3.5 and 6.0, while in a second or any subsequent additional step, the pH is lowered to between 1.5 and 3. Higher pH values ​​favor sulfide formation kinetics. Therefore, it is advantageous for the majority of the process to be carried out at relatively high pH values, as sulfide formation is the rate-limiting step. Lower pH values ​​are chosen in the second or any subsequent additional step to maximize the dissolution of Mn and other impurities. Optionally, solid-liquid separation can be performed after each such additional step. The majority of the conversion to sulfides typically occurs in the first reaction step and is then completed by the second or any subsequent additional step. Since sulfides do not form at pH values ​​below 1, the process must be completed at a pH between 1 and 5. Operating at pH values ​​above the upper limit will result in insufficient dissolution of Mn.

[0045] After the process is complete, the pH can be further lowered to below 1.5 to maximize impurity removal. In fact, although the formed metal sulfides will not dissolve further in the absence of an oxidizing agent, some impurities can still be removed from the residue.

[0046] The solid residue obtained in step v., which separates the solids from the solution, can be further processed in various ways, wherein the main component of the Co and / or Ni contained in the solid residue is Co and / or Ni sulfide. Hydrometallurgical treatment of the solid residue is a preferred option.

[0047] Therefore, another embodiment describes a method in which the solid residue is used as a starting material in a subsequent hydrometallurgical refining process. The hydrometallurgical refining process includes the following steps:

[0048] - Extract the solid residue containing Co sulfide and / or Ni with an inorganic acid, preferably H2SO4, to obtain a solution containing Ni and / or Co;

[0049] - Separate the solution from the solid while retaining the insoluble solid; and,

[0050] - Crystallize Ni and / or Co from a solution containing Ni and / or Co, preferably as Ni and / or Co sulfate crystals.

[0051] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feedstock reacts with the sulfiding agent in step iv. at a temperature between 20°C and 80°C, preferably between 25°C and 80°C. Preferably, the feedstock reacts with the sulfiding agent at a substantially constant temperature. Since the reaction is moderately exothermic, only heating is required in the initial stage of the method. In a preferred embodiment, the temperature is controlled below 80°C, preferably between 40°C and 80°C, and more preferably around 60°C. Ensuring that the reaction temperature is not too high enhances the solubility of H2S in the aqueous medium and thus favors the sulfidation reaction kinetics.

[0052] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed reacts with the sulfiding agent in step iv. at atmospheric pressure, i.e., at 1 bar, or at a low pressure of less than 0.3 bar, preferably less than 0.2 bar, and more preferably less than 0.1 bar. Operating under low-pressure conditions ensures that the H2S used in the method does not leak into the environment. Preferably, the method is carried out in an atmosphere free of oxygen or air. In a preferred embodiment, the gaseous atmosphere above the aqueous medium is purged with an inert gas such as N2. Performing the method in the absence of oxidants such as oxygen and air avoids undesirable oxidation of nickel sulfide and / or cobalt.

[0053] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein hydrogen sulfide in step iv. is replaced with NaHS, KHS, or LiHS. H2S and NaHS are preferred sources of sulfides. Most preferably, the sulfiding agent comprises H2S. H2S can be introduced into the aqueous medium as is, or it can be generated in situ by adding elemental sulfur under reducing conditions, more specifically in the presence of H2. In the invention, the sulfiding agent acts not only as a precipitant to form metal sulfides, but also advantageously as a reducing agent for metals in higher valence states such as 3+ or 4+ oxidation states. The amount of sulfiding agent added is preferably sufficient to saturate the slurry in H2S. Saturation can be readily verified by monitoring the absorption rate of H2S by the reaction mixture. Saturation provides optimal kinetics. Alternatively or otherwise, NaHS can be introduced as a sulfiding agent. Ammonium sulfide can also be used.

[0054] A suitable sulfiding agent should preferably be at least partially soluble in an aqueous medium. For example, Li₂S reacts with a slurry to form a soluble Li salt and a soluble sulfide. On the other hand, sulfides that are insoluble under the stated conditions (e.g., CuS) are not considered a suitable source of the sulfides (and corresponding sulfiding agents) according to the invention.

[0055] The inorganic acid is preferably selected from H₂SO₄, HCl, H₃PO₄, and HNO₃, or mixtures thereof. In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein the inorganic acid is sulfuric acid. Alternatively, the inorganic acid may be hydrochloric acid.

[0056] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the method is a continuous process. Specifically, the method is carried out under continuous flow conditions.

[0057] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises an amount of Ni and / or Co in the amount of 5% to 75% by weight, preferably 10% to 65% by weight, relative to the total weight of the solid metal-containing feed. Preferably, the solid metal-containing feed comprises an amount of Ni and / or Co in the amount of 20% to 60% by weight, such as 30% to 50% by weight.

[0058] In an alternative embodiment, the invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises lithium-free battery materials, such as non-lithiated production waste obtained from battery production or partially recycled battery materials from which lithium contents have been removed. In addition to oxides of Co and / or Ni, typical battery waste-based feeds may also contain anode materials, such as carbon, electrode foil, and electrolyte. Preferably, at least a major portion (more preferably at least 80% by weight, most preferably at least 90% by weight) of the Co and / or Ni contained in the feed is in the form of their respective metal oxides. The remainder may comprise Co and / or Ni in metallic form.

[0059] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises Ni in an amount of 10% to 70% by weight, preferably 20% to 60% by weight, and more preferably 30% to 55% by weight, relative to the total weight of the solid metal-containing feed. Preferably, the solid metal-containing feed further comprises Co in an amount of 0.5% to 15% by weight, preferably 1% to 10% by weight, and more preferably 1% to 5% by weight, relative to the total weight of the solid metal-containing feed.

[0060] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the Ni compound and / or the Co compound present in the solid metal-containing feed in step iv. are in a 2+ oxidation state. However, the method of the present invention also allows the Ni compound and the Co compound to also contain compounds in higher oxidation states such as 3+ or 4+. Preferably, the compounds are water-insoluble compounds. Advantageously, it has been found that, under the reaction conditions of the present invention, Ni and / or Co metal compounds having higher oxidation states are effectively reduced by a sulfiding agent, preferably H2S, during the first step of the method of the present invention.

[0061] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the Ni compound and / or at least one Co compound in the solid metal-containing feed in step iv. comprises carbonates, basic carbonates, sulfates, sulfites, phosphates, hydroxides, and / or oxides. Preferably, the Ni compound and / or at least one Co compound in the solid metal-containing feed consists of basic carbonates, hydroxides, and / or oxides, most preferably consisting of basic carbonates and / or hydroxides.

[0062] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises an amount of Mn in which 1% to 15% by weight, preferably 3% to 10% by weight, relative to the total weight of the solid metal-containing feed.

[0063] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises an amount of Mg in which 0.1% to 10% by weight, preferably 1% to 7% by weight, relative to the total weight of the solid metal-containing feed.

[0064] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. comprises an amount of Al in the amount of 0.01 wt% to 2.00 wt% relative to the total weight of the solid metal-containing feed, preferably 0.02 wt% to 1.50 wt%.

[0065] In a preferred embodiment, the present invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. further comprises an amount of Cu of 0.01 wt% to 0.20 wt% relative to the total weight of the solid metal-containing feed and / or an amount of Zn of 0.2 wt% to 1.0 wt% relative to the total weight of the solid metal-containing feed.

[0066] In a preferred embodiment, the invention provides a method according to a first aspect of the invention, wherein the solid metal-containing feed in step iv. is a powder, said powder preferably having a D50 of less than 100 µm as determined according to ASTM B822-97 Standard Test Method for Particle Size Distribution of Metal Powders and Related Compounds by Light Scattering, American Society for Testing and Materials, West Conshohocken, PA (1997). ASTM B822-97 is an ASTM standard test method for determining the size of particulate metals and compounds by laser diffraction. Preferably, the D50 of said powder is less than 50 µm, more preferably less than 30 µm, and greater than 0.1 µm, more preferably greater than 1 µm. When present in powder form, metal oxides are more readily reacted. Therefore, in industrial settings, an average particle size of less than 100 µm, less than 50 µm, or even less than 30 µm is preferred. It is not required that this powder be a dry powder; it can also be derived from wet processes, such as filter cake. This is particularly advantageous because the formation of Ni and Co sulfides has been found to be a rate-controlling step.

[0067] In another embodiment, the method according to the first aspect of the invention is carried out in a continuous operation. In this setup, feed and acid are continuously added to the reactor while the slurry is extracted from the reactor. Addition and extraction can also be carried out in batches, for example, repeated every 30 minutes. Continuous operation has several advantages. First, continuous operation enhances the usability of the reactor equipment. Second, the quality of solid sulfided Co and / or Ni is more consistent because they are formed in a steady-state manner. This is beneficial for further refining. In an alternative embodiment, the method according to the first aspect of the invention is carried out in a batch operation. In this operation, a first stage of the sulfidation process is carried out in a first reactor at a pH between 3.0 and 10.0, and a second stage of the process is carried out in a second, separate reactor at a pH below 3.0.

Claims

1. A process for producing a metal sulfide comprising nickel and / or cobalt, the process comprising the steps of: i. forming an aqueous metal sulfate solution by reacting sulfuric acid with a raw material feed comprising nickel and / or cobalt in water; ii. crystallizing the metal sulfate from the aqueous metal sulfate solution to form a crystallized metal sulfate in a mother liquor, the mother liquor comprising uncrystallized metal sulfate; iii. separating the crystallized metal sulfate from the mother liquor; iv. reacting at least a portion of the uncrystallized metal sulfate with a sulfidizing agent in an acidic aqueous medium, thereby obtaining a slurry consisting of a solid phase comprising a metal sulfide precipitate and an aqueous phase comprising one or more impurities and sulfuric acid; and v. separating the solid phase and the aqueous phase, thereby obtaining an aqueous phase and a solid phase comprising a metal sulfide, wherein the aqueous medium in step iv. further comprises a solid metal-containing feed comprising a nickel compound and / or a cobalt compound.

2. The process according to claim 1, further comprising the step of adding an alkali salt of Li, Na, K, Ca, Mg, Al, Fe, B, Mn, W and / or U to the aqueous medium in step iv.

3. The process according to claim 1 or 2, wherein the metal sulfide precipitate obtained in step iv. is subsequently leached with acid and / or with an oxidizing agent to regenerate hydrogen sulfide, and wherein the regenerated hydrogen sulfide is used in step iv.

4. The process according to any one of claims 1 to 3, wherein the uncrystallized metal sulfate is reacted with a sulfidizing agent in step iv. at a temperature between 40 °C and 80 °C.

5. The process according to any one of claims 1 to 4, wherein the uncrystallized metal sulfate is reacted with a sulfidizing agent in step iv. at atmospheric pressure.

6. The process according to any one of claims 1 to 5, wherein at least a portion of the uncrystallized metal sulfate is reacted with a sulfidizing agent in step iv. in an aqueous medium at a pH between 1.5 and 10.

7. The process according to claim 6, wherein sulfuric acid is added to the aqueous medium in step iv.

8. The process according to any one of claims 1 to 7, wherein prior to step ii. the amount of impurities in the aqueous metal sulfate solution is reduced by precipitating, ion exchanging and / or extracting impurities from the aqueous metal sulfate solution.

9. The process according to any one of claims 1 to 8, wherein the solid metal-containing feed in step iv. comprises Ni and / or Co in an amount of 5 to 75 wt% relative to the total weight of the solid metal-containing feed.

10. The process according to any one of claims 1 to 9, wherein the solid metal-containing feed in step iv. comprises Ni and / or Co in the form of a carbonate, an alkali carbonate, a sulfate, a phosphate, a hydroxide and / or an oxide. ​ ​ ​ ​ ​ ​ 11. The process according to any one of claims 1 to 10, wherein the solid metalliferous feed material in step iv. comprises Mn in an amount of 1 to 15 wt.-% relative to the total weight of the solid metalliferous feed material.

12. The process according to any one of claims 1 to 11, wherein the solid metalliferous feed material in step iv. comprises Mg in an amount of 0.1 to 10 wt.-% relative to the total weight of the solid metalliferous feed material.

13. The process according to any one of claims 1 to 12, wherein the solid metalliferous feed material in step iv. comprises Al in an amount of 0.01 to 2.00 wt.-% relative to the total weight of the solid metalliferous feed material.

14. The process according to any one of claims 1 to 13, wherein the solid metalliferous feed material in step iv. further comprises Cu in an amount of 0.01 to 0.20 wt.-% relative to the total weight of the solid metalliferous feed material and / or Zn in an amount of 0.2 to 1.0 wt.-% relative to the total weight of the solid metalliferous feed material.

15. The process according to any one of claims 1 to 14, wherein the solid metalliferous feed material in step iv. is a powder having an average particle size D50 of between 0.1 pm and 100 pm as determined according to ASTM B822-97.

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