Process for preparing high purity nickel sulfate solution

Abstract

The present invention provides a process for preparing a high-purity nickel sulfate solution, comprising: i. reacting sulfuric acid with a raw material feed comprising nickel, manganese, cobalt, and magnesium in an aqueous medium to form a mixed metal sulfate aqueous solution; ii. extracting manganese from the mixed metal sulfate aqueous solution, thereby obtaining a first aqueous raffinate comprising nickel, cobalt, and magnesium, and a manganese-enriched organic phase; iii. extracting cobalt from the first aqueous raffinate, thereby obtaining a second aqueous raffinate comprising nickel and magnesium, and a cobalt-enriched organic phase; and iv. extracting magnesium from the second aqueous raffinate solution, thereby obtaining a high-purity nickel sulfate solution and a magnesium-enriched organic phase.

Description

[Technical Field]

[0001] The present invention relates to a novel method for producing a high purity aqueous nickel sulfate solution having sufficient purity for use in the electroless plating of nickel metal layers or in the production of battery materials. [Background technology]

[0002] The development of lithium-ion batteries, particularly the use of nickel-manganese-cobalt and nickel-cobalt-aluminum cathode materials, has increased the demand for high-purity nickel sulfate, either as a solid or in solution. Indeed, impurities in the cathode material have a significant impact on battery performance. Therefore, much effort has been devoted to producing high-purity nickel sulfate in an industrially viable process.

[0003] In this regard, U.S. Patent Application Publication No. 2014 / 322109 provides a method for obtaining high-purity nickel sulfate with low levels of impurities, particularly low levels of magnesium and chloride, by introducing a selective nickel sulfide precipitation step and redissolving nickel sulfide in a nickel sulfate solution. This solution is further purified by solvent extraction to remove cobalt and magnesium impurities, and the concentration of the acidic organic extractant and the pH or acid concentration during processing are adjusted. The described processing strategy is cumbersome for concentrated nickel sulfate solutions because it requires intermediate precipitation and redissolution of the nickel bulk, followed by solvent extraction to remove the impurities cobalt and magnesium. In particular, the nickel sulfide step is dangerous due to the risk of hydrogen sulfide generation. Furthermore, solvent extraction is used to remove only cobalt and magnesium, while crude nickel feedstock typically contains more impurities.

[0004] Chinese Patent No. 107162067 relates to the field of solid waste recycling. In particular, the patent discloses a method for recycling high-purity nickel sulfate from nickel-containing waste batteries. The method includes the steps of decomposing nickel-containing waste batteries into battery powder, dissolving the battery powder with acid to obtain a metal-containing solution, adding an alkali metal sulfate, removing iron through an oxidation precipitation process, further removing impurities through a solvent extraction process to obtain a magnesium-containing nickel solution, passing the magnesium-containing nickel solution through a chelating resin exchange column to selectively adsorb nickel ions and then discharging a magnesium-rich solution for processing, desorbing the nickel ions to obtain a nickel sulfate solution, evaporating the nickel sulfate solution, cooling, crystallizing, filtering, and finally drying to obtain a purified nickel sulfate product. This lengthy and complex process ensures that the recycled nickel sulfate is a high-purity product with a nickel content of up to 99.5% or more and an impurity, i.e., magnesium content, of less than 0.005%. However, three different solvent extraction units are proposed to remove copper, manganese, and cobalt in separate steps. Apart from the high investment costs, no attempt is made to further remove other impurities such as calcium and magnesium. Finally, nickel is recovered by adsorption onto a resin, requiring a fourth separation step and the consumption of a neutralizing agent equal to the amount of metal ions adsorbed. Overall, the described process is considered neither simple nor efficient.

[0005] EP 1252345 B1 describes a process for extracting cobalt from a cobalt-nickel solution with a nickel-loaded solvent to obtain a purified nickel sulfate stream. However, this patent does not identify how to remove impurities such as calcium and magnesium to very low levels to produce a purified nickel sulfate solution for electroless nickel or battery applications. This patent appears to be more geared toward developing a solvent extraction process that can avoid the formation of insoluble ammonium / nickel sulfate double salts.

[0006] EP 2784166 describes a process for producing a pure nickel sulfate solution through multiple process steps, including sulfiding, redissolving, purification by precipitation, and solvent extraction. In particular, the sulfiding and redissolving steps are expensive operations that use sulfiding agents and produce nickel sulfide intermediates; both products are toxic, and contact and reaction with mineral acids can result in the generation of highly toxic gaseous hydrogen sulfide. Finally, the purified nickel sulfate solution still contains 50 mg / L of magnesium impurity, which is too much for battery-grade nickel sulfate, demonstrating the lack of selectivity of the proposed process.

[0007] European Patent No. 3733884 describes a solvent extraction method capable of selectively separating magnesium from an acidic aqueous solution of sulfuric acid. This solvent extraction method involves contacting an acidic aqueous solution of sulfuric acid containing nickel, cobalt, and magnesium with an organic solvent and selectively extracting magnesium into the organic solvent under very specific extraction conditions: either using a concentrated solvent, i.e., a solvent containing 40-60% alkylphosphonic acid as the extractant, at a fairly low pH of 1.5-2, or using a lower extractant concentration, i.e., a solvent containing 20-50% alkylphosphonic acid, at a higher pH of 2.0-2.5. This process is intended only to remove magnesium from the nickel solution, not to separate cobalt. Remarkably, at most 46% of magnesium was removed from a nickel sulfate solution that already contained approximately 9% nickel under the same extraction conditions. Under these conditions, only a Mg / Ni separation factor of 8-23 was obtained. Decreasing the extractant concentration in the spent solvent below 40% by volume resulted in higher Mg / Ni separation factors of up to 35, but the magnesium removal was much lower, i.e., below 28%.

[0008] EP 3222735 discloses a method for separating cobalt and magnesium from a nickel-containing feed solution by liquid-liquid extraction, in which the organic solvent used contains an alkylphosphinic acid as an extractant. Both cobalt and magnesium are extracted along with some nickel. First, nickel is washed out of the loaded solvent using an acidic solution. The resulting nickel solution may contain some cobalt, so the nickel solution is returned to the feed solution. Then, magnesium is washed out of the solvent using an acidic solution. The resulting magnesium solution may contain some cobalt and is processed elsewhere. Cobalt is stripped from the solvent using a dilute aqueous acid to form a cobalt-stripped solution. Aside from cobalt and magnesium, this patent does not address the removal of other metal contaminants in the nickel sulfate solution, such as calcium, zinc, cadmium, copper, manganese, and iron. Considering that acidic protons are released during extraction with an acidic extractant, the patent does not detail any technique for reaching the desired pH for extracting cobalt and magnesium from nickel sulfate solutions.

[0009] When EHEHPA, also known as PC88A, is used as the extractant, the extraction behavior for magnesium or calcium is similar to that for nickel. Japanese Patent Publication No. 10-310437 discloses an example of separating nickel and cobalt by solvent extraction using PC88A as the extractant, extracting cobalt along with other impurities such as calcium, copper, zinc, iron, and magnesium. When a solution containing high concentrations of nickel is subjected to solvent extraction, the extraction efficiency of magnesium or calcium decreases. Difficulties in removing magnesium from nickel sulfate solutions are noted. The final impurity product concentrations in the purified nickel sulfate solution, when containing 90-117 g / L of nickel, were still 3-26 mg / L of cobalt, 2-7 mg / L of calcium, and 10-27 mg / L of magnesium. The present invention solves the problem of insufficient calcium extraction by selecting operating conditions that favor calcium extraction while simultaneously reducing magnesium extraction. This is compensated for by carrying out an additional separate solvent extraction for magnesium using a more favorable extractant and more favorable operating conditions.

[0010] JP 2021-031729(A2) describes the treatment of a crude nickel sulfate solution with a single solvent extraction process that attempts to remove all cobalt, magnesium, and calcium from the nickel sulfate solution at once. The ratio of the amount of nickel loaded to the solvent to the concentration of cobalt in the nickel sulfate solution should be varied depending on the desired impurity removal. However, the examples show that it is not possible to remove all contaminants, as the purified nickel sulfate solution still contains 1-60 mg / L of cobalt, 1-20 mg / L of magnesium, and 1-15 mg / L of calcium. Furthermore, magnesium removal appears to be minimal because the magnesium input concentration in the crude nickel sulfate solution is very low, only 19-31 mg / L compared to the very high cobalt concentration of 8-12 g / L. This principle of co-extracting trace amounts of magnesium with large amounts of cobalt, even if incomplete, is evidence of the inevitable use of large amounts of nickel relative to the solvent. It only appears that magnesium may be better removed when the amount of nickel loaded onto the solvent is increased relative to the concentration of cobalt in the crude nickel sulfate solution. A similar patent, JP 2021-031730(A), suggests that the amount of magnesium reported in the cobalt eluate from coextraction with the solvent can be affected by the selected amount of nickel added to the solvent relative to the concentration of cobalt present in the crude nickel sulfate solution. The same examples as in JP 2021-031729(A2). The purified nickel sulfate solution may still contain high impurities, ranging from 1 to 60 mg / L of cobalt, 1 to 20 mg / L of magnesium, and 1 to 15 mg / L of calcium. The reported amount of magnesium coextracted into the cobalt eluate may vary significantly.

[0011] U.S. Patent No. 6,149,885(A) describes a process in which impurities such as cobalt, calcium, copper, and zinc are removed from a crude nickel sulfate solution by solvent extraction. A method is disclosed for loading nickel into a solvent that can later be used to remove impurities from the crude nickel sulfate solution. However, only a small amount of magnesium is removed. In one example, 34 mg / L of magnesium remains in the purified nickel sulfate solution, which is typically considered too impure for battery-grade nickel sulfate quality. In another example, a whopping 354 ppm of magnesium per 100% nickel remains in the purified nickel sulfate solution. Removal of other metals, such as cadmium and manganese, from the crude nickel sulfate solution is not even considered.

[0012] Chinese Patent No. 111334664 describes a ternary lithium battery cathode material containing nickel, cobalt, manganese, and lithium, and the recovery of valuable metals using a sulfation oxygen-free roasting-flooding-acid leaching-extraction process. The extraction process includes the following steps: Manganese extraction: extraction section after extraction stage 10 to obtain a loaded organic phase containing a P204 concentration of 20%, a degree of saponification of 50%, Ni, Co, Mn, and Mg extraction raffinate.

[0013] Cobalt extraction: Using a P507 concentration of 20%, a degree of saponification of 60%, and an extraction segment level of 8, a Ni- and Mg-enriched raffinate with a Co-enriched organic phase load is obtained.

[0014] Extraction of magnesium: At a P507 concentration of 25% and a degree of saponification of 40%, extraction segment 5 yields a loaded organic phase enriched in Mg and a raffinate enriched in Ni.

[0015] Nickel extraction: Use P507 to strip nickel, specific conditions: 20% P507 concentration, 70% saponification degree.

[0016] Chinese Patent No. 113444885 describes a method for preferentially extracting metallic lithium from waste ternary lithium-ion batteries and simultaneously obtaining battery-grade metal salts, and the method for extracting manganese, cobalt, and nickel includes the following steps: - Extraction of high purity manganese salt: The raffinate collected after leaching out impurities is mixed with organic extractant P204, and countercurrent extraction method is used for extraction, and the raffinate is collected. The organic extractant P204 is mixed with 260# solvent oil in a ratio of 25%. Extraction of cobalt salts: The raffinate is mixed with organic extractant P507 and extracted using a countercurrent extraction method. The organic extractant is mixed with 260# solvent oil, in which P507 accounts for 25%. - Nickel salt extraction: The raffinate is mixed with organic extractant Cyanex 272 mixed with 260# solvent oil, and a countercurrent extraction method is used for extraction. In the extraction process, all magnesium ions in the aqueous phase are extracted into the organic phase to obtain a high-purity nickel sulfate solution. The high-purity nickel sulfate solution is subjected to further processing to obtain battery-grade nickel sulfate.

[0017] WO 20 / 220559 describes a method for recovering valuable metals in waste nickel-cobalt-manganese ternary lithium batteries, which method comprises the following steps: (1) crushing and carbonizing waste nickel-cobalt-manganese ternary lithium batteries, and separating the powder and metal particles by air separation; (2) leaching the powder separated in step (1) with sulfuric acid to obtain a leachate; (3) Fe in the leaching solution used as the pre-extraction solution 2+ , Al 3+ , Ca 2+ , and Mg 2+ removing the (4) Using P204, the pre-extraction solution is extracted, impurities are removed, and stripping is performed to obtain a stripping solution containing manganese sulfate and Co. 2+ , Ni 2+ , and Li +and a raffinate solution containing manganese sulfate, which is obtained by removing copper from the stripping solution, followed by evaporation, concentration and crystallization; (5) Using the raffinate obtained in step (4), cobalt is extracted with P507. When cobalt is extracted with P507, the oil to water ratio is controlled to be 0.8 to 0.9:1, an alkaline solution is used for saponification, and the saponification rate is controlled to be 55% to 60%. A cobalt stripping solution and Ni 2+ and Li + evaporating, concentrating and crystallizing the raffinate, stripping solution containing cobalt sulfate; (6) The raffinate obtained in step (5) is extracted with C272 to remove impurities and to obtain Mg 2+ obtaining a C272 raffinate after removing (7) Nickel was extracted from C272 raffinate using P507 and stripped to give a stripped solution containing nickel sulfate and Li + and a raffinate solution containing nickel sulfate. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] US Patent Application Publication No. 2014 / 322109 [Patent Document 2] Chinese Patent No. 107162067 [Patent Document 3] European Patent No. 1252345(B1) [Patent Document 4] European Patent No. 2784166 [Patent Document 5] European Patent No. 3733884 [Patent Document 6] European Patent No. 3222735 [Patent Document 7] Japanese Patent Application Publication No. 10-310437 [Patent Document 8] Japanese Patent Application Publication No. 2021-031729 (A2) [Patent Document 9] U.S. Patent No. 6,149,885(A) [Patent Document 10] Chinese Patent No. 111334664 [Patent Document 11] Chinese Patent No. 113444885 [Patent Document 12] International Publication No. 20 / 220559 Summary of the Invention [Problem to be solved by the invention]

[0019] A general limitation of prior art processes is the need to feed the process with highly specialized nickel-containing material sources to reach the desired purity of nickel sulfate solution. Most such processes focus on the recovery of battery scrap materials. There is a need for a process that allows for the processing of raw materials of various quality grades and nickel contents into high-purity battery-grade nickel sulfate solution. Additionally, such a new process should also have high economy in terms of the number of process steps and high efficiency in terms of nickel recovery and recovery of other valuable materials, such as cobalt.

[0020] In conclusion, there is a need for a simple, efficient, and practical method for achieving high-purity nickel sulfate with low levels of cobalt, manganese, magnesium, and other impurities, resulting in nickel sulfate that can be used in applications requiring high purity, such as electroless plating of nickel metal layers, or as a precursor for battery cathode materials. It is an object of the present invention to provide a novel process for producing a high-purity nickel sulfate solution from an aqueous nickel solution containing cobalt, magnesium, and manganese, and optionally impurities such as iron, zinc, copper, cadmium, and calcium. It is a further object of the present invention to easily produce nickel sulfate with consistent quality. Finally, it is an object of the present invention to provide a process that allows for the production of a cobalt-enriched aqueous solution suitable for further processing from a crude nickel feedstock. [Means for solving the problem]

[0021] The present invention provides a solution to at least one of the above mentioned problems by providing a process for preparing a high purity nickel sulfate solution, as set forth in claim 1.

[0022] The present invention has the advantage that the elements cobalt, zinc, manganese, cadmium, aluminum, copper, calcium, and magnesium, if present, are all completely separated from the nickel.

[0023] The overall process according to the present invention is efficient in the sense that it avoids material losses thanks to the minimal co-extraction of the matrix element, nickel, thus providing a nickel solution of high purity, i.e., at least 99.8 atomic % nickel relative to the solution's metal content, while avoiding the formation of complex nickel-containing mixtures. Therefore, the process according to the present invention is environmentally friendly. The processing strategy ensures that the presence of undesirable ions in the final nickel sulfate solution originating from the reagents used during the nickel purification process, such as calcium from calcium bases, sodium from sodium bases, and chloride from hydrochloric acid, is avoided. In this way, the nickel sulfate solution obtained from the proposed process can be easily further processed by crystallization or spray drying to form nickel sulfate crystals or granules, respectively, which are easily transported. Advantageously, the present invention also allows for the production of a cobalt-enriched eluate and a manganese-enriched eluate, which can be further processed separately, for example, to produce high-purity cobalt salts as cobalt chloride and cobalt sulfate, and high-purity manganese salts as manganese chloride and manganese sulfate, respectively. The process of the present invention is simple, environmentally friendly, and provides high purity nickel sulfate.

[0024] Furthermore, the present invention provides a process by which raw material feeds such as battery scrap materials, mixed hydroxide precipitate (MHP) and cobalt hydroxide intermediate precipitate (CHIP), or mixtures thereof, can be converted from complex impure feeds to battery grade nickel sulfate solutions using as few as three solvent extraction steps and, where applicable, a precipitation step to remove iron, aluminum, etc., prior to the solvent extraction steps. The battery grade nickel sulfate solutions obtained by the present process can be used directly, i.e., without the need for further purification by ion exchange, extraction, or other methods, for the production of battery precursor materials. DETAILED DESCRIPTION OF THE INVENTION

[0025] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. As a further guide, term definitions are included to better understand the teachings of the present invention.

[0026] As used herein, the following terms have the following meanings: As used herein, "a," "an," and "the" refer to both the singular and the plural unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more compartments.

[0027] As used herein, "about" in reference to a measurable value, e.g., a parameter, amount, duration, etc., is meant to encompass a variation of the specified value by no more than ±20%, preferably no more than ±10%, more preferably no more than ±5%, even more preferably no more than ±1%, and even more preferably no more than ±0.1%, to the extent that such variations are appropriate for practicing the disclosed invention. However, it should be understood that the value to which the modifier "about" refers is itself specifically disclosed.

[0028] As used herein, the words "comprise," "comprising," and "comprises," as well as "comprised of," are synonymous with "include," "including," "includes," or "contain," "containing," or "contains," and are inclusive or open-ended terms specifying the presence of at least what follows, and do not exclude or preclude the presence of additional, unrecited components, features, elements, materials, or steps that are known in the art or disclosed herein.

[0029] The recitation of numerical ranges by endpoints includes not only the recited endpoints but also all numbers and fractions subsumed within that range. All percentages, unless otherwise defined or a different meaning is apparent to one of ordinary skill in the art from their use and the context in which they are used, shall be understood as weight percentages, abbreviated as "wt %," or volume percentages, abbreviated as "vol %," or atomic percentages, abbreviated as "atom %."

[0030] With respect to the organic phase, the following terms are used to identify components or the entire organic phase. i. In the context of the present invention, the term "organic phase" should be understood as synonymous with the term "solvent" or "solvent mixture" and refers to a liquid composition comprising one or more extractants, a diluent, and optionally one or more modifiers. ii. "Extractant" or extracting agent is an active component in the organic phase that extracts metal species into the organic phase by chemically binding with the metal species to form a metal-extractant complex that dissolves better in the organic phase than in the aqueous phase. iii. "Diluent" is an organic molecule, or usually a mixture of different organic molecules, added to the organic phase to dilute the extractant, allow dissolution of the metal complexes, improve the physical properties of the organic phase (especially the phase separation phenomenon), and reduce the cost of the extractant, given that diluents are usually cheaper than the extractant. The diluent is often a kerosene fraction and can be an aliphatic or aromatic hydrocarbon, naphthene, etc., or a mixture thereof. The diluent is preferably a kerosene-based petroleum fraction, such as Escaid, Elixore, Shellsol, Isopar, etc. iv. The organic phase may also contain a "modifier." Because crud formation or third phase formation is undesirable in solvent extraction, modifiers may be added to improve the solubility of metal complexes in the organic phase, to change the physical properties of the solvent to avoid these phenomena, or to prevent chemical decomposition of the extractant or diluent. However, modifiers may impair the selectivity of the organic phase because they may participate in the complex formation between the metal and the extractant.

[0031] The "selectivity" S of an extractant for one metal over another can be expressed as the ratio of the distribution coefficients D for both metals. S Mg / Ni =D Mg / D Ni

[0032] The "partition coefficient" of a metal is understood to be the ratio of the equilibrium concentration of this metal in the organic phase to the equilibrium concentration of the same metal in the aqueous phase, respectively. D M =[M] O / [M] A where M is a metal, such as nickel or magnesium, O represents the organic phase, and A represents the aqueous phase.

[0033] In the context of the present invention, the term "feedstock" refers to one or more feedstocks containing any one or combination of nickel, cobalt, manganese, or lithium. The metals may be present as such or as compounds of the aforementioned metals or as a mixture of compounds. In some embodiments, the feedstock may include any one or combination of raw materials and recycled materials. Examples of raw materials include, but are not limited to, mixed hydroxide precipitate (MHP), mixed sulfide precipitate (MSP), nickel sulfide concentrate, cobalt sulfide concentrate, nickel laterite, nickel matte, or ferronickel. Examples of recycled materials include, but are not limited to, spent cathode material and materials derived from recycled lithium-ion batteries or lithium-ion battery manufacturing scrap (collectively referred to herein as "black mass").

[0034] In the context of the present invention, the term "MHP" should be considered an abbreviation of the term "mixed hydroxide precipitate." Mixed hydroxide precipitate (MHP) is an intermediate product of nickel metallurgy resulting from the processing of laterite ore, which contains primarily nickel and small amounts of cobalt. MHP is a solid product typically prepared by extracting nickel and cobalt from laterite ore. Alternatively or additionally, MHP may be obtained from nickel- and / or cobalt-containing materials generated as waste products during the preparation of cathode materials or obtained from battery recycling processes.

[0035] In the context of the present invention, the term "CHIP" should be considered an abbreviation of the term "cobalt hydroxide intermediate precipitate." Cobalt hydroxide intermediates are primarily composed of cobalt and typically have a cobalt content of 25% to 40% by weight based on the total weight of the intermediate product. Typically, CHIP also contains a significant amount of nickel. CHIP is known to have very low amounts of impurities, making it attractive for the process according to the present invention.

[0036] The "feedstock" may refer to a solid feedstock containing an MHP product, a CHIP product, or a mixture of two or more MHP products, two or more CHIP products, or a mixture of one or more MHP products and one or more CHIP products. Preferably, the feedstock contains at least one nickel compound and at least one cobalt compound. Preferably, the nickel compound and the cobalt compound are present as nickel(II) compounds and cobalt(II) compounds, respectively. Furthermore, the nickel compound and the cobalt compound may be present in a higher oxidation state, such as 3+ or 4+, or the metal-containing feed may contain a mixture of nickel and / or cobalt compounds in the oxidation state 2+ and the oxidation states 3+ and / or 4+. Furthermore, the feedstock may contain an alloy of nickel(0) and cobalt(0), and / or the feedstock may contain one or more ores containing nickel and cobalt.

[0037] In the context of the present invention, the term "continuous process" is intended to be understood as a process in which the solution produced has a substantially constant effluent and composition. Specifically, a continuous process is one in which the solution produced has a constant composition within what would be considered normal process variations. More specifically, the solution produced has a composition in which the concentration of each component is within ±20% or less of its average concentration, preferably ±10% or less, more preferably ±5% or less, and even more preferably ±3% or less. In a preferred embodiment, the present invention provides a continuous process operating under steady-state conditions.

[0038] In the context of the present invention, the term "aqueous medium" is used for a water-based solution. The aqueous medium facilitates handling of the reactor contents, such as mixing or pumping. The aqueous medium may already contain some of the other components involved in the reaction, or these components may be added later. The aqueous medium may contain, in particular, a mineral acid.

[0039] In the context of the present invention, the term "cathode precursor material" refers to a mixed metal hydroxide, carbonate, oxyhydroxide, and / or oxide comprising nickel and at least one metal selected from cobalt, manganese, and aluminum. Preferably, the cathode precursor material comprises Ni in an amount of at least 30 mol %, or even at least 50 mol %, preferably 60 mol % to 95 mol %, based on the total content of nickel, cobalt, manganese, and aluminum in the cathode precursor material, and all values ​​therebetween. The cathode precursor material may further comprise one or more metals selected from Ba, Al, Ti, Zr, W, Fe, Cr, Mo, Nb, Mg, and V, more preferably Al, Ti, Zr, W, and Mg. In one preferred embodiment, the cathode precursor material comprises Ni, Co, and Al. In another preferred embodiment, the cathode precursor material comprises Ni, Co, and Mn.

[0040] In a first aspect, the present invention provides a process for preparing a high purity nickel sulfate solution, comprising: i. forming an aqueous mixed metal sulfate solution by reacting sulfuric acid with a raw material feed comprising nickel, manganese, cobalt, and magnesium in an aqueous medium; ii. extracting manganese from the mixed metal sulfate aqueous solution using a first organic phase comprising a first alkylphosphorus extractant (I) and a first diluent, thereby obtaining a first aqueous raffinate containing nickel, cobalt, and magnesium, and a manganese-enriched organic phase; iii. extracting cobalt from the first aqueous raffinate using a second organic phase comprising a second alkylphosphorus extractant (II) and a second diluent, thereby obtaining a second aqueous raffinate containing nickel and residual magnesium content and a cobalt-rich organic phase; iv. extracting magnesium from the aqueous raffinate solution using a third organic phase comprising a third alkylphosphorus extractant (III) and a third diluent, thereby obtaining a high-purity nickel sulfate solution and a magnesium-enriched organic phase.

[0041] In a preferred embodiment, the present invention provides a) the first alkylphosphorus extractant (I) comprises an alkylphosphoric acid and / or a nickel and / or cobalt salt of an alkylphosphoric acid; b) the second alkylphosphorus extractant (II) comprises an alkylphosphinic acid and / or a nickel salt of an alkylphosphinic acid; c) providing a process according to the first aspect of the present invention, wherein the third alkylphosphorus extractant (III) comprises an alkylphosphinic acid and / or a nickel salt of an alkylphosphinic acid.

[0042] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein the extraction in step ii. is carried out at a temperature of 20-45°C, preferably 20-40°C, more preferably 25-35°C, and most preferably about 20°C, 25°C, 30°C, 35°C, or 40°C, or any value therebetween. It has been found that lower temperatures provide better selectivity for Mn extraction and therefore better separation of Mn from Co. Preferably, the temperature is above 20°C, or even above 25°C, to facilitate operating temperature settings in high ambient temperature conditions.

[0043] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the extraction in step iii. is carried out at a temperature of 40-60°C, preferably at a temperature of about 50°C. It has been found that a sufficiently low temperature in step ii., combined with a higher temperature in step iii., contributes to the separation of manganese and cobalt from the aqueous stream obtained as an aqueous raffinate in step iii. Advantageously, the process configuration of the present invention allows a battery-grade high-purity nickel sulfate solution to be obtained in three solvent extraction steps, avoiding the need to extract Ni from the aqueous stream. Thus, the present invention also provides a process according to the first aspect of the present invention, wherein the high-purity nickel sulfate solution obtained in step iv. is not subjected to solvent extraction to extract nickel from the aqueous nickel sulfate solution.

[0044] The solvent extraction steps ii., iii., and iv. can be carried out in any suitable device, without particular limitation. Solvent extraction equipment generally comprises at least one device consisting of a mixer-settler, a column contactor, a centrifugal contactor, or any other type of contactor. Preferably, the extraction is carried out in a countercurrent configuration.

[0045] The first aqueous raffinate obtained in step ii. contains (i) nickel sulfate, (ii) cobalt sulfate, and (iii) magnesium at a concentration of 20 mg / L to 20 g / L, preferably 20 mg / L to 2 g / L, and more preferably 20 mg / L to 500 mg / L. Generally, the residual impurity content in the obtained first aqueous raffinate (A1) is too high for high-purity applications, and therefore it is subjected to a second solvent extraction step.

[0046] The second aqueous raffinate obtained in step iii. contains (i) nickel sulfate, (ii) and (ii) magnesium at a concentration of 20 mg / L to 20 g / L, preferably 20 mg / L to 2 g / L, more preferably 20 mg / L to 500 mg / L. Generally, the residual magnesium content in the obtained second aqueous raffinate (A2) is too high for high purity applications, so it is subjected to a third solvent extraction step to extract the magnesium.

[0047] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the aqueous mixed metal sulfate solution contains at least nickel, manganese, cobalt, and magnesium, and further contains one or more impurities selected from the group consisting of zinc, calcium, cadmium, iron, aluminum, and copper. Other impurities may be present as well. The present invention has the advantage that the elemental cobalt, magnesium, and manganese, as well as zinc, calcium, cadmium, iron, aluminum, and copper, if present, are completely separated from nickel in a simple, sequential solvent extraction process. This results in a high-purity aqueous nickel sulfate solution containing nickel at a concentration of 40-200 g / L and magnesium at a concentration of at most 10 mg / L, and three metal-containing organic phases: a manganese-rich organic phase containing manganese, magnesium, cobalt, and nickel, as well as zinc, copper, cadmium, and calcium, if present; a cobalt-rich organic phase containing a portion of the residual nickel and magnesium content; and a magnesium-rich organic phase containing nickel and magnesium. Preferably, the high purity aqueous nickel sulfate solution contains at most 5 mg / L of magnesium, even more preferably at most 1 mg / L of magnesium. The first, second, and / or third organic phases may contain modifiers.

[0048] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the aqueous mixed metal sulfate solution entering step ii. has a pH of 1.0 to 4.0, more preferably a pH of 1.5 to 3.5, and most preferably a pH of 2.0 to 3.0, before contacting the aqueous mixed metal sulfate solution with the solvent containing extractant I to establish chemical equilibrium between the aqueous nickel solution and the solvent.

[0049] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the first aqueous raffinate entering step iii. has a pH of 2.5 to 5.5, more preferably a pH of 3.0 to 5.0, and most preferably a pH of 3.5 to 4.5, before contacting the first aqueous raffinate with the solvent comprising extractant II to establish chemical equilibrium between the aqueous nickel solution and the solvent.

[0050] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the second aqueous raffinate entering step iv. has a pH of 4.0 to 6.5, more preferably a pH of 4.5 to 6.0, and most preferably a pH of 5.0 to 5.5, before contacting the second aqueous raffinate with the solvent containing extractant III to create chemical equilibrium between the aqueous nickel solution and the solvent.

[0051] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein said extraction in step iv. is carried out at a temperature of 45 to 65°C, preferably at a temperature of about 55°C.

[0052] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, further comprising the step of at least partially removing lithium from the aqueous mixed metal sulfate solution before step ii. The lithium from the feedstock may be removed before step ii. by washing before step i. Alternatively, lithium may be removed from the high-purity nickel sulfate solution obtained after step iv. Thus, in an alternative or complementary embodiment, the process further comprises the step of at least partially removing lithium from the aqueous mixed metal sulfate solution after step iv.

[0053] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein nickel is scrubbed from the manganese-rich organic phase, from the cobalt-rich organic phase, and / or from the magnesium-rich organic phase.

[0054] In a preferred embodiment, the present invention provides the process according to the first aspect of the invention, wherein the magnesium-depleted high-purity aqueous nickel sulfate solution comprises nickel at a concentration of 40 to 180 g / L and magnesium at a concentration of at most 5 mg / L.

[0055] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the aqueous mixed metal sulfate solution formed in step i. comprises nickel and cobalt in an amount of at least 30 atomic %, preferably at least 50 atomic %, more preferably at least 70 atomic %, and most preferably at least 85 atomic %, relative to the total metal content of the aqueous mixed metal sulfate solution. Preferably, the present invention provides a process according to the first aspect of the present invention, wherein the aqueous mixed metal sulfate solution formed in step i. comprises nickel and cobalt in an amount of at least 30 atomic %, preferably at least 60 atomic %, relative to the total metal content of the aqueous mixed metal sulfate solution, and wherein the aqueous mixed metal sulfate solution formed in step i. comprises magnesium, manganese, zinc, copper, and cadmium in an amount of at most 40 atomic %, relative to the total metal content of the aqueous mixed metal sulfate solution. Preferably, the aqueous mixed metal sulfate solution comprises nickel and cobalt in an amount of at least 75 atomic %, more preferably, the aqueous mixed metal sulfate solution comprises nickel and cobalt in an amount of at least 90 atomic %, and most preferably, the aqueous mixed metal sulfate solution comprises nickel and cobalt in an amount of at least 95 atomic %. In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the aqueous mixed metal sulfate solution formed in step i. further comprises calcium, zinc, copper, and cadmium in a combined amount of at most 25 atomic %, relative to the total metal content of the aqueous mixed metal sulfate solution. Preferably, the aqueous mixed metal sulfate solution further comprises calcium, zinc, copper, and cadmium in a combined amount of at most 10 atomic %, even more preferably, in an amount of at most 5 atomic %. Thereby, the aqueous mixed metal sulfate solution can be derived from any kind of source, such as mixed hydroxide precipitate, crude nickel sulfate, or any other type of suitable source, suitable per se or optionally processed into a suitable feed solution. This treatment may include leaching, selective leaching, dissolution, precipitation steps, and / or any other type of pretreatment step, and combinations of these are possible.For example, pretreated battery recycle material containing nickel, cobalt, manganese, and lithium can be processed in this flowsheet to produce a pure nickel sulfate solution and a pure cobalt salt solution, if the pretreatment includes at least leaching and finally prior lithium removal. Alternatively, lithium is removed at the end of step vi., for example, by a lithium ion exchange column.

[0056] In a preferred embodiment, the present invention provides the process according to the first aspect of the present invention, wherein the first, second, and third organic phases provided in steps ii., iii., and iv. comprise the first, second, and third extractants, respectively, in an amount of 5 to 50% by volume, based on the total volume of the solvent, and the diluent in an amount of 50 to 95% by volume, based on the total volume of the solvent.

[0057] In a preferred embodiment, the present invention provides the process according to the first aspect of the present invention, wherein the first organic phase used in step ii. comprises the first extractant (I) in an amount of 5 to 50% by volume, based on the total volume of the first organic phase, and the first diluent in an amount of 50 to 95% by volume, based on the total volume of the first organic phase. More preferably, the first organic phase comprises the first extractant (I) in an amount of 30 to 40% by volume, and the first diluent in an amount of 60 to 70% by volume.

[0058] In a preferred embodiment, the present invention provides the process according to the first aspect of the present invention, wherein the second organic phase used in step iii. comprises the second extractant (II) in an amount of 5 to 50% by volume, based on the total volume of the second organic phase, and the second diluent in an amount of 50 to 95% by volume, based on the total volume of the second organic phase. More preferably, the second organic phase comprises the second extractant (II) in an amount of 10 to 25% by volume, and the diluent in an amount of 75 to 90% by volume. It has been found that the extractant concentration in the organic phase allows optimal extraction of cobalt without compromising solvent processability.

[0059] In a preferred embodiment, the present invention provides the process according to the first aspect of the present invention, wherein the third organic phase used in step iv. comprises the third extractant (III) in an amount of 5 to 50% by volume, based on the total volume of the third organic phase, and the third diluent in an amount of 50 to 95% by volume, based on the total volume of the third organic phase. More preferably, the third organic phase comprises the third extractant (III) in an amount of 10 to 25% by volume, and the diluent in an amount of 75 to 90% by volume. It has been found that the extractant concentration in the organic phase allows optimal extraction of magnesium without compromising solvent processability.

[0060] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the first, second, and / or third diluent is a hydrocarbon. More generally, any organic, water-immiscible solvent capable of dissolving the extractant can be used. Thus, the diluent is not particularly limited. As an example of a diluent, a kerosene-based compound can be used, which may be aliphatic, naphthenic, aromatic, or even a mixture thereof.

[0061] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the first extractant is preloaded with nickel and / or cobalt, preferably nickel, to a concentration of at least 20% of the available extractant volume, i.e., converted to nickel and / or cobalt salts of the first extractant, preferably nickel salts of the first extractant. Preferably, the second and third extractants are preloaded with nickel to a concentration of at least 20% of the available extractant volume, i.e., converted to nickel salts of the second and third extractants. Preferably, the first, second, and third organic phases contain less than 2 g / L of sodium after preloading.

[0062] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the extractant used in step ii. comprises an alkylphosphorus acid and / or a nickel and / or cobalt salt of an alkylphosphorus acid, preferably a nickel salt of an alkylphosphorus acid. Preferably, the extractant used in steps iii. and iv., respectively, comprises an alkylphosphorus acid and / or a nickel salt of an alkylphosphorus acid. Suitable alkylphosphorus acids include bis(2-ethylhexyl)phosphoric acid (D2EHPA), (2-ethylhexyl)phosphonic acid mono(2-ethylhexyl)ester (EHEHPA, PC88A), bis-(2,4,4-trimethylpentyl)phosphinic acid (CYANEX272 or IONQUEST 290), and diisooctylphosphinic acid (DOPA). Alkylphosphorus acids act as chelating extractants due to the presence of coordinated phosphorus and oxygen atoms in their molecules. Among elements in an aqueous solution, elements that form corresponding chelate compounds with higher stability promote extraction efficiency compared to elements that do not form chelate compounds easily. The alkylphosphorus extractant can be selected from, but is not limited to, the following options: phosphoric acid, for example di-(2-ethylhexyl)phosphoric acid (also known as D2EHPA, DEHPA, HDEHP, P204), of the formula (CH 17 O) Organophosphorus compounds with 2PO2H. -phosphonic acids, such as 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (also known as EHEHPA, HEHEHP, P507, PC88A), formula R = (CH 17 )(C8H 17 O) Organophosphorus compounds with PO2H. phosphinic acids, such as bis-(2,4,4-trimethylpentyl)phosphinic acid (also known as Cyanex 272, Ionquest 290), 16 H 34 )Organophosphorus compounds with PO2H.

[0063] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the first extractant (I) has a higher selectivity for calcium over nickel than the second extractant (II). In other words, the first extractant (I) has a higher affinity for calcium relative to nickel than the second extractant (II) has for calcium over nickel. Furthermore, the first extractant (I) has a higher selectivity for calcium over nickel. Most preferably, the first extractant (I) comprises an alkyl phosphate such as D2EHPA. Preferably, the first alkylphosphorus extractant (I) comprises an alkyl phosphate and / or a nickel and / or cobalt salt of an alkyl phosphate, and the second alkylphosphorus extractant (II) comprises an alkyl phosphonic acid and / or a nickel salt of an alkyl phosphonic acid.

[0064] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the third extractant (III) has a higher selectivity for magnesium than the first extractant (I) and the second extractant (II). In other words, the third extractant (III) has a higher affinity for magnesium than the affinity of the first extractant (I) and the second extractant (II). Furthermore, the third extractant (III) has a higher selectivity for magnesium than its selectivity for nickel. Most preferably, the third extractant (III) comprises an alkylphosphinic acid such as IONQUEST 290.

[0065] In a preferred embodiment, the extractant used in steps ii, iii, and iv is neutralized with an alkali metal hydroxide and preloaded with nickel at a high pH before use in the extractions in steps ii-iv. The nickel-preloaded organic phase is then contacted with an aqueous nickel sulfate solution containing metal impurities. In this case, an exchange reaction occurs in which elements more easily extracted than nickel are transferred to the solvent, while nickel in the organic phase is transferred to the aqueous phase. As a result, impurities are removed from the mixed metal sulfate aqueous solution while increasing the nickel concentration in the resulting raffinate solution, thereby largely avoiding the introduction of alkali metals from the neutralizer into the main process (raffinate) stream. Examples of alkali metal hydroxides that can be used include sodium hydroxide, potassium hydroxide, and ammonium hydroxide. Furthermore, sodium hydroxide is preferably used as the alkali metal hydroxide. Alternatively, the extractant used in step ii can be preloaded with cobalt or a mixture of nickel and cobalt.

[0066] It has been found that preloading the extractant used in steps ii-iv with nickel allows for optimal and improved extraction without compromising the processability of the extractant. During this preloading step, the partially neutralized extractant, i.e., the extractant in its alkali metal converted form, exchanges the extractant's alkali metal, typically sodium, with nickel or cobalt from the aqueous nickel sulfate solution. Preferably, the residual amount of alkali metal in the preloaded solvent is as low as possible to limit the transfer of residual alkali metal from the preloaded solvent to the aqueous mixed metal sulfate solution when extracting impurities from the solution.

[0067] A portion of the nickel may be replaced by another harmless metal that replaces the impurities extracted from the aqueous nickel sulfate solution to be purified. This may be an alkali metal such as sodium or potassium, or a similar species such as ammonium. However, these other metals may result in the extraction of such metals present in the aqueous nickel sulfate solution to be purified, or may further contaminate the nickel sulfate solution by replacing the impurities to be extracted.

[0068] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, in which the extractant is converted prior to extraction into its nickel and / or cobalt salt, preferably the nickel salt corresponding to the appropriate conversion of the extractant, thus containing nickel in an amount of 20-70% of the available extractant volume and residual sodium at a concentration of at most 2 g / L, preferably at most 0.5 g / L, and more preferably at most 0.1 g / L. Preferably, nickel is preloaded to an amount of 25-60% of the available extractant volume, preferably greater than 30% of the available extractant volume, with residual sodium at a concentration of at most 0.5 g / L. More preferably, nickel is preloaded to an amount of 30-50% of the available extractant volume, with residual sodium at a concentration of at most 0.1 g / L. For step ii., cobalt salts or combined nickel-cobalt salts are also possible, with the same specifications as for nickel.

[0069] Therefore, the preferred nickel concentration of the preloaded solvent depends on the extractant concentration and the degree of conversion, both of which are determined by the target pH in the mixed metal sulfate aqueous solution and are therefore a function of the total amount of impurities to be removed. A higher degree of conversion of the extractant results in a higher pH during extraction, allowing for higher extraction of impurities (and nickel) from the nickel-containing feed solution, while a lower degree of conversion of the extractant results in a lower pH during extraction, allowing for better selectivity over impurities towards nickel.

[0070] In a preferred embodiment, the preloaded solvent containing nickel and, optionally, some other metal, such as sodium, potassium, or others, or other cation, such as ammonium, may be contacted again with a pure nickel-containing solution, such as a nickel sulfate or nickel chloride solution, to further replace the metallic sodium, potassium, ammonium, or others of the solvent with nickel from the pure nickel-containing solution. The nickel preloading, cobalt preloading, or nickel-cobalt preloading operation can be carried out in two or more stages, preferably in countercurrent operation, with at least a pure nickel sulfate solution, optionally to scrub from the solvent any alkali metals co-extracted from the spent base. As a result, a nickel-preloaded solvent containing significantly fewer other metals is obtained that can be used in extraction steps ii.-iv., thus maximally avoiding contamination of the aqueous nickel solution with undesired metals.

[0071] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, comprising step v., which comprises stripping the manganese-rich organic phase obtained in step ii. with an aqueous solution containing a mineral acid. This effectively results in the leaching of manganese, calcium, and, if present, zinc, copper, and cadmium from the first solvent. Preferably, the mineral acid is one or more selected from the group consisting of hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and perchloric acid. More preferably, the mineral acid is one or more selected from the group consisting of hydrochloric acid, hydrobromic acid, nitric acid, phosphoric acid, and perchloric acid. In another embodiment, the mineral acid is sulfuric acid. Considering the presence of calcium in the resulting stripping solution, it is most preferred to use hydrochloric acid. This results in a concentrated leaching solution containing manganese and calcium, and, if present, zinc, copper, cadmium, and a residual amount of nickel, along with a residual amount of cobalt from the first solvent. In this way, the extractant is regenerated to obtain a metal-free solvent that can be reused for extraction or preloading. Considering the presence of calcium in the resulting stripping solution, the use of hydrochloric acid is preferred. Stripping with hydrochloric acid forms calcium chloride, which is readily soluble in water. In this way, metal-containing materials can be concentrated from the solvent into an aqueous solution. Considering the low solubility of calcium sulfate, the use of sulfuric acid can induce the formation of solid precipitates that interfere with the solvent extraction process. In a preferred embodiment, the hydrochloric acid solution has a concentration of at least 50 g / L, more preferably 100 g / L to 300 g / L.

[0072] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, comprising step vi., which comprises stripping the cobalt-rich organic phase obtained in step iii. with an aqueous solution containing a mineral acid. This effectively results in leaching of cobalt from the second solvent. Preferably, the mineral acid is one or more selected from the group comprising hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and perchloric acid. More preferably, the mineral acid is one or more selected from the group comprising hydrochloric acid, hydrobromic acid, nitric acid, sulfuric acid, phosphoric acid, and perchloric acid. Most preferably, the mineral acid is sulfuric acid or hydrochloric acid. This results in a concentrated leaching solution containing cobalt.

[0073] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, comprising the step of stripping the magnesium-rich organic phase obtained in step iv. with an aqueous solution containing a mineral acid. Preferably, the mineral acid is one or more selected from the group comprising hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and perchloric acid. More preferably, the mineral acid is one or more selected from the group comprising hydrochloric acid, hydrobromic acid, nitric acid, sulfuric acid, phosphoric acid, and perchloric acid. Most preferably, the mineral acid is sulfuric acid. This allows a concentrated eluate solution containing magnesium to be obtained, and the solvent to be regenerated.

[0074] The stripping step can be carried out in any suitable device, without particular limitation. Stripping equipment generally comprises at least one device consisting of a mixer settler, a column contactor, a centrifugal contactor, or any other type of contactor. Preferably, stripping is carried out in a countercurrent configuration.

[0075] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein the stripping steps v. and / or vi. are carried out at a temperature of from 40°C to 60°C, preferably from 40°C to 50°C, more preferably at a temperature of about 45°C.

[0076] In a preferred embodiment, the present invention provides a post-treatment step according to the first aspect of the present invention, wherein the manganese-rich organic phase is further washed with sulfuric acid after being stripped with hydrochloric acid in step v. Washing with sulfuric acid allows chloride ions, and possibly residual metals such as iron or aluminum, to be removed from the solvent. In this way, the solvent is regenerated and can be reused for extraction after being preloaded.

[0077] In a preferred embodiment, the present invention provides a post-treatment step according to the first aspect of the present invention, wherein the high-purity aqueous nickel sulfate solution obtained in step iv. contains nickel at a concentration of 40 to 180 g / L and magnesium at a concentration of at most 5 mg / L, preferably at most 1 mg / L. Preferably, the high-purity aqueous nickel sulfate solution has a content of calcium, iron, aluminum, zinc, copper, manganese, cobalt, magnesium, and / or cadmium, each individually in an amount of at most 10 mg / L, preferably at most 5 mg / L, or even at most 1 mg / L.

[0078] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein at least a portion of the high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization without further purification, and the formed nickel sulfate crystals are used for preparing a cathode precursor material for lithium-ion batteries.

[0079] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein at least a portion of the high purity nickel sulfate solution obtained in step iv. is used without further purification to prepare a cathode precursor material for a lithium-ion battery.

[0080] The present invention is particularly suitable for the treatment of raw feeds containing nickel and cobalt compounds, such as, but not limited to, MHP, CHIP, etc. Advantageously, the high purity nickel sulfate solution obtained in step iv. does not require further extraction.

[0081] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein at least a portion of the high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization, at least a portion of the mother liquor formed during crystallization is bled, and at least a portion of the crystallizer bleed is used to preload one or more organic phases used in steps i., ii., and iii. The crystallizer bleed typically has a relatively large amount of sodium. By recycling the crystallizer bleed to any of the solvent extraction steps ii., iii., and / or iv., it is possible to recover the nickel sulfate present in the crystallizer bleed, while simultaneously allowing the sodium present in the bleed to be bled out of the flowsheet via the raffinate of the preloading step.

[0082] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein the high-purity aqueous nickel sulfate solution obtained after removal of residual magnesium in step iv. is subjected to crystallization or granulation. Preferably, the nickel sulfate in the nickel sulfate solution is crystallized, thereby enabling an additional purification step. In the case of granulation, any granulation technique known to those skilled in the art is suitable, such as, for example, spray drying. In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, wherein at least a portion of the mother liquor formed from the crystallization unit is recycled upstream. Preferably, the crystallizer bleed containing saturated nickel sulfate solution is used to preload nickel into one or more extractants, specifically, to preload nickel into one or more extractants used in one or more of steps ii., iii., and / or iv.

[0083] In a preferred embodiment, the present invention provides a process according to the first aspect of the present invention, in which nickel is scrubbed from the manganese-rich organic phase, the cobalt-rich organic phase, and / or the magnesium-rich organic phase. To recover this co-extracted nickel from the loaded organic phase before proceeding to the elution section, the co-extracted nickel is first selectively scrubbed from these solvents by washing with an acidic solution, such as aqueous sulfuric acid. Nickel is selectively scrubbed by applying optimum pH conditions, specifically the acidity of the final scrub solution, and the amount of acid added is adapted to reach this required pH.

[0084] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein the first, second and / or third organic phase, after washing or stripping with sulfuric acid, is loaded with nickel using alkali hydroxide and a nickel and / or cobalt salt containing solution, such as a nickel and / or cobalt sulfate solution or a nickel and / or cobalt chloride solution, and then recycled in step ii., step iii. and / or step iv., thereby closing the process loop.

[0085] In a preferred embodiment, the present invention provides a process according to the first aspect of the invention, wherein the aqueous mixed metal sulfate solution is obtained by removing iron and / or aluminium from an aqueous mixed metal sulfate solution comprising nickel, cobalt, manganese, magnesium, and, if present, zinc, copper, cadmium, and / or calcium, and further comprising iron and / or aluminium, respectively. The iron and / or aluminium may advantageously be removed by adding a basic reagent, such as a hydroxide, to the aqueous solution, thereby forming an iron and / or aluminium hydroxide precipitate. Potentially, the addition of an oxidizing agent, for example oxygen or hydrogen peroxide, may be included in the aforementioned iron and / or aluminium removal step.

[0086] In a preferred embodiment, the iron and / or aluminum is removed by precipitation using a calcium base, such as calcium hydroxide, calcium oxide, calcium carbonate, calcium bicarbonate, or any other calcium-containing basic reagent. The use of a calcium base is advantageous because calcium forms calcium sulfate, also known as gypsum, which has low aqueous solubility in this step of the process. Therefore, the use of an excess amount of calcium base is not detrimental to the purity of the resulting nickel sulfate solution. Only a limited amount of calcium remains in the nickel solution sent to solvent extraction step II. The latter process is designed to completely remove calcium from the nickel solution. The formation of calcium sulfate during the precipitation of iron and / or aluminum enhances the filterability of the iron and / or aluminum precipitate. Therefore, it may be preferable to use a calcium base in stoichiometric excess relative to the amount of iron and / or aluminum impurities present in the aqueous mixed-metal sulfate solution containing nickel, cobalt, magnesium, and iron and / or aluminum.

[0087] In another preferred embodiment, the base used may be nickel hydroxide or carbonate, or any other nickel-containing basic reagent, which will introduce beneficial nickel ions into the nickel sulfate solution. Other preferred nickel bases are nickel bicarbonate and nickel hydroxysulfate.

[0088] In another preferred embodiment, the base used may be cobalt hydroxide or carbonate, or any other cobalt-containing basic reagent, which introduces into the nickel sulfate solution the cobalt ions that are removed in step iii. Other preferred cobalt bases are cobalt bicarbonate and cobalt hydroxysulfate.

[0089] In yet another preferred embodiment, the base used may be magnesium hydroxide or carbonate, or any other magnesium-containing basic reagent, since magnesium can be efficiently and effectively removed in subsequent steps of the process of the present invention. Other preferred magnesium bases are magnesium bicarbonate and magnesium hydroxysulfate.

[0090] In yet another preferred embodiment, impurities such as iron and / or aluminum can be separated by precipitation using a combination of two or more precipitants selected from calcium bases, magnesium bases, cobalt bases, and nickel bases.

[0091] Furthermore, impurities such as iron and / or aluminum may be removed by precipitation in two or more precipitation steps, and a different precipitant may be used in each precipitation step. In a preferred embodiment, a nickel base is used in the first precipitation step and a calcium base is used in subsequent precipitation steps.

[0092] Alternatively, impurities such as iron and / or aluminum can be separated by other methods such as neutralization. However, the use of an alkaline base such as sodium hydroxide or potassium hydroxide will introduce metal impurities into the aqueous mixed metal sulfate solution that cannot be extracted by a subsequent solvent extraction process, and thus may complicate any potential crystallization or granulation processes at the end of the flowsheet.

[0093] In another embodiment, calcium is already present in the nickel feed solution entering solvent extraction step ii, either because it was previously introduced with the feedstock or by using a calcium-containing reagent such as calcium hydroxide, calcium oxide, calcium carbonate, calcium bicarbonate, or a calcium base as another calcium-containing basic reagent prior to entering solvent extraction step ii. [Example]

[0094] For each process step, examples are provided to further clarify the invention, but these examples are based on experimentally obtained data and are not intended to limit the scope of the invention.

[0095] Manganese extraction from mixed metal sulfate solutions A first organic phase is used that is composed of 25% by volume of D2EHPA with Escaid 110 as diluent. The extractant is saponified to 49% with 400 g / L of NaOH.

[0096] A feed solution having the following composition is subjected to extraction:

[0097] [Table 1]

[0098] Manganese extraction is carried out in a four-step batch mode at O / A=0.25 and a temperature of 30° C. The raffinate composition is also reported in the table above. Manganese, calcium, and zinc are removed to less than 1 mg / L in the raffinate.

[0099] Extraction of cobalt from mixed metal sulfate solutions A first organic phase composed of 35% by volume of Cyanex 272 is used, with Escaid 110 as the diluent. The extractant is first 58% saponified with 400 g / L NaOH and then preloaded with nickel to 12.9 g / L nickel and 120 mg / L sodium from a preload solution composed of 110 g / L nickel and 960 mg / L sodium.

[0100] A feed solution having the following composition is subjected to extraction:

[0101] [Table 2]

[0102] Cobalt extraction is carried out in a four-step batch mode at O / A=1.0 and a temperature of 55° C. The raffinate composition is also reported in the table above. Cobalt is removed to less than 1 mg / L in the raffinate.

[0103] Extraction of magnesium from mixed metal sulfate solutions A first organic phase composed of 15% by volume of Ionquest 290 is used, with Escaid 110 as diluent. The extractant is preloaded to 6.2 g / L of nickel in the solvent from a solution containing 130 g / L of nickel under injection of 125 g / L of sodium hydroxide solution.

[0104] A feed solution having the following composition is subjected to extraction:

[0105] [Table 3]

[0106] The magnesium extraction is carried out in a 5-step batch mode at O / A=0.5 and a temperature of 55° C. The raffinate composition is also reported in the table above. Magnesium is removed to less than 1 mg / L in the raffinate.

Claims

1. 1. A process for preparing a high purity nickel sulfate solution, comprising: i. forming an aqueous mixed metal sulfate solution by reacting sulfuric acid with a raw material feed comprising nickel, manganese, cobalt, and magnesium in an aqueous medium; ii. Extracting manganese from the aqueous mixed metal sulfate solution at a temperature of 20-45°C using a first organic phase containing a first alkylphosphorus extractant (I) containing alkyl phosphoric acid and / or a nickel salt of the alkyl phosphoric acid and a first diluent, thereby obtaining a first aqueous raffinate containing nickel, cobalt, and magnesium and a manganese-rich organic phase; iii. Extracting cobalt from the first aqueous raffinate at a temperature of 45-65°C using a second organic phase containing a second alkylphosphorus extractant (II) containing an alkylphosphinic acid and / or a nickel salt of the alkylphosphinic acid and a second diluent, thereby obtaining a second aqueous raffinate containing nickel and residual magnesium content and a cobalt-rich organic phase; iv. Extracting magnesium from the second aqueous raffinate using a third organic phase comprising a third alkylphosphorus extractant (III) containing an alkylphosphinic acid and / or nickel from the alkylphosphinic acid, and a third diluent, thereby obtaining a high-purity nickel sulfate solution and a magnesium-enriched organic phase.

2. 2. The process of claim 1, wherein the raw material feed further comprises iron and / or aluminum, and prior to step ii., a base is added to the aqueous mixed metal sulfate solution formed in step i., thereby forming a precipitate comprising iron and / or aluminum, respectively, and the precipitate is filtered off.

3. 3. The process of claim 2, wherein the base comprises a calcium base, a magnesium base, a cobalt base, a nickel base, or a combination of two or more of the foregoing bases.

4. 10. The process of claim 1, wherein at least a portion of the high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization without further purification, and the formed nickel sulfate crystals are used to prepare a cathode precursor material for a lithium-ion battery.

5. 10. The process of claim 1, wherein at least a portion of the high-purity nickel sulfate solution obtained in step iv. is used without further purification to directly prepare a cathode precursor material for a lithium-ion battery.

6. 4. The process of claim 1, further comprising stripping the magnesium-rich organic phase obtained in step iv with an aqueous solution containing a mineral acid.

7. 7. The process according to any one of claims 1 to 6, wherein the extraction in step iv. is carried out at a temperature of 45 to 65°C.

8. 10. The process of claim 1, wherein the first, second, and third extractants are preloaded with nickel to a concentration of at least 20% of the available extractant volume, i.e., converted to nickel salts of the first, second, and third extractants.

9. 2. The process of claim 1, wherein at least a portion of the high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization, at least a portion of the mother liquor formed during crystallization is bled, and at least a portion of the crystallizer bleed is used to precharge one or more of the organic phases used in steps i., ii., and iii.

10. 10. The process of claim 1, further comprising the step of at least partially removing lithium from the aqueous mixed metal sulfate solution prior to step ii.

11. 2. The process of claim 1, further comprising a step (v) comprising stripping the manganese-rich organic phase obtained in step (ii) with an aqueous solution comprising a mineral acid.

12. 2. The process of claim 1, further comprising a step (vi) comprising stripping the cobalt-rich organic phase obtained in step (iii) with an aqueous solution comprising a mineral acid.

13. 2. The process of claim 1, wherein the first, second, and third organic phases provided in steps ii., iii., and iv. comprise the first, second, and third extractants in amounts of 5 to 50% by volume, based on the total volume of the first, second, and third organic phases, respectively, and the diluent in amounts of 50 to 95% by volume, based on the total volume of the first, second, and third organic phases.

14. 2. The process of claim 1, wherein nickel is scrubbed from the manganese-rich organic phase, from the cobalt-rich organic phase, and / or from the magnesium-rich organic phase.

15. 10. The process of claim 1, wherein cobalt is scrubbed from the manganese-rich organic phase.

16. 2. The process of claim 1, wherein the aqueous mixed metal sulfate solution formed in step i. comprises nickel and / or cobalt in an amount of at least 60 atomic %, based on the total metal content of the aqueous mixed metal sulfate solution, and the aqueous mixed metal sulfate solution formed in step i. comprises calcium, magnesium, zinc, copper, and cadmium in an amount of at most 40 atomic %, based on the total metal content of the aqueous mixed metal sulfate solution.

17. 13. The process of claim 11 or 12, wherein the first and / or second organic phase is washed with sulfuric acid after being stripped with the mineral acid.

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