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BR-112025003471-B1 - PROCESS FOR PREPARING A HIGH-PURITY NICKEL SULFATE SOLUTION

BR112025003471B1BR 112025003471 B1BR112025003471 B1BR 112025003471B1BR-112025003471-B1

Abstract

PROCESS FOR PREPARING A HIGH-PURITY NICKEL SULFATE SOLUTION. The present invention provides a process for preparing a high-purity nickel sulfate solution, comprising the steps of: i. forming an aqueous solution of mixed metal sulfate by reacting sulfuric acid with a feedstock comprising nickel, manganese, cobalt, and magnesium in an aqueous medium; ii. extracting the manganese from said aqueous solution of mixed metal sulfate, thereby obtaining a first aqueous raffinate comprising nickel, cobalt, and magnesium, and a manganese-rich organic phase; iii. extracting the cobalt from said first aqueous raffinate, thereby obtaining a second aqueous raffinate comprising nickel and magnesium and a cobalt-rich organic phase; and iv. extracting the magnesium from said second aqueous raffinate solution, thereby obtaining a high-purity nickel sulfate solution and a magnesium-rich organic phase.

Inventors

  • Werner VERDICKT
  • Joris ROOSEN
  • Wannes DE MOOR
  • Jan Luyten

Assignees

  • UMICORE

Dates

Publication Date
20260310
Application Date
20230823
Priority Date
20220824

Claims (17)

  1. 1. Process for preparing a high-purity nickel sulfate solution characterized by comprising the steps of: i. forming an aqueous solution of mixed metal sulfate by reacting sulfuric acid with a feedstock comprising nickel, manganese, cobalt and magnesium in an aqueous medium; ii. extracting manganese from said aqueous solution of mixed metal sulfate at a temperature between 20 and 45 °C using a first organic phase comprising a first alkylphosphorus (I) based extractant and a first diluent, wherein said first alkylphosphorus (I) based extractant comprises an alkylphosphoric acid and/or nickel salts thereof, thereby obtaining a first aqueous raffinate comprising nickel, cobalt and a magnesium content, and a manganese-rich organic phase; iii. extract the cobalt from said first aqueous raffinate at a temperature between 45 and 65 °C using a second organic phase comprising a second alkylphosphorus (II) based extractant and a second diluent, wherein said second alkylphosphorus (II) based extractant comprises an alkylphosphinic acid and/or nickel salts thereof, thereby obtaining a second aqueous raffinate comprising nickel and a residual magnesium content and a cobalt-rich organic phase; and iv. extract the magnesium from said second aqueous raffinate solution using a third organic phase comprising a third alkylphosphorus (III) based extractant and a third diluent, wherein said third alkylphosphorus (III) based extractant comprises an alkylphosphinic acid and/or nickel salts thereof, thereby obtaining a high-purity nickel sulfate solution and a magnesium-enriched organic phase.
  2. 2. Process according to claim 1, characterized in that said feedstock additionally comprises iron and/or aluminum, and wherein, prior to step ii., a base is added to said aqueous solution of mixed metal sulfate formed in step i., thereby forming a precipitate comprising iron and/or aluminum, respectively, and wherein said precipitate is filtered.
  3. 3. Process according to claim 2, characterized in that said base comprises a calcium base, a magnesium base, a cobalt base, a nickel base, or a combination of two or more of the aforementioned bases.
  4. 4. A process according to any one of claims 1 to 3, characterized in that at least part of said high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization without further purification, and wherein the nickel sulfate crystals formed are used to prepare a cathode precursor material for lithium-ion batteries.
  5. 5. Process, according to any one of claims 1 to 4, characterized in that at least part of the high-purity nickel sulfate solution obtained in step iv. is used without further purification to directly prepare a cathode precursor material for lithium-ion batteries.
  6. 6. Process, according to any one of claims 1 to 5, characterized by comprising the step of stripping said magnesium-enriched organic phase obtained in step iv. with an aqueous solution comprising a mineral acid.
  7. 7. Process, according to any one of claims 1 to 6, characterized in that said extraction in step iv. is carried out at a temperature between 45 and 65 °C.
  8. 8. Process, according to any one of claims 1 to 7, characterized in that said first, second and third extractants are pre-loaded with nickel, that is, converted into nickel salts, at a concentration of at least 20% of the available extractant capacity.
  9. 9. A process according to any one of claims 1 to 8, characterized in that at least part of said high-purity nickel sulfate solution obtained in step iv. is subjected to crystallization, wherein at least part of the mother liquor formed during crystallization is bled off and wherein at least part of the crystallizer bleed off is used for pre-loading one or more organic phases used in steps i., ii. and iii.
  10. 10. Process, according to any one of claims 1 to 9, characterized by further comprising the step of removing, at least in part, lithium from said aqueous mixed metal sulfate solution prior to step ii.
  11. 11. Process, according to any one of claims 1 to 10, characterized by comprising step v., wherein step v. comprises stripping the manganese-rich organic phase obtained in step ii. with an aqueous solution comprising a mineral acid.
  12. 12. Process, according to any one of claims 1 to 11, characterized by comprising step vi., wherein step vi. comprises stripping the cobalt-rich organic phase obtained in step iii. with an aqueous solution comprising a mineral acid.
  13. 13. Process, according to any one of claims 1 to 12, characterized in that said first, second and third organic phases provided in steps ii., iii. and iv. comprise said first, second and third extractants, respectively, in an amount of 5 to 50% by volume, relative to the total volume of said solvents, and said diluents in an amount of 50 to 95% by volume, relative to the total volume of said solvents.
  14. 14. Process, according to any one of claims 1 to 13, characterized in that nickel is purified from said manganese-rich organic phase, said cobalt-rich organic phase and/or said magnesium-enriched organic phase.
  15. 15. Process, according to any one of claims 1 to 14, characterized in that cobalt is purified from the manganese-rich organic phase.
  16. 16. Process, according to any one of claims 1 to 15, characterized in that said aqueous mixed metal sulfate solution formed in step i. comprises nickel and/or cobalt in an amount of at least 60% at., relative to the total metal content of said aqueous mixed metal sulfate solution, and in that said aqueous mixed metal sulfate solution formed in step i. comprises calcium, magnesium, zinc, copper and cadmium in an amount of at most 40% at., relative to the total metal content of said aqueous mixed metal sulfate solution.
  17. 17. Process, according to any one of claims 11 to 16, characterized in that said first and/or second organic phase, after pickling with said mineral acid, is washed with sulfuric acid.

Description

TECHNICAL FIELD [0001] The present invention relates to an innovative method for producing a high-purity aqueous nickel sulfate solution with sufficient purity for use in the non-electrical deposition of metallic nickel layers or in the production of battery materials. INTRODUCTION [0002] The development of lithium-ion batteries and, specifically, the use of nickel-manganese-cobalt and nickel-cobalt-aluminum cathode materials, has increased the demand for high-purity nickel sulfate, either in solid form or in solution. In fact, impurities in cathode materials strongly affect battery performance. As such, much effort has been devoted to producing high-purity nickel sulfate in an industrially viable process. [0003] In this regard, US patent 2014 322109 provides a method for obtaining high-purity nickel sulfate having 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 refined by solvent removal to remove cobalt and magnesium impurities, adjusting the concentration of an acidic organic extractant and the pH or acid concentration at the time of treatment. The processing strategy described is complicated for concentrated nickel sulfate solutions, as it requires an intermediate precipitation and redissolution of the nickel mass, followed by solvent removal to remove cobalt and magnesium impurities. Especially the nickel sulfide step is hazardous due to the risk of hydrogen sulfide generation. Furthermore, solvent extraction is only used to remove cobalt and magnesium, even though raw nickel materials typically contain far more impurities. [0004] Document CN 107 162 067 relates to the field of solid waste recycling and particularly discloses a method for recycling high-purity nickel sulfate from nickel-containing battery waste. The method comprises the steps of disassembling nickel-containing battery waste into battery powder, dissolving the battery powder with an acid to obtain a metal-containing solution, adding alkaline metal sulfate, removing iron by an oxidative precipitation process, further removing impurities by means of a solvent extraction process to obtain magnesium-containing nickel liquid, passing the magnesium-containing nickel liquid through chelating resin exchange columns to selectively adsorb nickel ions and allow a magnesium-rich solution to flow for treatment, desorbing the nickel ions to obtain a nickel sulfate solution, evaporating the nickel sulfate solution, cooling, crystallization, filtration and finally drying to obtain the purified nickel sulfate product. Through this lengthy and complex process, it is guaranteed that the recycled nickel sulfate is a high-purity product with a nickel content of up to 99.5% or higher, while the impurity content, i.e., magnesium, is less than 0.005%. However, three different solvent extraction units are proposed to remove copper, manganese, and cobalt in separate stages. Besides the high investment costs, other impurities, such as calcium and magnesium, are not even supposedly removed. Finally, the nickel is recovered by adsorption onto a resin, requiring a fourth separation stage and consumption of a neutralizing agent equivalent to the amount of metal ions adsorbed. Overall, the described process is neither considered simple nor efficient. [0005] Document EP 1 252 345 B1 describes a process for extracting cobalt from a cobalt-nickel solution with a nickel-laden solvent to obtain a purified nickel sulfate stream. However, it does not explain how to remove impurities such as calcium and magnesium to very low levels in order to produce a purified nickel sulfate solution for electrolyte-free nickel applications or batteries. Further research is being conducted to develop a solvent extraction process where the formation of insoluble ammonium/nickel sulfate double salts can be avoided. [0006] Document EP 2 784 166 describes a process for producing a pure nickel sulfate solution in multiple process steps, including a sulfuration step, a redissolution step, a precipitation purification step, and a solvent extraction step. The sulfuration and redissolution steps, in particular, are expensive operations that use a sulfurizing agent and produce an intermediate nickel sulfide; both products are toxic and can lead to the generation of highly toxic gaseous hydrogen sulfide upon contact and reaction with mineral acids. In the end, the purified nickel sulfate solution still contains 50 mg/l of magnesium impurity, which is excessive for nickel sulfate used in batteries, demonstrating the lack of selectivity of the proposed process. [0007] Document EP 3 733 884 describes a solvent extraction method that allows the selective separation of magnesium from an acidic aqueous solution of sulfuric acid. The solvent extraction method involves contacting an acidic aqueous solution of sulfuric acid containing n