Mixed hydroxide precipitate refining

Abstract

The invention provides hydrometallurgical processes for treating a nickel and cobalt mixed hydroxide precipitate, using recycled ammonia for pH adjustment in successive stages of selective solvent extraction. 5

Description

MIXED HYDROXIDE PRECIPITATE REFININGFIELD

[0001] The invention is in the field of hydrometallurgy, relating to processes involving recovery of metal values by solvent extraction.BACKGROUND

[0002] Mixed hydroxide precipitate (MHP) is an intermediate nickel product, typically produced from laterite nickel ore using a high-pressure acid leaching process, which can contain both nickel and cobalt values. The refining of MHP is commercially well established, the classic approach being to releach the MHP in sulfuric acid solution under controlled pH conditions. The pH may be controlled to maximize the extraction of the divalent metals (e.g. Ni, Co, Cu, Zn, Mn, Mg, etc) and to minimize the extraction of trivalent metals (e.g. Fe, Al and Cr). Typically, any monovalent ions (eg. Na and Cl) will extract under these conditions.

[0003] The acid extraction can be controlled by allowing for some oxidation and precipitation of iron. For example if Fe is present as Fe(ll), the iron will extract with the other divalents. Addition of an oxidant and a pH adjustment may be required. For example hydrogen peroxide and lime or sodium hydroxide / sodium carbonate can be added to raise the pH and precipitate Fe to low levels.

[0004] Solvent extraction may be used to separate the non-nickel ions away from the nickel. This is often done in two steps with a di-(2-ethylhexyl) phosphate (D2EHPA) and a Cyanex 801 (2-ethylhexyl 2-ethylhexyl phosphonic acid) or Cyanex 272 (bis (2,4,4-trimethylpentyl) phosphinic acid) solvent extractant.D2EHPA can for example be used so as to separate Ca / Cu / Zn / Mn / Co(partial) from nickel. D2EHPA will generally also extract residual Fe / AI / Cr, provided all elements are in the trivalent state. Cyanex 801 and Cyanex 272 may be used to remove residual Co and Mn away from Ni, as well as ensure even lower background levels of other contaminants. Effective solvent extraction with D2EHPA and Cyanex 801 / Cyanex 272 requires pH control, and typically the requirement is for stoichiometric use of base to remove each element from solution. Sodiumhydroxide or sodium carbonate have been used for this duty. The relevant reactions may for example include:D2EHPA Solvent Extraction (HR(org) represents D2EHPA); Cyanex 801 or Cyanex 272 Solvent Extraction (HR(org) represents Cyanex 801 or Cyanex 272) CaSC>4 + 2HR(org) + 2NaOH = CaR2(org) + Na2SC>4 + 2H2O CuSC>4 + 2HR(org) + 2NaOH = CuR2(org) + Na2SC>4 + 2H2O ZnSO4 + 2HR(org) + 2NaOH = ZnR2(org) + Na2SO4+ 2H2O MnSC + 2HR(org) + 2NaOH = MnR2(org) + Na2SO4+ 2H2O CoSO4 + 2HR(org) + 2NaOH = CoR2(org) + Na2SC>4 + 2H2O Fe2(SO4)3+ 6HR(org) + 6NaOH = 2FeR3(org) + 3Na2SO4+ 6H2O AI2(SO4)3 + 6HR(org) + 6NaOH = 2AIR3(org) + 3Na2SO4+ 6H2O Cr2(SO4)3+ 6HR(org) + 6NaOH = 2CrR3(org) + 3Na2SO4+ 6H2O

[0005] Following solvent extractions of this kind, the principal remaining divalent elements in solution are nickel and magnesium. The extraction of nickel in the presence of magnesium can be accomplished with Versatic 10 solvent extractant using a suitable base for pH control, as follows:Versatic 10 Solvent Extraction (HR(org) represents Versatic 10) NiSC + 2HR(org) + 2NaOH = NiR2(org) + Na2SO4+ 2H2O

[0006] In commercial embodiments, the solvent extraction processes described above will typically include multiple counter current stages of contact between aqueous and organic phases, the use of scrubbing to selectively remove coextracted species, and stripping to recover loaded metals from the organic phase. For example, a loaded D2EHPA organic phase may be scrubbed to remove cobalt and nickel that is co-extracted with zinc, calcium, copper and manganese, preferentially scrubbing cobalt and nickel into an aqueous scrub raffinate (which may be recycled to the D2EHPA extraction stage). A D2EHPA scrubbing solution may for example be a solution that includes dissolved manganese and / or copper. Finally, a regeneration step may be used to remove difficult to strip metals to refresh the organic extractant for maximum efficiency.

[0007] Following pH adjustment with base to facilitate extraction into the organic phase, the loaded organic solutions in each solvent extraction can generally bestripped with acid. Hydrochloric acid solutions can for example be used to strip calcium containing organics to avoid the precipitation of gypsum (CaSC>4.2H2O). Gypsum precipitation results in solid accumulation, crud formation and blocking of pipes and launders with scale and is generally undesirable in solvent extraction processes. Accordingly, a hydrochloric acid strip solution may be used to form soluble CaCh in the strip solution and avoid formation of gypsum. Sulfuric acid strip solutions may be used to strip nickel and, if a second impurity removal step is used following the first impurity step targeting calcium removal, as summarized below: Nickel Stripping from Nickel Loaded Versatic 10 Solvent Extractant (HR(org) represents Versatic 10)NiR2(org) + H2SO4 = NiSC + 2HR(org)

[0008] Chloride or sulfate based strip solutions from the impurity removal step may be further processed to recover valuable metals such as cobalt, copper and zinc by processes such as precipitation, ion exchange, solvent extraction, etc.

[0009] Alternative bases may be used for pH adjustment in conjunction with solvent extraction. For example, Jayasekera, S., Donegan S., Harrison, T., Molnar, R., Robart, M., “Clean TeQ Sunrise Project -A Novel Hydrometallurgical Flowsheet to Produce Battery-Grade Cobalt and Nickel Sulfates”, Proceedings of Extraction 2018, Metallurgical Society of CIM (Montreal), describe the use of ammonia for pH adjustment. In the process described therein, the feed to the solvent extraction process was an Fe-AI-Cr free solution produced from resin-in-pulp elution and lime neutralization. Following eluate neutralization with lime (to precipitate Fe, Al, Cr, Cu), impurity solvent exchange (SX) was conducted with D2EHPA (to extract Zn, Ca, Mn, Cu), impurity SX was followed by cobalt SX with Cyanex 272 (to extract Co for crystallisation), followed by Nickel SX with Versatic 10 (to extract Ni for crystallisation). A solution of 30% NH3 as NH4OH was used for initial pH adjustment to facilitate extraction. The use of ammonia for pH adjustment resulted in the generation of ammonium sulfate solution after nickel recovery. The ammonium sulfate solution was crystallized to form an ammonium sulfate solid product for sale.

[0010] There remains a need for alternative process for hydrometallurgical treatment of MHP materials.SUMMARY

[0011] Processes are provided for treating a sulphate-containing acidic releached MHP solution, comprising: at least one step of solvent extraction in a solvent extraction solution comprising an aqueous phase and an organic phase, the step of solvent extraction comprising addition of a pH-adjusting ammonia, thereby adjusting pH of the aqueous phase to facilitate a selective extraction of at least one metal value into the organic phase from the aqueous phase, the selective extraction of the metal value from the aqueous phase leaving a pH-adjusted ammonium-sulphate-containing solution; and, recovering ammonia from the pH-adjusted ammonium-sulphate- containing solution by heating the pH-adjusted ammonium-sulphate- containing solution with addition of lime or magnesia, to produce an ammonia off gas and a solid calcium or magnesium sulphate product; and, recycling the ammonia off gas to produce at least some of the pH- adjusting ammonia.

[0012] The steps of solvent extraction may include an initial step of impurity solvent extraction comprising extracting the aqueous phase with a di-(2-ethylhexyl) phosphate (D2EHPA) organic phase, to selectively extract one or more of Ca / Cu / Zn / Mn / Co from nickel into a loaded D2EHPA organic phase leaving a D2EHPA-extracted aqueous phase. The initial step of impurity solvent extraction comprising the D2EHPA organic phase may for example be carried out at: an initial D2EHPA extraction pH of 3.1-3.7, and an initial D2EHPA extraction temperature of 25°-60°C; and, may include at least 3 extraction stages, and / or at least one D2EHPA scrub stage (wherein the loaded D2EHPA organic phase is scrubbed to preferentially scrub cobalt and nickel from the loaded D2EHPA organic phase into an aqueous D2EHPA scrub raffinate). The loaded D2EHPA organic phase may for example be stripped with an aqueous HCI stripping solution, for example at pH 2.4-2.8 in one or more D2EHPA stripping stages, to strip one or more of Ca / Cu / Zn / Mn / Co from the loaded D2EHPA organic phase.

[0013] The solvent extraction steps may further include an additional step of impurity solvent extraction comprising extracting the D2EHPA-extracted aqueous phase with a Cyanex 801 (2-ethylhexyl 2-ethylhexyl phosphonic acid) or Cyanex 272 (bis (2,4,4-trimethylpentyl) phosphinic acid) organic phase, to selectively extract one or more of Co / Cu / Zn from nickel into a loaded Cyanex organic phase leaving a Cyanex-extracted aqueous phase. The Cyanex 801 or 272 organic phase extraction may for example be carried out at: a Cyanex extraction pH of 4.8-5.5, and a Cyanex extraction temperature of a about 50°C.

[0014] The solvent extraction steps may further include a selective step of nickel solvent extraction comprising extracting the Cyanex-extracted aqueous phase with a neodecanoic acid (e.g. Versatic 10) organic phase, to selectively extract nickel into a loaded neodecanoic acid organic phase leaving a neodecanoic-acid - extracted aqueous phase.

[0015] Alternatively the solvent extraction steps may further include a selective step of nickel solvent extraction comprising extracting the Cyanex-extracted aqueous phase with a 2-hydroxyl-5-nonyl-acetophenone oxime (e.g. LIX 84) organic phase, to selectively extract nickel into a loaded LIX 84 organic phase leaving a LIX 84-extracted aqueous phase. Nickel may be stripped from the loaded LIX 84 organic phase with an ammonia-ammonium carbonate solution to form a nickel-ammine-carbonate solution, and the ammonia-ammonium carbonate solution may be steam stripped to precipitate basic nickel carbonate and recover ammonia.

[0016] In alternative embodiments, nickel may be stripped from the loaded organic phase with a nitric acid stripping solution to produce a nickel nitrate solution.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a graph showing ammonia volatlization with MgO addition at

[0018] Figure 2 is a flow sheet illustrating a process for MHP refining to make nickel sulfate with lime boil for ammonia recycle.

[0019] Figure 3 is a flow sheet illustrating a process for MHP refining to make nickel sulfate with magnesia boil for ammonia recycle.

[0020] Figure 4 is a flow sheet illustrating a process for MHP refining to make basic nickel carbonate with lime boil for ammonia recycle.

[0021] Figure 5 is a flow sheet illustrating a process for MHP refining to make basic nickel carbonate with magnesia boil for ammonia recycle.

[0022] Figure 6 is a line graph illustrating the conditions for extraction and stripping of nickel, copper and zinc from ammonia solution by LIX 84.DETAILED DESCRIPTION

[0023] MHP is a mixed nickel / cobalt hydroxide product. MHP can for example be produced from the leaching of laterite or sulphide ores, or of sulphide concentrates, or of alloys, by heap leaching, atmospheric tank or vat leaching, or by various pressure leaching processes. Alternative embodiments of the present processes may be applied to a wide range of such MHP materials.

[0024] MHP typically comprises a number of nickel and cobalt hydroxides. For example in a sulfate system nickel and cobalt hydroxy sulfates may form (Ni5(OH)sSO4 and Co5(OH)sSO4). MHP may also contain chloride or other anions as part of the nickel and cobalt precipitate and a number of metallic impurities. MHP typically has a cobalt content of about 1 % to 6%, a nickel content of about 25% to 55%, a manganese content of about 0.2 % to 5%, a calcium content of about 0.1% to 10% (depending for example on whether lime is used as the precipitant in the preparation of MHP), an iron content of 0.1% to 3%, an copper content of 0.01% to 0.5%, an zinc content of 0.1% to 2%, an aluminum content of 0.1% to 3%, an chromium content of 0.01% to 0.5%. Other impurities such as uranium, cadmium and silicon may also be present.

[0025] The present innovations are based in part on the recognition of two major problems associated with existing MHP refining practices using sodium- or ammonia- based pH adjustment strategies in solvent extraction.

[0026] First, in the case of solvent extraction pH adjustment with a sodium base, the final solution after nickel solvent extraction contains a high concentration of soluble sodium sulfate. Sodium sulfate may be crystallized and sold in certain markets but the value is generally very low and oversupplied. Disposal of sodium sulfate into receiving water ways is not normally allowed. The cost of NaOH (for example) for this duty may be relatively high and consequently can make MHP refining expensive.

[0027] The challenges associated with using a sodium base may be addressed with the use of ammonia for pH adjustment. However, in the case of solvent extraction pH adjustment with ammonia, the final solution containing ammonium sulfate will contain residual salts such as various chlorides from the MHP redissolution step. MHP often contains small amounts of chloride and chloride will concentrate in ammonium sulfate crystallization, resulting in potential contamination of ammonium sulfate and enhanced corrosion concerns in the crystallizer operation. In addition, the cost of ammonia to make ammonium sulfate by this method can be relatively high and can consequently make MHP refining expensive.

[0028] Processes are accordingly disclosed herein that facilitate the use of ammonia for solvent extraction pH adjustment, while avoiding the production of an ammonium sulfate by-product that may be contaminated with chloride. The present processes allow for the recycling of ammonia for pH adjustment, thereby ameliorating the cost of ammonia as a consumable base in the treatment of MHP by solvent extraction.

[0029] To avoid the production of an ammonium sulfate byproduct with contamination by chloride or other species, the final barren ammonium sulfate solution may be treated by either a lime boil or magnesia boil process. The lime boil process, as illustrated in Figure 2, uses calcium oxide or hydroxide and high temperatures to form gypsum and ammonia gas, with the ammonia then available for recycle by scrubbing and re-use as a base for pH adjustment in solvent extraction.Lime Boil(NH4)2SO4 + Ca(OH)2= 2NH3(g) + CaSO4.2H2O(solid)Table t Lime Boil Conditions*Note boiling point will vary with salt content of the solution and altitude.

[0030] The use of a lime boil allows for recovery of the valuable ammonia from ammonium sulfate and produces a solid product (gypsum) from the ammonium sulfate solution. In addition, any chloride salts present will remain in solution in the final effluent from the lime boil and will not interfere with ammonia recovery. It is an advantage of this process that the cost of MHP refining is lowered due to the recycle and re-use of ammonia and the substitution of lime or hydrated lime as the effective alkali for refining.

[0031] In alternative embodiments, as illustrated in Figure 3, a magnesia boil process may be used, for example where an excess of magnesium hydroxide is available.Magnesia Boil(NH4)2SO4 + Mg(OH)2= 2NH3(g) + MgSC + 2H2OTable 2. Magnesia Boil Conditions

[0032] The use of magnesia to regenerate and recycle ammonia forms a magnesium sulfate solution as a byproduct. In select embodiments, an advantage of the use of magnesia over lime is to reduce the potential for scaling of reactors, as magnesium sulfate is highly soluble.

[0033] As illustrated in Figure 2 and Figure 3, nickel may be solvent extracted prior to lime or magnesia boils, for example using a Versatic 10 solvent extractant (Shell Chemicals). Versatic 10 is a synthetic trialkyl acetic acid consisting of a mixture of highly branched isomers of C10 monocarboxylic acids (neodecanoic acids) obtained by the carboxylation of propylene trimer undergoing a Koch reaction. Similar carboxylic acid extractants may be available as Neo Acids (Exxon), and CeKanoic Acids (Kuhlmann). Versatic 10 selectivity is very pH- dependent, with pHi / 2 for Ni2+at pH 6.34 (the pH in an aqueous phase at which the metal ion distribution ratio is unity at equilibrium). Nickel may be recovered from the extractant with a sulfuric acid pH adjustment, to yield nickel sulfate for crystallization.

[0034] In alternative embodiments, as illustrated in Figure 4 and Figure 5, a LIX 84 solvent extractant may be used for nickel recovery from the purified solution.LIX 84 is 2-hydroxyl-5-nonyl-acetophenone oxime. Nickel is extracted as the oxime complex and then stripped using an excess of ammonia in an ammonium carbonate solution. The loading and stripping of nickel with LIX 84 may accordingly be mediated with an ammonia cycle: higher ammonia concentrations strip nickel and lower ammonia concentrations load nickel, with conditions as summarized in Table 3 based on the LIX 84 characteristics illustrated in Figure 6.Nickel Loading (HR(org) refers to the LIX 84 species).NiSC + 2HR(org) + 2NH3= NiR2(org) + (NH^SC

[0035] Nickel may be stripped using ammonia-ammonium carbonate solution to form a nickel-ammine-carbonate solution. The strip solution may be steam stripped to precipitate basic nickel carbonate (BNC) with recovery of ammonia and excess carbonate.Nickel StrippingNiR2(org) + 4NH3+ (NH4)2CO3= 2HR(org) + Ni(NH3)6CO3

[0036] The steam stripping produces the basic nickel carbonate product: 2Ni(NH3)6CO3+ H2O = Ni2(OH)2(CO3) + 12NH3(g) + CO2(g)

[0037] The ammonia and carbon dioxide may be recovered and recycled. The basic nickel carbonate may be produced as a high purity product, suitable forexample for direct incorporation as a solid in cathode active materials (Pcam) formulation, for example replacing the use of nickel metal in processes that involve mixing metal-containing powders to form pCAM materials (with calcination).

[0038] In alternative embodiments, nickel may be stripped from the loaded VERSATIC acid or LIX 84 solvents with nitric acid rather than sulfuric acid. Stripping nickel with nitric acid forms a strong nickel nitrate solution:NiR2(org) + 2HNO3= Ni(NO3)2+ 2HR(org)

[0039] The resulting nickel nitrate salts may for example be used for preparing battery materials.

[0040] The conditions employed for solvent extraction may for example be as characterized in Table 3.Table 3: Solvent Extraction ConditionspH adjustment with: E = 30% NH3as NH4OH; Sc = 100 g / L H2SC>4 or HNO3or for LIX84 NH3-(NH4)2CO3.In which:E=Extraction i.e. the step of extracting the metal value into the organic phase, with basic pH adjustment with ammonia;Sc=stripping, with acid addition to the organic phase to recover metal values from the organic phase, for example with sulphuric, nitric (for Ni extraction) or hydrochloric (to avoid gypsum precipitate in initial impurity solvent extraction) acid. ISX = impurity solvent extractionCSX = cobalt solvent extractionNSX V10 = Versatic nickel solvent extractionNSX LIX84 = LIX84 nickel solvent extractionExample 1

[0041] A 1 mol / L ammonium sulfate solution was treated with an excess of Mg(OH)2 and heated to 95 °C for 6 hours. The resulting solution was analyzed for total nitrogen. The recovery of ammonia by volatilization is shown in the graph of Figure 1 as a function of time. The vertical scale is a logarithmic scale. Over 95% of the initial ammonia in solution was volatilized.Definitions and Citations

[0042] Although various embodiments of the invention are disclosed herein, many adaptations and modifications may be made within the scope of the invention in accordance with the common general knowledge of those skilled in this art. Such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way. Terms such as “exemplary” or “exemplified” are used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” or “exemplified” is accordingly not to be construed as necessarily preferred or advantageous over other implementations, all such implementations being independent embodiments. Unless otherwise stated, numeric ranges are inclusive of the numbers defining the range, and numbers are necessarily approximations to the given decimal. The word "comprising" is used herein as an open-ended term, substantially equivalent to the phrase "including, but not limited to", and the word "comprises" has a corresponding meaning. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a thing" includes more than one such thing. Citation of references herein is not an admission that such references are prior art to the present invention. Any priority document(s) and all publications, including but not limited to patents and patent applications, cited inthis specification, and all documents cited in such documents and publications, are hereby incorporated herein by reference as if each individual publication were specifically and individually indicated to be incorporated by reference herein and as though fully set forth herein. The invention includes all embodiments and variations substantially as hereinbefore described and with reference to the examples and drawings.

Claims

CLAIMS:

1. A process for treating a sulphate-containing acidic re-leached MHP solution, comprising: at least one step of solvent extraction in a solvent extraction solution comprising an aqueous phase and an organic phase, the step of solvent extraction comprising addition of a pH-adjusting ammonia, thereby adjusting pH of the aqueous phase to facilitate a selective extraction of at least one metal value into the organic phase from the aqueous phase, the selective extraction of the metal value from the aqueous phase leaving a pH-adjusted ammonium-sulphate-containing solution; and, recovering ammonia from the pH-adjusted ammonium-sulphate- containing solution by heating the pH-adjusted ammonium-sulphate- containing solution with addition of lime or magnesia, to produce an ammonia off gas and a solid calcium or magnesium sulphate product; and, recycling the ammonia off gas to produce at least some of the pH- adjusting ammonia.

2. The process of claim 1 , wherein the at least one step of solvent extraction comprises an initial step of impurity solvent extraction comprising extracting the aqueous phase with a di-(2-ethylhexyl) phosphate (D2EHPA) organic phase, to selectively extract one or more of Ca / Cu / Zn / Mn / Co from nickel into a loaded D2EHPA organic phase leaving a D2EHPA-extracted aqueous phase.

3. The process of claim 2, wherein the initial step of impurity solvent extraction comprising the D2EHPA organic phase is carried out at: an initial D2EHPA extraction pH of 3.1-3.7, and an initial D2EHPA extraction temperature of 25°-60°C.

4. The process of claim 2 or 3, wherein the initial step of impurity solvent extraction comprising the D2EHPA organic phase comprises at least 3 extraction stages.

5. The process of any one of claims 2 to 4, comprising at least one D2EHPA scrub stage wherein the loaded D2EHPA organic phase is scrubbed to preferentially scrub cobalt and nickel from the loaded D2EHPA organic phase into an aqueous D2EHPA scrub raffinate.

6. The process of any one of claim 2 to 5, further comprising stripping the loaded D2EHPA organic phase with an aqueous HCI stripping solution at pH 2.4-2.8 in a D2EHPA stripping stage, to strip one or more of Ca / Cu / Zn / Mn / Co from the loaded D2EHPA organic phase.

7. The process of claim 6, further comprising least 2 D2EHPA stripping stages.

8. The process of any one of claims 2 to 7, wherein the initial step of impurity solvent extraction comprises one or more reactions represented by:CaSC>4 + 2HR(org) + 2NaOH = CaR2(org) + Na2SC>4 + 2H2O;CuSC>4 + 2HR(org) + 2NaOH = CuR2(org) + Na2SC>4 + 2H2O;ZnSC + 2HR(org) + 2NaOH = ZnR2(org) + Na2SO4+ 2H2O;MnSC + 2HR(org) + 2NaOH = MnR2(org) + Na2SO4+ 2H2O;CoSO4 + 2HR(org) + 2NaOH = CoR2(org) + Na2SC>4 + 2H2O; Fe2(SO4)3+ 6HR(org) + 6NaOH = 2FeR3(org) + 3Na2SO4+ 6H2O;AI2(SO4)3 + 6HR(org) + 6NaOH = 2AIR3(org) + 3Na2SO4+ 6H2O; and / or,Cr2(SO4)3+ 6HR(org) + 6NaOH = 2CrR3(org) + 3Na2SO4+ 6H2O; wherein HR(org) represents D2EHPA.

9. The process of any one of claims 2 to 8, wherein the at least one step of solvent extraction further comprises an additional step of impurity solvent extraction comprising extracting the D2EHPA-extracted aqueous phase with a Cyanex 801 (2-ethylhexyl 2-ethylhexyl phosphonic acid) or Cyanex 272 (bis (2,4,4-trimethylpentyl) phosphinic acid) organic phase, to selectively extract one or more of Co / Cu / Zn from nickel into a loaded Cyanex organic phase leaving a Cyanex-extracted aqueous phase.

10. The process of claim 9, wherein the additional step of impurity solvent extraction comprising the Cyanex 801 or 272 organic phase is carried out at: a Cyanex extraction pH of 4.8-5.5, and a Cyanex extraction temperature of a about 50°C.

11. The process of claim 9 or 10, wherein the at least one step of solvent extraction further comprises a selective step of nickel solvent extraction comprising extracting the Cyanex-extracted aqueous phase with a neodecanoic acid organic phase, to selectively extract nickel into a loaded neodecanoic acid organic phase leaving a neodecanoic-acid -extracted aqueous phase.

12. The process of claim 11 , wherein the neodecanoic acid is Versatic 10.

13. The process of claim 9 or 10, wherein the at least one step of solvent extraction further comprises a selective step of nickel solvent extraction comprising extracting the Cyanex-extracted aqueous phase with a 2-hydroxyl- 5-nonyl-acetophenone oxime (LIX 84) organic phase, to selectively extract nickel into a loaded LIX 84 organic phase leaving a LIX 84-extracted aqueous phase.

14. The process of claim 13, further comprising stripping nickel from the loaded LIX 84 organic phase with an ammonia-ammonium carbonate solution to form a nickel-ammine-carbonate solution.

15. The process of claim 14, further comprising steam stripping the ammonia-ammonium carbonate solution to precipitate basic nickel carbonate and recover ammonia.

16. The process of any one of claims 11 to 13, further comprising stripping nickel from the loaded organic phase with a nitric acid stripping solution to produce a nickel nitrate solution.

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