PURIFIED NICKEL SOLUTIONS USING SUCCESSIVE SOLVENT EXTRACTIONS

Abstract

Methods of recovering a nickel salt are disclosed. The method includes removing one or more impurities from an aqueous leach solution including cobalt, manganese, and nickel salts to produce a first purified aqueous solution including the cobalt, manganese, and nickel salts. The method includes extracting the cobalt and manganese salts from the first purified aqueous solution in a first liquid-liquid extraction step using a first organic extractant to produce an aqueous raffinate solution including the nickel salt and a first loaded organic solution including the cobalt and manganese salts. The method further includes extracting the nickel salt from the aqueous raffinate solution in a second liquid-liquid extraction step using a second organic extractant to produce a second loaded organic solution including the nickel salt. Systems for recovering a nickel salt are also disclosed.

Claims

1. A method of recovering a nickel salt, comprising: removing one or more impurities from an aqueous leach solution comprising cobalt, manganese, and nickel salts to produce a first purified aqueous solution comprising the cobalt, manganese, and nickel salts; extracting the cobalt and manganese salts from the first purified aqueous solution in a first liquid-liquid extraction step using a first organic extractant to produce an aqueous raffinate solution comprising the nickel salt and a first loaded organic solution comprising the cobalt and manganese salts; and extracting the nickel salt from the aqueous raffinate solution in a second liquid-liquid extraction step using a second organic extractant to produce a second loaded organic solution comprising the nickel salt.

2. The method of claim 1, wherein the aqueous leach solution is prepared by leaching metal salts from a granular mass of crushed battery materials including cathode materials and anode materials.

3. The method of claim 1, wherein removing the one or more impurities from the leach solution comprises precipitation by pH adjustment.

4. The method of claim 1, wherein the first organic extractant comprises a dialkylphosphinic acid.

5. The method of claim 4, wherein the dialkylphosphinic acid is dissolved in an organic diluent to a concentration of about 10% to about 20%.

6. The method of claim 1, wherein, during the first liquid-liquid extraction step, the first purified aqueous solution has an equilibrium pH of less than 7.

7. The method of claim 6, wherein the equilibrium pH is from about 4 and about 6.

8. The method of claim 6, wherein the equilibrium pH is achieved by increasing the pH of the first purified aqueous solution using a water-soluble base.

9. The method of claim 6, wherein the first organic extractant comprises a dialkylphosphinic acid and wherein the equilibrium pH is achieved by saponification of the dialkylphosphinic acid.

10. The method of claim 9, wherein a water-soluble base achieves a degree of saponification of the dialkylphosphinic acid of 30-35%.

11. The method of claim 1, wherein the first liquid-liquid extraction step occurs at a temperature of from about 40 C. to about 60 C.

12. The method of claim 1, wherein the second organic extractant comprises an alkylcarboxylic acid.

13. The method of claim 12, wherein the alkylcarboxylic acid is dissolved in an organic diluent to a concentration of about 30% to about 50%.

14. The method of claim 1, wherein, during the second liquid-liquid extraction step, the aqueous raffinate solution has an equilibrium pH of less than 7.

15. The method of claim 14, wherein the equilibrium pH is from about 5 to about 6.

16. The method of claim 15, wherein the equilibrium pH is achieved by increasing the pH of the aqueous raffinate solution using a water-soluble base.

17. The method of claim 15, wherein the second organic extractant comprises an alkylcarboxylic acid and wherein the equilibrium pH is achieved by saponification of the alkylcarboxylic acid.

18. The method of claim 17, wherein a water-soluble base achieves a degree of saponification of the alkylcarboxylic acid of 25-35%.

19. The method of claim 1, further comprising performing a third extraction step on the first loaded organic solution to produce an enriched cobalt and manganese salt solution and a first waste solution comprising spent first organic extractant.

20. The method of claim 19, further comprising regenerating the spent first organic extractant with a first acidic regenerant.

21. The method of claim 1, further comprising a fourth extraction step on the second loaded organic solution to produce a second purified aqueous solution comprising the nickel salt and a second waste solution comprising spent second organic extractant.

22. The method of claim 21, further comprising regenerating the second spent organic extractant with a second acidic regenerant.

23. The method of claim 21, further comprising recovering the nickel salt from the second purified aqueous solution.

24. The method of claim 21, wherein the nickel salt is recovered from the second purified aqueous solution by crystallization.

25. A system for recovering a nickel salt, comprising: an impurity removal stage constructed and arranged to remove one or more impurities from an aqueous leach solution comprising cobalt, manganese, and nickel salts to produce a first purified aqueous solution comprising the cobalt, manganese, and nickel salts; a first extraction stage constructed and arranged to remove the cobalt and manganese salts from the first purified aqueous solution to produce an aqueous raffinate solution comprising the nickel salt and a first loaded organic solution comprising the cobalt and manganese salts; and a second extraction stage constructed and arranged to remove the nickel salt from the aqueous raffinate solution to produce a second loaded organic solution comprising the nickel salt.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The foregoing and other features will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0006] FIG. 1 illustrates a flow chart of a method for the recovery of a nickel salt, in accordance with an embodiment disclosed herein;

[0007] FIG. 2 illustrates the selectivity of metal salts in a first organic extractant comprising a dialkylphosphinic acid as a function of equilibrium pH;

[0008] FIG. 3 illustrates the selectivity of metal salts in a second organic extractant comprising an alkylcarboxylic acid as a function of equilibrium pH;

[0009] FIG. 4 illustrates the effect of equilibrium pH on the metal selectivity function of 15 vol. % CYANEX 272 at 50 C.;

[0010] FIG. 5 illustrates the effect of the concentration of CYANEX 272 in an extractant solution on the extraction efficiency of NMC at room temperature and pH 5;

[0011] FIG. 6 illustrates the effect of the concentration of VERSATIC Acid 10 solution on the extraction efficiency of NMC at room temperature and pH 6.5;

[0012] FIG. 7 illustrates the effects of the concentration of CYANEX 272, feed dilution, and temperature on CYANEX 272 function in NMC extraction;

[0013] FIG. 8 illustrates the effects of temperature on the NMC extraction efficiency using an organic extractant including 15 vol. % CYANEX 272 at pH 5-5.5;

[0014] FIG. 9 illustrates the effects of temperature on metal extraction using 40 vol. % VERSATIC Acid 10 at pH 5.6 and O/A=1:1; and

[0015] FIG. 10 illustrates a comparison of the final product purities from five separate extraction experiments.

DETAILED DESCRIPTION

[0016] This disclosure is directed to systems and methods for the recovery of nickel salts, e.g., from a nickel-containing, e.g., a nickel-rich, cathode material in a recycling stream of end-of-life batteries. Lithium-ion batteries contain valuable precious metals which would go to waste when the batteries are spent and discarded. With the rising use of lithium-ion batteries, the recovery of precious metals from spent lithium-ion batteries has become an important industry.

[0017] Typically, end-of-life lithium-ion batteries are dismantled, crushed, or shredded to form a granular mass of battery materials (including cathode materials, anode materials, current collectors, electrolytes, etc.), often referred to as black mass which is used for further recycling. Current lithium-ion battery recycling efforts are primarily focused on recovering the base metals cobalt and lithium from lithium cobalt oxide cathodes. However, there are many other types of cathode materials used in lithium-ion batteries. A significant portion of these cathode materials include other base metals such as nickel and manganese. Conventional recycling methods do not adequately handle the recycling of different types of lithium-ion battery cathode materials and fail to sufficiently address the extraction of these other metals. Many existing recovery processes have numerous extraction, scrubbing, and stripping stages, increasing costs and time to produce suitable materials for battery production.

[0018] Further, black mass, especially those derived collectively from different types of lithium-ion batteries, contains many types of impurities. Failing to effectively remove them adversely affects the purity of metals recovered from recycling. Present efforts of impurity removal involve numerous steps requiring many reactors and filters. Not only does this lengthen the entire recycling process and increases costs, but with each reactor or filter, valuable material is lost, resulting in a severe reduction in the amount of base metals available for recovery.

[0019] Thus, there exists a need for a lithium-ion battery recycling process which can better handle the removal of impurities in black mass, especially that derived collectively from different types of lithium-ion batteries. There also exists an associated need to remove impurities in a more efficient way that requires less equipment and results in less reduction in the amount of base metals available for recovery.

[0020] Depicted herein is an example method and approach for recycling batteries containing, inter alia, nickel, manganese, and cobalt. Lithium-ion batteries have been used for many applications and are becoming more and more important for electronic devices, electric vehicles, and energy storage systems. High nickel ternary or quaternary batteries are gathering more attention due the higher energy capacity and lower raw materials cost. The high nickel batteries often reach their end of life within 8-15 years, and they will comprise the bulk of spent lithium-ion batteries in the future. Front-end material recovery methods from black mass are becoming more important as a way to recycle spent batteries and as a source for battery cathode materials.

[0021] FIG. 1 is a flow diagram of an embodiment of a method for the recovery of a nickel salt, e.g., from an aqueous leach solution comprising cobalt, manganese, and nickel salts. With reference to FIG. 1, in a recovery method 100, leaching 102 is performed on black mass using an aqueous leach solution to separate the recoverable materials from the black mass. The aqueous leach solution is prepared by leaching metal salts from a granular black mass, such as crushed battery materials including cathode materials and anode materials. The leach solution may include an acid, such as sulfuric acid, hydrochloric acid, nitric acid, acetic acid, boric acid, oxalic acid, formic acid, or any other suitable organic or inorganic acid and may further include an optional oxidizing agent or reducing agent. In a specific embodiment, an acid such as sulfuric acid and water, optionally including hydrogen peroxide, and the black mass are combined to dissolve base metals present within the crushed battery materials into the aqueous phase.

[0022] The aqueous leach solution includes numerous impurities that can impact the recovery of metal salts of interest. To remove the impurities, removal step 104 occurs in which insoluble compounds of the impurities are formed using a pH adjustment of the aqueous leach solution. For example, an increase in the pH of the aqueous leach solution using a water-soluble base, such as NaOH, NH.sub.4OH, (NH.sub.4).sub.2CO.sub.3, or another water-soluble base, can facilitate precipitation of insoluble hydroxide compounds that can subsequently be removed, such as by filtration, to produce a first purified aqueous solution comprising the cobalt, manganese, and nickel salts. In some embodiments, a pH of the first purified aqueous solution is acidic, e.g., a pH of from about 3 to 5.

[0023] With continued reference to FIG. 1, a method of recovering a nickel salt includes a first liquid-liquid extraction step 106 configured to extract the cobalt and manganese salts from the first purified aqueous solution. The first liquid-liquid extraction step 106 is a liquid-liquid extraction process using a liquid first organic extractant that is substantially immiscible with the aqueous leach solution. When the aqueous leach solution and the first organic extractant are combined, a first loaded organic solution including co-extracted cobalt and manganese salts is produced. The raffinate solution produced is an aqueous solution comprising the nickel salts.

[0024] Without wishing to be bound by any particular theory, organic extractants useful for liquid-liquid extractions disclosed herein are those having functionalities with affinity for the metal salts in the aqueous phase and with high selectivity for specific metal ions. For example, the extraction of Co and Ni from aqueous sulfate solutions has been achieved with organophosphorus compounds such as di(2-ethylhexyl)phosphoric acid (D2EHPA). In order to increase selectivity for cobalt and manganese salts while leaving the nickel salts in solution, the first organic extractant may include a dialkylphosphinic acid, e.g., R.sub.1R.sub.2PO.sub.2H where R.sub.1 and R.sub.2 are alkyl groups. As a non-limiting example, the first organic extractant may include bis(2,2,4 trimethylpentyl)phosphinic acid, i.e., CYANEX 272. When used as part of the first organic extractant, the dialkylphosphinic acid may be present in a concentration of about 10% to about 20% w/w or v/v in a solution. The balance of the first organic extractant may include an organic diluent or one or more diluents in which the dialkylphosphinic acid is soluble. For example, a paraffinic diluent, such as Shell GTL solvent, may be used.

[0025] As illustrated in FIG. 2, the selectivity of various metal salts in a solution of a first organic extractant comprising a dialkylphosphinic acid is a function of the equilibrium pH of the extraction solution. In FIG. 2, cobalt and manganese salts can be co-extracted within a narrow pH window, with nickel salts being extracted at a higher pH. In some embodiments, during the first liquid-liquid extraction step, the first purified aqueous solution has an equilibrium pH of less than 7, and, in specific embodiments, a pH of greater than 0, such as greater than 2. For example, the equilibrium pH during the first liquid-liquid extraction step is preferably from about 4 to about 6, such as from about 4.5 to about 5.5. In a specific example, the equilibrium pH during the first liquid-liquid extraction step is about 5.5. Other specific ranges could be determined by one of ordinary skill in the art in view of the information illustrated in FIG. 2.

[0026] As disclosed herein, the pH of the first purified aqueous solution following removal of impurities, e.g., via precipitation, is acidic. To increase the pH of the first purified aqueous solution to achieve the equilibrium pH during the first liquid-liquid extraction step, a basic pH adjusting compound can be added to the first purified aqueous solution. The pH adjusting compound can be a water-soluble base, such as NaOH, NH.sub.4OH, (NH.sub.4).sub.2CO.sub.3, or another water-soluble base. In some embodiments, a water-soluble acid, such as a weak acid or a dilute acid, may also be used, depending on the pH of the first purified aqueous solution.

[0027] In some embodiments, when the first organic extractant includes a dialkylphosphinic acid, the equilibrium pH for the first liquid-liquid extraction step can be achieved by saponification of the dialkylphosphinic acid. Saponification is an alkaline neutralization process in which an extractant is converted from an acid form to its salt form. As it pertains to the present disclosure, the saponification of the dialkylphosphinic acid using a water-soluble base causes the acidity of the aqueous phase to decrease, i.e., the equilibrium pH increases during extraction of the metals from the aqueous phase. This change in pH increases the total metal extraction and typically increases selectivity for specific metal salts of interest.

[0028] As a specific example, the saponification degree (S %) and the volume of the water-soluble base (NaOH) to be added to arrive at the target degree of saponification of the first organic extractant (di-(2-ethylhexyl) phosphoric acid, D2EHPA) can be obtained through Eq. 1 and Eq. 2, respectively:

[00001]$\begin{array}{cc}S\%=\frac{n_{\mathrm{Saponifier}}\left(\mathrm{mol}\right)}{n_{\mathrm{Extractant}}\left(\mathrm{mol}\right)}100\%=\frac{C_{NaOH}\left(\frac{\mathrm{mol}}{L}\right)V_{NaOH}\left(L\right)}{C_{D2\mathrm{EHPA}}\left(\frac{\mathrm{mol}}{L}\right)V_{D2\mathrm{EHPA}}\left(L\right)}100\%& \mathrm{Eq}.1\end{array}$$\begin{array}{cc}{V}_{S\mathrm{aponifier}}\left(L\right)=\frac{S\%n_{\mathrm{Extractant}}\left(\mathrm{mol}\right)}{C_{\mathrm{Saponifier}}\left(\frac{\mathrm{mol}}{L}\right)}& \mathrm{Eq}.2\end{array}$

where n.sub.Saponifier and n.sub.Extractant, are the initial moles of the water-soluble base and first organic extractant, respectively and C.sub.Saponifier is the concentration of the water-soluble base. The percent extraction efficiency (E %) is given by Eq. 3:

[00002]$\begin{array}{cc}E\%=\frac{{\left[C\right]}_{i,aq}{V}_i-{\left[C\right]}_{f,\mathrm{aq}}{V}_f}{{\left[C\right]}_{i,aq}{V}_i}100& \mathrm{Eq}.3\end{array}$

where [C].sub.i,aq, [C].sub.f,aq, V.sub.i and V.sub.f indicate the initial and final concentrations of metal ions in the aqueous phase and initial and final aqueous volume, respectively. The stripping efficiency (SE %) is determined from Eq. 4:

[00003]$\begin{array}{cc}\mathrm{SE}\%=\frac{{\left[C\right]}_{LSL}{V}_{LSL}}{{\left[C\right]}_{org}{V}_{org}}100& \mathrm{Eq}.4\end{array}$

where [C].sub.LSL, [C].sub.org are the concentrations of metal ions in the stripped liquor and organic phase respectively, whereas the V.sub.LSL and V.sub.org are the volumes of the stripped liquor and organic phase, respectively.

[0029] As a non-limiting example, the water-soluble base, e.g., NaOH, NH.sub.4OH, (NH.sub.4).sub.2CO.sub.3, or another water-soluble base, alone or in combination, can achieve a degree of saponification of the dialkylphosphinic acid of about 30-35%. To achieve this level of saponification of the dialkylphosphinic acid in the first organic extractant, the concentration of the water-soluble base can be, for example, about 50% w/w. Once the target degree of saponification of the dialkylphosphinic acid with the addition of the water-soluble base is achieved, the saponified dialkylphosphinic acid and the first purified aqueous solution can be combined in a fixed ratio of organic to aqueous phases, i.e., O:A ratio, to begin the first liquid-liquid extraction step. The specific ratio will depend on the concentration and type of metals to be extracted. Example O:A ratios include from about 1:1 to about 3:1, such as 2:1.

[0030] In addition to the pH, the concentration of the first organic extractant, the O:A ratio, and the degree of saponification of the first organic extractant, the efficiency of the first liquid-liquid extraction step can also be a function of the temperature. In some embodiments, the first liquid-liquid extraction step is performed at a temperature from about 40 C. to about 60 C. In certain embodiments, the first liquid-liquid extraction step is performed at a temperature of about 50 C.

[0031] With continued reference to FIG. 1, first liquid-liquid extraction step 106 produces an aqueous raffinate solution comprising the nickel salt and a first loaded organic solution comprising the cobalt and manganese salts. The metal salts in each of these solutions can be recovered using a series of extraction steps. For example, as disclosed herein, the aqueous raffinate solution is used as a feed solution for a second liquid-liquid extraction step 108 using a second organic extractant. The second organic extractant includes an alkylcarboxylic acid, e.g., iso-carboxylic acids, neo-carboxylic acids, sec-carboxylic acids, and tert-carboxylic acids. As a non-limiting example, the second organic extractant may include neo-decanoic acid, i.e., VERSATIC acid 10. As it pertains to the present disclosure, when used as part of the second organic extractant, the alkylcarboxylic acid may be present in a concentration of about 30% to about 50% w/w or v/v in solution. The balance of the second organic extractant may include an organic diluent or one or more diluents in which the alkylcarboxylic acid is soluble. For example, a paraffinic diluent may be used.

[0032] As illustrated in FIG. 3, the selectivity of various metal salts in a solution of a second organic extractant comprising an alkylcarboxylic acid is a function of the equilibrium pH of the extraction solution. In FIG. 3, nickel salts can be extracted within a pH window that is lower than and distinct from the cobalt and manganese salts. In some embodiments, during the second liquid-liquid extraction step, the aqueous raffinate solution has an equilibrium pH of less than 7 and, in specific embodiments, a pH of greater than 0, such as greater than 2. For example, the equilibrium pH during the second liquid-liquid extraction step is preferably from about 4.5 to about 6.5, such as from about 5 to about 6 in certain embodiments. In a specific example, the equilibrium pH during the second liquid-liquid extraction step is about 5.6. As discussed above, if necessary, to increase the pH of the aqueous raffinate solution to achieve the equilibrium pH during the second liquid-liquid extraction step, a basic pH adjusting compound or an adjusting compound that has an acidic pH close to neutral can be added to the aqueous raffinate solution. For example, the pH adjusting compound can be a water-soluble base, such as NaOH, NH.sub.4OH, (NH.sub.4).sub.2CO.sub.3, or another water-soluble base.

[0033] In some embodiments, when the second organic extractant includes an alkylcarboxylic acid, the equilibrium pH for the second liquid-liquid extraction step can be achieved by saponification of the alkylcarboxylic acid. As a non-limiting example, the water-soluble base, e.g., NaOH, NH.sub.4OH, (NH.sub.4).sub.2CO.sub.3, or another water-soluble base, alone or in combination, can achieve a degree of saponification of the alkylcarboxylic acid of about 25-35% as calculated using the formalism of Eqs. 1-4 disclosed herein. To achieve this level of saponification of the alkylcarboxylic acid in the second organic extractant, the concentration of the water-soluble base can be, for example, about 50% w/w. Once the target degree of saponification of the alkylcarboxylic acid with the addition of the water-soluble base is achieved, the saponified alkylcarboxylic acid and the aqueous raffinate solution can be combined in a fixed ratio of organic to aqueous, i.e., O:A ratio, to begin the second liquid-liquid extraction step. The specific ratio will depend on the concentration and type of metals to be extracted. Example O:A ratios include from about 1:1 to about 3:1, such as 2:1.

[0034] The first loaded organic solution comprising the cobalt and manganese salts that results from the first liquid-liquid extraction step 106 may be further processed in a third liquid-liquid extraction step 109 to produce an enriched cobalt and manganese salt solution and a first waste solution comprising spent first organic extractant. This step is referred to as a stripping or scrubbing step in which the metal salts in the organic phase are removed and transferred to an aqueous phase. For example, the third liquid-liquid extraction step is performed by using an acidic stripping solution, e.g., an aqueous solution of sulfuric acid, e.g., 2 M sulfuric acid, to transfer the cobalt and manganese salt back into the aqueous phase. The enriched aqueous cobalt and manganese salt solution can be further processed to produce purified cobalt salts and manganese salts for industrial purposes or other relevant uses requiring purified cobalt salts and manganese salts. The first waste solution comprising the spent first organic extractant can be further processed in a first regeneration step 111 to recover the first organic extractant such that it can be reused in the first extraction step 106. The first regeneration step 111 uses a first acidic regenerant solution, e.g., an aqueous solution of sulfuric acid, e.g., 5 M sulfuric acid, to remove any residual metal salts from active sites in the first organic extractant. Following regeneration of the first organic extractant, the regenerated first organic extractant can be washed to remove the first acidic regenerant solution, and the pH of the regenerated first organic extractant can be adjusted.

[0035] With continued reference to FIG. 1, the second loaded organic solution comprising the nickel salt from the second extraction step 108 can optionally be scrubbed using a nickel solution, such as an aqueous nickel sulfate solution, at step 110. This optional scrubbing would be used to remove any residual impurities in the aqueous and organic phases that result from the second extraction step 108. The second loaded organic solution produced from the second extraction step 108 can have the nickel extracted/scrubbed/stripped in a fourth extraction step 112 to produce a second purified aqueous solution comprising the nickel salt and a second waste solution, i.e., a recycled organic solution, comprising spent second organic extractant. The second waste solution comprising the spent second organic extractant can be further processed in a second regeneration step 113 to recover the second organic extractant such that it can be used in the second extraction step 108. For example, the second regeneration step 113 uses a first acidic regenerant solution, e.g., an aqueous solution of sulfuric acid, e.g., 5 M sulfuric acid, to remove any residual metal salts from active sites in the second organic extractant.

[0036] The second purified aqueous solution comprising the nickel salt can be further processed in a nickel recovery step 114 to recover the nickel salt. The nickel can be removed from the second purified aqueous solution using any suitable recovery method. In one embodiment, the nickel in the second purified aqueous solution can be recovered by crystallization. The second purified aqueous solution can have the concentration of nickel increased to form a supersaturated solution, permitting crystal formation. Other methods of inducing crystallization, such as supercooling of the second purified aqueous solution, addition of seed crystals, evaporative crystallization, or fractional crystallization on the second purified aqueous solution, are within the scope of this disclosure. Alternatively, the second purified aqueous solution comprising the nickel salt may be used as is, such as a source of pure nickel salts for production of cathode active material precursors.

[0037] In accordance with an embodiment, there is provided a system for recovering a nickel salt. The system includes an impurity removal stage constructed and arranged to remove one or more impurities from an aqueous leach solution comprising cobalt, manganese, and nickel salts to produce a first purified aqueous solution comprising the cobalt, manganese, and nickel salts. The system further includes a first extraction stage constructed and arranged to remove the cobalt and manganese salts from the first purified aqueous solution to produce an aqueous raffinate solution comprising the nickel salt and a first loaded organic solution comprising the cobalt and manganese salts. The system additionally includes a second extraction stage constructed and arranged to remove the nickel salt from the aqueous raffinate solution to produce a second loaded organic solution comprising the nickel salt.

EXAMPLES

[0038] The function and advantages of these and other embodiments of this disclosure can be better understood from the following examples. These examples are intended to be illustrative in nature and are not considered to be in any way limiting of the scope of the invention.

Example 1pH Determination

[0039] In this example, experimental investigations to attain selective extraction of target metals with high recovery rates and minimal loss of other valuable metals by optimizing the pH of the extraction steps are described. The determination of an optimal pH for the various extraction steps was achieved through the creation of extraction isotherms. Here, an in vivo pH isotherm was developed utilizing post-impurity removal purified aqueous solution and an aqueous raffinate as sources for extraction with CYANEX 272 and VERSATIC Acid 10, respectively, aimed at mimicking real-world process conditions.

[0040] Extractions were performed in a pH range of 4.5 to 6.5 using 15 vol. % CYANEX 272 at 50 C., with the balance of the extraction solution being Shell GTL solvent, a diluent paraffinic solvent, and 50% NaOH. Table 1 shows the chemical composition of the feed solution for pH isotherm experiment.

TABLE-US-00001 TABLE 1 Chemical composition of post-impurity removal leachate from NMC811 BM feed solution for CYANEX 272 pH isotherm Metal Ni Mn Co Li Mg Cu Input feed (ppm) 46104.34 1571.014 5781.576 1445.255 385.7158 163.5817

[0041] As illustrated in FIG. 4, over the pH range examined, more than 90% of Cu was successfully extracted. It was observed that increasing the pH enhanced the extraction efficiency of all metals. However, the enhancement was negligible for Ni, which may be due to an insufficient number of active sites on CYANEX 272 for Ni extraction as well as competing Mg extraction. As further illustrated in FIG. 4, CYANEX 272 demonstrated efficient performance as an extractant for Mn and Co co-extraction. Specifically, at pH 5.5, approximately 99% of Mn and Cu, along with 95% of Co, were extracted. At this pH, the efficiency of Mg extraction was about 41.22%, accompanied by only about 5% loss of Ni by extraction. It was further observed that as the pH increased, the viscosity of the extractant solution increased, which increased the complexity of pH adjustment and equilibrium pH attainment. Taking into consideration these variables, a pH range for the first extraction step of from about 5 to 5.5 was identified as suitable as it facilitated efficient Mn and Co co-extraction with minimal Ni extraction while also minimizing operational challenges such as dense organic phase formation. This determination was consistent with pH isotherm studies conducted at both room temperature (25 C.) and 50 C.

[0042] For the selective extraction of Ni using VERSATIC Acid 10 while minimizing the extraction of Group 1 and 2 elements such as Na, Ca, Li, and Mg, the feed source used to develop this isotherm included a CYANEX 272 aqueous raffinate solution obtained from a known source. It was found that, at 50 C., the target pH for VERSATIC Acid 10 extraction, adjusted to 5.6 to accommodate the effects on increased solution temperature, was successful in preventing Mg co-extraction with the Ni.

Example 2Extractant Concentration

[0043] In this example, experimental investigations were performed to determine an optimal concentration of organic extractants for the selective removal of metal salts from solutions derived from leaching of black mass. The optimal extractant concentration aims to mitigate operational issues such as excessive water solubility and difficulties in pH adjustment while maintaining high target metal recovery and minimum cost. Experiments have been conducted at room temperature and different volume percentages of extractants: 10%, 15%, 20%, and 30%.

[0044] FIG. 5 illustrates the effect of the concentration of CYANEX 272 in the extractant solution on the recovery of nickel, manganese, and cobalt at room temperature and at a pH of 5.0. Table 2 shows the chemical composition of the aqueous acidic leach solution generated after impurity removal. Mg was not added to the leach solution.

TABLE-US-00002 TABLE 2 Chemical composition of post-impurity removal leachate from black mass used as the feed solution to explore effects of CYANEX 272 concentration Metal Ni Mn Co Li Input feed (ppm) 56056.84 3097.98 7490.18 8628.20

[0045] A comparison of Mn and Co recovery rates between 20 vol. % and 30 vol. % CYANEX 272 showed a minimal increase in Mn recovery and an approximately 15% increase in Co recovery. Considering that, in a counter-current circuit, the 15% increase in cobalt recovery can be offset, along with the associated increase in extractant cost, an extractant concentration of 15%-20% CYANEX 272 at a temperature of 50 C. was determined to best balance performance and operational considerations.

[0046] For the selective extraction of Ni using VERSATIC Acid 10, experiments were conducted with the extractant using an aqueous raffinate solution from known CYANEX 272 extractions as the source feed. Initially, concentration modulation tests were performed to determine extraction conditions. VERSATIC Acid 10 exhibited consistent behavior as an extractant. To identify the optimal concentration for VERSATIC Acid 10 extraction, a broader range of concentrations was tested compared to those used in the CYANEX 272 experiments described in this example. This broader concentration range was selected since VERSATIC Acid 10 extraction is less efficient at lower concentrations. FIG. 6 illustrates the impact of VERSATIC Acid 10 concentration on the extraction of nickel, manganese, and cobalt salts from an aqueous leach solution at room temperature and pH 6.5. Table 3 presents the chemical composition of the feed solution, which comprises the raffinate produced subsequent to the initial extraction experiments. Magnesium was not added to the feed solution.

TABLE-US-00003 TABLE 3 Chemical composition of CYANEX 272 raffinate feed solution for exploring the effect of VERSATIC Acid 10 concentration Metal Ni Mn Co Li Cu Input feed (ppm) 50271.1 687.2931 3235.903 7261.506 50.093

[0047] As illustrated in FIG. 6, increasing the concentration of VERSATIC Acid 10 increased the efficiency of nickel, manganese, and cobalt extraction. At a concentration of 60 vol. % VERSATIC Acid 10, there was an 80.33% Ni extraction. It was observed that as the concentration of VERSATIC Acid 10 increased, the raffinate color lightened and the organic phase color darkened which indicated a higher level of Ni extraction. It was further observed that as the volumetric ratio of VERSATIC Acid 10 to diluent increased, the viscosity of the organic phase also increased which led to metal transfer losses. Crud formation in the VERSATIC Acid 10 was observed at volumetric ratios of VERSATIC Acid 10 to diluent exceeding 45 vol. %. Taking these factors in totality, a concentration of 40 vol. % VERSATIC Acid 10 was determined to be optimal and resulted in 55% Ni extraction at room temperature. One approach to further enhance Ni extraction was to increase the organic-to-aqueous (O/A) ratio from 1:1 to 2:1. Experiments conducted using this change demonstrated that, at an O/A ratio of 2:1, a pH 6, and extraction at room temperature, 70% Ni extraction was achieved.

Example 3Extraction Temperature

[0048] In this example, experimental investigations were performed to determine an optimal temperature of the extraction processes for the selective removal of metal salts from solutions derived from leaching of black mass. Initial experiments were performed at ambient temperatures, and it was observed that extractant performance was improved at elevated temperatures. Though the use of lower concentrations of CYANEX 272, such as 15 vol. %, holds operational and economic advantages, these lower concentrations had challenges in optimization of the extraction efficiency. To optimize the extraction efficiency of lower concentrations of CYANEX 272 for Mn and Co co-extraction, various strategies were explored. These strategies included dilution of the feed solution, utilization of tributyl phosphate (TBP) as a modifier, investigating the synergistic effects of di(2-ethylhexyl)phosphoric acid (D2EHPA) in conjunction with CYANEX 272, and increasing the reaction temperature. These experiments revealed that elevating the temperature from room temperature (25 C.) to 50 C. yielded the most substantial benefits. This adjustment resulted in a notable increase in Mn and Co extraction rates, surpassing 99% while demonstrating negligible extraction of Li and Ni, as illustrated in the third set of bars in FIG. 7.

[0049] FIG. 7 further shows that as the temperature was increased, the extraction efficiency was higher compared to doubling the CYANEX 272 concentration, i.e., the first set of bars in FIG. 7, or diluting the feed solution twice, i.e., the second set of bars in FIG. 7. Additional experiments were performed to assess the impact of temperature variations on CYANEX 272extraction performance.

[0050] FIG. 8 illustrates the effect of temperature on the extraction of nickel, manganese, and cobalt salts under optimal reaction conditions, i.e., extractant concentration and pH. Table 4 presents the chemical composition of the feed solution for the temperature effect experiments.

TABLE-US-00004 TABLE 4 Chemical composition of feed solution for exploring the effects of temperature on CYANEX 272 extraction experiments Metal Ni Mn Co Li Input feed (g/L) 53.365 2.862 6.948 7.959

[0051] FIG. 8 illustrates a positive correlation between increasing temperature and the efficiency of nickel, manganese, and cobalt extraction. Notably, employing a 15 vol. % CYANEX 272 extractant at 50 C. resulted in high extraction yields, with 99.66% of Mn and 99% of Co extracted, while also maintaining clarity in the organic phase without any formation of crud. It was determined that operational conditions for CYANEX 272 extraction are as follows: a 15 vol. % CYANEX 272 solution within a pH range of 5-5.5 and operating at a temperature of 50 C. These conditions offered the highest recovery rates for Mn and Co extraction while minimizing operational challenges.

[0052] Additional experiments were performed to determine an optimal pH range for high Ni extraction with minimum operational challenges. FIG. 9 illustrates the VERSATIC Acid 10 extraction efficiency as a function of temperature; it is noted that the feed solution for room temperature (25 C.) experiments was different from the elevated temperature experiments as there was no Mg present. Table 5 shows the chemical composition of feed solutions for these experiments.

TABLE-US-00005 TABLE 5 Chemical composition of feed solution for exploring the effects of temperature on VERSATIC Acid 10 extraction experiments Metal Ni Mn Co Li Mg Input feed for RT (ppm) 50271.1 687.2931 3235.903 7261.506 0 Input feed for high T (ppm) 29121.86 81.2411 663.8767 1946.716 328.5904

[0053] As illustrated in FIG. 9, it was evident that, unlike extractions that used CYANEX 272, extractions using VERSATIC Acid 10 did not demonstrate improved performance with increasing temperature. Ni extraction percentages remained broadly consistent across the different extraction temperatures. The highest Ni extraction of 60% was achieved at 50 C. with an O/A ratio of 1:1. It was observed that the extraction temperature did not appear to influence the performance of VERSATIC Acid 10 for Ni extraction. It was further observed that there was no formation of a solid crust or crud or visible cloudiness in the organic phase. In addition, when an O/A phase ratio of 2:1 was used for extraction, there was a positive effect on Ni extraction efficiency. As a result of these experiments, 50 C. was identified as the optimal temperature for maximizing Ni extraction efficiency with an extractant solution having a concentration of 40 vol. % VERSATIC Acid 10 solution within a pH range of 5.6.

Example 4Maximum Loading Capacity

[0054] In this example, experimental investigations were performed to determine maximum loading capacity for metal salts in organic extractants, which is the quantity of extractant required to extract the target metal and is also used to assess the effectiveness of the extractant. The target metals under consideration for CYANEX 272 included Mn, Co, Mg, and Ni, while for VERSATIC Acid 10, only Ni was examined as it was the sole metal targeted for extraction. Table 6 lists the maximum loading capacity of CYANEX 272 and VERSATIC Acid 10 under ideal extraction conditions disclosed in Examples 1-3.

TABLE-US-00006 TABLE 6 Maximum loading capacity of CYANEX 272 and VERSATIC Acid 10 Metal of Loading capacity extractant/metal Extractant interest (g/L) (mol/L) (mol/mol) CYANEX Mn 5.27 0.096 4.95 272 Co 8.23 0.140 3.40 Mg 2.48 0.102 4.67 Ni 6.30 0.107 4.43 VERSATIC Ni 20.53 0.350 6.11 Acid 10

[0055] The maximum loading capacity of CYANEX 272 as listed in Table 6 indicates that 5 moles of CYANEX 272 were needed for extracting Mn, 3.5 moles of CYANEX 272 were needed for extracting for Co, 5 moles of CYANEX 272 were needed for extracting for Mg, and 4.5 moles of CYANEX 272 were needed for extracting for Ni extraction. To enhance Co and Mg co-extraction, it is hypothesized that the removal of excess Mn prior to extraction with CYANEX 272 extraction could improve extraction efficiency and prevent CYANEX 272 overloading. In the case of Ni extraction, 6 moles of VERSATIC Acid 10 were needed to extract 1 mole of Ni. This observation was consistent with previous observations that increased concentrations of VERSATIC Acid 10 and an increased O/A ratio were needed for achieving complete Ni extraction.

Example 5Process Purity

[0056] In this example, experimental investigations were performed to determine the purity of the resulting recovered metal salts from the two-stage extraction process disclosed herein. Process purity is correlated to the determined optimal extraction conditions as it was a metric used to determine the extraction success. Several experiments were performed to determine the performance of the two-stage extraction process under the determined ideal conditions. FIG. 10 illustrates a comparison between other theorized processes highlighting the metals remaining in the product solution. As illustrated in FIG. 10, the Ni sulfate solution obtained through the two-stage process disclosed herein when performed at extraction temperature of 50 C. exhibited the highest purity, characterized by the highest Ni content and minimal Mn, Co, Mg, and Na content. This purity level rendered the solution suitable for CAM (Cathode Active Material) manufacturing without necessitating additional purification steps.

[0057] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term plurality refers to two or more items or components. The terms comprising, including, carrying, having, containing, and involving, whether in the written description or the claims and the like, are open-ended terms, i.e., to mean including but not limited to. Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases consisting of and consisting essentially of, are closed or semi-closed transitional phrases, respectively, with respect to the claims. Use of ordinal terms such as first, second, third, and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0058] Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Any feature described in any embodiment may be included in or substituted for any feature of any other embodiment. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

[0059] Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments disclosed.