WO2025238305A1

WO2025238305A1 - Solvent extraction process connection for recovery of manganese, cobalt and nickel

Info

Publication number: WO2025238305A1
Application number: PCT/FI2025/050251
Authority: WO
Inventors: Hannu Laitala
Original assignee: Metso Finland Oy
Current assignee: Metso Finland Oy
Priority date: 2024-05-15
Filing date: 2025-05-15
Publication date: 2025-11-20
Anticipated expiration: 2026-11-15
Also published as: FI20245614A1; CN120967171A

Abstract

The present invention concerns a process for recovering cobalt (Co), manganese (Mn) and nickel (Ni) from aqueous feed solutions comprising these elements. In the process, the aqueous feed solution is subjected to a first solvent extraction step in which the target elements Co, Mn, and Ni are extracted, leaving magnesium (Mg) and calcium (Ca) in the aqueous phase. The target elements are then selectively stripped from the extraction solution into a Co, Mn and Ni containing solution, from which Mn can be recovered by solvent extraction producing a raffinate containing Co and Ni.

Description

SOLVENT EXTRACTION PROCESS CONNECTION FOR RECOVERY OF MANGANESE, COBALT AND NICKEL

FIELD

[0001] The present invention relates to a process for recovering critical metals, in particular cobalt, manganese and nickel, from aqueous feed solutions containing the same.

BACKGROUND

[0002] The importance of recycling and recovering critical metals, such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), has grown remarkedly with the development and increased production of new electric vehicles and the thus steadily growing demand for batteries. The current battery technology commonly relies on such critical metals whereby, beside efficient recovery from primary mineral resources, recovering of these metals from secondary resources, such as spent batteries, is of high importance.

[0003] Hydrometallurgical separations of metals from spent batteries, typically lithium-ion batteries, proceed via the recovery of a black mass, which contains cathode active material and anode material, but from which wiring and other coarse solid battery components, such as plastic or steel parts, have already been removed. The next step is typically to separate cathode active material from the other components of the black mass, e.g., by using mechanical, thermal or chemical pre-treatment steps, followed by acid leaching to solubilize the cathode active material, and to prepare them for recovery.

[0004] Naturally, the proportion of metals present in black mass, production side streams, intermediate products, or natural minerals may vary. The recovery of individual metals in pure solutions is a demanding process and in terms of efficient use of the mineral resources, it is crucial to achieve high recovery rates for the target metals. In practice, this leads to a balance between costs and recovery efficiency.

[0005] In particular metals and impurities with similar properties as the target elements may interfere in the separation reaction and thus have a negative effect on either the purity of the product or the recovery rate. It might therefore not be economical to recover metals that are present in low concentrations or metals requiring several impurity removal steps. This is currently the case for manganese and cobalt solutions, which also typically contain nickel and impurities that may be difficult to separate, such as calcium and magnesium.

[0006] The prior art comprises various process schemes for the recovery of valuable metal components and for the removal of impurities. One such process is presented in publication WO 2023/163658 A2, disclosing processes and systems for purifying and recycling lithium-ion battery waste streams. The process and system comprise removal of impurities and separation of nickel, cobalt and manganese from a purified filtrate liquid stream by co-precipitation or by means of one or more chromatographic columns. The publication does not disclose solvent extraction processes for separation and recovery of Mn, Co or Ni.

[0007] Another prior art publication relating to the recovery of nickel, manganese and cobalt is publication WO 2022/183243 Al, which discusses the production of a coprecipitate comprising at least two of these metals. Said co-precipitate may be suitable for preparation of lithium-ion batteries.

[0008] A standard solvent extraction process scheme for the recovery of nickel and cobalt from solutions with low nickel concentration or solutions obtained from black mass includes a first impurity removal step. The impurity removal step is typically carried out in a process where manganese (Mn), calcium (Ca), zinc (Zn), iron (Fe), and copper (Cu) is removed in a first solvent extraction step. Such a solvent extraction may be carried out using di(2-ethylhexyl)phosphoric acid (DEHP A), which is capable of extracting manganese, calcium, zinc, iron, and copper from an aqueous feed solution. The subsequent cobalt recovery step may in such a process be carried out by solvent extraction using dialkyl phosphinic acid, which is sold under the trade name Cyanex® 272, with high selectivity between nickel and cobalt. However, dialkyl phosphinic acid has poor selectivity between cobalt and manganese, which would be a problem if manganese was not removed in the first solvent extraction step together with calcium and other impurities. In the third step, nickel may be recovered by a metal extractant, such as neodecanoic acid, which is sold under the trade name Versatic™ Acid 10. Neodecanoic acid has low selectivity between divalent metal ions, and has thus been used as a third solvent extraction step for separating nickel from other components remaining in the aqueous phase, in particular from monovalent cations, such as sodium, potassium, lithium, and ammonium, as well as divalent cations like calcium and magnesium. With such a conventional solvent extraction system, the total Ni amount need to be extracted in order to separate it from magnesium and calcium. [0009] A drawback with the currently employed solvent extraction process as described above is that manganese is removed in the first solvent extraction step together with calcium, zinc, iron, and copper. Especially the separation of manganese and calcium is demanding. One currently deployed process to separate calcium in a manganese containing solution is by addition of fluoride to form calcium fluoride precipitate. This will, however, lead to fluoride being present in the further process, where it is likely to cause problems. Further problems will arise from magnesium in the presence of cobalt. Currently, the process requires prewashing to reduce the amount of Mg to a level where solvent extraction may be employed. Especially with feeds containing large amounts of calcium and magnesium, such as mixed hydroxide precipitate (MHP), this problem becomes evident, as the separation of magnesium in solvent extraction of cobalt is a difficult process.

[0010] With an increasing demand for manganese, there is still a need for a more efficient process for concurrent recovery of manganese, cobalt and nickel in solutions containing the same, which currently is a demanding and costly process.

SUMMARY OF THE INVENTION

[0011] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0012] Thus, the present invention concerns a process for recovering cobalt (Co), manganese (Mn) and nickel (Ni) from aqueous Co, Mn and Ni bearing feed solutions. The process comprises the following steps:

- subjecting the aqueous feed solution to a first solvent extraction step in which the target elements Co, Mn, and Ni are extracted by use of a first organic extraction solution forming an organic phase, leaving an aqueous phase comprising divalent cations of magnesium (Mg) and calcium (Ca), when present,

- subjecting the organic phase from the first solvent extraction step to a stripping step, in which stripping step the target elements are selectively stripped into an aqueous target element solution containing Co, Mn and Ni,

- subjecting the aqueous target element solution to a second solvent extraction step in which Mn is, by use of a second organic extraction solution, extracted from the target element solution into an Mn containing extraction solution, leaving an aqueous raffinate containing Co and Ni, - recovering Mn from the Mn containing organic extraction solution through a stripping process, thus producing an aqueous Mn product solution, and

- recovering Co and Ni from the aqueous raffinate obtained in the second solvent extraction step.

[0013] Several advantages are achieved using the present invention. Among others, the process of the invention provides a simplified and cost-effective process for simultaneous recovery of manganese, cobalt and nickel. In current processes, manganese typically ends up with the impurities, such as magnesium and calcium, while the process connection according to the present invention separates the target elements from calcium and magnesium at an early stage, whereby these impurities will not interfere with the subsequent separation steps. Also, further impurities, such as chloride, fluoride, potassium and sodium, are preferably removed from the feed already in the first processing step. [0014] Since the present invention includes early removal of impurities and/or elements that typically interfere with the separation process, the advantages obtained with the invention include the reduced need to perform multiple prewashing or purification steps in the recovery of manganese, cobalt and nickel from sources containing elements that typically interferes in the solvent extraction process, such as calcium and magnesium. Further, the process is designed such that addition of additional reagents or ions may be avoided once these already have been removed. The process is thus suitable for the recovery of critical metals from, for example, contaminated cobalt feeds, mixed hydrogen precipitate, black mass and raw materials containing low amounts of nickel in a simplified process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIGURE 1 illustrates a preferable solvent extraction scheme in accordance with at least some embodiments of the present invention. From the first solvent extraction step (1), i.e., the preliminary solvent extraction (Pre SX), a target element solution containing Mn, Co and Ni is transferred to a second solvent extraction step (2), i.e., the manganese solvent extraction (Mn SX). An aqueous reject containing Mg and Ca, and optionally further contaminants not extracted in the first solvent extraction step, such as monovalent cations as well as F’ and Cl’, is formed in the preliminary solvent extraction. The target metals, i.e., Mn, Co and Ni, are selectively stripped from the organic phase into a target element solution, which is transferred to the second solvent extraction step (Mn SX). Further metal elements present in the extract can be stripped into a second stripping fraction, i.e., an impurity solution, which may contain, for example, Al, Cu, Fe and Zn. This impurity solution is rejected prior to the second solvent extraction step, in which manganese is extracted and recovered. The second solvent extraction step is preferably performed using preloading of the organic phase, which in Figure 1 is illustrated by removal of Na, as an exemplary base cation. Ni and Co are recovered from the raffinate obtained in the second solvent extraction step. Preferably, Ni and Co are separated into separate streams by means of ion exchange (Ni IX), in particular when Ni is removed from cobalt (i.e., Co is main element). If the main element of the Ni and Co containing stream after the Mn SX is Ni, then the Ni IX step as presented in Figure 1 can be replaced by a Co SX process. In both options Co and Ni will be separated into separate product streams. [0016] The system presented in Figure 1 illustrates a preferred embodiment of the invention, and should not be seen as limiting for the scope of the present disclosure.

EMBODIMENTS

[0017] The present invention concerns a process for concurrent recovery of critical metals using solvent extraction (SX). Solvent extraction processes are based on ion exchange between an aqueous phase and an organic phase. Hence, the transfer or recovery of a specific element in solution is herein to include corresponding ions, even if not specifically expressed.

[0018] In particular, the invention concerns a process for recovering cobalt (Co), manganese (Mn) and nickel (Ni) from aqueous Co, Mn and Ni bearing feed solutions. The process comprises the following steps:

- subjecting the aqueous feed solution to a first solvent extraction step in which the product elements Co, Mn, and Ni are extracted by use of a first organic extraction solution forming an organic phase, leaving an aqueous phase comprising divalent cations of magnesium (Mg) and calcium (Ca), when present,

- subjecting the organic phase from the first solvent extraction step to a stripping step, in which stripping step the target elements are selectively stripped into an aqueous target element solution containing Co, Mn and Ni, and impurity elements are preferably stripped into a separate impurity solution,

- subjecting the aqueous target element solution to a second solvent extraction step in which Mn is, by use of a second organic extraction solution, extracted from the target element solution into an Mn containing organic extraction solution, leaving an aqueous raffinate containing Co and Ni,

- recovering Mn from the Mn containing extraction solution through a stripping process, thus producing an aqueous Mn product solution, and

[0019] The aim of the first solvent extraction step, being a preliminary solvent extraction step, is to remove impurities that tend to interfere in the further solvent extraction steps. Such interfering compounds are in particular calcium and magnesium. In current solvent extraction processes, manganese is often removed together with impurities, in particular calcium ions, into the same phase, and the recovery of manganese from calcium containing solutions is typically a complicated and difficult process. A standard process for separation of calcium and manganese is to add fluoride, which in turn causes problems in the subsequent process steps. The drawbacks of the conventional processes may lead to manganese not being recovered but removed together with the contaminants. [0020] Magnesium is another contaminant causing difficulties in the process of recovering critical metals, and is particularly difficult to separate from cobalt. By utilization of an extraction process rejecting calcium and magnesium already in the preliminary solvent extraction step, the further separation and purification steps can be performed in a simple and cost-effective manner. Both the Mn containing extraction solution, or a corresponding Mn containing stripping solution, as well as the Co and Ni containing raffinate are essentially free from impurities. Manganese may thus be directly recovered from the aqueous Mn product solution through crystallisation or electrolysis.

[0021] The process of the invention thus provides an alternative process connection for recovering manganese, cobalt and nickel from aqueous solutions. It was discovered that by using an organic extractant with low selectivity for different metals, simultaneously extracting all target metals, the recovery process for Mn, Co and Ni as pure solutions can be simplified.

[0022] In the process of the present disclosure, the target metal ions are in the first solvent extraction step transferred to the organic phase, possibly together with other metal ions present in the aqueous feed solution. Some impurity ions, such as magnesium and calcium, when present in the feed solution, are in the first solvent extraction step rejected to the aqueous phase. To remove any residual amounts of such impurity ions that have been co-extracted into the organic phase, in particular calcium, the loaded organic solution can be contacted with a scrubbing solution before the subsequent stripping process.

[0023] The stripping process is preferably performed in two steps, whereby a first fraction of target element ions is first selectively stripped from the organic solvent, followed by stripping of other metal ions into an impurity fraction.

[0024] The target element solution is then subjected to a second solvent extraction step in which Mn is extracted from the aqueous target element solution into an Mn containing organic extraction solution, leaving an aqueous raffinate containing Co and Ni. Manganese is recovered from the loaded organic extraction solution through a stripping process.

[0025] According to some embodiments of the invention, the step of recovering Co and Ni from the aqueous raffinate comprises a Co/Ni separation step, from which Ni and Co are recovered as separate solutions. This enables Co and Ni to be purified and processed separately, and thus further use as raw material independently of each other. Preferably, the Co/Ni separation step is carried out by means of ion exchange. In such ion exchange processes, nickel will be retained by the ion exchange resin, from which it can be separately recovered, while cobalt will pass through the ion exchange column and can be recovered as pure solution. The capacity of the process is thus limited by the nickel content of the raffinate, why it is best suited for solutions with relatively low nickel content in relation to cobalt content. In cobalt based MHP solutions Co/Ni ratio is typically between 1 :1-100:1

[0026] The Co/Ni separation step can alternatively be carried out through other separation processes known in the art, such as by a third solvent extraction step. Such a third extraction step can be carried out using extraction conditions known in the prior art for the separation of cobalt and nickel, for example, by using an extractant containing dialkyl phosphinic acid, which is sold under the trade name Cyanex® 272.

[0027] According to a particularly preferred embodiment of the invention, the second solvent extraction step comprises preloading the organic phase with Co and/or Ni. By preloading the organic phase with Co and/or Ni, no pH adjustment is required in the Mn extraction step. Because no acid formation takes place in the second solvent extraction process when the organic phase is preloaded with Co and/or Ni, the addition of neutralization bases can be avoided in the Mn extraction step. During the Mn solvent extraction, Mn is replacing Co and/or Ni in the preloaded organic phase, whereby Co and/or Ni is transferred to the aqueous phase. [0028] The preloading of the organic phase can thus be an integrated part of the second solvent extraction step. By not performing the pH control by addition of bases in the Mn solvent extraction step, contamination of the aqueous phase with base cations, such as Na⁺, can be avoided. Likewise, any precipitation of the base cation may be avoided. Without the preloading step the raffinate would be contaminated with such cations originating from the base compound, typically sodium, and would thus interfere in the subsequent Co and Ni recovery step, or remain as an impurity. When the pH is already controlled in the preloading process, the aqueous solution containing base cations may be removed from the process in a separate aqueous stream (shown in Fig 1. as Na stream). A further benefit of the preloading step is that the concentration of Co and/or Ni in the raffinate from the Mn solvent extraction can be raised, thus reducing the volume of solution to be processed in the following step. The first solvent extraction step can be performed without preloading, as the most common base cations, such as sodium, remain in the aqueous phase.

[0029] In a further embodiment of the invention, aluminum (Al), copper (Cu), iron (Fe), and zinc (Zn), when present in the aqueous feed solution, are in the first solvent extraction step extracted into an organic phase together with the target elements, and preferably stripped into a separate impurity solution in the stripping step. The organic extractant, i.e., organic extraction solution, and the solvent extraction parameters may in the first solvent extraction step be chosen such that almost all metal elements are extracted into the organic phase. By selectively stripping the target ions from the metal containing extractant, two different stripping fractions can be obtained, i.e., a first stripping fraction containing the target elements (Co, Mn and Ni) and a second stripping fraction containing other metals, such as Al, Cu, Fe and Zn, herein referred to as an impurity fraction. In the stripping step, some of the zinc, and in lesser extent copper, may transfer to the target element fraction. Any zinc present in the target element fraction would likely be extracted together with Mn in the manganese solvent extraction step. Separation of Mn and Zn can be easily performed by techniques known in the art, for example ion exchange. Since some of the Zn would be extracted to the impurity fraction, the concentration of Zn is likely to be at a level where ion exchange is a preferred purification technique.

[0030] In a further preferred embodiment, the first solvent extraction step is carried out in a manner that allows monovalent ions selected from chloride (Cl ), fluoride (F ), sodium (Na⁺), potassium (K⁺), and lithium (Li⁺) to remain in the aqueous phase. It is further preferred to choose the extractant, i.e., the first extraction solution, and the solvent extraction conditions such that monovalent ions are rejected in the first, i.e., preliminary, solvent extraction. In addition to Mg and Ca, such monovalent ions are commonly present in the raw material, and generally cause different problems when using standard connections of the prior art. In particular monovalent cations, as well as fluoride and chloride, can be rejected in the process of the current disclosure. In this manner, any contaminants normally causing difficulties in the solvent extraction or purification process, such as fluoride added for calcium removal in prior art solutions, can be separated already in the preliminary solvent extraction. Thereby, the organic phase is essentially free from Ca, Mg and monovalent ions, especially Cl, F, Na, K, and Li, when being subjected to the selective stripping step.

[0031] The process of the invention is especially suitable for solutions containing relatively low amounts of nickel. Thus, in a preferred embodiment, the feed solution contain nickel in an amount up to 70 g/L, preferably up to 50 g/L, even more preferably up to 20 g/L. At nickel levels this low, the process is economically particularly beneficial.

[0032] In an embodiment of the invention, the total content of Co, Mn, and Ni in the target element solution is up to 150 g/L, such as up to 120 g/L, or in a range of, for example, 50-150 g/L or 30-120 g/L. This solution may thus be a relatively concentrated solution with respect to the metal content. The total metal concentration may be just under the saturation point where the metal ions would form precipitates. The increased target metal concentration when compared to the feed solution generally contributes to increased recovery rates and a more efficient process.

[0033] The Mn product solution may contain residuals of impurities, such as copper and zinc. In particular zinc may in some extent be co-extracted together with manganese and further stripped into the aqueous Mn product solution. In one embodiment of the invention, the Mn product solution is further purified through ion exchange. In this way, a pure Mn fraction can be obtained in a cost-effective manner.

[0034] The first solvent extraction step, i.e., the preliminary solvent extraction, is carried out using a first organic extraction solution capable of extracting the target elements Co, Mn and Ni, and rejecting main contaminants, such as Mg and Ca. In a preferred embodiment, neodecanoic acid functions as extractant in the preliminary solvent extraction step, i.e., as the first extraction solution. Neodecanoic acid is a mixture of branched CIO carboxylic acid, and is sold under the tradename Versatic™ Acid 10. Neodecanoic acid is capable of extracting almost all metals, there among Mn, Co and Ni, at the same time rejecting Ca and Mg, as well as monovalent cations and some monovalent anions, such as F’ and Cl’. Neodecanoic acid has been previously used for solvent extraction of Ni after separating other components, such as Co and Mn, present in the feed solution. When using neodecanoic acid as extractant, almost all other metals are extracted as well, and can in the following step be selectively stripped into a target element solution and a further fraction, herein referred to as an impurity solution. The first solvent extraction step can be carried out using a pH in the range of 5-8, preferably in a range of 6.5-8, and even more preferably in a range of 6.5-7. The solvent extraction temperature during the first solvent extraction step can be in the range of 40-60 °C, preferably 45-55 °C. Within these ranges, neodecanoic acid, or similar functionality extractants, can be used in the concurrent solvent extraction of Mn, Co and Ni, while rejecting Ca and Mg. Preferably, monovalent ions are also rejected by the extractant, i.e., first organic extraction solution, in particular ions selected from chloride (Cl ), fluoride (F ), sodium (Na⁺), potassium (K⁺), and lithium (Li⁺). This means that ions like fluoride and chloride can be removed at the first solvent extraction step, thus not interfering in the further process. [0035] The selective stripping of the target elements into an aqueous solution is preferably performed using a pH in the range of 3.5-6. The temperature may be in the range of 40-60 °C. The stripping process is preferably divided into two stages, whereby the first stripping fraction obtained typically is the target element solution. Subsequent to stripping Mn, Co and Ni, other metal elements present in the extract may be stripped into a further metal fraction, i.e., an impurity solution, from which the impurity elements can be recovered. Alternatively, the impurity solution may be discarded. Impurity metals can be stripped down in pH < 4.5 (in particular 0.5-4.5). The stripping step for recovery of the target elements Mn, Co and Ni may be performed at temperature in the range of 40-60 °C. The pH is preferably in the range of 4.5-6 during the selective stripping of the target elements. The impurities may be stripped from the extract of the first solvent extraction using a temperature in the range of 40-60 °C, preferably 45-55 °C. The pH is preferably < 4.5 during the stripping of impurity metals.

[0036] The second solvent extraction step is carried out using a second organic extraction solution, which is an organic extractant capable of selectively extracting manganese, thus obtaining an aqueous raffinate containing Co and Ni. In a preferred embodiment, di(2-ethylhexyl)phosphoric acid (DEHP A) functions as extractant in the second solvent extraction step. The second solvent extraction step may be carried out using a pH <4, preferably in the range of 3-4. The solvent extraction temperature may be in the range of 35-45 °C. Within these ranges, DEHPA, or similar functionality extractants, may be used to selectively extract Mn from Ni and Co.

[0037] The process of the present disclosure is suitable for recovery of manganese, cobalt and nickel from various sources. It is especially preferable for feed solutions containing relatively low amounts of nickel, as such a process connection is very cost efficient for obtaining pure Mn, Co and Ni product solutions. The process may be performed on a feed solution obtained from black mass and also from intermediate products or side streams, such as mixed hydroxide precipitate (MHP). The aqueous feed solution may thus be a leach solution originating from a Co, Mn and Ni bearing raw material selected from MHP, black mass and natural minerals. Currently, the recovery of Mn and Co from MHP precipitate requires several impurity removal steps.

[0038] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. [0039] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0040] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0041] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In this description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc.

[0042] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0043] The following non-limiting example is intended merely to illustrate the advantages obtained with the embodiments of the present invention.

EXAMPLE

Example 1 - Concurrent recovery of manganese, cobalt and nickel using solvent extraction An aqueous feed solution containing manganese, cobalt and nickel was subjected to a solvent extraction step using Versatic™ Acid 10 as extractant. The extraction was carried out at pH 6.8 and a temperature of around 50°C. An extract containing Mn, Co, Ni, Zn, Cu, Fe and Al was obtained. The impurity ions Cl’, F’, Ca²⁺ and Mg²⁺ were rejected to the aqueous phase and removed from the process. Loaded organic solution was contacted with scrubbing solution to remove any co-extracted calcium from the organic phase before stripping.

A selective stripping process was carried out on the extract obtained using Versatic™ Acid 10. Two different stripping solutions were obtained by first stripping Mn, Co and Ni from the extract into a product fraction and subsequently stripping Zn, Cu, Fe and Al into a separate impurity fraction. The aqueous product solution contained Mn, Co and Ni as well as residual amounts of Zn and was obtained using a stripping solution with a pH of 4.5-6. The aqueous product solution obtained in the previous step was subjected to a manganese solvent extraction step using DEHPA as extractant. The second solvent extraction was carried out at pH 3.8 and a temperature of about 40 °C. The extractant was pre loaded with Ni and Co to avoid base addition for pH control in the solvent extraction process. Mn as well as residual Zn was extracted and stripped into a manganese product solution. The manganese product solution was subjected to an ion exchange step for removal of Zn and a solution of pure manganese was recovered.

The aqueous raffinate obtained from the Mn solvent extraction step was a pure Co and Ni containing solution. The raffinate was subjected to an ion exchange step from which a pure Co containing solution was obtained. The ion exchange column was eluated to recover an eluate of pure nickel solution.

INDUSTRIAL APPLICABILITY

[0044] The present process can be used in the recovery of critical metals, in particular Mn, Co and Ni, from primary and secondary sources. Such metals are commonly used in the battery industry.

[0045] Particularly, the herein described process connection makes it possible to recover critical metals by solvent extraction in a simplified manner, such that prewashing or complicated separation steps can be avoided even at higher concentrations of calcium and magnesium.

Citation List

Patent Literature

WO 2023/163658 A2

WO 2022/183243 Al

Claims

1. Process for recovering cobalt (Co), manganese (Mn) and nickel (Ni) from aqueous Co, Mn and Ni bearing feed solutions, wherein the process comprises the following steps:

- subjecting the aqueous target element solution to a second solvent extraction step in which Mn is, by use a second organic extraction solution, extracted from the aqueous target element solution into an Mn containing organic extraction solution, leaving an aqueous raffinate containing Co and Ni,

- recovering Mn from the Mn containing organic extraction solution through a stripping process, thus producing an aqueous Mn product solution, and

2. The process according to claim 1, wherein the step of recovering Co and Ni from the aqueous raffinate comprises a Co/Ni separation step, from which Ni and Co are recovered as separate solutions.

3. The process according to claim 2, wherein the Co/Ni separation step is carried out by means of ion exchange or solvent extraction.

4. The process according to any of the preceding claims, wherein in the second solvent extraction step comprises preloading the organic phase with Co and/or Ni.

5. The process according to any of the preceding claims, wherein aluminum (Al), copper (Cu), iron (Fe), and zinc (Zn), when present in the aqueous feed solution, are in the first solvent extraction step extracted into the organic phase together with the target elements.

6. The process according to any of the preceding claims, wherein the first solvent extraction step is carried out in a manner that allows monovalent ions selected from chloride (Cl ), fluoride (F ), sodium (Na⁺), potassium (K⁺), and lithium (Li⁺) to remain in the aqueous phase.

7. The process according to any of the preceding claims, wherein the feed solution contain nickel in an amount up to 70 g/L, preferably up to 50 g/L, more preferably up to 20 g/L.

8. The process according to any of the preceding claims, wherein the total content of Co, Mn, and Ni in the target element solution is up to 150 g/L.

9. The process according to any of the preceding claims, wherein the aqueous Mn product solution is further purified through ion exchange.

10. The process according to any of the preceding claims, wherein neodecanoic acid is used as the first organic extraction solution in the first solvent extraction step.

11. The process according to any of the preceding claims, wherein the first solvent extraction step is carried out at a temperature in the range of 40-60 °C, preferably 45-55 °C, and a pH in the range of 5-8.

12. The process according to any of the preceding claims, wherein di(2- ethylhexyl)phosphoric acid (DEHP A) is used as the second organic extraction solution in the second solvent extraction step.

13. The process according to any of the preceding claims, wherein the second solvent extraction step is carried out at a temperature in the range of 35-40 °C and a pH < 4, preferably in the range of 3-4.

14. The process according to any of the preceding claims, wherein a leach solution originating from a Co, Mn and Ni bearing raw material selected from mixed hydroxide precipitate (MHP), black mass and natural minerals is used as the aqueous feed solution.