Method for processing cathode active materials by means of reactive extraction

Abstract

The invention relates to a method for processing cathode active materials, in particular for recovering the valuable metals nickel, cobalt and manganese, by means of reactive extraction.

Description

[0001] STAW 625 251045wo

[0002] METHOD FOR REPROCESSING CATHODE ACTIVE MATERIALS

[0003] BY MEANS OF REACTIVE EXTRACT

[0004] The present invention relates to a process for the processing of cathode active materials, in particular for the recovery of the valuable metals nickel, cobalt and manganese, by means of reactive extraction.

[0005] BACKGROUND OF THE INVENTION

[0006] The transition of transport and mobility to sustainable energy sources is one of the greatest projects of our time. However, the lack of high-performance batteries is hindering the substitution of combustion engine vehicles with purely electric vehicles. At the same time, it has become clear that the ambitious goal of reducing CO2 emissions can only be achieved if the development of new and long-lasting lithium-ion batteries (LIBs) is accompanied by a corresponding recycling concept for used batteries. The focus here is particularly on the recovery of the valuable metals nickel, cobalt, manganese, and lithium, which are contained in cathode active materials for high-energy-density LIBs. The composition of these cathode active materials (CAMs) can be described for the so-called NCM (nickel, cobalt, manganese) type by the general formula LiMn₂. x Co yNii-xy describes another class of compounds, the aluminum-containing CAMs with a typical composition LiNiCoo.isAIo.osC .

[0007] The reprocessing of used lithium-ion batteries, such as those used in electric vehicles, involves several steps, each carried out in specialized facilities. The first step is mechanical processing of the battery after discharge, through shredding and mechanical separation processes – the so-called pre-treatment. This process yields various fractions, including the so-called black mass. This black mass is then further processed in metallurgically oriented facilities as part of the post-treatment process.

[0008] The recovered black mass contains, in addition to residues of organic solvents and electrolyte, as well as metallic remnants from the copper or aluminum foil electrodes, primarily graphite as the anode active material and lithium transition metal mixed oxides as the cathode active material. The challenge, therefore, lies in separating the metals Cu, Al, Ni, Co, Mn, and Li contained in the black mass and recovering them in a form and purity sufficient to produce new cathode active materials.

[0009] The recycling of used batteries is a collaborative process. Many companies already specialize in the pretreatment described above, while others develop processes for the hydrometallurgical processing of the black mass. Following hydrometallurgical processing, the synthesis of CAM precursor compounds, known as pCAMs (mixed hydroxides of nickel, cobalt, and manganese), takes place. Hydrometallurgical processing of the black mass and pCAM synthesis can be carried out by a single company, or the hydrometallurgical processing may be limited to the commercially available transition metal sulfates in one company, while pCAM production is performed in other companies.This overall strategy, based on a division of labor, makes sense in the interest of a rapid introduction of global battery recycling, which should be done with the smallest possible CO2 footprint in the interest of the climate, which in particular means minimizing both the use of energy and the use of H+B materials.

[0010] Several methods for reprocessing lithium-ion batteries are already known from the state of the art.

[0011] H. Wang et al. describe an approach in "Development of a highly efficient hydrometallurgical recycling process for automotive Li-ion batteries," published in J. Sustain. Metall. (2015) 1: 168-178. In this approach, the black mass obtained after mechanical treatment of the battery is subjected to a leaching step to separate graphite. Copper is precipitated by adding iron powder and aluminum and iron as hydroxides. Cobalt, nickel, and manganese are separated as hydroxide, carbonate, and sulfite in a joint precipitation. Finally, the remaining lithium is precipitated as lithium carbonate. This process has the disadvantage that no further separation of the valuable metals cobalt, nickel, and manganese occurs, and a separate process is required for each component of the black mass.

[0012] J. Jung et al. describe a process in "A novel closed-loop process for recycling spent Li-ion battery cathode materials", International Journal of Green Energy (2021) 18: 15, 1597-1612, in which the sodium conventionally used as a precipitation reagent is replaced by lithium, thus avoiding the formation of sodium salts as a waste product, which are difficult to dispose of. However, attempts to separate nickel, cobalt, and manganese from each other by pH-controlled precipitation were not pursued further, so these elements could only be obtained as a mixture.

[0013] In their work published in Green Chem. 2013, 15, 1183, "A novel method to recycle mixed cathode materials for lithium batteries", H. Zou et al. forego separating nickel, cobalt, and manganese, instead preferring precipitation as a mixed hydroxide. The stoichiometry of the mixed hydroxide can be adjusted by prior addition of NiSC, CoSC, and MnSC. The mixed hydroxide is then used to synthesize LiNi0.33Mn0.33Co0.33O2.

[0014] Currently, there is no unified market for cathode active materials (CAMs) or their precursors (pCAMs); rather, the exact compositions vary depending on the battery manufacturer. Therefore, the current priority is to recover the metals as universally applicable and easily traded transition metal products in the form of their sulfates with sufficient purity. To increase energy density, the trend is toward cathode active materials with a high nickel content. Thus, over the course of historical development, the composition of Ni, Co, and Mn has shifted from a one-third mix (NCM 111) to current nickel contents of 80% (NCM 811), with even higher nickel contents expected in the future. This, in turn, makes the efficient recovery of these valuable metals all the more important.

[0015] Black mass is usually obtained by subjecting the mechanically processed used batteries to a leaching step, in which mineral acids are usually used as leaching agents, so that the valuable metals nickel, cobalt and manganese are obtained as an aqueous metal salt solution.

[0016] Methods for separating metal ions from aqueous solution are well known. Reactive extraction has become established as a common method, in which the metal ion to be extracted is transferred from the aqueous to the organic phase (extract) by reaction with an extraction solvent dissolved in an organic solvent (hereinafter referred to as solvent). The principle of reactive extraction can generally be illustrated using the example of a divalent metal ion as follows: M 2+ (aq) + 2 HR(org) — M R.2(org) + 2 H + (aq) (l) where M 2+ the metal ion and HR, the extraction agent.

[0017] Equation (1) is written here in its simplest form for illustrative purposes, without any limiting effect. It is known to those skilled in the art that, depending on the metal and concentration ratios, other metal complexes can also be formed by including further undissociated ligands HR.

[0018] The abstraction of the proton from the acid HR can, in principle, be achieved in two different ways. The required amount of OH' ions can be supplied by adding NaOH to the aqueous phase during the extraction process. This is done in the well-known conventional pH-controlled extraction, usually in mixer-settler systems using multi-stage countercurrent extraction.

[0019] Alternatively, the extraction solvent can be activated before the actual extraction process, which is usually also done with sodium, resulting in the following reaction equation:

[0020] M 2+ (aq) + 2 Na R(org) =M 2(org) + 2 Na + (aq) (2) .

[0021] In the prior art, there are several efforts to use reactive extraction to separate the metals contained in the cathode active materials from aqueous solution.

[0022] IR Rodrigues et al investigate the influences of different solvents on the extraction of cobalt with Cyanex® 272 from a nickel-containing solution in "Separation of cobalt and nickel via solvent extraction with Cyanex-272: Batch experiments and comparison of mixer-settlers and an agitated column as contractors for continuous counter-current extraction" in Separation and Purification Technology 296 (2022) 121326.

[0023] In their article “Product recovery from Li-ion battery waste coming from an industrial pre-treatment plant: Lab scale tests and process simulations” in Journal of Power Sources 206 (2012) 393-401, G. Granat et al. address the recovery of lithium and cobalt from lithium-ion batteries. To recover cobalt, it was first precipitated with NaOH, and the remaining solution was subjected to solvent extraction. Cyanex® 272 and D2HEPA were dissolved in kerosene as the solvent phase and partially saponified by the addition of NaOH. The metal was recovered from the organic solution by stripping with H2SO4.

[0024] In another publication by G. Granata, “Simultaneous recycling of nickel metal hydride, lithium ion and primary lithium batteries: Accomplishment of European Guidelines by optimizing mechanical pre-treatment and solvent extraction operations” in Journal of Power Sources 212 (2012) 205-211, solvent extraction was also used to recover the valuable metals. It was found that Cyanex® 272, at a stoichiometric Cyanex / Co ratio of 4 and a pH of 5-6, could be used to separate cobalt and nickel. However, in the presence of manganese, its selectivity was reduced, so manganese had to be separated first using D2EHPA at a stoichiometric D2EHPA / Mn ratio of 2 and a pH of 4.

[0025] In their article “Resource recovery of critically-rare metals by hydrometallurgical recycling of spent lithium ion batteries” in Separation and Purification Technology 209 (2019) 725-733, R. Satter et al. discuss the selective precipitation of metals from a leaching solution. While manganese and nickel were precipitated with KMnC and C4H8N2O2, respectively, cobalt was recovered as CoSO4 in a two-stage extraction process using Cyanex® 272, which was 50% saponified with Na. In a final step, lithium was precipitated as U2CO3 using Na2CO3.

[0026] WO 2022 / 236381 describes a process for obtaining nickel and / or cobalt salts from corresponding raw materials. The raw material is first treated with an iron or aluminum salt to precipitate alkali metal ions and monovalent cations, and nickel and / or cobalt salts are then isolated from the remaining solution by stepwise increasing the pH.

[0027] W. Zhang et al investigate various methods for the recovery of manganese in "Manganese metallurgy review. Part II : Manganese separation and recovery from solution", published in Hydrometallurgy 89 (2007) 160-177.

[0028] WO 2020 / 212363 discloses a process for recovering aluminium and iron from used batteries, in which the metals are removed from the leaching solution of black mass in the form of their phosphates by adding H3PO4. EP 4 261 298 also describes a process in which iron and aluminium are isolated during the reprocessing of lithium batteries, wherein the leaching solution is neutralized with phosphoric acid or phosphate and treated with an oxidizing agent. The pH is then increased to 2.0 to 3.5 and the iron and aluminium are precipitated in the form of their phosphates.

[0029] CN 111778401 concerns the processing of lithium batteries in which the separation of nickel, cobalt, and manganese is omitted. Instead, the metals are precipitated with Na₂CO₃ as a mixed carbonate, which is then mixed with lithium carbonate to obtain the desired ratio for a cathode material.

[0030] Current state-of-the-art approaches show that recovering valuable metals from used lithium-ion batteries requires, in some cases, highly complex processes. Furthermore, these processes necessitate a high input of sulfuric acid and sodium hydroxide, ultimately resulting in the formation of equivalent, and therefore large, quantities of the neutral salt sodium sulfate as an undesirable byproduct. Since the market for sodium sulfate, for example as an additive in detergents, is limited, suitable uses for the resulting neutral salt are currently lacking, necessitating its disposal in a complex and costly manner. While initial approaches exist to recover the salt via electro(dia)lytic salt splitting into sulfuric acid and sodium hydroxide, a large-scale industrial process is not yet available and would also require a significant amount of electrical energy.

[0031] BRIEF DESCRIPTION OF THE INVENTION

[0032] Against this background, the present invention aims to demonstrate ways of reducing the amount of neural salts generated during the recovery of valuable metals from black sludge. Furthermore, the process should be as cost-effective as possible, particularly for nickel recovery, and have a low CO2 footprint.

[0033] It was surprisingly found that this problem is solved by a method as defined in independent claim 1. Preferred embodiments of the method according to the invention are set out in the dependent claims.

[0034] The process according to the invention is based on the principle of reactive extraction, whereby the extraction of the desired metal is carried out using other metal ions already present in the solution, thus avoiding the introduction of foreign ions. In this way, the amount of sodium that must be added in conventional processes could be significantly reduced, which in turn also reduced the amount of neutral salt produced.

[0035] Therefore, a first object of the present invention is a method for separating Mn and Co ions from an aqueous starting solution containing Ni ions by reactive extraction, wherein, for the extraction of Mn, the aqueous starting solution is brought into contact with a solvent phase loaded with Co or Ni, and the raffinate obtained is brought into contact with a solvent phase loaded with Ni, wherein the solvent phases each comprise an extraction agent having an affinity A of A(Mn) > A(Co) > A(Ni) towards the metal ions.

[0036] DEFINITIONS

[0037] Within the scope of the present invention, Ni, Co, Mn etc., unless otherwise specified, are understood to mean the respective ion regardless of its oxidation state; metal and metal ion are treated as synonyms within the scope of the present invention unless otherwise specified.

[0038] The solvent phase refers to the non-aqueous phase before extraction.

[0039] The term raffinate refers to the aqueous phase obtained after extraction.

[0040] An extraction agent is an aid used in reactive extraction to transfer a metal ion from the aqueous phase to the organic phase.

[0041] The term extract refers to the non-aqueous phase after extraction.

[0042] In the context of the present invention, affinity is understood to mean the tendency to form a complex between the extraction agent and the metal ion.

[0043] Extraction refers to the process by which the desired metal is transferred from the aqueous phase (SX feed) to the organic phase. During extraction, a solvent phase containing an extraction agent comes into contact with an aqueous phase containing the desired metal (along with impurities). The extraction agent reacts chemically with the metal, forming an organometallic complex that is soluble in the solvent phase and transfers the metal into the extract.

[0044] Scrubbing refers to the selective removal of impurity metals from the extract containing the desired metal (and impurity metals).

[0045] Stripping refers to the process of removing the desired metal from the extract by reversing the chemical extraction reaction through reaction with at least the stoichiometric amount of acid.

[0046] DETAILED DESCRIPTION OF THE INVENTION

[0047] The present invention has surprisingly demonstrated that the extraction process can be carried out using a solvent phase loaded with transition metals, which are arranged downstream of the metal to be extracted in the affinity series with respect to the respective extraction agent, instead of the originally Na-activated extraction solvent. Without being bound to a specific theory, it is assumed that the metal ion in the solvent phase is displaced by the metal ion from the aqueous phase due to its different affinity for the extraction solvent, and is thus transferred into the extract. The process can therefore be described by the following general equation:

[0048] The metal M(i) has a higher affinity for the extraction solvent than the metal M(2).

[0049] Conventional methods still suffer from the problem that sodium sulfate tends to form sparingly soluble double salts with transition metal sulfates. This is addressed in the prior art by working with sufficiently dilute solutions, which ultimately require significant energy expenditure for evaporation.

[0050] This problem does not occur in the process according to the invention, since no Na is introduced into the aqueous main stream.

[0051] In this way, surprisingly effective separation of the metal ions was achieved, just as with conventional activation using sodium, without the need to introduce any foreign metals. For extraction, it is not strictly necessary to use the direct successor in the affinity series, provided that the metal used for extraction has a lower affinity for the extraction solvent than the metal to be extracted.

[0052] In a preferred embodiment, the process according to the invention therefore comprises the following steps, wherein a) an aqueous starting solution containing Ni, Co and Mn is brought into contact with a solvent phase loaded with Co or Ni, the Mn displacing the Co or Ni from the solvent phase and yielding a raffinate containing Ni and Co and a Mn-containing extract (Mn-OP); b) the raffinate from step a) is brought into contact with a solvent phase loaded with Ni, the Co displacing the Ni from the solvent phase and yielding a raffinate containing Ni and a Co-containing extract (Co-OP); and c) at least a part of the raffinate containing Ni is brought into contact with a solvent phase loaded with Na, the Ni displacing the Na from the solvent phase and yielding a raffinate containing Na and a Ni-containing extract (Ni-OP).

[0053] The inventive method is not limited to a single extraction step. Rather, the extractions can be carried out separately from one another. For example, the extraction solvent can be adapted to the metal to be extracted.

[0054] Prior art has proposed using different extraction agents to extract the different metal ions, which, however, obviously complicates the process. Within the framework of the inventive method, this has proven unnecessary in certain cases. Therefore, an embodiment is preferred in which the same extraction agent is used in both solvent phases.

[0055] The extraction agent is characterized by its specific affinity for the metal ions, an affinity which can either be obtained from tables or easily determined by a person skilled in the art. The extraction agent consists of compounds capable of forming organo-metal complexes. For example, longer-chain, particularly branched tertiary, carboxylic acids, sulfonic acids, or derivatives of phosphoric acid, phosphonic acid, or phosphinic acid are suitable. Furthermore, other protic compounds such as oximes and other compounds with sufficient CH acidity are suitable. In a preferred embodiment, the extraction agent is selected from the group consisting of branched long-chain carboxylic acids with at least 5 and preferably a maximum of 10 carbon atoms, sulfonic acids, organophosphonic acids, organophosphoric acids, organophosphoric acids, and oximes, as well as mixtures thereof.Suitable extraction agents, selected according to the metal ions to be extracted, are commercially available, such as neodecanoic acids, marketed under the trade names Versatic acids by Shell or Neo acids by Exxon. Other suitable carriers include dialkylphosphinic acids, marketed under the trade name Cyanex® 272, or phosphate esters such as bis(2-ethylhexyl)phosphate (D2EHPA).

[0056] A variety of water-immiscible organic liquids can be used as solvents for the solvent phase. The solvent is preferably selected from the group consisting of toluene, xylene, kerosene, naphtha, methyl isobutyl ketone, tributyl phosphate, cyclohexane, decane, pyridine, and mixtures thereof. Particularly preferably, the solvent is an aliphatic or aromatic petroleum distillate. Phase modifiers can also be added to the solvent, preferably selected from the group consisting of tributyl phosphate, trimethylphosphine oxide, tributyl phosphine oxide, trihexylphosphine oxide,

[0057] Trioctylphosphine oxide, higher alcohols, and mixtures thereof.

[0058] The process according to the invention starts with an aqueous starting solution containing Ni, Co, and Mn. This starting solution is preferably obtained from a leaching solution, such as that produced during the reprocessing of lithium batteries. In a preferred embodiment, the starting solution is essentially free of lithium, with the lithium content preferably being less than 2 g / l, and particularly preferably less than 1 g / l. The ratio of the metals Ni, Co, and Mn in the aqueous starting solution is determined by the ratio in which they were present in the battery and can, for example, be approximately 1:1:1 or 8:1:1.

[0059] The process according to the invention allows for the effective separation of metal ions from the aqueous phase, which has proven to be just as efficient as separation using a continuously sodium-laden organic phase for the successive extraction of the individual metal ions according to their affinity series. Nevertheless, as is known to those skilled in the art, a certain degree of contamination of the metal-laden organic phases with other metals cannot, by its very nature, be avoided in all cases. Therefore, an embodiment is preferred in which the obtained extracts are at least partially subjected to a purification step to remove undesirable residual contents of other metals. Preferably, this purification is carried out by a scrub treatment, so that the process according to the invention, in a preferred embodiment, further comprises a scrub treatment of the obtained extracts.For this scrub treatment, the extract is preferably brought into contact, at least partially, with an aqueous solution containing the main metal as a salt and / or with a mineral acid, where "main metal" refers to the metal to be extracted. The aqueous metal salt solution obtained during the scrub treatment can then be recycled back into the process before the respective extraction. Scrub steps in the recovery of metals by solvent extraction are well known to those skilled in the art and are generally always used, regardless of how the extraction is carried out chemically or by apparatus. The proportion of metal salt in the aqueous solution and / or mineral acid used for scrubbing depends on the specific case, and the stoichiometric excess of scrub solution can be reduced to a minimum by multi-stage genstream extraction.

[0060] In the process according to the invention, the metals are initially obtained as a metal-loaded extract. To finally isolate the metal, it must therefore be converted back into a water-soluble form. In the process according to the invention, this is achieved by means of a process known to those skilled in the art as stripping. Accordingly, in a preferred embodiment, the metal-loaded extracts, in particular the Mn-OP and the Co-OP, are stripped. According to the invention, this is done by contacting the extracts with a mineral acid, preferably sulfuric acid, to obtain aqueous metal salt solutions. The metal salts, for example in the form of their sulfates, can then be isolated from these aqueous metal salt solutions by crystallization. In this way, highly pure metal salts can be obtained, which can be used for further applications, for example in the production of cathode active materials.The free extraction solvent recovered during this process can be recycled back into the process. To achieve a high metal recovery rate, the stripping process is preferably carried out in a countercurrent flow, particularly in multi-stage applications. Mixer-settler systems, columns, or centrifugal extractors can all be used for this purpose.

[0061] As a further possibility to increase the yield of the individual metals, an embodiment is preferred in which the mineral acid used for stripping also contains a salt of the mineral acid of the metal to be stripped. For example, if sulfuric acid is used, an embodiment is preferred in which the sulfuric acid used for stripping also contains the sulfate of the metal to be stripped.

[0062] The present invention aims to provide a sustainable closed-loop system for separating metal ions from aqueous solutions. Therefore, a preferred embodiment includes a portion of the extract used as a metal-loaded solvent phase for extracting the metal upstream in the affinity series.

[0063] The process according to the invention provides that, for extraction, the aqueous starting solution or the raffinate is brought into contact with a solvent phase containing the extraction agent and a successor of the metal to be extracted from the affinity series. The amount of extraction agent and successor metal is preferably tailored to the amount of metal to be extracted, which can be determined by a person skilled in the art by a simple analysis of the starting solution and / or the raffinate for process control.

[0064] The process according to the invention is particularly intended for the processing of black mass, such as that obtained from the mechanical pretreatment of used lithium-ion batteries. Therefore, an embodiment in which the aqueous starting solution is obtained from black mass is preferred. The aqueous starting solution can, for example, be the leaching solution produced in the battery recovery process. Sulfuric acid has proven particularly effective as a leaching agent in the leaching process; therefore, an embodiment in which the starting solution is a sulfate solution, i.e., an aqueous solution containing nickel sulfate, cobalt sulfate, and manganese sulfate, is preferred. In addition to the aforementioned metal ions Ni, Co, and Mn, the aqueous starting solution can also contain Fe, Al, and Cu, which likewise originate from the underlying black mass.To avoid interference with the separation process according to the invention, it is advantageous to separate these metals beforehand. Therefore, in a preferred embodiment, the process according to the invention comprises a pretreatment of the aqueous starting solution in which any Fe, Al, and / or Cu present are separated. Various methods are suitable for this pretreatment. In a preferred embodiment, the pretreatment comprises treating the starting solution with phosphoric acid, whereby the aforementioned metals are precipitated as their phosphates or, depending on the proportions, as basic phosphates. Preferably, the precipitation takes place at a pH of 2 to 5, more preferably 2.7 to 4.7. The adjustment and / or maintenance of this pH is preferably carried out with nickel hydroxide, cobalt hydroxide, and / or manganese hydroxide, since this avoids the introduction of foreign ions.

[0065] Advantageously, the existing Cu is separated as CuS. Therefore, an embodiment is preferred in which the aqueous starting solution is treated with H2S at pH values ​​below 1 to avoid co-precipitation of CoS and NiS.

[0066] Alternatively, the pretreatment can also include reactive extraction with a solvent phase containing the extraction agent, which is loaded with nickel. Here, too, the inventive principle can be applied: the metal with the higher affinity displaces the metal with the lower affinity and is thus transferred into the organic phase. The resulting extract, loaded with iron, copper, and / or aluminum, can then be stripped to isolate the metals from the aqueous phase. This can be achieved, for example, by electrolyzing the copper from the stripping solution and precipitating aluminum and iron as hydroxides. Since these unwanted metals are now in a sidestream, sodium hydroxide solution can be used directly without introducing sodium into the main aqueous stream.

[0067] In the process according to the invention, a nickel-containing raffinate is obtained, which is at least partially brought into contact with a sodium-loaded solvent phase. The proportion of the raffinate subjected to this treatment preferably corresponds to the amounts of manganese and cobalt initially present in the aqueous starting solution, as well as optionally Cu, Fe, and Al, if the latter are also separated by solvent extraction. The remaining portion of the nickel-containing raffinate, which is sodium-free due to the process according to the invention, can be directly subjected to crystallization to obtain the nickel in commercially available form as nickel sulfate hexahydrate. Alternatively, the nickel sulfate can also be transported further as an aqueous solution and, for example, supplied to manufacturers of pCAMs.

[0068] In cases where the starting solution is a sulfate solution, a NazSC-containing raffinate remains. However, with the process according to the invention, this amount is significantly smaller than in the conventional process, in which all the nickel must be extracted via solvent extraction and therefore consumes at least a stoichiometric amount of sodium hydroxide solution.

[0069] Solid sodium sulfate can be obtained from the sodium sulfate solution by crystallization if a sufficient market exists. This is preferably subjected to electrolysis to recover NaOH and H₂SO₄. While this is not possible in conventional processes due to the large quantities produced, the small amounts produced in the process according to the invention are easily manageable. The recovered NaOH and H₂SO₄ can then be reintroduced into the process. For example, the H₂SO₄ can be used for scrubbing and / or stripping during the process according to the invention, or for leaching the black mass. The recovered NaOH can be used again to produce a Ni-loaded solvent phase.

[0070] For carrying out the process according to the invention, multi-stage mixer-settler systems and columns have proven particularly suitable, with one or more columns operated in countercurrent flow being preferred. In a preferred embodiment, the columns can be equipped with internals to promote phase mixing. Furthermore, the process according to the invention can be carried out in separators and centrifugal extractors. Combinations of the aforementioned systems can also be used.

[0071] The process according to the invention offers an effective and sustainable method for separating Mn, Co, and Ni from aqueous solutions. As part of the overall concept, it integrates into the recycling loop of used lithium-ion batteries, thus making an important contribution to the successful implementation of the mobility transition. Naturally, the process according to the invention can be used not only in battery recycling but also in the primary production of, for example, transition metals.

[0072] The method according to the invention is explained in more detail with reference to the attached figures and examples, which is by no means to be understood as a limitation of the inventive concept.

[0073] EXAMPLES

[0074] The difference between conventional methods and the method according to the present invention can be illustrated by the following equations using the example of co-extraction, where R represents the acid residue of the extraction solvent.

[0075] According to the conventional method, a solvent phase activated with Na is used to extract Co, whereby the Co is converted into extract and an aqueous Na solution remains as the raffinate:

[0076] CO 2+ (aq) + 2 NaR(org) = CoR2(org) + 2 Na + (aq) (3)

[0077] According to the inventive process, a solvent phase loaded with nickel as a direct affinity successor is used for the extraction of the Co:

[0078] CO 2+ (aq) + NiR2(org) — CoR2(org) + Ni 2+ (aq) (4)

[0079] The overall result for co-extraction is therefore as follows:

[0080] The following figures schematically illustrate various separation processes, with the dashed line indicating an organic phase and the solid line an aqueous phase. For the sake of clarity, the scrub steps as they are typically performed have been omitted.

[0081] Figure 1 schematically shows a separation process for Mn, Co, and Ni from an aqueous solution, in which the metals Mn, Co, and Ni are extracted successively from the aqueous phase according to a conventional process concept. A mixture corresponding to the currently used NMC 811 was used as an example. As proposed in the prior art, an extraction solvent activated with sodium, such as DEHPA sodium salt, is used for the extraction.

[0082] In a first step, a starting solution (1) composed of NiSC, MnSC, and CoSC in an 8:1:1 ratio is contacted with a sodium-activated solvent phase (21) to extract the Mn (Al). The sodium-activated solvent phase is an organic phase containing an extraction agent such as DEHPA saponified with sodium according to known methods (D, 20). After separation of the phases, the Mn-containing extract (9) can be subjected to a scrub and subsequent strip treatment (A2) to obtain MnSC (4) as a solution. MnSO4*H2O can then be crystallized from this solution by evaporation if the solution cannot be used directly. The crystallization process is outside the scope of the present invention and is therefore not shown separately in the flow diagram.The resulting raffinate (8), which now contains 1 part NazSC in addition to 8 parts Ni and 1 part Co, corresponding to the separated portion of Mn, is again contacted with a Na-activated solvent phase (22) in a second step to extract Co (Bl). The Co-containing extract (11) obtained after separation of the phases can be subjected to a scrub and subsequent strip treatment (B2) to obtain CoSC (5) as an aqueous solution. As with the manganese, cobalt sulfate, in this case as heptahydrate, can be crystallized from this if required. The remaining raffinate (10), which now contains 2 parts NazSC in addition to the original 8 parts Ni, in an amount corresponding to the extracted amounts of Mn and Co, is also contacted with a Na-activated solvent phase (23) to extract the Ni (CI). Direct crystallization of the NiSC is not possible due to the presence of Na.After the Ni is transferred into the extract (12) and separated (C2), a NazSC solution (7) remains as a raffinate, which must be further processed or disposed of in a complex manner. One possible processing method would be electrolysis to NaOH and H2SO4, but this is not currently available on the required scale.

[0083] Overall, 20 mol of NaOH are required, and mol of Na2SO4 are produced as an unwanted byproduct.

[0084] Figure 2 schematically illustrates the process according to the invention using the example of a solution of NiSO4, CoSO4 and MnSO4, wherein the direct successor in the affinity series is used for separation. i) Separation of Mn

[0085] A starting solution (1) of NiSO4, CoSO4, and MnSO4 in an 8:1:1 ratio is first contacted with a solvent phase (20) containing an extraction solvent, for example, DEHPA, and Co (Al) to transfer the Mn into the organic phase. The resulting Mn-OP extract (9) can be scrubbed with MnSO4 solution to wash out any remaining Co or Ni. The scrubbed wash solution can be combined with the raffinate (8) of the extraction, which now contains only Ni and Co, or recycled back into the process upstream of the mass flow (1). The scrubbed Mn-OP (9) is stripped with sulfuric acid (A2) to extract the Mn, yielding a MnSO4 solution (4). ii) Separation of Co

[0086] The raffinate (8) obtained during the separation of Mn, which contains not only Ni and the original Co but also the Co used for the Mn extraction, is brought into contact (Bl) with a solvent phase (19) containing an extraction solvent, for example DEHPA, and Ni. The extract thus obtained, now loaded with Co (Co-OP, 11), can be scrubbed with CoSO4 solution to remove any entrained Ni. The resulting wash solution can be combined with the raffinate (10) from the extraction, which now contains only Ni, or recycled to an upstream stage. A portion (21) of the Co-OP (11) is treated with sulfuric acid to obtain a CoSO4 solution (5). A portion (20) of the Co-OP (11) is recycled back into the process (Al) for the extraction of Mn from the aqueous phase. iii) Separation of Ni The raffinate (10) obtained during the separation of Co is split.The portion according to material stream (6) can be directly fed to crystallization to obtain NiSO4*6H2O. A portion (12) of the raffinate, corresponding to the amounts of manganese and cobalt originally fed in material stream (1), is recycled into the process and contacted with a Na-activated solvent phase (18) (C) to obtain a Ni-loaded solvent phase (Ni-OP, 19), which is then recycled back into the process for the extraction of Co (Bl). The resulting NazSC solution (7) contains the amounts of neutral salt emitted by the overall process, which are now only 2 mol instead of 10 mol compared to the conventional process. This remaining amount of neutral salt can be separated by electrolysis and recycled back into the process as NaOH and H2SO4.

[0087] Reducing the Na2SO4 load has a significant impact on the economic viability of the process and the global CO2 footprint. Even if a large-scale solution for Na2SO4 splitting were to be implemented, the required electrical energy would be reduced to 20%.

[0088] The regenerated organic phases HR can be reactivated and recycled back into the process. From the resulting pure sulfate solutions, either the metal sulfates can be crystallized or the solutions themselves can be further processed and / or transported.

[0089] Figure 3 schematically shows the process of the inventive method using the example of a solution of NiSC, CoSO4 and MnSC, wherein Ni is used to separate the affinity series instead of its direct successor.

[0090] As in the direct successor separation process, a starting solution (1) of NiSC, CoSO4, and MnSC in an 8:1:1 ratio is first contacted with a solvent phase (20) containing an extraction agent, for example, DEHPA, and nickel (Al) to transfer the Mn into the organic phase. However, in the separation process shown in Figure 3, a Ni-loaded solvent phase (20) is used instead of Co, and not the direct successor. The resulting raffinate (8) contains only CoSO4 and NiSU4, with the Ni content having increased to 9 / 10.

[0091] The further process corresponds to that described in Figure 2. Here too, the process according to the invention generates only 2 parts of Na₂SU₄, which, due to the small quantity, can be processed by electrolysis. Thus, it is also evident here that the amount of neutral salt generated can be significantly reduced by the process according to the invention.

[0092] Figure 4 shows a further embodiment of the process according to the invention, in which the starting solution (1) is first subjected to a pretreatment to separate the Cu and Al contained in the original leaching solution. For this purpose, an aqueous solution (27), such as that obtained from battery reprocessing, is first treated with H₂S (E), whereby Cu precipitates as CuS (29). The H₂SO₄ formed in the remaining solution (30) can be trapped as NiSC by adding Ni(OH)₂ (Fl), so that the solution (31) can be treated with phosphoric acid for further processing (F2) to separate Al as phosphate (33). The solution thus purified can then be fed to the separation step according to the invention as described in Figures 2 or 3, whereby the amount of Na₂SO₄ (34) obtained increases only slightly.The nickel hydroxide used for blunting can be obtained from the raffinate, containing only NiSC, after a corresponding stoichiometric split by precipitation with sodium hydroxide outside the main aqueous stream, so that the main aqueous stream contains more nickel but remains Na-free.

[0093] Figure 5 shows an alternative embodiment of the process according to the invention, in which the metals Cu and Al are separated by means of a solvent reaction using a Ni-containing solvent phase, before the solution thus purified is fed to the separation process shown in Figure 2 or 3.

[0094] As the described process shows, NaOH is only required in the production of the Ni-loaded solvent phase or, if necessary, for the precipitation of small amounts of nickel hydroxide, whereby the amount is significantly reduced from the conventional 11.25 mol to the invention 3.25 mol. Compared to the conventional process, a net saving of 70% can thus be achieved.

[0095] This translates into lower landfill costs or a correspondingly smaller electrolysis process.

[0096] The inventive method enables the establishment of a sustainable separation process that is self-sustaining and thus makes an important contribution to the effective recovery of rare and valuable materials from used Li-ion batteries.

Claims

Patent claims:

1. A process for separating Mn and Co ions from an aqueous starting solution containing Ni ions by reactive extraction, wherein, for the extraction of Mn, the aqueous starting solution is brought into contact with a solvent phase loaded with Co or Ni, and the resulting raffinate is brought into contact with a solvent phase loaded with Ni, characterized in that the solvent phases each comprise an extraction agent having an affinity (A) A(Mn) > A(Co) > A(Ni) towards the metal ions.

2. A method according to claim 1, characterized in that a) an aqueous starting solution containing Ni, Co and Mn is brought into contact with a solvent phase loaded with Co or Ni, wherein Mn displaces the Co or Ni from the solvent phase and a raffinate containing Ni and Co and a Mn-containing extract (Mn-OP) is obtained; b) the raffinate from step a) is brought into contact with a solvent phase loaded with Ni, wherein the Co displaces the Ni from the solvent phase and a raffinate containing Ni and a Co-containing extract (Co-OP) is obtained; and c) at least a part of the raffinate containing Ni is brought into contact with a solvent phase loaded with Na, wherein the Ni displaces the Na from the solvent phase and a raffinate containing Na and a Ni-loaded extract (Ni-OP) is obtained.

3. Method according to at least one of the preceding claims, characterized in that the same extraction agent is used in each case.

4. Method according to at least one of the preceding claims, characterized in that the extraction agent is selected from the group consisting of branched long-chain carboxylic acids with at least 5 and preferably a maximum of 10 carbon atoms, sulfonic acids, organo-phosphonic acids, organo-phosphoric acids, organo-phosphoric acids, oximes and mixtures thereof.

5. A method according to at least one of the preceding claims, characterized in that the solvent phase used is a solvent selected from the group consisting of carbon tetrachloride, toluene, xylene, kerosene, naphtha, tridecanol, methyl isobutyl ketone, tributyl phosphate, cyclohexane, decane, pyridine, dibromoethane and mixtures thereof.

6. Method according to at least one of the preceding claims, characterized in that the method further comprises a scrub treatment of the obtained extracts, wherein for this scrub treatment the extracts are preferably brought into contact at least partially with an aqueous solution containing the main metal as a salt and / or with a mineral acid containing the main metal as a salt.

7. Method according to claim 6, characterized in that the aqueous metal salt solution obtained is recycled back into the process before the respective extraction.

8. Method according to at least one of the preceding claims, characterized in that the metal-loaded extracts are stripped, wherein the extracts are preferably brought into contact with a mineral acid, preferably sulfuric acid.

9. Method according to claim 8, characterized in that the stripping process is carried out in a counter-current flow, in particular a multi-stage flow.

10. Method according to claim 9, characterized in that the stripping process is carried out in mixer-setters or columns.

11. Method according to one or more of claims 9 to 10, characterized in that the mineral acid used for stripping further contains a salt of the mineral acid of the metal to be stripped.

12. Method according to at least one of the preceding claims, characterized in that the metal content in the solvent phase is tailored to the amount of metal to be extracted.

13. Method according to at least one of the preceding claims, characterized in that the initial solution is obtained from black mass.

14. Method according to at least one of the preceding claims, characterized in that the starting solution is a sulfate solution.

15. Method according to at least one of the preceding claims, characterized in that, as part of a preliminary treatment, any Fe, Al and / or Cu that may be present in the initial solution is separated.

16. Method according to claim 15, characterized in that the pretreatment comprises a treatment of the starting solution with phosphoric acid.

17. Method according to claim 16, characterized in that the treatment is carried out at a pH range between 2.0 and 5.0, preferably 2.7 and 4.7, wherein the pH is preferably adjusted by means of nickel hydroxide, cobalt hydroxide and / or manganese hydroxide.

18. Method according to at least one of claims 15 to 17, characterized in that the pretreatment comprises the treatment of the aqueous starting solution with H2S.

19. Method according to claim 17, characterized in that the pretreatment comprises a reactive extraction with a Ni-loaded solvent phase.

20. Method according to at least one of the preceding claims, characterized in that the raffinate containing Na is subjected to electrolysis.

21. A method according to at least one of the preceding claims, characterized in that the method is carried out in a mixer-settler system, columns, separators or centrifugal extractors or combinations thereof.

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