WO2025132785A1

WO2025132785A1 - Recovery of value metals from aqueous solutions

Info

Publication number: WO2025132785A1
Application number: PCT/EP2024/087399
Authority: WO
Inventors: Maximilian RANG; Marc DUCHARDT; Anne-Marie Caroline ZIESCHANG; Fabian Seeler; Wolfgang Rohde; Kerstin Schierle-Arndt; Regina Vogelsang; Andrea Magin; Wolfram WILK; Vincent Smith; Huanjun ZHANG; Bernard Muller
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-12-19
Filing date: 2024-12-19
Publication date: 2025-06-26
Anticipated expiration: 2026-06-19

Abstract

The present disclosure relates to a process for recovering valuable materials from lithium ion battery material, and to a plant for recycling lithium ion battery materials, in particular lithium ion batteries.

Description

Recovery of value metals from aqueous solutions

The project leading to this application has received funding from Bundesministerium fur Wirtschaft und Klimaschutz and State of Brandenburg (DE; FKZ:16BZF101A/B); the applicant bears responsibility for all disclosures herein.

Field of the invention

Background

Lithium ion battery materials are complex mixtures of various elements and compounds. For example, many lithium ion battery materials contain valuable metals such as lithium, aluminum, copper, nickel, cobalt, and/or manganese. It may be desirable to recover various elements and compounds from lithium ion battery materials. For example, it may be advantageous to recover lithium, aluminum, copper, nickel, cobalt, and/or manganese. Accordingly, there is a need for devices and processes for recycling lithium ion battery material.

WO 20231054621 A1 discloses a method for recovering valuable metals from waste lithium ion batteries comprising a dissolution step for dissolving an active material powder obtained by pre-treating the waste lithium-ion batteries in a mineral acid to obtain an acid solution; and a solvent extraction step for separating manganese, cobalt, and nickel, among metals contained in the active material powder, from the acid solution through solvent extraction to obtain a first lithium salt aqueous solution as a residual liquid of the solvent extraction.

WO 2020 / 124130 A1 discloses a method for the recovery of metals from a feed stream containing one or more value metals and lithium. The method comprises subjecting the feed stream to a sulfuric acid leach to form a slurry comprising a pregnant leach solution of soluble metal salts and a solid residue; separating the pregnant leach solution and the solid residue; subjecting the pregnant leach solution to one or more separate solvent extraction steps, wherein each solvent extraction step recovers one or more value metals from the pregnant leach solution, the remaining pregnant leach solution comprising lithium; and recovery of lithium from the pregnant leach solution.

CN 105 591 171 A discloses a recycling method for valuable metals in waste nickel-cobalt-manganese ternary lithium ion batteries. The method comprises the steps that cathode materials are dissolved by adding alkali, and separating is performed to obtain a dissolved solution I and undissolved substances; acidolysis is performed on the undissolved substances to obtain a dissolved solution II, the pH value is adjusted to be alkaline, precipitation is formed, and filtrate I and a precipitate I are obtained; acidolysis is performed on the precipitate I to obtain a dissolved solution III, ammonium hydroxide is added into the dissolved solution III for complexing, after the pH value is adjusted to be alkaline, soluble carbonate is added, and filtering is performed to obtain filtrate II and a precipitate II; soluble carbonate is added into the filtrate II, and heating is performed to obtain a precipitate III; after acidolysis is performed, the pH value is adjusted to be 3.0-3.5, hydrochloride is added to adjust the pH value to be 2.0-3.0, and filtering is performed to obtain filtrate III and a precipitate IV.

CN 113 716626 A discloses a method for preparing a lithium-rich manganese positive electrode material and a high-capacity manganese-series lithium ion sieve by taking a waste lithium ion battery positive electrode material as a raw material. The waste lithium ion battery positive electrode material is a waste lithium manganate battery positive electrode material or a waste ternary nickel cobalt lithium manganate battery positive electrode material. The preparation method comprises six steps of reduction leaching of the waste lithium ion battery positive electrode material, precipitation separation of cobalt oxalate, precipitation separation of nickel hydroxide, co-precipitation separation of manganese carbonate and lithium carbonate, preparation of the lithium positive electrode material and preparation of the high-capacity manganese-series lithium ion sieve.

CN 114 132 909 A discloses a method for recovering pure metal salt from retired lithium manganese iron phosphate battery waste. The method comprises roasting lithium manganese iron phosphate powder in a converter under oxygen to remove an organic solvent; dissolving the fine-ground roasted powder with sulfuric acid, and filtering and separating to remove graphite and other insoluble substances; recovering copper from the filtrate by adding iron powder. After copper is recovered, phosphoric acid is supplemented to the solution according to the measured Fe/P, hydrogen peroxide is added for oxidation, aging is conducted for a long time, ferric phosphate is precipitated, and pure wet ferric phosphate is obtained through filtering, washing, repeated stirring and washing, purification and separation. After iron phosphate has been recovered, a sulfate solution containing aluminum, manganese, cobalt and nickel is precipitated, extracted and purified step by step according to different pH value ranges of aluminum phosphate, manganese carbonate and cobalt and nickel carbonate precipitates by using a metal salt chemical precipitation reaction mechanism. The lithium sulfate solution is purified and concentrated, and precipitated with sodium carbonate to prepare a battery-grade lithium carbonate product.

US 2022/320619 A1 discloses a method for recycling lithium batteries containing the steps: (a) digesting comminuted material, which contains comminuted components of electrodes of lithium batteries, using concentrated sulfuric acid at a digestion temperature (TA) of at least 100° C, so that waste gas and a digestion material are produced, (b) discharging the waste gas and (c) wet chemical extraction of at least one metallic component of the digestion material. It is an object of the present disclosure to provide an improved recycling plant for lithium ion battery materials and an improved recycling process for lithium ion battery materials.

Summary of the invention

The present disclosure provides a continuous process for recovering manganese carbonate from an acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations. The process involves precipitating a mixed metal hydroxide (MHP) from the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, separating solid MHP from a mother liquor, precipitating manganese carbonate from the mother liquor, and recovering manganese carbonate by solid/liquid separation.

The present disclosure also provides a production plant suitable for performing the continuous process of the present disclosure.

Brief description of the drawings

Fig. 1 is a schematic diagram of an exemplary production plant of the present disclosure.

Detailed description

The present disclosure provides a continuous process for recovering manganese carbonate from an acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations.

In some embodiments, the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations has been obtained by leaching lithium ion battery materials with sulfuric acid. Examples of suitable lithium ion battery materials for preparing the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations include black mass, cathode active materials, and mixed metal hydroxides (MHP). The acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations may additionally contain cations of other metals like copper, iron, aluminum, magnesium, calcium, and/or titanium; as well as anions like fluoride and/or phosphate.

In some embodiments of the process of the present disclosure, impurities are precipitated from the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations prior to step a). The precipitation involves the addition of sodium carbonate. In other embodiments, precipitation involves the addition of calcium hydroxide or calcium carbonate instead of sodium carbonate. This offers the advantage of reducing sodium concentration in the mother liquor.

The impurities comprise one or more selected from iron, aluminum, magnesium, calcium, titanium, manganese, residual copper, fluoride, and phosphate. The precipitation involves the addition of a sodium carbonate solution to the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, thereby adjusting the pH value of the solution to a value in the range of from 3.0 to 4.0. In some embodiments of the process, air is injected into the solution to oxidize any Fe(ll) present to Fe(lll). Iron, aluminum, and titanium precipitate from the solution as hydroxides and/or oxide-hydroxides and/or carbonates, fluorides and/or phosphates, and are removed from the mother liquor in a subsequent step by solid-liquid separation, e.g., filtration.

The mother liquor is further processed in a second precipitation step. The precipitation involves the addition of a sodium carbonate solution to the mother liquor obtained in the previous separation step, thereby adjusting the pH value of the solution to a value in the range of from 4.5 to 5.0. Iron, aluminum, and titanium precipitate from the solution as hydroxides and/or oxide-hydroxides and/or carbonates, fluorides and/or phosphates, and are removed from the mother liquor in a subsequent step by solid-liquid separation, e.g., filtration.

The process of the present disclosure comprises a) adding sodium hydroxide to the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, adjusting the pH of the solution to be in a range of from 7.0 to 8.5, and precipitating a mixed metal hydroxide (MHP) from the solution.

The process also comprises b) performing a solid/liquid separation of the mixture obtained in step a) to obtain solid MHP and a mother liquor.

The process further comprises c) adding carbonate anions to the mother liquor obtained in step b), adjusting the pH of the mother liquor to be in a range of from 7.5 to 9.0, and precipitating manganese carbonate from the solution. In some embodiments of the process, sodium carbonate and/or lithium carbonate is added in step c).

The process further comprises d) recovering manganese carbonate from the mixture obtained in step c) by solid/liquid separation.

In some embodiments, the process further comprises e) adding sodium hydroxide to the mother liquor obtained in step d), adjusting the pH of the mother liquor to be in the range of from 10 to 12.5, and precipitating magnesium hydroxide from the mother liquor, and subsequently f) removing solids from the mixture obtained in step e).

In some embodiments, the process further comprises g) adjusting the pH of the mother liquor obtained in step f), to be in a range of from 8.0 to 12.0, e.g., from 8.0 to 10.0, for instance, from 8.0 to 9.0; and subsequently removing lithium ions from the mother liquor by solvent extraction to obtain an aqueous phase depleted of lithium cations and a solvent phase comprising lithium cations; and scrubbing and stripping the solvent phase comprising lithium cations with sulfuric acid to obtain an acidic aqueous solution comprising lithium cations.

Solvent extraction is performed in step g) using an organic solvent suitable for extracting lithium cations from an aqueous solution. Examples of suitable organic solvents include organic solutions comprising an organic diluent, at least one phosphine oxide and at least one proton donating agent, as disclosed in WO 2013/065050 A1 . In some embodiments, the phosphine oxide corresponds to the general formula OPR1R2R3, wherein each of Ri, R₂ and R₃ is independently selected from straight or branched C1-C10 alkyl, straight or branched C2-C10 alkenyl, straight or branched C2-C10 alkynyl, optionally substituted C5-C12 aryl, optionally substituted C4 -C12 heteroaryl; the at least one proton donating agent is selected from the group consisting of straight or branched C1-C10 alcohol, C1-C10 ketone, C1-C10 aldehyde, C3-C20 fatty acid, and any combination thereof; and the molar ratio between said phosphine oxide and an organic acid in said extracting organic solution is in the range of between about 5:1 to about 1 :5. In some embodiments, the solvent used in step h) is a solution of 27 vol% Cyanex® 936P in in dearomatized hydrocarbon fluid (Escaid™ 110).

In some embodiments, the process further comprises h) crystalizing lithium sulfate from the acidic aqueous solution comprising lithium cations obtained in step g).

In some embodiments, the process further comprises i) dissolving the solid MHP obtained in step b) in sulfuric acid; j) removing residual solids from the solution obtained in step i); and optionally, k) adjusting the pH of the solution obtained in step i) to be in the range of from 2 to 4, and removing manganese cations and any impurity cations of the group consisting of Ca, Cu, Zn, and Cd present in the solution by solvent extraction to obtain an aqueous solution depleted of manganese cations and impurity cations.

The solvent comprising manganese cations and impurity cations can be scrubbed and then stripped with sulfuric acid to obtain an acidic aqueous solution comprising manganese cations and impurity cations.

Solvent extraction is performed in step k) using an organic solvent suitable for extracting manganese cations from an aqueous solution. Examples of suitable organic solvents include bis(2-ethylhexyl)phosphate (D2EHPA). In some embodiments, the solvent used in step k) is a solution of 40 vol% bis(2- ethylhexyl)phosphate (D2EHPA) in dearomatized hydrocarbon fluid (Escaid™ 110).

In some embodiments, the process further comprises I), adjusting the pH of the solution obtained in step j), or, if step k) has been performed, the pH of the aqueous solution depleted of manganese cations and impurity cations obtained in step k), to be in the range of from 3 to 6, and subsequently removing cobalt cations from the solution by solvent extraction to obtain an aqueous phase depleted of cobalt cations and a solvent phase comprising cobalt cations; and scrubbing and stripping the solvent phase comprising cobalt cations with sulfuric acid to obtain an acidic aqueous solution comprising cobalt cations. In some embodiments, the pH of the solution is adjusted in step I) to be in the range of from 4.3 to 5.8.

Solvent extraction is performed in step I) using an organic solvent suitable for extracting cobalt cations from an aqueous solution. Examples of suitable organic solvents include phosphinic acid derivatives, e.g., bis-(2,4,4-trimethyl- pentyl) phosphinic acid (Cyanex® 272). In some embodiments, the solvent used in step I) is a solution of 20 vol% bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex® 272) in dearomatized hydrocarbon fluid (Escaid™ 110) containing 1 g/L butylhydroxytoluene (BHT).

In some embodiments, the process further comprises m) crystalizing cobalt sulfate from the acidic aqueous solution comprising cobalt cations obtained in step I).

In some embodiments, the process further comprises n) crystalizing nickel sulfate from the aqueous solution depleted of cobalt cations obtained in step I).

The present disclosure also provides a production plant suitable for performing the process of the present disclosure. The production plant comprises at least one first continuously stirred tank reactor (CSTR) configured to receive an acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations. The first CSTR comprises a dosing device for liquids and heating/cooling means. Suitable continuously stirred tank reactors are known in the art.

The production plant further comprises at least one first solid/liquid separation device configured to receive an effluent of the first CSTR. The at least one first solid/liquid separation device thus is located downstream of the first CSTR. In some embodiments, the first solid/liquid separation device comprises a filter press.

The production plant further comprises at least one second continuously stirred tank reactor (CSTR) configured to receive an effluent of the first solid/liquid separation device. The second CSTR thus is located downstream of the first solid/liquid separation device. The second CSTR comprises a dosing device for liquids and heating/cooling means. Suitable continuously stirred tank reactors are known in the art.

The production plant further comprises at least one second solid/liquid separation device configured to receive an effluent of the second CSTR. The at least one second solid/liquid separation device thus is located downstream of the second CSTR. In some embodiments, the second solid/liquid separation device comprises a filter press.

The production plant further comprises at least one third continuously stirred tank reactor (CSTR) configured to receive an effluent of the second solid/liquid separation device. The third CSTR thus is located downstream of the second solid/liquid separation device. The third CSTR comprises a dosing device for liquids and heating/cooling means. Suitable continuously stirred tank reactors are known in the art. The production plant further comprises at least one third solid/liquid separation device configured to receive an effluent of the third CSTR. The at least one third solid/liquid separation device thus is located downstream of the third CSTR. In some embodiments, the second solid/liquid separation device comprises a filter press.

The production plant additionally comprises a first solvent extraction (SX) unit configured to receive an aqueous effluent of the third solid/liquid separation device. The first SX unit thus is located downstream of the third solid/liquid separation device. The first SX unit comprises an extraction module and a scrubbing and stripping module. In the extraction module of the SX unit, an aqueous solution is extracted with an organic solvent, an aqueous phase and an organic phase being formed in the process. The organic phase is separated from the aqueous phase and transferred to the scrubbing and stripping module, where it is extracted with an aqueous acid. After scrubbing and stripping, the organic phase is cycled back to the extraction module. Suitable solvent extraction (SX) units are known in the art.

The production plant additionally comprises at least one crystallizer for producing a crystalline metal salt from aqueous solutions of the metal salt. Suitable crystallizers are known in the art.

The production plant comprises a first crystallizer configured to receive an aqueous effluent of the scrubbing and stripping module of the first SX unit and to produce crystals of a first metal salt. The first crystallizer thus is located downstream of the first SX unit.

The production plant additionally comprises a fourth continuously stirred tank reactor (CSTR) configured to receive a solid from the first solid/liquid separation device. The fourth CSTR thus is located downstream of the first solid/liquid separation device. The fourth CSTR comprises a dosing device for liquids and heating/cooling means. Suitable continuously stirred tank reactors are known in the art. At least one fourth solid/liquid separation device configured to receive an effluent of the fourth CSTR is arranged downstream of the fourth CSTR.

A second solvent extraction (SX) unit configured to receive an aqueous effluent of the fourth solid/liquid separation device, is present downstream of the third solid/liquid separation device. The second SX unit comprises an extraction module and a scrubbing and stripping module. Suitable solvent extraction (SX) units are known in the art.

A second crystallizer configured to receive an aqueous effluent of the scrubbing and stripping module of the second SX unit and to produce crystals of a second metal salt is located downstream of the second SX unit.

A third crystallizer configured to receive an aqueous effluent of the extraction module of the second SX unit and to produce crystals of a third metal salt also is located downstream of the second SX unit.

Detailed description of the drawing

A schematic diagram of an exemplary production plant of the present disclosure is shown in Fig. 1 .

The production plant comprises a first continuously stirred tank reactor (CSTR) 10 which is configured to receive an acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations 1000. The first CSTR 10 comprises a dosing device for liquids, heating/cooling means, and gas injection means. In the first CSTR 10, an alkaline solution is added to precipitate a mixed hydroxide precipitate from the solution.

The production plant further comprises at least one first solid/liquid separation device 40 which is configured to receive an effluent 1001 of the first CSTR 10. In the at least one first solid/liquid separation device 50, a mixed hydroxide precipitate 5002 is recovered from the effluent 1001 of the first CSTR 10 by solid/liquid separation, e.g., filtration.

The production plant further comprises a second continuously stirred tank reactor (CSTR) 20 which is configured to receive an aqueous effluent 5001 from the at least one first solid/liquid separation device 50. The second CSTR 20 comprises a dosing device for liquids and heating/cooling means. In the second CSTR 20, a carbonate solution is added to precipitate manganese carbonate from the solution.

The production plant further comprises at least one second solid/liquid separation device 60 which is configured to receive an effluent 2001 of the second CSTR 20. In the at least one second solid/liquid separation device 60, manganese carbonate 6002 is recovered from the effluent 2001 of the second CSTR 20 by solid/liquid separation, e.g., filtration.

The production plant further comprises a third continuously stirred tank reactor (CSTR) 30 which is configured to receive an aqueous effluent 6001 from the at least one second solid/liquid separation device 60. The third CSTR 30 comprises a dosing device for liquids and heating/cooling means. In the third CSTR 20, a sodium hydroxide solution is added to precipitate magnesium hydroxide from the solution.

The production plant further comprises at least one third solid/liquid separation device 70 which is configured to receive an effluent 3001 of the third CSTR 30. In the at least one second solid/liquid separation device 70, magnesium hydroxide 7002 is recovered from the effluent 3001 of the second CSTR 30 by solid/liquid separation, e.g., filtration.

The production plant further comprises a first SX unit 90 which is configured to receive an aqueous effluent 7001 of at least one third solid/liquid separation device 70. The first SX unit 90 comprises an extraction module 91 and a scrubbing and stripping module 92. The aqueous effluent 7001 entering the first SX unit 90 is extracted with an organic solvent in the extraction module 91 . The extracted aqueous phase leaves the extraction module 91 as an aqueous effluent 9001. The loaded organic phase is transferred to the scrubbing and stripping module 72, where it is scrubbed and stripped of metal cations with sulfuric acid to produce an acidic aqueous solution comprising the metal cations from the organic phase. The organic phase is recycled to the extraction module 91 , and the acidic aqueous solution comprising the metal cations from the organic phase leaves the scrubbing and stripping module 92 as an aqueous effluent 9002.

The production plant further comprises a first crystallizer 120 configured to receive an aqueous effluent 9002 of the scrubbing and stripping module 92 of the first SX unit 90 and to produce crystals of a first metal salt, e.g., lithium sulfate.

The production plant further comprises a fourth CSTR 40 which is configured to receive a solid 5002 from the at least one first solid/liquid separation device 50. The fourth CSTR 40 comprises a dosing device for liquids and heating/cooling means. In the fourth CSTR 40, an acid is added to dissolve the solid.

The production plant further comprises at least one fourth solid/liquid separation device 80 which is configured to receive an effluent 4001 of the fourth CSTR 40. In the at least one fourth solid/liquid separation device 80, any solids 8002 remaining in the effluent 4001 of the fourth CSTR 40 are removed by solid/liquid separation, e.g., filtration.

The production plant further comprises a second SX unit 100 which is configured to receive an aqueous effluent 8001 of the at least one fourth solid/liquid separation device 80. The second SX unit 100 comprises an extraction module 101 and a scrubbing and stripping module 102. The aqueous effluent 8001 from the at least one fourth solid/liquid separation device 80 is extracted with an organic solvent in the extraction module 101. The extracted aqueous phase leaves the extraction module 101 as an aqueous effluent 10001. The loaded organic phase is transferred to the scrubbing and stripping module 102, where it is scrubbed and stripped of metal cations with sulfuric acid to produce an acidic aqueous solution comprising the metal cations from the organic phase. The organic phase is recycled to the extraction module 101 , and the acidic aqueous solution comprising the metal cations from the organic phase leaves the scrubbing and stripping module 102 as an aqueous effluent 10002.

The production plant further comprises a third SX unit 110 which is configured to receive an aqueous effluent 10001 of the second SX unit 100. The third SX unit 110 comprises an extraction module 111 and a scrubbing and stripping module 112. The aqueous effluent 10001 from the second SX unit 100 is extracted with an organic solvent in the extraction module 111. The extracted aqueous phase leaves the extraction module 111 as an aqueous effluent 11001. The loaded organic phase is transferred to the scrubbing and stripping module 112, where it is scrubbed and stripped of metal cations with sulfuric acid to produce an acidic aqueous solution comprising the metal cations from the organic phase. The organic phase is recycled to the extraction module 111 , and the acidic aqueous solution comprising the metal cations from the organic phase leaves the scrubbing and stripping module 112 as an aqueous effluent 11002.

The production plant further comprises a second crystallizer 130 configured to receive an aqueous effluent 11002 of the scrubbing and stripping module 112 of the third SX unit 110 and to produce crystals of a second metal salt, e.g., cobalt sulfate.

The production plant further comprises a third crystallizer 140 configured to receive an aqueous effluent 11001 of the extraction module 111 of the third SX unit 110 and to produce crystals of a third metal salt, e.g., nickel sulfate. Analytical methods

Residual moisture

Residual moisture was determined by a gravimetric method. The initial weight m_tot of the sample was measured, then the sample was completely dried overnight in an oven at 70°C and 110 mbar pressure and subsequently the dry weight m_dry was determined. Residual moisture was calculated as 1-(mdry/rntot)-

Particle Size Distribution

Particle size distribution was measured by dispersing a sample of the material in water comprising a non-ionic surfactant and measuring the dispersion in a laser diffraction particle size analyzer (Mastersizer® 3000, Malvern Panalytical GmbH, 34123 Kassel, Germany) coupled to an automated dispersion unit (Hydro MV, Malvern Panalytical GmbH, 34123 Kassel, Germany). The sample was dispersed in 120 ml water comprising 1 -2 ml of a polyethylene glycol ether (0.5 wt.-% solution of Lutensol® XL 80, BASF SE), stirring at 3,500 rpm and using 2 min of ultrasound sonification.

Metal content

Elemental analysis of solids was performed using a combination of acid dissolution and alkaline-borate fusion digestion with analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) on an inductively coupled plasma optical emission spectrometer (e.g., Agilent 5110 ICP-OES, Agilent Technologies Germany GmbH & Co. KG, 76337 Waldbronn, Germany).

An aliquot (e.g., about 0.2 g) of the sample material was weighed into a volumetric flask and dissolved under slight heating with 30 ml HCI. After cooling down, the insoluble residue was filtered out and incinerated together with the filter paper in a Pt crucible above an open flame. Subsequently, the residue was calcinated at about 600 °C in a muffle furnace and then mixed with 1 .0 g of a K2CO3-Na₂CO3/Na2B₄O7 flux mixture (4:1 ) and melted above an open flame until a clear melt was obtained. After cooling down, the melt cake was dissolved in deionized (DI) water under slight heating and 12 ml of HCI were added. Finally, the solution was joined to the initial filtered solution in the volumetric flask and topped up to its final volume with DI water. Each sample was prepared in triplicate. A blank sample was prepared in an analogous manner.

The digestion solution was analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES), using external calibration. For some samples, the digestion solution may be diluted before analysis, e.g., adapted to the concentration and calibration range of the respective analyte.

Examples a) MHP-Precipitation

1000 g of a solution (Table 1 , solution 1 ) containing Mn, Li, Ni, Co and Ca was heated to 43°C. The mixture was treated with a NaOH-solution until a pH of 8 was reached, during which precipitation of a green solid occurred. After a total reaction time of 180 min, the suspension was filtered off and the solid was washed. A moist solid residue (I) and a filtrate (2) could be obtained with a yield of 425.8 and 1230 g, respectively. Residual moisture and particle size distribution of the solid (I) were determined to be 58.6% and D(50) = 13.4 pm, respectively. The filtrate (2) contained 1 .5, 3.2 and 49.4% of the total amount of Ni, Co and Mn, respectively. b) MnCOs-Precipitation

200 g of a solution with a pH of 6 (Table 1, solution 2) containing Mn, Ca in the ratio of 55.8 to 1 .0 by weight and other elements typically found in battery waste streams (e.g. Li, Ni and Co) was heated to 43°C. The mixture was subsequently treated with a Na₂CO3-solution until a pH value of 8.4 was reached, during which precipitation of a colorless to pale pinkish solid occurred. After a total reaction time of 113 min, the suspension was filtered off and the solid was washed. A moist solid residue (II) and a filtrate (3) could be obtained with a yield of 7.7 and 416.4 g, respectively. Residual moisture and particle size distribution of the solid (II) were determined to be 20.8% and D(50) = 24.4 pm, respectively. A Mn:Ca-ratio of 95.1 :1 in the final product showed that the Ca-content could be reduced by 39.7%. The final Mn-yield amounted to 99.83% (2.4 g). The metal contents of solutions 1-3, as determined by ICP-OES, are summarized in Table 1. The solids obtained in the Example were dried, and their metal content was determined by ICP-OES, The results are given in Table 2.

In total, 99.8% Ni, 99.9%% Co and 99.8% Mn were recovered from solution 1 by these two steps.

Table 1 Metal content of solutions as determined by ICP OES

Solution Mn Li Ca Ni Co

1 1.30% 0.64% 0.16% 2.80% 1.20%

2 0.67%% 0.46% 0.012% 0.048% 0.044%

3 0.001 % 0.43% 0.005% 0.003% < 0.001 %

Table 2 Metal content of the solids obtained as determined by ICP-OES

Solid(dry) Mn Li Ca Ni Co Na

I 3.8% 1.20% 0.03% 17.6% 7.50% 8.20%

II 39% 0.42%% 0.41 % 2.30% 2.40% 3.60%

Determination of Metal Yields

Metal yields were determined using elemental contents determined by ICP- OES. If not stated otherwise, metal yields were determined using the elemental content determined in the dry solids

The following formulas were utilized:

( 1 )

m(E_pc) — E_ICP-PC * m(F C) ( 2 ) wherein

E denotes a given element, FC denotes the dry solid, EICP-FC is the determined percentage-based content in the dry solid, m(FC) is the mass of the dry solid, m(E_Fc) is the weight content of the element in the dry solid, m(E_Max) is the total amount of an element found in all product fractions, and

MY_E is the metal yield of the respective element.

List of reference numerals

10 First CSTR

20 Second CSTR

30 Third CSTR

40 Fourth CSTR

50 First solid/liquid separation unit

60 Second solid/liquid separation unit

70 Third solid/liquid separation unit

80 Fourth solid/liquid separation unit

90 First SX unit

91 Extraction module of first SX unit

92 Scrubbing and stripping module of first SX unit

1000 Second SX unit

101 Extraction module of second SX unit

102 Scrubbing and stripping module of second SX unit

110 Third SX unit

111 Extraction module of third SX unit

112 Scrubbing and stripping module of third SX unit

120 First crystallizer

130 Second crystallizer

140 Third crystallizer

1000 Acidic aqueous solution comprising Ni, Co, Mn, and Li cations

1001 Effluent of first CSTR

2001 Effluent of second CSTR

3001 Effluent of third CSTR

4001 Effluent of fourth CSTR

5001 Aqueous effluent of first solid/liquid separation unit

5002 Solids (mixed hydroxide precipitate)

6001 Aqueous effluent of second solid/liquid separation unit

6002 Solids (manganese carbonate)

7001 Aqueous effluent of third solid/liquid separation unit

7002 Solids (magnesium hydroxide) 8001 Aqueous effluent of fourth solid/liquid separation unit

8002 Solids

9001 Aqueous effluent of extraction module of first SX unit

9002 Aqueous effluent of scrubbing and stripping module of first SX unit 10001 Aqueous effluent of extraction module of second SX unit

10002 Aqueous effluent of scrubbing and stripping module of second SX unit

11001 Aqueous effluent of extraction module of third SX unit

11002 Aqueous effluent of scrubbing and stripping module of third SX unit

Claims

1 . A continuous process for recovering manganese carbonate from an acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, the process comprising a) adding sodium hydroxide to the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, adjusting the pH of the solution to be in a range of from 7.0 to 8.5, and precipitating a mixed metal hydroxide (MHP) from the solution, b) performing a solid/liquid separation of the mixture obtained in step a) to obtain solid MHP and a mother liquor, c) adding carbonate anions to the mother liquor obtained in step b), adjusting the pH of the mother liquor to be in a range of from 7.5 to 9.0, and precipitating manganese carbonate from the solution, d) recovering manganese carbonate from the mixture obtained in step c) by solid/liquid separation.

2. The process of claim 1 , wherein sodium carbonate and/or lithium carbonate is added in step c).

3. The process of claim 1 or 2, further comprising e) adding sodium hydroxide to the mother liquor obtained in step d), adjusting the pH of the mother liquor to be in the range of from 10 to 12.5, and precipitating magnesium hydroxide from the mother liquor, f) removing solids from the mixture obtained in step e). g) adjusting the pH of the mother liquor obtained in step f), to be in a range of from 8.0 to 12.0; and subsequently removing lithium ions from the mother liquor by solvent extraction to obtain an aqueous solution depleted of lithium cations and a solvent comprising lithium cations; and scrubbing and stripping the solvent comprising lithium cations with sulfuric acid to obtain an acidic aqueous solution comprising lithium cations.

4. The process of claim 3, further comprising h) crystalizing lithium sulfate from the acidic aqueous solution comprising lithium cations obtained in step g).

5. The process of any one of claims 1 to 4, further comprising i) dissolving the solid MHP obtained in step b) in sulfuric acid, j) removing residual solids from the solution obtained in step i), k) optionally, adjusting the pH of the solution obtained in step j) to be in the range of from 2 to 4, and removing manganese cations and any impurity cations of the group consisting of Ca, Cu, Zn, and Cd present in the solution by solvent extraction to obtain an aqueous solution depleted of manganese cations and impurity cations.

6. The process of claim 5, further comprising l) adjusting the pH of the solution obtained in step j) or, if step k) has been performed, the solution obtained in step k), to be in the range of from 3 to 6, and subsequently removing cobalt cations from the solution by solvent extraction to obtain an aqueous solution depleted of cobalt cations and a solvent comprising cobalt cations; and scrubbing and stripping the solvent comprising cobalt cations with sulfuric acid to obtain an acidic aqueous solution comprising cobalt cations.

7. The process of claim 4 or 5, further comprising m) crystalizing cobalt sulfate from the acidic aqueous solution comprising cobalt cations obtained in step I).

8. The process of any one of claims 4 to 6, further comprising n) crystalizing nickel sulfate from the aqueous solution depleted of cobalt cations obtained in step I).

9. The process of claim 6, wherein the solvent used in step I) is a solution of 20 vol% bis-(2,4,4-trimethylpentyl) phosphinic acid in dearomatized hydrocarbon fluid containing 1 g/L butylhydroxytoluene.

10. The process of any one of claims 1 to 9, wherein the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations has been obtained by leaching lithium ion battery materials with sulfuric acid.

11. The process of claim 10, wherein the lithium ion battery materials are selected from the group consisting of black mass, cathode active materials, and mixed metal hydroxide precipitates.

12. The process of any one of claims 1 to 11 , wherein impurities comprising one or more selected from iron, aluminum, magnesium, calcium, titanium, manganese, copper, fluoride, and phosphate are precipitated from the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations prior to step a) by addition of sodium carbonate and/or calcium hydroxide and/or calcium carbonate to the acidic aqueous solution comprising nickel, cobalt, manganese, and lithium cations, thereby adjusting the pH value of the solution to a value in the range of from 3.0 to 4.0, and removing the precipitate from the mother liquor in a subsequent step by solid-liquid separation.

13. The process of claim 12, wherein the mother liquor is further processed in a second precipitation step involving the addition of a sodium carbonate solution to the mother liquor obtained in the previous separation step, thereby adjusting the pH value of the solution to a value in the range of from 4.5 to 5.0, and removing the precipitate from the mother liquor in a subsequent step by solid-liquid separation.

4. A production plant comprising

1 ) a first continuously stirred tank reactor (CSTR) (10) configured to receive an acidic aqueous solution (1000) comprising nickel, cobalt, manganese, and lithium cations, the CSTR (10) comprising i. a dosing device for liquids, ii. heating/cooling means,

2) at least one first solid/liquid separation device (50) configured to receive an effluent (1001 ) of the first CSTR (10),

3) a second continuously stirred tank reactor (CSTR) (20) configured to receive an effluent (5001 ) from the first solid/liquid separation device (50), the second CSTR (20) comprising i. a dosing device for liquids, ii. heating/cooling means,

4) at least one second solid/liquid separation device (60) configured to receive an effluent (2001 ) of the second CSTR (20),

5) a third continuously stirred tank reactor (CSTR) (30) configured to receive an effluent (6001 ) from the second solid/liquid separation device (60), the third CSTR (30) comprising i. a dosing device for liquids, ii. heating/cooling means,

6) at least one third solid/liquid separation device (70) configured to receive an effluent (3001 ) of the third CSTR (30),

7) a first solvent extraction (SX) unit (90) configured to receive an aqueous effluent (7001 ) of the third solid/liquid separation device (70), the first SX unit (90) comprising i. an extraction module (91 ), ii. a scrubbing and stripping module (92).

8) a first crystallizer (120) configured to receive an aqueous effluent (9002) of the scrubbing and stripping module (92) of the first SX unit (90) and to produce crystals of a first metal salt.

9) a fourth continuously stirred tank reactor (CSTR) (40) configured to receive a solid (5002) from the first solid/liquid separation device (50), the fourth CSTR (40) comprising i. a dosing device for liquids, ii. heating/cooling means,

10) at least one fourth solid/liquid separation device (80) configured to receive an effluent (4001) of the fourth CSTR (40),

11 ) a second solvent extraction (SX) unit (100) configured to receive an aqueous effluent (8001 ) of the fourth solid/liquid separation device (80), the second SX unit (100) comprising i. an extraction module (101 ), ii. a scrubbing and stripping module (102),

12) a third solvent extraction (SX) unit (110) configured to receive an aqueous effluent (10001) of the extraction module (101 ) of the second SX unit (100), the third SX unit (110) comprising i. an extraction module (111 ), ii. a scrubbing and stripping module (112),

13) a second crystallizer (130) configured to receive an aqueous effluent (11002) of the scrubbing and stripping module (112) of the third SX unit (110) and to produce crystals of a second metal salt,

14) a third crystallizer (140) configured to receive an aqueous effluent (11001 ) of the extraction module (111 ) of the third SX unit (110) and to produce crystals of a third metal salt.