TECHNICAL FIELD

The present invention relates to processes for leaching cobalt from solid materials having a high Co(III) content, such as roasted materials containing cobalt and tungsten. Specifically, the present invention employs sulphuric acid based leaching solutions to form cobaltous sulphate solutions.

INTRODUCTION

Cobalt has gained much interest in recent decades, primarily for its industrial use in lithium-ion batteries and in wear-resistant, high-strength alloys. Further, cobalt has been used as colouring agent in glasses and ceramics and as drying agent in paints and varnishes. In order to meet the rising demand for cobalt, improved methods for the recovery of cobalt from waste materials or from ores are desired.

P. T. Ntakamutshia et al. describe optimized methods for agitation and column leaching of oxidised copper-cobalt ores under reducing conditions. Such methods employ reducing agents such as SO2, in situ generated by reaction of sulphuric acid and metabisulphite, to reduce any Co(III) which may be present, Minerals Engineering, Volume 111, September 2017, Pages 47-54, https://doi.org/10. 1016/j.mineng.2017.06.001. The paper presents and discusses the effect of recirculation of the leach liquor after pH readjustment to 1.5 on the minimisation of unreacted SO2 entrained in the leach liquor, sulphuric acid consumption; and the overall improvement of copper and cobalt extraction yields.

Cobalt-containing solid materials which also comprise further impurities such as tungsten, are often roasted before leaching cobalt and optionally other valuable materials, such as reported by Yang et al., Met. Mater. Int., Volume 22, No. 5 (2016), Pages 897-906 DOI: 10.1007/S12540-016-6060-3. Such roasting processes aim to oxidise tungsten, yet inevitably enhance the amount of Co(III) due to oxidation of cobalt. The formation of Co(III) is, however, disadvantageous since, consequently, enhanced amounts of reducing agents, such as SO2, are required for the formation of Co(II) in the leaching process. CN 103 757 355 discloses a leaching method of a nickel cobalt lithium manganate waste battery positive electrode material, the method comprising the steps of: putting a positive-negative electrode mixed material subjected to roasting pre-treatment separated from nickel cobalt lithium manganate waste batteries into a pressure-resistant sulfuric-acid-corrosion-resistant container, pumping sulfuric acid into the container, sealing the container, and introducing SO2 to perform leaching. High leaching rates were achieved for all metals present in the waste battery material, i.e., typically higher than 98% leaching was achieved for Ni, Co, Li, Cu, Al and Mn.

In search for alternative processes which would fulfil the requirements of a high recovery rate for Co, and preferably also other metals, from materials comprising Co ³⁺ , W. Xuan et al. found that the use of a leaching solution comprising 4N HCI affords a desired effectivity, RSC Advances, Volume 9, 2019, Pages 38612-38618, DOI : 10.1039/C9RA06686A. However, such processes have the disadvantage that CI2 gas may be formed during processing, which forms a safety risk. Also, the use of chlorine in the process is not preferred since, chloride salts require further purification steps to obtain a satisfactorily pure end product. It is thus a further object of the present invention to provide a process which is safe, preferably without the requirement of further safety procedures, especially without the need for further purification steps. Furthermore, the present inventors found that poor results were obtained for the leaching of most other metals, with the exception Co, Ni, Mn, Al and Zn. Therefore, it is also an object of the present invention to provide methods which allow for the co-leaching of other metals of industrial interest, such as - but not limited to - W.

It is thus an object of the present invention to provide new processes for recovering cobalt in high yield and efficiency from solid materials such as ores and waste materials. Preferably, such processes allow for a roasting operation prior to the recovery of cobalt. Hence, it is also an object to provide processes which efficiently process source materials which may comprise Co(III) in considerable amounts. Furthermore, it is an object of the present invention to reduce or even to avoid entirely the use of reducing agents to compensate for the presence of Co(III) in said materials. Also, it is an object of the present invention to provide new methods which allow for the selective leaching of one or more compounds from the solid material comprising cobalt. SUMMARY

The current invention provides in a solution for at least one of the above mentioned problems by providing processes for leaching cobalt from solid materials, as described in claim 1.

This is advantageous because good leaching and high Co recovery is achieved even if the solid material comprises substantial amounts of Co ³⁺ , provided that a leaching solution comprising at least 2.0 M sulphuric acid is used. It was found that a recovery rates higher than 80% of Co were typically achieved, even in absence of a reducing agent. Higher concentrations of sulphuric acid are preferred, even up to 5 M sulphuric acid, or even 6 M sulphuric acid. This allows for new leaching strategies and pretreatment procedures, including the use of a much more diverse feed material in terms of composition of metals and oxidation states.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

As used herein, the following terms have the following meanings:

"A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

"About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of +/- 20% or less, preferably +/-10% or less, more preferably +/-5% or less, even more preferably +/-1% or less, and still more preferably +/-0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

"Comprise," "comprising," and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints. All percentages are to be understood as percentage by weight, abbreviated as "wt.%" or as volume per cent, abbreviated as "vol.%", unless otherwise defined or unless a different meaning is obvious to the person skilled in the art from its use and in the context wherein it is used.

In the context of the present invention, the term "solid material" must be construed as a feed or a feed material, which is being fed to the leaching step in the process.

In the context of the present invention, the term "total weight of said solid material" is to be considered as the dry weight of said solid material, i.e. excluding any water or other volatiles, whereby volatiles are considered as elements or compounds having a boiling temperature up to 360°C.

The term "cobaltous" is to be construed as referring to "consisting of cobalt in oxidation state 2 + ."

The term "hard metal scrap" is to be understood as scrap metal comprising two or more metals such as cobalt, nickel, iron, tungsten, manganese, etc. as well as alloys comprising two or more metals. The aforementioned metals are not limited to the metallic oxidation state, but can also have higher oxidation states.

In a first aspect, the present invention provides a process for recovering cobalt from a solid material, comprising the steps of: i. leaching a solid material comprising 1 to 75 wt.% cobalt, relative to the total weight of said solid material, wherein the weight ratio of Co ³⁺ , relative to the total weight of cobalt in said solid material, is at least 0.1, with a leaching solution comprising sulphuric acid in a concentration of 2.0 M or more, thereby obtaining a leach liquor comprising cobaltous sulphate and a solid residue comprising insoluble materials; and ii. separating said leach liquor from said solid residue.

The inventors have found that good leaching and high Co recovery is achieved even if the solid material comprises Co ³⁺ , provided that a leaching solution comprising more than 2.0 M sulphuric acid is used. It was found that a recovery rates higher than 80% of Co were typically achieved, even in absence of a reducing agent. In contrast, recovery rates for similar processes having a leaching solution comprising less than 2.0 M sulphuric acid, such as 1.0 M sulphuric acid, showed a distinctly lower recovery rate of about 50% of Co. Higher concentration of sulphuric acid are preferred. Hence, contrary to what may be expected from the prior art, it was found that the presence of Co ³⁺ , as such, does not prevent leaching of cobalt from the solid material. This allows for new leaching strategies and pre-treatment procedures, including the use of a much more diverse feed material in terms of composition of metals and oxidation states.

The inventive process provides the advantage that a process is provided for recovering cobalt in high yield and efficiency from solid materials such as ores and waste materials. Specific cobalt-containing solid materials are hard metal scrap and battery waste materials. The solid materials may be roasted before the leaching operation, resulting in higher amounts of Co(III) in the solid material, without substantially reducing the effectivity of the leaching process, i.e. high recovery of Co(III) is still achieved. That the presence of Co(III) is not detrimental to the recovery rate of the process allows to conceive novel process pathways. Specifically, it can be contemplated that a solid feed material comprising tungsten, e.g. tungsten carbide, is calcined or roasted under oxidative conditions, and that the formed tungsten oxide WO3 is subsequently dissolved in an aqueous alkaline solution, e.g. a concentrated NaOH solution. Hence, not only improved recovery of Co is achieved, but also an improved recovery of other valuable metals is enabled in the same operation. Furthermore, the inventive process allows for processes which proceed in the absence of one or more reducing agents entirely, or proceed in the presence of a lower amount of one or more reducing agents, allow for a reduced use of reducing agents, or even allow for a process without the need for reducing agents entirely.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said leaching solution comprises sulphuric acid in a concentration of at least 2.3 M, preferably at least 2.5 M, at least 2.8 M or even at least 3.0 M sulphuric acid. It was found that higher amounts of sulphuric acid ensure a more straightforward conversion and consequently higher recovery of Co. In addition, it was found that the addition of reducing agents to the leaching reaction is not required to achieve high conversion and high recovery of Co. Preferably, said leaching solution comprises sulphuric acid in a concentration of at most 6 M, preferably at most 5 M sulphuric acid, more preferably at most 4.5 M sulphuric acid and even more preferably at most 4 M sulphuric acid. Preferably, said sulphuric acid is the sole acid used in said leaching solution. It was surprisingly found that improved selectivity for Co versus Mn was found at the optimized concentration of sulphuric acid.

In a preferred embodiment, the inventive process further comprises the step of neutralizing said leach liquor comprising cobaltous sulphate, either before or after separating said leach liquor from said solid residue. Preferably, said leach liquor comprising cobaltous sulphate is neutralized before or after separating said leach liquor from said solid residue, and more preferably said leach liquor comprising cobaltous sulphate is neutralized prior to separating said leach liquor from said solid residue. Preferably, said leach liquor is neutralized to a pH between 1 and 6.3, preferably between 2 and 4 and more preferably to a pH of about 3.

Since the addition of further reducing agents is not mandatory to obtain high conversions and yields, the present invention provides in a specific embodiment the process according to the first aspect of the invention whereby no reducing agent are added during the leaching of said solid material, i.e. step i. Importantly, it is observed that under such circumstances the leaching of materials comprising cobalt, nickel and manganese show selectivity towards the leaching of cobalt and nickel, while the leaching of manganese is suppressed. Thus, selective leaching of cobalt and nickel is realized. Moreover, it was found that tungsten, if present in the solid material, Preferably, no reducing agent is used during the major part of the leaching reaction, i.e., during the period for leaching more than 50 wt.% of the amount of Co in said solid material to be leached.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said leaching solution comprises sulphuric acid in a concentration of 3.0 to 4.0 M sulphuric acid. Most preferably, said leaching solution comprises sulphuric acid in a concentration of about 3.0, 3.2, 3.4, 3.6, 3.8 or 4.0.

Preferably, the present invention provides a process according to the first aspect of the invention, wherein said solid material comprises cobalt in an amount up to 75 wt.% cobalt, relative to the total weight of said solid material, preferably in an amount up to 70 wt.% cobalt, and more preferably in an mount up to 65 wt.% cobalt. Preferably, said solid material comprises cobalt in an amount up to 60 wt.% cobalt, preferably in an amount up to 55 wt.% cobalt, and more preferably in an mount up to 50 wt.% cobalt. Preferably, said solid material comprises at least 5 wt.% cobalt, more preferably at least 10 wt.% cobalt, and even more preferably at least 15 wt.% cobalt. Preferably, said solid material comprises 15 to 40 wt.% cobalt, and more preferably 25 to 40 wt.% cobalt. Most preferably, said solid material comprises 25 wt.%, 30 wt.%, 35 wt.%, or 40 wt.% cobalt, or any amount there in between. Albeit that a preferred amount of cobalt in said solid material is indicated, leaching of solid materials comprising lower or higher amounts of cobalt is also possible. Such processes may have a reduced efficiency, or may require further process measures to ensure high recovery rates for cobalt.

Preferably, the present invention provides a process according to the first aspect of the invention, wherein said solid material comprises 1 to 40 wt.% manganese, relative to the total weight of said solid material, preferably 5 to 30 wt.% manganese and more preferably 5 to 20 wt.% manganese. It was surprisingly found that a selective leaching of cobalt from a manganese-containing solid material is achieved.

Preferably, the present invention provides a process according to the first aspect of the invention, wherein the total amount of cobalt and nickel in said solid material is at least 80 wt.%, relative to the total weight of metals in said solid material, preferably at least 90 wt.%. Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material is roasted prior to leaching with said leaching solution. The roasting process may comprise a sequential washing and drying of the solid source material prior to the roasting. Preferably, distilled water is used for the washing. Without introducing any limitations to the invention, the roasting temperature may be between 500°C and 600°C, and the roasting time may be between 4 and 8 hours; the roasting atmosphere may be an air atmosphere. After roasting, the process may comprise grinding of the roasted product.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material is roasted, prior to said leaching step, to increase the content of Co ³⁺ , relative to the total weight of cobalt in said solid material, to a ratio of at least 0.1, preferably to a ratio of at least 0.15, at least 0.20, at least 0.25 or even at least 0.30. Said weight ratio may be up to 1.0. Preferably, said weight ratio is not more than 0.90, preferably not more than 0.80, not more than 0.70, or not more than 0.60. More preferably, said weight ratio is about 0.30, about 0.35, about 0.40, about 0.45, about 0.50, about 0.55, or about 0.60, or any value there in between.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material comprises 5 to 45 wt.% cobalt, relative to the total amount of metals in said solid material.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material comprises Co ³⁺ in an amount of at least 0.05 and not more than 0.95, relative to the total amount of cobalt in said solid material. Preferably, the present invention provides a process according to the first aspect of the invention, whereby said weight ratio of Co ³⁺ in said solid material relative to the total amount of cobalt in said solid material, is at least 0.1 : m Co ³⁺

- > 0.1 m °total

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said weight ratio of Co ³⁺ in said solid material relative to the total amount of cobalt in said solid material, is at least 0.15, at least 0.20, at least 0.25 or even at least 0.30. Preferably, said weight ratio is not more than 0.90, preferably not more than 0.80, not more than 0.70, not more than 0.60 or even not more than 0.55. More preferably, said weight ratio is about 0.30, about 0.35, about 0.40, about 0.45 or about 0.50, or any value there in between.

Preferably, said solid source material comprises tungsten in an amount of 0.1 to 15 wt.% of tungsten, relative to the total amount of metals in said solid source material. Such solid source materials may comprises tungsten carbide and/or tungsten oxide. Solid source materials comprising an amount of tungsten provide the advantage that valuable metals such as cobalt and tungsten can be leached simultaneously. Preferably, said solid source material comprises 0.5 to 5 wt.% tungsten, relative to the total amount of metals in said solid material, and more preferably 1 to 5 wt.% tungsten. Most preferably, said solid source material comprises 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, or 5 wt.% tungsten, or any amount there in between. Preferably, said tungsten is comprised in said solid source material in the form of WO3, and more preferably the amount of W ⁶⁺ , relative to the total amount of W in said solid material, expressed as weight-ratio, is at least 0.70, preferably at least 0.75, more preferably at least 0.80 and even more preferably at least 0.85. Most preferably, the amount of W ⁶⁺ , relative to the total amount of W in said solid material, expressed as weightratio, is at least 0.90, at least 0.95 or even at least 0.98.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material which is subjected to said leaching step is obtained from a purification process whereby a solid source material comprising tungsten is roasted and subsequently subjected to dissolution process for dissolving tungsten. Preferably, said dissolution process is achieved by contacting the roasted solid source material with a concentrated alkaline solution, such as a NaOH solution.

Preferably, said solid source material is roasted, prior to said leaching step, at a temperature of at least 600°C. More preferably, said solid source material is roasted at a temperature of at least 625°C, at least 650°C, at least 675°C, or even at least 700°C. Preferably, said solid source material is roasted, prior to said leaching step, at a temperature of less than 1000°C. More preferably, said solid source material is roasted at a temperature of less than 900°C, less than 875°C, less than 850°C, or even less than 825°C. Most preferably, said solid source material is roasted at a temperature of about 700°C, 720°C, 740°C, 760°C, 770°C, 800°C, or 820°C, or any temperature there in between. Preferably, said solid source material is roasted for a period of 1 to 24 hours, more preferably for a period of 2 to 16 hours, even more preferably for a period of 3 to 12 hours and most preferably for a period of 4 to 10 hours, and especially preferred for a period of 4, 6, 8, or 10 hours, or any period there in between. Preferably, said solid source material is roasted in an oxygen-con- taining atmosphere, such as air, oxygen-enriched air, or oxygen. Roasting of said solid source material allows for the oxidation of W, which ensures a higher recovery of W in the subsequent dissolution process step. The roasting step inevitably results in higher amounts of Co(III), and inevitably results in a higher weight ratio of Co ³⁺ , relative to the total amount of cobalt in said solid material, also referred to as said solid feed material.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said leaching solution has a pH lower than -0.3, whereby said pH is determined by adding a saturated oxalate solution for binding metal ions in metal oxalate complexes, and subsequently titrating the obtained solution. Preferably, said pH is between -0.30 and -0.70, and more preferably, said pH is between -0.48 and -0.60.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material is contacted with said leaching solution in presence of a reducing agent. Said reducing agent may be selected from the group consisting of SO2, and metal or metal alloy powders containing at least one of cobalt, iron and nickel, or any other metal with a lower reduction potential compared to Co(II).

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said reducing agent is SO2. In one embodiment of the present invention, SO2 is the sole reducing agent used in the process. In such cases, SO2 may be used in a stoichiometric amount, relative to the amount of Co ³⁺ . Ensuring the presence of a reducing agent resulted in a higher recovery rate for Co.

Preferably, the present invention provides a process according to the first aspect of the invention, further comprising the step of neutralizing said leach liquor with a cobalt-containing neutralizing agent, such as cobalt hydroxide, metallic cobalt, nickel-manganese-cobalt oxide. Preferably, said leach liquor comprising cobaltous sulphate is neutralized before or after separating said leach liquor from said solid residue, and more preferably said leach liquor comprising cobaltous sulphate is neutralized prior to separating said leach liquor from said solid residue. Preferably, said leach liquor is neutralized to a pH between 1 and 6.3, preferably between 2 and 4 and more preferably to a pH of about 3.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material is contacted with said leaching solution at a temperature between 65°C and 100°C, at a temperature between 75°C and 95°C, and more preferably at a temperature of about 75°C, 80°C, 85°C, 90°C, or 95°C, or any temperature there in between. Preferably, the leaching step is performed for a period of 15 minutes to 48 hours, more preferably for a period of 1 to 24 hours, even more preferably of 2 to 16 hours or even of 4 to 12 hours. Most preferably, said leaching step is performed for a period of 4 hours, 6 hours, 8 hours, 10 hours or 12 hours, or any period there in between.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material additionally comprises iron and/or nickel. Said solid material may further comprise copper, manganese, tantalum and/or chromium.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material comprises a nickel-manganese-cobalt oxide, such as a lithium nickel-manganese-cobalt oxide.

Preferably, the present invention provides a process according to the first aspect of the invention, whereby said solid material comprises hard metal scrap or battery waste materials. EXAMPLES

The following examples are intended to further clarify the present invention, and are nowhere intended to limit the scope of the present invention.

EXAMPLE 1

A solid material comprising Co is provided according to the composition detailed in Table 1. The fraction of Co ³⁺ , relative to the total amount of Co in said solid feed material, is 0.46.

Table 1. Composition of solid feed material.*

Co Ni Cu Mn Ta W Cr Fe

51 7 1275 1/7 0?8 1/7 3?5 5 6 12/7

* expressed in wt.%, relative to total dry weight of said solid material.

45 kg of solid material having a composition as depicted in Table 1 is added to 200 L of a 5 M sulphuric acid leaching solution. Process conditions are according to Table 2. Reaction temperature is maintained at about 80°C. Recovery yields for Co are reported in Table 2.

Table 2. Recovery yields for Co in processes according to Example 1.

Processing time (h) Recovery Co (%) ^a

EX 1.1 2 88

EX 1.2 5 94

EX 1.3 8 96

EX 1.4 8 + 3 (SO2) ^b 99 ^a percentage of Co recovered, relative to the Co content of said solid feed material. ^b processing time of 8 hours in 5 M sulphuric acid and subsequently 3 hours in presence of SO2. The leaching solution is purged with SO2 at an average flow rate of about 750 L/h.

The leachate is further neutralised using a solid composition comprising about 35 wt.% metallic Co, and subsequently with Ca(OH)2. The results of Table 2 show that high recovery rates for Co may be achieved, even in absence of a reducing agent. It was further experienced that also Ni and Fe were recovered in high yields. In absence of a reducing agent (EX 1.1-1.3), Mn and W remained predominantly in the solid phase, and were thus not dissolved.

EXAMPLE 2

The same procedure as Example 1 was followed. About 4.9 ton of solid dry material having a composition as depicted in Table 1 is added to 20.000 L of a 3.4 M sulphuric acid leaching solution. Reaction temperature is maintained at 90°C. Process conditions and recovery yields for Co are reported in Table 3.

Table 3. Recovery yields for Co in processes according to Example 2.

Processing time (h) Recovery Co (%) ^a

EX 2.1 7 95

EX 2.2 12 96

EX 2.3 16 + 10 (metal powder) ^b 98 ^a percentage of Co recovered, relative to the Co content of said solid feed material. ^b processing time of 16 hours in 3.4 M sulphuric acid and subsequently 10 hours in presence of 830 kg metal powder having a composition of 54 wt.% Fe, 25 wt.% Co, 15 wt.% Ni and 3 wt.% Cu.

The leachate is further neutralised using about 10.2 ton of Co(OH)2 having a Cocontent of about 32%. Further neutralisation to pH 3 is achieved by addition of Ca(OH) ₂ .

The results of Table 4 show that high recovery rates for Co may be achieved, even in absence of a reducing agent. It was further experienced that also Ni and Fe were recovered in high yields, i.e. more than 96%.

EXAMPLE 3

The procedure according to Example 1 is repeated, whereby 50 g dry solid is subjected to a leaching procedure using 500 mL of a sulphuric acid leaching liquid. A solid feed material having a Co content of 32.6 wt.% is used. The fraction of Co ³⁺ , relative to the total amount of Co in said solid feed material, is about 0.46. Process conditions and recovery yields for Co are reported in Table 4.

EXAMPLE 4

The procedure according to Example 3 is repeated. A solid feed material having a Co content of 31.5 wt.% is used. Process conditions and recovery yields for Co are reported in Table 4.

EXAMPLE 5

The procedure according to Example 3 is repeated. A solid feed material having a Co content of 32.6 wt.% is used. Process conditions and recovery yields for Co are reported in Table 4.

EXAMPLE 6

The procedure according to Example 3 is repeated. A solid feed material having a Co content of 20.4 wt.% is used. Process conditions and recovery yields for Co are reported in Table 4.

Table 4. Recovery yields for Co in processes according to Examples 3 to 6.

Sulphuric acid con- Processing time Recovery Co centration (M) ^b (h) (%) ^a

EX 3.1 3.5 2 80

EX 3.2 3.5 4 86

EX 3.3 3.5 6 89

EX 4.1 3.5 2 74

EX 4.2 3.5 4 79

EX 4.3 3.5 6 81

EX 5.1 3.3 2 74

EX 5.2 3.3 4 75

EX 5.3 3.3 6 78 Sulphuric acid con- Processing time Recovery Co centration (M) ^b (h) (%) ^a

EX 6.1 3.2 2 99

EX 6.2 3.2 4 100

EX 6.3 3.2 6 100 ^a percentage of Co recovered, relative to the Co content of said solid feed material. ^b free sulphuric acid concentration.

EXAMPLE 7

The procedure according to Example 1 is repeated. A solid feed material having a Co content of about 35 wt.% was used. The leaching solution used had a sulphuric acid concentration of 2.4 M. A leaching temperature of about 90°C is maintained, and the leaching process is continued for about 10 hours. A Co recovery rate of about 83% was achieved.

EXAMPLE 8

The procedure according to Example 1 is repeated, whereby 50 g dry solid is subjected to a leaching procedure using 500 mL of a sulphuric acid leaching liquid. The fraction of Co ³⁺ , relative to the total amount of Co in said solid feed material, is 0.67. The solid material was contacted with the leaching solution for a period of 4 hour. Process conditions and recovery yields for Co are reported in Table 5. Results show a significant increase in Co recovery for leaching operations in presence of concentrated sulphuric acid according to the invention.

Table 5. Recovery yields for Co in processes according to Example 8.

Sulphuric acid con- Temperature Recovery Co centration (M) ^b (°C) (%) ^a

COMP. EX. 8.1 - 60 0.8

EX 8.2 2.0 90 8.1

EX 8.3 3.0 90 12

EX 8.4 3.8 90 12 ^a percentage of Co recovered, relative to the Co content of said solid feed material. ^b free sulphuric acid concentration. EXAMPLE 9

The procedure according to Example 3 is repeated, whereby 50 g dry solid is subjected to a leaching procedure using 500 mL of a 3.5 M sulphuric acid leaching liquid. The fraction of Co ³⁺ , relative to the total amount of Co in said solid feed material, is 0.16. The solid material was contacted with the leaching solution for a period of 8 hour. Results indicate an increase in Co recovery for leaching operations in presence of concentrated sulphuric acid according to the invention compared to leaching operations using a lower sulphuric acid concentration.

EXAMPLE 10

A solid active battery material comprising Co, Mn, Ni, Li and oxygen is provided according to the composition detailed in Table 6. The fraction of Co ³⁺ , relative to the total amount of Co in said solid feed material, is 1.0.

Table 6. Composition of solid feed material.*

Co Mn Ni Li

11 14 23 4/7

* expressed in wt.%, relative to total dry weight of said solid material. Oxygen makes up the balance to 100%.

200 g of solid material having a composition as depicted in Table 6 is added to 0.75 L water, sulphuric acid is added to reach a sulphuric acid concentration as illustrated in Table 7 that also illustrates the process conditions. Recovery yields for Co, Mn and Ni are reported in Table 7.

Table 7. Recovery yields for Co in processes according to Example 10.

Sulphuric acid Tempera- Recovery Recovery Recovery concentration ture (°C) Co (%) ^a Mn (%) ^a Ni (%) ^a

(M)

COMP. EX. 0.05 ^bl 85 28 21 40

10.1

EX 10.1 2.7 ^b2 85 84 <10 92 Sulphuric acid Tempera- Recovery Recovery Recovery concentration ture (°C) Co (%) ^a Mn (%) ^a Ni (%) ^a

(M)

EX 10.2 4.3 ^b2 85 93 <10 97 ^a percentage of Co, Mn and Ni recovered, relative to the content of Co, Mn and Ni, respectively, in said solid feed material. ^bl processing time 1 hour; ^b2 processing time 1.5 hour. The results of Table 7 show that high recovery rates for Co may be achieved, even in absence of a reducing agent. It was further experienced that also Ni is recovered with high yields and that the process allows a selective leaching of Co and Ni compared to Mn. COMPARATIVE EXAMPLE 1

The procedure according to Example 7 is repeated, whereby the leaching solution used had a sulphuric acid concentration of about 1 M. A Co recovery rate of about 50% was achieved.