Method for producing cobalt solution and method for producing cobalt salt

Abstract

To provide a method for producing a cobalt solution capable of efficiently removing magnesium ions from a cobalt-containing solution containing magnesium ions and a method for producing a cobalt salt.SOLUTION: A method for producing a cobalt solution includes a step in which from a cobalt-containing solution containing magnesium ions, obtained by subjecting battery powder from lithium-ion battery waste to at least a leaching treatment, magnesium ions are removed to produce a cobalt solution. In this process, a solvent containing a carboxylic acid-based extracting agent is used to extract cobalt ions from the cobalt-containing solution and separate magnesium ions. After this, cobalt ions are back-extracted from the solvent, resulting in the cobalt solution as the reverse-extraction liquid.SELECTED DRAWING: None

Description

[Technical field]

[0001] This specification discloses a method for making a cobalt solution, a method for making a cobalt salt, a method for making a nickel solution, and a method for making a nickel salt. [Background technology]

[0002] In recent years, from the perspective of effective resource utilization, recovery of valuable metals such as cobalt and nickel from lithium-ion battery waste, which is discarded due to product life, manufacturing defects, or other reasons, through wet processing, has been widely considered.

[0003] In relation to this, Patent Document 1 describes a method for separating and recovering metals from a mixed metal aqueous solution, comprising the steps of: step (1): performing solvent extraction on a mixed metal aqueous solution containing metal group A consisting of lithium, manganese, nickel, and cobalt, and metal group B consisting of copper, aluminum, and iron, using a first mixed extractant containing a phosphonate ester extractant and a carboxylic acid extractant, and separating metals belonging to metal group B from the mixed metal solution; step (2): performing solvent extraction on the extraction residue after step (1) using a second mixed extractant containing a phosphate ester extractant and an oxime extractant, and further separating metals belonging to metal group B from the extraction residue and separating manganese; step (3): performing solvent extraction on the extraction residue after step (2) using a phosphonate ester extractant, and separating cobalt from the extraction residue; and step (4): performing solvent extraction on the extraction residue after step (3) using a carboxylic acid extractant, and separating nickel from the extraction residue.

[0004] Patent Documents 2 and 3 also disclose a method for treating lithium-ion battery scrap containing Li, Ni, Co, Mn, Al, Cu, and Fe, which comprises a roasting step, a crushing step, and a sieving step in this order, and then a leaching step in which the lithium-ion battery scrap is added to an acidic solution to be leached, leaving at least a part of the Cu as a solid, an Fe·Al removal step in which the leaching liquid obtained in the leaching step is subjected to, in any order, an Fe removal process in which an oxidizing agent is added to separate and remove Fe, and an Al removal process in which an Al·Mn extraction step in which the remaining Al and Mn are extracted and removed from the separation liquid obtained in the Fe·Al removal step by solvent extraction, and an Al·Mn extraction step in which the remaining Al and Mn are extracted and removed ... A method for treating lithium-ion battery scraps has been proposed, which includes a Co recovery step of extracting and stripping Co from a first post-extraction solution obtained in an extraction step, and recovering Co by electrowinning, a Ni recovery step of extracting and stripping a part of Ni from a second post-extraction solution obtained by solvent extraction in the Co recovery step, and recovering the Ni by electrowinning, a Li concentration step of extracting and stripping the remaining Ni and Li from a third post-extraction solution obtained by solvent extraction in the Ni recovery step, and concentrating Li by repeating the extraction and stripping operations, and a Li recovery step of carbonate Li in the Li concentrated solution obtained in the Li concentration step and recovering it as lithium carbonate. Patent documents 2 and 3 describe that "in the solvent extraction in the Co recovery step, a phosphonate ester extractant is used for the first post-extraction solution" and that "in the solvent extraction in the Ni recovery step, a carboxylic acid extractant is used for the second post-extraction solution". [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-162982 A [Patent Document 2] International Publication No. 2018 / 181816 [Patent Document 3] US Patent Application Publication No. 2020 / 0044295 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the battery powder of the lithium ion battery waste is subjected to a leaching treatment, magnesium ions may be contained in the solution containing cobalt ions due to the lithium ion battery waste containing a relatively large amount of magnesium, etc. If the magnesium ions are not sufficiently removed, the purity of the cobalt solution or nickel solution to be produced decreases, and there is a risk that the purity will not be sufficient for effective use in the production of lithium ion batteries.

[0007] This specification provides a method for producing a cobalt solution capable of effectively removing magnesium ions from a cobalt-containing solution containing magnesium ions, and a method for producing a cobalt salt, and also provides a method for producing a nickel solution capable of effectively removing magnesium ions from a nickel-containing solution containing magnesium ions, and a method for producing a nickel salt. [Means for solving the problem]

[0008] The method for producing a cobalt solution disclosed in this specification is a method for producing a cobalt solution by removing magnesium ions from the cobalt-containing solution, which is obtained by at least subjecting battery powder that is lithium-ion battery waste to a leaching treatment, and includes a magnesium separation step of extracting cobalt ions from the cobalt-containing solution using a solvent containing a carboxylic acid extractant to separate the magnesium ions, and then stripping the cobalt ions from the solvent to obtain the cobalt solution as a stripped liquid.

[0009] Furthermore, the method for producing a cobalt salt disclosed in this specification is a method for producing a cobalt salt by using the above-mentioned method for producing a cobalt solution, and includes a crystallization step of crystallizing a cobalt salt from the cobalt solution obtained in the magnesium separation step.

[0010] The method for producing a nickel solution disclosed in this specification is a method for producing a nickel solution by removing magnesium ions from the nickel-containing solution, which is obtained by at least performing a leaching treatment on battery powder of lithium-ion battery waste and contains cobalt ions and magnesium ions at a concentration of 0.002 g / L to 1.000 g / L, and includes a cobalt extraction step of extracting some of the cobalt ions and magnesium ions from the nickel-containing solution using a solvent containing a phosphonate ester extractant, and a nickel extraction step of extracting nickel ions from a post-extraction solution obtained after extraction in the cobalt extraction step, which contains nickel ions and magnesium ions at a concentration of 0.001 g / L to 0.610 g / L, using a solvent containing a carboxylic acid extractant to set the equilibrium pH to 6.3 to 7.5 to separate the magnesium ions, and then stripping the nickel ions from the solvent to obtain the nickel solution as a stripped liquid.

[0011] Furthermore, the method for producing a nickel salt disclosed in this specification is a method for producing a nickel salt using the above-mentioned method for producing a nickel solution, and includes a crystallization step of crystallizing a nickel salt from the nickel solution obtained in the nickel extraction step. Effect of the Invention

[0012] According to the above-mentioned method for producing a cobalt solution and method for producing a cobalt salt, magnesium ions can be effectively removed from a cobalt-containing solution containing magnesium ions. According to the above-mentioned method for producing a nickel solution and method for producing a nickel salt, magnesium ions can be effectively removed from a nickel-containing solution containing magnesium ions. The obtained cobalt solution and nickel solution have few impurities and can be used for producing lithium-ion batteries. [Brief description of the drawings]

[0013] [Figure 1]FIG. 1 is a flow chart showing an example of a process for recovering metals from lithium ion battery waste to which the method for producing a cobalt solution according to one embodiment can be applied. [Diagram 2] FIG. 1 is a flow diagram showing a method for producing a cobalt salt according to one embodiment. [Diagram 3] 1 is a graph showing the relationship between the extraction rate of each ion and the equilibrium pH during cobalt extraction in an embodiment. [Figure 4] 1 is a graph showing the removal rate of each ion in a post-stripping solution versus equilibrium pH during scrubbing of a solvent containing cobalt ions in an example. [Diagram 5] 1 is a graph showing the relationship between the extraction rate of each ion and the equilibrium pH during nickel extraction in an example. [Figure 6] 1 is a graph showing the removal rate of each ion in a post-stripping solution versus equilibrium pH during scrubbing of a nickel ion-containing solvent in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the above-mentioned method for producing a cobalt solution, method for producing a cobalt salt, method for producing a nickel solution, and method for producing a nickel salt will be described in detail.

[0015] The cobalt solution means an acidic solution containing cobalt ions and anions, and examples thereof include a cobalt sulfate solution, a cobalt hydrochloride solution, and a cobalt nitrate solution. An appropriate anion is selected depending on the cobalt salt to be produced. The cobalt solution is preferably highly pure with impurities removed to an extent that it can be effectively used in the production of lithium ion batteries, and the magnesium ion concentration, nickel ion concentration, manganese ion concentration, aluminum ion concentration, iron ion concentration, and copper ion concentration are preferably all 0.01 g / L or less. Furthermore, the sodium ion concentration is preferably 0.1 g / L or less. Furthermore, the cobalt salt means a cobalt compound (solid) in which cobalt ions and anions are ionically bonded, and is obtained by crystallization from the cobalt solution, and examples thereof include cobalt sulfate, cobalt hydrochloride, and cobalt nitrate. The magnesium grade, nickel grade, manganese grade, aluminum grade, iron grade, and copper grade of the cobalt salt are all 10 mass ppm or less. Furthermore, the sodium grade is preferably 10 mass ppm or less.

[0016] The nickel solution means an acidic solution containing nickel ions and anions, and examples of the solution include nickel sulfate solution, nickel hydrochloride solution, and nickel nitrate solution. An appropriate anion is selected depending on the nickel salt to be produced. The nickel solution is preferably high in purity with impurities removed to an extent that it can be effectively used in the production of lithium ion batteries, and the magnesium ion concentration, cobalt ion concentration, manganese ion concentration, aluminum ion concentration, iron ion concentration, and copper ion concentration are preferably all 0.01 g / L or less. Furthermore, the sodium ion concentration is preferably 0.1 g / L or less. The nickel salt means a nickel compound (solid) in which nickel ions and anions are ionically bonded, and is obtained by crystallization from the nickel solution, and examples of the nickel salt include nickel sulfate, nickel hydrochloride, and nickel nitrate. The magnesium grade, cobalt grade, manganese grade, aluminum grade, iron grade, and copper grade of the nickel salt are all 10 mass ppm or less. Furthermore, the sodium grade is preferably 10 mass ppm or less.

[0017] In one embodiment of the method for producing a cobalt solution, a cobalt solution is produced from a cobalt-containing solution obtained by performing at least a leaching process (=leaching step) on battery powder of lithium-ion battery waste. This cobalt-containing solution contains cobalt ions and magnesium ions as impurities. In order to separate the magnesium ions from the cobalt-containing solution, a magnesium separation step is performed in which the cobalt ions are extracted from the cobalt-containing solution using a solvent containing a carboxylic acid extractant, and the extracted cobalt ions are back-extracted from the solvent.

[0018] In the magnesium separation step, by using a solvent containing a carboxylic acid extractant, it becomes possible to extract cobalt ions without substantially extracting magnesium ions. This makes it possible to effectively remove magnesium ions from the cobalt-containing solution. In the magnesium separation step, by back-extracting cobalt ions from the solvent that extracted the cobalt ions, a cobalt solution from which magnesium ions have been sufficiently removed can be obtained.

[0019] In addition, a method for producing a nickel solution according to one embodiment produces a nickel solution from a nickel-containing solution obtained by performing at least a leaching process (=leaching step) on battery powder of lithium-ion battery waste. This nickel-containing solution contains cobalt ions and nickel ions, and also contains magnesium ions at a concentration of 0.002 g / L to 1.000 g / L. A cobalt extraction step is performed on the nickel-containing solution to extract a part of the cobalt ions and magnesium ions. The post-extraction liquid obtained after extraction in the cobalt extraction step contains nickel ions, and also contains magnesium ions at a concentration of 0.001 g / L to 0.610 g / L. A predetermined nickel extraction step is performed on this post-extraction liquid.

[0020] In the nickel extraction step, a solvent containing a carboxylic acid extractant is used for the post-extraction liquid to adjust the equilibrium pH during extraction to 6.3 to 7.5. This allows nickel ions to be extracted into the solvent while magnesium ions are not extracted, making it possible to effectively separate nickel and magnesium. In the nickel extraction step, nickel ions are back-extracted from the solvent that extracted the nickel ions, thereby obtaining a nickel solution from which magnesium ions have been sufficiently removed.

[0021] In this embodiment, various solutions can be applied as the cobalt-containing solution or nickel-containing solution, as long as they are obtained by subjecting battery powder of lithium-ion battery waste to at least a leaching treatment (= leaching process), and are solutions containing cobalt ions and magnesium ions, or solutions containing cobalt ions, nickel ions and magnesium ions. In addition, after the leaching process, a neutralization process, a solvent extraction process, etc. may be inserted as necessary. Here, a detailed description will be given of an example in which the present invention is applied to a process for recovering metals from lithium-ion battery waste as shown in FIG. 1, but the present invention is not limited to such a specific process.

[0022] (Lithium ion battery waste) The lithium-ion battery waste targeted here is lithium-ion batteries that can be used in mobile phones and various other electronic devices, and which have been discarded due to the end of the battery product's life, manufacturing defects, or other reasons. From the viewpoint of effective resource utilization, there is a demand for recovering valuable metals from lithium-ion battery waste. In particular, it is desirable to recover the valuable metals cobalt and nickel in high purity so that they can be reused in the manufacture of lithium-ion batteries.

[0023] Lithium ion battery waste has a housing containing aluminum as an exterior that envelops the periphery. For example, this housing may be made of only aluminum, or may contain aluminum and iron, aluminum laminate, etc. In addition, lithium ion battery waste may contain a positive electrode active material made of a single metal oxide selected from the group consisting of lithium, nickel, cobalt, and manganese, or two or more composite metal oxides, etc., in the housing, or an aluminum foil (positive electrode current collector) to which the positive electrode active material is applied and fixed, for example, by polyvinylidene fluoride (PVDF) or other organic binders, etc. In addition, lithium ion battery waste may contain copper, iron, etc. Furthermore, lithium ion battery waste usually contains an electrolyte in the housing. For example, ethylene carbonate, diethyl carbonate, etc. may be used as the electrolyte.

[0024] Lithium ion battery waste may contain magnesium, for example, at a ratio of 0.02% by mass to 0.10% by mass relative to cobalt or nickel. Magnesium may be used, for example, as an alloy component element of aluminum foil used as a current collector of a positive electrode. Such magnesium dissolves in the acid leaching solution in the leaching step described below and is contained as ions in the post-leaching solution. Although magnesium is removed to some extent in the neutralization step and manganese / aluminum extraction step, it is not removed to an extent that can be effectively used in the manufacture of lithium ion batteries and is contained in the acid solution. The magnesium ions are further extracted and back-extracted together with the cobalt ions in the subsequent cobalt extraction step, and a cobalt-containing solution containing magnesium ions is obtained. In this embodiment, a magnesium separation step is performed to remove magnesium ions from the obtained cobalt-containing solution containing magnesium ions.

[0025] (Pretreatment process) The pretreatment step includes roasting. In roasting, the lithium ion battery waste is heated. More specifically, the lithium ion battery waste can be heated, for example, at a temperature range of 450°C to 1000°C, preferably 600°C to 800°C, for 0.5 to 4 hours. This roasting is performed, for example, for the purpose of changing metals such as lithium and cobalt contained in the lithium ion battery waste into a form that is easily melted. Roasting can be performed in an air atmosphere or an inert atmosphere such as nitrogen, and may be performed in both an air atmosphere and an inert atmosphere sequentially or in any order. The roasting furnace may be of a batch type or a continuous type, and for example, a stationary furnace for a batch type and a rotary kiln furnace for a continuous type are available, and various other furnaces can also be used.

[0026] After roasting, the lithium ion battery waste can be crushed to extract battery powder containing the positive electrode active material from the casing of the lithium ion battery waste. In crushing, the casing of the lithium ion battery waste is broken and the positive electrode active material is selectively separated from the current collector (aluminum foil) to which the positive electrode active material is applied. For this, various known devices or equipment can be used, but it is particularly preferable to use an impact type crusher that can crush the lithium ion battery waste by applying an impact while cutting it. Examples of the impact type crusher include a sample mill, a hammer mill, a pin mill, a wing mill, a tornado mill, and a hammer crusher. A screen can be installed at the outlet of the crusher, and the lithium ion battery waste is crushed to a size that can pass through the screen and then discharged from the crusher through the screen.

[0027] After crushing, the battery powder can be sieved using a sieve with appropriate openings in order to remove, for example, current collectors (aluminum foil or copper foil), broken pieces of the housing, etc. As a result, aluminum and copper remain on the sieve, and battery powder from which aluminum and copper have been removed to a certain extent is obtained below the sieve. This battery powder can be subjected to the leaching process described below.

[0028] In addition, the roasting, crushing, and sieving in the pretreatment process may be performed individually as necessary, or may be performed in any order.

[0029] (Leaching process) In the leaching step, the battery powder is added to an acidic leaching solution such as sulfuric acid and leached. The leaching step can be carried out by a known method or under known conditions, but the pH is preferably 0.0 to 2.0.

[0030] If necessary, the battery powder may be brought into contact with water before the leaching with the acid leaching solution to separate only the lithium contained in the battery powder. In this case, the residue after the contact of the battery powder with water is added to the acid leaching solution to perform the leaching.

[0031] The leaching step produces a leaching solution after solid-liquid separation in which predetermined metals are dissolved. The predetermined metals include cobalt and magnesium. The predetermined metals may further include nickel, manganese, aluminum, iron, etc. For example, the cobalt ion concentration in the post-leaching solution may be 0 g / L to 50 g / L, the nickel ion concentration may be 0 g / L to 50 g / L, the manganese ion concentration may be 1 g / L to 50 g / L, the magnesium ion concentration may be 0.001 g / L to 0.1 g / L, the aluminum ion concentration may be 0.01 g / L to 10 g / L, and the iron ion concentration may be 0.1 g / L to 5 g / L. However, when the positive electrode active material of the lithium ion battery waste to be treated is a ternary system, the cobalt ion concentration in the post-leaching solution may be 1 g / L to 50 g / L, the nickel ion concentration may be 1 g / L to 50 g / L, the manganese ion concentration may be 1 g / L to 50 g / L, the magnesium ion concentration may be 0.001 g / L to 0.1 g / L, the aluminum ion concentration may be 0.01 g / L to 10 g / L, and the iron ion concentration may be 0.1 g / L to 5 g / L.

[0032] (neutralization process) The post-leaching solution is subjected to a neutralization process. In the neutralization process, an alkali such as sodium hydroxide is first added to the post-leaching solution to neutralize it to a predetermined pH. This causes some of the aluminum dissolved in the post-leaching solution to precipitate. Then, the residue containing some of the aluminum can be removed by solid-liquid separation using a filter press, thickener, etc.

[0033] Here, it is more preferable to adjust the pH to 4.0 to 6.0 by adding an alkali. Also, here, the oxidation-reduction potential (=ORP value, silver / silver chloride potential standard) of the post-leaching solution is preferably -500mV to 100mV. The solution temperature is preferably 50℃ to 90℃.

[0034] Thereafter, an oxidizing agent is added and the pH is adjusted to within the range of 3.0 to 4.0, thereby precipitating the iron in the solution. The addition of the oxidizing agent oxidizes the iron in the solution from divalent to trivalent, and the trivalent iron precipitates as an oxide or hydroxide at a lower pH than the divalent iron. In many cases, the iron precipitates as a solid such as iron hydroxide (Fe(OH)3). The precipitated iron can be removed by solid-liquid separation.

[0035] In order to precipitate iron, the ORP value during oxidation is preferably 300 mV to 900 mV. Prior to the addition of the oxidizing agent, an acid such as sulfuric acid, hydrochloric acid, or nitric acid can be added to lower the pH.

[0036] The oxidizing agent is not particularly limited as long as it can oxidize iron, but is preferably manganese dioxide, a positive electrode active material, and / or a manganese-containing leaching residue obtained by leaching a positive electrode active material. The manganese-containing leaching residue obtained by leaching a positive electrode active material with an acid or the like may contain manganese dioxide. When the above-mentioned manganese (positive electrode active material, etc.) is used as the oxidizing agent, a precipitation reaction occurs in which manganese dissolved in the liquid becomes manganese dioxide, and the precipitated manganese can be removed together with iron.

[0037] After the addition of the oxidizing agent, an alkali such as sodium hydroxide, sodium carbonate, or ammonia can be added to adjust the pH to a predetermined range.

[0038] If the neutralization step is carried out under conditions that remove a large amount of magnesium ions, there is a concern that iron and aluminum may not be effectively removed and that losses of cobalt, nickel, etc. may become significant. Therefore, it is preferable to carry out the neutralization step under the conditions described above. In this case, when the magnesium content in the battery powder is taken as 100 mass%, 10 mass% to 30 mass% of magnesium may be removed in the neutralization step, but magnesium may remain in the neutralized solution obtained after the neutralization step.

[0039] (Manganese / Aluminum Extraction Process) The neutralized liquid obtained after the neutralization step is subjected to a manganese / aluminum extraction step in which the remaining manganese and / or aluminum is extracted and removed by a solvent extraction method, thereby obtaining a metal-containing solution as an extracted liquid (=aqueous phase) from which manganese and / or aluminum has been removed.

[0040] At this time, it is preferable to use an extractant containing a phosphoric acid ester extractant for the neutralized liquid. Here, examples of the phosphoric acid ester extractant include di-2-ethylhexyl phosphoric acid (trade name: D2EHPA or DP8R). The extractant may be a mixture of an oxime extractant and a phosphoric acid ester extractant. In this case, the oxime extractant is preferably an aldoxime or an aldoxime-based extractant. Specifically, examples include 2-hydroxy-5-nonylacetophenone oxime (trade name: LIX84), 5-dodecyl salicylaldoxime (trade name: LIX860), a mixture of LIX84 and LIX860 (trade name: LIX984), and 5-nonyl salicylaldoxime (trade name: ACORGAM5640), and among these, 5-nonyl salicylaldoxime is preferable from the viewpoint of price and the like.

[0041] In the solvent extraction for extracting manganese and / or aluminum, the equilibrium pH during extraction is preferably 2.5 to 4.0, more preferably 2.8 to 3.3. Extraction is desirably performed in multiple stages. This allows a larger amount of magnesium to be removed from the neutralized solution in addition to manganese and / or aluminum. When performing extraction in multiple stages, it is also effective to set the equilibrium pH during extraction in at least one of the multiple stages, for example the equilibrium pH during extraction in the first stage, within the above-mentioned range, and to lower the equilibrium pH during extraction with each stage.

[0042] In the manganese / aluminum extraction step, it is preferable to carry out the steps under the above-mentioned conditions in order to effectively extract manganese and aluminum while suppressing losses of cobalt, nickel, etc. In this case, the metal-containing solution, which is the post-extraction liquid, contains a certain amount of magnesium ions. When the magnesium content in the battery powder is taken as 100 mass%, 10 mass% to 60 mass% of magnesium may be removed in the manganese / aluminum extraction step, but magnesium ions may remain in the metal-containing solution obtained in the manganese / aluminum extraction step.

[0043] The metal-containing solution (e.g., nickel-containing solution, etc.) obtained in the manganese / aluminum extraction step contains at least one or both of cobalt ions and nickel ions, and magnesium ions as impurities. The magnesium ion concentration of the metal-containing solution may be, for example, 0.002 g / L or more, typically 0.05 g / L or more. As described above, in the neutralization step and the manganese / aluminum extraction step, although a certain amount of magnesium may be removed, the magnesium ions may not be removed to an extent that can be effectively used in the manufacture of lithium-ion batteries, and the magnesium ions may be contained in the metal-containing solution. When the metal-containing solution contains a certain amount of magnesium ions in this way, for example, in a metal-containing solution containing cobalt ions and nickel ions, many of the magnesium ions tend to remain after the cobalt extraction step, so it is particularly effective to perform a magnesium separation step as in this embodiment. In addition, many of the magnesium ions tend to remain in the post-extraction liquid after the cobalt extraction step, so it is effective to separate nickel and magnesium in the nickel extraction step as well. However, this may not be a significant problem if the magnesium ion concentration of the metal-containing solution is low, for example, less than 0.002 g / L, whereas the magnesium ion concentration of the metal-containing solution may be 1.000 g / L or less.

[0044] The metal-containing solution has a cobalt ion concentration of, for example, 0 g / L to 50 g / L, typically 1 g / L to 15 g / L, and a nickel ion concentration of, for example, 0 g / L to 50 g / L, typically 1 g / L to 15 g / L. The metal-containing solution may contain sodium ions as an impurity. In this case, the sodium concentration in the metal-containing solution is, for example, 5 g / L to 40 g / L, typically 10 g / L to 30 g / L.

[0045] (Cobalt extraction process) The metal-containing solution after the manganese / aluminum extraction step contains either one or both of cobalt ions and nickel ions, and magnesium ions. In the cobalt extraction step, the metal-containing solution containing cobalt ions and nickel ions is subjected to a solvent extraction method to separate mainly cobalt ions from nickel ions in the metal-containing solution, and then the cobalt ions extracted into the solvent are back-extracted. As a result, a cobalt-containing solution that is substantially free of nickel is obtained as a back-extracted solution. Note that magnesium ions may remain in the extracted solution from the cobalt extraction step. Note that the metal-containing solution containing cobalt ions and magnesium ions but not nickel ions can be subjected to the magnesium separation step without the cobalt extraction step. Also, the metal-containing solution containing nickel ions and magnesium ions but not cobalt ions may be subjected to the nickel extraction step without passing through the cobalt extraction step.

[0046] In the cobalt extraction step, if the conditions are set so that as many cobalt ions as possible are extracted and as few nickel ions as possible are extracted, not only cobalt ions but also some magnesium ions are extracted. When the magnesium content in the battery powder is taken as 100 mass%, the cobalt-containing solution may contain 5 mass% to 30 mass% magnesium. Note that if the post-leaching solution obtained in the above-mentioned leaching step does not contain cobalt ions or nickel ions, and therefore the metal-containing solution after the manganese / aluminum extraction step does not contain cobalt ions or nickel ions, there is no need to separate the cobalt ions and nickel ions, so the cobalt extraction step can be omitted.

[0047] In the cobalt extraction step, cobalt ions and magnesium ions are extracted using a solvent containing a phosphonate ester extractant. As the phosphonate ester extractant, 2-ethylhexyl phosphonate (trade name: PC-88A, Ionquest801) is preferred from the viewpoint of separation efficiency between nickel ions and cobalt ions.

[0048] In the cobalt extraction step, the equilibrium pH during extraction is preferably 4.5 to 5.5, more preferably 4.8 to 5.2. When multiple extraction stages are performed, the equilibrium pH during at least one extraction stage, for example the equilibrium pH during the first extraction stage, can be set to a value within this range. The number of extraction stages and the O / A ratio can be appropriately set.

[0049] As an example of the extraction in the cobalt extraction step, the metal-containing solution can be extracted using a solvent containing PC-88A. The solvent may contain 25% by volume of PC-88A and 75% by volume of Shellsol D70 ("Shellsol" is a registered trademark of Shell Chemical Co., Ltd.). When performing extraction in multiple stages, the number of stages can be set appropriately. For example, the equilibrium pH during extraction may be lowered with each stage. The O / A ratio can be set appropriately, and NaOH can be used as a pH adjuster. When the magnesium ion concentration of the metal-containing solution is 0.002 g / L, the magnesium ion concentration of the back-extracted solution obtained in the cobalt extraction step may be 0.002 g / L, and the magnesium ion concentration of the extracted solution may be 0.001 g / L. When the magnesium ion concentration of the metal-containing solution is 1.000 g / L, the magnesium ion concentration of the back-extracted solution obtained in the cobalt extraction step may be 0.550 g / L, and the magnesium ion concentration of the extracted solution may be 0.610 g / L.

[0050] The solvent containing the extracted cobalt ions and magnesium ions may be scrubbed one or more times as necessary. The scrubbing liquid may be, for example, a sulfuric acid acidic solution, and the equilibrium pH may be 3.5 to 5.5.

[0051] Cobalt ions are stripped from the solvent in which cobalt ions and magnesium ions have been extracted. At that time, magnesium ions are also extracted together. A cobalt-containing solution containing cobalt ions and magnesium ions as impurities is obtained as a liquid after stripping. The stripping liquid used for stripping may be any inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. Here, the stripping is performed under pH conditions such that as much of the cobalt ions as possible move from the organic phase (=solvent) to the aqueous phase (=stripping liquid). Specifically, the pH is preferably in the range of 2.0 to 4.0, and more preferably in the range of 2.5 to 3.5. The O / A ratio and the number of stages can be appropriately determined. The liquid temperature may be room temperature, but is preferably 0°C to 40°C.

[0052] (Magnesium separation process) The stripped liquid obtained by stripping in the cobalt extraction step contains cobalt ions and magnesium ions as impurities. Magnesium ions become impurities and reduce the purity, particularly when a crystallization step described below is performed to produce a cobalt salt. In an embodiment of the method for producing a cobalt solution, the stripped liquid is used as a cobalt-containing solution, and a solvent extraction method is used to extract cobalt ions into an organic phase and leave magnesium ions in the aqueous phase, thereby separating magnesium. Thereafter, the organic phase is stripped to obtain a cobalt solution as a stripped liquid.

[0053] The magnesium separation step can be applied to any solution containing cobalt ions and magnesium ions as impurities. For example, when a leaching solution is obtained by leaching metals in a battery powder containing cobalt but not nickel, the extracted solution after the manganese / aluminum extraction step does not contain nickel ions, so the magnesium separation step can be carried out without going through the cobalt extraction step. The magnesium ion concentration of the cobalt-containing solution before the magnesium separation step is preferably 0.002 g / L to 1.000 g / L, typically 0.002 g / L to 0.550 g / L. If the magnesium ion concentration of the cobalt-containing solution is less than 0.002 g / L, even if magnesium ions are contained in the cobalt-containing solution obtained by performing extraction and back extraction in the cobalt extraction step, a high-purity cobalt solution suitable for, for example, lithium-ion batteries can be obtained without removing them in the magnesium separation step. On the other hand, when the magnesium ion concentration is high, for example, exceeds 1.000 g / L, attempting to remove the magnesium ions to a level that can be effectively used in the production of lithium-ion batteries in the magnesium separation step results in a large loss of cobalt ions, whereas preventing a large loss of cobalt ions in the magnesium separation step may result in failure to remove the magnesium ions to a level that can be effectively used in the production of lithium-ion batteries.

[0054] In the magnesium separation step, a solvent containing a carboxylic acid extractant such as neodecanoic acid, naphthenic acid, etc. is used. In particular, in order to extract cobalt ions while extracting as little magnesium ions as possible, a carboxylic acid extractant of neodecanoic acid, specifically Versatic Acid 10 (also called VA-10) manufactured by Shell Chemical Co., Ltd. is preferred.

[0055] The above carboxylic acid extractant is typically diluted with a hydrocarbon organic solvent and used as a solvent. Examples of the organic solvent include aromatic, paraffinic, and naphthenic solvents. Here, the concentration of the carboxylic acid extractant in the solvent is preferably 20% to 30% by volume. If the concentration of the carboxylic acid extractant is lower than 20% by volume, a large amount of organic phase may be required to increase the extraction efficiency. On the other hand, if the concentration of the carboxylic acid extractant is higher than 30% by volume, the viscosity of the organic phase increases, the phase separation property deteriorates, and there is a concern that separation of the aqueous phase and the organic phase becomes difficult. In the solvent extraction in the process other than the magnesium separation process, the extractant can be diluted in almost the same manner and used as the solvent.

[0056] The concentration of the carboxylic acid extractant in the solvent used for the extraction in the magnesium separation step is preferably 25% by volume or more. If the concentration of the carboxylic acid extractant in the solvent is lower than 25% by volume, a precipitate containing a cobalt compound or the like may occur on the aqueous phase side during the extraction of cobalt ions, which may lead to clogging of the piping and the shutdown of the operation. As described later, when performing extraction in multiple stages, it is preferable to maintain the concentration of the carboxylic acid extractant in the solvent at 25% by volume or more during extraction in each stage. The preferred range of the concentration of the carboxylic acid extractant in the solvent is 25% by volume to 30% by volume.

[0057] In addition, the equilibrium pH when extracting cobalt ions is preferably 6.0 to 7.0 so that the extraction rate of magnesium ions is less than 20% and the extraction rate of cobalt ions is close to 60%. If the equilibrium pH during extraction is high, many cobalt ions are extracted, but magnesium ions are also easily extracted. By lowering the equilibrium pH during extraction to a certain extent, magnesium ions are almost not extracted. In addition, when it is desired to maintain a high level of extraction rate of cobalt ions, it is more preferable to set the equilibrium pH to 6.5 to 7.0 so that the extraction rate of magnesium ions is less than 20% and the extraction rate of cobalt ions is even higher, 80% or more. In addition, when it is desired to suppress the extraction rate of magnesium ions, it is more preferable to set the equilibrium pH to 6.0 to 6.5 so that magnesium ions are almost not extracted. Extraction can be performed in only one stage, or in multiple stages (for example, three stages). When performing multiple stages of extraction, the equilibrium pH during at least one stage of extraction, preferably the first stage of extraction, can be in the above range. The equilibrium pH during extraction in the other stages is not particularly important, but the condition is often set so that the equilibrium pH gradually decreases with the number of stages. In particular, if the equilibrium pH during extraction in at least the final stage is set to 6.5 or less, magnesium is removed more effectively. However, even if the equilibrium pH during extraction is set relatively high, for example to 7.5, it is possible to remove magnesium ions to an acceptable level by performing scrubbing, which will be described below. The O / A ratio can be set appropriately.

[0058] If the pH during extraction of cobalt ions is relatively high, the solubility of the carboxylic acid extractant in water increases, and the carboxylic acid extractant in the solvent dissolves in the aqueous phase, resulting in a loss of the carboxylic acid extractant. In this case, the concentration of the carboxylic acid extractant in the solvent decreases, and as mentioned above, there is a risk of precipitation. To deal with this, it is desirable to recover the carboxylic acid extractant from the post-extraction solution, as described below.

[0059] To control the concentration of the carboxylic acid extractant in the solvent, for example, the relationship (calibration curve) between the concentration of the carboxylic acid extractant in the solvent and the amount of cobalt ions extracted into the solvent is obtained in advance. Then, a sample of the solvent is taken from the magnesium separation process, and a test is performed to extract cobalt ions from a solution containing cobalt ions using this sample. The concentration of the carboxylic acid extractant contained in the solvent can be estimated from the amount of cobalt ions extracted into the solvent in this test.

[0060] The extraction can be carried out based on a general method. For example, the solution (=aqueous phase) and the solvent (=organic phase) are brought into contact with each other, and typically stirred and mixed for 5 to 60 minutes using a mixer to react the ions with the extractant. The temperature during extraction is from room temperature (about 15°C to 25°C) to 60°C or less, and is preferably carried out at 35°C to 45°C for reasons of extraction speed, phase separation, and evaporation of the organic solvent. Thereafter, the mixed organic phase and aqueous phase are separated by a settler due to the difference in specific gravity.

[0061] If necessary, the solvent from which the cobalt ions have been extracted may be scrubbed. Scrubbing effectively removes magnesium ions that may be mixed into the solvent. Scrubbing can also remove sodium ions that may be present in the solvent, for example, due to a pH adjuster used in the solvent extraction. Scrubbing may be omitted.

[0062] In order to promote the removal of magnesium ions, etc., it is preferable that the equilibrium pH during scrubbing is 5.5 to 6.5. If the equilibrium pH during scrubbing exceeds 6.5, there is a concern that magnesium ions, etc. may not be sufficiently removed. Furthermore, if it is desired to further suppress cobalt loss, it is preferable that the equilibrium pH during scrubbing is 6.0 to 6.5. When the equilibrium pH during scrubbing is 5.5, about 50% of the cobalt ions are lost before and after scrubbing, but if the equilibrium pH is 6.0 or more, it is possible to suppress the loss of cobalt ions to a level where they are almost not observed. However, even if the loss of cobalt ions is large, it is possible to mix the scrubbing liquid with the leaching liquid and circulate it without discarding it. Furthermore, if it is desired to remove sodium ions in addition to magnesium ions, it is preferable that the equilibrium pH during scrubbing is 5.5 to 6.0. If the equilibrium pH during scrubbing is 6.0 or less, it is possible to remove almost all of the sodium ions.

[0063] The scrubbing liquid used in scrubbing may contain cobalt ions. In order to effectively remove impurities such as magnesium ions and sodium ions that may be contained in the solvent by scrubbing, it is preferable that the cobalt ion concentration of the scrubbing liquid is equal to or greater than the total concentration of impurities in the solvent. The impurities in the solvent refer to ions such as magnesium ions and sodium ions other than cobalt ions. Scrubbing may be performed in one or more stages, and the equilibrium pH in at least one stage may be in this range. The scrubbing liquid may be a sulfuric acid solution or the like.

[0064] Thereafter, the solvent from which the cobalt ions have been extracted is subjected to stripping using a stripping solution containing sulfuric acid, hydrochloric acid, nitric acid, or the like. When cobalt sulfate is to be produced in the crystallization step described below, it is preferable to use a stripping solution containing sulfuric acid. The pH during stripping is preferably 1.0 to 4.0, more preferably 1.5 to 2.0. There are no particular restrictions on the O / A ratio and the number of stages. The temperature during stripping is from room temperature (approximately 15°C to 25°C) to 60°C or less, and it is preferable to carry out stripping at 35°C to 45°C for reasons of extraction speed, phase separation, and evaporation of the organic solvent. As a result, a cobalt solution is obtained as a stripped liquid.

[0065] By passing through the magnesium separation step, the magnesium ion concentration of the cobalt solution can be sufficiently reduced to, for example, 0.001 g / L to 0.002 g / L. That is, the magnesium ions can be removed to a level that can be effectively used in the manufacture of lithium ion batteries. In addition, by carrying out the neutralization step, manganese / aluminum extraction step, and cobalt extraction step as pre-steps, the nickel ion concentration, manganese ion concentration, aluminum ion concentration, and iron ion concentration in the cobalt solution can also be reduced to a level that can be effectively used in the manufacture of lithium ion batteries.

[0066] The post-extraction liquid obtained after extracting cobalt ions into the solvent may contain the carboxylic acid extractant dissolved from the solvent during extraction. Discarding the post-extraction liquid results in a loss of the carboxylic acid extractant contained therein, so it is preferable to recover the carboxylic acid extractant from the post-extraction liquid.

[0067] To recover the carboxylic acid extractant from the post-extraction liquid, for example, the post-extraction liquid is mixed with a solvent to bring it into contact, and the equilibrium pH is adjusted to 5.5 or less to transfer the carboxylic acid extractant in the post-extraction liquid to the solvent, and then the solvent can be separated from the aqueous phase by gravity separation or the like. This allows the carboxylic acid extractant to be recovered from the post-extraction liquid in the solvent. The lower the equilibrium pH, the greater the amount of carboxylic acid extractant recovered, but if it is too low, the amount of recovery does not change much, and the cost increases due to the increase in the amount of acid such as sulfuric acid added. In addition, cobalt ions may remain in the carboxylic acid extractant at the time of recovery, and if the equilibrium pH is too low, the cobalt ions will transfer to the aqueous phase and become a loss. From this perspective, it is even more preferable that the equilibrium pH is 1.0 or more and 5.0 or less. The solvent to be contacted with the post-extraction liquid is not particularly limited, but can be a solvent after back extraction (and in some cases after further scavenging). This allows the solvent from which the carboxylic acid extractant has been recovered from the post-extraction liquid to be used for extracting cobalt ions in the magnesium separation process.

[0068] Alternatively, the post-extraction liquid alone can be adjusted to an equilibrium pH of 5.5 or less without contacting the post-extraction liquid with a solvent as described above. Then, for example, by performing gravity separation or the like, the carboxylic acid extractant is separated from the post-extraction liquid. In this way, it is also possible to recover the carboxylic acid extractant from the post-extraction liquid. In this case, it is even more preferable that the above-mentioned equilibrium pH is 1.0 or more and 5.0 or less. The carboxylic acid extractant separated from the post-extraction liquid can be used for the extraction of cobalt ions in the magnesium separation step. In many cases, in the magnesium separation step, the solvent after stripping (and sometimes after further scavenging) is used again for the extraction of cobalt ions and circulated. The carboxylic acid extractant separated from the post-extraction liquid can be used in the extraction of cobalt ions together with such a circulating solvent. In order to adjust the amount of circulating solvent sent to the extraction of cobalt ions according to the amount of carboxylic acid extractant recovered from the post-extraction liquid, a tank for storing the circulating solvent may be provided, as necessary, in the middle of the path that sends the circulating solvent from stripping (or subsequent scavenging) to extraction.

[0069] (Nickel extraction process) When cobalt ions and magnesium ions are separated from the metal-containing solution in the cobalt extraction step, the nickel extraction step can be performed on the post-extraction liquid obtained by the extraction in the cobalt extraction step. The post-extraction liquid after the cobalt extraction step may contain a small amount of magnesium ions in addition to nickel ions. The magnesium ion concentration of the post-extraction liquid may be 0.001 g / L to 0.610 g / L. When the magnesium content in the battery powder is 100 mass%, the post-extraction liquid may contain 5 mass% to 40 mass% magnesium. In this embodiment, the nickel extraction step is not limited to being applied to the post-extraction liquid obtained by the extraction in the cobalt extraction step, and can be applied to any solution containing nickel ions and magnesium ions as impurities. For example, when a post-extraction liquid is obtained by leaching a battery powder containing nickel but not cobalt, the nickel extraction step can be applied directly to the post-extraction liquid after the manganese / aluminum extraction step.

[0070] In the nickel extraction process, a carboxylic acid extractant is used to extract nickel ions from the above-mentioned post-extraction liquid, and the extracted nickel ions are stripped from the solvent. A nickel solution is obtained as the post-extraction liquid. Examples of carboxylic acid extractants include neodecanoic acid and naphthenic acid, and among them, neodecanoic acid (particularly VA-10) is preferred because of its excellent nickel ion extraction ability.

[0071] When extracting nickel ions, the equilibrium pH is preferably 6.3 to 7.5 so that the extraction rate of magnesium ions is close to 20% and the extraction rate of nickel ions exceeds 50%. The equilibrium pH is more preferably 6.4 to 6.9 so that the extraction rate of magnesium ions is low to close to 5% and the extraction rate of nickel ions is 80% or more. Furthermore, the equilibrium pH is more preferably 6.4 to 6.6 so that the extraction rate of cobalt ions is increased to a certain degree and magnesium ions are hardly extracted. When performing extraction in multiple stages (three stages, etc.), the equilibrium pH during at least one extraction stage, for example, the equilibrium pH during the first extraction stage, can be set within the above range. In extraction in multiple stages, the equilibrium pH can be gradually lowered as the stage progresses.

[0072] The solvent from which nickel ions have been extracted may be scrubbed using a scrubbing solution such as a sulfuric acid solution, if necessary. The equilibrium pH during scrubbing is preferably 5.5 to 6.5. If the equilibrium pH during scrubbing exceeds 6.5, the removal of magnesium ions that may be extracted into the solvent together with nickel ions may be insufficient. Furthermore, the equilibrium pH during scrubbing is preferably 5.5 to 6.0. If the equilibrium pH during scrubbing is 6.0 or less, most of the sodium ions can be removed in addition to the magnesium ions.

[0073] Thereafter, the solvent from which the nickel ions have been extracted is subjected to back extraction using a back extraction solution containing sulfuric acid, hydrochloric acid, nitric acid, or the like. The pH is preferably 1.0 to 3.0, and more preferably 1.5 to 2.5. The O / A ratio and the number of stages can be appropriately determined, but the O / A ratio is preferably 5 to 1, and more preferably 4 to 2. This results in a nickel solution being obtained as a post-back extraction liquid.

[0074] By passing through the nickel extraction process, the magnesium ion concentration of the nickel solution can be sufficiently reduced to, for example, 0.001 g / L to 0.002 g / L. That is, the magnesium ions can be removed to a level that can be effectively used in the manufacture of lithium ion batteries. In addition, by carrying out the neutralization process, the manganese / aluminum extraction process, and the cobalt extraction process as pre-processes, the cobalt ion concentration, manganese ion concentration, aluminum ion concentration, and iron ion concentration in the nickel solution can also be reduced to a level that can be effectively used in the manufacture of lithium ion batteries.

[0075] (crystallization process) A crystallization step for crystallizing cobalt ions or nickel ions can be performed on the cobalt solution (e.g., cobalt sulfate solution, cobalt hydrochloride solution, cobalt nitrate solution) obtained in the magnesium separation step after the cobalt extraction step and the nickel solution (e.g., nickel sulfate solution, nickel hydrochloride solution, nickel nitrate solution) obtained in the nickel extraction step. As a result, in the crystallization step using the cobalt solution, as shown in FIG. 2, it is possible to produce cobalt salts (e.g., cobalt sulfate, cobalt hydrochloride, cobalt nitrate). In addition, in the crystallization step using the nickel solution, it is possible to produce nickel salts (e.g., nickel sulfate, nickel hydrochloride, nickel nitrate). If necessary, a step such as solvent extraction may be performed before the crystallization step to remove impurities prior to crystallization.

[0076] In the crystallization step, the cobalt solution or nickel solution is concentrated by heating, for example, to 40° C. to 120° C. This causes the cobalt ions to crystallize as a cobalt salt, and the nickel ions to crystallize as a nickel salt.

[0077] The cobalt salts and nickel salts produced in this manner have impurities such as magnesium sufficiently removed, and therefore can be effectively used as raw materials for the production of lithium ion batteries.

[0078] (Magnesium removal process) In cases where the acidic solution obtained in the manganese / aluminum extraction step contains a relatively large amount of magnesium ions, the acidic solution may be subjected to a magnesium removal step. In particular, when the magnesium concentration of the acidic solution obtained in the manganese / aluminum extraction step exceeds 1.000 g / L, it is desirable to perform the magnesium removal step. In the magnesium removal step, the cobalt ions and nickel ions in the acidic solution obtained in the manganese / aluminum extraction step are extracted by a solvent extraction method, while some of the magnesium ions are left in the solution and removed. This makes it possible to suppress the transfer of a large amount of magnesium ions to the subsequent cobalt extraction step, and specifically, to make the magnesium concentration 1.000 g / L or less. If the magnesium concentration is 1.000 g / L or less, the cobalt solution obtained in the cobalt extraction step (including back extraction) and magnesium separation step can be used to manufacture lithium-ion batteries. At this time, when sodium ions are contained in the acidic solution, the sodium ions are also left in the solution and removed. However, the magnesium removal step is an optional step and can be omitted.

[0079] If it is attempted to completely remove magnesium ions in the magnesium removal step, the extraction of cobalt ions and nickel ions will be insufficient, resulting in losses of these ions. Therefore, the magnesium removal step is performed under conditions in which some of the magnesium ions remain in the liquid and are removed.

[0080] Specifically, cobalt ions and / or nickel ions are extracted using a solvent containing a carboxylic acid extractant, with an equilibrium pH during extraction of 6.8 to 7.2, preferably 6.9 to 7.0, and an O / A ratio of 1.0 to 1.5, preferably 1.0 to 1.2. This allows good phase separation while extracting most of the cobalt ions and nickel ions into the solvent (= organic phase), while leaving some of the magnesium ions in the post-extraction liquid (= aqueous phase) without extraction. The O / A ratio refers to the volume ratio of the organic phase to the aqueous phase.

[0081] Examples of the carboxylic acid extractant used in the extraction in the magnesium removal step include, but are not limited to, neodecanoic acid and naphthenic acid. Among them, neodecanoic acid is preferred from the viewpoint of extracting cobalt ions and nickel ions while extracting as little magnesium ions as possible. In addition, the carboxylic acid extractant preferably contains a carboxylic acid having 8 to 16 carbon atoms. Specifically, VA-10 and the like can be used.

[0082] In the stripping after extraction, the solvent from which the cobalt ions and nickel ions have been extracted as described above can be mixed with a stripping solution such as sulfuric acid or hydrochloric acid, and stirred for, for example, 5 to 60 minutes using a mixer or the like. In order to effectively strip manganese ions, cobalt ions, and nickel ions in the solvent, the acid concentration of the stripping solution is preferably adjusted to 0.05 g / L to 200 g / L (pH: -0.6 to 3.0), and more preferably adjusted to 1.5 g / L to 15 g / L (pH: 0.5 to 1.5). The temperature for stripping can be room temperature to 60°C, preferably 35°C to 45°C. EXAMPLES

[0083] Next, the above-mentioned methods for producing a cobalt solution, a cobalt salt, a nickel solution, and a nickel salt were experimentally carried out, and the effects thereof were confirmed, which will be described below, however, the description here is merely for illustrative purposes and is not intended to be limiting.

[0084] (Method of manufacturing cobalt solution) The battery powder of the lithium-ion battery waste was subjected to a leaching process, a neutralization process, a manganese / aluminum extraction process, and a cobalt extraction process, and a cobalt-containing solution was obtained as a back-extracted liquid of the cobalt extraction process. The cobalt-containing solution had a cobalt ion concentration of 15 g / L and a magnesium ion concentration of 1.000 g / L.

[0085] The cobalt-containing solution was subjected to the magnesium separation process. The solvent used here was 25% by volume of VA-10, a carboxylic acid extractant, diluted with Shellsol D70 ("Shellsol" is a registered trademark of Shell Chemical Co., Ltd.), and contained 25% by volume of VA-10 and 75% by volume of Shellsol D70. The O / A ratio during extraction was 2 / 1, and 25% by volume of NaOH was used as a pH adjuster. When extraction was performed by changing the equilibrium pH, the results shown in FIG. 3 were obtained. FIG. 3 is a graph showing the relationship between the extraction rate of each ion into the solvent and the equilibrium pH during extraction. Table 1 also shows the values ​​of each plot in FIG. 3. The extraction rate of each ion into the solvent was calculated from the ratio of the amount calculated from the concentration of each ion and the liquid volume of the back-extracted liquid obtained by performing back extraction on the solvent to the amount calculated from the concentration of each ion and the liquid volume of the back-extracted liquid obtained by performing back extraction on the solvent after that, to the amount calculated from the concentration of each ion and the liquid volume of the cobalt-containing solution before solvent extraction. Back extraction was performed under the conditions of sulfuric acid at pH 1.0 and an O / A ratio of 1 / 1.

[0086] [Table 1]

[0087] From Figure 3, it can be seen that cobalt ions and magnesium ions can be effectively separated by using a solvent containing a carboxylic acid extractant. In particular, if the equilibrium pH is set to 6.0 to 7.0, it is possible to extract a large amount of cobalt ions while sufficiently suppressing the extraction of magnesium ions. Furthermore, no precipitate was observed in the aqueous phase during the extraction of cobalt ions. This is thought to be due to the fact that the concentration of VA-10 in the solvent was maintained at about 25% by volume during the extraction.

[0088] In addition, the solvent from which the cobalt ions were extracted was subjected to scrubbing, followed by back extraction. A sulfuric acid acidic solution with a cobalt ion concentration of 10 g / L was used as the scrubbing liquid. The cobalt ion concentration of the solvent before scrubbing was 7.6 g / L, the magnesium ion concentration was 0.1 g / L, and the sodium ion concentration was 0.1 g / L. The ion concentrations of this solvent were calculated from the ion concentrations of the liquid after back extraction of the solvent. The O / A ratio during scrubbing was 1 / 1. The back extraction was performed using 500 g / L sulfuric acid with an O / A ratio of 1 / 1. A cobalt sulfate solution was obtained by this back extraction.

[0089] A test was conducted in which the equilibrium pH during scrubbing was changed, and the graph shown in Figure 4 was obtained as the removal rate of each ion in the liquid after stripping versus the pH of scrubbing. The removal rate was calculated from the ratio of the amount calculated from the concentration of each ion in the liquid after stripping to the solvent after scrubbing and the amount of liquid, to the amount calculated from the concentration of each ion in the liquid after stripping to the solvent before scrubbing and the amount of liquid. Note that the removal rate may fall below 0% due to the migration of cobalt ions in the scrubbing liquid to the solvent. In this case, the removal rate is set to 0%. Table 2 also shows the values ​​of each plot in Figure 4. As can be seen from Figure 4, magnesium ions and sodium ions were effectively removed by scrubbing. In particular, in the test in which the pH of scrubbing was 6.0 or less, it can be seen that both magnesium ions and sodium ions were below the detection limit. On the other hand, if the pH of scrubbing is too low, there is a concern that not only magnesium ions and sodium ions but also cobalt ions will be removed by scrubbing.

[0090] [Table 2]

[0091] In addition, the cobalt sulfate shown in Table 3 was obtained by carrying out a crystallization process on the cobalt sulfate solution obtained by performing back extraction after scrubbing. In this way, cobalt sulfate with a magnesium content of 10 mass ppm or less was obtained. In addition, the nickel content, manganese content, aluminum content, iron content, and sodium content of the cobalt sulfate were all 10 mass ppm or less. In this way, it was confirmed that impurities were removed to an extent that the product could be effectively used in the manufacture of lithium-ion batteries. [Table 3]

[0092] From the above, it was found that the above-mentioned method for producing a cobalt solution makes it possible to effectively remove magnesium ions from a cobalt-containing solution that also contains magnesium ions.

[0093] (Method of manufacturing nickel solution) The battery powder of lithium-ion battery waste was subjected to the leaching process, neutralization process, manganese / aluminum extraction process, and cobalt extraction process. The nickel ion concentration of the extracted solution from the cobalt extraction process was 7g / L, the magnesium ion concentration was 0.6g / L, and the sodium ion concentration was 40g / L.

[0094] The above post-extraction liquid was subjected to a nickel extraction process. The solvent used here was a carboxylic acid extractant VA-10 diluted with Shellsol D70 ("Shellsol" is a registered trademark of Shell Chemical Co.) and contained 25% by volume of VA-10 and 75% by volume of Shellsol D70. The O / A ratio during extraction was 1 / 1, and 25% by volume of NaOH was used as a pH adjuster. When extraction was performed by changing the equilibrium pH, the results shown in FIG. 5 were obtained. FIG. 5 is a graph showing the relationship between the extraction rate of each ion into the solvent and the equilibrium pH during extraction. Table 4 also shows the values ​​of each plot in FIG. 5. The extraction rate of each ion into the solvent was calculated from the ratio of the amount calculated from the concentration of each ion and the liquid volume of the post-extraction liquid obtained by performing back extraction on the solvent after the solvent extraction to the amount calculated from the concentration of each ion and the liquid volume of the post-extraction liquid before the solvent extraction. The back extraction was performed under the conditions of sulfuric acid at pH 1.0 and an O / A ratio of 1 / 1.

[0095] [Table 4]

[0096] It can be seen from FIG. 5 that by using a solvent containing a carboxylic acid extractant and setting the equilibrium pH to 6.3 to 7.5, nickel ions can be effectively extracted while suppressing the extraction of magnesium ions.

[0097] In addition, the solvent from which the nickel ions were extracted was subjected to scrubbing, followed by back extraction. A sulfuric acid acid solution with a nickel ion concentration of 10 g / L was used as the scrubbing liquid. The nickel ion concentration of the solvent before scrubbing was 7 g / L, the magnesium ion concentration was 0.5 g / L, and the sodium ion concentration was 1 g / L. The ion concentrations of this solvent were calculated from the ion concentrations of the liquid after back extraction of the solvent. The O / A ratio during scrubbing was 1 / 1. The back extraction was performed using 500 g / L sulfuric acid with an O / A ratio of 1 / 1. A nickel sulfate solution was obtained by this back extraction.

[0098] A test was conducted in which the equilibrium pH during scrubbing was changed, and the graph shown in Figure 6 was obtained, showing the removal rate of each ion in the liquid after stripping versus the pH of scrubbing. The removal rate was calculated from the ratio of the amount calculated from the concentration of each ion in the liquid after stripping to the solvent after scrubbing and the amount of liquid, to the amount calculated from the concentration of each ion in the liquid after stripping to the solvent before scrubbing and the amount of liquid. Note that the removal rate may fall below 0% due to the migration of nickel ions in the scrubbing liquid to the solvent. In this case, the removal rate is set to 0%. Table 5 also shows the values ​​of each plot in Figure 6. As can be seen from Figure 6, magnesium ions and sodium ions were effectively removed by performing scrubbing. In particular, in the test in which the pH of scrubbing was set to 5.5 or higher, nickel ions were hardly removed.

[0099] [Table 5]

[0100] In addition, nickel sulfate shown in Table 6 was obtained by carrying out a crystallization process on the nickel sulfate solution obtained by performing back extraction after scrubbing. In this way, nickel sulfate with a magnesium content of 10 mass ppm or less was obtained. In addition, the cobalt content, manganese content, aluminum content, iron content, and sodium content of the nickel sulfate were all 10 mass ppm or less. In this way, it was confirmed that impurities were removed to an extent that the nickel sulfate could be effectively used in the manufacture of lithium-ion batteries. [Table 6]

[0101] From the above, it was found that the above-mentioned method for producing a nickel solution can effectively remove magnesium ions from a nickel-containing solution that also contains magnesium ions.

Claims

1. A method for producing a cobalt solution by removing magnesium ions from a cobalt-containing solution obtained by subjecting battery powder of lithium-ion battery waste to at least a leaching treatment, the cobalt-containing solution containing magnesium ions, the method comprising the steps of: a magnesium separation step of extracting cobalt ions from the cobalt-containing solution using a solvent containing a carboxylic acid extractant to separate magnesium ions, and then stripping the cobalt ions from the solvent to obtain the cobalt solution as a stripped liquid.

2. 2. The method for producing a cobalt solution according to claim 1, wherein the equilibrium pH when cobalt ions are extracted in the magnesium separation step is 6.0 to 7.

0.

3. 3. The method for producing a cobalt solution according to claim 1, wherein in the magnesium separation step, the solvent from which cobalt ions have been extracted is scrubbed at an equilibrium pH of 5.5 to 6.5 before stripping.

4. 3. The method for producing a cobalt solution according to claim 1, wherein the magnesium ion concentration of the cobalt-containing solution is 0.002 g / L to 1.000 g / L.

5. 3. The method for producing a cobalt solution according to claim 1, wherein in the magnesium separation step, cobalt ions are stripped from the solvent using a stripping solution containing sulfuric acid, hydrochloric acid or nitric acid, and the pH during stripping is set to 1.0 to 4.

0.

6. 3. The method for producing a cobalt solution according to claim 1, wherein a concentration of the carboxylic acid extractant in the solvent used for extracting cobalt ions in the magnesium separation step is 25% by volume to 30% by volume.

7. 3. The method for producing a cobalt solution according to claim 1 or 2, wherein in the magnesium separation step, a post-extraction solution obtained after extraction of cobalt ions contains a carboxylic acid extractant, the carboxylic acid extractant is recovered from the post-extraction solution by adjusting the equilibrium pH to 5.5 or less, and the carboxylic acid extractant recovered from the post-extraction solution is used for extracting cobalt ions.

8. 3. The method for producing a cobalt solution according to claim 1 or 2, further comprising a cobalt extraction step of extracting a portion of cobalt ions and magnesium ions from a metal-containing solution containing cobalt ions, nickel ions and magnesium ions using a solvent containing a phosphonate ester extractant, and then back-extracting at least cobalt ions from the solvent to obtain the cobalt-containing solution.

9. 9. The method for producing a cobalt solution according to claim 8, wherein the magnesium ion concentration of the metal-containing solution is 0.002 g / L to 1.000 g / L.

10. 9. The method for producing a cobalt solution according to claim 8, further comprising a magnesium removal step of performing extraction and stripping, with a solvent containing a carboxylic acid-based extractant, on an acidic solution containing cobalt ions, nickel ions and magnesium ions to remove a portion of the magnesium ions and obtain the metal-containing solution.

11. 9. The method for producing a cobalt solution according to claim 8, further comprising a nickel extraction step of extracting nickel ions from a post-extraction solution obtained by the extraction in the cobalt extraction step using a solvent containing a carboxylic acid-based extractant, and back-extracting the nickel ions from the solvent.

12. The method for producing a cobalt solution according to claim 11, wherein the equilibrium pH when nickel ions are extracted in the nickel extraction step is 6.3 to 7.

5.

13. The method for producing a cobalt solution according to claim 11, wherein in the nickel extraction step, the solvent from which nickel ions have been extracted is scrubbed at an equilibrium pH of 5.5 to 6.5 before stripping.

14. A method for producing a cobalt salt using the method for producing a cobalt solution according to claim 1 or 2, comprising the steps of: A method for producing a cobalt salt, comprising: a crystallization step of crystallizing a cobalt salt from the cobalt solution obtained in the magnesium separation step.

15. A method for producing a nickel solution by removing magnesium ions from a nickel-containing solution obtained by subjecting battery powder of lithium-ion battery waste to at least a leaching treatment, the nickel-containing solution containing cobalt ions and magnesium ions at a concentration of 0.002 g / L to 1.000 g / L, the method comprising: a cobalt extraction step of extracting a portion of cobalt ions and magnesium ions from the nickel-containing solution using a solvent containing a phosphonate ester-based extractant; a nickel extraction step in which the post-extraction solution obtained after the extraction in the cobalt extraction step contains nickel ions and magnesium ions at a concentration of 0.001 g / L to 0.610 g / L is subjected to an equilibrium pH of 6.3 to 7.5 using a solvent containing a carboxylic acid-based extractant to extract nickel ions and separate magnesium ions, and then the nickel ions are stripped from the solvent to obtain the nickel solution as a stripped solution; A method for producing a nickel solution comprising:

16. The method for producing a nickel solution according to claim 15, wherein the solvent from which nickel ions have been extracted in the nickel extraction step is scrubbed at an equilibrium pH of 5.5 to 6.5 before stripping.

17. The method for producing a nickel solution according to claim 15 or 16, further comprising a magnesium removal step of subjecting an acidic solution containing cobalt ions, nickel ions and magnesium ions to extraction and stripping with a solvent containing a carboxylic acid-based extractant to remove a portion of the magnesium ions and obtain the nickel-containing solution.

18. A method for producing a nickel salt using the method for producing a nickel solution according to claim 15 or 16, comprising the steps of: A method for producing a nickel salt, comprising: a crystallization step of crystallizing a nickel salt from the nickel solution obtained in the nickel extraction step.

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