Metal recovery device and metal recovery method

Abstract

To provide an environment-friendly recovery apparatus of metal that is not accompanied by leaching with a high-concentration inorganic acid or extraction with an organic solvent.SOLUTION: A recovery apparatus of metal and a recovery method of metal are provided. The recovery apparatus of metal includes a leaching unit for leaching at least one metal component contained in a metal-element-containing composition directly into a hydrophobic deep eutectic solvent and a recovery unit for separating and recovering the metal component from the deep eutectic solvent. The metal-element-containing composition is solid at 25°C and does not contain an inorganic acid. The metal component is a metal, a metal compound or a metal ion. The deep eutectic solvent does not contain an inorganic acid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a metal recovery device and a metal recovery method. [Background technology]

[0002] To efficiently utilize resources, there is a demand for metal recovery equipment for metal refining and recycling. For example, in recent years, the spread of lithium-ion batteries (LiBs) has led to an increase in demand for rare metals such as cobalt and nickel, which are used in anode materials (active materials for cathodes). Due to issues such as uneven distribution of these metals in production areas and resource depletion, there is a demand for technology to recycle rare metals from discarded LiBs. Traditionally, recycling has been carried out using pyrometallurgy, but issues such as energy consumption and insufficient purity have led to the development of hydrometallurgy. Hydrometallurgy involves leaching anode materials into solution using an acid or other solvent, followed by the individual recovery of the target metals using solvent extraction or precipitation. The oxidation state of Co in LiCoO2, a typical anode material, is +3, and because the oxide is stable, it is difficult to dissolve in aqueous solution. Therefore, a leaching method is known in which Co(II) is produced by using a reducing agent in combination with an inorganic acid, which is then efficiently leached into the aqueous phase. However, this method raises concerns about environmental pollution due to the large amount of acid wastewater generated. In response to this, deep eutectic solvents (DES) and ionic liquids have attracted attention as environmentally friendly leaching media (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 describes an ionic compound with a freezing point of up to 100°C, which is formed by reacting at least one amine salt represented by a specific structure with at least one organic compound (II) capable of forming hydrogen bonds with a specific anion. [Patent Document 1] paragraph

[0055] states that one such ionic liquid, a 2:1 urea-choline chloride ionic liquid, can be used to extract metal oxides from ores, and that such metals can be extracted from the ionic liquid by electrowinning. [Patent Document 1] paragraphs

[0058] to

[0060] also state that such a carboxylic acid (oxalic acid)-choline chloride ionic liquid can be used to recover precious metals, particularly platinum and palladium, from materials and substances containing oxides, and that Pd can be recovered from automotive catalyst materials containing PdO supported on an alumina support.

[0004] Patent Document 2 describes a rare earth extractant containing a diketone and a neutral extractant, and also describes that this rare earth extractant can selectively extract rare earths even in a low pH range. Specifically, Patent Document 2 describes a rare earth extractant containing a diketone (2-thenoyltrifluoroacetone; melting point 40-44°C) and a neutral extractant (trioctylphosphine oxide; TOPO), and paragraph

[0030] suggests that the extractant is liquid at room temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2004-509945 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-057505 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 uses a hydrophilic ionic liquid or deep eutectic solvent that uses hydrophilic urea or oxalic acid, and requires that the metal components be leached into the ionic liquid phase or deep eutectic solvent phase, then contacted with an organic solvent to extract the metal components into the organic phase, and then contacted with a hydrophilic solvent for recovery. Because extraction is performed using an organic solvent, further improvements are needed to make this an environmentally friendly metal recovery method.

[0007] The method described in Patent Document 2 involves leaching metal components from a metal element-containing composition with acid, and then applying a rare earth extractant to the acidic solution from which the metal components have been leached. Therefore, the metal components of a solid metal element-containing composition are not directly leached into a hydrophobic deep eutectic solvent that does not contain inorganic acids, and acid waste liquid is generated. Further improvements are needed to make this an environmentally friendly metal recovery method. Furthermore, the method uses a rare earth extractant prepared by dissolving a diketone and a neutral extractant in an organic solvent diluent (toluene), which essentially requires a certain amount of organic solvent for extraction. Therefore, further improvements are needed to make this an environmentally friendly metal recovery method.

[0008] The problem to be solved by the present invention is to provide an environmentally friendly metal recovery device that does not involve leaching with a highly concentrated inorganic acid or extraction with an organic solvent. [Means for solving the problem]

[0009] As a result of extensive research, the inventors have discovered that the problem of acid waste liquid can be solved by directly contacting a solid metal element-containing composition with a deep eutectic solvent instead of the acid used in conventional leaching methods using inorganic acids, and that by using a hydrophobic deep eutectic solvent, metals can be recovered by directly contacting the composition with a hydrophilic solvent without extraction with an organic solvent, thereby solving the above-mentioned problems. The configuration of the present invention, which is a specific means for solving the above problems, and a preferred configuration of the present invention will be described below.

[0010] [1] A leaching unit that directly leaches at least one metal component contained in a metal element-containing composition into a hydrophobic deep eutectic solvent; a recovery unit that separates and recovers the metal component from the deep eutectic solvent; the metal element-containing composition is solid at 25°C and does not contain an inorganic acid; the metal component is a metal, a metal compound, or a metal ion; A metal recovery device in which the deep eutectic solvent does not contain inorganic acids. [2] The metal recovery device according to [1], wherein the hydrophobicity of the deep eutectic solvent is 1 g / 100 mL or less in terms of solubility in water at 25°C. [3] A metal recovery device according to [1] or [2], wherein the deep eutectic solvent does not contain an organic solvent having a boiling point of 150°C or less by itself. [4] A metal recovery device according to any one of [1] to [3], in which an extraction step of transferring metal components from a deep eutectic solvent to another organic solvent is not carried out between the leaching section and the recovery section. [5] The metal recovery device according to any one of [1] to [4], wherein the deep eutectic solvent is liquid at 25°C. [6] The metal element-containing composition contains two or more metal components, The metal recovery device according to any one of [1] to [5], wherein the deep eutectic solvent selectively leaches a specific type of metal component among two or more types of metal components at a higher concentration than the other types of metal components. [7] A deep eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors, At 25°C, the hydrogen bond donor and the hydrogen bond acceptor are in the form of solid particles before mixing, The metal recovery device according to any one of [1] to [6], wherein the metal component is brought into contact with the deep eutectic solvent by directly contacting a hydrogen bond donor and a hydrogen bond acceptor in the form of solid particles with the metal-containing composition. [8] A deep eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors, the hydrogen bond donor is benzoyltrifluoroacetone or decanoic acid; The metal recovery device according to any one of [1] to [7], wherein the hydrogen bond acceptor is tri-n-octylphosphine oxide. [9] A deep eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors, The metal recovery device according to any one of [1] to [8], wherein the concentration of the hydrogen bond donor is controlled to be 1.2 to 5 times the concentration of the hydrogen bond acceptor.

[10] The metal element-containing composition contains a metal oxide, The metal recovery device according to any one of [1] to [9], wherein a reducing agent is further added to the deep eutectic solvent.

[11] The metal recovery device according to

[10] , wherein the reducing agent is L-ascorbic acid, citric acid or malic acid.

[12] The metal recovery device according to

[10] or

[11] , wherein the concentration of the reducing agent is controlled to 0.03 to 0.30 mol / L relative to the deep eutectic solvent.

[13] The metal element-containing composition is LiCoO2 or LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 The metal recovery device according to any one of

[10] to

[12] , which contains O2.

[14] The metal element-containing composition contains a platinum group metal or a platinum group metal compound, The metal recovery device according to any one of [1] to [9], wherein an oxidizing agent is further added to the deep eutectic solvent.

[15] The metal recovery device according to any one of [1] to

[14] , wherein the water content of the deep eutectic solvent is controlled to 0.3 to 2.8 mass %.

[16] The metal recovery device according to any one of [1] to

[15] , wherein the recovery unit brings a hydrophilic solvent into contact with the deep eutectic solvent, and separates and recovers the metal components in the hydrophilic solvent.

[17] The metal recovery device according to

[16] , in which a chelating agent is added to the hydrophilic solvent, and the metal components are precipitated as salts in the hydrophilic solvent, and then separated and recovered.

[18] A metal recovery device according to any one of [1] to

[17] , comprising a recycling section that returns the deep eutectic solvent from which the metal components have been separated in the recovery section to the leaching section for reuse.

[19] The metal recovery device according to

[18] , wherein the recycling unit washes the deep eutectic solvent using a cleaning liquid capable of removing the chelating agent.

[20] A metal recovery device as described in

[18] or

[19] , in which when the cycle of the leaching section, recovery section and recycling section is repeated three times using only the deep eutectic solvent returned by the recycling section in the leaching section, the leaching rate of the metal components as expressed by the following formula 1 is 80% or more, and the recovery rate of the metal components as expressed by the following formula 2 is 95% or more. formula 1

number

number

[21] A leaching step of directly leaching at least one metal component contained in a metal element-containing composition into a hydrophobic deep eutectic solvent; and a recovery step of separating and recovering the metal component from the deep eutectic solvent, the metal element-containing composition is solid at 25°C and does not contain an inorganic acid; the metal component is a metal, a metal compound, or a metal ion; A method for recovering metals, wherein the deep eutectic solvent does not contain inorganic acids. [Effects of the Invention]

[0011] According to the present invention, an environmentally friendly metal recovery device can be provided that does not involve leaching with a high-concentration inorganic acid or extraction with an organic solvent. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of an example of a metal recovery device of the present invention. [Figure 2] Figure 2 is a schematic diagram of a metal recovery device using a hydrophilic deep eutectic solvent. [Figure 3] FIG. 3 is a schematic diagram of a metal recovery device using an inorganic acid leaching method. [Figure 4] FIG. 4 is a bar graph showing the leaching rates of Li and Co in the metal recovery methods of Examples 1-8. [Figure 5] FIG. 5 is a bar graph showing the leaching rates of Li and Co in the metal recovery methods of Examples 11-14. [Figure 6] FIG. 6 is a bar graph showing the leaching rates of Li and Co in the metal recovery methods of Examples 21-24. [Figure 7] FIG. 7 is a stacked bar graph showing the abundance ratios of Li and Co in the deep eutectic solvent (DES) phase, the aqueous phase, and the precipitate in the metal recovery methods of Examples 31 to 33. [Figure 8] FIG. 8 is a bar graph showing the leaching rate %L and recovery rate %S of Li and Co for each cycle in the metal recovery method of Example 41. [Figure 9] FIG. 9 is a bar graph showing the leaching rates %L and recovery rates %S of Li, Mn, Co, and Ni for the metal recovery methods of Examples 51 and 52. [Figure 10] FIG. 10 is an electron microscope photograph of the anode material before leaching, the anode material of Example 52 after leaching, and the anode material of Comparative Example 53 after leaching, taken with a scanning electron microscope equipped with an X-ray spectrometer (SEM-EDS). [Figure 11] FIG. 11 is an EDS chart of elemental analysis of the anode material before leaching using an energy dispersive X-ray spectrometer (EDS). [Figure 12]FIG. 12 is an EDS chart of elemental analysis of the anode material of Example 52 after leaching, performed using an energy dispersive X-ray spectrometer. [Figure 13] FIG. 13 is an EDS chart of elemental analysis by energy dispersive X-ray spectroscopy of the anode material after leaching in Comparative Example 53. [Figure 14] FIG. 14 is a schematic diagram of another example of the metal recovery device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. The following description of the constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0014] [Metal recovery equipment] The metal recovery device of the present invention includes: a leaching unit that directly leaches at least one metal component contained in a metal element-containing composition into a hydrophobic deep eutectic solvent; a recovery unit that separates and recovers the metal component from the deep eutectic solvent; the metal element-containing composition is solid at 25°C and does not contain an inorganic acid; the metal component is a metal, a metal compound, or a metal ion; The deep eutectic solvent does not contain inorganic acids. This configuration makes it possible to provide an environmentally friendly metal recovery device that does not involve leaching with a highly concentrated inorganic acid or extraction with an organic solvent. Preferred embodiments of the present invention will now be described.

[0015] <Metal recovery method> A preferred embodiment of the metal recovery apparatus of the present invention will be described together with the metal recovery method of the present invention with reference to the drawings. The metal recovery method of the present invention comprises a leaching step of directly leaching at least one metal component contained in a metal element-containing composition into a hydrophobic deep eutectic solvent, and a recovery step of separating and recovering the metal component from the deep eutectic solvent, wherein the metal element-containing composition is solid at 25°C and does not contain inorganic acids, the metal component is a metal, metal compound, or metal ion, and the deep eutectic solvent does not contain inorganic acids. Preferred embodiments of the metal recovery method of the present invention are the same as the preferred embodiments of the metal recovery apparatus of the present invention. FIG. 1 is a schematic diagram of an example of a metal recovery device of the present invention. The metal recovery device shown in Figure 1 includes a leaching section that directly leaches at least one metal component contained in a metal element-containing composition into a hydrophobic deep eutectic solvent, and a recovery section that separates and recovers the metal component from the deep eutectic solvent. First, metal components (Li, Co) are leached from a metal element-containing composition using a hydrophobic deep eutectic solvent, and the target metal components are dissolved (leached) in the hydrophobic deep eutectic solvent (DES phase). Next, in the recovery section, the hydrophobic deep eutectic solvent from which the metal components have leached is brought into contact with a hydrophilic solvent (aqueous phase), and the target metal components (Li, Co) are completely recovered from the hydrophobic deep eutectic solvent into the hydrophilic solvent. As shown in Figure 1, some types of target metal components (Co) are recovered as precipitates, which are salts of the metal components, and other types of metal components (Li) can be recovered as metal ions in the hydrophilic solvent. The metal recovery device shown in Figure 1 further transfers the deep eutectic solvent from which the metal components have been separated to a recycling section, and then reuses the deep eutectic solvent in the leaching section. However, the recycling section is not an essential component of the metal recovery device of the present invention.

[0016] It is preferable that the metal recovery device does not perform an extraction process in which metal components are transferred from the deep eutectic solvent to another organic solvent between the leaching section and the recovery section. By using a hydrophobic deep eutectic solvent, the extraction process can be omitted and the solvent can be used for both the leaching and recovery processes. Here, examples of metal recovery devices using conventional hydrometallurgy are shown in Figures 2 and 3. Figure 2 is a schematic diagram of a metal recovery device using a hydrophilic deep eutectic solvent. The metal recovery device in Figure 2 includes a leaching section that directly leaches the metal components contained in a metal element-containing composition into a hydrophilic deep eutectic solvent, an extraction section that transfers the metal components from the hydrophilic deep eutectic solvent to another organic solvent (organic phase), and a recovery section that transfers the metal components from the organic solvent to a hydrophilic solvent, where they are separated and recovered. Figure 3 is a schematic diagram of a metal recovery device using an inorganic acid leaching method. The metal recovery device in Figure 3 includes a leaching section that leaches the metal components contained in the metal element-containing composition into an inorganic acid-containing aqueous solution (aqueous phase), an extraction section that transfers one of the metal components (Co) from the inorganic acid-containing aqueous solution to an organic solvent (organic phase) for separation, and a recovery section that transfers the metal component (Co) from the organic solvent to a hydrophilic solvent for separation and recovery. Currently, the metal recovery device in Figure 3 is used in the recycling of home appliances. The metal element-containing composition is crushed into powder, and as many metals as possible are dissolved in an aqueous solution containing an inorganic acid. The powder is then transferred to an organic solvent containing an extractant, a compound that can selectively extract rare metals such as Co. Selective leaching of metal components is difficult with the metal recovery device in Figure 3.

[0017] <Leaching part> In the leaching section, at least one metal component contained in the metal element-containing composition is directly leached into a hydrophobic deep eutectic solvent. Furthermore, it is preferable that the leaching efficiency in the leaching section is high. The leaching rate of the metal components is preferably 10% or more, more preferably 20% or more, particularly preferably 50% or more, even more particularly preferably 70% or more, and even more particularly preferably 80% or more. It is preferable that the leaching zone has high selectivity for metal components. In particular, it is preferable to selectively leach only rare metals such as Co, Ni, and platinum group elements. On the other hand, it is preferable that the leaching zone has a low leaching rate for Fe, Al, Si, Ti, etc. The selectivity for metal components in the leaching zone can be controlled by the type and mixing ratio of the deep eutectic solvent, and the type and amount of the reducing agent or oxidizing agent.

[0018] (Metal element-containing composition) In the present invention, the metal element-containing composition contains at least one metal component, is solid at 25° C., and does not contain inorganic acids. By using a metal element-containing composition that is solid at 25°C, it is not necessary to dissolve the metal element-containing composition in a solvent, dispersion medium, inorganic acid, etc. before the recovery process in the recovery section, and it is also not necessary to adjust the pH, making it possible to provide an environmentally friendly metal recovery device. Furthermore, by using such a deep eutectic solvent that does not contain an inorganic acid, it is possible to provide an environmentally friendly metal recovery device. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and aqua regia.

[0019] In the present invention, the metal component contained in the metal element-containing composition is a metal, a metal compound, or a metal ion. The type of the metal element-containing composition is not particularly limited. For example, the metal element-containing composition may contain a metal compound such as a metal oxide, or may contain a metal, but preferably contains a metal oxide. When the metal element-containing composition contains a metal, it preferably contains an alkali metal, an alkaline earth metal or a transition metal, and more preferably contains an alkali metal or a transition metal. Among the alkali metals, it is preferable to contain Li from the viewpoint of recycling batteries such as lithium ion batteries. Among transition metals, it is more preferable to contain a first transition element (3d transition element), a second transition element (4d transition element), or a third transition element, and it is particularly preferable to contain a second transition element or a third transition element. Among the first transition elements, it is preferable to contain Mn, Co, or Ni. Among the second transition elements and third transition elements, it is more preferable to contain a platinum group metal. When the metal element-containing composition contains a metal compound or metal ion, the preferred types of metal components are the same as those in the case of metals. The metal recovery device of the present invention is useful for separating rare metals and recycling batteries. When the metal recovery device of the present invention is used for recycling batteries such as lithium ion batteries, the metal element-containing composition preferably contains a metal oxide, more preferably a metal oxide containing Li, such as LiCoO2 or LiNi, which are often used as anode materials for lithium ion batteries. 1 / 3 Mn 1 / 3 Co 1 / 3 It is particularly preferred that the metal recovery device of the present invention contains O2. When the metal recovery device of the present invention is used to recycle rare metals from automobile exhaust catalysts, it is preferred that the metal recovery device contains a metal such as platinum, palladium, or rhodium or a metal compound thereof, more preferably a platinum group metal or a platinum group metal compound, and particularly preferably a platinum group metal. When the metal recovery device of the present invention is used to recycle rare metals from ores, it is preferred that the metal recovery device contains a metal such as Ni or Co or a metal compound thereof (particularly a metal oxide).

[0020] (deep eutectic solvent) In the present invention, a hydrophobic deep eutectic solvent is used as the deep eutectic solvent. A deep eutectic solvent is a material prepared as a liquid at 25°C by lowering the melting point by mixing two or more compounds. Deep eutectic solvents preferably have excellent properties such as low volatility, flame retardancy, and designability. Deep eutectic solvents exhibit excellent performance in dissolving metal oxides due to their specific metal coordination ability and acidity. The compounds used to prepare the deep eutectic solvent may be two or more types, for example, three to five types. A hydrophobic deep eutectic solvent is a deep eutectic solvent that is immiscible with water. The hydrophobicity of the deep eutectic solvent is preferably such that its solubility in water at 25°C is 1 g / 100 mL or less, more preferably 0.1 g / 100 mL or less, and particularly preferably 0.01 g / 100 mL or less.

[0021] When the metal element-containing composition contains two or more types of metal components, it is preferable that the deep eutectic solvent selectively leaches a specific type of metal component among the two or more types of metal components at a higher concentration than the other types of metal components.

[0022] The deep eutectic solvent is preferably prepared by mixing two or more hydrogen-bonding compounds, i.e., the deep eutectic solvent is preferably a mixture of hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs). Examples of hydrogen bond donors include compounds with hydroxyl groups such as alcohols and compounds with carboxyl groups, with compounds with metal-coordinating functional groups being preferred. Examples of hydrogen bond donors include fatty acids, urea, glucose, glycerol, benzoyltrifluoroacetone (HBTA), and decanoic acid (decA). Among these, hydrophobic hydrogen bond donors such as octylphenol, diphenyl phosphate, fatty acid amines, fatty acid amides, long-chain alkylbenzene sulfonic acids, fatty acids, benzoyltrifluoroacetone (HBTA), and decanoic acid (decA) are preferred. In the present invention, benzoyltrifluoroacetone or decanoic acid is preferred as the hydrogen bond donor from the viewpoint of increasing leaching efficiency. Examples of hydrogen bond acceptors include compounds with a lone pair of electrons, such as amine compounds, choline chloride, ethers, ketones, and amides. Among these, hydrophobic hydrogen bond acceptors such as tetraoctylammonium chloride, tetrabutylphosphonium chloride, trioctylamine, diphenyl sulfoxide, diphenylamine, stearylamine, triphenyl phosphate, betaine, tetrabutylammonium bromide, and tri-n-octylphosphine oxide (TOPO) are preferred. In the present invention, it is preferable that the hydrogen bond acceptor be tri-n-octylphosphine oxide, from the viewpoint of increasing leaching efficiency.

[0023] There are no particular limitations on the ratio of the concentration of the hydrogen bond donor to the concentration of the hydrogen bond acceptor, and for example, the concentration of the hydrogen bond donor may be 0.1 to 10 times the concentration of the hydrogen bond acceptor. In the present invention, from the viewpoint of facilitating leaching of metal components at lower pH levels, it is preferable to control the concentration of the hydrogen bond donor to 1.2 to 5 times the concentration of the hydrogen bond acceptor, more preferably 1.5 to 3 times, and particularly preferably 2 to 2.5 times.

[0024] Deep eutectic solvents may contain other components in addition to hydrogen bond donors and hydrogen bond acceptors, such as water, reducing agents, and oxidizing agents.

[0025] -Water content of deep eutectic solvent- In the present invention, the water content of the deep eutectic solvent is preferably controlled to 0.2 mass% or more, more preferably 0.3 to 2.8 mass% from the viewpoint of increasing leaching efficiency, and particularly preferably 1.0 to 2.5 mass%.

[0026] -Reducing agent- When the metal element-containing composition contains a metal oxide, it is preferable to further add a reducing agent to the deep eutectic solvent. The type of reducing agent is not particularly limited, and known reducing agents can be used. A reducing agent can be selected according to the required reducing power depending on the type of metal-element-containing composition. In the present invention, it is preferable that the reducing agent has the ability to coordinate to metals. Specifically, it is more preferable that the reducing agent has two or more hydroxyl groups in the molecule, particularly preferably three or more hydroxyl groups in the molecule, and even more particularly preferably four or more hydroxyl groups in the molecule. As reducing agents capable of coordinating to metals, L-ascorbic acid, citric acid, or malic acid is preferred, and L-ascorbic acid is more preferred from the viewpoint of increasing leaching efficiency. The reducing agents may be used alone or in combination of two or more. The concentration of the reducing agent is not particularly limited. In the present invention, from the viewpoint of increasing leaching efficiency, the reducing agent is preferably controlled to 0.03 to 0.30 mol / L relative to the deep eutectic solvent, more preferably 0.06 to 0.25 mol / L, particularly preferably 0.07 to 1.9 mol / L, and even more particularly preferably 1.1 to 1.8 mol / L.

[0027] -Oxidizing agent- When the metal element-containing composition contains a platinum group metal or a platinum group metal compound, it is preferable to further add an oxidizing agent to the deep eutectic solvent. The type of oxidizing agent is not particularly limited, and any known oxidizing agent can be used. The oxidizing agent can be selected according to the type of metal element-containing composition and the required oxidizing power. The oxidizing agents may be used alone or in combination of two or more.

[0028] At 25°C, it is preferred that the hydrogen bond donor and hydrogen bond acceptor are in the form of solid particles before mixing. From the viewpoint of reducing the process for preparing the deep eutectic solvent, it is preferable to bring the metal component into contact with the deep eutectic solvent by directly contacting the hydrogen bond donor and hydrogen bond acceptor, which are in the form of solid particles, with the metal-containing composition.

[0029] Room-temperature ionic liquids are known as media that are not deep eutectic solvents but have similar functions. Ionic liquids are also called ionic liquids or low-melting-point molten salts. Ionic liquids are salts that exist in liquid form. Room-temperature ionic liquids are ionic liquids that are in liquid form at 25°C and 1 atmosphere. Ionic liquids are primarily composed of a single compound, and can ionize to have a positive or negative charge. Ionic liquids are sometimes used in combination with other organic solvents, but the combination does not involve hydrogen bonding between the two. Using a hydrophobic deep eutectic solvent results in higher leaching and recovery efficiencies than when using ionic liquids. However, typical single ionic liquids have little ability to leach metal components, and ionic liquids must be used in combination with a reducing agent. Furthermore, ionic liquids are expensive and difficult to use industrially. Hydrophobic deep eutectic solvents can be used with a combination of hydrogen bond donors and hydrogen bond acceptors that have been used industrially (in combination with organic solvents), making them inexpensive and easy to commercialize.

[0030] In the present invention, the deep eutectic solvent does not contain inorganic acids. By using such a deep eutectic solvent that does not contain inorganic acids, an environmentally friendly metal recovery device can be provided. Examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and aqua regia.

[0031] From the viewpoint of creating an environmentally friendly metal recovery device, it is preferable that the deep eutectic solvent does not contain any organic solvents that have a boiling point of 150° C. or less. The organic solvents that have a boiling point of 150° C. or less contained in the deep eutectic solvent are preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.1% by mass or less.

[0032] (Leaching process) The leaching temperature in the leaching section is preferably 40°C or higher, more preferably 50°C or higher from the viewpoint of increasing the leaching rate, and particularly preferably 60°C or higher. The temperature of the leaching step in the leaching section is preferably 100°C or lower from the viewpoint of energy efficiency, more preferably 80°C or lower, and particularly preferably 70°C or lower.

[0033] <Recovery Department> In the recovery section, the metal components are separated and recovered from the deep eutectic solvent. In the recovery section, it is preferable to bring the deep eutectic solvent into contact with a hydrophilic solvent and separate and recover the metal components in the hydrophilic solvent. Furthermore, it is preferable that the recovery section has a high recovery efficiency. It is particularly preferable that the recovery rate of the metal components is 80% or more, more particularly preferably 90% or more, and even more particularly preferably 95% or more.

[0034] (hydrophilic solvent) The hydrophilic solvent used in the recovery section is not particularly limited, and any known hydrophilic solvent can be used, such as water or alcohols.

[0035] (chelating agents, precipitants) In the present invention, it is preferable to add a chelating agent or a precipitating agent for precipitating a poorly soluble salt to the hydrophilic solvent, and precipitate the metal component as a salt in the hydrophilic solvent, which is then separated and recovered. Adding a chelating agent to the hydrophilic solvent is preferable from the viewpoint of increasing the reusability of the deep eutectic solvent. The chelating agent is not particularly limited, and known chelating agents can be used. Examples of chelating agents include oxalic acid and dimethylglyoxime, and it is more preferable to use oxalic acid. The precipitating agent for precipitating a poorly soluble salt is not particularly limited, and known precipitating agents such as acids, alkalis, and salts can be used. It is more preferable to use sodium hydroxide, sodium carbonate, or sodium phosphate as the precipitating agent. The concentration of the chelating agent or precipitating agent is preferably 0.1 mol / L or more, more preferably 0.3 mol / L or more, and particularly preferably 0.5 mol / L or more.

[0036] (Recovery process) The metal recovery device is required to be capable of separating and recovering metal components, i.e., capable of separating and recovering at least one type of metal component. For example, when a metal element-containing composition contains three or more types of metal components, it is sufficient to be capable of separating and recovering one type of metal component, preferably capable of separating and recovering two types of metal components, and more preferably capable of separating and recovering three types of metal components. Alternatively, one type of metal component may be separated as an ion in the aqueous phase, and a mixed salt of two or more types of metal components may be separated and recovered as a precipitate. The mixed salt of two or more types of metal components may be further separated and recovered one by one by a known method. After recovering the precipitate initially formed, it is preferable to further precipitate and recover the metal component separated as ions in the aqueous phase as a metal salt by a known method. For example, if the metal component separated as ions in the aqueous phase forms a carbonate with low solubility, carbon dioxide gas can be blown into the aqueous phase to precipitate and recover the metal component separated as ions in the aqueous phase as a carbonate.

[0037] <Reused part> The metal recovery device of the present invention preferably includes a recycling section that returns the deep eutectic solvent from which the metal components have been separated in the recovery section to the leaching section for reuse.

[0038] (cleaning solution) In the present invention, it is preferable that the recycling unit washes the deep eutectic solvent with a cleaning liquid capable of removing the chelating agent, from the viewpoint of regenerating the deep eutectic solvent and achieving a high leaching rate, a high recovery rate, and a high reusability. The cleaning liquid is not particularly limited, and any known cleaning liquid can be used. Examples of cleaning liquids include ammonia water and pure water. The concentration of the ammonia water is not particularly limited, but for example, 0.5 to 2 mol dm -3 It can be said that:

[0039] When the cycle of the leaching section, recovery section, and reuse section is repeated three times using only the deep eutectic solvent returned from the reuse section in the leaching section, the leaching rate of the metal components, as expressed by the following formula 1, is preferably 80% or more, and the recovery rate of the metal components, as expressed by the following formula 2, is preferably 95% or more; more preferably, the leaching rate is 90% or more, and the recovery rate is 97% or more; and particularly preferably, the leaching rate is 99% or more, and the recovery rate is 99% or more. Formula 1

number

number

[0040] When the leaching section uses the deep eutectic solvent returned by the recycling section, additives such as reducing agents and oxidizing agents different from those in the previous cycle may be added in the recycling section or the leaching section.

[0041] <Cleaning section> The metal recovery device may have other functions or devices, for example, a washing section may be provided between the leaching section and the recovery section, as shown in the schematic diagram of another example of the metal recovery device of the present invention shown in Figure 14. The washing section removes impurities and unnecessary metal components contained in the hydrophobic deep eutectic solvent obtained in the leaching section, and does not perform an extraction process, as the metal components to be recovered are not moved from the hydrophobic deep eutectic solvent phase. [Example]

[0042] The present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0043] [Examples 1 to 8] <Preparation of hydrophobic deep eutectic solvents> Metal recovery was carried out using the metal recovery device shown in FIG. First, solid particulate hydrogen bond donors (HBDs) and hydrogen bond acceptors (HBAs) were weighed at 25°C to achieve the desired molar ratio. The mixture was then thoroughly shaken and then completely dissolved by ultrasonic irradiation in a warm bath to prepare a liquid hydrophobic deep eutectic solvent (DES). The chemical structures of the compounds used are shown below. Hydrophobic deep eutectic solvents were prepared with compositions of HBTA / TOPO (2:1) and decA / TOPO (1:1) (the molar ratio of HBD:HBA is in parentheses). [ka]

[0044] LiCoO2 (LCO), which is a solid at 25°C, was used as the metal-element-containing composition. In the leaching of LiCoO2, a typical anode active material for lithium-ion batteries (LiBs), the reduction of Co(III) to Co(II) is effective in improving leaching efficiency. To efficiently leach LCO into a hydrophobic deep eutectic solvent, we used (a) L-ascorbic acid (ascA), (b) citric acid (citricA), or (c) malic acid (malicA) as reducing agents. The molecular structures of the reducing agents used are shown below. [ka]

[0045] In Example 1, HBTA / TOPO (2:1) without the addition of a reducing agent was used as the hydrophobic deep eutectic solvent. In Examples 2 to 4, HBTA / TOPO (2:1) was used as a reducing agent with 0.1 mol dm -3 AscA, citricA, or malicA was dissolved to a predetermined concentration, and a predetermined amount of pure water was added. The solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution, which was used as a hydrophobic deep eutectic solvent. In Example 5, decA / TOPO (1:1) without the addition of a reducing agent was used as the hydrophobic deep eutectic solvent. In Examples 6 to 8, decA / TOPO (1:1) was used as a reducing agent, with 0.1 mol dm -3 AscA, citricA, or malicA was dissolved to a predetermined concentration, and a predetermined amount of pure water was added. The solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution, which was used as a hydrophobic deep eutectic solvent. The water content of the hydrophobic deep eutectic solvent used in each example was adjusted to 2.5%.

[0046] <Leaching> LiCoO2 as a metal element-containing composition was added to the hydrophobic deep eutectic solvent used in each example introduced into the leaching section of the metal recovery device so that the pulp concentration was 10 g / L, and the mixture was stirred at 60°C and 400 rpm to start the leaching reaction. Leaching was then carried out for 24 hours.

[0047] <Recovery of Li and Co from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. The hydrophobic deep eutectic solvent in which LiCoO2 had been leached was contacted with a predetermined concentration of oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 3 hours. The reaction solution was completely separated into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate by centrifugation. The metal concentrations in the aqueous and deep eutectic solvent phases were measured using ICP-OES, and the abundance ratios of each metal in the aqueous, deep eutectic solvent, and precipitate were calculated using mass balance. As a result, it was found that the metal components could be separated and recovered one by one.

[0048] [evaluation] <Leaching efficiency at the leaching section> The leaching behavior of LCO was investigated using the hydrophobic deep eutectic solvents prepared in Examples 1 to 8 as leaching media. The leaching rate %L was calculated using the following formula:

number

[0049] FIG. 4 shows that in Examples 1 to 8, the metal components contained in the metal element-containing compositions were able to be directly leached into the hydrophobic deep eutectic solvent. Regardless of the type of reducing agent, the HBTA / TOPO (2:1) mixtures of Examples 1 to 4 showed higher leaching efficiency than the decA / TOPO (1:1) mixtures of Examples 5 to 8. The higher leaching efficiency of HBTA / TOPO (2:1) is thought to be due to its higher coordination ability than decA / TOPO (1:1). In Example 2, by adding ascA as a reducing agent to HBTA / TOPO (2:1), a high leaching efficiency of over 90% was achieved for both Li and Co. On the other hand, when comparing the systems of Examples 2 and 6, in which ascA was used as the reducing agent, the systems of Examples 3, 4, 7 and 8, in which citricA or malicA was used as the reducing agent, and the systems of Examples 1 and 5, in which no reducing agent was added, the systems of Examples 3, 4, 7 and 8, in which citricA or malicA was used as the reducing agent, showed the lowest leaching efficiency.

[0050] [Examples 11 to 14] <Preparation of hydrophobic deep eutectic solvents> The effect of ascA concentration on LCO leaching into HBTA / TOPO (2:1) was investigated. In Examples 11 to 14, HBTA / TOPO (2:1) was used as a reducing agent, with 0.05 mol dm -3 , 0.10 mol dm -3 , 0.15 mol dm -3 , 0.20 mol dm -3 A predetermined amount of pure water was added and stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution, which was used as a hydrophobic deep eutectic solvent. The water content of the hydrophobic deep eutectic solvent used in each example was adjusted to 2.5%.

[0051] <Leaching> LiCoO2 as a metal element-containing composition was added to the hydrophobic deep eutectic solvent used in each example introduced into the leaching section of the metal recovery device so that the pulp concentration was 10 g / L, and the mixture was stirred at 60°C and 400 rpm to initiate the leaching reaction, and leaching was carried out for 3 hours.

[0052] <Recovery of Li and Co from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. The hydrophobic deep eutectic solvent in which LiCoO2 had been leached was contacted with a predetermined concentration of aqueous oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 3 hours. The reaction solution was completely separated into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate by centrifugation. The metal concentrations in the aqueous and deep eutectic solvent phases were measured using ICP-OES, and the abundance ratios of each metal in the aqueous, deep eutectic solvent, and precipitate were calculated using mass balance. As a result, it was found that the metal components could be separated and recovered one by one.

[0053] [evaluation] <Leaching efficiency at the leaching section> The leaching rates % L in Examples 11 to 14 were determined in the same manner as in Examples 1 to 8, and the leaching efficiency in the leaching area was determined. The results obtained are shown in FIG. FIG. 5 shows that in Examples 11 to 14, the metal components contained in the metal element-containing compositions were able to be directly leached into the hydrophobic deep eutectic solvent. From Examples 11 to 13, the ascA concentration in HBTA / TOPO (2:1) was 0.05 to 0.15 mol dm -3 In the range of [ascA] = 0.15 mol dm, the leaching efficiency increased with increasing ascA concentration. -3 The leaching efficiency of LiCoO2 was maximized when the pulp density of LiCoO2 was 10 g / L (10 g dm -3 ) conditions, it is about 0.1 mol dm -3 It was suggested that the reduction of Co(III) requires more than one equivalent of reducing agent. On the other hand, as shown in Example 14, ascA was detected at a higher concentration of 0.20 mol dm -3 The leaching efficiency was lower than in Examples 12 and 13. This is thought to be due to the fact that excess ascA adhered to the surface of the LiCoO2 powder during the reaction, inhibiting leaching.

[0054] [Examples 21 to 24] <Preparation of hydrophobic deep eutectic solvents> The effect of water content on LCO leaching in a hydrophobic deep eutectic solvent containing HBTA / TOPO (2:1) and reducing agent AscA was investigated. In Example 21, HBTA / TOPO (2:1) was added with 0.10 mol dm -3 AscA was dissolved in the solution so that the water content was 0%, and the solution was stirred at 400 rpm for 1 hour at a controlled temperature of 60°C without adding pure water to obtain a homogeneous solution. This solution had a water content of 0%, and was used as a hydrophobic deep eutectic solvent. In Examples 22 to 24, HBTA / TOPO (2:1) was added with 0.10 mol dm -3 AscA was dissolved in the solution so that the water content was 0.5%, 1.25%, and 2.5%.

[0055] <Leaching> LiCoO2 as a metal element-containing composition was added to the hydrophobic deep eutectic solvent used in each example introduced into the leaching section of the metal recovery device so that the pulp concentration was 10 g / L, and the mixture was stirred at 60°C and 400 rpm to initiate the leaching reaction, and leaching was carried out for 3 hours.

[0056] <Recovery of Li and Co from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. The hydrophobic deep eutectic solvent in which LiCoO2 had been leached was contacted with a predetermined concentration of aqueous oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 3 hours. The reaction solution was completely separated into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate by centrifugation. The metal concentrations in the aqueous and deep eutectic solvent phases were measured using ICP-OES, and the abundance ratios of each metal in the aqueous, deep eutectic solvent, and precipitate were calculated using mass balance. As a result, it was found that the metal components could be separated and recovered one by one.

[0057] [evaluation] <Leaching efficiency at the leaching section> The leaching rates % L in Examples 21 to 24 were determined in the same manner as in Examples 1 to 8, and the leaching efficiency in the leaching area was determined. The results obtained are shown in FIG. FIG. 6 shows that in Examples 21 to 24, the metal components contained in the metal element-containing compositions were able to be directly leached into the hydrophobic deep eutectic solvent. Example 21 revealed that despite the addition of ascA as a reducing agent, both Li and Co showed extremely low leaching efficiency when water was not added. As shown in Examples 22 to 24, the leaching efficiency of Li and Co dramatically improved with increasing water content. This suggests that the presence of water molecules is involved in the reduction of Co(III) to Co(II) by ascA. The oxidation product of ascA, dehydroascorbic acid (DHA), is chemically unstable and undergoes hydrolysis and further oxidation reactions to produce end products such as L-threonic acid and oxalic acid. The added water is likely consumed in the hydrolysis reaction to produce the stable ascA oxidation product in the hydrophobic deep eutectic solvent.

[0058] [Examples 31 to 33] <Preparation of hydrophobic deep eutectic solvents> The effect of the type of hydrophilic solvent used in the recovery section was investigated. In Examples 31 to 33, HBTA / TOPO (2:1) was added with 0.10 mol dm -3 AscA was dissolved in the solution so that the above-mentioned solution was obtained. A predetermined amount of pure water was added and the solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution. The solution with a water content of 2.5% was used as a hydrophobic deep eutectic solvent.

[0059] <Leaching> LiCoO2 as a metal element-containing composition was added to the hydrophobic deep eutectic solvent used in each example introduced into the leaching section of the metal recovery device so that the pulp concentration was 10 g / L, and the mixture was stirred at 60°C and 400 rpm to initiate the leaching reaction, and leaching was carried out for 3 hours.

[0060] <Recovery of Li and Co from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. The hydrophobic deep eutectic solvent containing LiCoO2 was contacted with a predetermined concentration of oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 3 hours. Centrifugation of the reaction mixture completely separated the deep eutectic solvent phase (DES phase), aqueous phase, and precipitate. Oxalic acid reacted with Co(II) to produce a pink precipitate of sparingly soluble Co(C2O4)·2H2O. Furthermore, HBTA / TOPO (2:1) showed pH-dependent extraction curves for Li and Co, indicating that both metals were recovered in the aqueous phase, which was acidic with oxalic acid, i.e., back-extracted. In Examples 31 to 33, the concentrations of the oxalic acid aqueous solution were 1.00 M, 0.50 M, and 0.25 M (mol dm -3 ) was decided. The metal concentrations in the aqueous and deep eutectic solvent phases were measured by ICP-OES, and the abundance ratios of each metal in the aqueous, deep eutectic solvent (DES), and precipitate were calculated from mass balance. The results are shown in Figure 7. From Figure 7, it was found that in Examples 31 to 33, the metal components were separated and recovered one by one. Specifically, Li was quantitatively recovered in the aqueous phase at all oxalic acid concentrations. In particular, Co was quantitatively recovered at an oxalic acid concentration of 0.5 mol dm in Examples 32 and 33. -3 As a result, 99% of the metal components were recovered as oxalates. In other words, in Examples 32 and 33, the recovery rate and purity of each metal component were both 99% or higher. This suggests that the use of an oxalic acid solution can quantitatively remove both Li and Co from the deep eutectic solvent, allowing the deep eutectic solvent to be completely regenerated.

[0061] [Example 41] <Preparation of hydrophobic deep eutectic solvents> The reusability of the deep eutectic solvent was investigated by repeatedly leaching and recovering (stripping) LCO with HBTA / TOPO (2:1). In Example 41, HBTA / TOPO (2:1) was added with 10 mol dm -3AscA was dissolved in the solution so that the above-mentioned solution was obtained. A predetermined amount of pure water was added and the solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution. The resulting solution had a water content of 2.5% and was used as a hydrophobic deep eutectic solvent.

[0062] <Leaching> LiCoO2 as a metal element-containing composition was added to a hydrophobic deep eutectic solvent introduced into the leaching section of the metal recovery device so that the pulp concentration was 10 g / L, and the mixture was stirred at 60°C and 400 rpm to initiate the leaching reaction. Leaching was then carried out for 3 hours.

[0063] <Recovery of Li and Co from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. LiCoO2 was leached into a hydrophobic deep eutectic solvent and 0.50 mol dm -3 The mixture was contacted with an aqueous oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 1 hour. The reaction mixture was centrifuged to completely separate it into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate. The metal concentrations in the aqueous and deep eutectic solvent phases were measured by ICP-OES, and the abundance ratios of each metal in the aqueous, deep eutectic solvent, and precipitate were calculated by mass balance. As a result, it was found that Co and Li elements were completely recovered from the deep eutectic solvent (DES) phase.

[0064] <Reuse of deep eutectic solvent from which metal components have been separated> The deep eutectic solvent from which the metal components have been separated is transferred to the recycling section and washed with 1 mol dm -3 The plate was washed with 100 ml of ammonia water and purified water (MilliQ) for 30 minutes each. The washed deep eutectic solvent was then transferred from the recycling section to the leaching section and used for the next cycle of leaching. The above leaching, recovery and reuse cycle was repeated three times in total.

[0065] [evaluation] <Leaching efficiency and recovery efficiency using recycled deep eutectic solvent> The Co and Li concentrations in the deep eutectic solvent in each cycle were measured by ICP-OES, and the leaching rate %L and recovery rate %S were investigated. In the same manner as in Example 1, the leaching rates %L of Co and Li in each cycle of Example 41 were determined, and the leaching efficiency at the leaching zone was calculated. The recovery rates %S of Co and Li in each cycle indicate the removal rates of each metal component from the deep eutectic solvent. The recovery rates %S were calculated using the following equation 2.

number

[0066] The results obtained are shown in FIG. Figure 8 shows that in the first (1st), second (2nd), and third (3rd) cycles, each metal component was separated and recovered. Specifically, the leaching efficiency of Li and Co decreased slightly with each cycle. The recovery (back extraction) of Li and Co using an oxalic acid solution was nearly 100%. These results demonstrate that the deep eutectic solvent can be reused as a leaching solvent for LCO. It was anticipated that a small amount of oxalic acid would be dissolved in the DES that had come into contact with the oxalic acid solution, which would inhibit the leaching of LCO. However, it was found that by performing a cleaning process in the reuse section, the leaching and recovery efficiencies in the second and third cycles could be sufficiently improved, making it easier to reuse the deep eutectic solvent.

[0067] [Example 42] In the preparation and leaching of the hydrophobic deep eutectic solvent in Example 41, the solid particulate hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) were not weighed and then mixed, but the solid particulate hydrogen bond donor and hydrogen bond acceptor were sprinkled on the metal element-containing composition LiCoO2 in the leaching section of the metal recovery device to directly contact them. Metal recovery was carried out in the same manner as in Example 41. As a result, it was found that the evaluation results were equivalent to those of Example 41.

[0068] [Examples 51 and 52] <Preparation of hydrophobic deep eutectic solvents> The leaching and recovery of various anodic reagents with HBTA / TOPO (2:1) was investigated. In Examples 51 and 52, HBTA / TOPO (2:1) was used as a reducing agent with 10 mol dm -3 AscA was dissolved in the solution so that the above-mentioned solution was obtained. A predetermined amount of pure water was added and the solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution. The resulting solution had a water content of 2.5% and was used as a hydrophobic deep eutectic solvent.

[0069] <Leaching> In Example 51, a commercially available LiNi as a metal element-containing composition was used in a hydrophobic deep eutectic solvent introduced into the leaching section of a metal recovery device. 1 / 3 Mn 1 / 3 Co 1 / 3 O2 (NMC111) was added to the pulp to a concentration of 10 g / L, and the mixture was stirred at 60 °C and 400 rpm to initiate the leaching reaction. The leaching reaction was carried out for 3 hours. NMC111 is a model compound for next-generation lithium-ion battery anode materials and is a solid at 25 °C. In Example 52, leaching was carried out in the same manner as in Example 51, except that spent lithium ion battery anode material (spent cathode) was used as the metal element-containing composition. The spent lithium ion battery anode material (spent cathode) is an automotive lithium ion battery anode material, and is a mixture of anode material powders recovered from various sources, and is solid at 25°C.

[0070] <Recovery of metals from deep eutectic solvent after leaching> As a hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid was prepared by adding oxalic acid as a chelating agent to pure water. The anode material was leached with a hydrophobic deep eutectic solvent and 0.50 mol dm -3 The mixture was contacted with an aqueous oxalic acid solution at a volume ratio of 1:1 and vigorously stirred with a vortex mixer at room temperature for 1 hour. The reaction mixture was centrifuged to completely separate it into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate. The metal concentrations in the aqueous phase and deep eutectic solvent phase were measured by ICP-OES, and the abundance ratio of each metal in the aqueous phase, deep eutectic solvent phase, and precipitate was calculated by mass balance.

[0071] [evaluation] <Leaching efficiency and recovery efficiency> The leaching rate %L and recovery rate %S were calculated using the following formula.

number

[0072] <Comparison of anode material residue after leaching> As Comparative Example 53, the same anode material (Spent cathode) as that used in Example 52 was subjected to leaching of soluble metals using 5M HCl and 5 mass % H2O2. The differences between Comparative Example 53 and the anode material (residue) after leaching with a deep eutectic solvent of Example 52 were compared in terms of morphology and elemental analysis. Electron micrographs of the anode material before leaching, the anode material after leaching of Example 52, and the anode material after leaching of Comparative Example 53, taken with a scanning electron microscope equipped with an X-ray spectrometer (SEM-EDS), are shown in Figure 10. In Figure 10, "High mag." indicates a photograph taken in high-mag mode, and "Low mag." indicates a photograph taken in low-mag mode. The anode material before leaching, the anode material after leaching of Example 52, and the anode material after leaching of Comparative Example 53 were subjected to elemental analysis using an energy dispersive X-ray spectrometer (EDS). The EDS charts are shown in FIGS. 11 to 13, respectively. 11 to 13 show that the anode materials used in Example 52 and Comparative Example 53 contain Al, Si, Ti, and other elements in addition to the oxides of Co and Mn, which are active materials. The EDS results show that Al, Si, and Ti remain in the residue after leaching with a deep eutectic solvent in Example 52. On the other hand, after leaching with HCl in Comparative Example 53, the peaks for Al and Ti are smaller, suggesting that these metals are leached into the acid solution simultaneously with rare metals (Co and Mn). Therefore, it has been demonstrated that the metal recovery method of the present invention, metal leaching and recovery using a hydrophobic deep eutectic solvent, is more efficient and selective than conventional methods and has high industrial applicability.

[0073] [Example 61] Using the metal recovery device shown in Figure 14, we investigated metal recovery from ores (limonite and saprolite). HBTA / TOPO (2:1) with 0.1 mol dm -3 AscA was dissolved in the solution so that the above-mentioned solution was obtained. A predetermined amount of pure water was added and the solution was stirred at 60°C and 400 rpm for 1 hour to obtain a homogeneous solution. The resulting solution had a water content of 2.5% and was used as a hydrophobic deep eutectic solvent.

[0074] <Leaching> The metal-containing composition was added to a hydrophobic deep eutectic solvent introduced into the leaching section of the metal recovery device so that it would form a solid ore (limonite / saprolite) at 25°C. The leaching reaction was initiated by stirring at 60°C and 400 rpm, and leaching was carried out for 3 hours. It was found that Fe, Ni, and Co could be selectively leached from the ore.

[0075] <Cleaning> The hydrophobic deep eutectic solvent after the leaching process was introduced into the washing section of the metal recovery equipment, and a suitable metal capture agent (0.1–5 mol dm -3 A hydrophilic solvent containing sodium hydroxide and / or sodium sulfite was added to precipitate the iron impurity in the aqueous phase.

[0076] <Recovery of metals from deep eutectic solvent after leaching> As the hydrophilic solvent to be used in the recovery section, an aqueous solution of oxalic acid, which was prepared by adding oxalic acid as a chelating agent to pure water, and sulfuric acid were prepared. The anode material was contacted with the hydrophobic deep eutectic solvent and aqueous oxalic acid and / or sulfuric acid, and the mixture was vigorously stirred at room temperature. The reaction solution was centrifuged to completely separate it into a deep eutectic solvent phase (DES phase), an aqueous phase, and a precipitate. From the aqueous phase, nickel sulfate, nickel oxalate, cobalt sulfate and / or cobalt oxalate were recovered, followed by the production of nickel oxide and cobalt oxide.

[0077] <Reuse of deep eutectic solvent from which metal components have been separated> The deep eutectic solvent from which the metal components have been separated is transferred to the recycling section and washed with 1 mol dm -3 The mixture was washed with 100 ml of aqueous ammonia and 100 ml of pure water (MilliQ), respectively. The washed deep eutectic solvent was then transferred from the recycling section to the leaching section and used for the next cycle of leaching. The above leaching, recovery and reuse cycle was repeated three times in total. Example 61 demonstrated that metal salts could be recovered in each cycle, and that the deep eutectic solvent was useful as a leaching solvent for ores (limonite and saprolite) and could be reused.

Claims

1. a leaching unit that directly leaches at least one metal component contained in the metal element-containing composition into a hydrophobic deep eutectic solvent having a solubility in water at 25°C of 1 g / 100 mL or less; a recovery unit that separates and recovers the metal component from the deep eutectic solvent, the metal element-containing composition is solid at 25°C and does not contain an inorganic acid; the metal component is a metal, a metal compound, or a metal ion; the deep eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors; the deep eutectic solvent is free of inorganic acids; The recovery unit brings the deep eutectic solvent into contact with a hydrophilic solvent, and separates and recovers the metal component in the hydrophilic solvent. Metal recovery equipment.

2. The metal recovery apparatus according to claim 1 , wherein the deep eutectic solvent does not contain an organic solvent having a boiling point of 150° C. or less by itself.

3. 3. The metal recovery device according to claim 1, wherein an extraction step of transferring the metal components from the deep eutectic solvent to another organic solvent is not performed between the leaching section and the recovery section.

4. The metal recovery apparatus according to any one of claims 1 to 3, wherein the deep eutectic solvent is liquid at 25°C.

5. The metal element-containing composition contains two or more types of the metal components, The deep eutectic solvent selectively leaches a specific type of metal component among the two or more types of metal components at a higher concentration than other types of metal components. A metal recovery device according to any one of claims 1 to 4.

6. At 25°C, the hydrogen bond donor and the hydrogen bond acceptor are in the form of solid particles before mixing; The deep eutectic solvent is prepared by a process including directly contacting the hydrogen bond donor and the hydrogen bond acceptor, which are solid particles, with the metal element-containing composition, and contacting the metal component with the deep eutectic solvent. The metal recovery device according to any one of claims 1 to 5.

7. The hydrogen bond donor is benzoyltrifluoroacetone or decanoic acid, 7. The metal recovery apparatus according to claim 1, wherein the hydrogen bond acceptor is tri-n-octylphosphine oxide.

8. A metal recovery device described in any one of claims 1 to 7, wherein the concentration of the hydrogen bond donor is controlled to be 1.2 to 5 times the concentration of the hydrogen bond acceptor.

9. The metal element-containing composition contains a metal oxide, The metal recovery apparatus according to any one of claims 1 to 8, further comprising adding a reducing agent to the deep eutectic solvent.

10. 10. The metal recovery apparatus according to claim 9, wherein the reducing agent is L-ascorbic acid, citric acid, or malic acid.

11. The metal recovery apparatus according to claim 9 or 10, wherein the concentration of the reducing agent is controlled to 0.03 to 0.30 mol / L with respect to the deep eutectic solvent.

12. The metal element-containing composition is LiCoO 2 , or LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 The metal recovery device according to any one of claims 9 to 11, comprising:

13. the metal element-containing composition contains a platinum group metal or a platinum group metal compound; The metal recovery apparatus according to any one of claims 1 to 8, further comprising adding an oxidizing agent to the deep eutectic solvent.

14. The metal recovery apparatus according to any one of claims 1 to 13, wherein the water content of the deep eutectic solvent is controlled to 0.3 to 2.8 mass%.

15. The metal recovery device according to any one of claims 1 to 14, wherein a chelating agent is added to the hydrophilic solvent, and the metal components are precipitated as salts in the hydrophilic solvent, and then separated and recovered.

16. The metal recovery apparatus according to any one of claims 1 to 15, comprising a recycling section that returns the deep eutectic solvent from which the metal components have been separated in the recovery section to the leaching section.

17. The metal recovery apparatus according to claim 16, wherein the recycling unit washes the deep eutectic solvent with a cleaning liquid capable of removing a chelating agent.

18. A metal recovery device as described in claim 16 or 17, wherein when the cycle of the leaching section, the recovery section and the recycling section is repeated three times using only the deep eutectic solvent returned by the recycling section in the leaching section, the leaching rate of the metal components represented by the following formula 1 is 80% or more, and the recovery rate of the metal components represented by the following formula 2 is 95% or more. Formula 1 [Equation 1] In Equation 1, % L is the leaching rate, C M,DES is the concentration of the metal component in the deep eutectic solvent [mg dm −3 ], V DES is the volume of the deep eutectic solvent [dm 3 ], m init represents the mass of the metal element-containing composition, and m represents the molecular weight of the metal element-containing composition. Formula 2 [Equation 2] In Equation 2, %S is the recovery rate, C M,S,DES is the concentration of metal components in the deep eutectic solvent in the recovery process [mg dm −3 ], V S,DES is the volume of the deep eutectic solvent in the recovery process [dm 3 ], C M,L,DES is the concentration of the metal component in the deep eutectic solvent during the leaching process [mg dm −3 ], V L,DES represents the volume [dm 3 ] of the deep eutectic solvent in the leaching process.

19. a leaching step of directly leaching at least one metal component contained in the metal element-containing composition into a hydrophobic deep eutectic solvent having a solubility in water at 25°C of 1 g / 100 mL or less; and a recovery step of separating and recovering the metal component from the deep eutectic solvent, the metal element-containing composition is solid at 25°C and does not contain an inorganic acid; the metal component is a metal, a metal compound, or a metal ion; the deep eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors; the deep eutectic solvent is free of inorganic acids; In the recovery step, the deep eutectic solvent is brought into contact with a hydrophilic solvent, and the metal component is separated and recovered in the hydrophilic solvent. How to recover metals.

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