Metal extractant composition and method for isolating and recovering metal ions

Abstract

Provided are: a metal extractant composition for extracting metal ions present in an aqueous phase into an oil phase, the metal extractant composition containing an acidic extractant represented by specific formula and a compound having at least one hydrocarbon group and at least one specific functional group, the total number of carbon atoms of the hydrocarbon group being 14 or more; and a method for isolating and recovering metal ions, comprising mixing an aqueous phase containing a plurality of types of metal ions and an oil phase containing the acidic extractant in the presence of the compound.

Description

Metal extractant composition and method for separating and recovering metal ions

[0001] The present invention relates to a metal extractant composition that extracts metal ions present in an aqueous phase into an oil phase, and a method for separating and recovering metal ions present in an aqueous phase.

[0002] Valuable metals, such as precious metals and rare earth metals, are essential elements for precision instruments, and ensuring a stable supply of high-purity valuable metals presents a major challenge. These valuable metals are typically mined as a mixture of multiple metals, making it necessary to isolate and refine (highly purify) the target valuable metal from the mined mixture. Furthermore, because the amount of valuable metals that can be extracted from mines is limited, technologies for recovering valuable metals from industrial waste without relying on mining are also gaining importance. In particular, lithium-ion batteries (LiBs) are widely used in home appliances, and with the recent rapid spread of electric vehicles, the amount of discarded LiBs is increasing year by year. LiBs use positive electrode active materials containing metal elements such as cobalt and nickel, and demand for cobalt and nickel is expected to increase significantly. To meet the increasing demand for valuable metals associated with this trend, it is necessary not only to increase mining volume but also to establish metal recycling technologies for discarded LiBs (waste LiBs).

[0003] Wet extraction (solvent extraction) is used to isolate and purify valuable metals from mined mixtures and to recycle metals from waste materials. In wet extraction, an aqueous solution (aqueous phase) containing metal element ions (simply referred to as "metal ions") is brought into contact with an organic phase containing a metal extractant, mixed, and allowed to stand to separate the two phases. The metal ions (metal complexes) coordinated with the metal extractant are then transferred (extracted) into the organic phase. The organic phase is then removed, and the metal ions are stripped and, if necessary, purified, enabling the isolation and purification of the target metal and recycling as (high-purity) metal.

[0004] As an example of such a wet extraction method, Patent Document 1 describes a method for selectively extracting yttrium by contacting an aqueous solution containing hydroxyethylethylenediaminetriacetic acid, yttrium, and a lanthanoid with an extractant containing tributyl phosphate and an acidic phosphate ester of 2-heptylundecanol in the presence of a diluent such as alcohol. Patent Document 2 describes a method for removing and recovering one or more radionuclides or two or more metals from a feed solution containing radionuclides, using alkylphenylphosphonic acid as an extractant and alcohol, nitrophenyl alkyl ether, trialkyl phosphate, or a mixture thereof as a modifier. Patent Document 3 further describes a method for selectively extracting indium from an indium-containing aqueous solution using 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester and tridecyl alcohol.

[0005] Japanese Patent Application Laid-Open No. 54-054913 U.S. Patent No. 6,696,589 Japanese Patent Application Laid-Open No. 60-006896

[0006] In wet extraction methods, from the viewpoints of productivity, cost, etc., and furthermore, from the viewpoint of realizing industrialization, it is necessary to increase the processing volume per extraction operation. In particular, in order to cope with the increase in the amount of waste LiB as described above, one effective solution is to be able to quickly process a large amount of waste LiB in a single extraction operation, and this is particularly desirable from the viewpoint of efficiently recovering valuable metals from waste LiB. However, Patent Documents 1 to 3 do not consider at all wet extraction methods that enable an increase in processing volume, or metal extractants to be used in such wet extraction methods.

[0007] The present invention aims to provide a metal extractant composition that can rapidly mix an aqueous phase containing metal ions with an oil phase in a wet extraction method and that can also increase the solubility of a metal complex composed of metal ions and an acidic extractant in the oil phase. Another objective of the present invention is to provide a method for separating and recovering metal ions using the metal extractant composition.

[0008] The present inventors have conducted extensive research into wet extraction methods (methods for separating and recovering metal ions) and have come up with the idea that, in order to rapidly process a large amount of waste LiB, it may be effective to increase the mixing rate of the aqueous phase containing the metal ions with the oil phase, rather than the phase separation rate of the resulting mixture after mixing the aqueous phase containing the metal ions with the oil phase, and then increase the solubility of the metal complex in the oil phase (the extraction capacity of the metal ions). Based on this idea, the present inventors have continued to study metal extractants and the like for use in wet extraction methods. As a result, they have found that by using a metal extractant composition combining an acidic extractant (B) represented by the formula (I) described below and a specific compound (C) described below in a wet extraction method, the aqueous phase and the oil phase can be rapidly mixed, the solubility of the metal complex in the oil phase can be increased, and the processing volume can be increased. The present invention was completed through further research based on these findings.

[0009] That is, the above-mentioned problems have been solved by the following means: [1] A metal extractant composition for extracting metal ions (A) present in an aqueous phase into an oil phase, comprising an acidic extractant (B) represented by the following formula (I), and a compound (C) having at least one hydrocarbon group and at least one functional group included in the following functional group group (c), wherein the total number of carbon atoms constituting the at least one hydrocarbon group is 14 or more. In formula (I), R １ and R ２ each represents an aliphatic hydrocarbon group, and R １ and R ２ At least one of X represents an aliphatic hydrocarbon group having 12 or more carbon atoms. １ represents a hydroxy group or a sulfanyl group. １ represents an oxygen atom or a sulfur atom. １ and Z ２ one of which is a single bond and the other is an oxygen atom or a sulfur atom. <Functional Group (c)> Hydroxy group, amino group, sulfanyl group, imino group, ether bond, ester bond, phosphate ester bond, phosphonate ester bond, phosphinate ester bond, amide bond, urethane bond, urea bond [2] R １and R ２ [3] The metal extractant composition according to [1], wherein at least one of R is an aliphatic hydrocarbon group having 16 or more carbon atoms. １ and R ２ and each of the groups is an aliphatic hydrocarbon group having a branched structure.

[0010] [4] The metal extractant composition according to any one of [1] to [3], wherein the compound (C) is represented by the following formula (II): In formula (II), R ３ , R ４ and R ５ each represents a hydrocarbon group, and R ３ ~R ５ At least one of Y represents a hydrocarbon group having 8 or more carbon atoms. ２ represents an oxygen atom or a sulfur atom. ３ , Z ４ and Z ５ each represents a single bond, an oxygen atom, or a sulfur atom; Z ３ ~Z ５ At least one of R is a single bond. ３ , R ４ and R ５ [6] The metal extractant composition according to [4], wherein R ３ , R ４ and R ５ [7] The metal extractant composition according to [4] or [5], wherein at least one of R is a hydrocarbon group having 16 or more carbon atoms. ３ , R ４ and R ５wherein two of the groups are hydrocarbon groups having 16 or more carbon atoms. [8] The metal extractant composition according to any one of [1] to [7], wherein the molar ratio of compound (C) to acidic extractant (B) is 10.0 to 0.0001. [9] The metal extractant composition according to any one of [1] to [8], wherein metal ions (A) extracted into the oil phase are ions of two metal elements belonging to different groups among ions of metal elements belonging to groups 8 to 11 of the periodic table of the elements.

[10] A method for separating and recovering metal ions, comprising mixing an aqueous phase containing multiple metal ions with an oil phase containing the metal extractant composition according to any one of [1] to [9].

[11] A method for separating and recovering metal ions, comprising mixing an aqueous phase containing multiple metal ions with an oil phase containing the acidic extractant (B) according to [1] in the presence of compound (C) according to [1].

[0011] The present invention provides a metal extractant composition that can rapidly mix an aqueous phase containing metal ions with an oil phase in a wet extraction method and can also increase the solubility of a metal complex composed of metal ions and an acidic extractant in the oil phase, as well as a method for separating and recovering metal ions using the metal extractant composition.The above and other features and advantages of the present invention will become more apparent from the following description.

[0012] In the present invention, when describing the content, physical properties, etc. of a component by indicating a numerical range, if the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges represented using "to", the upper and lower limits forming the numerical range are not limited to the specific combinations written before and after "to" as a specific numerical range, but can be any numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that in the present invention, a numerical range represented using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In the present invention, when a compound is referred to (for example, when "compound" is added to the end), it is used to mean not only the compound itself, but also its salts and ions. It also means to include derivatives that have been partially modified, such as by introducing a substituent, to the extent that the effects of the present invention are not impaired. In the present invention, when a substituent, linking group, etc. (hereinafter referred to as a substituent, etc.) is not specified as substituted or unsubstituted, it means that the group may have an appropriate substituent. Therefore, in the present invention, even when simply described as a YYY group, this YYY group includes not only an embodiment having no substituent, but also an embodiment having a further substituent. This also applies to compounds where substituted or unsubstituted is not specified. Preferred substituents include, for example, groups selected from the substituents GZ described below. In the present invention, when there are multiple substituents, etc., designated by a specific symbol, or when multiple substituents, etc., are specified simultaneously or alternatively, this means that the respective substituents, etc., may be the same or different from each other. Furthermore, even if not otherwise specified, when multiple substituents, etc., are adjacent, they may be linked to each other or fused to form a ring.

[0013] In this specification, a "metal element belonging to a different group in the periodic table of elements" is referred to as a "different group metal element," and in particular, a "different group metal element in the same period in the periodic table" may be referred to as a "same-period, different-group metal element." Furthermore, an "ion of a different group metal element" and an "ion of a different group metal element in the same period" may be referred to as a "different group metal ion" and an "same-period, different-group metal ion," respectively. In the present invention, "ppm" indicating a content, etc., is based on mass and represents "mass ppm" unless otherwise specified.

[0014] [Metal Extractant Composition] The metal extractant composition of the present invention is a metal extractant composition for extracting metal ions (A) present in an aqueous phase into an oil phase. The metal extractant composition contains an acidic extractant (B) represented by the following formula (I), and further contains a compound (C) having at least one hydrocarbon group and at least one functional group included in the functional group group (c) described below, wherein the total number of carbon atoms constituting the at least one hydrocarbon group is 14 or more. The components contained in the metal extractant composition of the present invention, such as the acidic extractant (B), the compound (C), and the other components described below, may each be one or more types. The metal extractant composition of the present invention containing the acidic extractant (B) and the compound (C) can be used in a wet extraction method for extracting metal ions (A) present in an aqueous phase into an oil phase, thereby enabling rapid mixing of the aqueous phase containing the metal ions (A) with the oil phase and also increasing the solubility of a metal complex composed of the metal ions (A) and the acidic extractant in the oil phase. As a result, the wet extraction method using the metal extractant composition of the present invention can increase the processing amount, for example, the total content of metal ions in the aqueous phase, the amount of metal ions (A) extracted in the oil phase, and even the amount of waste LiB used.

[0015] The metal extractant composition of the present invention, for example, the acidic extractant (B) in combination with compound (C), exhibits the function of extracting metal ions present in an aqueous phase into an oil phase, and is particularly suitable for use in wet extraction methods. When the metal extractant composition of the present invention is used in wet extraction methods, as described above, the mixing rate between the aqueous phase and the oil phase is high, and the solubility of the metal complex in the oil phase is also increased. As a result, in addition to increasing the throughput, a specific metal ion (A) present in the aqueous phase can be extracted into the oil phase, preferably with a high recovery rate (high extraction rate), and more preferably with high selectivity. In particular, the metal extractant composition of the present invention can extract a specific metal ion (A) from multiple metal ions present in the aqueous phase into the oil phase, preferably with a high recovery rate, and more preferably with high selectivity. In the present invention, the metal ion (A) that can be extracted into the oil phase from multiple metal ions present in the aqueous phase is ideally one specific metal ion, but it may also be two or more metal ions, as described in the metal ion separation and recovery method of the present invention. Examples of the two or more types of metal ions include two or more types of metal ions contained in the aqueous phase described below, and preferably two types of metal ions belonging to groups 8 to 11 (preferably metal ions of different groups).

[0016] In the present invention, even when two or more types of metal ions are extracted, one of the metal ions can be extracted (separated and recovered) into the oil phase, preferably with a high recovery rate and more preferably with high selectivity relative to the other metal ions (including those extracted into the oil phase). For example, while two or more types of metal ions from different groups, specifically two or more types of metal ions belonging to Groups 1 to 14 of the Periodic Table, desirably two or more types of metal ions from different groups, and particularly desirably cobalt ions and nickel ions, which are metal ions from the same period and different groups, are extracted into the oil phase as ions of valuable metal elements, one of the metal ions can be extracted into the oil phase preferably with a high recovery rate and more preferably with high selectivity. Since metal ions from the same group have similar physical and chemical behaviors, it is not easy to separate and recover either one of them with a high recovery rate and / or high selectivity. However, in the present invention, which uses the acidic extractant (B) and the compound (C), it is possible to extract both metal ions from the same group that have similar physical and chemical behaviors, particularly metal ions belonging to Group 9 (particularly cobalt ions) and metal ions belonging to Group 10 (particularly nickel ions), which are required due to the recent rapid spread of lithium-ion batteries, while recovering one of the metal ions preferably with a high recovery rate and more preferably with high selectivity. Therefore, the present invention can greatly contribute to the further spread of electric vehicles and, ultimately, to the creation of a sustainable society.

[0017] In the present invention, being able to extract metal ions with a high recovery rate means that, for the metal ion extracted in the maximum amount (the specific metal ion to be extracted), the amount of the metal ion extracted into the oil phase can be extracted at a ratio of 60% or more to the content of the metal ion in the aqueous phase (before extraction) [(amount of metal ion extracted into the oil phase) / (content of the metal ion in the aqueous phase)]. This ratio (also referred to as recovery rate or extraction rate) is preferably 80% or more, more preferably 90% or more. The upper limit is not particularly limited, and ideally is the total amount (100%) of the metal ion present in the aqueous phase. For example, it is preferably 99% or less, and can also be 95% or less or 90% or less. The specific amount of extraction (the specific mass that can be transferred and extracted from the aqueous phase to the oil phase) depends on the content of metal ions present in the aqueous phase, but for example, under the conditions of Example 1, it can be 32,000 ppm or more, preferably 36,000 ppm or more, and more preferably 39,600 ppm or more.

[0018] In the present invention, "highly selective extraction of metal ions" means that only one specific metal ion can be extracted from multiple metal ions present in the aqueous phase. When two or more metal ions are extracted into the oil phase, "highly selective extraction of metal ions" means that, among the two or more extracted metal ions, the ratio of the specific metal ion (usually one type) to the total amount of other metal ions extracted [(amount of specific metal ion extracted) / (total amount of other metal ions extracted)] can be extracted and separated from other metal ions at a ratio (separation ability, selectivity) of 3.0 or more. The ratio (selectivity) is preferably 3.7 or more, more preferably 3.8 or more, and even more preferably 4.0 or more. The upper limit is not particularly limited, but can be, for example, 20.

[0019] In the present invention, the phrase "capable of rapidly mixing the aqueous phase and the oil phase (high mixing rate)" refers to the short time required for the combined solution to reach the predetermined pH immediately after the pH adjuster necessary to adjust the combined solution to the predetermined pH is added to the combined solution in a single go. This "high mixing rate" is not uniquely determined by the respective contents of the metal ions (A), the acidic extractant (B), or the compound (C), the volumes of the aqueous and oil phases, the mixing conditions, etc., but refers to, for example, meeting the pass criteria under the conditions of the mixing rate test in the Examples described below. This mixing rate is different from the time required for the liquid phase separation of the combined solution in which the aqueous and oil phases have reached the predetermined pH (i.e., until the phase interface can be visually confirmed) (the so-called "phase separation rate"). In the present invention, the phrase "high solubility of a metal complex composed of metal ions (A) and acidic extractant (B) in the oil phase" is synonymous with a high extraction capacity, such as the amount of extraction or extraction rate of metal ions (A). The term "high solubility" is not uniquely determined by the respective contents of the metal ions (A) or the acidic extractant (B) or the compound (C), the liquid volumes of the aqueous phase and the oil phase, the mixing conditions, etc., but means, for example, that at least one of, and preferably both of, the extraction amount and extraction rate under the conditions of the examples described below meet the acceptance criteria, or that the metal ions can be extracted with a high recovery rate, as described above.

[0020] The metal extractant composition of the present invention only needs to contain at least one acidic extractant (B) and at least one compound (C), and may contain other components as described below as appropriate to the extent that the effects of the present invention are not impaired. Furthermore, since the acidic extractant (B) functions as an extractant for metal ions in cooperation with the compound (C), the metal extractant composition of the present invention may contain, although not necessarily, a metal extractant other than the acidic extractant (B) (another metal extractant). In the present invention, when the metal extractant composition of the present invention contains another metal extractant, the content of the other metal extractant is not particularly limited, but it is preferable that the content of the other metal extractant is 10% by mass or less relative to the total of the acidic extractant (B). When the metal extractant composition of the present invention contains a solvent, the form of the acidic extractant (B) and the compound (C) in the solvent is not particularly limited, and they may be in a solid state such as a powder or granule, or may be dissolved in the solvent.

[0021] (Acidic Extractant (B)) The acidic extractant (B) contained in the metal extractant composition of the present invention is a compound having a chemical structure represented by the following formula (I). The acidic extractant (B) represented by the following formula (I) is a compound having a structure represented by the following formula (I) as described below. １ The acidic extractant (B) has a hydroxy group or a sulfanyl group, and exhibits acidity, which improves the synergistic effect with the hydrophobic compound (C) described below, thereby exhibiting the above-mentioned excellent properties. In the present invention, "acidic" means that the extractant does not react with active oxygen, for example, the above-mentioned X １ Specifically, the pKa of the acidic extractant (B) is preferably 0.1 to 8.0. The pKa can be measured by neutralization titration.

[0022] The acidic extractant (B) represented by the following formula (I) is a phosphonic acid monoester compound, and the phosphonic acid monoester (R Ｐ１ -P(=O)(OH)-OR Ｐ２ ) and thiophosphonic acid monoesters in which at least one of the three oxygen atoms of the phosphonic acid is replaced with a sulfur atom. Ｐ１ and R Ｐ２ is R in the following formula (I): １ and R ２ The acidic extractant (B) is preferably a phosphonic acid monoester in terms of stability, the mixing rate of both phases, and the solubility of the metal complex.

[0023]

[0024] In formula (I), R １ and R ２ R represents an aliphatic hydrocarbon group. １ and R ２ The aliphatic hydrocarbon groups that can be taken as R may be the same or different. １ and R ２The aliphatic hydrocarbon group that can be used as R is not particularly limited, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, etc., with alkyl groups being preferred. In the present invention, alkyl groups include aralkyl groups substituted with an aryl group. The same applies to alkenyl groups and alkynyl groups. The chain structure of the aliphatic hydrocarbon group may be any of linear, branched, and cyclic chains, but a branched chain is more preferred in that it can achieve a higher level of both the mixing speed of the two phases and the solubility of the metal complex. The number of branches (number of branched carbon atoms) in an aliphatic hydrocarbon group having a branched structure (branched aliphatic hydrocarbon group) may be 1 or more, and can be 1 to 8. In terms of the mixing speed of the two phases and the solubility of the metal complex, it is preferably 1 to 6, and more preferably 1 to 4. R １ and R ２ The aliphatic hydrocarbon groups that can be used as R are preferably aliphatic hydrocarbon groups having a branched structure, in that they can achieve a higher level of both the mixing rate of the two phases and the solubility of the metal complex. １ and R ２ The aliphatic hydrocarbon groups having a branched structure that can be taken as the above may have the same or different chemical structures (molecular structures), such as chain structures and branch carbon numbers.

[0025] R １ and R ２ The number of carbon atoms constituting the aliphatic hydrocarbon group (hereinafter, "number of carbon atoms" may also be simply referred to as "carbon number") is not particularly limited and can be determined appropriately. The number of carbon atoms in the aliphatic hydrocarbon group can be, for example, 8 or more, and in terms of the mixing speed of the two phases and the solubility of the metal complex, it is preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and particularly preferably 16 or more. On the other hand, the upper limit of the number of carbon atoms is not particularly limited and can be determined appropriately, and can be, for example, 30 or less, preferably 24 or less. The number of carbon atoms in the aliphatic hydrocarbon group refers to the total number of carbon atoms constituting the aliphatic hydrocarbon; if the aliphatic hydrocarbon group has a substituent other than the aliphatic hydrocarbon group (for example, an aromatic hydrocarbon), the number of carbon atoms of this substituent is not included.

[0026] In the present invention, regardless of the number of carbon atoms in each of the above aliphatic hydrocarbon groups, R １ and R ２ At least one of the aliphatic hydrocarbon groups has 12 or more carbon atoms. １ and R ２ When at least one of R is an aliphatic hydrocarbon group having 12 or more carbon atoms, it is possible to achieve both the mixing speed of the two phases and the solubility of the metal complex. １ and R ２ The number of carbon atoms in at least one of the aliphatic hydrocarbon groups is preferably 14 or more, more preferably 16 or more, and the upper limit is not particularly limited and can be, for example, 30 or less, preferably 24 or less.

[0027] In the present invention, R １ and R ２ the number of carbon atoms in one of the aliphatic hydrocarbon groups and R １ and R ２ and the number of carbon atoms of the other aliphatic hydrocarbon group, a first combination in which one aliphatic hydrocarbon group has 1 to 11 carbon atoms and the other aliphatic hydrocarbon group has 12 or more carbon atoms; １ and R ２ and a second combination in which both aliphatic hydrocarbon groups have 12 or more carbon atoms. In the first combination, the number of carbon atoms in one of the aliphatic hydrocarbon groups is preferably 4 to 10, more preferably 6 to 10, and even more preferably 8 to 10, in terms of the mixing speed of the two phases and the solubility of the metal complex. The number of carbon atoms in the other aliphatic hydrocarbon group is the same as the number of carbon atoms in the aliphatic hydrocarbon group having 12 or more carbon atoms. In the second combination, the number of carbon atoms in both aliphatic hydrocarbon groups is the same as the number of carbon atoms in the aliphatic hydrocarbon group having 12 or more carbon atoms, and they may have the same or different carbon numbers. In the second combination, the chemical structures (molecular structures), for example, chain structures and branched carbon numbers, of both aliphatic hydrocarbon groups may be the same or different.

[0028] In formula (I), X １represents a hydroxy group or a sulfanyl group (—SH), and is preferably a hydroxy group. １ The hydroxyl group and sulfanyl group may each form a salt. The cation that forms the salt is not particularly limited, and examples thereof include metal cations, particularly metal cations of Group 1 or Group 2, and organic cations. The organic cation is not particularly limited, and examples thereof include ammonium cations and alkylammonium cations.

[0029] In formula (I), Y １ represents an oxygen atom or a sulfur atom, and is preferably an oxygen atom.

[0030] In formula (I), Z １ and Z ２ represents a single bond on one side and an oxygen atom or a sulfur atom on the other side. １ and Z ２ The other atom is preferably an oxygen atom.

[0031] In formula (I), R １ -Z １ - group and R ２ -Z ２ The combination with the - group is not particularly limited, but Z １ and Z ２ R bonded to one of １ or R ２ The number of carbon atoms in the aliphatic hydrocarbon group that can be taken by Z １ and Z ２ R bonded to the other １ or R ２ It is preferable that the number of carbon atoms of the aliphatic hydrocarbon group is equal to or smaller than that of the aliphatic hydrocarbon group that can be taken by the group.

[0032] In formula (I), R １ , Z １ , R ２ , Z ２ , Y １ and X １ The combination of is not particularly limited and can be determined appropriately. Preferred examples of the combination include combinations of the preferred elements indicated by the respective symbols.

[0033] The acidic extractant (B) may have a substituent, and examples of the substituent that may be had include groups selected from the substituents GZ described below. The molecular weight of the acidic extractant (B) is not particularly limited, but can be, for example, 350 to 2000. In terms of solubility in the oil phase, it is preferably 370 to 1500, and more preferably 400 to 1000. The acidic extractant (B) may be a commercially available product or a synthetic product. The acidic extractant (B) can be synthesized by referring to known synthesis methods, such as the method described in Patent Document 2 or the synthesis method described in the Examples described below.

[0034] Specific examples of the acidic extractant (B) include those shown below in addition to those synthesized in the examples, but the present invention is not limited to these.

[0035] (Compound (C)) The compound (C) contained in the metal extractant composition of the present invention is a compound having at least one hydrocarbon group and at least one functional group included in the functional group group (c) described below, and is a compound in which the total number of carbon atoms constituting all of the hydrocarbon groups is 14 or more. This compound (C) cooperates with the acidic extractant (B) to reinforce and promote the metal ion extraction function of the acidic extractant (B), thereby allowing the acidic extractant (B) to exhibit the above-mentioned excellent extraction properties. The compound (C) is preferably a neutral compound in that it can reinforce or effectively exhibit the excellent extraction properties of the acidic extractant (B). In the present invention, a "neutral compound" means a compound that does not have active oxygen (acidic group) in the chemical structure of one molecule of the compound. Specifically, for example, the pKa of the compound is preferably 12 to 30. Here, the acidic group is a carboxyl group, a phenolic hydroxyl group, a phosphate group (-OP(=O)(OR Ｃ ) ２ ), a phosphonic acid group (-P(=O)(OR Ｃ ) ２ ), sulfonic acid group (—S(═O) ２ OH), sulfinic acid group (-S(=O)OH), etc. Ｃ represents a hydrogen atom or a substituent, and at least one of them is a hydrogen atom. ＣThe substituent that can be used as the compound (C) is not particularly limited, and examples thereof include groups selected from the substituents G and Z described below. Compound (C) has at least one hydrocarbon group, and the total number of carbon atoms constituting all of the hydrocarbon groups is 14 or more. Compound (C) having such a hydrocarbon group exhibits hydrophobicity and can be said to be a hydrophobic additive for the acidic extractant (B).

[0036] Compound (C) is a compound having at least one hydrocarbon group and at least one functional group included in the functional group group (c) described below (sometimes referred to as "functional group (c)" for convenience in the present invention), and can also be referred to as a hydrocarbon compound having at least one functional group (c). Compound (C) may be a compound in which the hydrocarbon group and the functional group (c) are bonded via a linking group, but is preferably a compound in which the hydrocarbon group and the functional group (c) are directly bonded. The linking group is not particularly limited, and examples include groups in which one or more hydrogen atoms have been removed from a group selected from the substituents GZ described below (excluding hydrocarbon groups).

[0037] The hydrocarbon group contained in the compound (C) is not particularly limited, and examples thereof include aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Aliphatic hydrocarbon groups are preferred because they can cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex. The aliphatic hydrocarbon that constitutes the aliphatic hydrocarbon group is not particularly limited, and examples thereof include chain or cyclic saturated aliphatic hydrocarbons (alkanes, cycloalkanes), chain or cyclic unsaturated aliphatic hydrocarbons (alkenes, alkynes), and the like. The aliphatic hydrocarbon group is a monovalent or divalent or higher group obtained by removing the required number of hydrogen atoms (the number of functional groups (c)) from the aliphatic hydrocarbon. Examples of the aliphatic hydrocarbon group include groups composed of the saturated aliphatic hydrocarbons and groups composed of unsaturated aliphatic hydrocarbons. Examples of the monovalent aliphatic hydrocarbon group include alkyl groups, alkenyl groups, alkynyl groups, and the like. As the aliphatic hydrocarbon group, a group consisting of the above-mentioned saturated aliphatic hydrocarbon is preferred, and a group consisting of an alkane is more preferred, in that it can cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex. An example of a monovalent group consisting of an alkane is an alkyl group. The aromatic hydrocarbon group is a monovalent or divalent or higher group obtained by removing the required number of hydrogen atoms (the number of functional groups (c)) from an aromatic hydrocarbon. An example of a monovalent aromatic hydrocarbon group is an aryl group. The aryl group is not particularly limited and is, for example, the same as the aryl group in the substituent GZ described below. In the present invention, the aliphatic hydrocarbon group includes an aliphatic hydrocarbon group having an aromatic hydrocarbon group as a substituent, and the aromatic hydrocarbon group includes an aromatic hydrocarbon group having an aliphatic hydrocarbon group as a substituent.

[0038] The chain structure of the aliphatic hydrocarbon group may be any of linear, branched, and cyclic, but linear or branched chains are preferred, with branched chains being more preferred in that it can cooperate with the acidic extractant (B) to achieve both a higher level of mixing speed between the two phases and a higher level of solubility of the metal complex. The number of branches (number of branched carbon atoms) in the aliphatic hydrocarbon group having a branched structure (branched aliphatic hydrocarbon group) may be 1 or more, and may be 1 to 8, and is preferably 1 to 6, and more preferably 1 to 4, in that it can cooperate with the acidic extractant (B) to achieve both a higher level of mixing speed between the two phases and a higher level of solubility of the metal complex.

[0039] The number of hydrocarbon groups contained in compound (C) is not particularly limited and can be determined appropriately depending on the chemical structure, and can be, for example, 1 to 6, preferably 1 to 3. When compound (C) has two or more hydrocarbon groups, the two or more hydrocarbon groups may have the same or different chemical structures, such as chain structure and number of carbon atoms. In the present invention, the number of hydrocarbon groups contained in compound (C) is a number that includes, when the functional group (c) described below or a substituent that compound (C) may optionally have has a hydrocarbon group (a partial structure formed by hydrocarbon), the number of hydrocarbon groups contained in this functional group (c) or substituent, etc.

[0040] The total number of carbon atoms constituting all hydrocarbon groups in compound (C) is 14 or more. Compound (C) having a total carbon number of 14 or more can cooperate with acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex. The total number of carbon atoms is preferably 15 or more, more preferably 16 or more, even more preferably 18 or more, particularly preferably 24 or more, and most preferably 30 or more, in order to achieve a higher level of both the mixing rate of the two phases and the solubility of the metal complex in cooperation with acidic extractant (B). On the other hand, the upper limit of the total number of carbon atoms is not particularly limited and can be determined appropriately. For example, it can be 60 or less, preferably 54 or less, more preferably 48 or less, and even more preferably 36 or less. In the present invention, the total carbon number is a number that includes, in addition to the number of carbon atoms constituting the hydrocarbon group, when the functional group (c) described below or a substituent or the like that the compound (C) may optionally have has a hydrocarbon group (a partial structure formed by hydrocarbon), the number of carbon atoms constituting the hydrocarbon group (a partial structure formed by hydrocarbon) that the functional group (c) or the substituent or the like has.

[0041] The number of carbon atoms constituting the hydrocarbon group of compound (C) (when compound (C) has two or more hydrocarbon groups, each hydrocarbon group) is appropriately determined taking into account the total carbon number. The number of carbon atoms in each hydrocarbon group can be, for example, 4 or more, and is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and even more preferably 16 or more, in order to cooperate with the acidic extractant (B) to achieve a higher level of both the mixing rate of the two phases and the solubility of the metal complex. On the other hand, the upper limit of the number of carbon atoms in each hydrocarbon group can be, for example, 36 or less, preferably 30 or less, more preferably 24 or less, and even more preferably 20 or less, and is also preferably set to the upper limit of the number of carbon atoms in the medium-chain hydrocarbon group. When compound (C) has two or more hydrocarbon groups, the carbon atoms in each hydrocarbon group may be the same or different. Of the two or more hydrocarbon groups contained in compound (C), at least one hydrocarbon group (sometimes referred to as a "medium-chain hydrocarbon group" for convenience) may have a carbon number of, for example, 8 to 24. In order to achieve both a higher level of mixing speed between the two phases and a higher level of solubility of the metal complex in cooperation with the acidic extractant (B), the carbon number of the medium-chain hydrocarbon group is preferably 8 to 20, and more preferably 8 to 18. In one preferred embodiment, the lower limit of the carbon number of the medium-chain hydrocarbon group is 10 or 12. Meanwhile, the carbon number of at least one other hydrocarbon group (sometimes referred to as a "long-chain hydrocarbon group" for convenience) may have a carbon number of, for example, 12 to 36. In order to achieve both a higher level of mixing speed between the two phases and a higher level of solubility of the metal complex in cooperation with the acidic extractant (B), the carbon number of the long-chain hydrocarbon group is preferably 14 to 30, and more preferably 16 to 24. When compound (C) has three or more hydrocarbon groups, it is preferable that the number of long-chain hydrocarbon groups is large.

[0042] When compound (C) has two or more hydrocarbon groups, the combination of hydrocarbon groups is not particularly limited, and can be a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon. However, in terms of being able to cooperate with the acidic extractant (B) to improve the mixing speed of the two phases and the solubility of the metal complex, a combination of aliphatic hydrocarbon groups is preferred, a combination of saturated aliphatic hydrocarbons is more preferred, and a combination of groups consisting of alkanes is even more preferred. A combination of monovalent groups consisting of alkanes is a combination of alkyl groups. The combination of chain structures of hydrocarbon groups is not particularly limited, but in terms of being able to cooperate with the acidic extractant (B) to improve the mixing speed of the two phases and the solubility of the metal complex, a combination of saturated aliphatic hydrocarbons having a branched structure, for example, a combination of alkyl groups having a branched structure, is preferred.

[0043] In the compound (C), the position at which the functional group (c) is bonded in the hydrocarbon group is not particularly limited, and may be, for example, inside or at the end of the carbon chain constituting the hydrocarbon group.

[0044] The compound (C) has at least one functional group (c) included in the following functional group group (c). The number of functional groups (c) that the compound (C) has is not particularly limited as long as it is one or more, and can be, for example, 1 to 4, preferably 1 to 2, and more preferably 1, in terms of being able to cooperate with the acidic extractant (B) to improve the mixing speed of the two phases and the solubility of the metal complex. <Functional group (c)> Hydroxy group, amino group, sulfanyl group (thiol group), imino group, ether bond, ester bond, phosphate ester bond, phosphonate ester bond, phosphinate ester bond, amide bond, urethane bond, urea bond

[0045] The hydroxy group is represented by —OH and is preferably bonded to a carbon atom to form a hydrocarbon alcohol compound or a phenol compound. Forming an alcohol compound is more preferable in that it can cooperate with the acidic extractant (B) to improve the mixing rate of both phases and the solubility of the metal complex. The amino group is represented by —N(R Ｎ１ ) ２ and forms a hydrocarbon amine compound. Ｎ１ represents a hydrogen atom or a substituent.Ｎ１ The substituents that can be used as the group are not particularly limited, and examples thereof include groups selected from the substituents GZ described below. Preferred are hydrocarbon groups such as alkyl groups (including cycloalkyl groups), alkenyl groups, alkynyl groups, and aryl groups, and heterocyclic groups, with alkyl groups and aryl groups being more preferred. The sulfanyl group (thiol group) is represented by -SH and is preferably bonded to a carbon atom to form a hydrocarbon thiol compound or a thiophenol compound. Forming a hydrocarbon thiol compound is more preferred, as it can cooperate with the acidic extractant (B) to improve the mixing rate of both phases and the solubility of the metal complex. The imino group is represented by -NR Ｎ２ a bond represented by - or -C=NR Ｎ３ and preferably forms a hydrocarbon imino compound. Ｎ２ represents a hydrogen atom, a substituent, or a bond **, and R Ｎ３ represents a hydrogen atom or a substituent. Ｎ２ and R Ｎ３ The substituent that can be taken as is not particularly limited, and examples thereof include groups selected from the substituents G and Z described below. Hydrocarbon groups such as alkyl groups (including cycloalkyl groups), alkenyl groups, alkynyl groups, and aryl groups, heterocyclic groups, and the like are preferred, and alkyl groups or aryl groups are more preferred.

[0046] Ether bond (-O-), ester bond (*-CO-O-**), phosphate ester bond (*-OP(=O)(OR Ｃ ) ２ ), phosphonate bond (*-P(=O)(OR Ｃ ) ２ ), phosphinic acid ester bond (*-P(=O)(OR Ｃ ) R Ｄ ), amide bond (*-CONR ＮＡ１ -**), urethane bond (*-NR ＮＡ１ -CO-O-**), urea bond (-NR ＮＡ１ -CO-NR ＮＡ１-) respectively means the bond shown in parentheses. Each of the above bonds preferably forms an ether compound, ester compound, phosphate ester compound, phosphonate ester compound, phosphinate ester compound, amide compound, urethane compound, or urea compound of a hydrocarbon. However, the phosphate ester bond, phosphonate ester bond, and phosphinate ester bond include bonds in which at least one oxygen atom contained in the above bond is substituted with a sulfur atom, such as a thiophosphate ester bond, a thiophosphonate ester bond, and a thiophosphinate ester bond. In each of the above bonds, * and ** indicate the bonding site.

[0047] R Ｃ and R Ｄ indicates a substituent or a bond **, respectively. However, the two R Ｃ At least one of R in the phosphinic acid ester bond is a bond **, and preferably one is a bond ** and the other is a substituent. Ｃ and R Ｄ At least one of the is a bonded portion **. ＮＡ１ represents a hydrogen atom or a substituent. Ｃ , R Ｄ and R ＮＡ１ The substituent that can be taken as R is not particularly limited, but examples thereof include groups selected from the substituents G and Z described below, and preferred are hydrocarbon groups such as alkyl groups (including cycloalkyl groups), alkenyl groups, alkynyl groups, aralkyl groups, and aryl groups, heterocyclic groups, and the like, with alkyl groups and aryl groups being more preferred. Ｃ , R Ｄ and R ＮＡ１ The hydrocarbon groups that can be represented by R are preferably the same as the hydrocarbon groups contained in the compound (C). ＣThe number of carbon atoms in the hydrocarbon group which may be the same as the number of carbon atoms in the hydrocarbon group contained in compound (C), but in a preferred embodiment it is preferably 1 to 20, more preferably 1 to 12, and even more preferably 1 to 6, and in another preferred embodiment it is the same as the number of carbon atoms in the hydrocarbon group contained in compound (C). The number of carbon atoms in the aryl group is preferably 6 to 26, more preferably 6 to 20, and even more preferably 6 to 12. In addition, Ｃ , two R in the urea bond ＮＡ１ may be the same or different. ＮＡ１ is preferably a hydrogen atom. In each of the above bonds, either of the two bonds * and ** may be bonded to the hydrocarbon group of compound (C), but it is preferable that the bond * is bonded to the hydrocarbon group.

[0048] The imino group (—NR Ｎ２ The bond represented by -) and the terminal group bonded to each of the above bonds are not particularly limited, and examples thereof include a hydrogen atom or a substituent. Examples of the substituent that can be taken as the terminal group include a group selected from the substituents GZ described below. Among them, hydrocarbon groups such as alkyl groups (including cycloalkyl groups), alkenyl groups, alkynyl groups, and aryl groups, and heterocyclic groups are preferred, with alkyl groups or aryl groups being more preferred. The hydrocarbon group that can be taken as the terminal group is preferably the same as the hydrocarbon group contained in compound (C). In the present invention, the number of carbon atoms in the hydrocarbon group that can be taken as the terminal group is determined by the above R Ｃ The number of carbon atoms in the aryl group is the same as that of the hydrocarbon group that can be used as R ＮＡ１ In the present invention, the number of carbon atoms in the aryl group can be the same as that of the aryl group ＮＡ１ When either the terminal group or the group has a hydrogen atom, this hydrogen atom is ＮＡ１ Interpret as follows.

[0049] In the present invention, an ether bond is included in a hydroxy group, an ester bond, etc., but the -O- contained therein is not considered an ether group. Also, an ester bond is included in a urethane bond, but the -CO-O- bond contained therein is not considered to be an ester bond. Furthermore, an amide bond is included in a urethane bond, a urea bond, etc., but the -CO-N contained therein is not considered to be an ether group. ＲＮ The - bond is not interpreted as an amide group.

[0050] A hydroxy group, an amino group, a sulfanyl group, an imino group, or the like may form a salt. The cation that forms the salt is not particularly limited, and examples thereof include metal cations, particularly metal cations of Group 1 or Group 2. The anion that forms the salt is not particularly limited, and examples thereof include halide ions.

[0051] The functional group (c) of the compound (C) is preferably a hydroxy group, a phosphate ester bond, a phosphonate ester bond, or a phosphinate ester bond, and more preferably a hydroxy group or a phosphonate ester bond, because these functional groups can cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex at a higher level.

[0052] When the compound (C) has two or more functional groups (c), the combination of the functional groups (c) is not particularly limited, but a combination of the above-mentioned preferred functional groups (c) is preferred, and a combination including a hydroxy group or a phosphonate ester bond is more preferred.

[0053] In the functional group (c), the combination of at least one hydrocarbon group and at least one functional group (c) is not particularly limited. However, in terms of being able to cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex to a higher level, a combination of an aliphatic hydrocarbon group and the above-mentioned preferred functional group (c) is preferred, a combination of a saturated aliphatic hydrocarbon and the above-mentioned preferred functional group (c) is more preferred, a combination of a group consisting of an alkane (alkyl group) and the above-mentioned preferred functional group (c) is even more preferred, and a combination of a group consisting of an alkane and a hydroxy group or a phosphonate ester bond is particularly preferred.

[0054] The compound (C) is preferably a phosphonic acid or phosphinic acid compound represented by the following formula (II).

[0055] In formula (II), R ３ , R ４ and R ５ R represents a hydrocarbon group. ３ ~R ５ The hydrocarbon group that can be used as the hydroxyl group is not particularly limited, and examples thereof include aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Aliphatic hydrocarbon groups are preferred because they can cooperate with the acidic extractant (B) to improve the mixing speed of the two phases and the solubility of the metal complex. The aliphatic hydrocarbon group is not particularly limited, and examples thereof include alkyl groups, alkenyl groups, and alkynyl groups. Alkyl groups are preferred because they can cooperate with the acidic extractant (B) to improve the mixing speed of the two phases and the solubility of the metal complex. The chain structure of the hydrocarbon group may be linear, branched, or cyclic, but branched chains are more preferred because they can cooperate with the acidic extractant (B) to achieve a higher level of both the mixing speed of the two phases and the solubility of the metal complex. The number of branches (number of branched carbon atoms) in the hydrocarbon group having a branched structure (branched hydrocarbon group) may be 1 or more, and may be 1 to 8. In terms of being able to cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex, the number of branches is preferably 1 to 6, and more preferably 1 to 4. The aromatic hydrocarbon group is not particularly limited, and is, for example, the same as the aryl group in the substituent GZ described below.

[0056] R ３ ~R ５ It is also preferred that at least one of the hydrocarbon groups that can be taken as the phosphonate ester bond is the same as the hydrocarbon group contained in compound (C), that at least one hydrocarbon group is the terminal group contained in the phosphonate ester bond, and that all of the hydrocarbon groups are the same as the hydrocarbon group contained in compound (C).

[0057] R ３ ~R ５ The total number of carbon atoms constituting the three hydrocarbon groups that can be taken as R is 14 or more, in order to cooperate with the acidic extractant (B) to improve the mixing rate of the two phases and the solubility of the metal complex. ３ ~R５ The total number of carbon atoms constituting the three hydrocarbon groups that can be taken as the aryl group is the same as the total number of carbon atoms constituting all the hydrocarbon groups contained in the compound (C).

[0058] R ３ ~R ５ The number of carbon atoms constituting each of the three hydrocarbon groups that can be taken as R is appropriately determined taking into consideration the total number of carbon atoms, and is the same as the number of carbon atoms constituting the hydrocarbon group contained in compound (C). ３ ~R ５ At least one of the three hydrocarbon groups that can be used as R has 8 or more carbon atoms. ３ ~R ５ The number of carbon atoms constituting each of the three hydrocarbon groups that can be taken as the group may be the same or different. In a preferred embodiment, the hydrocarbon group directly bonded to P in formula (II), for example, Z ３ is a single bond, R ３ The number of carbon atoms in the hydrocarbon group that can be used as the ４ and Z ５ is the above atom, R ４ and R ５ It is preferable that the number of carbon atoms of both hydrocarbon groups that can be taken as Z is equal to or smaller than that of Z. ３ is a single bond, R ３ The number of carbon atoms in the hydrocarbon group that can be taken as Z is the same as the number of carbon atoms in the medium-chain hydrocarbon group. ４ and Z ５ is the above atom, R ４ and R ５ The number of carbon atoms in both hydrocarbon groups that can be taken as R is preferably the same as the number of carbon atoms in the long-chain hydrocarbon group. ４ The number of carbon atoms in the hydrocarbon group that can be ５ The number of carbon atoms of the hydrocarbon group that can be taken as R may be different from that of the ３ ~R ５Of the three hydrocarbon groups that may be present, it is preferred that the number of carbon atoms in at least one hydrocarbon group is the same as the number of carbon atoms in the medium-chain hydrocarbon group, and it is preferred that the number of carbon atoms in at least one other hydrocarbon group is the same as the number of carbon atoms in the long-chain hydrocarbon group. Of the three hydrocarbon groups, it is preferred that two are long-chain hydrocarbon groups.

[0059] R ３ ~R ５ The combination of three hydrocarbon groups that can be used as R is not particularly limited, and a combination of an aliphatic hydrocarbon group and an aromatic hydrocarbon can also be used, but a combination of aliphatic hydrocarbon groups is preferred, a combination of alkyl groups is more preferred, and a combination of alkyl groups having a branched structure is even more preferred, in that they can cooperate with the acidic extractant (B) to improve the mixing rate of both phases and the solubility of the metal complex. ３ ~R ５ As for the possible combinations of three hydrocarbon groups, focusing on the number of carbon atoms, it is preferred that at least one hydrocarbon group has 8 or more carbon atoms and at least one hydrocarbon group has 16 or more carbon atoms, and it is more preferred that one hydrocarbon group has 8 or more carbon atoms and two hydrocarbon groups have 16 or more carbon atoms.

[0060] In formula (II), Y ２ represents an oxygen atom or a sulfur atom, and is preferably an oxygen atom.

[0061] In formula (II), Z ３ , Z ４ and Z ５ each represents a single bond, an oxygen atom, or a sulfur atom, and at least one is a single bond. ３ ~Z ５ At least one of Z is an oxygen atom or a sulfur atom. ３ ~Z ５ may be single bonds, but Z is preferably a single bond in that it can cooperate with the acidic extractant (B) to improve the mixing rate of both phases and the solubility of the metal complex. ３ ~Z ５ It is preferred that one of Z is a single bond. ３ ~Z ５When Z is not a single bond, it is preferably an oxygen atom. ３ ~Z ５ The combination of is not particularly limited, and examples thereof include Z ３ is a single bond, and Z ４ is an oxygen atom or a sulfur atom, and Z ５ is a single bond, an oxygen atom or a sulfur atom, and Z ３ is a single bond, and Z ４ and Z ５ is an oxygen atom is more preferred.

[0062] In formula (II), R ３ -Z ３ - group, R ４ -Z ４ - group and R ５ -Z ５ The combination of - groups is not particularly limited, and examples thereof include the above-mentioned R ３ ~R ５ The above combinations and Z ３ ~Z ５ and the combination of the above, and Z having a single bond is preferred in that it can cooperate with the acidic extractant (B) to improve the mixing rate of both phases and the solubility of the metal complex. ３ R bonded to ３ The hydrocarbon group that can be taken by Z is the above-mentioned medium-chain hydrocarbon group, and Z ４ and Z ５ R bonded to ４ or R ５ The hydrocarbon group which Z can take is preferably the long chain hydrocarbon group described above, and Z taking a single bond is preferably a long chain hydrocarbon group. ３ R bonded to ３ The hydrocarbon group may have 8 or more carbon atoms, and Z may have an oxygen atom or a sulfur atom. ４ and Z ５ R bonded to ４ or R ５ It is more preferable that the number of carbon atoms in the hydrocarbon group be 16 or more.

[0063] In formula (II), R ３ ~R ５ , Z ３ ~R ５ and Y ２The combination of is not particularly limited and can be determined appropriately. Preferred examples of the combination include combinations of the preferred elements indicated by the respective symbols.

[0064] The compound (C) may have a substituent, and examples of the substituent that the compound (C) may have include groups selected from the following substituents GZ.

[0065] - Substituent GZ - an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), In the present invention, alkyl groups usually include cycloalkyl groups, but will be described separately here.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), aralkyl groups (preferably aralkyl groups having 7 to 23 carbon atoms, for example, benzyl, phenethyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably 5- or 6-membered heterocyclic groups having at least one oxygen atom, sulfur atom, or nitrogen atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups.For example, a tetrahydropyran ring group, a tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, a pyrrolidone group, etc.), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), a heterocyclic oxy group (a group in which an -O- group is bonded to the above heterocyclic group), an alkoxycarbonyl group (preferably or an alkoxycarbonyl group having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.), an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), a heterocyclic oxycarbonyl group (a group in which an —O—CO— group is bonded to the above heterocyclic group), an amino group (preferably an amino group having 0 to 20 carbon atoms, an alkylamino group, or an arylamino group, for example, amino(—NH ２), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl group (including an alkylcarbonyl group, an alkenylcarbonyl group, an alkynylcarbonyl group, an arylcarbonyl group, or a heterocyclic carbonyl group, preferably an acyl group having 1 to 20 carbon atoms, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, nicotinoyl, etc.), acyl Oxy groups (including alkylcarbonyloxy groups, alkenylcarbonyloxy groups, alkynylcarbonyloxy groups, and heterocyclic carbonyloxy groups, preferably acyloxy groups having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, and nicotinoyloxy), aryloyloxy groups (preferably aryloyloxy groups having 7 to 23 carbon atoms, for example, benzoyloxy and naphthoyloxy), carbamoyl groups (preferably carbamoyl groups having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino groups (preferably acylamino groups having 1 to 20 carbon atoms, for example, acetylamino, benzoylamino, etc.), alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio groups (preferably arylthio groups having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), heterocyclic thio groups (groups in which an -S- group is bonded to the above heterocyclic group), alkylsulfonyl groups (preferably alkylsulfonyl groups having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl groups (preferably an arylsulfonyl group having 6 to 22 carbon atoms, for example, benzenesulfonyl; an alkylsilyl group (preferably an alkylsilyl group having 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl; an arylsilyl group (preferably an arylsilyl group having 6 to 42 carbon atoms, for example, triphenylsilyl; an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl, triethoxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; a phosphoryl group (preferably a phosphoric acid group having 0 to 20 carbon atoms, for example, -OP(=O)(R, Ｐ ) ２ ), a phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, —P(═O)(R Ｐ ) ２ ), a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R Ｐ ) ２ ), a phosphonic acid group (preferably a phosphonic acid group having 0 to 20 carbon atoms, for example, —PO(OR Ｐ ) ２ ), sulfo group (sulfonic acid group), carboxy group, hydroxy group, sulfanyl group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). Ｐis a hydrogen atom or a substituent (preferably a group selected from the substituents GZ). Each of the groups listed as the substituents GZ may be further substituted with the substituent GZ. The alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group and / or alkynylene group may be cyclic or chain-like, and may be linear or branched.

[0066] The molecular weight of compound (C) is not particularly limited, but can be, for example, 350 to 2000. In terms of solubility in the oil phase, it is preferably 400 to 1500, and more preferably 500 to 1000. Compound (C) may be a commercially available product or a synthetic product. Compound (C) can be synthesized by a known synthesis method, for example, the method described in Patent Document 2, or the synthesis method described in the Examples below.

[0067] Specific examples of compound (C) include those shown below in addition to those synthesized in the examples, but the present invention is not limited to these.

[0068] (Other Components) The other components that may be contained in the metal extractant composition of the present invention are not particularly limited, and examples thereof include metal extractants other than the acidic extractant (B) (other metal extractants), solvents, etc. The other metal extractants are not particularly limited, and examples thereof include various known metal extractants used for extracting metal ions. Suitable examples of the solvent include the organic solvents used in the oil phase described below.

[0069] (Composition of Metal Extractant Composition) The content of each component in the metal extractant composition of the present invention is not particularly limited and may be determined appropriately. For example, in the metal extractant composition of the present invention, the molar ratio of compound (C) to acidic extractant (B) ([compound (C) / acidic extractant (B)]) is not particularly limited and can be, for example, 10.0 to 0.0001, preferably 5.0 to 0.0003, and more preferably 3.0 to 0.0005. When the metal extractant composition of the present invention is used as is (without adjusting the components), the molar ratio of compound (C) to acidic extractant (B) is preferably 1.0 to 0.001, more preferably 0.5 to 0.003, even more preferably 0.2 to 0.003, and particularly preferably 0.1 to 0.005, in order to achieve both the mixing speed of the two phases and the solubility of the metal complex.

[0070] In the metal extractant composition of the present invention, the content of the acidic extractant (B) relative to the total mass of the acidic extractant (B) and the compound (C) is appropriately determined in consideration of the molar ratio, etc., and can be, for example, 99.9 to 70.0 mass%, preferably 99.7 to 80.0 mass%, and more preferably 99.5 to 90.0 mass%. Similarly, the content of the compound (C) relative to the total mass of the acidic extractant (B) and the compound (C) is appropriately determined in consideration of the molar ratio, etc., and can be, for example, 0.1 to 30.0 mass%, preferably 0.3 to 20.0 mass%, and more preferably 0.5 to 10.0 mass%.

[0071] (Preparation of Metal Extractant Composition) The metal extractant composition of the present invention can be prepared by mixing the acidic extractant (B), the compound (C), and optionally other components. The mixing conditions are not particularly limited.

[0072] [Metal Extractant Kit] The metal extractant composition of the present invention is a mixture of an acidic extractant (B) and a compound (C). However, the present invention can also be a metal extractant kit having a first agent containing the acidic extractant (B) and a second agent containing the compound (C). In the metal extractant kit, the acidic extractant (B) contained in the first agent is the same as the acidic extractant (B) contained in the metal extractant composition of the present invention. The first agent can contain other components as described above, for example, a liquid agent in which the acidic extractant (B) is dissolved or dispersed in the solvent. In the metal extractant kit, the compound (C) contained in the second agent is the same as the compound (C) contained in the metal extractant composition of the present invention. The second agent can contain other components as described above. The metal extractant kit can be used after mixing the first agent and the second agent in a wet extraction method to prepare the metal extractant composition of the present invention, or the first agent and the second agent can be used separately.

[0073] [Method for Separating and Recovering Metal Ions] The method for separating and recovering metal ions of the present invention (hereinafter sometimes referred to as the "separation and recovery method of the present invention") uses the metal extractant composition of the present invention. For example, it is a method in which an aqueous phase containing multiple metal ions and an oil phase containing an acidic extractant (B) are mixed in the presence of compound (C). In the separation and recovery method of the present invention, the metal extractant composition of the present invention can be used as is (as a mixture of acidic extractant (B) and compound (C)), or the acidic extractant (B) and compound (C) can be used separately. That is, one embodiment of the separation and recovery method of the present invention includes a method in which an aqueous phase containing multiple metal ions and an oil phase containing the metal extractant composition of the present invention are mixed. Another embodiment of the separation and recovery method of the present invention includes a method in which an aqueous phase containing multiple metal ions, an oil phase containing acidic extractant (B), and compound (C) are mixed. In another embodiment, compound (C) may be mixed alone or as a solution or dispersion.

[0074] In the separation and recovery method of the present invention, rapid mixing of the aqueous phase and the oil phase is believed to cause the acidic extractant (B) to coordinate with the metal ion to form a metal complex, and further, the compound (C) to have affinity for the metal complex. The affinity of the compound (C) for the metal complex is believed to further enhance the metal ion extraction ability of the acidic extractant (B) and further enhance the solubility of the affinity metal complex. As a result, even with a large treatment volume, a large amount of a metal complex containing a specific metal ion can be transferred (extracted) from the aqueous phase to the oil phase. Furthermore, the specific metal ion can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity. Here, the metal ions extracted into the oil phase may be a portion of the multiple metal ions contained in the aqueous phase, or all of the heterogeneous metal ions contained in the aqueous phase. The separation and recovery method of the present invention can extract one type of metal ion as a valuable metal element ion into the oil phase, preferably with a high recovery rate and more preferably with high selectivity, but can also extract two or more heterogeneous metal ions, preferably two or more heterogeneous metal ions, into the oil phase. For example, one metal ion selected from two or more different metal ions belonging to Groups 1 to 14 of the periodic table, preferably two or more different metal ions belonging to Groups 8 to 11, can be extracted into an oil phase, preferably with a high recovery rate and more preferably with high selectivity. In particular, the separation and recovery method of the present invention can extract one metal ion selected from two or more different metal ions belonging to Groups 9 to 12 of the periodic table, particularly preferably cobalt ions and nickel ions, which are different metal ions of the same period, into an oil phase, preferably with a high recovery rate and more preferably with high selectivity.

[0075] <Aqueous Phase> The water that forms the aqueous phase is not particularly limited, but (ultra) pure water, ion-exchanged water, etc. can be used.

[0076] The metal ions contained in the aqueous phase may contain at least two types of ions of metal elements belonging to Groups 1 to 14 of the periodic table, preferably at least two types of metal ions belonging to Groups 3 to 14, and may also contain metal ions belonging to Groups 15 to 17. In the present invention, the aqueous phase preferably contains two or more types of metal ions belonging to Groups 1 to 14, more preferably two or more types of metal ions belonging to Groups 3 to 14, and even more preferably contains ions of at least one transition metal element (metal element belonging to Groups 3 to 12). In an embodiment containing at least one transition metal element, the aqueous phase preferably contains two or more types of metal ions belonging to Groups 4 to 12, more preferably two or more types of metal ions belonging to Groups 4 to 10, even more preferably two or more types of metal ions belonging to Groups 8 to 12, particularly preferably two or more types of metal ions belonging to Groups 9 to 12, and most preferably two or more types of metal ions belonging to Groups 9 and 10. The metal ions belonging to each group are not particularly limited, but are preferably metal ions belonging to periods 4 to 6 of the periodic table, and more preferably metal ions belonging to periods 4 or 5. The number of types of metal ions is not particularly limited as long as it is two or more types, and can be, for example, 2 to 15 types, preferably 2 to 8 types, and more preferably 2 to 5 types. The combinations of multiple metal ions are not particularly limited, but examples of combinations of groups include combinations of Groups 9 and 10, combinations of Groups 9 and 12, combinations of Groups 9 and 11, combinations of Groups 9, 10 and 12, combinations of Groups 4 and 9, combinations of Groups 7, 9 and 10, and combinations of Groups 7, 8, 9 and 10. In the present invention, two or more types of metal ions belonging to each group may be used, but a single type is preferred in terms of exhibiting high selectivity.

[0077] Specific combinations of metal ions include, for example, combinations including Co and Ni, combinations including Co and Zn, combinations including Co and Cu, combinations including Rh and Ni, combinations including Zr and Rh, combinations including Mn, Co and Ni, and combinations of Mn, Fe, Co and Ni. The multiple types of metal ions contained in the aqueous phase may include metal ions of the same group, or may include metal ions of different groups. The number of types of different metal ions contained in the aqueous phase may be two or more, and is preferably, for example, two to four types, and more preferably two types.

[0078] The metal elements belonging to each group are not particularly limited, and appropriate atoms can be used. For example, preferred metal elements belonging to Group 1 include Li, Na, Rb, and Cs. Preferred metal elements belonging to Group 2 include Mg, Ca, Sr, and Ba. Preferred metal elements belonging to Group 3 include Sc and Y. Preferred metal elements belonging to Group 4 include Ti, Zr, and Hf. Preferred metal elements belonging to Group 5 include V, Nb, and Ta. Preferred metal elements belonging to Group 6 include Cr, Mo, and W. Preferred metal elements belonging to Group 7 include Mn and Tc. Preferred metal elements belonging to Group 8 include Fe, Ru, and Os. Preferred metal elements belonging to Group 9 include Co, Rh, and Ir. Preferred metal elements belonging to Group 10 include Ni, Pd, and Pt. Preferred metal elements belonging to Group 11 include Cu, Ag, and Au. Preferred examples of metal elements belonging to Group 12 include Zn, Cd, and Hg. Preferred examples of metal elements belonging to Group 13 include Al, Ga, In, and Tl. Preferred examples of metal elements belonging to Group 14 include Ga, Sn, and Pb. Preferred examples of metal elements belonging to Group 15 include Sb and Bi. Preferred examples of metal elements belonging to Group 16 include, but are not limited to, Te.

[0079] The multiple types of metal ions can be prepared appropriately, and examples thereof include various metal salts (salts of inorganic acids such as nitric acid and sulfuric acid of typical elements or organic acids such as acetic acid), mixtures of mined metals (ions), materials recovered from metal waste, metals recovered from other wastes such as waste batteries (waste LiBs), and mixtures thereof. Examples of metals recovered from waste LiBs include materials recovered by known methods such as wet treatment and electrolysis.

[0080] The total content of multiple metal ions in the aqueous phase is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 1,000,000 ppm by mass, preferably 1,000 to 100,000 ppm by mass, and more preferably 1,000 to 80,000 ppm by mass. The total content of metal ions belonging to groups 9 to 12 among the metal ions is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 80,000 ppm by mass, and preferably 1,000 to 60,000 ppm by mass. The total content of metal ions belonging to groups 3 to 7 and groups 13 to 16 among the metal ions is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 60,000 ppm by mass, and preferably 1,000 to 30,000 ppm by mass. The content of the metal ions belonging to each group is not particularly limited and may be set as appropriate, but may be, for example, 1,000 to 60,000 ppm by mass, and preferably 1,000 to 50,000 ppm by mass. When two or more types of metal ions belonging to each group are contained, the content of the metal ions belonging to each group is the total content.

[0081] In the present invention, when the aqueous phase contains metal ions from different groups, the content of metal ions from one group may be the same as, or greater than, or less than, the content of metal ions from another group. The separation and recovery method of the present invention preferably enables separation and recovery of metal ions with high selectivity, so the content of metal ions from different groups does not need to be set to a specific ratio. For example, the mass ratio of the content of metal ions from a specific group (e.g., metal ions extracted at the maximum extraction rate) to the content of metal ions from another group (e.g., metal ions other than the metal ions extracted at the maximum extraction rate (including unextracted metal ions)) [content of metal ions from a specific group:content of metal ions from another group] can be, for example, 100:0.5 to 20,000, preferably 100:1 to 10,000, and more preferably 100:10 to 5,000.

[0082] The pH of the aqueous phase is not particularly limited and can be set as appropriate. However, taking into consideration factors such as the solubility of metal ions and the formation of complex ions, it is preferably set to, for example, 0.1 to 10, and more preferably 2.0 to 9.0. The pH of the aqueous phase can be adjusted using a pH adjuster such as an acid or alkali. Known acids can be used without particular limitation, including inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, organic phosphoric acid, and organic sulfonic acid. Known alkalis can be used without particular limitation, including inorganic alkalis and organic alkalis, with inorganic alkalis being preferred. Examples of inorganic alkalis include metal alkalis such as hydroxides and carbonates of Group 1 or Group 2 metals, as well as aqueous ammonia and ammonium chloride. Examples of organic alkalis include organic ammonium salts. The temperature of the aqueous phase is not particularly limited and can be set to, for example, 10 to 60°C.

[0083] The aqueous phase may contain, as necessary, a ligand (compound) that coordinates with the metal ion or a compound that generates the ligand. The aqueous phase can be prepared by dissolving metal ions in water. The conditions for preparing the aqueous phase are not particularly limited. For example, the preparation temperature can be 10 to 60°C. The aqueous phase may contain a masking agent in addition to the metal ions. Any known masking agent can be used without any particular limitation. Examples of the masking agent include monodentate ligands such as ammonia and chelating agents such as dithizone.

[0084] <Oil Phase> In the separation and recovery method of the present invention, an oil phase (organic phase) containing one or more metal extractant compositions of the present invention is used in addition to the aqueous phase. The acidic extractant (B) exhibits solubility in organic solvents and is present in the oil phase, where it coordinates with metal ions present near the interface between the aqueous phase and the oil phase, thereby transferring these metal ions to the oil phase. In the present invention, solubility in organic solvents refers to the property of the metal extractant being soluble in organic solvents at the content described below. In addition, compound (C) has the function of increasing the solubility in the oil phase of a metal complex in which the acidic extractant (B) coordinates with a metal ion.

[0085] The organic solvent forming the oil phase is not particularly limited, and any suitable organic solvent can be used. Examples include alcohol solvents, ether solvents, hydrocarbon solvents (aromatic solvents, aliphatic solvents), halogenated solvents, etc. Among these, hydrocarbon solvents are preferred, and various solvents that are fractions of petroleum are more preferred, and aromatic, paraffinic, naphthenic, kerosene, gasoline, naphtha, kerosene, and diesel hydrocarbon solvents are even more preferred.

[0086] The content of the acidic extractant (B) in the oil phase is appropriately set taking into consideration the content of metal ions, the amount of coordination to the metal ions, and the like. For example, the content in the oil phase can be 20 to 10,000 mmol / L (mM), preferably 50 to 2,000 mmol / L. When the oil phase contains compound (C) (an embodiment in which compound (C) is not additionally added to the combined solution), the content of compound (C) in the oil phase is appropriately set taking into consideration the content of metal ions, the content of acidic extractant (B), and the like. For example, the content in the oil phase can be 0.1 to 500 mmol / L (mM), preferably 0.5 to 200 mmol / L. Furthermore, the molar ratio of compound (C) to acidic extractant (B) in the oil phase ([compound (C) / acidic extractant (B)]) can be appropriately determined and can be the molar ratio described above in the metal extractant composition of the present invention, and is preferably the molar ratio described above when the metal extractant composition of the present invention is used as is. The temperature of the oil phase is not particularly limited and can be, for example, 10 to 60°C.

[0087] The oil phase may contain appropriate components in addition to the acidic extractant (B) and the compound (C). The oil phase can be prepared by mixing or dissolving the acidic extractant (B) and, if necessary, the compound (C) in an organic solvent. The preparation conditions for the oil phase are not particularly limited, and the preparation temperature can be, for example, 10 to 60°C.

[0088] In the separation and recovery method of the present invention, when the acidic extractant (B) and the compound (C) are used separately, an oil phase containing the acidic extractant (B) can be used. The organic solvent used in the oil phase containing the acidic extractant (B) is as described above. The content of the acidic extractant (B) in the oil phase containing the acidic extractant (B) can be the content in the oil phase. However, when the compound (C) is used as a solution or dispersion, the content in the oil phase is defined as the content relative to the total amount of the oil phase containing the acidic extractant (B) and the solution or dispersion of the compound (C). When the compound (C) is used as a solution or dispersion, the organic solvent described above can be used as the solvent for dissolving or dispersing the compound (C).

[0089] (Contact, Mixing) In the separation and recovery method of the present invention, the aqueous phase and the oil phase are mixed and allowed to stand. The mixing and standing conditions are not particularly limited and can be set appropriately. For example, mixing can be performed using various mixing devices. Examples of mixing devices include a method using a magnetic stirrer (stirrer tip), a method using a mechanical stirrer, and a method using a mixer. The stirring conditions (stirring speed, stirring time, etc.) are sufficient as long as they allow mixing of the aqueous phase and the oil phase (conditions under which the acidic extractant (B) coordinates to the metal ions), and are set appropriately depending on the combination of metal ions and acidic extractant (B), the mixing temperature, and the mixing device. For example, the stirring speed can be 80 rpm or more, preferably 100 to 200 rpm, as the rotation speed of the magnetic stirrer, etc. The stirring time (mixing time) is not uniquely determined by the stirring conditions, etc., but can be, for example, 10 minutes to 24 hours. In the present invention, since the aqueous phase and the oil phase can be mixed quickly, the stirring time can be set to a short time, for example, 1 hour or less. The mixing temperature is not particularly limited and can be, for example, 10 to 60°C. The standing conditions are not particularly limited and can be set appropriately as long as the aqueous phase and the oil phase separate into two layers. The standing time in the wet extraction method is usually set to 10 minutes to 24 hours after mixing is stopped. The standing temperature is not particularly limited and can be, for example, 10 to 60°C.

[0090] When mixing the aqueous phase and the oil phase, the mixing ratio of the aqueous phase to the oil phase is appropriately set depending on the content (concentration) of the metal ions, the content (concentration) of the acidic extractant (B), etc., and is not uniquely determined. For example, when mixing the aqueous phase and the oil phase satisfying the above concentrations, the ratio of the oil phase to 100 mL of the aqueous phase can be 50 to 2000 mL, preferably 80 to 1000 mL, and more preferably 80 to 200 mL. On the other hand, when focusing on the metal ions present in the aqueous phase, it is preferable to mix the oil phase at a ratio of 1.0 to 20 molar times the total content (moles) of the metal ions, and more preferably at a ratio of 1.5 to 10 molar times the acidic extractant (B). The content of the acidic extractant (B) relative to the total content of metal ions that can be coordinated with the acidic extractant (B) (also referred to as the mixed amount; the ratio of the number of moles of the acidic extractant (B) to the total number of moles of metal ions: molar ratio) can be, for example, 1.0 to 10.0 equivalents, preferably 1.0 to 6.0 equivalents, and also preferably 1.5 to 6.0 equivalents. Here, the metal ions that can be coordinated with the acidic extractant (B) refer to metal ions that are coordinated with the acidic extractant (B) and extracted into the oil phase.

[0091] In mixing the aqueous phase and the oil phase, the molar ratio of compound (C) to acidic extractant (B) [compound (C) / acidic extractant (B)] is not particularly limited, but is preferably 1.0 to 0.001 in terms of the mixing speed of the two phases and the solubility of the metal complex. In the separation and recovery method of the present invention, this molar ratio [compound (C) / acidic extractant (B)] is more preferably 0.5 to 0.003, even more preferably 0.2 to 0.003, and particularly preferably 0.1 to 0.005, in order to achieve a higher level of both the mixing speed of the two phases and the solubility of the metal complex.

[0092] When mixing the aqueous phase and the oil phase, the pH of the mixed system (combined solution) is usually adjusted. Here, the pH set for the specific metal ion to be extracted is not unique and is appropriately determined taking into consideration the pKa of the acidic extractant (B), the complex formation constant between the acidic extractant (B) and the metal ion, the coordination number of the metal ion, and the like. The pH of the mixed system is preferably 0.01 to 14. For example, in order to achieve both the mixing rate of the two phases and the solubility of the metal complex, it is more preferably 0.1 to 10, even more preferably 0.5 to 7.0, and particularly preferably 1.0 to 6.5. When separating and recovering metal ions belonging to Group 9 and Group 10, the pH of the mixed system is most preferably 3.0 to 6.5 within the above range. In the present invention, it is preferable to set the pH of the mixed system to a predetermined value depending on the combination of metal ions and acidic extractant (B), in order to achieve both the mixing rate of the two phases and the solubility of the metal complex. For example, the pH can be adjusted to the pH obtained by adding a base (e.g., sodium hydroxide) in an amount sufficient to neutralize 0.5 equivalents of the metal extractant contained in the oil phase that would be neutralized upon mixing with the aqueous phase. The pH can be adjusted using the pH adjuster described above or an aqueous solution thereof. When mixing the aqueous phase and the oil phase, the pH of the mixed system is adjusted before the above-described mixing of the aqueous phase and the oil phase.

[0093] The aqueous phase and the oil phase are mixed in this manner, and the resulting two-phase separation fluid (solvent extraction phase, solvent extraction system) is one in which the aqueous phase and the oil phase are separated and exist in a layered state while in contact with each other. Among the multiple metal ions described above, metal ions coordinate-bonded to the acidic extractant (B) are present (migrate) in the oil phase. The number of metal ions extracted into the oil phase is ideally one, but may be two or more. In this case, it can be, for example, 2 to 10 types, preferably 2 to 6 types, and more preferably 2 or 3 types. The two or more metal ions extracted into the oil phase among the multiple metal ions are not particularly limited, but are preferably the same as the two or more heterogeneous metal ions (combination) contained in the aqueous phase described above.

[0094] The separation and recovery method of the present invention, which is a simple method of mixing an aqueous phase and an oil phase and allowing them to stand, allows the aqueous phase containing metal ions to be mixed quickly with the oil phase, and also increases the solubility of metal complexes consisting of metal ions and an acidic extractant in the oil phase, thereby allowing for an increase in the throughput. Even with an increased throughput, a specific metal ion from among multiple metal ions can be extracted, separated, and recovered, preferably with a high recovery rate and more preferably with high selectivity. In particular, even when two or more metal ions are extracted, one of the metal ions can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity.

[0095] The type of metal ion that can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity, is not uniquely determined by the group or period of the metal ion, the content, the type of acidic extractant (B), etc. For example, when extracting a metal ion belonging to Group 9 and a metal ion belonging to Group 10 into an oil phase, the metal ion belonging to Group 9 can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity. In particular, when extracting Co ions as the metal ion belonging to Group 9 and Ni ions as the metal ion belonging to Group 10, the Co ions or Ni ions can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity. Furthermore, when extracting a metal ion belonging to Group 9 and a metal ion belonging to Group 11 into an oil phase, the metal ion belonging to Group 11 can be separated and recovered, preferably with a high recovery rate and more preferably with high selectivity. Furthermore, when metal ions belonging to Group 9, metal ions belonging to Group 10, and metal ions belonging to Group 12 are extracted into an oil phase, the metal ions belonging to Group 10 are usually not extracted, but the metal ions belonging to Group 12 can be separated and recovered preferably with a high recovery rate, and more preferably with high selectivity.

[0096] The separation and recovery method of the present invention can extract and recover one or more metal ions from multiple metal ions present in an aqueous phase, preferably with a high recovery rate, more preferably with high selectivity, into an oil phase, even when the treatment volume is increased. In particular, the separation and recovery method of the present invention can extract two or more metal ions while recovering one of the metal ions, preferably with a high recovery rate, more preferably with high selectivity. Therefore, by subjecting the aqueous phase containing two or more metal ions stripped from the oil phase to the separation and recovery method of the present invention, the selectivity for one metal ion can be further increased without significantly impairing the recovery rate, resulting in the recovery of high-purity metal ions, preferably with a high recovery rate. Such a separation and recovery method of the present invention can also be referred to as a method for extracting two or more metal ions.

[0097] In the separation and recovery method of the present invention, the acidic extractant (B) coordinates with the metal ion and cooperates with the compound (C) to extract the metal ion into the oil phase, so the aqueous phase and the oil phase do not need to contain compounds that cooperate with the acidic extractant (B) to extract the metal ion, such as compounds that coordinate with the metal ion or compounds that generate ligands, such as known metal extractants, etc. The separation and recovery method of the present invention usually uses an aqueous phase containing a specific metal ion as an essential component and an oil phase containing the acidic extractant (B) and the compound (C) as essential components.

[0098] The separation and recovery method of the present invention may include steps other than the step of mixing and allowing the aqueous phase and oil phase to stand. Examples include a step of premixing the aqueous phase and oil phase before adjusting the pH, a step of stripping (isolating) metal ions from the oil phase obtained by mixing and allowing the aqueous phase and oil phase to stand (a step of stripping metal ions from the oil phase to recover the acidic extractant (B)), a step of recovering the stripped metal ions as a compound (salt), a step of purifying the stripped metal ions or their compounds, a step of purifying the recovered acidic extractant (B), and even a step of preliminarily removing ions of metal elements belonging to Group 1 or Group 2 of the periodic table of elements. The mixing conditions for the premixing step are not particularly limited, and examples include the mixing conditions for the step of mixing the aqueous phase and oil phase described above (however, pH adjustment is not required). As a method for back-extracting (isolating) metal ions from the oil phase, known methods can be applied without any particular limitation, and can be carried out, for example, by using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid to make the liquid phase acidic, for example, to a pH of 2 to 4. As a method for recovering the back-extracted metal ions as a compound, known methods can be applied without any particular limitation.

[0099] The separation and recovery method of the present invention may be carried out as a batch process or a continuous process. The apparatus for carrying out the separation and recovery method of the present invention is not particularly limited, and known equipment can be used. Examples include a separatory funnel, a mixer settler, and the like. A contacting and mixing apparatus using a liquid delivery device such as a flow synthesis apparatus or an emulsion flow apparatus can also be used. The above-mentioned conditions can be applied to the contacting, mixing, and standing conditions in continuous processing. The amount of the aqueous phase used to flow can also be set to be greater than the above-mentioned mixing ratio of the aqueous phase to the oil phase.

[0100] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the following examples, "parts" and "%" representing compositions are based on mass unless otherwise specified. In the present invention, "room temperature" means 25°C.

[0101] [Synthesis and Preparation of Acidic Extractant (B) and Compound (C)] The acidic extractant (B) and compound (C) shown below were synthesized or prepared. The compounds shown below were commercially available products. PC-88A: mono-2-ethylhexyl (2-ethylhexyl)phosphonate (manufactured by Tokyo Chemical Industry Co., Ltd.) A-1: ​​2-hexyl-1-decanol (manufactured by Tokyo Chemical Industry Co., Ltd.) A-6: isotridecanol (C １３ H ２７ OH isomer mixture, manufactured by KH Neochem Co., Ltd.)

[0102]

[0103] <Synthesis of Compound E-1> Compound E-1 was synthesized as follows. Specifically, 89 g of diethyl phosphite (manufactured by Tokyo Chemical Industry Co., Ltd.) and 450 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked recovery flask and stirred thoroughly. While the three-necked recovery flask was ice-cooled, 23.2 g of sodium hydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added and stirred for 20 minutes while still ice-cooled. Thereafter, the reaction solution was heated and stirred for 30 minutes under reflux. Next, while the three-necked recovery flask was ice-cooled, 70.0 g of 1-bromo-2-ethylhexane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise to the resulting reaction solution over 20 minutes, and the mixture was stirred at an internal temperature of 45°C for 24 hours. 300 g of water was added to the resulting reaction solution, followed by extraction with toluene, and the solvent was removed by distillation under reduced pressure to obtain 103 g of a yellow liquid.

[0104] Next, the obtained yellow liquid and 400 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked recovery flask and stirred thoroughly. 113 g of bromotrimethylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added to the three-necked recovery flask and stirred at room temperature for 4 hours. After the solvent was distilled off under reduced pressure from the obtained reaction solution, 530 g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred at an internal temperature of 40°C for 3 hours. 200 mL of aqueous sodium hydroxide solution (4 mol / L) was added to the reaction solution obtained in this manner, and the aqueous layer was washed twice with toluene. 65 mL of concentrated hydrochloric acid was added to the obtained aqueous solution, and the mixture was extracted with toluene. The solvent was then distilled off under reduced pressure to obtain 57.2 g of compound A (yield 81%, 2 steps). 20.0 g of compound A and 2-butyl-1-n-octanol (branched C １２ H ２５ 19.2 g of cyclohexyl carbodiimide (manufactured by Tokyo Chemical Industry Co., Ltd.) and 120 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and stirred, and then the temperature was raised to a reflux state. A solution of 23.4 g of dicyclohexylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 120 g of tetrahydrofuran was added dropwise thereto over 3 hours, and then the mixture was stirred for 4 hours. The resulting reaction solution was returned to room temperature, and the white solid was removed by filtration. The solvent was distilled off under reduced pressure from the resulting filtrate. The resulting crude product was dissolved in toluene and washed with water, and then the solvent was distilled off under reduced pressure to obtain 31.1 g (yield 83%) of compound E-1 as a pale yellow liquid.

[0105] The compound E-1 thus synthesized was identified as follows: Compound E-1 was dissolved in deuterated chloroform, １ H-NMR was measured (apparatus: BLUKER 400). δ (ppm): 9.61 (1H, br s), 3.90 (2H, t, J = 5.6 Hz), 1.80-1.21 (28H, m), 0.91-0.86 (12H, m). Furthermore, the m / z: 362.4 obtained by HPLC-MS was [M+H ＋ (Precise molecular weight of E-1: 362.3) From the above, the obtained compound was identified as having the structure shown in E-1 above.

[0106] <Synthesis of Compounds E-2 and E-3> In the synthesis of Compound E-1, 1-bromo-2-ethylhexane and / or 2-butyl-1-n-octanol was used in the synthesis of Compound E-1. １ and R ２ Compounds E-2 and E-3 were synthesized and identified in the same manner as in the synthesis of compound E-1, except that the corresponding groups were changed to halides or alcohols.

[0107] <Synthesis of Compound A-2> Compound A-2 was synthesized as follows. In a 500 mL three-neck flask, 20.0 g of the compound A obtained in the synthesis of compound E-1 and 2-butyl-1-n-octanol (branch C １２ H ２５ 38.4 g of cyclohexyl carbodiimide (manufactured by Tokyo Chemical Industry Co., Ltd.) and 120 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and stirred, and the temperature was raised to a reflux state. A solution of 44.6 g of dicyclohexylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 120 g of tetrahydrofuran was added dropwise thereto over 3 hours, and the mixture was stirred for 4 hours. The resulting reaction solution was returned to room temperature, and the white solid was removed by filtration. The solvent was distilled off under reduced pressure from the resulting filtrate. The resulting crude product was dissolved in toluene and washed with water, and the solvent was distilled off under reduced pressure to obtain 41.2 g (yield 75%) of Compound A-2 as a pale yellow liquid.

[0108] The compound A-2 thus synthesized was identified as follows: Compound A-2 was dissolved in deuterated chloroform, １ H-NMR was measured (apparatus: BLUKER 400). δ (ppm): 3.71 (4H, t, J = 5.6 Hz), 1.80-1.21 (45H, m), 0.91-0.86 (18H, m). Furthermore, the m / z: 530.6 obtained by HPLC-MS was [M+H ＋ (Precise molecular weight of E-1: 530.5) From the above, the obtained compound was identified as having the structure shown in A-2 above.

[0109] <Synthesis of Compounds A-3 and A-4> In the synthesis of Compound A-2, 1-bromo-2-ethylhexane and / or 2-butyl-1-octanol was used in the synthesis of a compound represented by the chemical formula (i.e., the hydrocarbon group of Compound (C) and the R ３ ~R ５ Compounds A-3 and A-4 were synthesized and identified in the same manner as in the synthesis of compound A-2, except that the corresponding group was changed to a halide or alcohol.

[0110] <Synthesis of Compound A-5> 2-heptyl-1-undecanol (Diadol 18G-C, branched C １８ H ３５ Composition 18GPA was obtained using a hydroxypropyl methylcellulose (OH, manufactured by Mitsubishi Chemical Corporation) according to the synthesis method for composition 18GPA described in Patent Document 1. This composition 18GPA was purified by silica gel column chromatography (eluent: hexane 100%) to synthesize compound A-5.

[0111] <Synthesis of Compound A-7> Compound A-7 was synthesized and identified in the same manner as in the synthesis of Compound A-5, except that 2-heptyl-1-undecanol was changed to 2-hexyl-1-decanol.

[0112] <Synthesis of Compound T-1> 30.7 g of phosphoryl chloride and 150 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 500 mL three-neck flask, and the mixture was stirred and then cooled with ice until the internal temperature was 5° C. or less. １８ H ３５A solution containing 102.9 g of hexane (manufactured by Mitsubishi Chemical Corporation) and 38.5 g of triethylamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise over 1 hour, and the mixture was then warmed to room temperature and stirred for 4 hours. The reaction solution was then cooled to 5°C or below, and 80 g of water was slowly added. The resulting reaction solution was stirred at 60°C for 2 hours, after which 100 g of heptane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, stirred, and allowed to stand. After removing the aqueous layer, the solvent was distilled off from the oil layer under reduced pressure to obtain a crude product. The resulting crude product was purified by silica gel column chromatography (eluent: 100% hexane) to obtain 91.0 g (75% yield) of a pale yellow liquid, Compound T-1. The compound T-1 synthesized in this manner was identified as follows. Specifically, Compound T-1 was dissolved in deuterated chloroform, １ H-NMR was measured (apparatus: BLUKER 400). δ (ppm): 10.34 (1H, br s), 4.12 (4H, t, J = 5.8 Hz), 2.01-1.21 (58H, m), 0.91-0.86 (12H, m). Furthermore, the m / z: 602.6 obtained by HPLC-MS was [M+H ＋ (Precise molecular weight of E-1: 602.5) From the above, the obtained compound was identified as having the structure shown in T-1 above.

[0113] <Synthesis of Compound T-2> Compound T-2 was synthesized according to the synthesis method of BOPPA described in Patent Document 2.

[0114] [Preparation of Metal Ion-Containing Aqueous Solution] <Preparation of Metal Ion-Containing Aqueous Solution Containing One Type of Metal Ion> 190.8 g of cobalt (II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to a 1 L volumetric flask, made up to scale with ultrapure water, and then stirred and dissolved at 40° C. to prepare a metal ion-containing aqueous solution (W1) having a metal ion concentration of 40,000 ppm. Similarly, 191.4 g of nickel (II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to a 1 L volumetric flask, made up to scale with ultrapure water, and then stirred and dissolved at 40° C. to prepare a metal ion-containing aqueous solution (W2) having a metal ion concentration of 40,000 ppm.

[0115] <Preparation of metal ion-containing aqueous solution containing two types of metal ions> 47.6 g of cobalt (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 47.8 g of nickel (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were added to a 1 L volumetric flask, and the mixture was made up to volume with ultrapure water. The mixture was then stirred at 40°C to dissolve the metal ion, thereby preparing a metal ion-containing aqueous solution (W3) having a concentration of each metal ion of 10,000 ppm.

[0116] The pH of the prepared metal ion-containing aqueous solutions (W1) to (W3) was measured using a pH meter (SK-620pHII, manufactured by Satotec Co., Ltd.) and the results are shown below. Metal ion-containing aqueous solution (W1): 6.7 Metal ion-containing aqueous solution (W2): 6.7 Metal ion-containing aqueous solution (W3): 6.5

[0117] [Preparation of Oil Phase Containing Metal Extractant Composition] Synthesized or prepared acidic extractant (B) and compound (C) were added to a 100 mL volumetric flask and diluted with kerosene (Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature. Oil phases (Y1) to (Y10) and (Yc1) to (Yc5) containing the acidic extractant (B) and compound (C) shown in Tables 1 and 2 at the following concentrations and molar ratios shown in the tables were prepared. In oil phases (Y1) to (Y6) and (Y10), the content (concentration) of acidic extractant (B) in the oil phase was 1400 mM, and the content of compound (C) in the oil phase was 14 mM. In oil phase (Y7), the content of acidic extractant (B) in the oil phase was 1400 mM, and the content of compound (C) in the oil phase was 140 mM. In the oil phase (Y8), the content of the acidic extractant (B) in the oil phase was 1400 mM, and the content of the compound (C) in the oil phase was 420 mM. In the oil phase (Y9), the content of the acidic extractant (B) in the oil phase was 1400 mM, and the content of the compound (C) in the oil phase was 14 mM. In the oil phases (Yc1) to (Yc5), the content of the acidic extractant (B) in the oil phase was 1400 mM. In the oil phases (Yc2) to (Yc5), the content of the compound (C) in the oil phase was 14 mM. In addition, the molar ratio of the compound (C) to the acidic extractant (B) in each oil phase ([compound (C) / acidic extractant (B)]) was as shown in the "molar ratio" column of Tables 1 and 2.

[0118] [Example 1] <Example 1-1> In Example 1-1, a metal ion-containing aqueous solution (W1) containing a large amount of one type of metal ion as the aqueous phase was mixed with an oil phase (Y1), and the mixing speed of the aqueous phase and the oil phase, the amount of extracted metal ions, and the extraction rate were evaluated. In this example, the pH at the time of mixing of the aqueous phase and the oil phase was set to the pH shown in the "pH at mixing" column in Table 1, and the amount of pH adjuster (10 M aqueous sodium hydroxide solution) required to adjust to that pH value (0.7 mL) was determined. 10 mL of the oil phase (Y1) was added to 10 mL of the prepared metal ion-containing aqueous solution (W1) in a 30 mL vial, and the mixture was stirred at 25 ° C. for 30 minutes (rotation speed: 150 rpm) using a stirrer tip (diameter 6 mm, length 20 mm) (premixing). The amount of acidic extractant E-1 mixed relative to the Co ion content (unit: equivalents) at this time was 2.1. Thereafter, the calculated amount of 10 M aqueous sodium hydroxide solution was added all at once to the preliminary mixture (combined liquid), and the mixture was stirred (at 150 rpm) until the pH of the mixture reached the value shown in the "pH at mixing" column in Table 1, and then allowed to stand at the same temperature for 1 hour. After confirming that the oil and aqueous phases had separated into two, the aqueous phase was separated and separated to separate and recover the metal ions. The pH of the mixture was measured using a pH meter (SK-620pHII, manufactured by Satotec). The metal ions extracted in Example 1-1 are shown in the "Extracted metal ions" column in Table 1.

[0119] Examples 1-2 to 1-11 and Comparative Examples 1-1 to 1-5 Separation and recovery of metal ions in Examples 1-2 to 1-11 and Comparative Examples 1-1 to 1-5 were carried out in the same manner as in Example 1-1, except that in Example 1-1, the metal ion-containing aqueous solution (aqueous phase) and the oil phase were changed to the combinations shown in Table 1, and a 10 M aqueous sodium hydroxide solution in an amount necessary to adjust the pH at the time of mixing the aqueous phase and the oil phase to the value shown in the "pH at mixing" column in Table 1 was added all at once, mixed, and allowed to stand.

[0120] <Evaluation 1-1: Evaluation of Mixing Speed> In each of the above Examples and Comparative Examples, the mixing speed was defined and evaluated as the stirring time required from immediately after adding a predetermined amount of pH adjuster all at once until the pH of the mixed solution reached the value shown in the "pH at mixing" column in Table 1. The results are shown in Table 1. In this evaluation, a rating of "D" or higher was considered to be acceptable. The stirring times for Comparative Examples 1-1 to 1-5 were 80 minutes, 60 minutes, 60 minutes, 75 minutes, and 65 minutes, respectively. - Evaluation Criteria - A: Stirring time is less than 10 minutes B: Stirring time is 10 minutes or more but less than 20 minutes C: Stirring time is 20 minutes or more but less than 25 minutes D: Stirring time is 25 minutes or more but less than 30 minutes E: Stirring time is 30 minutes or more

[0121] <Evaluation 1-2: Evaluation of Extraction Amount and Extraction Rate> In each Example and Comparative Example, the dissolved metal ion content of each aqueous phase used (metal ion-containing aqueous solutions (W1) and (W2)) and each aqueous phase after extraction was quantified using an inductively coupled plasma optical emission spectroscopy (ICP-OES) device (Optima 7300D (trade name), manufactured by PerkinElmer). The measured values ​​of the dissolved metal ion content of each aqueous phase used in the Examples and Comparative Examples are shown in the column "Metal ion concentration (ppm) in aqueous phase before extraction" in Table 1, and the measured values ​​of the dissolved metal ion content of each aqueous phase after mixing in each Example and Comparative Example are shown in the column "Metal ion concentration (ppm) in aqueous phase after extraction" in Table 1. The amount of extraction (difference, unit: ppm) of each metal ion was calculated using the metal ion concentration CI in the aqueous phase before extraction and the metal ion concentration CA in the aqueous phase after mixing according to the following formula, and the extraction rate (unit: %) of each metal ion was also calculated using the following formula. The results are shown in the "Extracted Amount" and "Extraction Rate" columns of Table 1, respectively. Extracted Amount (ppm) = (CI - CA) Extraction Rate (%) = [(CI - CA) / CI] x 100 In this test, the larger the extraction amount and extraction rate, the greater the amount of metal ion extracted into the oil phase, and the greater the mass of metal ion extracted into the oil phase per unit volume. Furthermore, the larger the extraction amount, the greater the amount of processing that can be performed in a single extraction operation. In this test, an extraction amount of 32,000 ppm or more is considered acceptable, and an extraction rate of 80% or more is considered acceptable.

[0122]

[0123] [Example 2] <Example 2-1> In Example 2-1, a metal ion-containing aqueous solution (W3) containing two types of metal ions as the aqueous phase and an oil phase (Y1) were mixed, and the mixing rate of the aqueous phase and the oil phase was evaluated. In this example, the pH at the time of mixing of the aqueous phase and the oil phase was set to the pH shown in the "pH at mixing" column in Table 2, and the amount of pH adjuster (10 M aqueous sodium hydroxide solution) required to adjust to that pH value (0.2 mL) was determined. 10 mL of the oil phase (Y1) was added to 10 mL of the prepared metal ion-containing aqueous solution (W3) in a 30 mL vial, and the mixture was stirred (rotation speed: 150 rpm) at 25 °C for 30 minutes using a stirrer tip (diameter 6 mm, length 20 mm) (pre-mixing). At this time, the amount (unit: equivalent) of acidic extractant E-1 mixed relative to the total content of coordinating metal ions (synonymous with extracted metal ions, Co and Ni in Example 2-1) was 4.1. Thereafter, the calculated amount of 10 M aqueous sodium hydroxide solution was added all at once to the preliminary mixture (combined liquid), and the mixture was stirred (at 150 rpm) until the pH of the mixture reached the value shown in the "pH at mixing" column in Table 2, after which it was allowed to stand at the same temperature for 1 hour. After confirming that the oil and aqueous phases had separated into two, the aqueous phase was separated and separated for separation and recovery of metal ions. The pH of the mixture was measured using a pH meter (SK-620pHII, manufactured by Satotec Co., Ltd.).

[0124] Examples 2-2 to 2-11 (2-7 is a missing number) and Comparative Examples 2-1 to 2-5 Separation and recovery of metal ions in Examples 2-2 to 2-11 and Comparative Examples 2-1 to 2-5 were carried out in the same manner as in Example 2-1, except that in Example 2-1, the metal ion-containing aqueous solution (aqueous phase) and the oil phase were changed to the combination shown in Table 2, and the amount of 10 M sodium hydroxide aqueous solution required to adjust the pH when the aqueous phase and the oil phase were mixed to the value shown in the "pH at mixing" column in Table 2 was added all at once, mixed, and allowed to stand.

[0125] The metal ions extracted in each Example and Comparative Example are shown in the "Extracted metal ions" column of Table 2. Furthermore, in each Example and Comparative Example, the dissolved metal ion content of each aqueous phase (metal ion-containing aqueous solution (W3)) used and each aqueous phase after extraction was quantified using an inductively coupled plasma optical emission spectroscopy (ICP-OES) analyzer (Optima 7300D (trade name), manufactured by PerkinElmer). The measured values ​​of the dissolved metal ion content of each aqueous phase used in the Examples and Comparative Examples are shown in the "Metal ion concentration (ppm) in aqueous phase before extraction" column of Table 2, and the measured values ​​of the dissolved metal ion content of each aqueous phase after mixing in each Example and Comparative Example are shown in the "Metal ion concentration (ppm) in aqueous phase after extraction" column of Table 2.

[0126] <Evaluation 2-1: Evaluation of Mixing Speed> In Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-5, the mixing speed was evaluated in the same manner as in Evaluation 1-1 of Example 1. The results are shown in Table 2. In this evaluation, a rating of "D" or higher was considered to be acceptable. The mixing times in Comparative Examples 2-1 to 2-5 were 65 minutes, 55 minutes, 55 minutes, 65 minutes, and 60 minutes, respectively.

[0127]

[0128] [Example 3] Metal ions were separated and recovered in the same manner as in Examples 1 and 2, except that the oil phase containing the acidic extractant (B) and the compound (C) in Examples 1 and 2 was replaced with the acidic extractant (B) and the compound (C) separately. That is, instead of the oil phases used in Examples 1 and 2, an oil phase containing the same acidic extractant (B) as the acidic extractant (B) contained in the oil phase and the compound (C) alone were separately added to the aqueous phase in the same amounts as in Examples 1 and 2, and premixed. Separation and recovery of metal ions was carried out in the same manner as in Examples 1 and 2. As a result, similar results to those in Examples 1 and 2 were obtained.

[0129] The results shown in Example 1 (Table 1), Example 2 (Table 2), and Example 3 reveal the following. In the separation and recovery of metal ions by wet extraction, Comparative Examples 2-1 to 2-5, which used oil phases (Yc1) to (Yc5) that did not contain at least one of the acidic extractant (B) and compound (C) specified in the present invention, were all able to extract two types of metal ions present in the metal ion-containing aqueous solution (W3) into the oil phase, as shown in Table 2, but the mixing speed was slow. Furthermore, Comparative Examples 1-1 to 1-5, which used the same oil phase, all had slow mixing speeds and insufficient extraction amounts and extraction rates, as shown in Table 1. Therefore, it was found that the separation and recovery methods of the comparative examples using oil phases (Yc1) to (Yc5) were not suitable for increasing the processing volume.

[0130] In contrast, in Examples 2-1 to 2-11, which used the metal extractant composition of the present invention (oil phases (Y1) to (Y10)) containing the acidic extractant (B) and the compound (C), as shown in Table 2, the mixing rate was fast, and two types of metal ions present in the metal ion-containing aqueous solution (W3) could be extracted into the oil phase, and one type of metal ion (Co ion) could be selectively separated and recovered. The selectivity ratio in Examples 2-1 to 2-11 exceeded at least 3.1. Furthermore, in Examples 1-1 to 1-11, which used the same oil phase, as shown in Table 1, the mixing rate was fast, the aqueous phase and the oil phase were mixed quickly, the solubility of the metal complex was increased, and even when the treatment amount (metal ion concentration in the aqueous phase) was increased, the metal ions could be extracted at a high extraction rate and a high extraction rate. In particular, in Examples 1-4 to 1-9, metal ions could be extracted with an extraction rate of 90% or more and a large extraction amount of 36,500 ppm, while in Examples 1-5 to 1-9, an extraction rate of 100% and an extraction amount of 40,000 ppm were achieved. Thus, when the metal extractant composition of the present invention is used in a wet extraction method, it is possible to increase the mixing speed of the aqueous phase and the oil phase, and further increase the solubility of the metal complex in the oil phase, thereby increasing the processing amount in the wet extraction method. Furthermore, even when the processing amount is increased, specific metal ions present in the aqueous phase can be extracted into the oil phase with a high extraction rate (high recovery rate), preferably with high selectivity, in a short mixing time. Furthermore, it can be seen that a specific metal ion can be separated and recovered from two or more metal ions belonging to different groups that have similar physical and chemical behaviors, particularly one metal ion belonging to Groups 9 and 10 that can be recovered from waste LiB, with a high extraction rate and preferably with high selectivity.

[0131] The above results demonstrate that stripping the oil phase obtained in each of the above examples using conventional methods and conditions allows for the simple and highly productive separation and recovery of a specific metal ion from among multiple metal ions present in large quantities in the aqueous phase, with a high recovery rate and preferably high selectivity. However, in technologies for recovering a specific metal ion from an aqueous phase containing multiple metal ions, it is generally difficult to recover the specific metal ion with a high extraction rate and selectivity. Maintaining high selectivity results in a decrease in extraction rate, requiring multiple separation and recovery procedures to achieve a desired extraction rate. In contrast, the present invention allows for the simple and highly productive extraction of a large amount of one of two heterogeneous metal ions from the aqueous phase with a high recovery rate and preferably high selectivity. Therefore, in light of the above-mentioned circumstances, the present invention is of great technical significance in that it allows for the recovery of one metal ion from the obtained oil phase by a stripping step or the like, with a simple and reduced number of steps, and with high productivity due to an increased treatment volume and a shortened treatment time, while improving the recovery amount and recovery rate, preferably even higher selectivity, of the metal ion.

[0132] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0133] This application claims priority based on Japanese Patent Application No. 2024-148548, filed on August 30, 2024, the contents of which are incorporated herein by reference as part of the present specification.

Claims

1. A metal extractant composition for extracting metal ions (A) present in an aqueous phase into an oil phase, comprising an acidic extractant (B) represented by the following formula (I), and a compound (C) having at least one hydrocarbon group and at least one functional group included in the following functional group group (c), wherein the total number of carbon atoms constituting the at least one hydrocarbon group is 14 or more. In formula (I), R １ and R ２ each represents an aliphatic hydrocarbon group, and R １ and R ２ At least one of X represents an aliphatic hydrocarbon group having 12 or more carbon atoms. １ represents a hydroxy group or a sulfanyl group. １ represents an oxygen atom or a sulfur atom. １ and Z ２ represents a single bond on one side and an oxygen atom or a sulfur atom on the other side. <Functional Group (c)> Hydroxy group, amino group, sulfanyl group, imino group, ether bond, ester bond, phosphate ester bond, phosphonate ester bond, phosphinate ester bond, amide bond, urethane bond, urea bond 2. The above R １ and R ２ 2. The metal extractant composition according to claim 1, wherein at least one of the groups is an aliphatic hydrocarbon group having 16 or more carbon atoms.

3. The above R １ and R ２ and each of the groups is an aliphatic hydrocarbon group having a branched structure.

4. The metal extractant composition according to claim 1, wherein the compound (C) is represented by the following formula (II): In formula (II), R ３ , R ４ and R ５ each represents a hydrocarbon group, and R ３ ~R ５ At least one of Y represents a hydrocarbon group having 8 or more carbon atoms. ２ represents an oxygen atom or a sulfur atom. ３ , Z ４ and Z ５ each represents a single bond, an oxygen atom, or a sulfur atom; Z ３ ~Z ５ At least one of is a single bond.

5. The above R ３ , R ４ and R ５ The metal extractant composition according to claim 4, wherein each of the groups is an aliphatic hydrocarbon group.

6. The above R ３ , R ４ and R ５ 5. The metal extractant composition according to claim 4, wherein at least one of the groups is a hydrocarbon group having 16 or more carbon atoms.

7. The above R ３ , R ４ and R ５ 5. The metal extractant composition according to claim 4, wherein two of the groups are hydrocarbon groups having 16 or more carbon atoms.

8. The metal extractant composition according to claim 1, wherein the molar ratio of compound (C) to acidic extractant (B) is 10.0 to 0.0001.

9. The metal extractant composition according to claim 1, wherein the metal ions (A) extracted into the oil phase are ions of two metal elements belonging to different groups among ions of metal elements belonging to groups 8 to 11 of the periodic table of the elements.

10. A method for separating and recovering metal ions, which comprises mixing an aqueous phase containing multiple types of metal ions with an oil phase containing the metal extractant composition according to any one of claims 1 to 9.

11. A method for separating and recovering metal ions, comprising mixing an aqueous phase containing multiple types of metal ions with an oil phase containing the acidic extractant (B) described in claim 1 in the presence of the compound (C) described in claim 1.

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