Metal extractant, separation recovery method of metal ions using metal extractant, and compound

Abstract

Provided are a metal extractant and a compound that extract metal ions present in a water phase to an oil phase, in which the metal extractant and the compound have a structure represented by Formula (I) and do not include a nitrogen atom; and a separation recovery method of metal ions using the metal extractant.In Formula (I), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent, X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom, and a benzene ring in the formula may form a fused ring.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of PCT International Application No. PCT / JP2024 / 009754 filed on Mar. 13, 2024, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-050477 filed in Japan on Mar. 27, 2023. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to a metal extractant that extracts metal ions present in a water phase to an oil phase, a separation recovery method of metal ions using this metal extractant, and a compound.2. Description of the Related Art

[0003] Valuable metals such as noble metals or rare earth metals are essential elements for precision equipment, and stable supply and acquisition of the valuable metals with high purity is a big challenge. The valuable metals are typically mined as a mixture of plural kinds of metals. Therefore, the desired valuable metals need to be isolated and purified (high purity) from the mined mixture. In addition, the valuable metals that can be mined from mines are also limited, and thus a technique of recovering the valuable metals from industrial waste irrespective of mining is also important. In particular, along with the spread of electric vehicles, the amount of lithium ion batteries (LiB) wasted has been increasing every year. In LiB, a positive electrode active material including a metal element such as cobalt or nickel is used, and a significant increase in the demand for cobalt or nickel is also expected. In order to deal with the increase in the demand for valuable metals along with the trend, not only an increase in the amount of mining but also establishment of a technique of recycling waste LiB into a metal are desired.

[0004] As the isolated purification method of a desired valuable metal from the mined mixture and the method of recycling waste into a metal, a wet extraction method (solvent extraction method) is used. In the wet extraction method, in a case where an aqueous solution (water phase) including ions of a metal element (simply referred to as metal ions) and an organic phase including a metal extractant are brought into contact with each other, mixed, and left to stand to separate the two phases, the metal ions to which the metal extractant is coordinated are moved (extracted) to the organic phase. By extracting the organic phase, stripping the metal ions, and optionally purifying the metal ions, a desired metal can be isolated and purified, and the waste can be recycled as a (high-purity) metal.

[0005] As the metal extractant used for the wet extraction method, for example, JP2013-133537A describes an extractant including a mixture of a quaternary amine such as methyltri-n-octylammonium chloride and a phenol such as nonylphenol. In addition, JP2016-194105A describes a second mixed extractant including a phosphate-based extractant such as di-2-ethylhexyl phosphate and an oxime-based extractant such as 5-nonylsalicylaldoxime.SUMMARY OF THE INVENTION

[0006] Regarding the metal extractants described in JP2013-133537A and JP2016-194105A, JP2013-133537A and JP2016-194105A describe that, by using two kinds of specific extractants in combination for the wet extraction method, specific metal ions present in a water phase can be extracted and recovered to an oil phase. However, in a case where the two kinds of specific extractants are individually used for the wet extraction method without being used in combination, the selectivity (separability) of metal ions to be extracted is not sufficient, and a metal extractant having high initial selectivity where specific metal ions can be selectively separated and extracted from the water phase is desired for the wet extraction method.

[0007] Incidentally, the wet extraction method is normally performed under relatively mild conditions regarding extraction conditions (contact conditions between the water phase and the oil phase) such as a temperature or a pressure. From the viewpoint of reducing recycling costs, in general, the metal extractant is repeatedly used. However, in the wet extraction method, in a case where the water phase and the oil phase are brought into contact with each other, or in a case where metal ions extracted to the oil phase are stripped and isolated, a mixed solution of the water phase and the oil phase is set to a predetermined pH to be relatively strongly acidic or basic (for example, refer to JP2013-133537A and JP2016-194105A). In a case where the wet extraction method set to the pH conditions is repeatedly performed, even with a metal extractant having high selectivity for metal ions, the amount of metal ions extracted from the water phase to the oil phase gradually decreases. Therefore, a metal extractant having high durability where a recovery rate (extraction rate) of metal ions is maintained even in a case where the wet extraction method is repeatedly performed is desired.

[0008] However, JP2013-133537A and JP2016-194105A consider neither further improvement of the selectivity of metal ions nor suppression of a decrease in the recovery rate of metal ions during the repeated use.

[0009] An object of the present invention is to provide: a metal extractant that can extract specific metal ions present in a water phase to an oil phase with high selectivity and also has high durability; and a separation recovery method of metal ions using this metal extractant. In addition, an object of the present invention is to provide a compound that can be a metal extractant having the above-described excellent characteristics.

[0010] The present inventors conducted a thorough investigation on the metal extractant used for the wet extraction method and found that, by adopting a compound where a phenolic structure (structure represented by “benzene ring —OR1” in Formula (I) described below) is adopted, a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom is introduced into the benzene ring, and a nitrogen atom is not included, in a case where this compound is used as a metal extractant for a wet extraction method, a reduction in the amount of metal ions extracted can be suppressed for a long period of time while maintaining high selectivity (separability) of the metal ions.

[0011] The present invention has been completed as a result of repeated investigation based on the above findings.

[0012] That is, the above-described objects have been achieved by the following means.

[0013] <1> A metal extractant that extracts metal ions present in a water phase to an oil phase,

[0014] in which the metal extractant has a structure represented by Formula (I) and does not include a nitrogen atom,in Formula (I), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0016] X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom, and

[0017] a benzene ring in Formula (I) may form a fused ring.

[0018] <2> The metal extractant according to <1>,

[0019] in which the metal extractant includes a functional group selected from the following group G of functional groups,<Group G of Functional Groups>a carboxy group, a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group.

[0021] <3> The metal extractant according to <2>,

[0022] in which the functional group selected from the group G of functional groups is a phosphate group or a phosphonate group.

[0023] <4> The metal extractant according to any one of <1> to <3>,

[0024] in which the metal extractant has a hydrocarbon group having 9 or more carbon atoms.

[0025] <5> The metal extractant according to any one of <1> to <4>,

[0026] in which the metal extractant is represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0028] L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,

[0029] R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, and

[0030] a benzene ring in Formula (II) may form a fused ring.

[0031] <6> The metal extractant according to any one of <1> to <5>,

[0032] in which the metal ions are ions of a metal element belonging to Group 1 to Group 14 in a periodic table.

[0033] <7> The metal extractant according to any one of <1> to <6>,

[0034] in which the metal extractant is used for extraction and separation of two or more kinds of metal ions belonging to different groups in a periodic table among the metal ions.

[0035] <8> A separation recovery method of metal ions, the separation recovery method including:

[0036] mixing a water phase including plural kinds of metal ions with an oil phase including the metal extractant according to any one of <1> to <7>.

[0037] <9> A compound represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0039] L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,

[0040] R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, and

[0041] a benzene ring in Formula (II) may form a fused ring.

[0042] An object of the present invention is to provide: a metal extractant that can extract specific metal ions present in a water phase to an oil phase with high selectivity and also has high durability; and a separation recovery method of metal ions using this metal extractant. In addition, an object of the present invention is to provide a compound that can be a metal extractant having the above-described excellent characteristics.

[0043] The above-described and other characteristics and advantageous effects of the present invention will be clarified from the following description appropriately with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 is a 1H-NMR chart showing a compound E-1 synthesized in Example.DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] In the present invention, in a case where a numerical range is shown to describe a content, physical properties, or the like of a component, any upper limit value and any lower limit value can be appropriately combined to obtain a specific numerical range in a case where an upper limit value and a lower limit value of the numerical range are described separately. In a case where a plurality of numerical ranges represented by “-” are set and described, the upper limit value and the lower limit value which form each of the numerical ranges are not limited to a specific combination described before and after “to” as a specific numerical range and can be set to a numerical range obtained by appropriately combining the upper limit value and the lower limit value of each numerical range. In the present invention, numerical ranges represented by “to” include numerical values before and after “to” as lower limit values and upper limit values.

[0046] In the present invention, the expression of a compound (for example, in a case where a compound is represented by an expression with “compound” added to the end) refers to not only the compound itself but also a salt or an ion thereof. In addition, this expression also refers to a derivative obtained by modifying a part of the compound, for example, by introducing a substituent into the compound within a range where the effects of the present invention do not deteriorate.

[0047] A substituent, a linking group, or the like (hereinafter, referred to as “substituent or the like”) that is not specified in the present invention regarding whether to be substituted or unsubstituted may have an appropriate substituent. Accordingly, even in a case where a YYY group is simply described in the present invention, this YYY group includes not only an aspect not having a substituent but also an aspect having a substituent. The same shall be applied to a compound which is not specified in the present specification regarding whether to be substituted or unsubstituted. Examples of a preferable substituent include groups selected from the substituent GZ described below.

[0048] In the present invention, in a case where a plurality of substituents or the like represented by a specific reference numeral are present or a plurality of substituents or the like are simultaneously or alternatively defined, the respective substituents or the like may be the same as or different from each other. In addition, unless specified otherwise, in a case where a plurality of substituents or the like are adjacent to each other, the substituents may be linked or fused to each other to form a ring.

[0049] In the present specification, “metal elements belonging to different groups in the periodic table of elements” in the specific metal ion group will be referred to as “different-group metal elements”, and particularly “different-group metal elements of the same period in the periodic table” will also be referred to as “same-period different-group metal elements”. In addition, “ions of the different-group metal elements” and “ions of the same-period different-group metal elements” will also be referred to as “different-group metal ions” and “same-period different-group metal ions”, respectively.

[0050] In the present invention, unless specified otherwise, “ppm” representing a content or the like is based on mass and represents “mass ppm”.[Metal Extractant]

[0051] A metal extractant according to an embodiment of the present invention includes a compound represented by Formula (I), and may include appropriately other components within a range where the effects of the present invention do not deteriorate. In addition, the metal extractant according to the embodiment of the present invention may include other compounds (other metal extractants) that function as extractants of metal ions other than the compound represented by Formula (I). However, the compound represented by Formula (I) exhibits the above-described excellent characteristics as the metal extractant as described below. Therefore, it is preferable that the metal extractant according to the embodiment of the present invention includes the compound represented by Formula (I) alone. In the present invention, the meaning of the metal extractant according to the embodiment of the present invention including the compound represented by Formula (I) alone includes an aspect where only the compound represented by Formula (I) is included and an aspect where a content of the other metal extractants with respect to a total mass including the compound represented by Formula (I) is 10% by mass or less.

[0052] In addition, each of forms of the metal extractant according to the embodiment of the present invention and the compound represented by Formula (I) is not particularly limited, and may be a solid such as powder or a granule or may be a liquid (solution) in which the substance is dissolved in an organic solvent.

[0053] The metal extractant according to the embodiment of the present invention has a function of extracting metal ions present in a water phase to an oil phase, and can be suitably used particularly for a wet extraction method. By using the metal extractant according to the embodiment of the present invention in the wet extraction method, even in a case where the compound represented by Formula (I) is included alone and even in a case where the metal extractant is used for a long period of time, specific metal ions present in the water phase can be extracted to the oil phase with high selectivity and high recovery rate. In particular, the metal extractant can extract specific metal ions from plural kinds of metal ions present in the water phase to the oil phase with high selectivity and high recovery rate.

[0054] In the present invention, as the metal ions that can be extracted to the oil phase among plural kinds of metal ions present in the water phase, ideally, one kind of specific metal ions can be used. However, two or more kinds of metal ions can also be used. Even in a case where two or more kinds of metal ions are included, one kind of metal ions among the two or more kinds of metal ions can be extracted (separated and recovered) with higher selectivity and with higher recovery rate than those of the other metal ions (including metal ions extracted to the oil phase). For example, while extracting, as ions of valuable metal elements, two or more kinds of different-group metal ions, for example, two or more kinds of metal ions belonging to Group 1 to Group 14 in the periodic table, desirably two or more kinds of different-group metal ions, and particularly desirably cobalt ions and nickel ions that are the same-period different-group metal ions to the oil phase, one kind of metal ions among the two or more kinds of metal ions can be extracted to the oil phase with high selectivity and high recovery rate.

[0055] Since the same-period different-group metal ions have similar physical behaviors and similar chemical behaviors, it is not easy to separate and recover any one kind of metal ions among the same-period different-group metal ions with high selectivity. However, in the present invention where the compound represented by Formula (I) is used as the metal extractant, while extracting the same-period different-group metal ions having similar physical behaviors and similar chemical behaviors, in particular, metal ions belonging to Group 9 (in particular, cobalt ions) and metal ions belonging to Group 10 (in particular, nickel ions) that are required along with the recent rapid spread of lithium ion batteries, one kind of metal ions among the two or more kinds of metal ions can be recovered with high selectivity and high recovery rate. Therefore, the present invention can largely contribute to further spread of electric vehicles and construction of a sustainable society.

[0056] In addition, in the present invention, being capable of extracting metal ions with high recovery rate with high selectivity represents that only one specific kind of metal ions among plural kinds of metal ions present in the water phase can be extracted. In addition, in a case where two or more kinds of metal ions are extracted to the oil phase, being capable of extracting metal ions with high selectivity represents that specific metal ions can be extracted and separated from the other metal ions such that, among the two or more kinds of extracted metal ions, a ratio of the amount of specific metal ions (typically one kind) to be extracted to the total amount of the other metal ions extracted [(the amount of the specific metal ions extracted) / (the total amount of the other metal ions extracted) is 1.5 or more (separability, selection ratio). The ratio (selection ratio) is preferably 3.0 or more, more preferably 4.5 or more, and particularly preferably 8.0 or more. The upper limit thereof is not particularly limited, but may be, for example, 30.

[0057] In the present invention, the above-described ratio (selection ratio) refers to a ratio that is achieved in a case where the metal extractant according to the embodiment of the present invention is initially used for the wet extraction method. On the other hand, in the metal extractant according to the embodiment of the present invention, high selectivity can be maintained even in a case where the metal extractant is repeatedly used for the wet extraction method and is continuously used for a long period of time. For example, in a case where a metal extractant is used 10 times for the wet extraction method (separation extraction operation) in Examples described below, a selection ratio is preferably 1.5 or more and more preferably 4.5 or more.

[0058] In addition, in the present invention, being capable of extracting metal ions with high recovery rate represents that the metal ions can be extracted such that, regarding metal ions (specific metal ions to be extracted) extracted in the maximum amount among the two or more kinds of extracted metal ions, a ratio of the amount of the metal ion extracted to the oil phase to the content of the metal ions (before the extraction) in the water phase [(the amount of the metal ions extracted to the oil phase) / (the content of the metal ions in the water phase] is 60% or more. The above-described ratio (recovery rate) is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more. The upper limit is not particularly limited and is ideally the total amount (100%) of the metal ions present in the water phase. For example, the upper limit is preferably 99% or less.

[0059] In the present invention, the above-described ratio (recovery rate) refers to a ratio that is achieved in a case where the metal extractant according to the embodiment of the present invention is initially used for the wet extraction method. On the other hand, the metal extractant according to the embodiment of the present invention has excellent durability. Therefore, high recovery rate can be maintained even in a case where the metal extractant is repeatedly used for the wet extraction method and is continuously used for a long period of time. For example, in a case where a metal extractant is used 10 times for the wet extraction method (separation extraction operation) in Examples described below, a recovery rate is preferably 70% or more and more preferably 85% or more.(Compound Represented by Formula (I))

[0060] The metal extractant according to the embodiment of the present invention consists of a compound having a (chemical) structure represented by Formula (I) and does not include a nitrogen atom in the structure (molecule) (also referred to as the compound according to the embodiment of the present invention). This compound has excellent characteristics as the metal extractant as described above.

[0061] The compound according to the embodiment of the present invention does not include a nitrogen atom. In the present invention, the compound not having a nitrogen atom represents that an atom group forming the compound does not include a nitrogen atom, for example, any of the phenolic structure or the substituent does not include a nitrogen atom. Examples of the substituent including a nitrogen atom include an amino group, an imino group (—NRN1—, —C═NRN1), and a group consisting of a nitrogen-containing aromatic ring or a nitrogen-containing aliphatic ring. RN1 in the imino group represents a hydrogen atom or a substituent. The substituent is, for example, a group selected from a substituent GZ described below, and typical examples thereof include an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and a hydroxy group.

[0062] The compound according to the embodiment of the present invention having high selectivity and high durability can be used, for example, repeatedly and continuously over a long period of time as a metal extractant for the wet extraction method. Any of the number of times (number of times of use) the compound according to the embodiment of the present invention can be repeatedly used for the wet extraction method or a period of time in which the compound according to the embodiment of the present invention can be continuously used for the wet extraction method cannot be uniquely determined depending on various conditions in the wet extraction method, stripping conditions of metal ions, purification conditions for appropriate purification during reuse, and the like. For example, the number of times of use in the batch type wet extraction method can be 5 or more and is preferably 10 or more. The continuous use time in the continuous type wet extraction method can be 12 hours or longer and is preferably 24 hours or longer. On the other hand, the upper limits of the number of times of use and the continuous use time can be appropriately determined depending on not only the above-described conditions but also selection ratio and recovery rate. For example, the number of times of use can be 100 or less, and from the viewpoint that a high selection ratio and a high recovery rate in the above-described ranges can be achieved, is preferably 50 or less and more preferably 30 or less. In addition, the continuous use time can be 168 hours or shorter, and from the viewpoint that a high selection ratio and a high recovery rate in the above-described ranges can be achieved, is preferably 48 hours or shorter and more preferably 36 hours or shorter.

[0063] In the compound represented by Formula (I), a benzene ring in Formula (I) may form a fused ring. Examples of the compound that form a fused ring include a compound represented by Formula (IC). In Formula (IC), a represents an atomic group (not including a nitrogen atom) that forms a fused ring with the benzene ring in Formula (IC).

[0064] The atomic group that can be used as a only needs to be an atomic group that can form a fused ring with the benzene ring in Formula (IC), and examples thereof include an atomic group that can form a fused ring not including a nitrogen atom. The ring that can be formed by a with the benzene ring (two carbon atoms) in Formula (IC) is not particularly limited, and may be an aliphatic ring or an aromatic ring or may be a hydrocarbon ring or a heterocycle (excluding a ring including a nitrogen atom). Further, the formed ring itself may be a monocycle or a polycycle. Specific examples of the ring that is formed by a include a cycloalkyl group, an aryl group, and a heterocyclic group in the substituent GZ described below.

[0065] In the present invention, a compound not including a, that is, the compound represented by Formula (I) is preferable.

[0066] In Formulae (I) and (IC), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent.

[0067] In the present invention, as a preferable first aspect of the atom or the like that can be used as R1, a hydrogen atom or a metal atom is preferable, and a hydrogen atom is more preferable. On the other hand, as a preferable second aspect of the atom or the like that can be used as R1, a monovalent substituent is preferable.

[0068] As the metal atom that can be used as R1, an atom that can form a salt of a phenolic hydroxyl group may be used, and a monovalent metal atom is preferable. The metal atom that can be used as R1 is typically present as a metal ion. Examples of the metal atom include a metal atom belonging to Group 1 or Group 2 in the periodic table. Among these, a metal atom belonging to Group 1 is preferable, and lithium, sodium, or potassium is more preferable.

[0069] The monovalent substituent that can be used as R1 is not particularly limited, a substituent not including a nitrogen atom is selected, and examples thereof include a group (a substituent not including a nitrogen atom) selected from the substituent GZ described below. As the monovalent substituent, for example, a hydrocarbon group such as an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an aralkyl group, a heterocyclic group is preferable, an alkyl group or an aryl group is more preferable, and an alkyl group is still more preferable.

[0070] Each of the alkyl group and the alkyl group in the alkenyl group, the alkynyl group, and the aralkyl group that can be used as R1 is not particularly limited, may be a straight chain, a branched chain, or a cyclic chain, and is preferably a straight chain.

[0071] The total number of carbon atoms (hereinafter, also simply referred to as the number of carbon atoms) forming the monovalent substituent that can be used as R1, in particular, the hydrocarbon group is not particularly limited irrespective of the description of the substituent GZ described below. The number of carbon atoms in each of the groups is appropriately determined in a range of, for example, 1 to 30. As a preferable first aspect of the number of carbon atoms in the monovalent substituent that can be used as R1, the number of carbon atoms is preferably 1 to 12 (corresponding to a short-chain alkyl group and a medium-chain alkyl group), more preferably 1 to 6 (corresponding to a short-chain alkyl group), and still more preferably 1 to 4 (corresponding to a short-chain alkyl group). As a preferable second aspect of the number of carbon atoms in the monovalent substituent that can be used as R1, the number of carbon atoms is preferably 9 to 20 (corresponding to a medium-chain alkyl group and a long-chain alkyl group), more preferably 10 to 18, and still more preferably 12 to 16.

[0072] In Formulae (I) and (IC), X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom. This substituent does not typically include a nitrogen atom.

[0073] A preferable first aspect of the monovalent substituent that can be used as X is an aspect where the heteroatom is directly bonded to the benzene ring in Formula (I) or Formula (IC). In this aspect, the heteroatom in the monovalent substituent is preferably a sulfur atom or a phosphorus atom and can also further include an oxygen atom. A preferable second aspect of the monovalent substituent that can be used as X is an aspect where the heteroatom is not directly bonded to the benzene ring in Formula (I) or Formula (IC). In this aspect, the heteroatom in the monovalent substituent is preferably an oxygen atom. In the substituent of the second aspect, the linking portion such as the atom or the linking group that is directly bonded to the benzene ring in the Formula (I) or Formula (IC) is not particularly limited. For example, an atom that does not correspond to any of the heteroatom or a nitrogen atom or a linking group (not including a nitrogen atom) where an atom other than the heteroatom is a bonding portion can be used, examples thereof include a group obtained by removing a hydrogen atom from a group selected from the substituent GZ described below. Among these, a carbon atom is preferable.

[0074] The number of kinds of heteroatoms in the monovalent substituent that can be used as X is not particularly limited. For example, the number of kinds can be 1 or more, and is preferably 2 or 3, and more preferably 2. Examples of a combination of two or more kinds of heteroatoms include a combination of a phosphorus atom and an oxygen atom and / or a sulfur atom.

[0075] The number of atoms in the monovalent substituent that can be used as X is not particularly limited, and is appropriately determined depending on the chemical structure of X and the like. For example, the number of heteroatoms can be 1 to 12 and is preferably 2 to 8 and more preferably 2 to 5.

[0076] In the monovalent substituent that can be used as X, the heteroatom may be present at any position of the monovalent substituent, for example, may be present in an atomic chain forming the monovalent substituent or at a terminal thereof. In the present invention, an aspect where one heteroatom is present at a terminal of an atomic chain forming the substituent and is bonded to the benzene ring in Formula (I) or Formula (IC), or an aspect where one heteroatom forms a carbonyl group and is bonded to the benzene ring in Formula (I) or Formula (IC) is preferable.

[0077] The monovalent substituent that can be used as X is not particularly limited as long as it includes the heteroatom, and examples thereof include a substituent that includes the heteroatom and does not include a nitrogen atom among the substituents in the substituent GZ described below. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, each of the functional groups in the group G of functional groups described below is preferable. Examples of a monovalent substituent that can be used as a preferable first aspect among the functional groups in the group G of functional groups include a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group. Examples of a monovalent substituent that can be used as a preferable second aspect include a carboxy group.

[0078] In the compound represented by Formula (I) or Formula (IC), the monovalent substituent is used as X as described above. Therefore, this compound is a non-polymerizable compound having one structure represented by Formula (I) or Formula (IC) where the structure is not a repeating unit. Therefore, the compound represented by Formula (I) or Formula (IC) does not adopt a structure where a plurality of structures represented by Formula (I) or Formula (IC) are linked to each other through X, for example, a linear structure or a cyclic or tubular structure.

[0079] The compound represented by Formula (I) or Formula (IC) can be formed by appropriately combining R1, X, and a in the formula, and is preferably formed by combining preferable examples of the respective reference numerals.

[0080] Note that the compound represented by Formula (I) or Formula (IC) may be a basic compound, but it is preferable that the compound represented by Formula (I) or Formula (IC) corresponds to an acidic compound having at least one active hydrogen atom, that is, an acidic metal extractant from the viewpoint of exhibiting excellent selectivity and high durability as the metal extractant. Examples of the active hydrogen atom in the compound include a hydroxy group (including a phenolic hydroxy group and a hydroxy group bonded to a phosphorus atom or a sulfur atom), a carboxy group and an active hydrogen atom in a sulfanyl group. The active hydrogen atom may be present in any of a ring formed by R1, X, or a, and is preferably present in R1 or X. The number of hydroxy groups present in the compound may be 1 or more, and can be 1 to 4, and is preferably 1 or 2.

[0081] In the compound represented by Formula (I) or Formula (IC), a bonding position of an —OR1 group and X to the benzene ring is not particularly limited. For example, X may be present at any of the 2-position (o-), 3-position (m-), or 4-position (p-) with respect to the OR1 group and preferably at the 2-position from the viewpoint that metal ions can be stably coordinated and the selectivity and the durability of the metal extractant can be improved.

[0082] In the compound represented by Formula (IC), the position where the ring formed by a is bonded to the benzene ring is not particularly limited as long as it does not inhibit the bonding of the —OR1 group and X to the benzene ring. For example, the ring formed by a may be any of the 2- and 3-positions, the 3- and 4-positions, the 4- and 5-positions, or the 5- and 6-positions with respect to the —OR1 group, is preferably bonded to a position away from the —OR1 group and X, and is more preferably bonded to the 4- and 5-positions in a case where X is bonded to the 2-position.

[0083] In the present invention, the compound represented by Formula (I) is preferably a compound represented by Formula (II) from the viewpoints of the selectivity and the durability of the metal extractant. Any of the compound represented by Formula (II) or a compound represented by Formula (IIC) does not include a nitrogen atom as in the compound represented by Formula (I) or Formula (IC).

[0084] In Formula (II), R1 is the same as R1 in Formula (I).

[0085] In addition, in the compound represented by Formula (II), a benzene ring in Formula (II) may form a fused ring as in the compound represented by Formula (I). That is, the compound where the benzene ring in Formula (I) forms a fused ring is represented by, for example, Formula (IIC). In Formula (II), a represents an atomic group (not including a nitrogen atom) that forms a fused ring with the benzene ring in Formula (TIC), and is specifically the same as a in Formula (IC).

[0086] In the present invention, a compound not including a, that is, the compound represented by Formula (II) is preferable.

[0087] In Formula (II) and Formula (IIC), a -L-R2 group is a preferable aspect of the monovalent substituent that can be used as X in Formulae (I) and (IC), and is formed by L and R2.

[0088] Here, L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom. R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms.

[0089] The divalent linking group that can be used as L only needs to be a linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom. This linking group is not particularly limited, and examples thereof include an oxygen atom, a sulfur atom, a carbonyl group, a phosphate linking group (—OP(═O)(ORC)—O— group), a phosphonate linking group (—P(═O)(ORC)—O— group), a phosphinate linking group (—P(═O)RC—O— group) (note that each of the phosphate linking group, the phosphonate linking group, and the phosphinate linking group includes a linking group where at least one oxygen atom in each of the groups is substituted with a sulfur atom), and a group including a combination thereof. Here, RC represents a hydrogen atom or a substituent, and is the same as RC in the group G of functional groups described below.

[0090] In the group including the combination, the number of groups, linking groups, or atoms to be combined is not particularly limited and, for example, can be 2 to 15 and is preferably 2 to 10 and more preferably 2 to 5. In addition, the number of kinds of groups, linking groups, or atoms to be combined is not particularly limited and, for example, can be 2 or more and is preferably 2 or 3. Examples of the group including the combination include a carbonyloxy group, a sulfonate linking group (—S(═O)2—O—), and a sulfinate linking group (—S(═O)—O—) (note that each of the sulfonate linking group and the sulfinate linking group includes a linking group where at least one oxygen atom in each of the groups is substituted with a sulfur atom).

[0091] The number of linking atoms in the linking group is not particularly limited, and is preferably 15 or less, more preferably 10 or less, still more preferably 6 or less, and still more preferably 4 or less. The lower limit is 1 or more. The number of linking atoms refers to the minimum number of atoms that connect the benzene ring and R2 in Formula (II) or Formula (TIC). The number of atoms (number of constituent atoms) forming the linking group cannot be uniquely determined depending on RC of the phosphate linking group or the like. For example, the number of atoms forming the linking group can be 1 to 100 and is preferably 1 to 40 and more preferably 1 to 24.

[0092] A preferable first aspect of the monovalent substituent that can be used as L is an aspect where the heteroatom is directly bonded to the benzene ring in Formula (II) or Formula (IIC). In this aspect, the heteroatom in the divalent linking group is preferably a sulfur atom or a phosphorus atom and can also further include an oxygen atom. On the other hand, a preferable second aspect of the divalent linking group that can be used as L is an aspect where the heteroatom is not directly bonded to the benzene ring in Formula (II). In this aspect, the heteroatom in the divalent linking group is preferably an oxygen atom. In the linking group of the second aspect, the linking portion such as the atom or the linking group that is directly bonded to the benzene ring in the Formula (II) or Formula (IIC) is the same as that of the preferable second aspect of the monovalent substituent that can be used as X in Formulae (I) and (IC), and is preferably a carbon atom.

[0093] The number of kinds of heteroatoms and the number of atoms in the divalent linking group that can be used as L are not particularly limited, and are preferably the same as the number of kinds of heteroatoms and the number of atoms in the monovalent substituent that can be used as X.

[0094] In the linking group that can be used as L, the heteroatom may be present at any position of the divalent linking group, for example, may be present in an atomic chain forming the divalent linking group or at a terminal thereof. In the present invention, an aspect where one heteroatom is present at a terminal of an atomic chain forming the linking group and is bonded to the benzene ring in Formula (II) or Formula (IIC), or an aspect where one heteroatom forms a carbonyl group and is bonded to the benzene ring in Formula (II) or Formula (IIC) is preferable.

[0095] The divalent linking group that can be used as L is not particularly limited as long as it includes the heteroatom and does not include a nitrogen atom, and examples thereof include a substituent that includes the heteroatom and does not include a nitrogen atom among the substituents in the substituent GZ described below. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, a structure forming each of the functional groups in the group G of functional groups described below is preferable. Examples of a divalent linking group that can be used as a preferable first aspect among the functional groups in the group G of functional groups include a structures forming each of a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group, specifically, a structure obtained by removing RC or RD from each of the groups. Examples of a divalent linking group that can be used as a preferable second aspect include a structure forming a carboxy group, specifically, a carbonyloxy group.

[0096] The hydrocarbon group that can be used as R2 is not particularly limited, and examples thereof include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, and an aralkyl group. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, an alkyl group is preferable.

[0097] Each of the alkyl group and the alkyl group in the alkenyl group, the alkynyl group, and the aralkyl group that can be used as R2 is not particularly limited, may be a straight chain, a branched chain, or a cyclic chain, and is preferably a branched chain from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level. In a case where the alkyl group or the like that can be used as R2 is a branched chain, the number of branched carbon atoms present in the group is not particularly limited as long as it is 1 or more. A preferable first aspect of the number of branched carbon atoms present in the branched chain is 1 or 2. On the other hand, a preferable second aspect of the number of branched carbon atoms present in the branched chain is 3 or more, can be 3 to 10, and is preferably 3 to 8 and more preferably 4 to 7.

[0098] The total number of carbon atoms (simply referred to as the number of carbon atoms) forming the hydrocarbon group that can be used as R2 is not particularly limited as long as it is 8 or more, and is preferably 9 to 20 from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level. As a preferable first aspect of the number of carbon atoms in the hydrocarbon group that can be used as R2, the number of carbon atoms is more preferably 8 to 11, still more preferably 8 to 10, and still more preferably 8 or 9 from the viewpoints of the selectivity and the durability of the metal extractant. On the other hand, as a preferable second aspect of the number of carbon atoms in the hydrocarbon group that can be used as R2, the number of carbon atoms is more preferably 10 to 24 and still more preferably 12 to 20 from the viewpoint that the durability can be further improved while maintaining high selectivity of the metal extractant.

[0099] In a case where RC in the linking group L represents a hydrocarbon group, R2 may be the same as or different from this hydrocarbon group.

[0100] The compound represented by Formula (II) is a non-polymerizable compound as in the compound represented by Formula (I) or Formula (IC).

[0101] The compound represented by Formula (II) or Formula (TIC) can be formed by appropriately combining R1, L, R2, and a in the formula, and is preferably formed by combining preferable examples of the respective reference numerals.

[0102] Note that the compound represented by Formula (II) or Formula (IIC) preferably includes at least one active hydrogen atom as in the compound represented by Formula (I) or Formula (IC). The active hydrogen atom may be present in any of a ring formed by R1, L, R2, or α, and is preferably present in R1 or L. The number of hydroxy groups present in the compound is the same as that of the compound represented by Formula (I) or Formula (IC).

[0103] In the compound represented by Formula (II) or Formula (IIC), a bonding position of an —OR1 group and -L-R2 to the benzene ring is not particularly limited, and is the same as the bonding position of the —OR1 group and X to the benzene ring in the compound represented by Formula (I) or Formula (IC).

[0104] In the compound represented by Formula (IIC), the position where the ring formed by a is bonded to the benzene ring is not particularly limited, and is the same as the position where the ring formed by a is bonded to the benzene ring in the compound represented by Formula (I) or Formula (IC).

[0105] It is preferable that the compound according to the embodiment of the present invention (including the compound represented by Formula (II)) has a functional group selected from the group G of functional groups. It is preferable that a coordinating functional group coordinated to metal ions to be extracted contributes to improvement of the selectivity and the durability of the metal extractant including the compound according to the embodiment of the present invention.

[0106] As long as the compound according to the embodiment of the present invention includes the following functional group in a molecule, a position at which the following functional group is introduced and bonded is not particularly limited. For example, the functional group may be bonded to the benzene ring in each of the formulae, may be bonded to a ring formed by any atom group a, or may be introduced as R1 or into R1. In the present invention, from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the functional group is introduced as X or into X in Formula (I) or Formula (IC) or is introduced as -L-R2 in Formula (II) or Formula (IIC).

[0107] From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, the functional group in the compound according to the embodiment of the present invention is preferably a phosphate group or a phosphonate group among the group G of functional groups, and more preferably a phosphate group or a phosphonate group where all of XA, XB, and Z represent oxygen atoms.<Group G of Functional Groups>

[0108] A carboxy group, a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group (—S(═O)2ORC), and a sulfinate group (—S(═O)ORC)

[0109] The phosphate group, the phosphonate group, and the phosphinate group are typically represented by —OP(═O)(ORC)2, —P(═O)(ORC)2, and —P(═O)(ORC)RD, respectively. The phosphate group, the phosphonate group, and the phosphinate group as the functional groups in the present invention refer to groups represented by —XA—P(=Z)(XBRC)2, —P(═Z)(XBRC)2, and —P(═Z)(XBRC)RD, respectively. Here, XA represents an oxygen atom or a sulfur atom and preferably an oxygen atom. XB represents an oxygen atom or a sulfur atom, and preferably an oxygen atom. Z represents an oxygen atom or a sulfur atom and preferably an oxygen atom. A combination of XA, XB, and Z in each of the groups is not particularly limited and can be appropriately set. In each of the phosphate group, phosphonate group, and the phosphinate group, it is preferable that all of XA, XB, and Z represent oxygen atoms.

[0110] In the present invention, RC and RD in the coordinating functional group each independently represent a hydrogen atom or a substituent. The substituent that can be used as RC and RD are not particularly limited, and examples thereof include groups selected from the substituent GZ described below. In particular, as the substituent that can be used as RC and RD, from the viewpoint of solubility in the oil phase, a hydrocarbon group such as an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group is preferable. The hydrocarbon group that can be used as RC and RD is not particularly limited, and is preferably the same as the hydrocarbon group that can be used as R2 in Formula (II) and more preferably an alkyl group.

[0111] Two RC's in each of the phosphate group and the phosphonate group may be the same as or different from each other. In a case where two RC's are different, it is preferable that one RC represents a hydrogen atom and the other RC represents a hydrocarbon group. In a case where the functional group is introduced as the -L-R2 group in Formula (II) or Formula (IIC), assuming that the phosphate group and the phosphonate group include one hydrocarbon group, this hydrocarbon group is analyzed as R2. In addition, it is preferable that, in phosphinic acid, RC represents a hydrogen atom and RD represents a hydrocarbon group.

[0112] The carboxy group may form a salt. In addition, in a case where RC represents a hydrogen atom, the phosphate group, the phosphonate group, the sulfonate group, the phosphinic acid, or the sulfinate group may form a salt. A cation that forms a salt is not particularly limited, and examples thereof include a metal cation, in particular, a metal cation belonging to Group 1 or Group 2.

[0113] A preferable first aspect that can be used as two RC's and RC and RD is an aspect (an aspect of an acidic functional group) where, in each of the functional groups, one RC represents a hydrogen atom and the remaining RC or RD represents a substituent. In this aspect, each of the functional groups includes one hydroxyl group, and one monovalent substituent can be used as R1. On the other hand, a preferable second aspect that can be used as two RC's and RC and RD is an aspect (an aspect of an acidic functional group) where, in each of the functional groups, RC and RD represent a substituent. In this aspect, two substituents may be the same as or different from each other and are preferably a hydrocarbon group. In this second aspect, each of the functional groups includes a hydroxyl group, and a hydrogen atom or a metal element is used as R1.

[0114] The compound according to the embodiment of the present invention only needs to include at least one functional group selected from the group G of functional groups, or may include two or more functional groups.

[0115] From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the compound according to the embodiment of the present invention includes a hydrocarbon group having 9 or more carbon atoms.

[0116] As long as the compound according to the embodiment of the present invention including the hydrocarbon group having 9 or more carbon atoms includes a hydrocarbon group having 9 or more carbon atoms, a position where this hydrocarbon group is introduced and bonded is not particularly limited. For example, the functional group may be bonded to the benzene ring in each of the formulae, may be bonded to a ring formed by any atom group a, or may be introduced as R1 or into R1. In the present invention, from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the hydrocarbon group having 9 or more carbon atoms is introduced as X or into X in Formula (I) or Formula (IC) or is introduced as -L-R2 in Formula (II) or Formula (IIC), it is more preferable that the hydrocarbon group having 9 or more carbon atoms is introduced into the functional group selected from the group of functional groups, and it is still more preferable that the hydrocarbon group having 9 or more carbon atoms is introduced as RC in ORC in the phosphate group and the phosphonate group or as RD in the phosphinate group among the functional groups.

[0117] Examples of the hydrocarbon group having 9 or more carbon atoms include hydrocarbon groups having 9 or more carbon atoms among the hydrocarbon groups that can be used as R2.

[0118] The number of hydrocarbon groups having 9 or more carbon atoms in the compound according to the embodiment of the present invention is not particularly limited, can be 1 or more, and is preferably 1 or 2.

[0119] In a case where the compound according to the embodiment of the present invention includes two hydrocarbon groups having 9 or more carbon atoms, a preferable first aspect of a combination of the hydrocarbon groups is an aspect where a hydrocarbon group having 12 or more carbon atoms and a hydrocarbon group having 8 to 11 carbon atoms are combined. In this aspect, the number of hydrocarbon groups having 12 or more carbon atoms is more preferably 14 or more. The upper limit of carbon atoms is not particularly limited, but is, for example, preferably 24 or less and more preferably 20 or less. A preferable second aspect of a combination of the hydrocarbon groups is an aspect where hydrocarbon groups having 12 or more carbon atoms are combined. In this aspect, the number of carbon atoms in the hydrocarbon group having 12 or more carbon atoms is the same as the number of carbon atoms in the first aspect.

[0120] In the compound according to the embodiment of the present invention, the second aspect also includes an aspect where the two hydrocarbon groups having 9 or more carbon atoms are changed to hydrocarbon groups having 8 to 11 carbon atoms (referred to as a third aspect for convenience of description).

[0121] On the other hand, in the first aspect to the third aspect regarding the combination of the two hydrocarbon groups in the compound according to the embodiment of the present invention, a molecular structure of the hydrocarbon group is not particularly limited. From the viewpoints of the selectivity and the durability of the metal extractant, a combination of hydrocarbon groups having a branched structure is preferable, and a combination of alkyl groups having a branched structure is more preferable. In addition, in each of the aspects, the kind of the hydrocarbon group is not particularly limited. The same (kind) of substituents may be combined, or different (kinds) of substituents may be combined. As the combination of the same substituents, a combination of alkyl groups is preferable from the viewpoints of the selectivity and the durability of the metal extractant.

[0122] The compound according to the embodiment of the present invention may function as a monodentate ligand for specific metal ions (metal ions to be extracted) present in the water phase, but preferably functions as a multidentate ligand from the viewpoints of the selectivity and the durability.

[0123] The molecular weight of the compound according to the embodiment of the present invention is not particularly limited, and, for example, can be 150 to 50,000. From the viewpoints of solubility in the oil phase, the molecular weight is preferably 200 to 10,000 and more preferably 250 to 1,000. In the present invention, in a case where the compound according to the embodiment of the present invention has a polymer chain, unless specified otherwise, the molecular weight of the oligomer refers to the number-average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC).—Measurement of Molecular Weight—

[0124] Regarding a method of measuring the molecular weight of the oligomer, basically, a value measured using a method under the following condition 1 or condition 2 (preferred) is used. In this case, an appropriate eluent may be selected and used depending on the kind of the oligomer.(Condition 1)Column: Connect two TOSOH TSKgel Super AWM-H (trade name, manufactured by

[0126] Tosoh Corporation)

[0127] Carrier: 10 mM LiBr / N-methylpyrrolidone

[0128] Measurement temperature: 40° C.

[0129] Carrier flow rate: 1.0 ml / min

[0130] Sample concentration: 0.1% by mass

[0131] Detector: refractive index (RI) detector(Condition 2)Column: A column obtained by connecting TOSOH TSKgel Super HZM-H, TOSOH

[0133] TSKgel Super HZ4000, and TOSOH TSKgel Super HZ2000 (all of which are trade names,

[0134] manufactured by Tosoh Corporation)

[0135] Carrier: tetrahydrofuran

[0136] Measurement temperature: 40° C.

[0137] Carrier flow rate: 1.0 ml / min

[0138] Sample concentration: 0.1% by mass

[0139] Detector: refractive index (RI) detector

[0140] The pKa of the compound according to the embodiment of the present invention is not particularly limited, an appropriate value can be adopted, and a value of 1.0 to 14 is preferable. For example, in a case where the compound according to the embodiment of the present invention preferably includes an active hydrogen atom as a hydroxy group bonded to a phosphorus atom in X of Formula (I) or Formula (IC) or in L of Formula (II) or Formula (IIC), the pKa has a small value and specifically is likely to be in a range of 2.0 to 7.5. On the other hand, in a case where the compound according to the embodiment of the present invention includes a hydrogen atom as R1 of each of the formulae and does not include an active hydrogen atom in X of Formula (I) or Formula (IC) or in L of Formula (II) of Formula (IIC), the pKa is a large value and specifically is likely to be in a range of 8.0 to 14. The pKa can be measured using a neutralization titration method.

[0141] The compound according to the embodiment of the present invention may include a substituent, and examples of the substituent that may be included in the compound include groups (excluding a group including a nitrogen atom) selected from the substituent GZ described below.

[0142] The compound according to the embodiment of the present invention can be synthesized with reference to a well-known synthesis method, for example, a synthesis method described in Examples described below.

[0143] Specific examples of the compound according to the embodiment of the present invention include the following compounds in addition to compounds synthesized in Examples, but the present invention is not limited thereto.—Substituent GZ—

[0144] The substituent GZ includes: an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylheptyl, benzyl, 2-ethoxyethyl, or 1-carboxymethyl); an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, or oleyl); an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, or phenyl-ethynyl); a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms; for example, cyclopropyl, cyclopentyl, cyclohexyl, or 4-methylcyclohexyl; the meaning of an alkyl group described in the present invention typically includes a cycloalkyl group but, here, an alkyl group and a cycloalkyl group are distinguished from each other); an aryl group (preferably an aryl group having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, or 3-methylphenyl); an aralkyl group (preferably an aralkyl group having 7 to 23 carbon atoms, for example, benzyl or phenethyl); a heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms and more preferably a 5- or 6-membered heterocyclic group having at least one oxygen atom, sulfur atom, or nitrogen atom. The heterocyclic group includes an aromatic heterocyclic group and an aliphatic heterocyclic group. 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); an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, or benzyloxy); an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, or 4-methoxyphenoxy); a heterocyclic oxy group (a group in which an —O— group is bonded to the above-described heterocyclic group); an alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, or dodecyloxycarbonyl); an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, or 4-methoxyphenoxycarbonyl); a heterocyclic oxycarbonyl group (a group in which an —O—CO— group is bonded to the above-described 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 (—NH2), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, or anilino); a sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl or N-phenylsufamoyl); an acyl group (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, or nicotinoyl); an acyloxy group (an alkylcarbonyloxy group, an alkenylcarbonyloxy group, an alkynylcarbonyloxy group, or a heterocyclic carbonyloxy group, preferably an acyloxy group having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, or nicotinoyloxy); an aryloyloxy group (preferably an aryloyloxy group having 7 to 23 carbon atoms, for example, benzoyloxy or naphthoyloxy); a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl or N-phenylcarbamoyl); an acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, for example, acetylamino or benzoylamino); an alkylthio group (preferably an alkylthio group having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, or benzylthio); an arylthio group (preferably an arylthio group having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, or 4-methoxyphenylthio); a heterocyclic thio group (a group in which an —S— group is bonded to the above-described heterocyclic group); an alkylsulfonyl group (preferably an alkylsulfonyl group having 1 to 20 carbon atoms, for example, methylsulfonyl or ethylsulfonyl); an arylsulfonyl group (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, or 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, or triethoxysilyl); an aryloxysilyl group (preferably an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl); a phosphoryl group (preferably a phosphate group having 0 to 20 carbon atoms, for example, —OP(═O)(R′)2); a phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, —P(═O)(R′)2); a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R′)2); a phosphonate group (preferably a phosphonate group having 0 to 20 carbon atoms, for example, —PO(OR′)2); a sulfo group (a sulfonate group), a carboxy group, a hydroxy group, a sulfanyl group, a cyano group, and a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). R1 represents a hydrogen atom or a substituent (preferably a group selected from the substituent GZ).

[0145] In addition, each group exemplified in the substituent GZ may be further substituted with the substituent GZ.

[0146] The alkyl group, the alkylene group, the alkenyl group, the alkenylene group, the alkynyl group, the alkynylene group, and / or the like may be cyclic or chained, may be linear or branched.[Separation Recovery Method of Metal Ions]

[0147] A separation recovery method of metal ions according to an embodiment of the present invention (hereinafter, also referred to as the separation recovery method according to the embodiment of the present invention) is a method of mixing a water phase including plural kinds of metal ions and an oil phase including the metal extractant according to the embodiment of the present invention. As a result, the specific metal ions to which the metal extractant according to the embodiment of the present invention is coordinated can be moved (extracted) to be separated and recovered from the water phase to the oil phase with high selectivity and high recovery rate. Further, even in a case where the metal extractant according to the embodiment of the present invention that has been used once is repeatedly used (reused), a decrease in selectivity and recovery rate during an initial use is suppressed, and specific metal ions can be separated and recovered with high selectivity and high recovery rate. In addition, even in a case where the metal extractant according to the embodiment of the present invention is in contact with the water phase for a long period of time, a decrease in initial selectivity and initial recovery rate is suppressed, and specific metal ions can be separated and recovered with high selectivity and high recovery rate. That is, even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, specific metal ions present in the water phase can be extracted to the oil phase while suppressing a decrease in initial high selectivity and initial high recovery rate. Here, the metal ions to be extracted to the oil phase may be a part of the plural kinds of metal ions in the water phase or may be all kinds of different-group metal ions in the water phase.

[0148] Even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, as ions of a valuable metal element, one kind of metal ions can be extracted to the oil phase with high selectivity and high recovery rate. In this case, one kind of metal ions among two or more kinds of different-group metal ions, for example, two or more kinds of different-group metal ions belonging to Group 1 to Group 14 in the periodic table can be extracted to the oil phase with high selectivity and high recovery rate. In particular, even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, one kind of metal ions among two or more kinds of different-group metal ions belonging to Group 8 to Group 12 in the periodic table, particularly desirably, cobalt ions and nickel ions that are same-period different-group metal ions can be extracted to the oil phase with high selectivity and high recovery rate.

[0149] The present inventors found that the metal extractant according to the embodiment of the present invention has the characteristics and function in which, while extracting two or more kinds of metal ions among plural kinds of metal ions (groups) present in the water phase to the oil phase together in the wet extraction method, one kind of metal ions can be extracted to the oil phase with high selectivity and high recovery rate over a long period of time, and applies the separation recovery method according to the embodiment of the present invention to the new use where two or more kinds of metal ions, in particular, different-group metal ions are separated and recovered.<Water Phase>

[0150] Water formed in the water phase is not particularly limited, and (super) pure water, ion exchange water, or the like can be used.

[0151] The metal ions in the water phase may include metal ions of at least two metal elements belonging to Group 1 to Group 14 in the periodic table, preferably includes at least two kinds of metal ions belonging to Group 3 to Group 14, and may include metal ions belonging to Group 15 to Group 17.

[0152] In the present invention, it is preferable that two or more kinds of metal ions belonging to Group 1 to Group 14 are included, it is more preferable that two or more kinds of metal ions belonging to Group 3 to Group 14 are included, and it is still more preferable that ions of at least one kind of a transition metal element (transition metal element belonging to Group 3 to Group 12) are included. In an aspect including at least one transition metal element, it is preferable that two or more kinds of metal ions belonging to Group 4 to Group 12 are included, it is more preferable that two or more kinds of metal ions belonging to Group 4 to Group 10 are included, it is still more preferable that two or more kinds of metal ions belonging to Group 8 to Group 12 are included, it is still more preferable that two or more kinds of metal ions belonging to Group 9 to Group 12 are included, and it is most preferable that two or more kinds of metal ions belonging to Group 9 and Group 10 are included. The metal ions belonging to each of the groups are not particularly limited, metal ions belonging to the fourth to sixth periods in the periodic table are preferable, and metal ions belonging to the fourth period or the fifth period are more preferable. In addition, the number of kinds of the metal ions is not particularly limited as long as it is 2 or more. For example, the number of kinds of the metal ions can be 2 to 15 and is preferably 2 to 8 and more preferably 2 to 5.

[0153] A combination of the plurality of metal ions is not particularly limited, and examples of a combination of groups include a combination including Group 9 and Group 10, a combination including Group 9 and Group 12, a combination including Group 4 and Group 9, a combination including Group 8 and Group 10, a combination including Group 7, Group 9, and Group 10, and a combination of Group 7, Group 8, Group 9, and Group 10.

[0154] In the present invention, the number of kinds of metal ions belonging to each of the groups may be two or more but, from the viewpoint of exhibiting high selectivity, is preferably one.

[0155] Specific examples of the combination of the metal ions include a combination including Co and Ni, a combination including Co and Zn, a combination including Fe and Ni, a combination including Zr and Rh, a combination including Mn, Co, and Ni and a combination including Mn, Fe, Co, and Ni.

[0156] The plural kinds of metal ions in the water phase may include the same group of metal ions, or may include different-group metal ions. The number of kinds of the different-group metal ions in the water phase may be 2 or more and, for example, is preferably 2 to 4 and more preferably 2.

[0157] The metal element belonging to each of the groups is not particularly limited, and an appropriate atom can be used. Examples of the metal element belonging to each of the groups are as follows.

[0158] Preferable examples of a metal element belonging to Group 1 include Li, Na, Rb, and Cs.

[0159] Preferable examples of a metal element belonging to Group 2 include Mg, Ca, Sr, and Ba.

[0160] Preferable examples of a metal element belonging to Group 3 include Sc and Y.

[0161] Preferable examples of a metal element belonging to Group 4 include Ti, Zr, and Hf.

[0162] Preferable examples of a metal element belonging to Group 5 include V, Nb, and Ta.

[0163] Preferable examples of a metal element belonging to Group 6 include Cr, Mo, and W.

[0164] Preferable examples of a metal element belonging to Group 7 include Mn and Tc.

[0165] Preferable examples of a metal element belonging to Group 8 include Fe, Ru, and Os.

[0166] Preferable examples of a metal element belonging to Group 9 include Co, Rh, and Ir.

[0167] Preferable examples of a metal element belonging to Group 10 include Ni, Pd, and Pt.

[0168] Preferable examples of a metal element belonging to Group 11 include Cu, Ag, and Au.

[0169] Preferable examples of a metal element belonging to Group 12 include Zn, Cd, and Hg.

[0170] Preferable examples of a metal element belonging to Group 13 include Al, Ga, In, and Tl.

[0171] Preferable examples of a metal element belonging to Group 14 include Ga, Sn, and Pb.

[0172] Preferable examples of a metal element belonging to Group 15 include Sb and Bi.

[0173] A metal element belonging to Group 16 is not particularly limited, and preferable examples thereof include Te.

[0174] The plural kinds of metal ions can be appropriately prepared and, for example, various metal salts (salts of typical elements with inorganic acids such as nitric acid or sulfuric acid or organic acids such as acetic acid), a mixture of mined metals (ion), a recovery from metal waste, other waste such as a metal recovery from a waste battery (LiB), or a mixture thereof can be used. Examples of the metal recovery from the waste LiB include recoveries obtained using a well-known method such as a wet process or electrolysis.

[0175] A total content of the plural kinds of metal ions in the water phase is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 1,000,000 mass ppm and is preferably 1,000 to 100,000 mass ppm, more preferably 1,000 to 80,000 mass ppm, and still more preferably 2,000 to 30,000 mass ppm.

[0176] A total content of the metal ions belonging to Group 8 to Group 12 among the metal ions is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 80,000 mass ppm and is preferably 1,000 to 60,000 mass ppm and more preferably 2,000 to 30,000 mass ppm.

[0177] A total content of the metal ions belonging to Group 3 to Group 7 and Group 13 to Group 16 among the metal ions is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 60,000 mass ppm and is preferably 1,000 to 30,000 mass ppm.

[0178] A content of the metal ions belonging to each of the groups is not particularly limited and is appropriately set. For example, the content can be 1,000 to 60,000 mass ppm and is preferably 1,000 to 50,000 mass ppm and more preferably 2,000 to 25,000 mass ppm. In a case where two or more kinds of metal ions belonging to each of the groups are present, the content of the metal ions belonging to each of the groups is the total content.

[0179] In the present invention, in a case where the water phase includes different-group metal ions, the content of the metal ions belonging to one group may be more than or less than a content of the metal ions belonging to another group. In the separation recovery method according to the embodiment of the present invention, the metal ions can be separated and recovered multiple times with high selectivity and high recovery rate. Therefore, the contents of the metal ions belonging to different groups do not need to be set at a specific ratio. For example, a mass ratio of the content of metal ions belonging to a specific group (for example, metal ions extracted in the maximum amount) to the content of metal ions belonging to another group (for example, metal ions other than the metal ions extracted in the maximum amount (including metal ions that are not extracted) [the content of the metal ions belonging to the specific group:the content of the metal ions belonging to the other group] can be, for example, 100:1 to 10,000 and is preferably 100:10 to 5,000, more preferably 100:50 to 1,000, and still more preferably 100:80 to 130.

[0180] The pH of the water phase is not particularly limited and is appropriately set. For example, the pH of the water phase is preferably 0.1 to 10 and more preferably 2.0 to 10 in consideration of the solubility of the metal ions, the formation of complex ions, and the like.

[0181] The pH of the water phase can be adjusted, for example, using an acid or an alkali. As the acid, a well-known acid can be used without any particular limitation, and examples thereof include an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid and an organic acid such as formic acid, acetic acid, oxalic acid, organic phosphoric acid, or organic sulfonic acid. As the alkali, a well-known alkali can be used without any particular limitation, and examples thereof include an inorganic alkali and an organic alkali. Among these, an inorganic alkali is preferable. Examples of the inorganic alkali include a hydroxide of a metal belonging to Group 1 or Group 2, a metal alkali such as a carbonate, ammonia water, and ammonium chloride. Examples of the organic alkali include an organic ammonium salt.

[0182] The temperature of the water phase is not particularly limited and can be, for example, 10° C. to 60° C.

[0183] The water phase may optionally include, for example, a ligand coordinated to metal ions or a compound that generates the ligand.

[0184] The water phase can be prepared by dissolving metal ions in water. Preparation conditions of the water phase are not particularly limited. For example, the preparation temperature can be 10° C. to 60° C.

[0185] The water phase may include a masking agent in addition to the above-described metal ions. As the masking agent, various well-known agents can be used without any particular limitation. Examples of the masking agent include a monodentate ligand such as ammonia or a chelating agent such as dithizone.<Oil Phase>

[0186] In the separation recovery method according to the embodiment of the present invention, the oil phase (organic phase) including one kind or two or more kinds of the metal extractants according to the embodiment of the present invention is used for the above-described water phase. In the present invention, even in a metal extractant that is recovered and purified after use (also referred to as a recovered product) and a metal extractant that is used for a long period of time (both of which will be collectively referred to as a used product), high selectivity and high recovery rate of an unused metal extractant (also referred to as an unused product) are maintained. Therefore, the metal extractant according to the embodiment of the present invention in the oil phase may be the unused product or the used product or may be a combination of the unused product and the used product. In a case where the unused product and the used product are combined, the mixing ratio is not particularly limited and is appropriately determined.

[0187] In addition, the metal extractant used in the separation recovery method according to the embodiment of the present invention may include other metal extractants as described above, but preferably includes the compound according to the embodiment of the present invention alone.

[0188] The metal extractant according to the embodiment of the present invention exhibits solubility in an organic solvent, is present in the oil phase, is coordinate-bonded to metal ions present in the vicinity of an interface between the water phase and the oil phase, and has a function of moving the metal ions to the oil phase. In the present invention, the solubility in the organic solvent refers to a property in which the metal extractant is soluble in the organic solvent in a content described below.

[0189] The organic solvent for forming the oil phase is not particularly limited, and an appropriate organic solvent can be used. Examples of the organic solvent include an alcohol solvent, an ether solvent, a hydrocarbon-based solvent (an aromatic solvent or an aliphatic solvent), and a halogen solvent. In particular, a hydrocarbon-based solvent is preferable, various solvents as components separated from petroleum are more preferable, and hydrocarbon-based solvents of aromatic groups, paraffin, naphthene, kerosine, gasoline, naphtha, heating oil, and light oil are still more preferable.

[0190] The content of the metal extractant in the oil phase is appropriately set in consideration of the content of the 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 millimole / L (mM), and is preferably 50 to 1,000 millimole / L and more preferably 100 to 500 millimole / L.

[0191] The temperature of the oil phase is not particularly limited and can be, for example, 10° C. to 60° C.

[0192] The oil phase may include appropriate components in addition to the acidic metal extractant according to the embodiment of the present invention.

[0193] The oil phase can be prepared by dissolving the metal extractant in the organic solvent. Preparation conditions of the oil phase are not particularly limited. For example, the preparation temperature can be 10° C. to 60° C.<Contact and Mixing>

[0194] In the separation recovery method according to the embodiment of the present invention, the water phase and the oil phase described above are mixed and left to stand.

[0195] In this case, mixing conditions and standing conditions are not particularly limited and can be appropriately set. For example, mixing can be performed using various mixing devices. Examples of a method using the mixing device include a method using a magnetic stirrer (stirrer tip), a method using a mechanical stirrer, and a method using a mixer. Stirring conditions (a stirring rate, a stirring time, and the like) only need to be conditions (conditions where the metal extractant is coordinate-bonded to the metal ions) where the water phase and the oil phase can be mixed, and are appropriately set depending on the combination of the metal ions and the metal extractant, and the mixing temperature, and the mixing device. For example, as a stirring rate, a rotation speed of a magnetic stirrer or the like can be 80 rpm to 200 rpm. For example, a stirring time is not uniquely determined depending on stirring conditions and the like, and can be, for example, 10 minutes to 24 hours. A mixing temperature is not particularly limited, and can be, for example, 10° C. to 60° C.

[0196] Standing conditions can be appropriately set without any particular limit as long as they are conditions where the water phase and the oil phase can be separated into two layers. A standing time in the wet extraction method is typically set to 10 minutes to 24 hours after stopping the mixing. A standing temperature is not particularly limited, and can be, for example, 10° C. to 60° C.

[0197] During the mixing of the water phase and the oil phase, a mixing ratio between the water phase and the oil phase is appropriately set depending on a metal ion concentration, a concentration of the metal ions, the content (concentration) of the metal extractant, and the like, and is not uniquely determined. For example, in a case where the water phase and the oil phase that satisfy the respective concentrations are mixed, the ratio of the oil phase to 100 mL of the water phase can be 50 to 2,000 mL and is preferably 80 to 1,000 mL and more preferably 80 to 200 mL. On the other hand, focusing on the metal ions present in the water phase, it is preferable that the oil phase is mixed at a ratio of 0.5 to 20 mole times of the metal extractant to the total content (moles) of the metal ions, and it is more preferable that the oil phase is mixed at a ratio of 0.5 to 10 mole times of the metal extractant to the total content (moles) of the metal ions. In addition, the content of the metal extractant with respect to the total content of the metal ions to which the metal extractant can be coordinated (also referred to as the mixing amount; a ratio of the number of moles of the metal extractant to the total number of moles of the metal ions: molar ratio) can be, for example, 0.5 to 10.0 equivalents, and is preferably 0.5 to 6.0 equivalents. Here, the metal ions to which the metal extractant can be coordinated refers to metal ions that are coordinated to the metal extractant and are extracted to the oil phase.

[0198] During the mixing of the water phase and the oil phase, the pH of the mixing system can be adjusted. Here, the pH that is set for specific metal ions to be extracted is not uniquely determined and is appropriately determined in consideration of the pKa of the metal extractant, the complex formation constants of the metal extractant and the metal ions, the number of metal ions to be coordinated, and the like. The pH of the mixing system is preferably 0.01 to 14, more preferably, for example, 0.1 to 10. It is preferable that the pH of the mixing system is set according to the metal extractant to be used from the viewpoints of the selectivity and the recovery rate. For example, in a case where the pKa of the metal extractant (the compound according to the embodiment of the present invention) is the above-described small value, in the above-described range, the pH of the mixing system is preferably 0.5 to 9.0, more preferably 1.0 to 8.5, and still more preferably 2.0 to 8.0. On the other hand, in a case where the pKa of the metal extractant is the above-described large value, in the above-described range, the pH of the mixing system is preferably 5.0 to 12.0, more preferably 7.0 to 12.0, and still more preferably 7.0 to 11.0.

[0199] The adjustment of the pH can be performed using the acid or the alkali described above, an aqueous solution thereof, or the like, and one preferable aspect is an aspect where ammonia or an ammonium salt is not used.

[0200] In a case where the pH of the mixing system is adjusted during the mixing of the water phase and the oil phase, the mixing of the water phase and the oil phase and the standing after the mixing are performed after adjusting the pH.

[0201] In a two-phase separated fluid (a solvent extraction phase or a solvent extraction system) where the water phase and the oil phase are phase-separated that is obtained by mixing the water phase and the oil phase and leaving the mixture to stand, the water phase and the oil phase are phase-separated into layers and present in a state where they are in contact with each other. The metal ions to which the metal extractant is coordinate-bonded among the above-described plural kinds of metal ions are present (moved) in the oil phase.

[0202] In addition, the number of kinds of the metal ions extracted to the oil phase is ideally 1 but may also be 2 or more. In this case, for example, the number of kinds of the metal ions can be 2 to 10 and is preferably 2 to 6 and more preferably 2 or 3. The two or more kinds of metal ions extracted to the oil phase among the plural kinds of metal ions are not particularly limited and, for example, are preferably the same as the above-described two or more kinds of different-group metal ions (combination) in the water phase.

[0203] In the separation recovery method according to the embodiment of the present invention, using a simple method of mixing the water phase and the oil phase with each other and leaving the mixture to stand, specific metal ions among plural kinds of metal ions can be separated, recovered, and extracted with high selectivity and high recovery rate over a long period of time. In particular, while extracting ions of two or more kinds of metal elements, one kind of metal ions can be separated and recovered to an oil phase with high selectivity and high recovery rate over a long period of time. Further, even in a case where the used product is used as the metal extractant, specific metal ions can be separated and recovered with selectivity and recovery rate that are higher or equal to those of the unused product.

[0204] The one kind of metal ions that can be separated and recovered with high selectivity and high recovery rate are not uniquely determined depending on the group or the period of the metal ions, the content thereof, the kind of the metal extractant, and the like. For example, in a case where metal ions belonging to Group 9 and metal ions belonging to Group 10 are extracted to the oil phase, the metal ions belonging to Group 9 can be separated and recovered with high selectivity and high recovery rate. In particular, in a case where Co ions as metal ions belonging to Group 9 and Ni ions as metal ions belonging to Group 10 are extracted, the Co ions can be separated and recovered with high selectivity and high recovery rate. In addition, in a case where metal ions belonging to Group 9 and metal ions belonging to Group 12 are extracted to the oil phase, the metal ions belonging to Group 12 can be separated and recovered with high selectivity and high recovery rate. Further, in a case where metal ions belonging to Group 8 and metal ions belonging to Group 10 are extracted to the oil phase, the metal ions belonging to Group 8 can be separated and recovered with high selectivity and high recovery rate.

[0205] In the separation recovery method according to the embodiment of the present invention, as described above, one kind or two or more kinds of metal ions among plural kinds of metal ions present in the water phase can be extracted and recovered to the oil phase with high selectivity and high recovery rate. In particular, in the separation recovery method according to the embodiment of the present invention, while extracting ions of two or more kinds of metal elements, one kind of metal ions can be separated and recovered to the oil phase with high selectivity and high recovery rate. Therefore, by further subjecting the water phase including the two or more kinds of metal ions stripped from the oil phase to the separation recovery method according to the embodiment of the present invention, the selectivity of one kind of metal ions can be further improved without significant deterioration in recovery rate, and thus high-purity metal ions can be recovered with high recovery rate. Further, even in a case where the separation, recovery, and stripping is repeatedly performed multiple times or is continuously performed for a long period of time, metal ions can be extracted and recovered without deterioration in high selectivity and high recovery rate of the metal ions.

[0206] The separation recovery method according to the embodiment of the present invention can also be a method of extracting two or more kinds of metal ions.

[0207] In the separation recovery method according to the embodiment of the present invention, the metal extractant alone can be coordinated to metal ions to extract the metal ion to the oil phase. Therefore, the water phase and the oil phase do not need to include a compound that acts to extract metal ions in cooperation with the metal extractant according to the embodiment of the present invention, such as, a compound that is coordinated to metal ions or a compound that forms a ligand. For example, the water phase and the oil phase do not need to include a well-known metal extractant. In the separation recovery method according to the embodiment of the present invention, typically, the water phase including the specific metal ions as an essential component and the oil phase including the metal extractant according to the embodiment of the present invention as an essential component are used.

[0208] The separation recovery method according to the embodiment of the present invention may include steps other than the step of mixing the water phase and the oil phase with each other and leaving the mixture to stand. Examples of the other steps include a step of preliminarily mixing (pre-mixing) the water phase and the oil phase before adjusting the pH, a step of stripping (isolating) metal ions from the oil phase obtained in the step of mixing the water phase and the oil phase with each other and leaving the mixture to stand (step of stripping metal ions from the oil phase to recover a metal extractant), a step of recovering the stripped metal ions as a compound (salt), a step of purifying the stripped metal ions or the compound thereof, a step of purifying the recovered metal extractant, and a step of removing ions of metal elements belonging to Group 1 or Group 2 in the periodic table of elements in advance. As a method of stripping (isolating) the metal ions from the oil phase, a well-known method can be applied without any particular limitation. For example, the different-group metal ions can be stripped by adjusting the liquid phase to be acidic, for example, pH of 2 to 4 using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. By stripping the metal ions from the oil phase, the oil phase including the metal extractant can be recovered. In addition, as a method of recovering the stripped metal ions as a compound, a well-known method can be applied without any particular limitation.

[0209] The separation recovery method according to the embodiment of the present invention includes not only a method using the metal extractant (unused product) according to the embodiment of the present invention but also a method using the metal extractant (used product) recovered in the recovery step alone or in combination with the unused product, and a method using the oil phase (including the recovered metal extractant) obtained in the stripping step (method of bringing the oil phase into contact with a newly prepared water phase).

[0210] The separation recovery method according to the embodiment of the present invention may be performed through a batch process or a continuous process.

[0211] In the present invention, the metal extractant has high durability. Therefore, for example, in a batch process, using a non-treated water phase and the recovered metal extractant (oil phase), the number of times of process (the number of times of contact between the water phase and the oil phase) can be increased to repeat the process. The number of times the process can be repeated cannot be uniquely determined depending on contact conditions, a metal ion concentration, and the like as described above, and can be set to be, for example, 5 or more within a range where the selection ratio and the extraction rate are satisfied.

[0212] The separation recovery method using the repeated separation and recovery through the batch process is not particularly limited as long as it is a method using the recovered metal extractant (used product). For example, in one method, the first separation recovery method is performed using the metal extractant (unused product) according to the embodiment of the present invention, subsequently the second separation recovery method of bringing the oil phase (including the used product of the metal extractant according to the embodiment of the present invention) recovered in the first separation recovery method into contact with an unused water phase to mix them is performed, and the third or subsequent separation recovery method is repeatedly performed appropriately using the same method as the second separation recovery method. Specifically, a method described in Examples can be performed. The oil phase recovered in each of the separation recovery methods can also be appropriately purified. For example, a method of bringing metal ions mixed in the oil phase into contact with a water solvent to remove the metal ions can be used. Conditions in the first and second or subsequent separation recovery methods are as described above.

[0213] On the other hand, for example, in the continuous process method, a contact time between the water phase and the oil phase (time for which the oil phase is in contact with the water phase to be circulated) can be set to be long. A time for which the contact process can be performed cannot be uniquely determined depending on contact conditions, a metal ion concentration, the amount of the water phase to be circulated, and the like, and can be set to be, for example, 12 hours or longer within a range where the selection ratio and the extraction rate are satisfied. In the continuous process, the amount of the water phase to be used and circulated can also be set to be more than a mixing ratio between the water phase and the oil phase.

[0214] A device for performing the separation recovery method according to the embodiment of the present invention is not particularly limited, and a well-known device can be used. Examples of the device include a separating funnel and a mixer settler. In addition, a contact and mixing device including a liquid feeding device such as a flow synthesis system or an emulsion flow system can also be used. As conditions for contact, mixing, and standing in the continuous process, each of the above-described conditions can be applied.EXAMPLES

[0215] Hereinafter, the present invention will be described in more detail based on Examples but is not limited to these examples.

[0216] “Parts” and “%” that represent compositions in the following Examples are mass-based unless otherwise specified. In the present invention, “room temperature” refers to 25° C.[Preparation and Synthesis of Compounds]

[0217] Compounds shown below were synthesized and prepared.

[0218] A commercially available product manufactured by Tokyo Chemical Industry Co., Ltd. was used as a compound E-3 (octyl salicylate) shown below, and a commercially available product manufactured by ChemBridge Corporation was used as a compound E-5 (2-butoxybenzoic acid). In addition, a commercially available product of ACORGAM 5640 (trade name, manufactured by Solvay S.A.) was used as a compound T-1 (5-nonylsalicylaldoxime), a commercially available product of KELEX-100 (trade name, manufactured by Nordmann, Rassmann GmbH) was used as a compound T-2 (7-(4-ethyl-2-methyloctyl)-8-quinolinol), and a commercially available product manufactured by FUJIFILM Wako Pure Chemical Corporation was used as a compound T-3 (4-nonylphenol).<Synthesis of Compound E-1>

[0219] A compound E-1 was synthesized as follows.

[0220] Specifically, 15.1 g of N-chlorosuccinimide (manufactured by FUJIFILM Wako Pure Chemical Corporation) and 230 g of toluene (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, and were stirred at room temperature. N-chlorosuccinimide was dispersed in toluene without being dissolved. While cooling the three-necked eggplant flask with ice, 30.0 g of bis(2-chlorohexyl) phosphite (manufactured by Sigma-Aldrich Co. LLC) was slowly added dropwise. After completion of the dropwise addition, the reaction solution was returned to room temperature and was stirred for 5 hours. The obtained reaction solution was filtered to remove insoluble matter, and the solvent was distilled off under reduced pressure. While optionally adding hexane, the filtration and the distillation under reduced pressure were repeated to obtain 31.2 g (yield: 97%) of a light yellow liquid (intermediate E1).

[0221] Next, 8.3 g of phenol (manufactured by FUJIFILM Wako Pure Chemical Corporation) and 105 g of toluene were added to a 300 mL three-necked eggplant flask, and were stirred at room temperature. 19.1 g of pyridine (manufactured by FUJIFILM Wako Pure Chemical Corporation), 9.8 g of 4-dimethylaminopyridine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the light yellow liquid (intermediate E1) obtained in the previous stage were added to the obtained solution, and were stirred at 60° C. for 12 hours. The obtained reaction solution was added to water, and organic matter was extracted with hexane. The hexane solution was cleaned with a saturated sodium hydrogen carbonate solution and water, and the solvent was distilled off under reduced pressure. Silica gel chromatography (eluent: hexane) was performed on the obtained crude product to obtain 16.9 g of a colorless transparent liquid (intermediate E2).

[0222] Next, 40.0 g of tetrahydrofuran (super dehydrated, manufactured by FUJIFILM Wako Pure Chemical Corporation) was added to a 500 mL three-necked eggplant flask, and the solution was cooled at −78° C. using an acetone / dry ice bath. 64 mL of a 1.0 M hexane solution of lithium diisopropylamide (manufactured by Sigma-Aldrich Co. LLC) was added dropwise, and the reaction solution was stirred for 30 minutes. Next, a solution consisting of 16.9 g of the colorless transparent liquid (intermediate E2) obtained in the previous stage and 55.3 g of tetrahydrofuran was added dropwise while maintaining the temperature of the reaction solution at −50° C. or lower. After completion of the dropwise addition, the reaction solution was stirred for 1 hour and was stirred at 0° C. for 5 hours. 100 mL of a saturated ammonium chloride solution was added, the reaction solution was extracted with ethyl acetate, and the solvent was distilled off under reduced pressure. As a result, a crude product was obtained. Silica gel chromatography (eluent: hexane) was performed on the obtained crude product to obtain 20.7 g of a compound E-1 (yield: 65%, two steps).

[0223] The compound E-1 synthesized as described above was identified as follows.

[0224] That is, the compound E-1 was dissolved in deuterated chloroform, and 1H-NMR was measured (device: BRUKER 400). The obtained chart is shown in FIG. 1.

[0225] δ (ppm): 10.28 (1H, br s, OH), 7.43 (1H, t, J=7.1 Hz), 7.34 (1H, ddd, J=14.2, 7.7, 1.7 Hz), 6.97 (1H, t, J=7.7 Hz), 6.91 (1H, ddd, J=14.1, 7.4, 1.7 Hz), 4.05-3.82 (4H, m, OCH2—), 1.60-1.16 (18H, m), 0.90-0.82 (12H, m)

[0226] As a result, the obtained compound was identified to have the above-described structure represented by compound E-1.<Synthesis of Compound E-2>

[0227] A compound E-2 was synthesized as follows.

[0228] Specifically, 18.1 g of the compound E-1, 130 g of 2-ethylhexanol (manufactured by FUJIFILM Wako Pure Chemical Corporation), and 3.5 g of sodium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, and were stirred at room temperature. Next, the reaction solution was heated to 160° C. and stirred for 12 hours. 150 g of purified water was added to the obtained reaction solution, and the reaction solution was stirred for 20 minutes. After cleaning the obtained solution with toluene, 4 M hydrochloric acid was added to the water phase until the pH was 2 or higher. Next, by performing the toluene extraction and distilling off the solvent under reduced pressure, 11.1 g (yield: 89%) of the compound E-2 was obtained.<Synthesis of Compound E-4>

[0229] A compound E-4 was synthesized as follows.

[0230] Specifically, 15.5 g of the compound E-1, 10.2 g of butyl bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), and 200 g of dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, were stirred at room temperature, and were cooled with ice. 15.5 g of potassium carbonate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added, and the reaction solution was stirred at 40° C. for 7 hours. The obtained reaction solution was cast into a 3 L Erlenmeyer flask including 1.5 L iced water, and was stirred at room temperature for 1 hour. The obtained solution was extracted with hexane, and the solvent was distilled off under reduced pressure. As a result, 15.4 g (yield: 91%) of a compound where a phenol group of compound E-1 was butylated was obtained.

[0231] The obtained compound was hydrolyzed under the same conditions as those of the hydrolysis reaction in the synthesis of the compound E-2. As a result, 9.9 g (yield: 88%) of a compound E-4 was obtained.<Synthesis of Compound E-6>

[0232] A compound E-6 was synthesized using the same method as that of the compound E-1, except that, during the synthesis of the compound E-1, 2-butyl-1-n-octanol was used instead of 2-ethylhexanol.[Preparation of Metal Ion-Containing Aqueous Solution]

[0233] 47.7 g of cobalt (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemicals Corporation) and 52.6 g of nickel (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemicals Corporation) were added to a 1 L measuring flask, were diluted with ultrapure water, and were stirred and dissolved at 40° C. to prepare a metal ion-containing aqueous solution (W1).

[0234] In addition, sulfates of a combination of metal ions shown in the column “Metal Ion Concentration in Water Phase before Extraction (ppm)” of Table 1-1 were dissolved in ultrapure water such that the amounts thereof used were changed to obtain the metal ion concentration shown in the same column. As a result, each of metal ion-containing aqueous solutions (W2) and (W3) was prepared.

[0235] The results of measuring the pH of the prepared metal ion-containing aqueous solutions (W1) to (W3) using a pH meter (SK-620 pH II, measured by SATOTECH) are shown below.

[0236] Metal ion-containing aqueous solution (W1): 6.5

[0237] Metal ion-containing aqueous solution (W2): 7.0

[0238] Metal ion-containing aqueous solution (W3): 6.2<Preparation of Metal Extractant Solution (Oil Phase)>

[0239] Each of the synthesized or prepared compounds (all of which were unused products) was added to a 100 mL measuring flask, and was diluted using IP SOLVENT 2835 (a paraffin-based solvent, manufactured by Idemitsu Kosan Co., Ltd.) at room temperature. As a result, metal extractant solutions (Y1) to (Y6) and (Yc1) to (Yc3) (concentration: 350 mM) including the compounds as metal extractants were prepared, respectively.Example 1

[0240] Using the metal ion-containing aqueous solution (W1) and the oil phase (Y1) the separation extraction operation (wet extraction method) of metal ions was repeated 10 times as described below.

[0241] 10 mL of the extractant solution (Y1) with respect to 10 mL of the prepared metal ion-containing aqueous solution (W1) was added to a 30 mL vial tube, and the mixture was stirred using a stirrer tip at 25° C. for 30 minutes (pre-mixing). In this case, the mixing amount (unit: equivalent) of the compound E-1 with respect to the total content of metal ions to be coordinated (that have the same definition as the extracted metal ions; in Example 1, Co and Ni) was 0.98. Next, a 10 M sodium hydroxide aqueous solution or a 10 M hydrochloric acid was added to adjust the pH of the mixed solution to a value shown in the column “pH during Mixing” of Table 1-1. Further, the solution was stirred at 25° C. for 30 minutes, and was left to stand at the same temperature for 1 hour. After verifying that the solution was separated into two layers of the organic phase (oil phase) and the water phase, the separated water phase was extracted, the separation and recovery of the metal ions was performed, and the oil phase was extracted to recover the metal extractant.

[0242] The pH of the mixed solution was measured using a pH meter (SK-620 pH II, manufactured by SATOTECH).

[0243] This way, the initial (first) separation extraction operation was performed, the metal ions extracted in each of Examples are shown in the column “Kind” of the column “Extracted Metal Ions” of Table 1-1, and the metal ions extracted in the maximum amount are shown in the column “Maximum Extracted Ions” of Table 1-1.

[0244] Next, in the initial separation extraction operation, 10 mL of purified water was added to 10 mL of the separated and extracted oil phase, 10 M hydrochloric acid was added to adjust the pH of the mixed solution to 1.0, and the reaction solution was stirred at room temperature for 30 minutes and was left to stand at the same temperature for 1 hour. After verifying that the solution was separated into two layers of the organic phase (oil phase) and the water phase, the separated oil phase was extracted. As a result, the metal extractant was separated and purified to recover the whole oil phase.

[0245] This way, using the recovered oil phase (including the recovered product of the metal extractant), the second separation extraction operation was performed using the same method as that of the initial separation extraction operation (at this time, the mixing amount was 0.98 equivalents). The oil phase recovered in the second separation extraction operation was processed using the same method as described above to recover the metal extractant by the separation and purification.

[0246] The second separation extraction operation and the separation purification operation of the metal extractant were further repeated 8 times, that is, was performed 10 times in total (all of the mixing amounts were 0.98 equivalents). In a case where the amount of the organic solvent in the recovered oil phase was insufficient, the amount of the solution including IP SOLVENT 2835 was adjusted to 10 mL.Examples 2 to 8 and Comparative Examples 1 to 3

[0247] The separation extraction operations of the metal ions according to Examples 2 to 8 and Comparative Examples 1 to 3 were repeatedly performed 10 times using the same method as that of Example 1, except that the metal ion-containing aqueous solution and the extractant solution were changed to a combination shown in the column “Water Phase” and the column “Oil Phase” of Table 1-1, and the pH during the mixing of the water phase and the oil phase was set to a value shown in the column “pH during Mixing” of Table 1-1.

[0248] The metal ions extracted in each of Examples are shown in the column “Kind” of the column “Extracted Metal Ions” of Table 1-1, and the metal ions extracted in the maximum amount are shown in the column “Maximum Extracted Ions” of Table 1-1.

[0249] In each of Examples and Comparative Examples, regarding each of the prepared water phases, each of the water phases recovered in the initial (first) separation extraction operation, and each of the water phases recovered in the tenth separation extraction operation, each of the contents of dissolved metal ions was determined using an inductively coupled plasma-optical emission spectrometer (ICP-OES) (Optima 7300 D (trade name), manufactured by Perkin Elmer Co., Ltd.). “,” in the metal ion concentration of the table represents a breakpoint of digits without representing a decimal point.

[0250] The measured value of the content of the dissolved metal ions prepared in each of the water phases prepared in Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase before Extraction (ppm)” of Table 1-1. In addition, the measured value of the content of the dissolved metal ions in each of the water phases recovered in the initial (first) separation extraction operation of Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase after Initial Extraction (ppm)” of Table 1-2, and the measured value of the content of the dissolved metal ions in each of the water phases recovered in the tenth separation extraction operation of Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase after Tenth Extraction (ppm)” of Table 1-2.<Evaluation 1: Evaluation of Extraction rate (Recovery Rate)>

[0251] In each of Examples and Comparative Examples, an extraction rate (unit: %) of metal ions extracted in the maximum extraction amount was calculated based on the following expression from a metal ion concentration CI in the prepared water phase (water phase before the first separation extraction operation) and a metal ion concentration C1 in the water phase after the first separation extraction operation or a metal ion concentration C10 in the water phase after the tenth separation extraction operation. The result is shown in the column “Initial Extraction Rate” or the column “Tenth Extraction Rate” of Table 1-2.

[0252] In the present test, as each of the extraction rates increases, the extractability (recovery power) of specific metal ions in each of the separation extraction operations is higher. In addition, as a difference between the initial extraction rate and the tenth extraction rate (initial extraction rate−tenth extraction rate) decreases, even in a case where the metal extractant is repeatedly used (the separation extraction operation is repeatedly performed), specific metal ions can be recovered while maintaining a high recovery rate of an unused metal extractant, and the metal extractant (compound used as the metal extractant) has higher durability.

[0253] In the present test, an initial extraction rate of 95% or more is pass, and a tenth extraction rate of 70% or more is pass.Initial⁢ Extraction⁢ rate⁢ (%)=[(CI-C⁢1) / CI]×100Tenth⁢ Extraction⁢ rate⁢ (%)=[(CI-C⁢10) / CI]×100<Evaluation 2: Evaluation of Selectivity (Separability)>

[0254] In each of Examples and Comparative Examples, the amounts (unit: ppm) of metal ions extracted were calculated based on the following formula from the metal ion concentration CI in the water phase before the first separation extraction operation and the metal ion concentration C1 in the water phase after the first separation extraction operation or the metal ion concentration C10 in the water phase after the tenth separation extraction operation, and the maximum amount (ppm) of the metal ions extracted was divided by the total amount CT (ppm) of the other metal ions extracted to calculate a selection ratio as a ratio between the amounts thereof extracted. The result is shown in the column “Initial Selection Ratio” or the column “Tenth Selection Ratio” of Table 1-2.

[0255] In the present test, as each of the selection ratios increases, characteristics (selectivity, separability) in which specific metal ions in each of the separation extraction operations are selectively extracted and recovered with respect to the other metal ions are higher. In addition, as the difference (Initial Selection Ratio−Tenth Selection Ratio) between the initial selection ratio and the tenth selection ratio decreases or as the tenth selection ratio further increases as compared to the initial selection ratio, even in a case where the metal extractant is repeatedly used (the separation extraction operation is repeatedly performed), specific metal ions can be selectively extracted and recovered while maintaining high selectivity of an unused metal extractant, and the metal extractant (compound used as the metal extractant) has higher durability from the viewpoint of the selectivity.

[0256] In the present test, an initial selection ratio of 1.5 or more is pass, and a tenth selection ratio of 1.5 or more is pass.Initial⁢ Selection⁢ Ratio=[(CI-C⁢1) / CT]×100Tenth⁢ Selection⁢ Ratio=[(CI-C⁢10) / CT]×100TABLE 1-1Metal Ion Concentration in WaterExtracted Metal IonspHOil PhaseWaterPhase before Extraction (ppm)MaximumduringMetalNo.PhaseCoNiZnFeKindExtracted IonsMixingExtractantExample 1W110,00011,00000Co, NiCo9.8Y1E-1Example 2W110,00011,00000Co, NiCo3.5Y2E-2Example 3W110,00011,00000Co, NiCo9.7Y3E-3Example 4W110,00011,00000Co, NiCo4.1Y4E-4Example 5W110,00011,00000Co, NiCo6.5Y5E-5Example 6W110,00011,00000Co, NiCo9.8Y6E-6Example 7W210,000012,0000Co, ZnZn7.5Y6E-6Example 8W3011,000011,000Ni, FeFe8.5Y6E-6ComparativeW110,00011,00000Co, NiCo6.8Yc1T-1Example 1ComparativeW110,00011,00000Co, NiCo10.3Yc2T-2Example 2ComparativeW110,00011,00000Co, NiCo9.9Yc3T-3Example 3TABLE 1-2Metal Ion Concentration in WaterInitialInitialMetal Ion Concentration in WaterTenthTenthPhase after Initial Extraction (ppm)ExtractionSelectionPhase after Tenth Extraction (ppm)ExtractionSelectionNo.CoNiZnFeRateRatioCoNiZnFeRateRatioExample 108,80000100%4.51,5009,1000085%4.5Example 206,20000100%2.12,3007,3000077%2.1Example 305,00000100%1.72,7006,5000073%1.6Example 408,90000100%4.83009,0000097%4.9Example 507,90000100%3.21,2008,3000088%3.3Example 609,80000100%8.35009,8000095%7.9Example 77,800000100%5.57,9000400097%5.5Example 808,70000100%4.808,800050095%4.8Comparative07,20000100%2.64,5008,9000055%2.6Example 1Comparative06,50000100%2.24,2008,1000058%2.0Example 2Comparative03,00000100%1.32,2004,1000078%1.1Example 3The following can be seen from the results and the like shown in Tables 1-1 and 1-2.In Comparative Examples 1 to 3 using T-1 to T-3 as metal extractants in the related art in the separation recovery of metal ions in the wet extraction method, the two kinds of metal ions present in the metal ion-containing aqueous solution (W1) were extracted to the oil phase. However, in Comparative Example 3 using the metal extractant T-3, regarding the metal ions (Co ions) extracted in the maximum amount, substantially the entire amount of Co ions were able to be extracted in the initial separation extraction operation, but a large amount of Ni was also extracted. Therefore, the initial selection ratio was low. On the other hand, in Comparative Examples 1 and 2 using the metal extractant T-1 or T-2, the tenth extraction rate was significantly lower than the initial extraction rate. Based on the above results, the metal extractants T-1 to T-3 were not able to be repeatedly used for the wet extraction method because a high selection ratio and durability were not able to be simultaneously achieved.

[0259] On the other hand, in all of Examples 1 to 8 where the compounds E-1 to E-6 according to the embodiment of the present invention were used as the metal extractants, two or kinds of metal ions among the metal ions present in the metal ion-containing aqueous solution were extracted to the oil phase. However, regarding the metal ions extracted in the maximum amount (Examples 1 to 6: Co ions, Example 7: Zn Ions, Example 8: Fe ions), substantially the entire amount of metal ions were able to be extracted in the initial separation extraction operation, and a high extraction rate of 73% or more was maintained even in the tenth separation extraction operation. Further, not only in the initial separation extraction operation but also in the tenth separation extraction operation, the metal ions extracted in the maximum amount were able to be extracted from the water phase to the oil phase with a high selection ratio with respect to the metal ions other than the metal ions extracted in the maximum amount. As a result, even in a case where the compound according to the embodiment of the present invention is recovered after being used for the wet extraction method and is reused multiple times for the wet extraction method, the selectivity and the recovery rate during the initial use can be maintained, and specific metal ions can be separated and recovered with high selectivity and high recovery rate.

[0260] In a case where the same experiment was performed using the same method as that of Examples 1 to 7 and Comparative Examples 1 to 3, except that the metal ion concentration in the water phase was reduced to ⅕, the same results were obtained.

[0261] It can be seen that, even in a case where the compound according to the embodiment of the present invention is repeatedly used as a metal extractant in the wet extraction method, metal ions present in the water phase can be separated and recovered with high selectivity and high recovery rate. Further, specific metal ions among two or more kinds of metal ions belonging to different groups having similar physical behaviors and similar chemical behaviors, in particular, one kind of metal ions among metal ions belonging to Groups 9 and 10 that can be recovered from waste LiB can be separated and recovered with high selectivity and high recovery rate. The details of the reason why the compound according to the embodiment of the present invention has the above-described excellent characteristics are not clear, but are presumed to be that the compound according to the embodiment of the present invention is not likely to be decomposed and deteriorate even after being exposed to conditions of the wet extraction method.

[0262] From the above results, it can be seen that, by stripping the oil phase obtained in each of Examples using a typical method and conditions, irrespective of the number of times of execution of the separation extraction operation, the metal ions can be separated and recovered to the oil phase simply with high selectivity, high recovery rate, and high productivity in a large recovery amount without deterioration in high selectivity.

[0263] Incidentally, in the technique of recovering specific metal ions from the water phase including a plurality of metal ions, it is generally difficult to recover the specific metal ions with high selectivity and recovery rate, and in a case where high selectivity is maintained, the recovery rate decreases. Therefore, in order to achieve a predetermined recovery rate, currently, it is required to perform the separation recovery operation multiple times. On the other hand, it can be seen that, even in a case where the metal extractant according to the embodiment of the present invention is used over a long period of time, using the simple method, one kind of metal ions among two kinds of different-group metal ions can be extracted from the water phase to the oil phase with high productivity, high selectivity, and high recovery rate. Therefore, in consideration of the current conditions, the technical significance of the present invention is high from the viewpoint that, through the stripping step or the like from the obtained oil phase, one kind of metal ions can be recovered simply and with high productivity and a small number of steps while further improving selectivity with high recovery rate and while further reusing the metal extractant.

[0264] The present invention has been described with the embodiments thereof, any details of the description of the present invention are not limited unless described otherwise, and it is obvious that the present invention is widely construed without departing from the gist and scope of the present invention described in the accompanying claims.

[0265] The present application claims priority based on JP2023-050477 filed on Mar. 27, 2023, the entire content of which is incorporated herein by reference.

Examples

example 1

[0240]Using the metal ion-containing aqueous solution (W1) and the oil phase (Y1) the separation extraction operation (wet extraction method) of metal ions was repeated 10 times as described below.

[0241]10 mL of the extractant solution (Y1) with respect to 10 mL of the prepared metal ion-containing aqueous solution (W1) was added to a 30 mL vial tube, and the mixture was stirred using a stirrer tip at 25° C. for 30 minutes (pre-mixing). In this case, the mixing amount (unit: equivalent) of the compound E-1 with respect to the total content of metal ions to be coordinated (that have the same definition as the extracted metal ions; in Example 1, Co and Ni) was 0.98. Next, a 10 M sodium hydroxide aqueous solution or a 10 M hydrochloric acid was added to adjust the pH of the mixed solution to a value shown in the column “pH during Mixing” of Table 1-1. Further, the solution was stirred at 25° C. for 30 minutes, and was left to stand at the same temperature for 1 hour. After verifying th...

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a Continuation of PCT International Application No. PCT / JP2024 / 009754 filed on Mar. 13, 2024, which claims priority under 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-050477 filed in Japan on Mar. 27, 2023. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The present invention relates to a metal extractant that extracts metal ions present in a water phase to an oil phase, a separation recovery method of metal ions using this metal extractant, and a compound.2. Description of the Related Art

[0003] Valuable metals such as noble metals or rare earth metals are essential elements for precision equipment, and stable supply and acquisition of the valuable metals with high purity is a big challenge. The valuable metals are typically mined as a mixture of plural kinds of metals. Therefore, the desired valuable metals need to be isolated and purified (high purity) from the mined mixture. In addition, the valuable metals that can be mined from mines are also limited, and thus a technique of recovering the valuable metals from industrial waste irrespective of mining is also important. In particular, along with the spread of electric vehicles, the amount of lithium ion batteries (LiB) wasted has been increasing every year. In LiB, a positive electrode active material including a metal element such as cobalt or nickel is used, and a significant increase in the demand for cobalt or nickel is also expected. In order to deal with the increase in the demand for valuable metals along with the trend, not only an increase in the amount of mining but also establishment of a technique of recycling waste LiB into a metal are desired.

[0004] As the isolated purification method of a desired valuable metal from the mined mixture and the method of recycling waste into a metal, a wet extraction method (solvent extraction method) is used. In the wet extraction method, in a case where an aqueous solution (water phase) including ions of a metal element (simply referred to as metal ions) and an organic phase including a metal extractant are brought into contact with each other, mixed, and left to stand to separate the two phases, the metal ions to which the metal extractant is coordinated are moved (extracted) to the organic phase. By extracting the organic phase, stripping the metal ions, and optionally purifying the metal ions, a desired metal can be isolated and purified, and the waste can be recycled as a (high-purity) metal.

[0005] As the metal extractant used for the wet extraction method, for example, JP2013-133537A describes an extractant including a mixture of a quaternary amine such as methyltri-n-octylammonium chloride and a phenol such as nonylphenol. In addition, JP2016-194105A describes a second mixed extractant including a phosphate-based extractant such as di-2-ethylhexyl phosphate and an oxime-based extractant such as 5-nonylsalicylaldoxime.SUMMARY OF THE INVENTION

[0006] Regarding the metal extractants described in JP2013-133537A and JP2016-194105A, JP2013-133537A and JP2016-194105A describe that, by using two kinds of specific extractants in combination for the wet extraction method, specific metal ions present in a water phase can be extracted and recovered to an oil phase. However, in a case where the two kinds of specific extractants are individually used for the wet extraction method without being used in combination, the selectivity (separability) of metal ions to be extracted is not sufficient, and a metal extractant having high initial selectivity where specific metal ions can be selectively separated and extracted from the water phase is desired for the wet extraction method.

[0007] Incidentally, the wet extraction method is normally performed under relatively mild conditions regarding extraction conditions (contact conditions between the water phase and the oil phase) such as a temperature or a pressure. From the viewpoint of reducing recycling costs, in general, the metal extractant is repeatedly used. However, in the wet extraction method, in a case where the water phase and the oil phase are brought into contact with each other, or in a case where metal ions extracted to the oil phase are stripped and isolated, a mixed solution of the water phase and the oil phase is set to a predetermined pH to be relatively strongly acidic or basic (for example, refer to JP2013-133537A and JP2016-194105A). In a case where the wet extraction method set to the pH conditions is repeatedly performed, even with a metal extractant having high selectivity for metal ions, the amount of metal ions extracted from the water phase to the oil phase gradually decreases. Therefore, a metal extractant having high durability where a recovery rate (extraction rate) of metal ions is maintained even in a case where the wet extraction method is repeatedly performed is desired.

[0008] However, JP2013-133537A and JP2016-194105A consider neither further improvement of the selectivity of metal ions nor suppression of a decrease in the recovery rate of metal ions during the repeated use.

[0009] An object of the present invention is to provide: a metal extractant that can extract specific metal ions present in a water phase to an oil phase with high selectivity and also has high durability; and a separation recovery method of metal ions using this metal extractant. In addition, an object of the present invention is to provide a compound that can be a metal extractant having the above-described excellent characteristics.

[0010] The present inventors conducted a thorough investigation on the metal extractant used for the wet extraction method and found that, by adopting a compound where a phenolic structure (structure represented by “benzene ring —OR1” in Formula (I) described below) is adopted, a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom is introduced into the benzene ring, and a nitrogen atom is not included, in a case where this compound is used as a metal extractant for a wet extraction method, a reduction in the amount of metal ions extracted can be suppressed for a long period of time while maintaining high selectivity (separability) of the metal ions.

[0011] The present invention has been completed as a result of repeated investigation based on the above findings.

[0012] That is, the above-described objects have been achieved by the following means.

[0013] <1> A metal extractant that extracts metal ions present in a water phase to an oil phase,

[0014] in which the metal extractant has a structure represented by Formula (I) and does not include a nitrogen atom,in Formula (I), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0016] X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom, and

[0017] a benzene ring in Formula (I) may form a fused ring.

[0018] <2> The metal extractant according to <1>,

[0019] in which the metal extractant includes a functional group selected from the following group G of functional groups,<Group G of Functional Groups>a carboxy group, a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group.

[0021] <3> The metal extractant according to <2>,

[0022] in which the functional group selected from the group G of functional groups is a phosphate group or a phosphonate group.

[0023] <4> The metal extractant according to any one of <1> to <3>,

[0024] in which the metal extractant has a hydrocarbon group having 9 or more carbon atoms.

[0025] <5> The metal extractant according to any one of <1> to <4>,

[0026] in which the metal extractant is represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0028] L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,

[0029] R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, and

[0030] a benzene ring in Formula (II) may form a fused ring.

[0031] <6> The metal extractant according to any one of <1> to <5>,

[0032] in which the metal ions are ions of a metal element belonging to Group 1 to Group 14 in a periodic table.

[0033] <7> The metal extractant according to any one of <1> to <6>,

[0034] in which the metal extractant is used for extraction and separation of two or more kinds of metal ions belonging to different groups in a periodic table among the metal ions.

[0035] <8> A separation recovery method of metal ions, the separation recovery method including:

[0036] mixing a water phase including plural kinds of metal ions with an oil phase including the metal extractant according to any one of <1> to <7>.

[0037] <9> A compound represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,

[0039] L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,

[0040] R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, and

[0041] a benzene ring in Formula (II) may form a fused ring.

[0042] An object of the present invention is to provide: a metal extractant that can extract specific metal ions present in a water phase to an oil phase with high selectivity and also has high durability; and a separation recovery method of metal ions using this metal extractant. In addition, an object of the present invention is to provide a compound that can be a metal extractant having the above-described excellent characteristics.

[0043] The above-described and other characteristics and advantageous effects of the present invention will be clarified from the following description appropriately with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 is a 1H-NMR chart showing a compound E-1 synthesized in Example.DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] In the present invention, in a case where a numerical range is shown to describe a content, physical properties, or the like of a component, any upper limit value and any lower limit value can be appropriately combined to obtain a specific numerical range in a case where an upper limit value and a lower limit value of the numerical range are described separately. In a case where a plurality of numerical ranges represented by “-” are set and described, the upper limit value and the lower limit value which form each of the numerical ranges are not limited to a specific combination described before and after “to” as a specific numerical range and can be set to a numerical range obtained by appropriately combining the upper limit value and the lower limit value of each numerical range. In the present invention, numerical ranges represented by “to” include numerical values before and after “to” as lower limit values and upper limit values.

[0046] In the present invention, the expression of a compound (for example, in a case where a compound is represented by an expression with “compound” added to the end) refers to not only the compound itself but also a salt or an ion thereof. In addition, this expression also refers to a derivative obtained by modifying a part of the compound, for example, by introducing a substituent into the compound within a range where the effects of the present invention do not deteriorate.

[0047] A substituent, a linking group, or the like (hereinafter, referred to as “substituent or the like”) that is not specified in the present invention regarding whether to be substituted or unsubstituted may have an appropriate substituent. Accordingly, even in a case where a YYY group is simply described in the present invention, this YYY group includes not only an aspect not having a substituent but also an aspect having a substituent. The same shall be applied to a compound which is not specified in the present specification regarding whether to be substituted or unsubstituted. Examples of a preferable substituent include groups selected from the substituent GZ described below.

[0048] In the present invention, in a case where a plurality of substituents or the like represented by a specific reference numeral are present or a plurality of substituents or the like are simultaneously or alternatively defined, the respective substituents or the like may be the same as or different from each other. In addition, unless specified otherwise, in a case where a plurality of substituents or the like are adjacent to each other, the substituents may be linked or fused to each other to form a ring.

[0049] In the present specification, “metal elements belonging to different groups in the periodic table of elements” in the specific metal ion group will be referred to as “different-group metal elements”, and particularly “different-group metal elements of the same period in the periodic table” will also be referred to as “same-period different-group metal elements”. In addition, “ions of the different-group metal elements” and “ions of the same-period different-group metal elements” will also be referred to as “different-group metal ions” and “same-period different-group metal ions”, respectively.

[0050] In the present invention, unless specified otherwise, “ppm” representing a content or the like is based on mass and represents “mass ppm”.[Metal Extractant]

[0051] A metal extractant according to an embodiment of the present invention includes a compound represented by Formula (I), and may include appropriately other components within a range where the effects of the present invention do not deteriorate. In addition, the metal extractant according to the embodiment of the present invention may include other compounds (other metal extractants) that function as extractants of metal ions other than the compound represented by Formula (I). However, the compound represented by Formula (I) exhibits the above-described excellent characteristics as the metal extractant as described below. Therefore, it is preferable that the metal extractant according to the embodiment of the present invention includes the compound represented by Formula (I) alone. In the present invention, the meaning of the metal extractant according to the embodiment of the present invention including the compound represented by Formula (I) alone includes an aspect where only the compound represented by Formula (I) is included and an aspect where a content of the other metal extractants with respect to a total mass including the compound represented by Formula (I) is 10% by mass or less.

[0052] In addition, each of forms of the metal extractant according to the embodiment of the present invention and the compound represented by Formula (I) is not particularly limited, and may be a solid such as powder or a granule or may be a liquid (solution) in which the substance is dissolved in an organic solvent.

[0053] The metal extractant according to the embodiment of the present invention has a function of extracting metal ions present in a water phase to an oil phase, and can be suitably used particularly for a wet extraction method. By using the metal extractant according to the embodiment of the present invention in the wet extraction method, even in a case where the compound represented by Formula (I) is included alone and even in a case where the metal extractant is used for a long period of time, specific metal ions present in the water phase can be extracted to the oil phase with high selectivity and high recovery rate. In particular, the metal extractant can extract specific metal ions from plural kinds of metal ions present in the water phase to the oil phase with high selectivity and high recovery rate.

[0054] In the present invention, as the metal ions that can be extracted to the oil phase among plural kinds of metal ions present in the water phase, ideally, one kind of specific metal ions can be used. However, two or more kinds of metal ions can also be used. Even in a case where two or more kinds of metal ions are included, one kind of metal ions among the two or more kinds of metal ions can be extracted (separated and recovered) with higher selectivity and with higher recovery rate than those of the other metal ions (including metal ions extracted to the oil phase). For example, while extracting, as ions of valuable metal elements, two or more kinds of different-group metal ions, for example, two or more kinds of metal ions belonging to Group 1 to Group 14 in the periodic table, desirably two or more kinds of different-group metal ions, and particularly desirably cobalt ions and nickel ions that are the same-period different-group metal ions to the oil phase, one kind of metal ions among the two or more kinds of metal ions can be extracted to the oil phase with high selectivity and high recovery rate.

[0055] Since the same-period different-group metal ions have similar physical behaviors and similar chemical behaviors, it is not easy to separate and recover any one kind of metal ions among the same-period different-group metal ions with high selectivity. However, in the present invention where the compound represented by Formula (I) is used as the metal extractant, while extracting the same-period different-group metal ions having similar physical behaviors and similar chemical behaviors, in particular, metal ions belonging to Group 9 (in particular, cobalt ions) and metal ions belonging to Group 10 (in particular, nickel ions) that are required along with the recent rapid spread of lithium ion batteries, one kind of metal ions among the two or more kinds of metal ions can be recovered with high selectivity and high recovery rate. Therefore, the present invention can largely contribute to further spread of electric vehicles and construction of a sustainable society.

[0056] In addition, in the present invention, being capable of extracting metal ions with high recovery rate with high selectivity represents that only one specific kind of metal ions among plural kinds of metal ions present in the water phase can be extracted. In addition, in a case where two or more kinds of metal ions are extracted to the oil phase, being capable of extracting metal ions with high selectivity represents that specific metal ions can be extracted and separated from the other metal ions such that, among the two or more kinds of extracted metal ions, a ratio of the amount of specific metal ions (typically one kind) to be extracted to the total amount of the other metal ions extracted [(the amount of the specific metal ions extracted) / (the total amount of the other metal ions extracted) is 1.5 or more (separability, selection ratio). The ratio (selection ratio) is preferably 3.0 or more, more preferably 4.5 or more, and particularly preferably 8.0 or more. The upper limit thereof is not particularly limited, but may be, for example, 30.

[0057] In the present invention, the above-described ratio (selection ratio) refers to a ratio that is achieved in a case where the metal extractant according to the embodiment of the present invention is initially used for the wet extraction method. On the other hand, in the metal extractant according to the embodiment of the present invention, high selectivity can be maintained even in a case where the metal extractant is repeatedly used for the wet extraction method and is continuously used for a long period of time. For example, in a case where a metal extractant is used 10 times for the wet extraction method (separation extraction operation) in Examples described below, a selection ratio is preferably 1.5 or more and more preferably 4.5 or more.

[0058] In addition, in the present invention, being capable of extracting metal ions with high recovery rate represents that the metal ions can be extracted such that, regarding metal ions (specific metal ions to be extracted) extracted in the maximum amount among the two or more kinds of extracted metal ions, a ratio of the amount of the metal ion extracted to the oil phase to the content of the metal ions (before the extraction) in the water phase [(the amount of the metal ions extracted to the oil phase) / (the content of the metal ions in the water phase] is 60% or more. The above-described ratio (recovery rate) is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more. The upper limit is not particularly limited and is ideally the total amount (100%) of the metal ions present in the water phase. For example, the upper limit is preferably 99% or less.

[0059] In the present invention, the above-described ratio (recovery rate) refers to a ratio that is achieved in a case where the metal extractant according to the embodiment of the present invention is initially used for the wet extraction method. On the other hand, the metal extractant according to the embodiment of the present invention has excellent durability. Therefore, high recovery rate can be maintained even in a case where the metal extractant is repeatedly used for the wet extraction method and is continuously used for a long period of time. For example, in a case where a metal extractant is used 10 times for the wet extraction method (separation extraction operation) in Examples described below, a recovery rate is preferably 70% or more and more preferably 85% or more.(Compound Represented by Formula (I))

[0060] The metal extractant according to the embodiment of the present invention consists of a compound having a (chemical) structure represented by Formula (I) and does not include a nitrogen atom in the structure (molecule) (also referred to as the compound according to the embodiment of the present invention). This compound has excellent characteristics as the metal extractant as described above.

[0061] The compound according to the embodiment of the present invention does not include a nitrogen atom. In the present invention, the compound not having a nitrogen atom represents that an atom group forming the compound does not include a nitrogen atom, for example, any of the phenolic structure or the substituent does not include a nitrogen atom. Examples of the substituent including a nitrogen atom include an amino group, an imino group (—NRN1—, —C═NRN1), and a group consisting of a nitrogen-containing aromatic ring or a nitrogen-containing aliphatic ring. RN1 in the imino group represents a hydrogen atom or a substituent. The substituent is, for example, a group selected from a substituent GZ described below, and typical examples thereof include an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and a hydroxy group.

[0062] The compound according to the embodiment of the present invention having high selectivity and high durability can be used, for example, repeatedly and continuously over a long period of time as a metal extractant for the wet extraction method. Any of the number of times (number of times of use) the compound according to the embodiment of the present invention can be repeatedly used for the wet extraction method or a period of time in which the compound according to the embodiment of the present invention can be continuously used for the wet extraction method cannot be uniquely determined depending on various conditions in the wet extraction method, stripping conditions of metal ions, purification conditions for appropriate purification during reuse, and the like. For example, the number of times of use in the batch type wet extraction method can be 5 or more and is preferably 10 or more. The continuous use time in the continuous type wet extraction method can be 12 hours or longer and is preferably 24 hours or longer. On the other hand, the upper limits of the number of times of use and the continuous use time can be appropriately determined depending on not only the above-described conditions but also selection ratio and recovery rate. For example, the number of times of use can be 100 or less, and from the viewpoint that a high selection ratio and a high recovery rate in the above-described ranges can be achieved, is preferably 50 or less and more preferably 30 or less. In addition, the continuous use time can be 168 hours or shorter, and from the viewpoint that a high selection ratio and a high recovery rate in the above-described ranges can be achieved, is preferably 48 hours or shorter and more preferably 36 hours or shorter.

[0063] In the compound represented by Formula (I), a benzene ring in Formula (I) may form a fused ring. Examples of the compound that form a fused ring include a compound represented by Formula (IC). In Formula (IC), a represents an atomic group (not including a nitrogen atom) that forms a fused ring with the benzene ring in Formula (IC).

[0064] The atomic group that can be used as a only needs to be an atomic group that can form a fused ring with the benzene ring in Formula (IC), and examples thereof include an atomic group that can form a fused ring not including a nitrogen atom. The ring that can be formed by a with the benzene ring (two carbon atoms) in Formula (IC) is not particularly limited, and may be an aliphatic ring or an aromatic ring or may be a hydrocarbon ring or a heterocycle (excluding a ring including a nitrogen atom). Further, the formed ring itself may be a monocycle or a polycycle. Specific examples of the ring that is formed by a include a cycloalkyl group, an aryl group, and a heterocyclic group in the substituent GZ described below.

[0065] In the present invention, a compound not including a, that is, the compound represented by Formula (I) is preferable.

[0066] In Formulae (I) and (IC), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent.

[0067] In the present invention, as a preferable first aspect of the atom or the like that can be used as R1, a hydrogen atom or a metal atom is preferable, and a hydrogen atom is more preferable. On the other hand, as a preferable second aspect of the atom or the like that can be used as R1, a monovalent substituent is preferable.

[0068] As the metal atom that can be used as R1, an atom that can form a salt of a phenolic hydroxyl group may be used, and a monovalent metal atom is preferable. The metal atom that can be used as R1 is typically present as a metal ion. Examples of the metal atom include a metal atom belonging to Group 1 or Group 2 in the periodic table. Among these, a metal atom belonging to Group 1 is preferable, and lithium, sodium, or potassium is more preferable.

[0069] The monovalent substituent that can be used as R1 is not particularly limited, a substituent not including a nitrogen atom is selected, and examples thereof include a group (a substituent not including a nitrogen atom) selected from the substituent GZ described below. As the monovalent substituent, for example, a hydrocarbon group such as an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or an aralkyl group, a heterocyclic group is preferable, an alkyl group or an aryl group is more preferable, and an alkyl group is still more preferable.

[0070] Each of the alkyl group and the alkyl group in the alkenyl group, the alkynyl group, and the aralkyl group that can be used as R1 is not particularly limited, may be a straight chain, a branched chain, or a cyclic chain, and is preferably a straight chain.

[0071] The total number of carbon atoms (hereinafter, also simply referred to as the number of carbon atoms) forming the monovalent substituent that can be used as R1, in particular, the hydrocarbon group is not particularly limited irrespective of the description of the substituent GZ described below. The number of carbon atoms in each of the groups is appropriately determined in a range of, for example, 1 to 30. As a preferable first aspect of the number of carbon atoms in the monovalent substituent that can be used as R1, the number of carbon atoms is preferably 1 to 12 (corresponding to a short-chain alkyl group and a medium-chain alkyl group), more preferably 1 to 6 (corresponding to a short-chain alkyl group), and still more preferably 1 to 4 (corresponding to a short-chain alkyl group). As a preferable second aspect of the number of carbon atoms in the monovalent substituent that can be used as R1, the number of carbon atoms is preferably 9 to 20 (corresponding to a medium-chain alkyl group and a long-chain alkyl group), more preferably 10 to 18, and still more preferably 12 to 16.

[0072] In Formulae (I) and (IC), X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom. This substituent does not typically include a nitrogen atom.

[0073] A preferable first aspect of the monovalent substituent that can be used as X is an aspect where the heteroatom is directly bonded to the benzene ring in Formula (I) or Formula (IC). In this aspect, the heteroatom in the monovalent substituent is preferably a sulfur atom or a phosphorus atom and can also further include an oxygen atom. A preferable second aspect of the monovalent substituent that can be used as X is an aspect where the heteroatom is not directly bonded to the benzene ring in Formula (I) or Formula (IC). In this aspect, the heteroatom in the monovalent substituent is preferably an oxygen atom. In the substituent of the second aspect, the linking portion such as the atom or the linking group that is directly bonded to the benzene ring in the Formula (I) or Formula (IC) is not particularly limited. For example, an atom that does not correspond to any of the heteroatom or a nitrogen atom or a linking group (not including a nitrogen atom) where an atom other than the heteroatom is a bonding portion can be used, examples thereof include a group obtained by removing a hydrogen atom from a group selected from the substituent GZ described below. Among these, a carbon atom is preferable.

[0074] The number of kinds of heteroatoms in the monovalent substituent that can be used as X is not particularly limited. For example, the number of kinds can be 1 or more, and is preferably 2 or 3, and more preferably 2. Examples of a combination of two or more kinds of heteroatoms include a combination of a phosphorus atom and an oxygen atom and / or a sulfur atom.

[0075] The number of atoms in the monovalent substituent that can be used as X is not particularly limited, and is appropriately determined depending on the chemical structure of X and the like. For example, the number of heteroatoms can be 1 to 12 and is preferably 2 to 8 and more preferably 2 to 5.

[0076] In the monovalent substituent that can be used as X, the heteroatom may be present at any position of the monovalent substituent, for example, may be present in an atomic chain forming the monovalent substituent or at a terminal thereof. In the present invention, an aspect where one heteroatom is present at a terminal of an atomic chain forming the substituent and is bonded to the benzene ring in Formula (I) or Formula (IC), or an aspect where one heteroatom forms a carbonyl group and is bonded to the benzene ring in Formula (I) or Formula (IC) is preferable.

[0077] The monovalent substituent that can be used as X is not particularly limited as long as it includes the heteroatom, and examples thereof include a substituent that includes the heteroatom and does not include a nitrogen atom among the substituents in the substituent GZ described below. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, each of the functional groups in the group G of functional groups described below is preferable. Examples of a monovalent substituent that can be used as a preferable first aspect among the functional groups in the group G of functional groups include a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group. Examples of a monovalent substituent that can be used as a preferable second aspect include a carboxy group.

[0078] In the compound represented by Formula (I) or Formula (IC), the monovalent substituent is used as X as described above. Therefore, this compound is a non-polymerizable compound having one structure represented by Formula (I) or Formula (IC) where the structure is not a repeating unit. Therefore, the compound represented by Formula (I) or Formula (IC) does not adopt a structure where a plurality of structures represented by Formula (I) or Formula (IC) are linked to each other through X, for example, a linear structure or a cyclic or tubular structure.

[0079] The compound represented by Formula (I) or Formula (IC) can be formed by appropriately combining R1, X, and a in the formula, and is preferably formed by combining preferable examples of the respective reference numerals.

[0080] Note that the compound represented by Formula (I) or Formula (IC) may be a basic compound, but it is preferable that the compound represented by Formula (I) or Formula (IC) corresponds to an acidic compound having at least one active hydrogen atom, that is, an acidic metal extractant from the viewpoint of exhibiting excellent selectivity and high durability as the metal extractant. Examples of the active hydrogen atom in the compound include a hydroxy group (including a phenolic hydroxy group and a hydroxy group bonded to a phosphorus atom or a sulfur atom), a carboxy group and an active hydrogen atom in a sulfanyl group. The active hydrogen atom may be present in any of a ring formed by R1, X, or a, and is preferably present in R1 or X. The number of hydroxy groups present in the compound may be 1 or more, and can be 1 to 4, and is preferably 1 or 2.

[0081] In the compound represented by Formula (I) or Formula (IC), a bonding position of an —OR1 group and X to the benzene ring is not particularly limited. For example, X may be present at any of the 2-position (o-), 3-position (m-), or 4-position (p-) with respect to the OR1 group and preferably at the 2-position from the viewpoint that metal ions can be stably coordinated and the selectivity and the durability of the metal extractant can be improved.

[0082] In the compound represented by Formula (IC), the position where the ring formed by a is bonded to the benzene ring is not particularly limited as long as it does not inhibit the bonding of the —OR1 group and X to the benzene ring. For example, the ring formed by a may be any of the 2- and 3-positions, the 3- and 4-positions, the 4- and 5-positions, or the 5- and 6-positions with respect to the —OR1 group, is preferably bonded to a position away from the —OR1 group and X, and is more preferably bonded to the 4- and 5-positions in a case where X is bonded to the 2-position.

[0083] In the present invention, the compound represented by Formula (I) is preferably a compound represented by Formula (II) from the viewpoints of the selectivity and the durability of the metal extractant. Any of the compound represented by Formula (II) or a compound represented by Formula (IIC) does not include a nitrogen atom as in the compound represented by Formula (I) or Formula (IC).

[0084] In Formula (II), R1 is the same as R1 in Formula (I).

[0085] In addition, in the compound represented by Formula (II), a benzene ring in Formula (II) may form a fused ring as in the compound represented by Formula (I). That is, the compound where the benzene ring in Formula (I) forms a fused ring is represented by, for example, Formula (IIC). In Formula (II), a represents an atomic group (not including a nitrogen atom) that forms a fused ring with the benzene ring in Formula (TIC), and is specifically the same as a in Formula (IC).

[0086] In the present invention, a compound not including a, that is, the compound represented by Formula (II) is preferable.

[0087] In Formula (II) and Formula (IIC), a -L-R2 group is a preferable aspect of the monovalent substituent that can be used as X in Formulae (I) and (IC), and is formed by L and R2.

[0088] Here, L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom. R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms.

[0089] The divalent linking group that can be used as L only needs to be a linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom. This linking group is not particularly limited, and examples thereof include an oxygen atom, a sulfur atom, a carbonyl group, a phosphate linking group (—OP(═O)(ORC)—O— group), a phosphonate linking group (—P(═O)(ORC)—O— group), a phosphinate linking group (—P(═O)RC—O— group) (note that each of the phosphate linking group, the phosphonate linking group, and the phosphinate linking group includes a linking group where at least one oxygen atom in each of the groups is substituted with a sulfur atom), and a group including a combination thereof. Here, RC represents a hydrogen atom or a substituent, and is the same as RC in the group G of functional groups described below.

[0090] In the group including the combination, the number of groups, linking groups, or atoms to be combined is not particularly limited and, for example, can be 2 to 15 and is preferably 2 to 10 and more preferably 2 to 5. In addition, the number of kinds of groups, linking groups, or atoms to be combined is not particularly limited and, for example, can be 2 or more and is preferably 2 or 3. Examples of the group including the combination include a carbonyloxy group, a sulfonate linking group (—S(═O)2—O—), and a sulfinate linking group (—S(═O)—O—) (note that each of the sulfonate linking group and the sulfinate linking group includes a linking group where at least one oxygen atom in each of the groups is substituted with a sulfur atom).

[0091] The number of linking atoms in the linking group is not particularly limited, and is preferably 15 or less, more preferably 10 or less, still more preferably 6 or less, and still more preferably 4 or less. The lower limit is 1 or more. The number of linking atoms refers to the minimum number of atoms that connect the benzene ring and R2 in Formula (II) or Formula (TIC). The number of atoms (number of constituent atoms) forming the linking group cannot be uniquely determined depending on RC of the phosphate linking group or the like. For example, the number of atoms forming the linking group can be 1 to 100 and is preferably 1 to 40 and more preferably 1 to 24.

[0092] A preferable first aspect of the monovalent substituent that can be used as L is an aspect where the heteroatom is directly bonded to the benzene ring in Formula (II) or Formula (IIC). In this aspect, the heteroatom in the divalent linking group is preferably a sulfur atom or a phosphorus atom and can also further include an oxygen atom. On the other hand, a preferable second aspect of the divalent linking group that can be used as L is an aspect where the heteroatom is not directly bonded to the benzene ring in Formula (II). In this aspect, the heteroatom in the divalent linking group is preferably an oxygen atom. In the linking group of the second aspect, the linking portion such as the atom or the linking group that is directly bonded to the benzene ring in the Formula (II) or Formula (IIC) is the same as that of the preferable second aspect of the monovalent substituent that can be used as X in Formulae (I) and (IC), and is preferably a carbon atom.

[0093] The number of kinds of heteroatoms and the number of atoms in the divalent linking group that can be used as L are not particularly limited, and are preferably the same as the number of kinds of heteroatoms and the number of atoms in the monovalent substituent that can be used as X.

[0094] In the linking group that can be used as L, the heteroatom may be present at any position of the divalent linking group, for example, may be present in an atomic chain forming the divalent linking group or at a terminal thereof. In the present invention, an aspect where one heteroatom is present at a terminal of an atomic chain forming the linking group and is bonded to the benzene ring in Formula (II) or Formula (IIC), or an aspect where one heteroatom forms a carbonyl group and is bonded to the benzene ring in Formula (II) or Formula (IIC) is preferable.

[0095] The divalent linking group that can be used as L is not particularly limited as long as it includes the heteroatom and does not include a nitrogen atom, and examples thereof include a substituent that includes the heteroatom and does not include a nitrogen atom among the substituents in the substituent GZ described below. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, a structure forming each of the functional groups in the group G of functional groups described below is preferable. Examples of a divalent linking group that can be used as a preferable first aspect among the functional groups in the group G of functional groups include a structures forming each of a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group, specifically, a structure obtained by removing RC or RD from each of the groups. Examples of a divalent linking group that can be used as a preferable second aspect include a structure forming a carboxy group, specifically, a carbonyloxy group.

[0096] The hydrocarbon group that can be used as R2 is not particularly limited, and examples thereof include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, and an aralkyl group. From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, an alkyl group is preferable.

[0097] Each of the alkyl group and the alkyl group in the alkenyl group, the alkynyl group, and the aralkyl group that can be used as R2 is not particularly limited, may be a straight chain, a branched chain, or a cyclic chain, and is preferably a branched chain from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level. In a case where the alkyl group or the like that can be used as R2 is a branched chain, the number of branched carbon atoms present in the group is not particularly limited as long as it is 1 or more. A preferable first aspect of the number of branched carbon atoms present in the branched chain is 1 or 2. On the other hand, a preferable second aspect of the number of branched carbon atoms present in the branched chain is 3 or more, can be 3 to 10, and is preferably 3 to 8 and more preferably 4 to 7.

[0098] The total number of carbon atoms (simply referred to as the number of carbon atoms) forming the hydrocarbon group that can be used as R2 is not particularly limited as long as it is 8 or more, and is preferably 9 to 20 from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level. As a preferable first aspect of the number of carbon atoms in the hydrocarbon group that can be used as R2, the number of carbon atoms is more preferably 8 to 11, still more preferably 8 to 10, and still more preferably 8 or 9 from the viewpoints of the selectivity and the durability of the metal extractant. On the other hand, as a preferable second aspect of the number of carbon atoms in the hydrocarbon group that can be used as R2, the number of carbon atoms is more preferably 10 to 24 and still more preferably 12 to 20 from the viewpoint that the durability can be further improved while maintaining high selectivity of the metal extractant.

[0099] In a case where RC in the linking group L represents a hydrocarbon group, R2 may be the same as or different from this hydrocarbon group.

[0100] The compound represented by Formula (II) is a non-polymerizable compound as in the compound represented by Formula (I) or Formula (IC).

[0101] The compound represented by Formula (II) or Formula (TIC) can be formed by appropriately combining R1, L, R2, and a in the formula, and is preferably formed by combining preferable examples of the respective reference numerals.

[0102] Note that the compound represented by Formula (II) or Formula (IIC) preferably includes at least one active hydrogen atom as in the compound represented by Formula (I) or Formula (IC). The active hydrogen atom may be present in any of a ring formed by R1, L, R2, or α, and is preferably present in R1 or L. The number of hydroxy groups present in the compound is the same as that of the compound represented by Formula (I) or Formula (IC).

[0103] In the compound represented by Formula (II) or Formula (IIC), a bonding position of an —OR1 group and -L-R2 to the benzene ring is not particularly limited, and is the same as the bonding position of the —OR1 group and X to the benzene ring in the compound represented by Formula (I) or Formula (IC).

[0104] In the compound represented by Formula (IIC), the position where the ring formed by a is bonded to the benzene ring is not particularly limited, and is the same as the position where the ring formed by a is bonded to the benzene ring in the compound represented by Formula (I) or Formula (IC).

[0105] It is preferable that the compound according to the embodiment of the present invention (including the compound represented by Formula (II)) has a functional group selected from the group G of functional groups. It is preferable that a coordinating functional group coordinated to metal ions to be extracted contributes to improvement of the selectivity and the durability of the metal extractant including the compound according to the embodiment of the present invention.

[0106] As long as the compound according to the embodiment of the present invention includes the following functional group in a molecule, a position at which the following functional group is introduced and bonded is not particularly limited. For example, the functional group may be bonded to the benzene ring in each of the formulae, may be bonded to a ring formed by any atom group a, or may be introduced as R1 or into R1. In the present invention, from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the functional group is introduced as X or into X in Formula (I) or Formula (IC) or is introduced as -L-R2 in Formula (II) or Formula (IIC).

[0107] From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, the functional group in the compound according to the embodiment of the present invention is preferably a phosphate group or a phosphonate group among the group G of functional groups, and more preferably a phosphate group or a phosphonate group where all of XA, XB, and Z represent oxygen atoms.<Group G of Functional Groups>

[0108] A carboxy group, a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group (—S(═O)2ORC), and a sulfinate group (—S(═O)ORC)

[0109] The phosphate group, the phosphonate group, and the phosphinate group are typically represented by —OP(═O)(ORC)2, —P(═O)(ORC)2, and —P(═O)(ORC)RD, respectively. The phosphate group, the phosphonate group, and the phosphinate group as the functional groups in the present invention refer to groups represented by —XA—P(=Z)(XBRC)2, —P(═Z)(XBRC)2, and —P(═Z)(XBRC)RD, respectively. Here, XA represents an oxygen atom or a sulfur atom and preferably an oxygen atom. XB represents an oxygen atom or a sulfur atom, and preferably an oxygen atom. Z represents an oxygen atom or a sulfur atom and preferably an oxygen atom. A combination of XA, XB, and Z in each of the groups is not particularly limited and can be appropriately set. In each of the phosphate group, phosphonate group, and the phosphinate group, it is preferable that all of XA, XB, and Z represent oxygen atoms.

[0110] In the present invention, RC and RD in the coordinating functional group each independently represent a hydrogen atom or a substituent. The substituent that can be used as RC and RD are not particularly limited, and examples thereof include groups selected from the substituent GZ described below. In particular, as the substituent that can be used as RC and RD, from the viewpoint of solubility in the oil phase, a hydrocarbon group such as an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group is preferable. The hydrocarbon group that can be used as RC and RD is not particularly limited, and is preferably the same as the hydrocarbon group that can be used as R2 in Formula (II) and more preferably an alkyl group.

[0111] Two RC's in each of the phosphate group and the phosphonate group may be the same as or different from each other. In a case where two RC's are different, it is preferable that one RC represents a hydrogen atom and the other RC represents a hydrocarbon group. In a case where the functional group is introduced as the -L-R2 group in Formula (II) or Formula (IIC), assuming that the phosphate group and the phosphonate group include one hydrocarbon group, this hydrocarbon group is analyzed as R2. In addition, it is preferable that, in phosphinic acid, RC represents a hydrogen atom and RD represents a hydrocarbon group.

[0112] The carboxy group may form a salt. In addition, in a case where RC represents a hydrogen atom, the phosphate group, the phosphonate group, the sulfonate group, the phosphinic acid, or the sulfinate group may form a salt. A cation that forms a salt is not particularly limited, and examples thereof include a metal cation, in particular, a metal cation belonging to Group 1 or Group 2.

[0113] A preferable first aspect that can be used as two RC's and RC and RD is an aspect (an aspect of an acidic functional group) where, in each of the functional groups, one RC represents a hydrogen atom and the remaining RC or RD represents a substituent. In this aspect, each of the functional groups includes one hydroxyl group, and one monovalent substituent can be used as R1. On the other hand, a preferable second aspect that can be used as two RC's and RC and RD is an aspect (an aspect of an acidic functional group) where, in each of the functional groups, RC and RD represent a substituent. In this aspect, two substituents may be the same as or different from each other and are preferably a hydrocarbon group. In this second aspect, each of the functional groups includes a hydroxyl group, and a hydrogen atom or a metal element is used as R1.

[0114] The compound according to the embodiment of the present invention only needs to include at least one functional group selected from the group G of functional groups, or may include two or more functional groups.

[0115] From the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the compound according to the embodiment of the present invention includes a hydrocarbon group having 9 or more carbon atoms.

[0116] As long as the compound according to the embodiment of the present invention including the hydrocarbon group having 9 or more carbon atoms includes a hydrocarbon group having 9 or more carbon atoms, a position where this hydrocarbon group is introduced and bonded is not particularly limited. For example, the functional group may be bonded to the benzene ring in each of the formulae, may be bonded to a ring formed by any atom group a, or may be introduced as R1 or into R1. In the present invention, from the viewpoint that the selectivity and the durability of the metal extractant can be simultaneously improved at a higher level, it is preferable that the hydrocarbon group having 9 or more carbon atoms is introduced as X or into X in Formula (I) or Formula (IC) or is introduced as -L-R2 in Formula (II) or Formula (IIC), it is more preferable that the hydrocarbon group having 9 or more carbon atoms is introduced into the functional group selected from the group of functional groups, and it is still more preferable that the hydrocarbon group having 9 or more carbon atoms is introduced as RC in ORC in the phosphate group and the phosphonate group or as RD in the phosphinate group among the functional groups.

[0117] Examples of the hydrocarbon group having 9 or more carbon atoms include hydrocarbon groups having 9 or more carbon atoms among the hydrocarbon groups that can be used as R2.

[0118] The number of hydrocarbon groups having 9 or more carbon atoms in the compound according to the embodiment of the present invention is not particularly limited, can be 1 or more, and is preferably 1 or 2.

[0119] In a case where the compound according to the embodiment of the present invention includes two hydrocarbon groups having 9 or more carbon atoms, a preferable first aspect of a combination of the hydrocarbon groups is an aspect where a hydrocarbon group having 12 or more carbon atoms and a hydrocarbon group having 8 to 11 carbon atoms are combined. In this aspect, the number of hydrocarbon groups having 12 or more carbon atoms is more preferably 14 or more. The upper limit of carbon atoms is not particularly limited, but is, for example, preferably 24 or less and more preferably 20 or less. A preferable second aspect of a combination of the hydrocarbon groups is an aspect where hydrocarbon groups having 12 or more carbon atoms are combined. In this aspect, the number of carbon atoms in the hydrocarbon group having 12 or more carbon atoms is the same as the number of carbon atoms in the first aspect.

[0120] In the compound according to the embodiment of the present invention, the second aspect also includes an aspect where the two hydrocarbon groups having 9 or more carbon atoms are changed to hydrocarbon groups having 8 to 11 carbon atoms (referred to as a third aspect for convenience of description).

[0121] On the other hand, in the first aspect to the third aspect regarding the combination of the two hydrocarbon groups in the compound according to the embodiment of the present invention, a molecular structure of the hydrocarbon group is not particularly limited. From the viewpoints of the selectivity and the durability of the metal extractant, a combination of hydrocarbon groups having a branched structure is preferable, and a combination of alkyl groups having a branched structure is more preferable. In addition, in each of the aspects, the kind of the hydrocarbon group is not particularly limited. The same (kind) of substituents may be combined, or different (kinds) of substituents may be combined. As the combination of the same substituents, a combination of alkyl groups is preferable from the viewpoints of the selectivity and the durability of the metal extractant.

[0122] The compound according to the embodiment of the present invention may function as a monodentate ligand for specific metal ions (metal ions to be extracted) present in the water phase, but preferably functions as a multidentate ligand from the viewpoints of the selectivity and the durability.

[0123] The molecular weight of the compound according to the embodiment of the present invention is not particularly limited, and, for example, can be 150 to 50,000. From the viewpoints of solubility in the oil phase, the molecular weight is preferably 200 to 10,000 and more preferably 250 to 1,000. In the present invention, in a case where the compound according to the embodiment of the present invention has a polymer chain, unless specified otherwise, the molecular weight of the oligomer refers to the number-average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC).—Measurement of Molecular Weight—

[0124] Regarding a method of measuring the molecular weight of the oligomer, basically, a value measured using a method under the following condition 1 or condition 2 (preferred) is used. In this case, an appropriate eluent may be selected and used depending on the kind of the oligomer.(Condition 1)Column: Connect two TOSOH TSKgel Super AWM-H (trade name, manufactured by

[0126] Tosoh Corporation)

[0127] Carrier: 10 mM LiBr / N-methylpyrrolidone

[0128] Measurement temperature: 40° C.

[0129] Carrier flow rate: 1.0 ml / min

[0130] Sample concentration: 0.1% by mass

[0131] Detector: refractive index (RI) detector(Condition 2)Column: A column obtained by connecting TOSOH TSKgel Super HZM-H, TOSOH

[0133] TSKgel Super HZ4000, and TOSOH TSKgel Super HZ2000 (all of which are trade names,

[0134] manufactured by Tosoh Corporation)

[0135] Carrier: tetrahydrofuran

[0136] Measurement temperature: 40° C.

[0137] Carrier flow rate: 1.0 ml / min

[0138] Sample concentration: 0.1% by mass

[0139] Detector: refractive index (RI) detector

[0140] The pKa of the compound according to the embodiment of the present invention is not particularly limited, an appropriate value can be adopted, and a value of 1.0 to 14 is preferable. For example, in a case where the compound according to the embodiment of the present invention preferably includes an active hydrogen atom as a hydroxy group bonded to a phosphorus atom in X of Formula (I) or Formula (IC) or in L of Formula (II) or Formula (IIC), the pKa has a small value and specifically is likely to be in a range of 2.0 to 7.5. On the other hand, in a case where the compound according to the embodiment of the present invention includes a hydrogen atom as R1 of each of the formulae and does not include an active hydrogen atom in X of Formula (I) or Formula (IC) or in L of Formula (II) of Formula (IIC), the pKa is a large value and specifically is likely to be in a range of 8.0 to 14. The pKa can be measured using a neutralization titration method.

[0141] The compound according to the embodiment of the present invention may include a substituent, and examples of the substituent that may be included in the compound include groups (excluding a group including a nitrogen atom) selected from the substituent GZ described below.

[0142] The compound according to the embodiment of the present invention can be synthesized with reference to a well-known synthesis method, for example, a synthesis method described in Examples described below.

[0143] Specific examples of the compound according to the embodiment of the present invention include the following compounds in addition to compounds synthesized in Examples, but the present invention is not limited thereto.—Substituent GZ—

[0144] The substituent GZ includes: an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylheptyl, benzyl, 2-ethoxyethyl, or 1-carboxymethyl); an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, or oleyl); an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, or phenyl-ethynyl); a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms; for example, cyclopropyl, cyclopentyl, cyclohexyl, or 4-methylcyclohexyl; the meaning of an alkyl group described in the present invention typically includes a cycloalkyl group but, here, an alkyl group and a cycloalkyl group are distinguished from each other); an aryl group (preferably an aryl group having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, or 3-methylphenyl); an aralkyl group (preferably an aralkyl group having 7 to 23 carbon atoms, for example, benzyl or phenethyl); a heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms and more preferably a 5- or 6-membered heterocyclic group having at least one oxygen atom, sulfur atom, or nitrogen atom. The heterocyclic group includes an aromatic heterocyclic group and an aliphatic heterocyclic group. 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); an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, or benzyloxy); an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, or 4-methoxyphenoxy); a heterocyclic oxy group (a group in which an —O— group is bonded to the above-described heterocyclic group); an alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, or dodecyloxycarbonyl); an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, or 4-methoxyphenoxycarbonyl); a heterocyclic oxycarbonyl group (a group in which an —O—CO— group is bonded to the above-described 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 (—NH2), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, or anilino); a sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl or N-phenylsufamoyl); an acyl group (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, or nicotinoyl); an acyloxy group (an alkylcarbonyloxy group, an alkenylcarbonyloxy group, an alkynylcarbonyloxy group, or a heterocyclic carbonyloxy group, preferably an acyloxy group having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, or nicotinoyloxy); an aryloyloxy group (preferably an aryloyloxy group having 7 to 23 carbon atoms, for example, benzoyloxy or naphthoyloxy); a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl or N-phenylcarbamoyl); an acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, for example, acetylamino or benzoylamino); an alkylthio group (preferably an alkylthio group having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, or benzylthio); an arylthio group (preferably an arylthio group having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, or 4-methoxyphenylthio); a heterocyclic thio group (a group in which an —S— group is bonded to the above-described heterocyclic group); an alkylsulfonyl group (preferably an alkylsulfonyl group having 1 to 20 carbon atoms, for example, methylsulfonyl or ethylsulfonyl); an arylsulfonyl group (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, or 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, or triethoxysilyl); an aryloxysilyl group (preferably an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl); a phosphoryl group (preferably a phosphate group having 0 to 20 carbon atoms, for example, —OP(═O)(R′)2); a phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, —P(═O)(R′)2); a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R′)2); a phosphonate group (preferably a phosphonate group having 0 to 20 carbon atoms, for example, —PO(OR′)2); a sulfo group (a sulfonate group), a carboxy group, a hydroxy group, a sulfanyl group, a cyano group, and a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). R1 represents a hydrogen atom or a substituent (preferably a group selected from the substituent GZ).

[0145] In addition, each group exemplified in the substituent GZ may be further substituted with the substituent GZ.

[0146] The alkyl group, the alkylene group, the alkenyl group, the alkenylene group, the alkynyl group, the alkynylene group, and / or the like may be cyclic or chained, may be linear or branched.[Separation Recovery Method of Metal Ions]

[0147] A separation recovery method of metal ions according to an embodiment of the present invention (hereinafter, also referred to as the separation recovery method according to the embodiment of the present invention) is a method of mixing a water phase including plural kinds of metal ions and an oil phase including the metal extractant according to the embodiment of the present invention. As a result, the specific metal ions to which the metal extractant according to the embodiment of the present invention is coordinated can be moved (extracted) to be separated and recovered from the water phase to the oil phase with high selectivity and high recovery rate. Further, even in a case where the metal extractant according to the embodiment of the present invention that has been used once is repeatedly used (reused), a decrease in selectivity and recovery rate during an initial use is suppressed, and specific metal ions can be separated and recovered with high selectivity and high recovery rate. In addition, even in a case where the metal extractant according to the embodiment of the present invention is in contact with the water phase for a long period of time, a decrease in initial selectivity and initial recovery rate is suppressed, and specific metal ions can be separated and recovered with high selectivity and high recovery rate. That is, even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, specific metal ions present in the water phase can be extracted to the oil phase while suppressing a decrease in initial high selectivity and initial high recovery rate. Here, the metal ions to be extracted to the oil phase may be a part of the plural kinds of metal ions in the water phase or may be all kinds of different-group metal ions in the water phase.

[0148] Even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, as ions of a valuable metal element, one kind of metal ions can be extracted to the oil phase with high selectivity and high recovery rate. In this case, one kind of metal ions among two or more kinds of different-group metal ions, for example, two or more kinds of different-group metal ions belonging to Group 1 to Group 14 in the periodic table can be extracted to the oil phase with high selectivity and high recovery rate. In particular, even in a case where separation recovery method according to the embodiment of the present invention is repeatedly performed or is continuously performed for a long period of time, one kind of metal ions among two or more kinds of different-group metal ions belonging to Group 8 to Group 12 in the periodic table, particularly desirably, cobalt ions and nickel ions that are same-period different-group metal ions can be extracted to the oil phase with high selectivity and high recovery rate.

[0149] The present inventors found that the metal extractant according to the embodiment of the present invention has the characteristics and function in which, while extracting two or more kinds of metal ions among plural kinds of metal ions (groups) present in the water phase to the oil phase together in the wet extraction method, one kind of metal ions can be extracted to the oil phase with high selectivity and high recovery rate over a long period of time, and applies the separation recovery method according to the embodiment of the present invention to the new use where two or more kinds of metal ions, in particular, different-group metal ions are separated and recovered.<Water Phase>

[0150] Water formed in the water phase is not particularly limited, and (super) pure water, ion exchange water, or the like can be used.

[0151] The metal ions in the water phase may include metal ions of at least two metal elements belonging to Group 1 to Group 14 in the periodic table, preferably includes at least two kinds of metal ions belonging to Group 3 to Group 14, and may include metal ions belonging to Group 15 to Group 17.

[0152] In the present invention, it is preferable that two or more kinds of metal ions belonging to Group 1 to Group 14 are included, it is more preferable that two or more kinds of metal ions belonging to Group 3 to Group 14 are included, and it is still more preferable that ions of at least one kind of a transition metal element (transition metal element belonging to Group 3 to Group 12) are included. In an aspect including at least one transition metal element, it is preferable that two or more kinds of metal ions belonging to Group 4 to Group 12 are included, it is more preferable that two or more kinds of metal ions belonging to Group 4 to Group 10 are included, it is still more preferable that two or more kinds of metal ions belonging to Group 8 to Group 12 are included, it is still more preferable that two or more kinds of metal ions belonging to Group 9 to Group 12 are included, and it is most preferable that two or more kinds of metal ions belonging to Group 9 and Group 10 are included. The metal ions belonging to each of the groups are not particularly limited, metal ions belonging to the fourth to sixth periods in the periodic table are preferable, and metal ions belonging to the fourth period or the fifth period are more preferable. In addition, the number of kinds of the metal ions is not particularly limited as long as it is 2 or more. For example, the number of kinds of the metal ions can be 2 to 15 and is preferably 2 to 8 and more preferably 2 to 5.

[0153] A combination of the plurality of metal ions is not particularly limited, and examples of a combination of groups include a combination including Group 9 and Group 10, a combination including Group 9 and Group 12, a combination including Group 4 and Group 9, a combination including Group 8 and Group 10, a combination including Group 7, Group 9, and Group 10, and a combination of Group 7, Group 8, Group 9, and Group 10.

[0154] In the present invention, the number of kinds of metal ions belonging to each of the groups may be two or more but, from the viewpoint of exhibiting high selectivity, is preferably one.

[0155] Specific examples of the combination of the metal ions include a combination including Co and Ni, a combination including Co and Zn, a combination including Fe and Ni, a combination including Zr and Rh, a combination including Mn, Co, and Ni and a combination including Mn, Fe, Co, and Ni.

[0156] The plural kinds of metal ions in the water phase may include the same group of metal ions, or may include different-group metal ions. The number of kinds of the different-group metal ions in the water phase may be 2 or more and, for example, is preferably 2 to 4 and more preferably 2.

[0157] The metal element belonging to each of the groups is not particularly limited, and an appropriate atom can be used. Examples of the metal element belonging to each of the groups are as follows.

[0158] Preferable examples of a metal element belonging to Group 1 include Li, Na, Rb, and Cs.

[0159] Preferable examples of a metal element belonging to Group 2 include Mg, Ca, Sr, and Ba.

[0160] Preferable examples of a metal element belonging to Group 3 include Sc and Y.

[0161] Preferable examples of a metal element belonging to Group 4 include Ti, Zr, and Hf.

[0162] Preferable examples of a metal element belonging to Group 5 include V, Nb, and Ta.

[0163] Preferable examples of a metal element belonging to Group 6 include Cr, Mo, and W.

[0164] Preferable examples of a metal element belonging to Group 7 include Mn and Tc.

[0165] Preferable examples of a metal element belonging to Group 8 include Fe, Ru, and Os.

[0166] Preferable examples of a metal element belonging to Group 9 include Co, Rh, and Ir.

[0167] Preferable examples of a metal element belonging to Group 10 include Ni, Pd, and Pt.

[0168] Preferable examples of a metal element belonging to Group 11 include Cu, Ag, and Au.

[0169] Preferable examples of a metal element belonging to Group 12 include Zn, Cd, and Hg.

[0170] Preferable examples of a metal element belonging to Group 13 include Al, Ga, In, and Tl.

[0171] Preferable examples of a metal element belonging to Group 14 include Ga, Sn, and Pb.

[0172] Preferable examples of a metal element belonging to Group 15 include Sb and Bi.

[0173] A metal element belonging to Group 16 is not particularly limited, and preferable examples thereof include Te.

[0174] The plural kinds of metal ions can be appropriately prepared and, for example, various metal salts (salts of typical elements with inorganic acids such as nitric acid or sulfuric acid or organic acids such as acetic acid), a mixture of mined metals (ion), a recovery from metal waste, other waste such as a metal recovery from a waste battery (LiB), or a mixture thereof can be used. Examples of the metal recovery from the waste LiB include recoveries obtained using a well-known method such as a wet process or electrolysis.

[0175] A total content of the plural kinds of metal ions in the water phase is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 1,000,000 mass ppm and is preferably 1,000 to 100,000 mass ppm, more preferably 1,000 to 80,000 mass ppm, and still more preferably 2,000 to 30,000 mass ppm.

[0176] A total content of the metal ions belonging to Group 8 to Group 12 among the metal ions is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 80,000 mass ppm and is preferably 1,000 to 60,000 mass ppm and more preferably 2,000 to 30,000 mass ppm.

[0177] A total content of the metal ions belonging to Group 3 to Group 7 and Group 13 to Group 16 among the metal ions is not particularly limited and is appropriately set. For example, the total content can be 1,000 to 60,000 mass ppm and is preferably 1,000 to 30,000 mass ppm.

[0178] A content of the metal ions belonging to each of the groups is not particularly limited and is appropriately set. For example, the content can be 1,000 to 60,000 mass ppm and is preferably 1,000 to 50,000 mass ppm and more preferably 2,000 to 25,000 mass ppm. In a case where two or more kinds of metal ions belonging to each of the groups are present, the content of the metal ions belonging to each of the groups is the total content.

[0179] In the present invention, in a case where the water phase includes different-group metal ions, the content of the metal ions belonging to one group may be more than or less than a content of the metal ions belonging to another group. In the separation recovery method according to the embodiment of the present invention, the metal ions can be separated and recovered multiple times with high selectivity and high recovery rate. Therefore, the contents of the metal ions belonging to different groups do not need to be set at a specific ratio. For example, a mass ratio of the content of metal ions belonging to a specific group (for example, metal ions extracted in the maximum amount) to the content of metal ions belonging to another group (for example, metal ions other than the metal ions extracted in the maximum amount (including metal ions that are not extracted) [the content of the metal ions belonging to the specific group:the content of the metal ions belonging to the other group] can be, for example, 100:1 to 10,000 and is preferably 100:10 to 5,000, more preferably 100:50 to 1,000, and still more preferably 100:80 to 130.

[0180] The pH of the water phase is not particularly limited and is appropriately set. For example, the pH of the water phase is preferably 0.1 to 10 and more preferably 2.0 to 10 in consideration of the solubility of the metal ions, the formation of complex ions, and the like.

[0181] The pH of the water phase can be adjusted, for example, using an acid or an alkali. As the acid, a well-known acid can be used without any particular limitation, and examples thereof include an inorganic acid such as sulfuric acid, hydrochloric acid, nitric acid, or phosphoric acid and an organic acid such as formic acid, acetic acid, oxalic acid, organic phosphoric acid, or organic sulfonic acid. As the alkali, a well-known alkali can be used without any particular limitation, and examples thereof include an inorganic alkali and an organic alkali. Among these, an inorganic alkali is preferable. Examples of the inorganic alkali include a hydroxide of a metal belonging to Group 1 or Group 2, a metal alkali such as a carbonate, ammonia water, and ammonium chloride. Examples of the organic alkali include an organic ammonium salt.

[0182] The temperature of the water phase is not particularly limited and can be, for example, 10° C. to 60° C.

[0183] The water phase may optionally include, for example, a ligand coordinated to metal ions or a compound that generates the ligand.

[0184] The water phase can be prepared by dissolving metal ions in water. Preparation conditions of the water phase are not particularly limited. For example, the preparation temperature can be 10° C. to 60° C.

[0185] The water phase may include a masking agent in addition to the above-described metal ions. As the masking agent, various well-known agents can be used without any particular limitation. Examples of the masking agent include a monodentate ligand such as ammonia or a chelating agent such as dithizone.<Oil Phase>

[0186] In the separation recovery method according to the embodiment of the present invention, the oil phase (organic phase) including one kind or two or more kinds of the metal extractants according to the embodiment of the present invention is used for the above-described water phase. In the present invention, even in a metal extractant that is recovered and purified after use (also referred to as a recovered product) and a metal extractant that is used for a long period of time (both of which will be collectively referred to as a used product), high selectivity and high recovery rate of an unused metal extractant (also referred to as an unused product) are maintained. Therefore, the metal extractant according to the embodiment of the present invention in the oil phase may be the unused product or the used product or may be a combination of the unused product and the used product. In a case where the unused product and the used product are combined, the mixing ratio is not particularly limited and is appropriately determined.

[0187] In addition, the metal extractant used in the separation recovery method according to the embodiment of the present invention may include other metal extractants as described above, but preferably includes the compound according to the embodiment of the present invention alone.

[0188] The metal extractant according to the embodiment of the present invention exhibits solubility in an organic solvent, is present in the oil phase, is coordinate-bonded to metal ions present in the vicinity of an interface between the water phase and the oil phase, and has a function of moving the metal ions to the oil phase. In the present invention, the solubility in the organic solvent refers to a property in which the metal extractant is soluble in the organic solvent in a content described below.

[0189] The organic solvent for forming the oil phase is not particularly limited, and an appropriate organic solvent can be used. Examples of the organic solvent include an alcohol solvent, an ether solvent, a hydrocarbon-based solvent (an aromatic solvent or an aliphatic solvent), and a halogen solvent. In particular, a hydrocarbon-based solvent is preferable, various solvents as components separated from petroleum are more preferable, and hydrocarbon-based solvents of aromatic groups, paraffin, naphthene, kerosine, gasoline, naphtha, heating oil, and light oil are still more preferable.

[0190] The content of the metal extractant in the oil phase is appropriately set in consideration of the content of the 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 millimole / L (mM), and is preferably 50 to 1,000 millimole / L and more preferably 100 to 500 millimole / L.

[0191] The temperature of the oil phase is not particularly limited and can be, for example, 10° C. to 60° C.

[0192] The oil phase may include appropriate components in addition to the acidic metal extractant according to the embodiment of the present invention.

[0193] The oil phase can be prepared by dissolving the metal extractant in the organic solvent. Preparation conditions of the oil phase are not particularly limited. For example, the preparation temperature can be 10° C. to 60° C.<Contact and Mixing>

[0194] In the separation recovery method according to the embodiment of the present invention, the water phase and the oil phase described above are mixed and left to stand.

[0195] In this case, mixing conditions and standing conditions are not particularly limited and can be appropriately set. For example, mixing can be performed using various mixing devices. Examples of a method using the mixing device include a method using a magnetic stirrer (stirrer tip), a method using a mechanical stirrer, and a method using a mixer. Stirring conditions (a stirring rate, a stirring time, and the like) only need to be conditions (conditions where the metal extractant is coordinate-bonded to the metal ions) where the water phase and the oil phase can be mixed, and are appropriately set depending on the combination of the metal ions and the metal extractant, and the mixing temperature, and the mixing device. For example, as a stirring rate, a rotation speed of a magnetic stirrer or the like can be 80 rpm to 200 rpm. For example, a stirring time is not uniquely determined depending on stirring conditions and the like, and can be, for example, 10 minutes to 24 hours. A mixing temperature is not particularly limited, and can be, for example, 10° C. to 60° C.

[0196] Standing conditions can be appropriately set without any particular limit as long as they are conditions where the water phase and the oil phase can be separated into two layers. A standing time in the wet extraction method is typically set to 10 minutes to 24 hours after stopping the mixing. A standing temperature is not particularly limited, and can be, for example, 10° C. to 60° C.

[0197] During the mixing of the water phase and the oil phase, a mixing ratio between the water phase and the oil phase is appropriately set depending on a metal ion concentration, a concentration of the metal ions, the content (concentration) of the metal extractant, and the like, and is not uniquely determined. For example, in a case where the water phase and the oil phase that satisfy the respective concentrations are mixed, the ratio of the oil phase to 100 mL of the water phase can be 50 to 2,000 mL and is preferably 80 to 1,000 mL and more preferably 80 to 200 mL. On the other hand, focusing on the metal ions present in the water phase, it is preferable that the oil phase is mixed at a ratio of 0.5 to 20 mole times of the metal extractant to the total content (moles) of the metal ions, and it is more preferable that the oil phase is mixed at a ratio of 0.5 to 10 mole times of the metal extractant to the total content (moles) of the metal ions. In addition, the content of the metal extractant with respect to the total content of the metal ions to which the metal extractant can be coordinated (also referred to as the mixing amount; a ratio of the number of moles of the metal extractant to the total number of moles of the metal ions: molar ratio) can be, for example, 0.5 to 10.0 equivalents, and is preferably 0.5 to 6.0 equivalents. Here, the metal ions to which the metal extractant can be coordinated refers to metal ions that are coordinated to the metal extractant and are extracted to the oil phase.

[0198] During the mixing of the water phase and the oil phase, the pH of the mixing system can be adjusted. Here, the pH that is set for specific metal ions to be extracted is not uniquely determined and is appropriately determined in consideration of the pKa of the metal extractant, the complex formation constants of the metal extractant and the metal ions, the number of metal ions to be coordinated, and the like. The pH of the mixing system is preferably 0.01 to 14, more preferably, for example, 0.1 to 10. It is preferable that the pH of the mixing system is set according to the metal extractant to be used from the viewpoints of the selectivity and the recovery rate. For example, in a case where the pKa of the metal extractant (the compound according to the embodiment of the present invention) is the above-described small value, in the above-described range, the pH of the mixing system is preferably 0.5 to 9.0, more preferably 1.0 to 8.5, and still more preferably 2.0 to 8.0. On the other hand, in a case where the pKa of the metal extractant is the above-described large value, in the above-described range, the pH of the mixing system is preferably 5.0 to 12.0, more preferably 7.0 to 12.0, and still more preferably 7.0 to 11.0.

[0199] The adjustment of the pH can be performed using the acid or the alkali described above, an aqueous solution thereof, or the like, and one preferable aspect is an aspect where ammonia or an ammonium salt is not used.

[0200] In a case where the pH of the mixing system is adjusted during the mixing of the water phase and the oil phase, the mixing of the water phase and the oil phase and the standing after the mixing are performed after adjusting the pH.

[0201] In a two-phase separated fluid (a solvent extraction phase or a solvent extraction system) where the water phase and the oil phase are phase-separated that is obtained by mixing the water phase and the oil phase and leaving the mixture to stand, the water phase and the oil phase are phase-separated into layers and present in a state where they are in contact with each other. The metal ions to which the metal extractant is coordinate-bonded among the above-described plural kinds of metal ions are present (moved) in the oil phase.

[0202] In addition, the number of kinds of the metal ions extracted to the oil phase is ideally 1 but may also be 2 or more. In this case, for example, the number of kinds of the metal ions can be 2 to 10 and is preferably 2 to 6 and more preferably 2 or 3. The two or more kinds of metal ions extracted to the oil phase among the plural kinds of metal ions are not particularly limited and, for example, are preferably the same as the above-described two or more kinds of different-group metal ions (combination) in the water phase.

[0203] In the separation recovery method according to the embodiment of the present invention, using a simple method of mixing the water phase and the oil phase with each other and leaving the mixture to stand, specific metal ions among plural kinds of metal ions can be separated, recovered, and extracted with high selectivity and high recovery rate over a long period of time. In particular, while extracting ions of two or more kinds of metal elements, one kind of metal ions can be separated and recovered to an oil phase with high selectivity and high recovery rate over a long period of time. Further, even in a case where the used product is used as the metal extractant, specific metal ions can be separated and recovered with selectivity and recovery rate that are higher or equal to those of the unused product.

[0204] The one kind of metal ions that can be separated and recovered with high selectivity and high recovery rate are not uniquely determined depending on the group or the period of the metal ions, the content thereof, the kind of the metal extractant, and the like. For example, in a case where metal ions belonging to Group 9 and metal ions belonging to Group 10 are extracted to the oil phase, the metal ions belonging to Group 9 can be separated and recovered with high selectivity and high recovery rate. In particular, in a case where Co ions as metal ions belonging to Group 9 and Ni ions as metal ions belonging to Group 10 are extracted, the Co ions can be separated and recovered with high selectivity and high recovery rate. In addition, in a case where metal ions belonging to Group 9 and metal ions belonging to Group 12 are extracted to the oil phase, the metal ions belonging to Group 12 can be separated and recovered with high selectivity and high recovery rate. Further, in a case where metal ions belonging to Group 8 and metal ions belonging to Group 10 are extracted to the oil phase, the metal ions belonging to Group 8 can be separated and recovered with high selectivity and high recovery rate.

[0205] In the separation recovery method according to the embodiment of the present invention, as described above, one kind or two or more kinds of metal ions among plural kinds of metal ions present in the water phase can be extracted and recovered to the oil phase with high selectivity and high recovery rate. In particular, in the separation recovery method according to the embodiment of the present invention, while extracting ions of two or more kinds of metal elements, one kind of metal ions can be separated and recovered to the oil phase with high selectivity and high recovery rate. Therefore, by further subjecting the water phase including the two or more kinds of metal ions stripped from the oil phase to the separation recovery method according to the embodiment of the present invention, the selectivity of one kind of metal ions can be further improved without significant deterioration in recovery rate, and thus high-purity metal ions can be recovered with high recovery rate. Further, even in a case where the separation, recovery, and stripping is repeatedly performed multiple times or is continuously performed for a long period of time, metal ions can be extracted and recovered without deterioration in high selectivity and high recovery rate of the metal ions.

[0206] The separation recovery method according to the embodiment of the present invention can also be a method of extracting two or more kinds of metal ions.

[0207] In the separation recovery method according to the embodiment of the present invention, the metal extractant alone can be coordinated to metal ions to extract the metal ion to the oil phase. Therefore, the water phase and the oil phase do not need to include a compound that acts to extract metal ions in cooperation with the metal extractant according to the embodiment of the present invention, such as, a compound that is coordinated to metal ions or a compound that forms a ligand. For example, the water phase and the oil phase do not need to include a well-known metal extractant. In the separation recovery method according to the embodiment of the present invention, typically, the water phase including the specific metal ions as an essential component and the oil phase including the metal extractant according to the embodiment of the present invention as an essential component are used.

[0208] The separation recovery method according to the embodiment of the present invention may include steps other than the step of mixing the water phase and the oil phase with each other and leaving the mixture to stand. Examples of the other steps include a step of preliminarily mixing (pre-mixing) the water phase and the oil phase before adjusting the pH, a step of stripping (isolating) metal ions from the oil phase obtained in the step of mixing the water phase and the oil phase with each other and leaving the mixture to stand (step of stripping metal ions from the oil phase to recover a metal extractant), a step of recovering the stripped metal ions as a compound (salt), a step of purifying the stripped metal ions or the compound thereof, a step of purifying the recovered metal extractant, and a step of removing ions of metal elements belonging to Group 1 or Group 2 in the periodic table of elements in advance. As a method of stripping (isolating) the metal ions from the oil phase, a well-known method can be applied without any particular limitation. For example, the different-group metal ions can be stripped by adjusting the liquid phase to be acidic, for example, pH of 2 to 4 using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. By stripping the metal ions from the oil phase, the oil phase including the metal extractant can be recovered. In addition, as a method of recovering the stripped metal ions as a compound, a well-known method can be applied without any particular limitation.

[0209] The separation recovery method according to the embodiment of the present invention includes not only a method using the metal extractant (unused product) according to the embodiment of the present invention but also a method using the metal extractant (used product) recovered in the recovery step alone or in combination with the unused product, and a method using the oil phase (including the recovered metal extractant) obtained in the stripping step (method of bringing the oil phase into contact with a newly prepared water phase).

[0210] The separation recovery method according to the embodiment of the present invention may be performed through a batch process or a continuous process.

[0211] In the present invention, the metal extractant has high durability. Therefore, for example, in a batch process, using a non-treated water phase and the recovered metal extractant (oil phase), the number of times of process (the number of times of contact between the water phase and the oil phase) can be increased to repeat the process. The number of times the process can be repeated cannot be uniquely determined depending on contact conditions, a metal ion concentration, and the like as described above, and can be set to be, for example, 5 or more within a range where the selection ratio and the extraction rate are satisfied.

[0212] The separation recovery method using the repeated separation and recovery through the batch process is not particularly limited as long as it is a method using the recovered metal extractant (used product). For example, in one method, the first separation recovery method is performed using the metal extractant (unused product) according to the embodiment of the present invention, subsequently the second separation recovery method of bringing the oil phase (including the used product of the metal extractant according to the embodiment of the present invention) recovered in the first separation recovery method into contact with an unused water phase to mix them is performed, and the third or subsequent separation recovery method is repeatedly performed appropriately using the same method as the second separation recovery method. Specifically, a method described in Examples can be performed. The oil phase recovered in each of the separation recovery methods can also be appropriately purified. For example, a method of bringing metal ions mixed in the oil phase into contact with a water solvent to remove the metal ions can be used. Conditions in the first and second or subsequent separation recovery methods are as described above.

[0213] On the other hand, for example, in the continuous process method, a contact time between the water phase and the oil phase (time for which the oil phase is in contact with the water phase to be circulated) can be set to be long. A time for which the contact process can be performed cannot be uniquely determined depending on contact conditions, a metal ion concentration, the amount of the water phase to be circulated, and the like, and can be set to be, for example, 12 hours or longer within a range where the selection ratio and the extraction rate are satisfied. In the continuous process, the amount of the water phase to be used and circulated can also be set to be more than a mixing ratio between the water phase and the oil phase.

[0214] A device for performing the separation recovery method according to the embodiment of the present invention is not particularly limited, and a well-known device can be used. Examples of the device include a separating funnel and a mixer settler. In addition, a contact and mixing device including a liquid feeding device such as a flow synthesis system or an emulsion flow system can also be used. As conditions for contact, mixing, and standing in the continuous process, each of the above-described conditions can be applied.EXAMPLES

[0215] Hereinafter, the present invention will be described in more detail based on Examples but is not limited to these examples.

[0216] “Parts” and “%” that represent compositions in the following Examples are mass-based unless otherwise specified. In the present invention, “room temperature” refers to 25° C.[Preparation and Synthesis of Compounds]

[0217] Compounds shown below were synthesized and prepared.

[0218] A commercially available product manufactured by Tokyo Chemical Industry Co., Ltd. was used as a compound E-3 (octyl salicylate) shown below, and a commercially available product manufactured by ChemBridge Corporation was used as a compound E-5 (2-butoxybenzoic acid). In addition, a commercially available product of ACORGAM 5640 (trade name, manufactured by Solvay S.A.) was used as a compound T-1 (5-nonylsalicylaldoxime), a commercially available product of KELEX-100 (trade name, manufactured by Nordmann, Rassmann GmbH) was used as a compound T-2 (7-(4-ethyl-2-methyloctyl)-8-quinolinol), and a commercially available product manufactured by FUJIFILM Wako Pure Chemical Corporation was used as a compound T-3 (4-nonylphenol).<Synthesis of Compound E-1>

[0219] A compound E-1 was synthesized as follows.

[0220] Specifically, 15.1 g of N-chlorosuccinimide (manufactured by FUJIFILM Wako Pure Chemical Corporation) and 230 g of toluene (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, and were stirred at room temperature. N-chlorosuccinimide was dispersed in toluene without being dissolved. While cooling the three-necked eggplant flask with ice, 30.0 g of bis(2-chlorohexyl) phosphite (manufactured by Sigma-Aldrich Co. LLC) was slowly added dropwise. After completion of the dropwise addition, the reaction solution was returned to room temperature and was stirred for 5 hours. The obtained reaction solution was filtered to remove insoluble matter, and the solvent was distilled off under reduced pressure. While optionally adding hexane, the filtration and the distillation under reduced pressure were repeated to obtain 31.2 g (yield: 97%) of a light yellow liquid (intermediate E1).

[0221] Next, 8.3 g of phenol (manufactured by FUJIFILM Wako Pure Chemical Corporation) and 105 g of toluene were added to a 300 mL three-necked eggplant flask, and were stirred at room temperature. 19.1 g of pyridine (manufactured by FUJIFILM Wako Pure Chemical Corporation), 9.8 g of 4-dimethylaminopyridine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the light yellow liquid (intermediate E1) obtained in the previous stage were added to the obtained solution, and were stirred at 60° C. for 12 hours. The obtained reaction solution was added to water, and organic matter was extracted with hexane. The hexane solution was cleaned with a saturated sodium hydrogen carbonate solution and water, and the solvent was distilled off under reduced pressure. Silica gel chromatography (eluent: hexane) was performed on the obtained crude product to obtain 16.9 g of a colorless transparent liquid (intermediate E2).

[0222] Next, 40.0 g of tetrahydrofuran (super dehydrated, manufactured by FUJIFILM Wako Pure Chemical Corporation) was added to a 500 mL three-necked eggplant flask, and the solution was cooled at −78° C. using an acetone / dry ice bath. 64 mL of a 1.0 M hexane solution of lithium diisopropylamide (manufactured by Sigma-Aldrich Co. LLC) was added dropwise, and the reaction solution was stirred for 30 minutes. Next, a solution consisting of 16.9 g of the colorless transparent liquid (intermediate E2) obtained in the previous stage and 55.3 g of tetrahydrofuran was added dropwise while maintaining the temperature of the reaction solution at −50° C. or lower. After completion of the dropwise addition, the reaction solution was stirred for 1 hour and was stirred at 0° C. for 5 hours. 100 mL of a saturated ammonium chloride solution was added, the reaction solution was extracted with ethyl acetate, and the solvent was distilled off under reduced pressure. As a result, a crude product was obtained. Silica gel chromatography (eluent: hexane) was performed on the obtained crude product to obtain 20.7 g of a compound E-1 (yield: 65%, two steps).

[0223] The compound E-1 synthesized as described above was identified as follows.

[0224] That is, the compound E-1 was dissolved in deuterated chloroform, and 1H-NMR was measured (device: BRUKER 400). The obtained chart is shown in FIG. 1.

[0225] δ (ppm): 10.28 (1H, br s, OH), 7.43 (1H, t, J=7.1 Hz), 7.34 (1H, ddd, J=14.2, 7.7, 1.7 Hz), 6.97 (1H, t, J=7.7 Hz), 6.91 (1H, ddd, J=14.1, 7.4, 1.7 Hz), 4.05-3.82 (4H, m, OCH2—), 1.60-1.16 (18H, m), 0.90-0.82 (12H, m)

[0226] As a result, the obtained compound was identified to have the above-described structure represented by compound E-1.<Synthesis of Compound E-2>

[0227] A compound E-2 was synthesized as follows.

[0228] Specifically, 18.1 g of the compound E-1, 130 g of 2-ethylhexanol (manufactured by FUJIFILM Wako Pure Chemical Corporation), and 3.5 g of sodium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, and were stirred at room temperature. Next, the reaction solution was heated to 160° C. and stirred for 12 hours. 150 g of purified water was added to the obtained reaction solution, and the reaction solution was stirred for 20 minutes. After cleaning the obtained solution with toluene, 4 M hydrochloric acid was added to the water phase until the pH was 2 or higher. Next, by performing the toluene extraction and distilling off the solvent under reduced pressure, 11.1 g (yield: 89%) of the compound E-2 was obtained.<Synthesis of Compound E-4>

[0229] A compound E-4 was synthesized as follows.

[0230] Specifically, 15.5 g of the compound E-1, 10.2 g of butyl bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), and 200 g of dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Corporation) were added to a 500 mL three-necked eggplant flask, were stirred at room temperature, and were cooled with ice. 15.5 g of potassium carbonate (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added, and the reaction solution was stirred at 40° C. for 7 hours. The obtained reaction solution was cast into a 3 L Erlenmeyer flask including 1.5 L iced water, and was stirred at room temperature for 1 hour. The obtained solution was extracted with hexane, and the solvent was distilled off under reduced pressure. As a result, 15.4 g (yield: 91%) of a compound where a phenol group of compound E-1 was butylated was obtained.

[0231] The obtained compound was hydrolyzed under the same conditions as those of the hydrolysis reaction in the synthesis of the compound E-2. As a result, 9.9 g (yield: 88%) of a compound E-4 was obtained.<Synthesis of Compound E-6>

[0232] A compound E-6 was synthesized using the same method as that of the compound E-1, except that, during the synthesis of the compound E-1, 2-butyl-1-n-octanol was used instead of 2-ethylhexanol.[Preparation of Metal Ion-Containing Aqueous Solution]

[0233] 47.7 g of cobalt (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemicals Corporation) and 52.6 g of nickel (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemicals Corporation) were added to a 1 L measuring flask, were diluted with ultrapure water, and were stirred and dissolved at 40° C. to prepare a metal ion-containing aqueous solution (W1).

[0234] In addition, sulfates of a combination of metal ions shown in the column “Metal Ion Concentration in Water Phase before Extraction (ppm)” of Table 1-1 were dissolved in ultrapure water such that the amounts thereof used were changed to obtain the metal ion concentration shown in the same column. As a result, each of metal ion-containing aqueous solutions (W2) and (W3) was prepared.

[0235] The results of measuring the pH of the prepared metal ion-containing aqueous solutions (W1) to (W3) using a pH meter (SK-620 pH II, measured by SATOTECH) are shown below.

[0236] Metal ion-containing aqueous solution (W1): 6.5

[0237] Metal ion-containing aqueous solution (W2): 7.0

[0238] Metal ion-containing aqueous solution (W3): 6.2<Preparation of Metal Extractant Solution (Oil Phase)>

[0239] Each of the synthesized or prepared compounds (all of which were unused products) was added to a 100 mL measuring flask, and was diluted using IP SOLVENT 2835 (a paraffin-based solvent, manufactured by Idemitsu Kosan Co., Ltd.) at room temperature. As a result, metal extractant solutions (Y1) to (Y6) and (Yc1) to (Yc3) (concentration: 350 mM) including the compounds as metal extractants were prepared, respectively.Example 1

[0240] Using the metal ion-containing aqueous solution (W1) and the oil phase (Y1) the separation extraction operation (wet extraction method) of metal ions was repeated 10 times as described below.

[0241] 10 mL of the extractant solution (Y1) with respect to 10 mL of the prepared metal ion-containing aqueous solution (W1) was added to a 30 mL vial tube, and the mixture was stirred using a stirrer tip at 25° C. for 30 minutes (pre-mixing). In this case, the mixing amount (unit: equivalent) of the compound E-1 with respect to the total content of metal ions to be coordinated (that have the same definition as the extracted metal ions; in Example 1, Co and Ni) was 0.98. Next, a 10 M sodium hydroxide aqueous solution or a 10 M hydrochloric acid was added to adjust the pH of the mixed solution to a value shown in the column “pH during Mixing” of Table 1-1. Further, the solution was stirred at 25° C. for 30 minutes, and was left to stand at the same temperature for 1 hour. After verifying that the solution was separated into two layers of the organic phase (oil phase) and the water phase, the separated water phase was extracted, the separation and recovery of the metal ions was performed, and the oil phase was extracted to recover the metal extractant.

[0242] The pH of the mixed solution was measured using a pH meter (SK-620 pH II, manufactured by SATOTECH).

[0243] This way, the initial (first) separation extraction operation was performed, the metal ions extracted in each of Examples are shown in the column “Kind” of the column “Extracted Metal Ions” of Table 1-1, and the metal ions extracted in the maximum amount are shown in the column “Maximum Extracted Ions” of Table 1-1.

[0244] Next, in the initial separation extraction operation, 10 mL of purified water was added to 10 mL of the separated and extracted oil phase, 10 M hydrochloric acid was added to adjust the pH of the mixed solution to 1.0, and the reaction solution was stirred at room temperature for 30 minutes and was left to stand at the same temperature for 1 hour. After verifying that the solution was separated into two layers of the organic phase (oil phase) and the water phase, the separated oil phase was extracted. As a result, the metal extractant was separated and purified to recover the whole oil phase.

[0245] This way, using the recovered oil phase (including the recovered product of the metal extractant), the second separation extraction operation was performed using the same method as that of the initial separation extraction operation (at this time, the mixing amount was 0.98 equivalents). The oil phase recovered in the second separation extraction operation was processed using the same method as described above to recover the metal extractant by the separation and purification.

[0246] The second separation extraction operation and the separation purification operation of the metal extractant were further repeated 8 times, that is, was performed 10 times in total (all of the mixing amounts were 0.98 equivalents). In a case where the amount of the organic solvent in the recovered oil phase was insufficient, the amount of the solution including IP SOLVENT 2835 was adjusted to 10 mL.Examples 2 to 8 and Comparative Examples 1 to 3

[0247] The separation extraction operations of the metal ions according to Examples 2 to 8 and Comparative Examples 1 to 3 were repeatedly performed 10 times using the same method as that of Example 1, except that the metal ion-containing aqueous solution and the extractant solution were changed to a combination shown in the column “Water Phase” and the column “Oil Phase” of Table 1-1, and the pH during the mixing of the water phase and the oil phase was set to a value shown in the column “pH during Mixing” of Table 1-1.

[0248] The metal ions extracted in each of Examples are shown in the column “Kind” of the column “Extracted Metal Ions” of Table 1-1, and the metal ions extracted in the maximum amount are shown in the column “Maximum Extracted Ions” of Table 1-1.

[0249] In each of Examples and Comparative Examples, regarding each of the prepared water phases, each of the water phases recovered in the initial (first) separation extraction operation, and each of the water phases recovered in the tenth separation extraction operation, each of the contents of dissolved metal ions was determined using an inductively coupled plasma-optical emission spectrometer (ICP-OES) (Optima 7300 D (trade name), manufactured by Perkin Elmer Co., Ltd.). “,” in the metal ion concentration of the table represents a breakpoint of digits without representing a decimal point.

[0250] The measured value of the content of the dissolved metal ions prepared in each of the water phases prepared in Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase before Extraction (ppm)” of Table 1-1. In addition, the measured value of the content of the dissolved metal ions in each of the water phases recovered in the initial (first) separation extraction operation of Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase after Initial Extraction (ppm)” of Table 1-2, and the measured value of the content of the dissolved metal ions in each of the water phases recovered in the tenth separation extraction operation of Examples and Comparative Examples is shown in the column of “Metal Ion Concentration in Water Phase after Tenth Extraction (ppm)” of Table 1-2.<Evaluation 1: Evaluation of Extraction rate (Recovery Rate)>

[0251] In each of Examples and Comparative Examples, an extraction rate (unit: %) of metal ions extracted in the maximum extraction amount was calculated based on the following expression from a metal ion concentration CI in the prepared water phase (water phase before the first separation extraction operation) and a metal ion concentration C1 in the water phase after the first separation extraction operation or a metal ion concentration C10 in the water phase after the tenth separation extraction operation. The result is shown in the column “Initial Extraction Rate” or the column “Tenth Extraction Rate” of Table 1-2.

[0252] In the present test, as each of the extraction rates increases, the extractability (recovery power) of specific metal ions in each of the separation extraction operations is higher. In addition, as a difference between the initial extraction rate and the tenth extraction rate (initial extraction rate−tenth extraction rate) decreases, even in a case where the metal extractant is repeatedly used (the separation extraction operation is repeatedly performed), specific metal ions can be recovered while maintaining a high recovery rate of an unused metal extractant, and the metal extractant (compound used as the metal extractant) has higher durability.

[0253] In the present test, an initial extraction rate of 95% or more is pass, and a tenth extraction rate of 70% or more is pass.Initial⁢ Extraction⁢ rate⁢ (%)=[(CI-C⁢1) / CI]×100Tenth⁢ Extraction⁢ rate⁢ (%)=[(CI-C⁢10) / CI]×100<Evaluation 2: Evaluation of Selectivity (Separability)>

[0254] In each of Examples and Comparative Examples, the amounts (unit: ppm) of metal ions extracted were calculated based on the following formula from the metal ion concentration CI in the water phase before the first separation extraction operation and the metal ion concentration C1 in the water phase after the first separation extraction operation or the metal ion concentration C10 in the water phase after the tenth separation extraction operation, and the maximum amount (ppm) of the metal ions extracted was divided by the total amount CT (ppm) of the other metal ions extracted to calculate a selection ratio as a ratio between the amounts thereof extracted. The result is shown in the column “Initial Selection Ratio” or the column “Tenth Selection Ratio” of Table 1-2.

[0255] In the present test, as each of the selection ratios increases, characteristics (selectivity, separability) in which specific metal ions in each of the separation extraction operations are selectively extracted and recovered with respect to the other metal ions are higher. In addition, as the difference (Initial Selection Ratio−Tenth Selection Ratio) between the initial selection ratio and the tenth selection ratio decreases or as the tenth selection ratio further increases as compared to the initial selection ratio, even in a case where the metal extractant is repeatedly used (the separation extraction operation is repeatedly performed), specific metal ions can be selectively extracted and recovered while maintaining high selectivity of an unused metal extractant, and the metal extractant (compound used as the metal extractant) has higher durability from the viewpoint of the selectivity.

[0256] In the present test, an initial selection ratio of 1.5 or more is pass, and a tenth selection ratio of 1.5 or more is pass.Initial⁢ Selection⁢ Ratio=[(CI-C⁢1) / CT]×100Tenth⁢ Selection⁢ Ratio=[(CI-C⁢10) / CT]×100TABLE 1-1Metal Ion Concentration in WaterExtracted Metal IonspHOil PhaseWaterPhase before Extraction (ppm)MaximumduringMetalNo.PhaseCoNiZnFeKindExtracted IonsMixingExtractantExample 1W110,00011,00000Co, NiCo9.8Y1E-1Example 2W110,00011,00000Co, NiCo3.5Y2E-2Example 3W110,00011,00000Co, NiCo9.7Y3E-3Example 4W110,00011,00000Co, NiCo4.1Y4E-4Example 5W110,00011,00000Co, NiCo6.5Y5E-5Example 6W110,00011,00000Co, NiCo9.8Y6E-6Example 7W210,000012,0000Co, ZnZn7.5Y6E-6Example 8W3011,000011,000Ni, FeFe8.5Y6E-6ComparativeW110,00011,00000Co, NiCo6.8Yc1T-1Example 1ComparativeW110,00011,00000Co, NiCo10.3Yc2T-2Example 2ComparativeW110,00011,00000Co, NiCo9.9Yc3T-3Example 3TABLE 1-2Metal Ion Concentration in WaterInitialInitialMetal Ion Concentration in WaterTenthTenthPhase after Initial Extraction (ppm)ExtractionSelectionPhase after Tenth Extraction (ppm)ExtractionSelectionNo.CoNiZnFeRateRatioCoNiZnFeRateRatioExample 108,80000100%4.51,5009,1000085%4.5Example 206,20000100%2.12,3007,3000077%2.1Example 305,00000100%1.72,7006,5000073%1.6Example 408,90000100%4.83009,0000097%4.9Example 507,90000100%3.21,2008,3000088%3.3Example 609,80000100%8.35009,8000095%7.9Example 77,800000100%5.57,9000400097%5.5Example 808,70000100%4.808,800050095%4.8Comparative07,20000100%2.64,5008,9000055%2.6Example 1Comparative06,50000100%2.24,2008,1000058%2.0Example 2Comparative03,00000100%1.32,2004,1000078%1.1Example 3The following can be seen from the results and the like shown in Tables 1-1 and 1-2.In Comparative Examples 1 to 3 using T-1 to T-3 as metal extractants in the related art in the separation recovery of metal ions in the wet extraction method, the two kinds of metal ions present in the metal ion-containing aqueous solution (W1) were extracted to the oil phase. However, in Comparative Example 3 using the metal extractant T-3, regarding the metal ions (Co ions) extracted in the maximum amount, substantially the entire amount of Co ions were able to be extracted in the initial separation extraction operation, but a large amount of Ni was also extracted. Therefore, the initial selection ratio was low. On the other hand, in Comparative Examples 1 and 2 using the metal extractant T-1 or T-2, the tenth extraction rate was significantly lower than the initial extraction rate. Based on the above results, the metal extractants T-1 to T-3 were not able to be repeatedly used for the wet extraction method because a high selection ratio and durability were not able to be simultaneously achieved.

[0259] On the other hand, in all of Examples 1 to 8 where the compounds E-1 to E-6 according to the embodiment of the present invention were used as the metal extractants, two or kinds of metal ions among the metal ions present in the metal ion-containing aqueous solution were extracted to the oil phase. However, regarding the metal ions extracted in the maximum amount (Examples 1 to 6: Co ions, Example 7: Zn Ions, Example 8: Fe ions), substantially the entire amount of metal ions were able to be extracted in the initial separation extraction operation, and a high extraction rate of 73% or more was maintained even in the tenth separation extraction operation. Further, not only in the initial separation extraction operation but also in the tenth separation extraction operation, the metal ions extracted in the maximum amount were able to be extracted from the water phase to the oil phase with a high selection ratio with respect to the metal ions other than the metal ions extracted in the maximum amount. As a result, even in a case where the compound according to the embodiment of the present invention is recovered after being used for the wet extraction method and is reused multiple times for the wet extraction method, the selectivity and the recovery rate during the initial use can be maintained, and specific metal ions can be separated and recovered with high selectivity and high recovery rate.

[0260] In a case where the same experiment was performed using the same method as that of Examples 1 to 7 and Comparative Examples 1 to 3, except that the metal ion concentration in the water phase was reduced to ⅕, the same results were obtained.

[0261] It can be seen that, even in a case where the compound according to the embodiment of the present invention is repeatedly used as a metal extractant in the wet extraction method, metal ions present in the water phase can be separated and recovered with high selectivity and high recovery rate. Further, specific metal ions among two or more kinds of metal ions belonging to different groups having similar physical behaviors and similar chemical behaviors, in particular, one kind of metal ions among metal ions belonging to Groups 9 and 10 that can be recovered from waste LiB can be separated and recovered with high selectivity and high recovery rate. The details of the reason why the compound according to the embodiment of the present invention has the above-described excellent characteristics are not clear, but are presumed to be that the compound according to the embodiment of the present invention is not likely to be decomposed and deteriorate even after being exposed to conditions of the wet extraction method.

[0262] From the above results, it can be seen that, by stripping the oil phase obtained in each of Examples using a typical method and conditions, irrespective of the number of times of execution of the separation extraction operation, the metal ions can be separated and recovered to the oil phase simply with high selectivity, high recovery rate, and high productivity in a large recovery amount without deterioration in high selectivity.

[0263] Incidentally, in the technique of recovering specific metal ions from the water phase including a plurality of metal ions, it is generally difficult to recover the specific metal ions with high selectivity and recovery rate, and in a case where high selectivity is maintained, the recovery rate decreases. Therefore, in order to achieve a predetermined recovery rate, currently, it is required to perform the separation recovery operation multiple times. On the other hand, it can be seen that, even in a case where the metal extractant according to the embodiment of the present invention is used over a long period of time, using the simple method, one kind of metal ions among two kinds of different-group metal ions can be extracted from the water phase to the oil phase with high productivity, high selectivity, and high recovery rate. Therefore, in consideration of the current conditions, the technical significance of the present invention is high from the viewpoint that, through the stripping step or the like from the obtained oil phase, one kind of metal ions can be recovered simply and with high productivity and a small number of steps while further improving selectivity with high recovery rate and while further reusing the metal extractant.

[0264] The present invention has been described with the embodiments thereof, any details of the description of the present invention are not limited unless described otherwise, and it is obvious that the present invention is widely construed without departing from the gist and scope of the present invention described in the accompanying claims.

[0265] The present application claims priority based on JP2023-050477 filed on Mar. 27, 2023, the entire content of which is incorporated herein by reference.

Examples

example 1

[0240]Using the metal ion-containing aqueous solution (W1) and the oil phase (Y1) the separation extraction operation (wet extraction method) of metal ions was repeated 10 times as described below.

[0241]10 mL of the extractant solution (Y1) with respect to 10 mL of the prepared metal ion-containing aqueous solution (W1) was added to a 30 mL vial tube, and the mixture was stirred using a stirrer tip at 25° C. for 30 minutes (pre-mixing). In this case, the mixing amount (unit: equivalent) of the compound E-1 with respect to the total content of metal ions to be coordinated (that have the same definition as the extracted metal ions; in Example 1, Co and Ni) was 0.98. Next, a 10 M sodium hydroxide aqueous solution or a 10 M hydrochloric acid was added to adjust the pH of the mixed solution to a value shown in the column “pH during Mixing” of Table 1-1. Further, the solution was stirred at 25° C. for 30 minutes, and was left to stand at the same temperature for 1 hour. After verifying th...

Claims

1. A metal extractant that extracts metal ions present in a water phase to an oil phase,wherein the metal extractant has a structure represented by Formula (I) and does not include a nitrogen atom,in Formula (I), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,X represents a monovalent substituent including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom, anda benzene ring in Formula (I) may form a fused ring.

2. The metal extractant according to claim 1,wherein the metal extractant includes a functional group selected from the following group G of functional groups,<Group G of Functional Groups>a carboxy group, a phosphate group, a phosphonate group, a phosphinate group, a sulfonate group, and a sulfinate group.

3. The metal extractant according to claim 2,wherein the functional group selected from the group G of functional groups is a phosphate group or a phosphonate group.

4. The metal extractant according to claim 1,wherein the metal extractant has a hydrocarbon group having 9 or more carbon atoms.

5. The metal extractant according to claim 3,wherein the metal extractant has a hydrocarbon group having 9 or more carbon atoms.

6. The metal extractant according to claim 1,wherein the metal extractant is represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, anda benzene ring in Formula (II) may form a fused ring.

7. The metal extractant according to claim 1,wherein the metal ions are ions of a metal element belonging to Group 1 to Group 14 in a periodic table.

8. The metal extractant according to claim 1,wherein the metal extractant is used for extraction and separation of two or more kinds of metal ions belonging to different groups in a periodic table among the metal ions.

9. The metal extractant according to claim 6,wherein the metal extractant is used for extraction and separation of two or more kinds of metal ions belonging to different groups in a periodic table among the metal ions.

10. A separation recovery method of metal ions, the separation recovery method comprising:mixing a water phase including plural kinds of metal ions with an oil phase including the metal extractant according to claim 1.

11. A compound represented by Formula (II),in Formula (II), R1 represents a hydrogen atom, a metal atom, or a monovalent substituent,L represents a divalent linking group including at least one of an oxygen atom, a sulfur atom, or a phosphorus atom and not including a nitrogen atom,R2 represents a hydrocarbon group having 8 or more carbon atoms, in which in a case where L represents a carbonyloxy group, R2 represents a hydrogen atom or a hydrocarbon group having 8 or more carbon atoms, anda benzene ring in Formula (II) may form a fused ring.

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