Metal extractant, method for separating and recovering metal ions using said metal extractant, and compound

Abstract

Provided are a compound represented by formula (I), a metal extractant, and a method for separating and recovering metal ions using this metal extractant. In formula (I), R1 and R2 each represent a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. YP represents an oxygen atom or a sulfur atom. Z represents a hydroxy group, a sulfanyl group or a hydroxyaryl group. L represents a single bond, but in cases where n is 2 or more, L sandwiched between two adjacent Ps represents a single bond or a linking group. n represents an integer of 1 to 6.

Description

Metal extractant, method for separating and recovering metal ions using the metal extractant, and compound

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

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

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

[0004] As an example of a metal extractant for use in such a wet extraction method, Patent Document 1 describes a metal extractant consisting of a phenylphosphonic acid monoester of a hydrocarbon group having 4 to 6 branched carbon atoms and a total of 16 to 20 carbon atoms. Furthermore, Patent Document 2 describes a metal extractant for use in a wet extraction method in which an organic phase containing a metal extractant is contacted with an aqueous phase in multiple stages, the metal extractant being a monoalkyl alkylphosphonate ester in which both alkyl groups have 8 to 10 carbon atoms (excluding cases in which both alkyl groups are the same alkyl group having 8 carbon atoms).

[0005] JP 2012-184503 A JP 61-58531 A

[0006] It is described that the metal extractants described in Patent Documents 1 and 2 can be used in wet extraction to extract and recover specific metal ions present in an aqueous phase into an oil phase. However, the selectivity (separation ability) of the extracted metal ions is insufficient for either metal extractant. Therefore, a highly selective metal extractant capable of selectively separating and extracting specific metal ions from an aqueous phase is desired. Furthermore, when the metal extractants described in Patent Documents 1 and 2 are used in wet extraction, a long period of time is required for liquid phase separation between the aqueous and oil phases after contact and mixing. As a result, the productivity of the wet extraction method (metal ion separation and recovery efficiency) is low and the method is not suitable for continuous separation and recovery processing. In particular, the metal extractant described in Patent Document 2 requires contact between the aqueous and oil phases in multiple stages, resulting in productivity problems. Therefore, a metal extractant that can rapidly increase the phase separation rate after contact and mixing of the aqueous and oil phases is also desired. However, Patent Documents 1 and 2 do not consider further improvement of metal ion selectivity or improvement of phase separation rate.

[0007] The present invention aims to provide a metal extractant that can rapidly separate an aqueous phase containing metal ions from an oil phase while extracting specific metal ions present in the aqueous phase into the oil phase with high selectivity, and a method for separating and recovering metal ions using the metal extractant. Another objective of the present invention is to provide a compound that can be used as a metal extractant exhibiting the above-mentioned excellent properties.

[0008] The present inventors have conducted extensive research into metal extractants for use in wet extraction methods, and have found that the basic structure (-P(=Y)) derived from phosphoric acid compounds Ｐ ) Z-:Y Ｐ and Z are as described below. It has been found that by adopting a compound in which at least one active hydrogen atom remains in its basic structure and two substituents having specific molecular weights are introduced, it is possible to achieve both an increase in the phase separation rate and an improvement in selectivity (separation ability), thereby solving the problem of conventional wet extraction methods in which an increase in the phase separation rate generally leads to a decrease in the selectivity of the metal ions to be separated and extracted. The present invention has been completed through further investigation based on these findings.

[0009] That is, the above-mentioned problems have been solved by the following means: <1> A metal extractant for extracting metal ions present in an aqueous phase into an oil phase, the metal extractant being represented by the following formula (I): In formula (I), R １ and R ２ Each of Y represents a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. Ｐ represents an oxygen atom or a sulfur atom. Z represents a hydroxy group, a sulfanyl group, or a hydroxyaryl group. L represents a single bond, provided that when n is 2 or greater, the L sandwiched between two adjacent Ps represents a single bond or a linking group. n is an integer of 1 to 6. <2> R １ and R ２ The metal extractant according to <1>, wherein at least one of R is a substituent containing any one of a nitrogen atom, an oxygen atom, and a sulfur atom. <3> The metal extractant according to <1> or <2>, wherein n is 1. <4> R １ and R ２ <5> The metal extractant according to any one of <1> to <3>, wherein at least one of R is a substituent having a branched structure. １ and R ２ The metal extractant according to any one of <1> to <4>, wherein at least one of R is a substituent containing a hydrocarbon group having 3 or more branched carbon atoms, or a substituent containing a hydrocarbon group having 9 or more carbon atoms.１ and R ２ <7> The metal extractant according to any one of <1> to <5>, wherein at least one of R is a substituent containing a hydrocarbon group having one or more branched carbon atoms and 9 or more carbon atoms. １ and R ２ The metal extractant according to any one of <1> to <6>, wherein at least one of the groups is a substituent containing a ring structure. <8> The metal extractant according to any one of <1> to <7>, wherein the metal ion is an ion of a metal element belonging to Groups 1 to 14 of the periodic table. <9> The metal extractant according to any one of <1> to <8>, which is used for extracting and separating two or more types of metal ions belonging to different groups in the periodic table. <10> A method for separating and recovering metal ions, which comprises mixing an aqueous phase containing multiple types of metal ions with an oil phase containing the metal extractant according to any one of <1> to <9>. <11> A compound represented by the following formula (I): In formula (I), R １ and R ２ R each represents a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. １ and R ２ At least one of Y represents a substituent having a branched structure. Ｐ represents an oxygen atom or a sulfur atom. Z represents a hydroxy group, a sulfanyl group, or a hydroxyaryl group. L represents a single bond, provided that when n is 2 or greater, the L sandwiched between two adjacent Ps represents a single bond or a linking group. n is an integer from 1 to 6.

[0010] The present invention provides a metal extractant capable of extracting specific metal ions present in an aqueous phase into an oil phase with high selectivity while rapidly separating the aqueous phase containing the metal ions from the oil phase, and a method for separating and recovering metal ions using the metal extractant. The present invention also provides a compound that can be used as a metal extractant and exhibits the above-mentioned excellent properties. The above and other features and advantages of the present invention will become more apparent from the following description, taken in conjunction with the accompanying drawings, where appropriate.

[0011] FIG. 1 shows the compound E-1 synthesized in the example. １ 1H-NMR chart.

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

[0013] [Metal Extractant] The metal extractant of the present invention contains a compound represented by formula (I) described below, and may contain other components as appropriate within the scope of not impairing the effects of the present invention. Furthermore, the metal extractant of the present invention may contain other compounds (other metal extractants) that function as extractants for metal ions in addition to the compound represented by formula (I). However, since the compound represented by formula (I) exhibits the above-mentioned excellent properties as a metal extractant, as described below, it is preferable to contain the compound represented by formula (I) alone. In the present invention, the metal extractant of the present invention containing the compound represented by formula (I) alone includes embodiments containing only the compound represented by formula (I) and embodiments containing the other metal extractant in an amount of 10% by mass or less relative to the total amount of the compound represented by formula (I). Furthermore, the form of the metal extractant of the present invention and the compound represented by formula (I) are not particularly limited, and may be in a solid form such as powder or granules, or in a liquid form (solution) dissolved in an organic solvent described below. The metal extractant of the present invention exhibits the function of extracting metal ions present in an aqueous phase into an oil phase and is particularly suitable for use in wet extraction methods. When the metal extractant of the present invention is used in a wet extraction method, specific metal ions present in an aqueous phase can be extracted into an oil phase with high selectivity, preferably with a high recovery rate (high extraction rate). In particular, this metal extractant can extract specific metal ions from multiple types of metal ions present in the aqueous phase into an oil phase with high selectivity, preferably with a high recovery rate. In the present invention, the metal ions that can be extracted into the oil phase from the multiple types of metal ions present in the aqueous phase are ideally one specific metal ion, but two or more metal ions may also be extracted. Even in the case of two or more metal ions, one of the metal ions can be extracted (separated and recovered) into the oil phase with high selectivity, preferably with a high recovery rate, relative to the other metal ions (including those extracted into the oil phase). For example, two or more different metal ions, for example, two or more metal ions belonging to Groups 1 to 14 of the periodic table, desirably two or more different metal ions, particularly desirably cobalt ions and nickel ions, which are different metal ions of the same period, can be extracted into the oil phase as ions of valuable metal elements, while one of the metal ions can be extracted into the oil phase with high selectivity, preferably with a high recovery rate.Because metal ions belonging to the same periodic group have similar physical and chemical behaviors, it is not easy to separate and recover one of them with high selectivity. However, in the present invention, which uses a compound represented by formula (I) as a metal extractant, it is possible to extract both metal ions belonging to the same periodic group that have similar physical and chemical behaviors, particularly metal ions belonging to Group 9 (particularly cobalt ions) and metal ions belonging to Group 10 (particularly nickel ions), which are required due to the rapid spread of lithium-ion batteries in recent years, while recovering one of the metal ions with high selectivity and preferably at a high recovery rate. Therefore, the present invention can greatly contribute to the further spread of electric vehicles and, ultimately, to the creation of a sustainable society.

[0014] In the present invention, "highly selective extraction of metal ions" means that only one specific metal ion can be extracted from multiple metal ions present in the aqueous phase. Furthermore, when two or more metal ions are extracted into the oil phase, "highly selective extraction of metal ions" means that, among the two or more extracted metal ions, the ratio of the specific metal ion (usually one type) to the total amount of other metal ions extracted [(amount of specific metal ion extracted) / (total amount of other metal ions extracted)] can be extracted and separated from other metal ions at a ratio (separation ability, selectivity) of 3.0 or more. The ratio (selectivity) is preferably 4.0 or more, more preferably 5.0 or more, and even more preferably 6.0 or more. The upper limit is not particularly limited, but can be, for example, 50.

[0015] In the present invention, the phrase "high recovery rate of metal ions" means that, for the metal ions extracted in the maximum amount (specific metal ions to be extracted), the amount of the metal ions extracted into the oil phase is 60% or more as a ratio of the amount of the metal ions extracted into the aqueous phase (before extraction) [(amount of metal ions extracted into the oil phase) / (content of the metal ions in the aqueous phase)]. This ratio (recovery rate) is preferably 80% or more, and more preferably 90% or more. The upper limit is not particularly limited, and ideally is the total amount of the metal ions present in the aqueous phase (100%). For example, it is preferably 99% or less, and can also be 95% or less or 90% or less. The specific extraction rate, depending on the content of the metal ions present in the aqueous phase, can be, for example, 30,000 ppm by mass or less, and preferably 20,000 ppm by mass or less.

[0016] In the present invention, the time required for rapid liquid phase separation (phase separation) after contact and mixing of the aqueous phase and the oil phase is not uniquely determined by the content of metal ions or metal extractant, the liquid volumes of the aqueous phase and the oil phase, the mixing conditions, etc. Rapid liquid phase separation of the aqueous phase and the oil phase means, for example, that the two phases separate to a state where the phase interface can be visually confirmed within 5 minutes (at the end of 5 minutes) after mixing of the two phases is stopped under the conditions in the Examples described below. In the present invention, the time required for liquid phase separation of the aqueous phase and the oil phase to be completed after contact and mixing of the two phases (when the phase interface can be visually confirmed) is referred to as the phase separation time, and the speed at which the two phases separate after contact and mixing of the aqueous phase and the oil phase is referred to as the phase separation rate.

[0017] (Compound Represented by Formula (I)) The metal extractant of the present invention comprises a compound having a chemical structure represented by the following formula (I) (sometimes referred to as the compound of the present invention). As described above, this compound exhibits excellent properties as a metal extractant.

[0018] In formula (I), R １ and R ２ Each of R represents a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more.１ and R ２ are each a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. Ｐ )Z-" (Y Ｐ and Z are as described below.) and two substituents R １ and R ２ Compounds having the above basic structure represented by formula (I) include compounds having 1 to 6 acid groups, such as phosphate groups, phosphonate groups, and phosphinate groups, as well as compounds having at least one oxygen atom of these acid groups substituted with a sulfur atom. For example, compounds in which n is 1 in formula (I) include phosphate ester compounds (R １ OP(=O)(Z)-OR ２ ), phosphonate ester compounds (R １ -P(=O)(Z)-OR ２ , R １ OP(=O)(Z)-R ２ ) or phosphinic acid compounds (R １ -P(=O)(Z)-R ２ and thiophosphoric acid compounds in which at least one oxygen atom in each of the above phosphoric acid compounds is converted to a sulfur atom. It should be noted that "Z" in each of the above compounds has the same meaning as Z in formula (I). The compound represented by formula (I) in which n is 1 is preferably a phosphoric acid compound, more preferably a phosphoric acid ester compound or a phosphonic acid ester compound, even more preferably a phosphonic acid ester compound, and particularly preferably a phosphonic acid monoester compound, in that it can achieve both high levels of selectivity and phase separation rate as a metal extractant.

[0019] R １ and R ２ The substituents that can be used as R are all those having a molecular weight of 100 or more. １ and R ２ The molecular weight of at least one of the possible substituents R １ The substituents that can be used as R２ and the substituents which can be taken as R have a molecular weight of 100 or more, and at least one of them has a molecular weight of 160 or more, so that the compound represented by the above formula (I) becomes a metal extractant which exhibits high selectivity even when the phase separation rate is fast. １ and R ２ The molecular weight of the substituent that can be used as R is preferably 120 or more, more preferably 160 or more, and even more preferably 200 or more, in terms of the selectivity and phase separation rate of the metal extractant. On the other hand, the upper limit of the molecular weight of the substituent is not particularly limited and can be determined appropriately, and can be, for example, 400 or less, preferably 350 or less. In terms of achieving both high levels of selectivity and phase separation rate of the metal extractant, R １ and R ２ It is preferable that the molecular weight of both substituents that can be taken as R is 160 or more. １ and R ２ Among the substituents that can be used as R, those having a molecular weight of 160 or more preferably have a molecular weight of 200 or more, more preferably 220 or more, and even more preferably 240 or more, in that they can achieve both the selectivity of the metal extractant and the phase separation rate at a higher level. The upper limit of the molecular weight of the substituents having a molecular weight of 160 or more is not particularly limited, and １ and R ２ The molecular weight of the substituent R can be set to the above upper limit. １ and R ２ When the molecular weights of all possible substituents are 160 or more, it is preferable that at least one of the substituents has the above molecular weight. In the present invention, the molecular weight of a substituent refers to the total atomic weight of the atoms constituting the substituent. However, when the substituent has a polymer chain in its structure, the number average molecular weight is determined by gel permeation chromatography (GPC) as converted into standard polystyrene as described below.

[0020] R １ and R ２ The total number of carbon atoms constituting each substituent is not particularly limited and can be determined appropriately as long as the substituent satisfies the above-mentioned molecular weight. For example, １ and R２ The total number of carbon atoms in the substituents that can be used as R (hereinafter simply referred to as the number of carbon atoms) is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and particularly preferably 14 or more, in terms of the selectivity and phase separation rate of the metal extractant. On the other hand, the upper limit of the number of carbon atoms is not particularly limited and can be determined appropriately, and can be, for example, 30 or less, and preferably 24 or less. １ and R ２ The number of carbon atoms in the substituent having a molecular weight of 160 or more among the substituents that can be used as R is preferably 12 or more, more preferably 14 or more, even more preferably 15 or more, and particularly preferably 16 or more, in order to achieve a higher level of both selectivity and phase separation rate of the metal extractant. １ and R ２ The number of carbon atoms in the substituent may be set to the above upper limit.

[0021] R １ and R ２ The substituents that can be taken as R are not particularly limited, and include various substituents and groups that combine substituents. In the present invention, the above-mentioned "various substituents" do not represent R alone. １ and R ２ The above "groups with a combination of substituents" refers to substituents formed by combining multiple substituents. In order to clearly distinguish between the above "various substituents" and the above "groups with a combination of substituents," for convenience, the above "various substituents" are sometimes referred to as "single substituents," and the above "groups with a combination of substituents" are sometimes referred to as "composite substituents." A composite substituent is formed by combining multiple single substituents, usually by removing hydrogen atoms from a required number of single substituents among the single substituents that constitute it. In a composite substituent, the position at which a specific substituent is substituted with another substituent is not particularly limited and can be determined appropriately. For example, when a phenyl group is substituted with another substituent, the substitution position may be any of the 2nd to 4th positions relative to the bonding position of the phenyl group. In the present invention, R １ and R ２Substituents that can be used as a group are interpreted as single substituents whenever possible. For example, a 2-ethylhexyl group can be interpreted as a compound substituent in which an ethyl group substitutes for a hexyl group, but it is interpreted as a branched alkyl group. Furthermore, a hexyloxy group can be interpreted as a compound substituent combining a hexyl group and an oxygen atom, but it is interpreted as an alkoxy group.

[0022] R １ and R ２ The substituents (including single substituents and composite substituents) that can be taken as R may be hydrocarbon groups composed only of carbon atoms and hydrogen atoms, or may be heteroatom-containing substituents containing at least one heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. １ and R ２ It is preferable that at least one of the possible substituents is a heteroatom-containing substituent. The heteroatom-containing substituent preferably contains an oxygen atom or a sulfur atom as the heteroatom, and preferably contains an oxygen atom. The number of heteroatoms contained in the heteroatom-containing substituent is not particularly limited and can be 1 to 4, preferably 1. In the heteroatom-containing substituent, the heteroatom may be present in any of the substituents, for example, it may be present inside or at the end of the atomic chain constituting the substituent. In the present invention, it is preferable that one of the heteroatoms is present at the end of the atomic chain constituting the substituent and is bonded to P in the above formula (I). The heteroatom-containing substituent is not particularly limited, and examples thereof include single substituents such as alkoxy groups, aryloxy groups, heterocyclic oxy groups, alkylthio groups, arylthio groups, and heterocyclic thio groups, as described below, and composite substituents such as groups combining these single substituents with an aryl group (substituents containing a ring structure).

[0023] R １ and R ２The single substituent that can be taken as is not particularly limited, and includes appropriate substituents, for example, a group selected from the substituent GZ described below (however, the number of carbon atoms and molecular weight are as described above, not those of the substituent GZ). Among them, hydrocarbon groups such as alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, heterocyclic groups, alkoxy groups, aryloxy groups, heterocyclic oxy groups, alkylthio groups, arylthio groups, heterocyclic thio groups, amino groups, etc. are preferred, and in terms of the selectivity and phase separation rate of the metal extractant, alkyl groups, alkoxy groups, and alkylthio groups are more preferred, and alkyl groups or alkoxy groups are even more preferred.

[0024] The alkyl, alkenyl, and alkynyl groups that can be used as sole substituents may be linear, branched, or cyclic, but branched chains are more preferred because they can achieve a higher level of both selectivity and phase separation rate for the metal extractant. The molecular weights and carbon number of the alkyl, alkenyl, and alkynyl groups all satisfy the above-mentioned ranges. The aryl, heterocyclic, aryloxy, heterocyclic oxy, arylthio, heterocyclic thio, and amino groups that can be used as sole substituents are the same as the corresponding groups in the substituent GZ described below. The alkyl groups that constitute the alkoxy and alkylthio groups that can be used as sole substituents are all the same as the alkyl groups that can be used as sole substituents.

[0025] R １ and R ２The composite substituent that can be used as the substituent is not particularly limited, and examples thereof include (single) substituents, such as groups combining multiple substituents selected from the substituents G and Z. The number of single substituents constituting the composite substituent is not particularly limited, and can be 2 to 6, preferably 2 to 4. Examples of composite substituents include groups combining hydrocarbon groups (groups combining an alkyl group, an alkenyl group, or an alkynyl group with an aryl group), groups combining an alkoxy group or an alkylthio group with an aryl group, and groups combining an alkyl group, an alkenyl group, or an alkynyl group with an amino group. In addition, when an oxygen atom or sulfur atom bonded to an alkyl group is contained in the composite substituent, the oxygen atom and sulfur atom are interpreted as atoms derived from the alkoxy group or alkylthio group, respectively. For example, the composite substituent "alkyl group-oxygen atom-phenyl group-" in compounds E-4 and E-5 synthesized in the examples is interpreted as a group combining an alkoxy group and a phenyl group, not as a group combining an alkyl group and a phenoxy group, nor as a group combining an alkyl group, an oxygen atom, and a phenyl group. The above interpretation is the same when the composite substituent contains an oxygen atom or the like bonded to an alkenyl group or an alkynyl group.

[0026] As the composite substituent, those containing a ring structure are preferred in that the selectivity and phase separation rate of the metal extractant can be compatible at a higher level. The ring structure contained in the composite substituent is not particularly limited, and examples thereof include ring structures derived from cycloalkyl groups, aryl groups, heterocyclic groups, etc., and ring structures derived from aryl groups and aromatic heterocyclic groups are preferred. In terms of the selectivity and phase separation rate of the metal extractant, ring structures derived from aryl groups are more preferred. Specific examples of composite substituents containing a ring structure include groups combining an alkyl group and an aryl group, groups combining an alkoxy group or an alkylthio group and an aryl group, etc., and alkoxyaryl groups are more preferred, and alkoxyphenyl groups are even more preferred.

[0027] R １ and R ２Among the above-mentioned substituents, preferred are alkyl, alkoxy, and alkylthio groups, or composite substituents containing a ring structure combining an alkoxy or alkylthio group with an aryl group, from the viewpoint of the selectivity and phase separation rate of the metal extractant. Among the preferred substituents, the alkoxy, alkylthio, and composite substituents containing a ring structure are preferably those having a molecular weight of 160 or more, from the viewpoint of the selectivity and phase separation rate of the metal extractant.

[0028] R １ The substituents that can be used as R ２ The combination of substituents that can be taken as R is not particularly limited, and １ and R ２ The above-mentioned substituents that can be taken as R can be appropriately combined. For example, the molecular structure of the substituent is not particularly limited. １ and R ２ The substituents that can be used as the branched structure are preferably combinations containing substituents having a branched structure (combinations in which at least one of the substituents has a branched structure) in terms of the selectivity and phase separation rate of the metal extractant, and more preferably combinations of branched substituents with each other, and combinations of branched substituents with substituents having a ring structure (particularly composite substituents). Here, the branched structure substituent is not particularly limited, but among the above, examples include hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, and single or composite substituents containing hydrocarbon groups. Single substituents such as alkyl groups, alkoxy groups, and arylthio groups, or composite substituents such as groups combining alkoxy groups or alkylthio groups with aryl groups are preferred, and alkyl groups, alkoxy groups, or groups combining alkoxy groups and aryl groups are more preferred. In the present invention, the branched structure substituent does not have to be a substituent having a molecular weight of 160 or more or a substituent having 12 or more carbon atoms, but in terms of the selectivity and phase separation rate of the metal extractant, it is preferable that the substituent have a molecular weight of 160 or more or a substituent having 12 or more carbon atoms.

[0029] The type of the substituent is not particularly limited, but R１ and R ２ As for possible combinations of substituents, in terms of the selectivity and phase separation rate of the metal extractant, combinations of single substituents or combinations of single substituents and complex substituents are preferred. In combinations of single substituents, the same (type) of substituents may be combined, or different (types) of substituents may be combined. Examples of combinations of the same substituents include combinations of alkyl groups, alkenyl groups, alkynyl groups, alkoxy groups, or alkylthio groups. In the above combinations of the same substituents, the carbon chains of the combined single substituents may be the same or different, but it is preferable that both are branched chains. Furthermore, the number of carbon atoms of the combined single substituents may be the same or different.

[0030] On the other hand, as a combination of different substituents, a combination in which one of the substituents is an alkoxy group or an alkylthio group is preferred. In terms of the selectivity and phase separation rate of the metal extractant, a combination of an alkyl group, an alkenyl group, or an alkynyl group with an alkoxy group or an alkylthio group is more preferred, and a combination of an alkyl group with an alkoxy group is even more preferred. In the above combinations of different substituents, the carbon chain of the alkyl group, alkenyl group, or alkynyl group and the carbon chain of the alkyl group constituting the alkoxy group or alkylthio group may be the same or different, but it is preferable that both are branched chains. Furthermore, the number of carbon atoms of the alkyl group, alkenyl group, or alkynyl group and the number of carbon atoms of the alkyl group constituting the alkoxy group or alkylthio group may be the same or different. In the above preferred combinations of different substituents, the alkoxy group and the alkylthio group preferably have a larger molecular weight and carbon number than the alkyl group, alkenyl group, and alkynyl group, in order to achieve a higher level of both selectivity and phase separation rate of the metal extractant, and more preferably correspond to a substituent with a molecular weight of 160 or more.

[0031] As a combination of a single substituent and a composite substituent, in terms of the selectivity and phase separation rate of the metal extractant, a combination of an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, or an alkylthio group with a composite substituent containing a ring structure is preferred, and a combination of an alkyl group, an alkoxy group, or an alkylthio group with a composite substituent combining an alkoxy group and an aryl group is more preferred.

[0032] R １ The substituents that can be used as R ２ Among the above-mentioned combinations of possible substituents, a combination of alkoxy groups, a combination of an alkyl group and an alkoxy group, and a combination of an alkoxy group and an alkoxyaryl group are particularly preferred.

[0033] In the compound represented by formula (I), R １ and R ２ The substituents that can be used for R can be selected appropriately from the above-mentioned substituents. However, when focusing on the molecular structure and number of carbon atoms of the substituents, R is preferred in that it can achieve both high levels of selectivity and phase separation rate of the metal extractant. １ and R ２ is a substituent containing a hydrocarbon group having 3 or more branched carbon atoms, or a substituent containing a hydrocarbon group having 9 or more carbon atoms, and １ and R ２ is more preferably a substituent containing a hydrocarbon group having 3 or more branched carbon atoms, or a substituent containing a hydrocarbon group having 9 or more carbon atoms. In the present invention, the substituent containing a specific group or ring structure includes a substituent consisting of only the specific group or ring structure, and a substituent consisting of the specific group or ring structure and other groups, atoms, or structures (details will be described later). For example, the substituent containing a hydrocarbon group includes a substituent consisting of only a hydrocarbon group (the hydrocarbon group itself) and a hydrocarbon oxy group consisting of this hydrocarbon group and, for example, an oxygen atom.

[0034] The hydrocarbon group having three or more branched carbon atoms is not particularly limited, but typically includes alkyl groups, alkenyl groups, or alkynyl groups having a branched structure, each of which has three or more branched carbon atoms (tertiary carbon atoms). The number of branched carbon atoms present in the hydrocarbon group is not particularly limited as long as it is three or more, and can be, for example, 3 to 8. From the viewpoints of the selectivity and phase separation rate of the metal extractant, it is preferably 3 to 6, and more preferably 4 to 6. The molecular weight and number of carbon atoms of the hydrocarbon group having three or more branched carbon atoms are not particularly limited and can be appropriately selected within the above ranges, but it is preferable that the molecular weight is 160 or more and the number of carbon atoms is 12 or more. As the hydrocarbon group having three or more branched carbon atoms, alkyl groups having a branched structure and having three or more branched carbon atoms are preferred, such as 2,5,7,7-tetramethyloctane and 2-(1,3,3-trimethyl-1-butyl)-5,7,7-trimethyloctane.

[0035] The hydrocarbon group having 9 or more carbon atoms is not particularly limited. However, among the above-mentioned hydrocarbon groups, an alkyl group, an alkenyl group, or an alkynyl group is preferred, and an alkyl group is more preferred. The molecular weight of the hydrocarbon group having 9 or more carbon atoms is not particularly limited as long as it is 127 or more, but is preferably selected appropriately within the above range. The hydrocarbon group having 9 or more carbon atoms may be linear or branched, but a branched chain is preferred. When the hydrocarbon group having 9 or more carbon atoms is branched, the number of branched carbon atoms is not particularly limited as long as it is 1 or more, and examples include an embodiment having 1 or 2 branched carbon atoms and an embodiment having 3 or more branched carbon atoms. In an embodiment having 3 or more branched carbon atoms, the number of branched carbon atoms is preferably the same as the number of branched carbon atoms of the hydrocarbon group having 3 or more branched carbon atoms, in terms of the selectivity and phase separation rate of the metal extractant. As the hydrocarbon group having 9 or more carbon atoms, an alkyl group having 9 or more carbon atoms is preferred, and a branched alkyl group having 1 or more branched carbon atoms and 9 or more carbon atoms is more preferred. Examples of linear alkyl groups having 9 or more carbon atoms include n-nonyl, n-decyl, n-dodecyl, n-tetradecyl, and n-hexadecyl. Examples of alkyl groups having 9 or more carbon atoms and one or two branched carbon atoms include 1-ethyl-1-methylhexane, 8-methylnonane, 2-butyloctane, 2-hexyldecane, 2-ethyldecane, 2-octyldecane, 2-hexyldodecane, 2-octyldodecane, and 2-decyltetradecane. Examples of alkyl groups having 9 or more carbon atoms and three or more branched carbon atoms include 2-(1,3,3-trimethyl-1-butyl)-5,7,7-trimethyloctane.

[0036] The atoms, groups, etc. other than the hydrocarbon group that constitute the substituent containing the hydrocarbon group are not particularly limited, and examples thereof include groups selected from the substituents GZ described below (substituents other than hydrocarbon groups), the heteroatoms, etc. Among these, groups containing the hydrocarbon group and an oxygen atom or a sulfur atom are preferred, and specific examples thereof include an alkoxy group and an alkylthio group.

[0037] In this embodiment, R １The substituents that can be used as R ２ The combination of substituents that can be taken as R is not particularly limited, and any one of the substituents may be a substituent containing a hydrocarbon group having 3 or more branched carbon atoms or a substituent containing a hydrocarbon group having 9 or more carbon atoms. １ and R ２ Among the above possible substituents, substituents that do not fall into either the category of a substituent containing a hydrocarbon group having 3 or more branched carbon atoms or a hydrocarbon group having 9 or more carbon atoms can be appropriately combined. Substituents that do not fall into either of the above categories are not uniquely determined by the substituent containing a hydrocarbon group having 3 or more branched carbon atoms or the substituent containing a hydrocarbon group having 9 or more carbon atoms, but examples thereof include linear alkyl groups having 8 carbon atoms.

[0038] In formula (I), Y Ｐ represents an oxygen atom or a sulfur atom, and an oxygen atom is preferred.

[0039] In formula (I), Z represents a hydroxy group, a sulfanyl group (mercapto group), or a hydroxyaryl group. A preferred first embodiment of the group that can be taken as Z is preferably a hydroxy group or a sulfanyl group, and more preferably a hydroxy group. Meanwhile, a preferred second embodiment of the group that can be taken as Z is preferably a hydroxy group or a hydroxyaryl group. The hydroxyaryl group that can be taken as Z may be any aryl group having at least one hydroxy group. Examples of the aryl group include the aryl groups in the substituent GZ described below, with a phenyl group being preferred. The number of hydroxy groups introduced into the aryl group is not particularly limited and can be 1 to 4, with 1 or 2 being preferred. The position of the aryl group into which the hydroxy group is introduced is not particularly limited and can be appropriately set relative to the bonding position of the aryl group. For example, in the case of a phenyl group, the hydroxy group may be introduced at any of the 2- to 4-positions relative to the bonding position, with the 2-position being preferred. Examples of hydroxyaryl groups include 2-, 3-, or 4-hydroxyphenyl groups, dihydroxyphenyl groups, trihydroxyphenyl groups, and tetrahydroxyphenyl groups. In terms of the selectivity and phase separation rate of the metal extractant, 2-, 3-, or 4-hydroxyphenyl groups are preferred. Each of the groups that can be taken as Z may form a salt. Cations that form salts are not particularly limited, and include, for example, metal cations, particularly Group 1 or Group 2 metal cations, organic cations, and the like. Examples of organic cations are not particularly limited, and include, for example, ammonium cations, alkylammonium cations, and the like.

[0040] In formula (I), L represents a single bond. However, when n is 2 or more, the L sandwiched between two adjacent Ps represents a single bond or a linking group. The linking group that can be taken as L is not particularly limited, and examples thereof include an alkylene group (preferably having 1 to 12 carbon atoms, more preferably having 1 to 6 carbon atoms, and even more preferably having 1 to 4 carbon atoms), an alkenylene group (preferably having 2 to 6 carbon atoms, and more preferably having 2 to 3 carbon atoms), an arylene group (preferably having 6 to 24 carbon atoms, and more preferably having 6 to 10 carbon atoms), an oxygen atom, a sulfur atom, an imino group (-NR Ｎ -:R Ｎrepresents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms. ), a carbonyl group, or a group relating to a combination thereof. The linking group is preferably an alkylene group, an arylene group, a carbonyl group, an oxygen atom, a sulfur atom, or an imino group, or a group relating to a combination thereof, with an alkylene group being more preferred. Here, the alkylene group and alkenylene group may be linear, branched, or cyclic, but linear or branched chains are preferred. In the group relating to the combination, the number of groups, linking groups, or atoms to be combined is not particularly limited, but can be, for example, 2 to 15, preferably 2 to 10, and more preferably 2 to 5. The number of types of groups, linking groups, or atoms to be combined is also not particularly limited, but can be, for example, two or more, preferably two or three. The number of linking atoms in the linking group is not particularly limited, but is preferably 15 or less, more preferably 10 or less, even more preferably 6 or less, and particularly preferably 4 or less. The lower limit is 1 or more. The number of linking atoms refers to the minimum number of atoms connecting two adjacent Ps. The number of atoms constituting the linking group (number of constituent atoms) is not particularly limited, but can be, for example, 3 to 30, preferably 3 to 20, and more preferably 3 to 10. For example, when the linking group is -CH ２ -CH ２ -, the number of atoms constituting the molecular structure is 6, but the number of linking atoms is 2. When the compound represented by formula (I) has two or more linking groups, it is sufficient that at least one linking group satisfies the above-mentioned number of linking atoms and number of constituent atoms, and it is preferable that all linking groups satisfy the above-mentioned number of linking atoms and number of constituent atoms.

[0041] In formula (I), n is an integer of 1 to 6. In a first preferred embodiment of n, n is preferably an integer of 1 to 3. In a second preferred embodiment of n, n is preferably 1 or an integer of 3 to 6. In the first and second embodiments, n is more preferably 1. When n is an integer of 2 to 6, n Y Ｐ , Z and L may be the same or different.

[0042] The compound represented by formula (I) is a compound represented by formula (I) １ and R ２ And Y Ｐ The compound represented by formula (I) can be formed by appropriately combining Z, L, and n, and it is preferable to form it by combining preferred symbols. However, although the compound represented by formula (I) may be a basic compound, it is preferable that it is an acidic compound having at least one active hydrogen atom, that is, the compound represented by formula (I) corresponds to an acidic metal extractant, in terms of exhibiting excellent selectivity and a high phase separation rate as a metal extractant. Examples of the active hydrogen atom in the compound include a hydroxy group (including a phenolic hydroxy group) and a hydrogen atom in a sulfanyl group. The active hydrogen atom is represented by R １ , R ２ and L, but preferably present in Z. The number of hydroxy groups present in the compound may be one or more, and may be 1 to 4, with 1 or 2 being preferred. In the compound represented by formula (I), a group containing an active hydrogen atom may form a salt, converting the active hydrogen atom into a cation. Such a cation is not particularly limited, and examples include the cations described above for Z.

[0043] The compound represented by formula (I) may function as a polydentate ligand with respect to a specific metal ion (metal ion to be extracted) present in the aqueous phase, but from the viewpoints of selectivity and phase separation rate, it is preferable that the compound function as a monodentate ligand.

[0044] The molecular weight of the compound represented by formula (I) is not particularly limited, but can be, for example, 350 to 50,000. From the viewpoint of solubility in the oil phase, etc., it is preferably 400 to 10,000, and more preferably 500 to 1,000. In the present invention, when the compound represented by formula (I) has a polymer chain, the molecular weight refers to the number average molecular weight calculated in terms of standard polystyrene by gel permeation chromatography (GPC), unless otherwise specified. - Molecular Weight Measurement - The molecular weight of the oligomer is basically measured by the method under Condition 1 or Condition 2 (preferred) below. However, depending on the type of oligomer, an appropriate eluent may be selected and used. (Condition 1) Column: Two TOSOH TSKgel Super AWM-H (trade name, manufactured by Tosoh Corporation) connected together Carrier: 10 mM LiBr / N-methylpyrrolidone Measurement temperature: 40°C Carrier flow rate: 1.0 ml / min Sample concentration: 0.1 mass% Detector: RI (refractive index) detector (Condition 2) Column: A column connected together with TOSOH TSKgel Super HZM-H, TOSOH TSKgel Super HZ4000, and TOSOH TSKgel Super HZ2000 (all trade names, manufactured by Tosoh Corporation) is used. Carrier: Tetrahydrofuran Measurement temperature: 40°C Carrier flow rate: 1.0 ml / min Sample concentration: 0.1 mass% Detector: RI (refractive index) detector

[0045] The pKa of the compound represented by formula (I) is not particularly limited and can take any appropriate value, preferably 0.1 to 12. The pKa can be measured by neutralization titration. The compound represented by formula (I) may have a substituent, and examples of the substituent that may be had include groups selected from the substituents GZ described below. The compound represented by formula (I) can be synthesized by known synthesis methods, for example, the synthesis method described in Patent Document 1, the synthesis method described in the Examples described below, and the like.

[0046] Specific examples of the compound represented by formula (I) include those shown below in addition to those synthesized in the examples, but the present invention is not limited to these.

[0047]

[0048] - Substituent GZ - an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), In the present invention, alkyl groups usually include cycloalkyl groups, but will be described separately here.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), aralkyl groups (preferably aralkyl groups having 7 to 23 carbon atoms, for example, benzyl, phenethyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably 5- or 6-membered heterocyclic groups having at least one oxygen atom, sulfur atom, or nitrogen atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups.For example, a tetrahydropyran ring group, a tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, a pyrrolidone group, etc.), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), a heterocyclic oxy group (the above heterocyclic group having -O- a group bonded to an -O-CO- group), an alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.), an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), a heterocyclic oxycarbonyl group (a group formed by bonding an -O-CO- group to the above heterocyclic group), an amino group (preferably an amino group having 0 to 20 carbon atoms, an alkylamino group, or an arylamino group, for example, amino(-NH ２), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl group (including an alkylcarbonyl group, an alkenylcarbonyl group, an alkynylcarbonyl group, an arylcarbonyl group, or a heterocyclic carbonyl group, preferably an acyl group having 1 to 20 carbon atoms, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, nicotinoyl, etc.), acyl Oxy groups (including alkylcarbonyloxy groups, alkenylcarbonyloxy groups, alkynylcarbonyloxy groups, and heterocyclic carbonyloxy groups, preferably acyloxy groups having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, and nicotinoyloxy), aryloyloxy groups (preferably aryloyloxy groups having 7 to 23 carbon atoms, for example, benzoyloxy and naphthoyloxy), carbamoyl groups (preferably carbamoyl groups having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino groups (preferably acylamino groups having 1 to 20 carbon atoms, for example, acetylamino, benzoylamino, etc.), alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio groups (preferably arylthio groups having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), heterocyclic thio groups (groups in which an -S- group is bonded to the above heterocyclic group), alkylsulfonyl groups (preferably alkylsulfonyl groups having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl groups (preferably an arylsulfonyl group having 6 to 22 carbon atoms, for example, benzenesulfonyl; an alkylsilyl group (preferably an alkylsilyl group having 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl; an arylsilyl group (preferably an arylsilyl group having 6 to 42 carbon atoms, for example, triphenylsilyl; an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl, triethoxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; a phosphoryl group (preferably a phosphoric acid group having 0 to 20 carbon atoms, for example, -OP(=O)(R, Ｐ ) ２ ), a phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, —P(═O)(R Ｐ ) ２ ), a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R Ｐ ) ２ ), a phosphonic acid group (preferably a phosphonic acid group having 0 to 20 carbon atoms, for example, —PO(OR Ｐ ) ２ ), sulfo group (sulfonic acid group), carboxy group, hydroxy group, sulfanyl group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). Ｐis a hydrogen atom or a substituent (preferably a group selected from the substituents GZ). Each of the groups listed as the substituents GZ may be further substituted with the substituent GZ. The alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group and / or alkynylene group may be cyclic or chain-like, and may be linear or branched.

[0049] [Method for Separating and Recovering Metal Ions] The method for separating and recovering metal ions of the present invention (hereinafter sometimes referred to as the separation and recovery method of the present invention) involves mixing an aqueous phase containing multiple metal ions with an oil phase containing the metal extractant of the present invention. This allows specific metal ions coordinated with the metal extractant of the present invention to be transferred (extracted) from the aqueous phase to the oil phase, allowing for separation and recovery with high selectivity, preferably with a high recovery rate. Here, the metal ions extracted into the oil phase may be a portion of the multiple metal ions contained in the aqueous phase, or all of the heterogeneous metal ions contained in the aqueous phase. The separation and recovery method of the present invention can extract one type of metal ion as a valuable metal element ion into the oil phase with high selectivity, preferably with a high recovery rate. However, it can also extract two or more heterogeneous metal ions, for example, one metal ion selected from two or more heterogeneous metal ions belonging to Groups 1 to 14 of the Periodic Table, into the oil phase with high selectivity, preferably with a high recovery rate. In particular, the separation and recovery method of the present invention can extract one of two or more different metal ions belonging to Groups 9 to 12 of the periodic table, particularly preferably cobalt ions and nickel ions, which are different metal ions from the same period, into an oil phase with high selectivity and preferably with a high recovery rate.The separation and recovery method of the present invention is based on the discovery of the characteristics and functions of the metal extractant of the present invention, which, although two or more metal ions (groups) of multiple metal ions present in the aqueous phase are extracted together into the oil phase in a wet extraction method, can extract one of the metal ions with high selectivity and preferably with a high recovery rate, and is applied to a new application of separating and recovering two or more metal ions, particularly different metal ions from different groups.

[0050] <Aqueous Phase> The water that forms the aqueous phase is not particularly limited, but (ultra) pure water, ion-exchanged water, etc. can be used.

[0051] The metal ions contained in the aqueous phase may contain at least two types of ions of metal elements belonging to Groups 1 to 14 of the periodic table, preferably at least two types of metal ions belonging to Groups 3 to 14, and may also contain metal ions belonging to Groups 15 to 17. In the present invention, the aqueous phase preferably contains two or more types of metal ions belonging to Groups 1 to 14, more preferably two or more types of metal ions belonging to Groups 3 to 14, and even more preferably contains ions of at least one transition metal element (metal element belonging to Groups 3 to 12). In an embodiment containing at least one transition metal element, the aqueous phase preferably contains two or more types of metal ions belonging to Groups 4 to 12, more preferably two or more types of metal ions belonging to Groups 4 to 10, even more preferably two or more types of metal ions belonging to Groups 8 to 12, particularly preferably two or more types of metal ions belonging to Groups 9 to 12, and most preferably two or more types of metal ions belonging to Groups 9 and 10. The metal ions belonging to each group are not particularly limited, but are preferably metal ions belonging to periods 4 to 6 of the periodic table, and more preferably metal ions belonging to periods 4 or 5. The number of types of metal ions is not particularly limited as long as it is two or more types, and can be, for example, 2 to 15 types, preferably 2 to 8 types, and more preferably 2 to 5 types. The combinations of multiple metal ions are not particularly limited, but examples of combinations of groups include combinations of Groups 9 and 10, combinations of Groups 9 and 12, combinations of Groups 9 and 11, combinations of Groups 9, 10 and 12, combinations of Groups 4 and 9, combinations of Groups 7, 9 and 10, and combinations of Groups 7, 8, 9 and 10. In the present invention, two or more types of metal ions belonging to each group may be used, but a single type is preferred in terms of exhibiting high selectivity.

[0052] Specific combinations of metal ions include, for example, combinations including Co and Ni, combinations including Co and Zn, combinations including Co and Cu, combinations including Rh and Ni, combinations including Zr and Rh, combinations including Mn, Co and Ni, and combinations of Mn, Fe, Co and Ni. The multiple types of metal ions contained in the aqueous phase may include metal ions of the same group, or may include metal ions of different groups. The number of types of different metal ions contained in the aqueous phase may be two or more, and is preferably, for example, two to four types, and more preferably two types.

[0053] The metal elements belonging to each group are not particularly limited, and appropriate atoms can be used. For example, preferred metal elements belonging to Group 1 include Li, Na, Rb, and Cs. Preferred metal elements belonging to Group 2 include Mg, Ca, Sr, and Ba. Preferred metal elements belonging to Group 3 include Sc and Y. Preferred metal elements belonging to Group 4 include Ti, Zr, and Hf. Preferred metal elements belonging to Group 5 include V, Nb, and Ta. Preferred metal elements belonging to Group 6 include Cr, Mo, and W. Preferred metal elements belonging to Group 7 include Mn and Tc. Preferred metal elements belonging to Group 8 include Fe, Ru, and Os. Preferred metal elements belonging to Group 9 include Co, Rh, and Ir. Preferred metal elements belonging to Group 10 include Ni, Pd, and Pt. Preferred metal elements belonging to Group 11 include Cu, Ag, and Au. Preferred examples of metal elements belonging to Group 12 include Zn, Cd, and Hg. Preferred examples of metal elements belonging to Group 13 include Al, Ga, In, and Tl. Preferred examples of metal elements belonging to Group 14 include Ga, Sn, and Pb. Preferred examples of metal elements belonging to Group 15 include Sb and Bi. Preferred examples of metal elements belonging to Group 16 include, but are not limited to, Te.

[0054] The multiple types of metal ions can be prepared appropriately, and examples thereof include various metal salts (salts of inorganic acids such as nitric acid and sulfuric acid of typical elements or organic acids such as acetic acid), mixtures of mined metals (ions), materials recovered from metal waste, metals recovered from other wastes such as waste batteries (LiBs), and mixtures thereof. Metals recovered from waste LiBs can be recovered by known methods such as wet treatment and electrolysis.

[0055] The total content of the plurality of metal ions in the aqueous phase is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 1,000,000 ppm by mass, preferably 1,000 to 100,000 ppm by mass, more preferably 1,000 to 80,000 ppm by mass, and even more preferably 2,000 to 60,000 ppm by mass. The total content of metal ions belonging to Groups 9 to 12 among the metal ions is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 80,000 ppm by mass, preferably 1,000 to 60,000 ppm by mass, and more preferably 2,000 to 60,000 ppm by mass. The total content of metal ions belonging to groups 3 to 7 and groups 13 to 16 among the metal ions is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 60,000 ppm by mass, preferably 1,000 to 30,000 ppm by mass. The content of metal ions belonging to each group is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 60,000 ppm by mass, preferably 1,000 to 50,000 ppm by mass, and more preferably 2,000 to 30,000 ppm by mass. When two or more types of metal ions belonging to each group are contained, the content of the metal ions belonging to each group is the total content.

[0056] In the present invention, when the aqueous phase contains metal ions of different groups, the content of metal ions belonging to one group may be greater or less than the content of metal ions belonging to another group. Because the separation and recovery method of the present invention can separate and recover metal ions with high selectivity, it is not necessary to set the content of metal ions belonging to different groups to a specific ratio. For example, the mass ratio of the content of metal ions belonging to a specific group (e.g., metal ions extracted at the maximum extraction rate) to the content of metal ions belonging to another group (e.g., metal ions other than the metal ions extracted at the maximum extraction rate (including metal ions that are not extracted)) [content of metal ions belonging to a specific group:content of metal ions belonging to another group] can be, for example, 100:1 to 10,000, preferably 100:10 to 5,000, more preferably 100:50 to 1,000, and even more preferably 100:70 to 250.

[0057] The pH of the aqueous phase is not particularly limited and can be set as appropriate. However, taking into consideration the solubility of metal ions, the formation of complex ions, and the like, it is preferably set to, for example, 0.1 to 10, and more preferably 2.0 to 9.0. The pH of the aqueous phase can be adjusted, for example, using an acid or alkali. Known acids can be used without particular limitation, and examples thereof include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, organic phosphoric acid, and organic sulfonic acid. Known alkalis can be used without particular limitation, and examples thereof include inorganic alkalis and organic alkalis, with inorganic alkalis being preferred. Examples of inorganic alkalis include metal alkalis such as hydroxides and carbonates of Group 1 or Group 2 metals, as well as aqueous ammonia and ammonium chloride. Examples of organic alkalis include organic ammonium salts. The temperature of the aqueous phase is not particularly limited and can be set to, for example, 10 to 60°C.

[0058] The aqueous phase may contain, as necessary, a ligand (compound) that coordinates with the metal ion or a compound that generates the ligand. The aqueous phase can be prepared by dissolving metal ions in water. The conditions for preparing the aqueous phase are not particularly limited. For example, the preparation temperature can be 10 to 60°C. The aqueous phase may contain a masking agent in addition to the metal ions. Any known masking agent can be used without any particular limitation. Examples of the masking agent include monodentate ligands such as ammonia and chelating agents such as dithizone.

[0059] <Oil Phase> In the separation and recovery method of the present invention, an oil phase (organic phase) containing one or more metal extractants of the present invention is used in addition to the aqueous phase. The metal extractant of the present invention exhibits solubility in organic solvents and is present in the oil phase, where it coordinates with metal ions present near the interface between the aqueous phase and the oil phase, thereby transferring these metal ions to the oil phase. In the present invention, solubility in organic solvents refers to the property of the metal extractant being soluble in organic solvents at the content described below.

[0060] The organic solvent forming the oil phase is not particularly limited, and any suitable organic solvent can be used. Examples include alcohol solvents, ether solvents, hydrocarbon solvents (aromatic solvents, aliphatic solvents), halogenated solvents, etc. Among these, hydrocarbon solvents are preferred, and various solvents that are fractions of petroleum are more preferred, and aromatic, paraffinic, naphthenic, kerosene, gasoline, naphtha, kerosene, and diesel hydrocarbon solvents are even more preferred.

[0061] The content of the metal extractant in the oil phase is appropriately set taking into consideration the content of metal ions, the amount of coordination to the metal ions, etc. For example, the content in the oil phase can be 20 to 10,000 mmol / L (mM), preferably 50 to 1,000 mmol / L, and more preferably 100 to 500 mmol / L. The temperature of the oil phase is not particularly limited and can be, for example, 10 to 60°C.

[0062] The oil phase may contain other appropriate components in addition to the acidic metal extractant of the present invention. The oil phase can be prepared by dissolving the metal extractant in an organic solvent. The preparation conditions for the oil phase are not particularly limited, and the preparation temperature can be, for example, 10 to 60°C.

[0063] (Contact, Mixing) In the separation and recovery method of the present invention, the aqueous phase and the oil phase are mixed and allowed to stand. The mixing and standing conditions are not particularly limited and can be set appropriately. For example, mixing can be performed using various mixing devices. Examples of mixing devices include a method using a magnetic stirrer (stirrer tip), a method using a mechanical stirrer, and a method using a mixer. The stirring conditions (stirring speed, stirring time, etc.) are sufficient as long as they allow mixing of the aqueous phase and the oil phase (conditions under which the metal extractant coordinates to the metal ion), and are set appropriately depending on the combination of metal ion and metal extractant, the mixing temperature, and the mixing device. For example, the stirring speed can be 80 rpm or more, preferably 100 to 200 rpm, as the rotation speed of the magnetic stirrer, etc. The stirring time is not uniquely determined by the stirring conditions, etc., but can be, for example, 10 minutes to 24 hours. In the present invention, since the aqueous phase and the oil phase can be separated at a high phase separation rate, the stirring speed can be set high and the stirring time can be set long. The mixing temperature is not particularly limited and can be, for example, 10 to 60°C. The standing conditions are not particularly limited and can be set appropriately as long as the aqueous phase and the oil phase separate into two layers. The standing time in the wet extraction method is usually set to 10 minutes to 24 hours after mixing is stopped. However, in the present invention, since the aqueous phase and the oil phase can be separated at a high phase separation rate, the standing time can be set shorter than usual, thereby increasing the productivity of the wet extraction method. In this case, the standing time can be, for example, less than 5 minutes after mixing is stopped, and preferably less than 4 minutes. The standing temperature is not particularly limited and can be, for example, 10 to 60°C.

[0064] When mixing the aqueous phase and the oil phase, the mixing ratio of the aqueous phase to the oil phase is appropriately set depending on the content (concentration) of the metal ions, the content (concentration) of the metal extractant, etc., and is not uniquely determined. For example, when mixing aqueous phases and oil phases satisfying the above concentrations, the ratio of the oil phase to 100 mL of aqueous phase can be 50 to 2,000 mL, preferably 80 to 1,000 mL, and more preferably 80 to 200 mL. On the other hand, when focusing on the metal ions present in the aqueous phase, it is preferable to mix the oil phase at a ratio where the metal extractant is 0.5 to 20 times the total molar content (moles) of the metal ions, and more preferably 0.5 to 10 molar amounts of the metal extractant. Furthermore, the content of the metal extractant relative to the total content of metal ions that can be coordinated by the metal extractant (also referred to as the mixing amount; the ratio of the number of moles of metal extractant to the total number of moles of metal ions: molar ratio) can be, for example, 0.5 to 10.0 equivalents, and preferably 0.5 to 6.0 equivalents. Here, the metal ions to which the metal extractant can be coordinated refer to metal ions that are coordinated with the metal extractant and extracted into the oil phase.

[0065] The pH of the mixed system can also be adjusted during the mixing of the aqueous phase and the oil phase. The pH set for a specific metal ion to be extracted is not unique and is determined appropriately, taking into consideration the pKa of the metal extractant, the complex formation constant between the metal extractant and the metal ion, the coordination number of the metal ion, and other factors. The pH of the mixed system is preferably 0.01 to 14, more preferably 0.1 to 10. From the standpoints of selectivity and phase separation rate, and also in terms of recovery rate, it is more preferably 0.5 to 7.0, particularly preferably 1.0 to 6.5, and most preferably 2.5 to 6.5. When separating and recovering metal ions belonging to Group 9 and Group 10, the pH of the aqueous phase is most preferably 3.0 to 6.5 within the above range. The pH can be adjusted using the above-mentioned acids or alkalis, or aqueous solutions thereof, but one preferred embodiment is to avoid the use of ammonia or ammonium salts. When adjusting the pH of the mixed system during mixing of the aqueous phase and the oil phase, the above-mentioned mixing of the aqueous phase and the oil phase and leaving to stand after mixing are carried out after adjusting the pH.

[0066] The aqueous phase and the oil phase are mixed in this manner, and the resulting two-phase separation fluid (solvent extraction phase, solvent extraction system) is one in which the aqueous phase and the oil phase are separated and exist in a layered state while in contact with each other. Of the multiple metal ions described above, the metal ions coordinate-bonded to the metal extractant are present (moved) in the oil phase. The number of metal ions extracted into the oil phase is ideally one, but may be two or more. In this case, the number can be, for example, 2 to 10, preferably 2 to 6, and more preferably 2 or 3. The two or more metal ions extracted into the oil phase from the multiple metal ions are not particularly limited, but are preferably the same as the two or more heterogeneous metal ions (combination) contained in the aqueous phase.

[0067] The separation and recovery method of the present invention, which is a simple method of mixing the aqueous phase and the oil phase and allowing them to stand, allows a specific metal ion from among multiple types of metal ions to be extracted, separated, and recovered with high selectivity, preferably with a high recovery rate, and in particular, allows ions of two or more metal elements to be extracted, while separating and recovering one of the metal ions with high selectivity, preferably with a high recovery rate.

[0068] The type of metal ion that can be separated and recovered with high selectivity, preferably with a high recovery rate, is not uniquely determined by the group or period of the metal ion, the content, the type of metal extractant, etc. For example, when extracting a metal ion belonging to Group 9 and a metal ion belonging to Group 10 into an oil phase, the metal ion belonging to Group 9 can be separated and recovered with high selectivity, preferably with a high recovery rate. In particular, when extracting Co ions as the metal ion belonging to Group 9 and Ni ions as the metal ion belonging to Group 10, the Co ions can be separated and recovered with high selectivity, preferably with a high recovery rate. Furthermore, when extracting a metal ion belonging to Group 9 and a metal ion belonging to Group 11 into an oil phase, the metal ion belonging to Group 11 can be separated and recovered with high selectivity, preferably with a high recovery rate. Furthermore, when metal ions belonging to Group 9, metal ions belonging to Group 10, and metal ions belonging to Group 12 are extracted into an oil phase, the metal ions belonging to Group 10 are usually not extracted, but the metal ions belonging to Group 12 can be separated and recovered with high selectivity, preferably at a high recovery rate.

[0069] As described above, the separation and recovery method of the present invention can extract and recover one or more metal ions from multiple metal ions present in an aqueous phase into an oil phase with high selectivity, preferably with a high recovery rate. In particular, the separation and recovery method of the present invention can extract two or more metal ions while recovering one of the metal ions with high selectivity, preferably with a high recovery rate. Therefore, by subjecting the aqueous phase containing two or more metal ions stripped from the oil phase to the separation and recovery method of the present invention, the selectivity for one metal ion can be further increased without significantly impairing the recovery rate, and as a result, high-purity metal ions can be recovered, preferably with a high recovery rate. Such a separation and recovery method of the present invention can also be referred to as a method for extracting two or more metal ions.

[0070] In the separation and recovery method of the present invention, the metal extractant can coordinate to metal ions alone and extract the metal ions into the oil phase, so the aqueous phase and the oil phase do not need to contain compounds that cooperate with the metal extractant of the present invention to extract metal ions, such as compounds that coordinate to metal ions or compounds that generate ligands, such as known metal extractants. The separation and recovery method of the present invention typically uses an aqueous phase containing a specific metal ion as an essential component and an oil phase containing the metal extractant of the present invention as an essential component.

[0071] The separation and recovery method of the present invention may include steps other than the step of mixing and allowing the aqueous phase and oil phase to stand. Examples of such steps include a step of premixing the aqueous phase and oil phase before adjusting the pH, a step of stripping (isolating) metal ions from the oil phase obtained by mixing and allowing the aqueous phase and oil phase to stand (a step of stripping metal ions from the oil phase to recover a metal extractant), a step of recovering the stripped metal ions as a compound (salt), a step of purifying the stripped metal ions or their compounds, a step of purifying the recovered metal extractant, and even a step of preliminarily removing ions of metal elements belonging to Group 1 or Group 2 of the periodic table. As a method for stripping (isolating) metal ions from the oil phase, known methods can be applied without particular limitation. For example, stripping (isolating) metal ions can be performed by acidifying the liquid phase, e.g., pH 2 to 4, using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. As a method for recovering the stripped metal ions as a compound, known methods can be applied without particular limitation.

[0072] The separation and recovery method of the present invention may be carried out as a batch process or a continuous process. The apparatus for carrying out the separation and recovery method of the present invention is not particularly limited, and known equipment can be used. Examples include a separatory funnel, a mixer settler, and the like. A contacting and mixing apparatus using a liquid delivery device such as a flow synthesis apparatus or an emulsion flow apparatus can also be used. The above-mentioned conditions can be applied to the contacting, mixing, and standing conditions in continuous processing. The amount of the aqueous phase used to flow can also be set to be greater than the above-mentioned mixing ratio of the aqueous layer to the oil phase.

[0073] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the following examples, "parts" and "%" representing compositions are based on mass unless otherwise specified. In the present invention, "room temperature" means 25°C.

[0074] [Synthesis and Preparation of Compounds] The compounds shown below were synthesized or prepared. PC-88A (mono-2-ethylhexyl (2-ethylhexyl)phosphonate) shown below was a commercially available product (manufactured by Tokyo Chemical Industry Co., Ltd.). VA-10 shown below was a commercially available product (Versatic acid 10, manufactured by Hexion).

[0075]

[0076] <Synthesis of Compound E-1> Compound E-1 was synthesized as follows. Specifically, 89 g of diethyl phosphite (manufactured by Tokyo Chemical Industry Co., Ltd.) and 450 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked recovery flask and stirred thoroughly. While the three-necked recovery flask was ice-cooled, 23.2 g of sodium hydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added and stirred for 20 minutes while still ice-cooled. Thereafter, the reaction solution was heated and stirred for 30 minutes under reflux. Next, while the three-necked recovery flask was ice-cooled, 70.0 g of 1-bromo-2-ethylhexane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise to the resulting reaction solution over 20 minutes, and the mixture was stirred at an internal temperature of 45°C for 24 hours. 300 g of water was added to the resulting reaction solution, followed by extraction with toluene, and the solvent was removed by distillation under reduced pressure to obtain 107 g of a yellow liquid.

[0077] Next, the obtained yellow liquid and 400 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked flask and stirred thoroughly. 113 g of bromotrimethylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added to the three-necked flask and stirred at room temperature for 4 hours. The solvent was removed from the obtained reaction solution by distillation under reduced pressure, and then 530 g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred at an internal temperature of 40°C for 3 hours. 200 mL of aqueous sodium hydroxide solution (4 mol / L) was added to the reaction solution obtained in this manner, and the aqueous layer was washed twice with toluene. 65 mL of concentrated hydrochloric acid was added to the obtained aqueous solution, and the mixture was extracted with toluene. The solvent was then removed by distillation under reduced pressure to obtain 43.6 g of compound A (yield 62%, 2 steps). 20.0 g of compound A and Fine Oxocol 1600K (branched C １６ H ３３ 25.0 g of cyclohexylcarbodiimide (manufactured by Nissan Chemical Industries, Ltd.) and 120 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and stirred, and the temperature was raised to a reflux state. A solution of 23.4 g of dicyclohexylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 120 g of tetrahydrofuran was added dropwise thereto over 3 hours, and the mixture was stirred for 4 hours. The resulting reaction solution was returned to room temperature, and the white solid was removed by filtration. The solvent was distilled off under reduced pressure from the resulting filtrate. The resulting crude product was dissolved in toluene and washed with water, and then the solvent was distilled off under reduced pressure to obtain 32.0 g (yield 74%) of compound E-1 as a pale yellow liquid.

[0078] The compound E-1 thus synthesized was identified as follows: Compound E-1 was dissolved in deuterated chloroform, １ H-NMR was measured (apparatus: BLUKER 400), and the resulting chart is shown in Figure 1. δ (ppm): 9.65 (1H, br s), 3.89 (2H, t, J = 5.6 Hz), 1.80-1.21 (36H, m), 0.91-0.86- (12H, m). Furthermore, the m / z 419 obtained by HPLC-MS was [M+H ＋ (Precise molecular weight of E-1: 418) From the above, the obtained compound was identified as having the structure shown in E-1 above.

[0079] <Synthesis of Compounds E-2 to E-6 and E-9> In the synthesis of compound E-1, 1-bromo-2-ethylhexane or Fine Oxocol 1600K was used in the synthesis of a compound having the formula R shown in the above-mentioned formula and Table 1 below. １ and R ２ Compounds E-2 to E-6 and E-9 were synthesized in the same manner as in the synthesis of compound E-1, except that the corresponding groups were introduced into the corresponding halides or alcohols.

[0080] <Synthesis of Compound E-7> Fine Oxocol 1600K (branch C) was placed in a 500 mL three-necked recovery flask. １６ H ３３ 30.0 g of tetrabromide (manufactured by Nissan Chemical Industries, Ltd.), 49.2 g of carbon tetrabromide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 160 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added, and the mixture was stirred while cooling in an ice bath. To the resulting reaction solution, a solution consisting of 48.7 g of triphenylphosphine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 130 g of dichloromethane was added dropwise over 10 minutes. The reaction solution was then warmed to room temperature and stirred for 2 hours. 4 M sodium hydroxide solution was added to this solution, and the mixture was extracted with dichloromethane. The solvent was then evaporated under reduced pressure to obtain the product (branch C １６ H ３３ Br) was obtained as a pale yellow liquid (yield 90%). 1.9 g of magnesium (Fujifilm Wako Pure Chemical Industries, Ltd.) and 100 g of diethyl ether were added to a 300 mL three-necked recovery flask and stirred at room temperature. 22.0 g of the above product was added dropwise to generate a Grignard reagent. Subsequently, 5.0 g of dibutyl phosphite was added while maintaining the temperature of the reaction solution below 15°C, and the reaction solution was then heated and stirred under reflux for 5 hours. While cooling the resulting reaction solution in an ice bath, 10% sulfuric acid was added dropwise, the organic layer was washed with a 15% aqueous sodium carbonate solution, and the solvent was distilled off under reduced pressure. The resulting product was purified by column chromatography to identify branched C １６ H ３３Phosphorous acid having two groups was obtained as a colorless, transparent liquid (yield 84%). 78 g of hydrogen peroxide solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 10.0 g of the above-mentioned phosphorous acid were added to a 200 mL three-necked recovery flask and stirred at room temperature. The reaction solution was then heated to 65°C and stirred for 24 hours. 100 g of saturated aqueous sodium thiosulfate solution was added, followed by extraction with toluene, and the solvent was evaporated under reduced pressure to obtain compound E-7 as a colorless, transparent liquid (yield 96%).

[0081] <Synthesis of Compound E-8> In a 1 L three-necked flask, 17.4 g of ethylenediphosphonic acid (Tokyo Chemical Industry Co., Ltd.) and Fine Oxocol 180 (branch C １８ H ３７ 49.5 g of N,N'-dicyclohexylcarbodiimide (DCC, manufactured by Nissan Chemical Industries, Ltd.) and 200 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and dissolved under reflux with stirring. Separately, 41.6 g of N,N'-dicyclohexylcarbodiimide (DCC, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 180 g of tetrahydrofuran were added to a 500 mL graduated cylinder and mixed to prepare a DCC solution. This DCC solution was added dropwise to the three-necked recovery flask described above over 3 hours, and after the completion of the addition, the mixture was stirred for an additional 5 hours. The resulting solution was allowed to cool at room temperature, and the precipitated white crystals were removed by filtration and washed with toluene. The solvent was removed from the filtrate by distillation under reduced pressure, yielding compound E-8 as a colorless, transparent liquid (yield 98%).

[0082] <Synthesis of Compound T-1> Compound T-1 was synthesized with reference to Example 1 of Patent Document 1.

[0083] <Synthesis of Compound T-2> Compound T-2 was synthesized in the same manner as in the synthesis of Compound E-1, except that Fine Oxocol 1600K was changed to isodecyl alcohol. The obtained Compound T-2 was identified in the same manner as Compound E-1.

[0084] Each compound synthesized as described above was identified in the same manner as compound E-1. １ and R ２The molecular weights and the number of carbon atoms of the substituents corresponding to the above are shown in Table 1. In Table 1, the substituents on the left side of the "P" atom in the basic structure of the chemical formula are represented by R １ , the right-hand substituent is R ２ It states that:

[0085]

[0086] [Preparation of metal ion-containing aqueous solution] 81.1 g of cobalt (II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 81.3 g of nickel (II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L volumetric flask, and the mixture was diluted with ultrapure water and stirred at 40 ° C. to dissolve the solution, thereby preparing a metal ion-containing aqueous solution (W1). Furthermore, metal ion-containing aqueous solutions (W2) to (W4) were prepared by dissolving each sulfate salt in ultrapure water in the combination of metal ions shown in the "Metal ion concentration (ppm) in the aqueous phase before extraction" column in Table 2-1. The pH of the prepared metal ion-containing aqueous solutions (W1) to (W4) was measured using a pH meter (SK-620pHII, manufactured by Satotec Co., Ltd.) and the results are shown below. Metal ion-containing aqueous solution (W1): 6.6 Metal ion-containing aqueous solution (W2): 6.2 Metal ion-containing aqueous solution (W3): 6.5 Metal ion-containing aqueous solution (W4): 7.0

[0087] <Preparation of Metal Extractant Solutions (Oil Phase)> Each synthesized or prepared compound was added to a 100 mL volumetric flask, and the mixture was diluted to a measuring volume with kerosene (Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature to prepare metal extractant solutions (Y1) to (Y9) and (Yc1) to (Yc4) (concentration 450 mM) containing each compound as a metal extractant.

[0088] [Example 1] 10 mL of the extractant solution (Y1) was added to 10 mL of the prepared metal ion-containing aqueous solution (W1) in a 30 mL vial, and the mixture was stirred at 25 ° C. for 30 minutes (rotation speed: 150 rpm) using a stirrer tip (diameter 6 mm, length 20 mm) (pre-mixing). At this time, the amount of compound E-1 mixed (unit: equivalent) relative to the total content of coordinating metal ions (synonymous with extracted metal ions, Co and Ni in Example 1) was 0.78. Thereafter, 10 M aqueous sodium hydroxide or 10 M hydrochloric acid was added to adjust the pH of the mixture to the value shown in the "pH at mixing" column in Table 2-2, and the mixture was further stirred at 25 ° C. for 30 minutes (rotation speed: 150 rpm), and then allowed to stand at the same temperature for 1 hour. After confirming that the organic phase (oil phase) and aqueous phase had separated into two phases, the aqueous phase was separated and the metal ions were separated and recovered. The pH of the mixed solution was measured using a pH meter (SK-620pHII, manufactured by Satotec Co., Ltd.) The metal ions extracted in Example 1 are shown in the "Type" column of the "Extracted Metal Ions" section of Table 2-2, and the metal ions extracted in the maximum amount are shown in the "Maximum Extracted Ions" column of the same section of Table 2-2.

[0089] Examples 2 to 12 and Comparative Examples 1 to 4 In Example 1, the metal ion-containing aqueous solution and the extractant solution were changed to the combinations shown in the "Aqueous Phase" column of Table 2-1 and the "Oil Phase" column of Table 2-2 (hereinafter, Table 2-1 and Table 2-2 are collectively referred to as Table 2), and the pH when the aqueous phase and the oil phase were mixed was set to the value shown in the "pH at Mixing" column of Table 2-2, and the mixture was allowed to stand. In each example, the extracted metal ions are shown in the "Type" column of the "Extracted Metal Ions" column in Table 2-2, and the metal ions extracted in the maximum amount are shown in the "Maximum Extracted Ions" column in the same column of Table 2-2.

[0090] The dissolved metal ion content of each aqueous phase used in the Examples and Comparative Examples, and each aqueous phase after extraction, was quantified using an inductively coupled plasma optical emission spectroscopy (ICP-OES) analyzer (Optima 7300D (trade name), manufactured by PerkinElmer). The measured values ​​of the dissolved metal ion content of each aqueous phase used in the Examples and Comparative Examples are shown in the "Metal ion concentration (ppm) in aqueous phase before extraction" column of Table 2-1, and the measured values ​​of the dissolved metal ion content of each aqueous phase after mixing in each Example and Comparative Example are shown in the "Metal ion concentration (ppm) in aqueous phase after extraction" column of Table 2-1. Note that the "," in the metal ion concentrations in the table indicates a separator between digits, not a decimal point.

[0091] <Evaluation 1: Evaluation of Selectivity (Separation Ability)> In each Example and Comparative Example, the extraction amount (difference, unit: ppm) of each metal ion was calculated from the metal ion concentration in the aqueous phase before the extraction and the metal ion concentration in the aqueous phase after the extraction, and the selectivity ratio was calculated as the ratio of the extraction amounts by dividing the extraction amount (ppm) of the maximum extraction amount of the metal ion by the total extraction amount (ppm) of the other metal ions. The results are shown in the "Selectivity Ratio" column in Table 2-2. In this test, a larger selectivity ratio indicates better selectivity (separation ability) for a specific metal ion, and a selectivity ratio of 3.0 or higher is acceptable.

[0092] <Evaluation 2: Phase separation rate> In each example and comparative example, the rate of phase separation between the aqueous phase and the oil phase was evaluated by measuring the time elapsed until the mixture separated into two phases when left to stand at 25°C after stirring for 30 minutes at 25°C. In this test, the shorter the elapsed time, the higher the phase separation rate, and an evaluation standard of "D" or higher is considered to be acceptable. - Evaluation standard - A: Less than 2 minutes B: 2 minutes or more but less than 3 minutes C: 3 minutes or more but less than 4 minutes D: 4 minutes or more but less than 5 minutes E: 5 minutes or more but less than 10 minutes F: 10 minutes or more

[0093]

[0094]

[0095] The results shown in Table 2 reveal the following: In the separation and recovery of metal ions by wet extraction, Comparative Examples 1 to 4, which used conventional metal extractants PC-88A, VA-10, T-1, and T-2, all extracted two types of metal ions present in the metal ion-containing aqueous solution (W1) into the oil phase. Moreover, because a large amount of Ni was also extracted in addition to Co, the selectivity of the maximum amount of Co ions extracted was low. Furthermore, in all of Comparative Examples 1 to 4, the time elapsed until separation into two phases was long (the phase separation rate was low), making the productivity of the wet extraction method inferior.

[0096] In contrast, in Examples 1 to 12, in which compounds E-1 to E-9 of the present invention were used as metal extractants, two types of metal ions present in the metal ion-containing aqueous solution were extracted into the oil phase. However, the metal ions extracted in the maximum amount (Examples 1 to 5, 8, and 10 to 12: Co ions, Example 6: Zn ions, Example 7: Cu ions, Example 9: Rh ions) were extracted almost entirely (with high recovery rates) from the aqueous phase into the oil phase with a high selectivity relative to metal ions other than the metal ions extracted in the maximum amount. Moreover, in all of Examples 1 to 12, the elapsed time until separation into two phases was short (high phase separation rate), which can increase the productivity of the wet extraction method.

[0097] The present experiments were carried out in the same manner as in Examples 1 to 12 and Comparative Examples 1 to 4, except that the metal ion concentration in the aqueous phase was reduced to 1 / 5, and similar results were obtained. Thus, it can be seen that when the compound of the present invention is used as a metal extractant in a wet extraction method, metal ions present in the aqueous phase can be separated and recovered with high selectivity and high recovery rate while rapidly separating the aqueous phase from the oil phase. Furthermore, it can be seen that a specific metal ion from two or more metal ions belonging to different groups that have similar physical and chemical behaviors, particularly one metal ion belonging to Groups 9 and 10 that can be recovered from waste LiB, can be separated and recovered with high selectivity and high recovery rate while rapidly separating the aqueous phase from the oil phase.

[0098] The above results demonstrate that stripping the oil phase obtained in each of the above examples using conventional methods and conditions can separate and recover metal ions extracted into the oil phase with high selectivity and recovery rate in a high yield without sacrificing high selectivity, and in a simple and highly productive manner. However, in technologies for recovering a specific metal ion from an aqueous phase containing multiple metal ions, it is generally difficult to recover the specific metal ion with high selectivity and recovery rate. Maintaining high selectivity results in a decrease in recovery rate, and multiple separation and recovery procedures are required to achieve a desired recovery rate. In contrast, the present invention allows for the simple and highly productive extraction of one of two different metal ions from the aqueous phase with high selectivity and almost the entire amount into the oil phase. Therefore, in light of the above-mentioned circumstances, the present invention is of great technical significance in that it allows for the recovery of one metal ion from the obtained oil phase with a high recovery rate and further improved selectivity, in a simple and few-step manner, and with high productivity.

[0099] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0100] This application claims priority based on Japanese Patent Application No. 2023-050476, filed in Japan on March 27, 2023, the contents of which are incorporated herein by reference.

Claims

1. A metal extractant that extracts metal ions present in an aqueous phase into an oil phase, A metal extractant containing a phosphonate ester compound or a phosphinic acid compound represented by the following formula (I): 【Chemistry 1】 In formula (I), R １ and R ２ each represents a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. However, at least one of R 1 and R 2 is a substituent containing a hydrocarbon group having one or more branched carbon atoms and 9 or more carbon atoms. Y Ｐ represents an oxygen atom or a sulfur atom. Z represents a hydroxy group, a sulfanyl group, or a hydroxyaryl group. L represents a single bond. n is 1.

2. The R １ and R ２ 2. The metal extractant according to claim 1, wherein at least one of the groups is a substituent containing any one of a nitrogen atom, an oxygen atom, and a sulfur atom.

3. The R １ and R ２ 2. The metal extractant according to claim 1, wherein at least one of the above is a substituent having a branched structure.

4. The R １ and R ２ 2. The metal extractant according to claim 1, wherein at least one of the above is a substituent containing a hydrocarbon group having 3 or more branched carbon atoms, or a substituent containing a hydrocarbon group having 9 or more carbon atoms.

5. The R １ and R ２ The metal extractant according to claim 1, wherein at least one of the following is a substituent containing a ring structure.

6. 2. The metal extractant according to claim 1, wherein the metal ions are ions of metal elements belonging to groups 1 to 14 of the periodic table.

7. 2. The metal extractant according to claim 1, which is used for extracting and separating two or more types of metal ions belonging to different groups in the periodic table.

8. A method for separating and recovering metal ions, comprising mixing an aqueous phase containing a plurality of types of metal ions with an oil phase containing the metal extractant according to any one of claims 1 to 7.

9. A phosphonate compound or a phosphinic acid compound represented by the following formula (I): 【Chemistry 2】 In formula (I), R １ and R ２ Each of R represents a substituent having a molecular weight of 100 or more, and at least one of the substituents has a molecular weight of 160 or more. １ and R ２ At least one of the groups is a substituent containing a hydrocarbon group having one or more branched carbon atoms and 9 or more carbon atoms. Y Ｐ represents an oxygen atom or a sulfur atom. Z represents a hydroxy group, a sulfanyl group, or a hydroxyaryl group. L represents a single bond. n is 1.

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