JP5854460B2 - Selective metal extractant containing piperazine alkyl derivatives - Google Patents

Description

  The present invention relates to a novel piperazine alkyl derivative that selectively adsorbs a metal, a metal extractant containing the compound, and a metal recovery method.

  Zinc is used for a negative electrode material such as a manganese battery or an alkaline battery, in addition to being used as a plating material for a steel sheet. Cadmium is an element belonging to the same group 12 as zinc, and is used not only for the plating material of the steel sheet, but also for the negative electrode material of the nickel-cadmium battery.

  Zinc is produced by refining zinc ore. Since cadmium often coexists in zinc ore, cadmium is also produced when refining zinc from zinc ore. For this reason, the process of isolate | separating and collect | recovering zinc and cadmium is needed at the time of refining zinc ore.

  Zinc and cadmium have similar physicochemical properties and behave accordingly. For this reason, it is difficult to selectively separate zinc and cadmium with ordinary separation means. Therefore, in order to produce high purity zinc and / or cadmium, it is necessary to develop a separation means with higher selectivity.

  Patent Document 1 describes a bis-benzimidazole composition as an extractant for extracting zinc. According to the said literature, zinc can be extracted from the zinc salt containing liquid containing cadmium by using said composition.

  Patent Document 2 describes a zinc selective extractant containing an N-substituted pyridone derivative as an active ingredient. According to this document, zinc can be extracted with high selectivity without extracting cadmium from a metal solution containing zinc and coexisting with cadmium.

  Patent Document 3 describes a method for separating and recovering zinc by extracting zinc by solvent extraction with 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester. According to this document, zinc can be efficiently separated from a solution containing a high concentration of cadmium.

JP-A-5-25139 JP 2007-126716 A JP 2008-106348 A

  As described above, various techniques have been developed as means for selectively separating zinc and cadmium, but no method for efficiently separating and recovering cadmium has yet been provided. In addition, since zinc sulfate aqueous solution, which is an intermediate material in zinc ore refining, and electrode waste liquid of nicad battery are strongly acidic aqueous solutions, in the case of an extractant with phosphorus or sulfur atoms as a ligand, the extractant is oxidized by oxidation. There was also a problem that it was easily denatured.

  Therefore, an object of the present invention is to provide means for selectively extracting cadmium or zinc ions from a solution containing one or more base metal ions selected from cadmium and zinc.

As a result of various studies on means for solving the above problems, the present inventor has found that the above object can be achieved by using a piperazine alkyl derivative having a lipid-soluble substituent introduced into piperazine, and has completed the present invention. .
That is, the gist of the present invention is as follows.

［式中、
R¹、R²、R³及びR⁴は、互いに独立して、水素、置換若しくは非置換の直鎖若しくは分岐鎖状C_8-18アルキル、C_8-18アルケニル若しくはC_8-18アルキニル、又は置換若しくは非置換の直鎖若しくは分岐鎖状C_7-18アリールアルキル若しくはC_8-18アリールアルケニルであり（但し、R¹が水素のとき、R²は水素ではなく、R³が水素のとき、R⁴は水素ではない）；
L¹及びL²は、互いに独立して、置換若しくは非置換の直鎖若しくは分岐鎖状C_1-5アルキレン、C_2-5アルケニレン若しくはC_2-5アルキニレンである］
で表される化合物。 (1) Formula I:

[Where:
R ¹ , R ² , R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _8-18 alkyl, C _8-18 alkenyl or C _8-18 alkynyl, or Substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (where R ¹ is hydrogen, R ² is not hydrogen and R ³ is hydrogen, R ⁴ is not hydrogen);
L ¹ and L ² are each independently a substituted or unsubstituted linear or branched C _1-5 alkylene, C _2-5 alkenylene or C _2-5 alkynylene]
A compound represented by

(2) The compound of (1), wherein R ¹ , R ² , R ³ and R ⁴ are 2-ethyl-hexane-1-yl and L ¹ and L ² are methylene.

  (3) A metal ion extractant containing the compound (1) or (2).

  (4) The extractant according to (3), wherein the metal ion is at least one metal ion selected from the group consisting of gold, palladium, platinum, cadmium and zinc.

  (5) Recovery of metal ions, comprising an extraction step in which an aqueous phase containing metal ions and an organic phase containing the compound of (1) or (2) are brought into contact with each other to extract metal ions into the organic phase. Method.

  (6) The method according to (5) above, wherein the metal ion is at least one metal ion selected from the group consisting of gold, palladium, platinum, cadmium and zinc.

  According to the present invention, it is possible to provide means for selectively extracting cadmium or zinc ions from a solution containing one or more base metal ions selected from cadmium and zinc.

It is process drawing which shows one Embodiment of the collection | recovery method of the metal ion of this invention. FIG. 3 is a diagram showing the extraction results of hydrochloric acid by the compound of Example 1 (1,4-di {[di (2-ethylhexyl) carbamoyl] methyl} piperazine; DDCMP). FIG. 2 is a graph showing the effect of equilibrium hydrochloric acid concentration on the extraction rate of various metal ions from a hydrochloric acid solution by the compound of Example 1 (DDCMP). FIG. 4 is a diagram showing the extraction equilibrium arrival time of cadmium (II) by the compound of Example 1 (DDCMP). FIG. 3 is a graph showing the effect of equilibrium hydrochloric acid concentration on the distribution ratio of cadmium (II) by the compound of Example 1 (DDCMP). 2 is a graph showing the influence of hydrogen ion concentration on the distribution ratio of cadmium (II) by the compound of Example 1 (DDCMP). FIG. 2 is a graph showing the influence of chloride ion concentration on the distribution ratio of cadmium (II) by the compound of Example 1 (DDCMP). FIG. FIG. 3 is a graph showing the effect of extractant concentration on the distribution ratio of cadmium (II) by the compound of Example 1 (DDCMP). FIG. ₂ is a diagram showing a presumed structure of a complex of the compound of Example 1 (DDCMP) and CdCl ₂ . FIG. 2 is a graph showing the time for reaching the extraction equilibrium of zinc (II) with the compound (DDCMP) of Example 1. FIG. 3 is a graph showing the effect of equilibrium hydrochloric acid concentration on the distribution ratio of zinc (II) by the compound of Example 1 (DDCMP). 2 is a graph showing the influence of hydrogen ion concentration on the distribution ratio of zinc (II) by the compound of Example 1 (DDCMP). FIG. 2 is a graph showing the influence of chloride ion concentration on the distribution ratio of zinc (II) by the compound of Example 1 (DDCMP). FIG. FIG. 3 is a graph showing the influence of extractant concentration on the distribution ratio of zinc (II) by the compound of Example 1 (DDCMP). FIG. ₂ is a diagram showing a presumed structure of a complex of the compound of Example 1 (DDCMP) and ZnCl ₂ .

で表される化合物に関する。 Hereinafter, preferred embodiments of the present invention will be described in detail.
<1. Piperazine alkyl derivatives>
The present invention provides compounds of formula I:

It relates to a compound represented by

As used herein, “alkyl” means a straight or branched chain aliphatic hydrocarbon group containing the specified number of carbon atoms. For example, “C _1-18 alkyl” means a straight or branched hydrocarbon chain containing at least 1 and at most 18 carbon atoms. Suitable alkyls include but are not limited to, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n -Octyl, 2-ethylhexyl, 3-methyl-1-isopropylbutyl, 2-methyl-1-isopropylbutyl, 1-tert-butyl-2-methylpropyl, n-nonyl, 3,5,5-trimethylhexyl, decyl , Undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl.

  In the present specification, “alkenyl” means a group in which one or more C—C single bonds of the alkyl are substituted with double bonds. Suitable alkenyls include, but are not limited to, vinyl, 1-propenyl, allyl, 1-methylethenyl (isopropenyl), 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-2-propenyl, 2 -Methyl-2-propenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-pentenyl, 1-hexenyl, n-heptenyl, 1-octenyl, 1-nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl Tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, octadecenyl and the like.

  In the present specification, “alkynyl” means a group in which one or more C—C single bonds of the alkyl are substituted with triple bonds. Suitable alkynyls include but are not limited to ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-methyl-2-propynyl, 1-pentynyl, 1-hexynyl 1-heptynyl, 1-octynyl, 1-noninyl, decynyl, undecynyl, dodecynyl, tridecynyl, tetradecynyl, pentadecynyl, hexadecynyl, heptadecynyl and octadecynyl.

  In the present specification, “aryl” means an aromatic ring group having 6 to 15 carbon atoms. Suitable aryls include, but are not limited to, phenyl, naphthyl, anthryl (anthracenyl), and the like.

  In the present specification, “arylalkyl” means a group in which one of hydrogen atoms of the alkyl is substituted with the aryl. Suitable arylalkyls include, but are not limited to, benzyl, 1-phenethyl, 2-phenethyl, and the like.

  In the present specification, “arylalkenyl” means a group in which one of the hydrogen atoms of the alkenyl is substituted with the aryl. Suitable arylalkenyl includes, but is not limited to, styryl.

The groups described above are each independently unsubstituted or one or more C _1-18 alkyl, C _2-18 alkenyl, C _2-18 alkynyl, C _6-15 aryl, C _7-18 arylalkyl, C _8-18 arylalkenyl, C (O) Z (Z is hydrogen, hydroxyl, C _1-18 alkyl, C _2-18 alkenyl, C _2-18 alkynyl or NH _2), OH , QC _1-18 alkyl, QC _2-18 alkenyl, QC _2-18 alkynyl, QC _6-15 aryl, QC _7-18 arylalkyl (Q is O or S), halogen, NO ₂ , or NR ^A R It can also be substituted by ^B (R ^A and R ^B are, independently of one another, hydrogen, C _1-18 alkyl, C _2-18 alkenyl or C _2-18 alkynyl).

  In the present specification, “halogen” or “halo” means fluorine, chlorine, bromine or iodine.

  The present inventor has found that by using a piperazine alkyl derivative represented by the formula I, a noble metal ion can be selectively extracted from an aqueous hydrochloric acid solution containing a base metal (base metal) ion and a noble metal ion. Further, it has been found that when a hydrochloric acid aqueous solution containing base metal (base metal) ions and noble metal ions has a low hydrochloric acid concentration, ions of cadmium or zinc can be selectively extracted from the aqueous solution. The piperazine alkyl derivative represented by the formula I is a novel compound found by the present inventors.

In the compound represented by formula I, R ¹ , R ² , R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _8-18 alkyl, C _8-18. Alkenyl or C _8-18 alkynyl, or substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that when R ¹ is hydrogen, R ² is not hydrogen Preferably, when R ³ is hydrogen, R ⁴ is not hydrogen), substituted or unsubstituted linear or branched C _8-18 alkyl, C _8-18 alkenyl or C _8-18 alkynyl, or It is more preferably a substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl, a substituted or unsubstituted linear or branched C _8-18 alkyl, C ₈ to be _-18 alkenyl or C _8-18 alkynyl Preferably, the 2-ethyl - it is especially preferred is hexane-1-yl.

In the compound represented by formula I, L ¹ and L ² are each independently a substituted or unsubstituted linear or branched C _1-5 alkylene, C _2-5 alkenylene or C _2-5 alkynylene. Preferably, it is more preferably methylene, ethylene or propylene, particularly preferably methylene.

Preferably, the compound of formula I is such that R ¹ , R ² , R ³ and R ⁴ are independently of one another hydrogen, substituted or unsubstituted linear or branched C _8-18 alkyl, C _8-18 alkenyl or C _8-18 alkynyl, or substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that when R ¹ is hydrogen, R ² Is not hydrogen and when R ³ is hydrogen, R ⁴ is not hydrogen);
L ¹ and L ² are each independently a substituted or unsubstituted linear or branched C _1-5 alkylene, C _2-5 alkenylene or C _2-5 alkynylene.

More preferably, in the compound represented by formula I, R ¹ , R ² , R ³ and R ⁴ are independently of each other a substituted or unsubstituted linear or branched C _8-18 alkyl, C _{8 -18} alkenyl or C _8-18 alkynyl, or substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl;
L ¹ and L ² are each independently a substituted or unsubstituted linear or branched C _1-5 alkylene, C _2-5 alkenylene or C _2-5 alkynylene.

  Particularly preferably, the compound of the formula I is 1,4-di {[di (2-ethylhexyl) carbamoyl] methyl} piperazine (DDCMP).

  The compound represented by Formula I of the present invention may be in the form of a salt or a solvate. In the present specification, the “compound represented by the formula I” means not only the compound itself but also a salt or solvate thereof. Examples of the salt of the compound represented by formula I include, but are not limited to, hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, carbonic acid, perchloric acid, formic acid, acetic acid, maleic acid, fumaric acid, benzoic acid, oxalic acid Preferred are salts with inorganic or organic acids such as citric acid or adipic acid.

  By using the compound represented by formula I in the form as described above, ions of a specific noble metal such as gold, palladium or platinum, or cadmium from an aqueous solution containing base metal ions and / or noble metal ions Alternatively, specific base metal ions such as zinc can be selectively extracted.

<2. Manufacturing method of piperazine alkyl derivative>
The present invention also relates to a process for producing the compound of formula I described above.

［式中、R¹、R²及びL¹は、式Iについて定義したものと同様の意味を表し、X²はハロゲンである］
で表されるハロゲン化アシルアミドと、式IIb：

［式中、R³、R⁴及びL²は、式Iについて定義したものと同様の意味を表し、X²はハロゲンである］
で表されるハロゲン化アシルアミドと、ピペラジンとを反応させてピペラジンをアルキル化するピペラジンアルキル化工程
を含む方法によって製造することが出来る。 The compound of formula I is represented by formula IIa:

[Wherein R ¹ , R ² and L ¹ represent the same meaning as defined for formula I, and X ² is halogen]
A halogenated acylamide of formula IIb:

[Wherein R ³ , R ⁴ and L ² represent the same meaning as defined for formula I and X ² is halogen]
It can manufacture by the method including the piperazine alkylation process of reacting the halogenated acylamide represented by these, and piperazine, and alkylating piperazine.

［式中、L¹は、式Iについて定義したものと同様の意味を表し、X¹及びX²はハロゲンである］
で表されるハロゲン化アシルハライドと、式IVa：
R¹-NH-R² IVa
［式中、R¹及びR²は、式Iについて定義したものと同様の意味を表す］
で表される二級アミンとを反応させて、ハロゲン化アシルハライドをアミド化するアシルアミド化工程
によって、
また、式IIbで表されるハロゲン化アシルアミドは、式IIIb：

［式中、L²は、式Iについて定義したものと同様の意味を表し、X¹及びX²はハロゲンである］
で表されるハロゲン化アシルハライドと、式IVb：
R³-NH-R⁴ IVb
［式中、R³及びR⁴は、式Iについて定義したものと同様の意味を表す］
で表される二級アミンとを反応させて、ハロゲン化アシルハライドをアミド化するアシルアミド化工程
によって、それぞれ製造することが出来る。 The halogenated acylamide represented by Formula IIa is represented by Formula IIIa:

[Wherein L ¹ represents the same meaning as defined for formula I and X ¹ and X ² are halogen]
An acyl halide halide represented by formula IVa:
R ¹ -NH-R ² IVa
[Wherein R ¹ and R ² represent the same meaning as defined for formula I]
By an acylamidation step in which a halogenated acyl halide is amidated by reacting with a secondary amine represented by
The halogenated acylamide represented by Formula IIb is represented by Formula IIIb:

[Wherein L ² represents the same meaning as defined for formula I and X ¹ and X ² are halogen]
An acyl halide halide represented by formula IVb:
R ³ -NH-R ⁴ IVb
[Wherein R ³ and R ⁴ represent the same meaning as defined for formula I]
It can be produced by an acylamidation step in which a halogenated acyl halide is amidated by reacting with a secondary amine represented by the formula:

  The piperazine alkylation step is preferably carried out under basic conditions. In this case, the base used is preferably triethylamine, potassium carbonate, sodium hydroxide, methoxysoda or NaH. This step is preferably carried out in the presence of an aprotic solvent such as chloroform, toluene, xylene or THF. The reaction temperature is preferably in the range of 50 to 100 ° C., and the reaction time is preferably in the range of 24 to 48 hours.

  The acylamidation step is preferably carried out under basic conditions. In this case, the base used is preferably triethylamine. This step is preferably carried out in the presence of an aprotic solvent such as chloroform, toluene, xylene or THF. The reaction temperature is preferably in the range of 0 to 25 ° C., and the reaction time is preferably in the range of 1 to 5 hours.

The method for producing a compound represented by formula I of the present invention includes a piperazine alkylation step. Further, in addition to the piperazine alkylation step, an acylamidation step may be further included.
By the above method, the compound represented by the formula I can be produced.

<3. Metal ion extractant>
In this specification, the “base metal” means a metal that is not included in the noble metal among non-ferrous metals, and specifically, aluminum (Al), copper (Cu), zinc (Zn), and lead (Pb). And rare metals such as titanium (Ti), nickel (Ni), cadmium (Cd) and tungsten (W).

  In this specification, “noble metal” means ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au). means.

  The metal ion extractant of the present invention is gold (III), palladium (II) or platinum (IV) from a solution containing one or more base metal ions and / or one or more noble metal ions. It can be used to selectively extract noble metal ions or base metal ions which are cadmium (II) or zinc (II). More specifically, even if rhodium (III) is present in a solution containing gold (III), palladium (II) and / or platinum (IV), gold (III), palladium (II) Alternatively, platinum (IV) can be selectively extracted. Further, even if nickel (II), manganese (II) and / or cobalt (II) is present in a solution containing cadmium (II) and / or zinc (II), cadmium (II) or Zinc (II) can be selectively extracted.

  Therefore, the metal ion extractant of the present invention is preferably used for selectively extracting ions of at least one metal selected from the group consisting of gold, palladium, platinum, cadmium and zinc, More preferably, it is used for selectively extracting ions of at least one base metal selected from the group consisting of cadmium and zinc.

  The metal ion extractant of the present invention may contain only the compound represented by Formula I, and in addition to the compound, a dilution containing one or more organic solvents and / or one or more additives. An agent may be further contained. Examples of the organic solvent include, but are not limited to, toluene, benzene, xylene, chloroform, 1,2-dichloroethane, carbon tetrachloride, n-hexane, and cyclohexane. Toluene is preferred. Examples of the additive include, but are not limited to, 2-ethylhexyl alcohol, octanol, decanol, and nonylphenol. 2-ethylhexyl alcohol is preferred. In this case, it is preferable that the concentration of the additive is set so as to be in the range of 5 to 20% by mass with respect to the total mass of the metal ion extractant.

  By containing the components as described above, the metal ion extractant of the present invention is obtained from a solution containing one or more base metal ions and / or one or more noble metal ions from gold, palladium or platinum. It is possible to selectively extract ions of a noble metal that is or a base metal ion that is cadmium or zinc.

<4. Metal ion recovery method>
Usually, in an acidic aqueous solution of metal ions, the metal ions form a neutral complex or an anionic complex ion with a conjugate base of the acid. Thus, metal ions can form an equilibrium state consisting of metal ions and some form of complex or complex ion, depending on the acid concentration and pH.

  The compound represented by the formula I of the present invention has an amine capable of forming a complex with an anion. The inventor appropriately adjusts the acid concentration of an aqueous solution containing one or more types of base metal ions and / or one or more types of noble metal ions, and an aqueous phase composed of the aqueous solution and Formula I of the present invention. Selective extraction of gold (III), palladium (II) or platinum (IV), or cadmium (II) or zinc (II) into the organic phase by contacting with the organic phase containing the represented compound I found what I can do. Therefore, the present invention relates to a method for recovering metal ions using the compound represented by formula I of the present invention.

  FIG. 1 is a process diagram showing an embodiment of the method for recovering metal ions of the present invention. Hereinafter, a preferred embodiment of the method of the present invention will be described in detail with reference to FIG.

[3-1. Extraction process]
In the method of the present invention, an aqueous phase containing a metal ion is brought into contact with an organic phase containing a compound represented by the formula I (the metal extractant of the present invention) to extract the metal ion into the organic phase. Including an extraction step (step S1).

In the present specification, the “aqueous phase containing metal ions” means an aqueous solution (aqueous phase) containing metal ions. Here, the metal ion is preferably an ion of at least one metal selected from the group consisting of gold, palladium, platinum, cadmium and zinc, and at least one selected from the group consisting of cadmium and zinc. More preferably, it is a type of base metal ion. The metal ion is preferably in a concentration of 1 × 10 ^{−4 to} 0.1 M, more preferably 1 × 10 ⁻³ to 1 × 10 ⁻² M in the aqueous phase.

The aqueous phase used in this step comprises ions of noble metal and base metal as described above in addition to ions of at least one metal selected from the group consisting of gold, palladium, platinum, cadmium and zinc. Other metal ions may be contained. For example, even when rhodium (III) is present in an aqueous phase containing gold (III), palladium (II) and / or platinum (IV), gold (III), palladium (II) or platinum ( Each of IV) can be selectively extracted. Further, even if nickel (II), manganese (II) and / or cobalt (II) is present in the aqueous phase containing cadmium (II) and / or zinc (II), cadmium (II) Alternatively, zinc (II) can be selectively extracted. In this case, the other metal ions are each independently preferably at a concentration of 1 × 10 ^{−5 to} 0.1 M, and more preferably at a concentration of 1 × 10 ^{−4 to} 0.01 M. Such aqueous phases include, for example, electrode waste liquids of zinc ore or nickel cadmium batteries, electronic equipment wastes, aldehyde production waste liquids by oxo reaction, and waste metal catalysts such as automobile exhaust gas catalysts, plating waste liquids, and Etching waste liquid can be used. Even when the aqueous phase used in this step contains other metal ions, the method of the present invention comprises noble metal ions selected from the group consisting of gold, palladium and platinum, or cadmium and zinc. It becomes possible to selectively extract base metal ions selected from the group.

The metal ions in the aqueous phase usually exist in the equilibrium state of a salt or complex (ion) of the acid with the conjugate base. For example, when the aqueous phase containing cadmium (II) or zinc (II) is an aqueous hydrochloric acid solution, cadmium (II) is CdCl ₂ , CdCl ₃ ⁻ , CdCl ₄ ²⁻ , CdCl ₅ ³⁻ or CdCl ₆ ⁴⁻ Zinc (II) is present in the form of a complex such as ZnCl ₂ , ZnCl ₃ ⁻ or ZnCl ₄ ²⁻ respectively. Here, when the aqueous phase containing the metal ion in the form of the above complex is brought into contact with the organic phase containing the compound represented by the formula I, the amino group of the compound represented by the formula I becomes cadmium (II ) Or zinc (II) complexes to form new complexes. The complex can exist stably in the organic phase due to the contribution of the fat-soluble substituent of the compound represented by Formula I, so that cadmium (II) or zinc (II) can be extracted into the organic phase. It becomes.

  As described above, since the metal ions in the aqueous phase exist in an equilibrium state of a salt or a complex (ion), the equilibrium state can change depending on the acid concentration of the aqueous phase. Therefore, desired metal ions can be selectively extracted from an aqueous solution containing base metal ions and noble metal ions by appropriately adjusting the acid concentration of the aqueous phase.

Examples of the acid contained in the aqueous phase include, but are not limited to, mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as formic acid, acetic acid, and oxalic acid. Hydrochloric acid or nitric acid is preferred. Only one kind of acid may be used, or a mixture of two or more kinds of acids may be used. The acid is preferably in a concentration of 1 × 10 ⁻² to 10 M.

  More specifically, the aqueous phase used in this step preferably contains 0.01 to 8 M acid when gold (III) is selectively extracted. When palladium (II) is selectively extracted, it is preferable to contain 0.01 to 6 M acid. When platinum (IV) is selectively extracted, it is preferable to contain 0.01 to 6 M acid. When selectively extracting cadmium (II), it is preferable to contain 0.01-8 M acid. In addition, when zinc (II) is selectively extracted, it is preferable to contain 0.01 to 8 M acid. In the above case, the acid used is preferably hydrochloric acid or nitric acid.

  The organic phase used in this step contains a compound represented by the formula I of the present invention or a metal extractant. The organic phase may be in the form of a liquid phase, containing the compound represented by Formula I of the present invention in the form of a solid, or in the form of a solid phase in which the compound is bound or impregnated on a support. May be.

  When the organic phase is in the form of a liquid phase, a diluent containing the compound of formula I of the present invention and optionally one or more organic solvents and / or one or more additives as described above A solution or dispersion further containing can be used as the organic phase. When the compound represented by Formula I is in a liquid form at normal temperature, it is preferable to use the compound as it is or in a form diluted with the above-mentioned diluent. In this case, the compound represented by Formula I is preferably at a concentration of 0.01 to 0.5 M.

  When the organic phase is in the form of a solid phase, if the compound represented by the formula I is in a solid form at room temperature, it can be used as it is in contact with the aqueous phase. In addition, the compound represented by the formula I may be dissolved in an organic solvent and impregnated in a support. Examples of the carrier (resin) for impregnation include, but are not limited to, polystyrene resin, cellulose triacetate, polyacrylate resin, activated carbon, hydrophobic zeolite, silica, and polyvinyl chloride resin. I can do it. Polystyrene resin, cellulose triacetate, polyacrylic acid ester or polyvinyl chloride resin is preferred. In this case, the compound represented by the formula I is preferably impregnated in the support in the range of 1 to 5 mmol / g support.

  In this step, various means commonly used in the technical field can be used as the means for bringing the aqueous phase into contact with the organic phase. When the organic phase is in the form of a liquid phase, it is preferable to use a batch method or a continuous extraction method. When the organic phase is in the form of a solid phase, it is preferable to use a batch method or a column method.

  When the organic phase is in the form of a liquid phase, the volume ratio of the aqueous phase to the organic phase is preferably in the range of 1:10 to 10: 1, and more preferably in the range of 1: 5 to 5: 1. preferable. The temperature at which the aqueous phase and the organic phase are brought into contact with each other is preferably in the range of 5 to 50 ° C. Moreover, in the case of a batch method, it is preferable that the time which makes an aqueous phase and an organic phase contact is the range of 0.5 to 48 hours.

  When the organic phase contains a compound represented by Formula I that is in a solid form at room temperature, or when the compound is impregnated in a carrier, it generally depends on the concentration of metal ions in the aqueous solution. It is preferable to use an organic phase of about 1 to 5 g with respect to 1 L of liquid phase. The temperature at which the aqueous phase and the organic phase are brought into contact with each other is preferably in the range of 5 to 50 ° C. Moreover, in the case of a batch method, it is preferable that the time which makes an aqueous phase and an organic phase contact is the range of 0.5 to 48 hours.

  By carrying out this step under the above conditions, it becomes possible to selectively extract a desired metal into the organic phase.

[3-2. Desorption process]
In the method of the present invention, an organic phase containing a metal ion and an aqueous phase are phase-separated, and then the organic phase is brought into contact with the desorption aqueous solution to desorb the metal ion from the organic phase into the desorption aqueous solution. A desorption step (step S2) for (back extraction) may be included.

  The desorption aqueous solution used in this step is not limited, but examples thereof include water, hydrochloric acid, perchloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, maleic acid, fumaric acid, benzoic acid, and oxalic acid. One or more acidic aqueous solutions selected from the group consisting of acids, citric acid and adipic acid, one or more alkaline aqueous solutions selected from the group consisting of aqueous ammonia, sodium hydroxide and potassium hydroxide, thiourea, thiocyanic acid Mention may be made of chelating compounds such as ammonium and sodium thiocyanate, ethylenediaminetetraacetic acid (EDTA), and mixtures thereof (for example mixtures of thiourea and hydrochloric acid). When back-extracting ions of at least one metal selected from the group consisting of gold, palladium and platinum, ammonia water, aqueous thiourea solution, mixed aqueous solution of thiourea and hydrochloric acid, ammonium thiocyanate, sodium thiocyanate or EDTA Preferably there is. When back-extracting ions of at least one metal selected from the group consisting of cadmium and zinc, water, aqueous ammonia, aqueous hydrochloric acid, aqueous perchloric acid, aqueous nitric acid, aqueous sulfuric acid, phosphoric acid, formic acid, acetic acid, maleic An acid, fumaric acid, benzoic acid, oxalic acid, citric acid or adipic acid is preferred. In the above case, the acidic aqueous solution preferably has a concentration of 0.1 to 3M. The alkaline aqueous solution preferably has a concentration of 0.1 to 3M. The thiourea, ammonium thiocyanate and sodium thiocyanate aqueous solution are preferably at a concentration of 0.1 to 3M. The aqueous solution of the chelate compound preferably has a concentration of 0.01 to 0.1 M.

  When the organic phase is in the form of a liquid phase, the volume ratio of the organic phase to the desorption aqueous solution is preferably in the range of 1:10 to 10: 1, and preferably in the range of 1: 5 to 5: 1. More preferred. The temperature at which the organic phase is brought into contact with the desorbed aqueous solution is preferably in the range of 5 to 50 ° C. In the case of the batch method, the time for bringing the organic phase into contact with the desorbed aqueous solution is preferably in the range of 0.5 to 48 hours.

  When the organic phase contains a compound represented by Formula I that is in a solid form at room temperature, or when the compound is impregnated in a support, 30 to 100 mL of desorption aqueous solution is added to 1 g. It is preferable to use it. The temperature at which the organic phase is brought into contact with the desorbed aqueous solution is preferably in the range of 5 to 50 ° C. In the case of the batch method, the time for bringing the organic phase into contact with the desorbed aqueous solution is preferably in the range of 0.5 to 48 hours.

  By carrying out this step under the above conditions, desired metal ions can be efficiently recovered.

  After completion of this step, the compound represented by formula I may be washed by treating with a strong acid (such as hydrochloric acid or nitric acid) and / or a strong alkali (such as sodium hydroxide) to remove impurities. . The washed compound can be reused in the method of the present invention. Therefore, the method of the present invention may include a washing step (step S3) in which the organic phase is treated with a strong acid and / or strong alkali after the metal is desorbed in the desorption aqueous solution.

  As described above, by carrying out the method of the present invention, from a solution containing one or more base metal ions and / or one or more noble metal ions, a noble metal ion that is gold, palladium, or platinum, Alternatively, it becomes possible to selectively extract ions of base metal that is cadmium or zinc.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the technical scope of the present invention is not limited to these examples.

<Example 1: Synthesis of 1,4-di {[di (2-ethylhexyl) carbamoyl] methyl} piperazine (DDCMP)>

  0.16 mol (38.6 g) di (2-ethylhexyl) amine and 0.16 mol (16.2 g) triethylamine were mixed in chloroform and stirred in an ice bath for about 4 hours. To this mixed solution, 0.18 mol (19.9 g) of chloroacetyl chloride was dropped in an ice bath. After the dropwise addition, the mixture was further stirred at room temperature for 19 hours. After stopping the reaction, the obtained chloroform solution was sufficiently washed with distilled water. The chloroform solution was dehydrated with sodium sulfate, and then chloroform was distilled off under reduced pressure to obtain 2-chloro-N, N-di (2-ethylhexyl) acetamide (CDEHAA).

20 mmol (1.72 g) piperazine and 40 mmol (4.05 g) triethylamine were dissolved in 50 cm ³ of chloroform, and 40 mmol (12.7 g) of CDEHAA was added dropwise with stirring at room temperature. After the dropping, the mixture was stirred and refluxed at 60 ° C. for 31 hours. The reaction time was determined by thin layer chromatography (TLC) (developing solvent hexane: ethyl acetate = 5: 1). After the reaction was stopped, the resulting chloroform solution was washed successively with brine and hydrochloric acid to remove unreacted CDEHAA and triethylamine. At this time, it was confirmed that the pH of the aqueous phase after phase separation was 1. Since hydrochloric acid remained in the phase-separated chloroform solution, the chloroform solution was washed with sodium hydroxide and distilled water until the pH after phase separation became around 7, and the hydrochloric acid was removed. The chloroform solution was dehydrated with sodium sulfate, and chloroform was distilled off under reduced pressure.

The product obtained was a brown liquid. The yield was 80%. The structure of the product was determined by FT-IR and ¹ H-NMR. ¹ H NMR (400 MHz, CDCl ₃ , TMS standard): δ = 3.26 (t, J = 3.8Hz, 8H), δ = 3.20 (s, 4H), δ = 2.82 (d, 4H), δ = 2.56 ( d, 4H), δ = 1.67 (m, 4H), δ = 1.26 (m, 32H), δ = 0.90 (m, 24H).

<Example 2: Extraction experiment of hydrochloric acid by DDCMP>
Since DDCMP has an amide group, it is considered that hydrochloric acid can be extracted. Therefore, an extraction experiment of hydrochloric acid by DDCMP was performed. All extraction experiments were performed by the batch method. Each aqueous phase was adjusted to a predetermined hydrochloric acid concentration (hydrogen ion concentration: 0.1 to 8 mol dm ^-3 ; chloride ion concentration: 0.1 to 8 mol dm ^-3 ). In the organic phase, toluene was used as a diluent and the DDCMP concentration was adjusted to a predetermined concentration (0.005 or 0.01 mol dm ^-3 DDCMP concentration). Each phase was placed in an Erlenmeyer flask with a stopper and shaken in a thermostatic bath at 30 ° C. for 24 hours. Thereafter, the aqueous phase and the organic phase were separated, and the aqueous phase hydrochloric acid concentration after equilibration was determined by neutralization titration using an aqueous sodium hydroxide solution. Further, the concentration of the organic phase hydrochloric acid after equilibration was determined by neutralization titration using potassium hydroxide / ethanol.

C _orgHCl / [RNN] ₀ was used to evaluate the extraction characteristics. The extraction results of hydrochloric acid by DDCMP are shown in FIG.

As shown in FIG. 2, when the DDCMP concentrations were 0.005 and 0.01 mol dm ⁻³ (5 mM and 10 mM), the values of C _orgHCl / [RNN] ₀ were almost the same. Since the value seems to have converged to about 2, it is considered that 2 molecules of hydrochloric acid are extracted with 1 molecule of the extractant.

<Example 3: Extraction experiment of metal ion by DDCMP>
All extraction experiments were performed by the batch method. The aqueous phase is about 1 × 10 ^-3 mol dm ^-3 gold (III), palladium (II), platinum (II), rhodium (II), copper (II), manganese (II), nickel (II), Contains chloride salts of cadmium (II), zinc (II), cobalt (II), iron (II), indium (III), gallium (III), samarium (III), europium (III) and yttrium (III) A hydrochloric acid aqueous solution (hydrochloric acid concentration: 0.1 to 8 (0.1, 0.2, 0.3, etc.) mol dm ^-3 ) was used, and a toluene solution containing 0.01 mol dm ^-3 DDCMP was used as the organic phase. 10 ml of each phase was dispensed into an Erlenmeyer flask with a stopper and shaken in a thermostatic bath at 30 ° C. for 24 hours. Thereafter, the aqueous phase was fractionated, and the initial metal concentration and the metal concentration in the aqueous phase after equilibration were measured using an atomic absorption photometer (PERKIN ELMER Aanalyst 100). Moreover, the metal concentration in the organic phase was determined from the mass balance. The pH after equilibration was measured using a pH meter (Toa Denpa Kogyo HM-30S), and the hydrochloric acid concentration after equilibration was determined by neutralization titration.

  In order to evaluate the extraction characteristics of metal ions, the extraction rate E and the distribution ratio D were defined as follows. Figure 3 shows the effect of equilibrium hydrochloric acid concentration on the extraction rate of various metal ions from hydrochloric acid solution by DDCMP.

As shown in FIG. 3, indium (III), rhodium (III), copper (II), nickel (II), iron (II), manganese (II) and cobalt (II) are almost extracted in the total hydrochloric acid region. There wasn't. Gold (III) and platinum (IV) had almost no influence of hydrochloric acid concentration, and showed a high extraction rate of 100% in the entire hydrochloric acid region. Palladium (II) showed a high extraction rate of about 100% near the low hydrochloric acid concentration, but the extraction rate rapidly decreased as the hydrochloric acid concentration increased, and gradually decreased thereafter. Gallium (III) is hardly extracted at low hydrochloric acid concentration, but shows a high extraction rate of about 100% when the hydrochloric acid concentration is around 5 mol dm ^-3 . From these results, separation of noble metal and rhodium (III), separation of indium (III) and gallium (III) at high hydrochloric acid concentration, cadmium (II), zinc (II), nickel (II) at each hydrochloric acid concentration It is thought that separation of manganese (II) and cobalt (II) is possible. Rare earth was hardly extracted.

<Example 4: Measurement of extraction equilibrium arrival time of cadmium (II) by DDCMP>
In order to determine the time to reach extraction equilibrium of cadmium (II), an aqueous hydrochloric acid solution (hydrochloric acid concentration: 0.3 mol dm ^-3 ) containing about 0.1 x 10 ^-3 mol dm ^-3 cadmium (II) chloride was used as the aqueous phase. The toluene solution containing DDCMP of mol dm ^-3 was used as an organic phase, and the change over time of the extraction rate was measured. Fig. 4 shows the time to reach extraction equilibrium of cadmium (II) by DDCMP.
As shown in FIG. 4, equilibrium was reached in about 30 minutes.

<Example 5: Effect of equilibrium hydrochloric acid concentration on distribution ratio of cadmium ions by DDCMP>
Since DDCMP showed high selectivity for cadmium (II), the cadmium (II) extraction equilibrium from hydrochloric acid solution, which is industrially important, was studied in detail. The aqueous phase is an aqueous hydrochloric acid solution (hydrochloric acid concentration: 0.1-5 mol dm ^-3 ) containing about 0.1 x 10 ^-3 mol dm ^-3 cadmium (II) chloride, and the organic phase is 0.01 mol dm ^-3 DDCMP. Each toluene solution contained was used. The hydrochloric acid concentration after equilibration was determined by neutralization titration. Fig. 5 shows the effect of equilibrium hydrochloric acid concentration on the distribution ratio of cadmium (II) by DDCMP.

As shown in FIG. 5, as the hydrochloric acid concentration increased, the distribution ratio showed a second order dependency and increased.
Therefore, in order to clarify whether this influence is caused by chloride ions or hydrogen ions, the influence of hydrogen ions and chloride ions on the distribution ratio was investigated below.

<Example 6: Effect of hydrogen ion concentration on the distribution ratio of cadmium (II) by DDCMP>
The effect of hydrogen ion concentration on the distribution ratio when chloride ion concentration was kept constant was investigated. The aqueous phase contains various hydrogen ion concentration aqueous solutions containing about 0.1 × 10 ⁻³ mol dm ⁻³ of cadmium (II) chloride (hydrogen ion concentration: 0.01 to 0.3 mol dm ⁻³ ; chloride ion concentration: 0.3 mol dm ⁻³ ), And the toluene solution containing 0.01 mol dm ^-3 DDCMP was used as the organic phase. The aqueous phase was prepared by mixing 1 mol dm ^-3 hydrochloric acid and lithium chloride. The hydrogen ion concentration after equilibration was measured using neutralization titration. Figure 6 shows the effect of hydrogen ion concentration on the distribution ratio of cadmium (II) by DDCMP.

  As shown in FIG. 6, as the hydrogen ion concentration increased, the distribution ratio showed a secondary dependence and increased.

<Example 7: Effect of chloride ion concentration on distribution ratio of cadmium (II) by DDCMP>
The effect of chloride ion concentration on the distribution ratio when the hydrogen ion concentration was kept constant was investigated. The aqueous phase is about 0.1 × 10 ^-3 mol dm ^-3 of various chloride ion concentration aqueous solution containing cadmium chloride (II) (chloride ion concentration: 0.01~3 mol dm ^-3; hydrogen ion concentration: 0.1 mol dm ^{- 3} ) For the organic phase, a toluene solution containing 0.01 mol dm ^-3 DDCMP was used. The aqueous phase was adjusted to a chloride ion concentration by adding 0.1 mol dm ^-3 hydrochloric acid to a predetermined hydrogen ion concentration and adding lithium chloride thereto. Fig. 7 shows the effect of chloride ion concentration on the distribution ratio of cadmium (II) by DDCMP.

  As shown in FIG. 7, the distribution ratio increased with increasing chloride ion concentration, showing a second-order dependence.

<Example 8: Effect of extractant concentration on distribution ratio of cadmium (II) by DDCMP>
The effect of extractant concentration on the distribution ratio of cadmium (II) was investigated. The aqueous phase is an aqueous hydrochloric acid solution (hydrochloric acid concentration: 0.1 and 1 mol dm ^-3 ) containing about 0.1 × 10 ^-3 mol dm ^-3 cadmium (II) chloride, and the organic phase is 0.001 to 0.01 mol dm ^-3 Each toluene solution containing DDCMP was used. The effect of extractant concentration on the distribution ratio of cadmium (II) by DDCMP is shown in FIG.

As shown in FIG. 8, since the slope is 2, it is considered that two molecules of the extractant are involved in one molecule of cadmium (II). In this case, the estimated structure of the complex of DDCMP and CdCl ₂ is shown in FIG.

<Example 9: Measurement of extraction equilibrium arrival time of zinc (II) by DDCMP>
In order to determine the time to reach the extraction equilibrium of zinc (II), an aqueous hydrochloric acid solution (hydrochloric acid concentration: 0.3 mol dm ^-3 ) containing about 0.1 x 10 ^-3 mol dm ^-3 zinc chloride (II) was used as the aqueous phase. The toluene solution containing DDCMP of mol dm ^-3 was used as an organic phase, and the change over time of the extraction rate was measured. The time for reaching the extraction equilibrium of zinc (II) by DDCMP is shown in FIG.
As shown in FIG. 10, equilibrium was reached in about 30 minutes.

<Example 10: Effect of equilibrium hydrochloric acid concentration on the distribution ratio of zinc ions by DDCMP>
Since DDCMP showed high selectivity for zinc (II), the zinc (II) extraction equilibrium from hydrochloric acid solution, which is industrially important, was studied in detail. The aqueous phase is an aqueous hydrochloric acid solution containing about 1 x 10 ^-3 mol dm ^-3 zinc (II) chloride (hydrochloric acid concentration: 0.1 to 5 mol dm ^-3 ), and the organic phase is 0.01 mol dm ^-3 DDCMP. Each toluene solution contained was used. The hydrochloric acid concentration after equilibration was determined by neutralization titration. FIG. 11 shows the effect of equilibrium hydrochloric acid concentration on the distribution ratio of zinc (II) by DDCMP.

As shown in FIG. 11, as the hydrochloric acid concentration increased, the distribution ratio showed a secondary dependence and increased.
Therefore, in order to clarify whether this influence is caused by chloride ions or hydrogen ions, the influence of hydrogen ions and chloride ions on the distribution ratio was investigated below.

<Example 11: Effect of hydrogen ion concentration on zinc (II) distribution ratio by DDCMP>
The effect of hydrogen ion concentration on the distribution ratio when chloride ion concentration was kept constant was investigated. The aqueous phase contains various hydrogen ion concentration aqueous solutions containing about 0.1 × 10 ^-3 mol dm ^-3 zinc (II) (hydrogen ion concentration: 0.01 to 0.3 mol dm ^-3 ; chloride ion concentration: 1 mol dm ^-3 ) The organic phase was a toluene solution containing 0.01 mol dm ^-3 DDCMP. The aqueous phase was prepared by mixing 1 mol dm ^-3 hydrochloric acid and lithium chloride. The hydrogen ion concentration after equilibration was measured using neutralization titration. FIG. 12 shows the influence of hydrogen ion concentration on the distribution ratio of zinc (II) by DDCMP.
As shown in FIG. 12, the distribution ratio did not depend on the hydrogen ion concentration.

<Example 12: Effect of chloride ion concentration on the distribution ratio of zinc (II) by DDCMP>
The effect of chloride ion concentration on the distribution ratio when the hydrogen ion concentration was kept constant was investigated. The aqueous phase is about 0.1 × 10 ^-3 mol dm ^-3 of various chloride ion concentration aqueous solution containing zinc chloride (II) (chloride ion concentration: 0.01~3 mol dm ^-3; hydrogen ion concentration: 0.1 mol dm ^{- 3} ) For the organic phase, a toluene solution containing 0.01 mol dm ^-3 DDCMP was used. The aqueous phase was adjusted to a chloride ion concentration by adding 0.1 mol dm ^-3 hydrochloric acid to a predetermined hydrogen ion concentration and adding lithium chloride thereto. FIG. 13 shows the effect of chloride ion concentration on the distribution ratio of zinc (II) by DDCMP.

  As shown in FIG. 13, as the chloride ion concentration increased, the distribution ratio showed a second order dependence and increased.

<Example 13: Effect of extractant concentration on zinc (II) distribution ratio by DDCMP>
The effect of extractant concentration on the distribution ratio of zinc (II) was investigated. The aqueous phase is an aqueous hydrochloric acid solution containing about 0.1 × 10 ^-3 mol dm ^-3 zinc (II) chloride (hydrochloric acid concentration: 0.1 and 1 mol dm ^-3 ), and the organic phase is 0.001 to 0.01 mol dm ^-3 . Each toluene solution containing DDCMP was used. FIG. 14 shows the effect of extractant concentration on the partition ratio of zinc (II) by DDCMP.

As shown in FIG. 14, since the slope is 1, it is considered that one molecule of the extractant is involved in one molecule of zinc (II).
In this case, the estimated structure of the complex of DDCMP and ZnCl ₂ is shown in FIG.

<Example 14: Back extraction experiment of cadmium (II) and zinc (II)>
All extraction experiments were performed by the batch method. The aqueous phase is an aqueous hydrochloric acid solution containing about 0.1 × 10 ^-3 mol dm ^-3 cadmium (II) chloride (hydrochloric acid concentration: 3 mol dm ^-3 ) or about 0.1 × 10 ^-3 mol dm ^-3 zinc chloride (II ) Containing a hydrochloric acid aqueous solution (hydrochloric acid concentration: 3 mol dm ^-3 ), and the organic phase was a toluene solution containing 0.01 mol dm ^-3 DDCMP. 100 ml of each phase was dispensed into an Erlenmeyer flask with a stopper and shaken in a thermostatic bath at 30 ° C. for about 24 hours.

  Then, each of the aqueous phase and the organic phase was separated, and 10 ml of the separated organic phase and 10 ml of an aqueous phase (desorbed aqueous solution) containing a predetermined concentration of back extractant were placed in an Erlenmeyer flask with a stopper. Then, it was shaken again in a constant temperature bath at 30 ° C. for 24 hours. The initial metal ion concentration and the water phase metal ion concentration after equilibration were measured using an atomic absorption photometer. Further, the metal ion concentration in the organic phase was determined from the mass balance.

  Table 1 shows the back extraction rates of cadmium (II) and zinc (II) with various back extractants when using an organic phase containing DDCMP. The back extraction rate (%) means the ratio of each back extracted metal ion to the total amount of cadmium (II) or zinc (II) extracted into the organic phase in the extraction step.

  As shown in Table 1, regardless of which back extractant (desorbed aqueous solution) was used, the back extraction rate of cadmium (II) and zinc (II) was almost 100%. This suggests that chloride ions are required for extraction of cadmium (II) and zinc (II). Therefore, it was suggested that cadmium (II) and zinc (II) extracted in the organic phase containing DDCMP can be recovered and concentrated almost 100% by using these back extractants.

  The extractant of the present invention is a noble metal ion selected from the group consisting of gold (III), palladium (II) and platinum (IV), or a base selected from the group consisting of cadmium (II) and zinc (II) Metal ions can be selectively extracted. As a result, gold (III), palladium (II) or platinum (IV) is obtained from noble metal acidic waste liquid such as electronic equipment waste or waste catalyst, and cadmium (II) or zinc (from zinc or nicad battery waste solution). II) can be selectively recovered.

Claims (3)

Formula I:

[Where:
R ^1, R ^2, R ³ and R ⁴ are 2-ethyl - Ri hexan-1-yl der;
L ¹ and L ² are methylene ]
A compound represented by An extractant for at least one metal ion selected from the group consisting of gold, palladium, platinum, cadmium and zinc, comprising the compound of claim 1 . Gold, palladium, platinum, by contacting the organic phase containing at least one water phase containing metal ions compound of claim 1 selected from the group consisting of cadmium and zinc, organic said metal ion A method for recovering the metal ion, comprising an extraction step of extracting the phase.

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