JP5818315B2 - Metal selective extractant - Google Patents

Description

  The present invention relates to a metal extractant containing a compound that selectively adsorbs metal, and a metal recovery method using the compound.

  Despite being a rare metal-consuming country that consumes about 20% of the world's rare metals, Japan relies on imports for most of its major resources. Therefore, ensuring a stable supply of rare metals is a difficult task. Among rare metals, platinum group metals such as ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt) have low production from natural minerals. Therefore, it is not only separated and recovered as a by-product discharged with the refining of base metals such as copper (Cu), cobalt (Co) and nickel (Ni), but also waste of electronic equipment, and It is also separated and recovered from waste catalysts such as waste liquid from aldehyde production by oxo reaction and exhaust gas catalyst for automobiles.

  Examples of the method for recovering the platinum group metal include a solvent extraction method, a precipitation separation method, and an ion exchange method. Among these, the solvent extraction method is widely used from the viewpoint of economy and operability.

  Patent Document 1 describes an extractant for Rh, which is biphenylalkylpyridine. According to this document, only the Rh can be selectively separated with high efficiency from the Rh-containing solution by the above extractant.

  In Patent Document 2, a solution containing phosphite and Rh is treated with an oxidizing agent in the presence of a polar solution containing carboxylic acid and a specific phosphonate, and then into a polar solvent phase and a more nonpolar organic solvent phase. A method for recovering Rh, characterized by phase separation and recovery of Rh in a polar solvent, is described. According to this document, Rh can be efficiently separated from a solution containing phosphite and Rh, such as a catalyst solution after the reaction of oxo reaction (hydroformylation reaction).

  Patent Document 3 describes a method of mutually separating platinum group metals from platinum group metal-containing materials containing impurity metals. According to this document, the platinum group metal is highly purified by recovering Pd, Pt, Ru, Ir, and Rh in a stepwise manner from a platinum group metal-containing material containing an impurity metal using a specific extractant. Can be separated from each other.

  Patent Document 4 describes a palladium extractant consisting of sulfur-containing diamide compounds such as thioglycolamide compounds, 3,3'-thiodipropionamide compounds and 3,6-dithiaoctanediamide compounds. According to this document, Pd can be extracted in a short time by using a sulfur-containing diamide compound as compared with a conventional extractant such as dihexyl sulfide (DHS).

  Patent Document 5 describes a platinum group metal separation reagent containing an amide-containing tertiary amine compound such as Nn-hexyl-bis (N-methyl-Nn-octylethylamido) amine as an active ingredient. According to this document, by using an amide-containing tertiary amine compound as described above as a separation reagent, Rh, Pt and Pd are extracted from an acidic treated solution containing a platinum group metal consisting of Rh, Pt and Pd. can do. Further, Rh can be selectively recovered by bringing the separation reagent-containing solution after metal extraction into contact with a high-concentration hydrochloric acid solution, and the separation reagent-containing solution after Rh separation is brought into contact with a high-concentration nitric acid solution. Thus, Pt and Pd can be recovered.

JP-A-5-295458 JP 2000-325802 JP JP 2005-97695 A International Publication No. 2005/083131 Pamphlet International Publication No. 2009/001897 Pamphlet

As described above, various techniques have been developed as a method for recovering a platinum group metal by a solvent extraction method, but no method for efficiently separating and recovering the platinum group metal has yet been provided. Usually, since the waste liquid and the waste catalyst treatment liquid discharged with the refining of the base metal are acidic aqueous solutions of hydrochloric acid, metal ions can form chloride ions and chloro complexes. For example, Rh ions are present in the form of complexes such as [RhCl ₅ ] ⁻ , [RhCl ₅ (H ₂ O)] ²⁻ or [RhCl ₆ ] ³⁻ . Such chloro complexes of Rh ions are less likely to be extracted or adsorbed than base metal and other platinum group metal ions and complexes. Therefore, Rh ions are exclusively recovered from the residual liquid after the step of extracting or adsorbing ions of the base metal and other white metal metals. However, in such a method, it is difficult to selectively extract Rh ions, and thus it is difficult to improve Rh purity. Further, if the recovery rate of other platinum group metals is improved in the preceding step, the recovery rate of Rh obtained from the remaining liquid in the final step will be reduced as a result.

  Therefore, an object of the present invention is to provide means for selectively extracting Rh or Pd ions from a solution containing base metal ions and platinum group metal ions.

  As a result of various studies on means for solving the above-mentioned problems, the present inventor has found that the above object can be achieved by using an imidazole derivative in which a fat-soluble substituent is introduced into imidazole, and has completed the present invention.

［式中、
R¹及びR²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_1-18アルキル、C_2-18アルケニル若しくはC_2-18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及びR²は同一であることはない）；
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_1-4アルキル、C_2-4アルケニル若しくはC_2-4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るか、又は
R³及びR⁴は、それらが結合するイミダゾール環上の炭素原子と一緒になってイミダゾール環と縮合するシクロアルキル若しくはアリール（前記イミダゾール環と縮合するシクロアルキル若しくはアリールは、非置換であるか、或いは1個若しくは複数個のハロゲンによって置換されている）を形成する］
で表される化合物を含有する、金属イオンの抽出剤。
（2） 金属イオンがロジウム及びパラジウムからなる群より選択される白金族金属のイオンである、前記（1）の抽出剤。
（3） 金属イオンを含有する水相を、式I:

［式中、
R¹及びR²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_1-18アルキル、C_2-18アルケニル若しくはC_2-18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及びR²は同一であることはない）；
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_1-4アルキル、C_2-4アルケニル若しくはC_2-4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るか、又は
R³及びR⁴は、それらが結合するイミダゾール環上の炭素原子と一緒になってイミダゾール環と縮合するシクロアルキル若しくはアリール（前記イミダゾール環と縮合するシクロアルキル若しくはアリールは、非置換であるか、或いは1個若しくは複数個のハロゲンによって置換されている）を形成する］
で表される化合物を含有する有機相に接触させて、金属イオンを該有機相に抽出する抽出工程を含む、金属イオンの回収方法。
（4） 金属イオンがロジウム及びパラジウムからなる群より選択される白金族金属のイオンである、前記（3）の方法。 That is, the gist of the present invention is as follows.
(1) The following formula I:

[Where:
R ¹ and R ² are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-18 alkyl, C _2-18 alkenyl or C _2-18 alkynyl, or substituted or unsubstituted straight Chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that
R ¹ and R ² are not identical);
R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4 alkynyl, or substituted or unsubstituted straight A chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl, or
R ³ and R ⁴ are cycloalkyl or aryl fused to the imidazole ring together with the carbon atom on the imidazole ring to which they are attached (the cycloalkyl or aryl fused to the imidazole ring is unsubstituted, Or is substituted by one or more halogens]
A metal ion extractant containing a compound represented by:
(2) The extractant according to (1), wherein the metal ion is a platinum group metal ion selected from the group consisting of rhodium and palladium.
(3) A water phase containing metal ions is represented by the formula I:

[Where:
R ¹ and R ² are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-18 alkyl, C _2-18 alkenyl or C _2-18 alkynyl, or substituted or unsubstituted straight Chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that R ¹ and R ² are not the same);
R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4 alkynyl, or substituted or unsubstituted straight A chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl, or
R ³ and R ⁴ are cycloalkyl or aryl fused to the imidazole ring together with the carbon atom on the imidazole ring to which they are attached (the cycloalkyl or aryl fused to the imidazole ring is unsubstituted, Or is substituted by one or more halogens]
A method for recovering metal ions, comprising an extraction step in which a metal ion is extracted into the organic phase by contacting with an organic phase containing a compound represented by the formula:
(4) The method according to (3) above, wherein the metal ion is a platinum group metal ion selected from the group consisting of rhodium and palladium.

  According to the present invention, it is possible to provide means for selectively extracting Rh or Pd ions from a solution containing base metal ions and platinum group metal ions.

It is process drawing which shows one Embodiment of the collection | recovery method of the metal ion of this invention. It is a figure which shows the result of having used chloroform for the diluent in the organic phase containing the compound of Examples 1-5. In the organic phase containing the compound of Examples 1-5, it is a figure which shows the result of using the toluene solution containing 10 volume% 2-ethylhexyl alcohol for a diluent. FIG. 4 is a graph showing the relationship between the distribution ratio of Rh (III) ions and the equilibrium hydrochloric acid concentration when an organic phase containing the compound of Example 4 is used. 6 is a graph showing the relationship between the distribution ratio of Rh (III) ions and the equilibrium hydrogen ion concentration when an organic phase containing the compound of Example 4 is used. FIG. FIG. 6 is a graph showing the relationship between the distribution ratio of Rh (III) ions and the equilibrium chloride ion concentration when an organic phase containing the compound of Example 4 is used. A: When initial hydrogen ion concentration is 1.0 M; B: When initial hydrogen ion concentration is 3.0 M. FIG. 6 is a graph showing the relationship between the distribution ratio of Rh (III) ions and the initial compound concentration when an organic phase containing the compound of Example 4 is used. It is a figure which shows the relationship between the experimental result performed in the usage examples 2-5, and the calculated value calculated from Formula (8). A: Relationship between Rh (III) ion distribution ratio and equilibrium hydrochloric acid concentration; B: Relationship between Rh (III) ion distribution ratio and equilibrium hydrogen ion concentration; C: Rh (III) ion distribution ratio and equilibrium chloride concentration Relationship between the concentration of the product ions; D: Relationship between the distribution ratio of Rh (III) ions and the concentration of the initial compound. FIG. 4 is a diagram showing a putative structure of a complex of the compound (UDIM) of Example 4 and Rh (III).

で表される化合物を含有する金属の抽出剤に関する。 Hereinafter, preferred embodiments of the present invention will be described in detail.
<1. Imidazole derivatives>
The present invention provides compounds of formula I:

It is related with the extractant of the metal containing the compound represented by these.

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, n -Decyl, n-undecyl, n-dodecyl and the like.

  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, 1-decenyl and oleyl (( Z) -octadeca-9-enyl) 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, 1-decynyl and the like.

  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 inventor is able to selectively extract rhodium (Rh) or palladium (Pd) ions from a solution containing base metal ions and platinum group metal ions by using an imidazole derivative represented by the formula I. I found it. The present invention therefore relates to a metal extractant containing a compound of the formula I.

In the compound of formula I, R ¹ and R ² are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-18 alkyl, C _2-18 alkenyl or C _2-18. Alkynyl, or substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (wherein R ¹ and R ² are not necessarily the same) is preferable.

In the compound of formula I, R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4. Alkynyl, or substituted or unsubstituted linear or branched C _7-18 arylalkyl or C _8-18 arylalkenyl is preferred.

Alternatively, R ³ and R ⁴ are cycloalkyl or aryl fused with the imidazole ring together with the carbon atom on the imidazole ring to which they are attached (the cycloalkyl or aryl fused with the imidazole ring is unsubstituted) Or substituted by one or more halogens, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4 alkynyl). preferable.

Preferably, the compound of formula I is such that R ¹ and R ² independently of one another are hydrogen, unsubstituted linear C _9-18 alkyl or unsubstituted linear C _2-18 alkenyl. Yes (but R ¹ and R ² are not the same);
R ³ and R ⁴ , independently of each other, are hydrogen or methyl, or together with the carbon atom on the imidazole ring to which they are attached form an unsubstituted phenyl that is fused with the imidazole ring.

More preferably, the compound of formula I is such that R ¹ and R ² independently of one another are hydrogen, unsubstituted linear C _9-12 alkyl or unsubstituted linear C _17-18 alkenyl. Where R ¹ and R ² are not the same;
R ³ and R ⁴ , independently of each other, are hydrogen or methyl, or together with the carbon atom on the imidazole ring to which they are attached form an unsubstituted phenyl that is fused with the imidazole ring.

Particularly preferably, the compound of the formula I is:
1-dodecylimidazole (DIM);
4-methyl-1-dodecylimidazole (MDIM);
1-oleylimidazole (OLIM);
Undecylimidazole (UDIM); and nonylbenzimidazole (NBIM);
Selected from the group of compounds consisting of

  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 salts 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 or benzoic acid. Salts with inorganic or organic acids are preferred.

  By using the compound represented by the formula I in the form as described above, it is possible to selectively extract Rh or Pd ions from a solution containing base metal ions and platinum group metal ions.

  As the compound represented by the formula I of the present invention, a commercially available product may be used as it is, and for example, in the technical field such as nucleophilic substitution reaction between imidazole and alkyl halide, halogenated alkenyl or halogenated alkynyl. You may manufacture using a well-known synthetic reaction.

［式中、R³及びR⁴は、式Iと同様の意味を表す］
で表されるイミダゾールと、式III：
R¹-X III
［式中、R¹は、式Iと同様の意味を表し、Xはハロゲンである］
で表されるハロゲン化アルキル、ハロゲン化アルケニル若しくはハロゲン化アルキニルとを、塩基存在下、非プロトン性極性溶媒中で反応させる置換工程；
を含む方法によって製造することができる。
上記の反応により、式Iで表される化合物を製造することが可能となる。 For example, the compound represented by the formula I [wherein R ^{1 to} R ⁴ represent the same meaning as described above] is represented by the formula II:

[Wherein R ³ and R ⁴ represent the same meaning as in formula I]
An imidazole represented by formula III:
R ¹ -X III
[Wherein R ¹ represents the same meaning as in formula I, and X is halogen]
A substitution step in which an alkyl halide, an alkenyl halide, or an alkynyl halide represented by the above is reacted in an aprotic polar solvent in the presence of a base;
It can manufacture by the method containing.
The above reaction makes it possible to produce the compound represented by the formula I.

<2. Metal extractant>
In the present specification, the “base metal” means a metal that is not included in the noble metal among non-ferrous metals, specifically, aluminum (Al), copper (Cu), zinc (Al), and lead (Pb). And rare metals such as titanium (Ti), nickel (Ni) and tungsten (W).

  In this specification, “platinum group metal” means ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt) and gold (Au). Among the noble metals consisting of), Ru, Rh, Pd, Os, Ir and Pt having properties similar to Pt are meant.

  The metal extractant of the present invention includes one or more base metal ions selected from the group consisting of Al, Cu, Al, Pb, Ti, Ni and W, Ru, Rh, Pd, Os, Ir and Pt. It can be used to selectively extract platinum group metal ions selected from the group consisting of Rh and Pd from a solution containing one or more types of platinum group metal ions selected from the group. It is preferably used to selectively extract Rh ions.

  The metal extractant of the present invention may contain only the compound represented by Formula I, and in addition to the compound, a diluent containing one or more organic solvents and / or one or more additives May further be 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 or chloroform is preferred. Examples of the additive include, but are not limited to, 2-ethylhexyl alcohol, octanol, decanol, and nonylphenol. 2-ethylhexyl alcohol is preferred. The concentration of the additive is preferably in the range of 5 to 20% by mass with respect to the total mass of the metal extractant. Particularly preferably, the diluent contained in the metal extractant of the present invention is chloroform or toluene containing 2-ethylhexyl alcohol in a range of 10 to 20% by mass relative to the total mass of the metal extractant. is there.

  By containing the above components, the metal extractant of the present invention can selectively extract Rh or Pd ions from a solution containing base metal ions and platinum group metal ions. .

<3. Metal ion recovery method>
Usually, in an acidic aqueous solution of metal ions, the metal ions form an anionic complex ion with an acid conjugate base. Thus, metal ions can form an equilibrium consisting of metal ions and some form of complex ions, depending on the acid concentration and pH.

  The compound represented by the formula I of the present invention has an amino group capable of forming a complex with an anion. The inventor appropriately adjusts the acid concentration and / or pH of an aqueous solution containing base metal ions and platinum group metal ions, and converts the aqueous phase comprising the aqueous solution to a compound represented by formula I of the present invention. It was found that Rh or Pd ions can be selectively extracted into the organic phase by contacting with an organic phase containing. 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. Includes 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 ions are preferably platinum group metal ions selected from the group consisting of Rh and Pd ions, and more preferably Rh ions. The platinum group metal ion preferably has a concentration of 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ M, more preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻² M in the aqueous phase. preferable.

The aqueous phase used in this step is not limited to the platinum group metal ions selected from the group consisting of Rh and Pd ions, but also other metals consisting of the base metal ions and other platinum group metal ions described above. Ions may be contained. In this case, the other metal ions are each independently preferably at a concentration of 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ M, and a concentration of 1 × 10 ⁻⁴ to 1 × 10 ⁻² M. It is more preferable. Examples of such an aqueous phase include wastes of electronic equipment, and acidic waste liquids such as waste liquids of aldehyde production by oxo reaction and exhaust gas catalysts of automobiles. Even if the aqueous phase used in this step contains other metal ions, Rh or Pd ions can be selectively extracted by the method of the present invention.

Metal ions in the aqueous phase usually exist in the equilibrium state of a salt or complex ion of the acid with a conjugate base. For example, when the aqueous phase containing Rh ions is an aqueous hydrochloric acid solution, the Rh ions are in the form of complexes such as [RhCl ₅ ] ⁻ , [RhCl ₅ (H ₂ O)] ²⁻ or [RhCl ₆ ] ^3−. Exists. Here, when an aqueous phase containing a metal ion in the form of the above complex is brought into contact with an organic phase containing a compound represented by formula I, a complex anion in which the amino group of the compound represented by formula I is Rh To form a new complex. Since 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, Rh ions can be extracted into the organic phase.

  As described above, since the metal ions in the aqueous phase exist in an equilibrium state of salt or complex ions, the equilibrium state may change depending on the acid concentration and / or pH of the aqueous phase. Therefore, by appropriately adjusting the acid concentration and / or pH of the aqueous phase, desired metal ions can be selectively extracted from an aqueous solution containing base metal ions and platinum group metal ions.

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.

Examples of the acid used for adjusting the pH include the acids described above. In addition, examples of the base used for adjusting the pH include, but are not limited to, NaOH, KOH, LiOH, and NH ₃ .

More specifically, the aqueous phase used in this step preferably contains 1 × 10 ⁻² to 10 M acid. In this case, the acid used is preferably hydrochloric acid or nitric acid. Or it is preferable to adjust pH to the range of -1 to 0.5. In this case, it is preferable to adjust the pH with hydrochloric 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 0.05 to 1M.

  When the organic phase is in the form of a solid phase, it can be used as it is in the aqueous phase as long as the compound represented by Formula I is in a solid form at room temperature. 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, polyacrylate resin, activated carbon, hydrophobic zeolite, silica, and polyvinyl chloride resin. Polystyrene resin, 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 is phase-separated from an aqueous phase, and then contacted with a desorption aqueous solution to desorb (back extract) metal ions from the organic phase into the desorption aqueous solution. A separation step (step S2) may be included.

  The aqueous desorption solution used in this step is not limited, but for example, one or more acidic aqueous solutions selected from the group consisting of hydrochloric acid, nitric acid and sulfuric acid, ammonia, sodium hydroxide and potassium hydroxide. One or more alkaline aqueous solutions selected from the group consisting of thiourea and ammonium thiocyanate, and mixtures thereof (for example, a mixture of thiourea and hydrochloric acid) can be mentioned. A single component aqueous solution comprising hydrochloric acid, nitric acid, sulfuric acid or aqueous ammonia is preferred. In the case of hydrochloric acid, the concentration is preferably 1 to 8 M. In the case of nitric acid, the concentration is preferably 1 to 8 M. In the case of ammonia water, the concentration is preferably 1 to 5 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 performing the method of the present invention, Rh or Pd ions can be selectively extracted from a solution containing base metal and platinum group metal ions.

  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: 1-dodecylimidazole (DIM)

34.04 g (0.50 mol) of imidazole was placed in a 1000 cm ³ three-necked flask and dissolved in 500 cm ³ of 1,4-dioxane. After adding about 50.59 g (0.50 mol) of triethylamine to the mixture, 24.92 g (0.10 mol) of 1-bromododecane was slowly added to the stirred mixture using a dropping funnel over about 30 minutes at room temperature. It was dripped. After completion of the dropwise addition, the reaction mixture was refluxed at 80 ° C. for 48 hours using a mantle heater. The progress of the reaction was confirmed using thin layer chromatography (developing solvent ethanol: chloroform = 1: 5).

After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure, chloroform was added to the residue, and the remaining aqueous solution was phase-separated. The resulting chloroform solution, 3 times with 1.0 mol dm ^-3 HCl, and washed once with 1.0 aqueous sodium hydroxide mol dm ^-3, to remove unreacted imidazole and hydrochloric acid. Since sodium hydroxide remains in the resulting chloroform solution, the operation of adding phase separation by adding distilled water to the chloroform solution was repeated until the pH of the aqueous phase after phase separation reached about 7, Was removed. After dehydrating the chloroform solution using magnesium sulfate, the chloroform was distilled off under reduced pressure. Thereafter, the product was distilled, and the solvent was changed to hexane to remove impurities.

The final product was obtained as a tan liquid. Yield 85%. ¹ H-NMR and ¹³ C-NMR spectra of the product were measured, and the product was identified as the title compound from the results of the spectrum and TLC analysis.

  This compound (DIM) was insoluble in toluene but soluble in chloroform. Therefore, the following extraction experiment was performed using chloroform as a diluent.

Example 2: 1-dodecyl-4-methylimidazole (MDIM)

41.05 g (0.50 mol) of 4-methylimidazole was placed in a 1000 cm ³ three-necked flask and dissolved in 500 cm ³ of 1,4-dioxane. After adding about 50.59 g (0.50 mol) of triethylamine to the mixture, 24.92 g (0.10 mol) of 1-bromododecane was slowly added to the stirred mixture using a dropping funnel over about 30 minutes at room temperature. It was dripped. After completion of the dropwise addition, the reaction mixture was refluxed at 80 ° C. for 48 hours using a mantle heater. The progress of the reaction was confirmed using thin layer chromatography (developing solvent ethanol: chloroform = 1: 5).

After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure, chloroform was added to the residue, and the remaining aqueous solution was phase-separated. The resulting chloroform solution, 1.0 3 times with hydrochloric acid mol dm ^-3, 1.0 and washed once with aqueous sodium hydroxide mol dm ^-3, to remove the 4-methyl imidazole and hydrochloric acid unreacted. Since sodium hydroxide remains in the resulting chloroform solution, the operation of adding phase separation by adding distilled water to the chloroform solution was repeated until the pH of the aqueous phase after phase separation reached about 7, Was removed. After dehydrating the chloroform solution using magnesium sulfate, the chloroform was distilled off under reduced pressure. Thereafter, the product was distilled, and the solvent was changed to hexane to remove impurities.

The final product was obtained as a tan liquid. Yield 80%. ¹ H-NMR and ¹³ C-NMR spectra of the product were measured, and the product was identified as the title compound from the results of the spectrum and TLC analysis.

  This compound (MDIM) was insoluble in toluene but soluble in chloroform. Therefore, the following extraction experiment was performed using chloroform as a diluent.

Example 3: 1-oleylimidazole (OLIM)

34.04 g (0.50 mol) of imidazole was placed in a 1000 cm ³ three-necked flask and dissolved in 500 cm ³ of 1,4-dioxane. After about 50.59 g (0.50 mol) of triethylamine was added to the mixture, 28.69 g (0.10 mol) of oleyl chloride was slowly added dropwise to the stirred mixture over about 30 minutes at room temperature using a dropping funnel. . After completion of the dropwise addition, the reaction mixture was refluxed at 80 ° C. for 48 hours using a mantle heater. The progress of the reaction was confirmed using thin layer chromatography (developing solvent ethanol: chloroform = 1: 5).

After completion of the reaction, 1,4-dioxane was distilled off under reduced pressure, chloroform was added to the residue, and the remaining aqueous solution was phase-separated. The resulting chloroform solution, 3 times with 1.0 mol dm ^-3 HCl, and washed once with 1.0 aqueous sodium hydroxide mol dm ^-3, to remove unreacted imidazole and hydrochloric acid. Since sodium hydroxide remains in the resulting chloroform solution, the operation of adding phase separation by adding distilled water to the chloroform solution was repeated until the pH of the aqueous phase after phase separation reached about 7, Was removed. After dehydrating the chloroform solution using magnesium sulfate, the chloroform was distilled off under reduced pressure. Thereafter, the product was distilled, and the solvent was changed to hexane to remove impurities.

The final product was obtained as a tan liquid. Yield 85%. ¹ H-NMR and ¹³ C-NMR spectra of the product were measured, and the product was identified as the title compound from the results of the spectrum and TLC analysis.

  This compound (OLIM) was insoluble in toluene but soluble in chloroform. Therefore, the following extraction experiment was performed using chloroform as a diluent.

上記の化合物は、市販品（東京化成株式会社）をそのまま用いた。 Example 4: 2-Undecylimidazole (UDIM)

As the above compound, a commercially available product (Tokyo Chemical Industry Co., Ltd.) was used as it was.

上記の化合物は、市販品（東京化成株式会社）をそのまま用いた。 Example 5: 2-nonylbenzimidazole (NBIM)

As the above compound, a commercially available product (Tokyo Chemical Industry Co., Ltd.) was used as it was.

Use Case 1: Relationship between extraction rate and hydrochloric acid concentration
To 50 cm ³ Erlenmeyer flasks, aqueous phase (1 mmol dm ^-3 0.56 containing rhodium chloride, 1.0, 1.8, 3.2, 5.6 or 8.0 M aqueous hydrochloric acid) to 15 cm ^3, the organic phase (0.5 mol dm ^-3 Example Compound A chloroform solution containing 10% by volume or a toluene solution containing 10% by volume of 2-ethylhexyl alcohol) was added by 15 cm ³ , and the mixture was shaken at 30 ° C. for 24 hours using a thermostatic bath. Next, the aqueous phase was collected and the Rh ion concentration was measured using an atomic absorption photometer. FIG. 2 shows the results of using chloroform as a diluent, and FIG. 3 shows the results of using a toluene solution containing 10% by volume of 2-ethylhexyl alcohol as a diluent.

As shown in FIGS. 2 and 3, in any of the compounds, the extraction rate decreased as the hydrochloric acid concentration increased. Comparing the abundance of Rh (III) ions at the reduced chloride ion concentration, it is presumed that [RhCl ₅ (H ₂ O)] ⁻ was selectively extracted by the compounds of Examples 1 to 5.

  Comparing the difference in extraction rate with the diluent used for the same compound, a toluene solution containing 10% by volume of 2-ethylhexyl alcohol was used as the diluent and a case where chloroform was used as the diluent. Compared with the increase in hydrochloric acid concentration, the decrease in extraction rate was more prominent (Figs. 2 and 3). This result is assumed to be related to the difference in solubility of the compounds of Examples 1-5 in the diluent.

When an organic phase (chloroform solution) containing a 1-substituted imidazole type compound (Examples 1 to 3) was used, an extraction rate of about 80% was exhibited at a hydrochloric acid concentration in the range of 1.0 to 3.2 M (FIG. 2). . In addition, when the organic phase containing 0.1 mol dm ^-3 Example compound was used, the extraction rate was about 20%.

  When an organic phase containing the compound (DIM) of Example 1 (a toluene solution containing 10% by volume of 2-ethylhexyl alcohol) is used, Rh (III) ions are extracted most efficiently at a hydrochloric acid concentration of 3.2 M, The extraction rate gradually decreased with hydrochloric acid concentration exceeding that (Fig. 3). In contrast, when an organic phase containing the compound of Example 2 (MDIM) having a methyl group at the 4-position of the imidazole ring (a toluene solution containing 10% by volume of 2-ethylhexyl alcohol) was used, 1.8 M hydrochloric acid Rh (III) ions were extracted most efficiently at the concentration, but the extraction rate decreased sharply at hydrochloric acid concentrations exceeding that. In addition, when an organic phase containing the compound (OLIM) of Example 3 (a toluene solution containing 10% by volume of 2-ethylhexyl alcohol) is used, Rh (III) ions are extracted most efficiently at a hydrochloric acid concentration of 3.0 M. However, it was hardly extracted at a hydrochloric acid concentration of 8.0 M.

  From the above results, it is speculated that among the 1-substituted imidazole type compounds (Examples 1 to 3), the compound of Example 3 (OLIM) is the most preferred compound for the method of recovering Rh (III) ions. .

  When using an organic phase containing a 2-substituted imidazole-type or benzimidazole-type compound having a secondary amino group (Example 4 or 5), hydrochloric acid having the highest extraction rate at a hydrochloric acid concentration of 1.0 M and exceeding that The extraction rate gradually decreased with concentration (Figures 2 and 3). Compared with the case where the organic phase containing the compound (UDIM) of Example 4 was used, when the organic phase containing the compound (NBIM) of Example 5 was used, the overall extraction rate was low. It is surmised that the complex formation is inhibited by the steric hindrance of the benzene ring of the compound of Example 5 (NBIM).

Example 2: Relationship between distribution ratio and equilibrium hydrochloric acid concentration
To 50 cm ³ Erlenmeyer flasks, aqueous phase (1.0 containing 1 mmol dm ^-3 rhodium chloride, 1.8, 3.2, 5.6 or 8.0 M aqueous hydrochloric acid) to 15 cm ^3, the organic phase (the compound of 0.5 mol dm ^-3 Example 4 Of chloroform solution containing 15 cm ³ ) and shaken at 30 ° C. for 24 hours using a thermostatic bath. Next, the aqueous phase was collected and the Rh ion concentration was measured using an atomic absorption photometer. The aqueous phase at the time when the extraction equilibrium was reached was collected, and the hydrochloric acid concentration was quantified by neutralization titration.

  FIG. 4 shows the relationship between the distribution ratio of Rh (III) ions and the equilibrium hydrochloric acid concentration when the organic phase containing the compound of Example 4 was used.

  As shown in FIG. 4, it has been clarified that the distribution ratio of Rh (III) ions and the equilibrium hydrochloric acid concentration show a correlation of slope = -1.

Use Example 3: Relationship between Distribution Ratio and Equilibrium Hydrogen Ion Concentration The hydrogen ion concentration was changed within a predetermined range while keeping the chloride ion concentration constant with a hydrochloric acid and lithium chloride mixed aqueous solution. In a 50 cm ³ Erlenmeyer flask, add an aqueous phase (hydrochloric acid and lithium chloride mixed solution containing 1 mmol dm ^-3 rhodium chloride (hydrogen ion concentration: 1.0, 1.8, 3.2 or 6.0 M; chloride ion concentration: 6.0 M)) to 15 cm ³ , organic phase (0.5 mol dm ⁻³ chloroform solution containing the compound of Example 4) was added 15 cm ^{3 at a} time, and the mixture was shaken at 30 ° C. for 24 hours using a thermostatic bath. Next, the aqueous phase was collected and the Rh ion concentration was measured using an atomic absorption photometer. The aqueous phase at the time when extraction equilibrium was reached was collected, and the hydrogen ion concentration was quantified by neutralization titration.

  FIG. 5 shows the relationship between the distribution ratio of Rh (III) ions and the equilibrium hydrogen ion concentration when an organic phase containing the compound of Example 4 is used.

  As shown in FIG. 5, it has been clarified that the distribution ratio of Rh (III) ions and the equilibrium hydrogen ion concentration show a correlation having a maximum value of the distribution ratio at an equilibrium hydrogen ion concentration of about 1.0 M.

Use Example 4: Relationship between Distribution Ratio and Equilibrium Chloride Ion Concentration Chloride ion concentration was changed within a predetermined range while keeping the hydrogen ion concentration constant with a mixed aqueous solution of hydrochloric acid and lithium chloride. In a 50 cm ³ Erlenmeyer flask, water phase (hydrochloric acid and lithium chloride mixed solution containing 1 mmol dm ^-3 rhodium chloride (hydrogen ion concentration: 1.0 or 3.0 M; chloride ion concentration: 0.3, 1.0, 1.8 or 3.0 M)) 15 cm ³ , organic phase (0.1 mol dm ⁻³ chloroform solution containing the compound of Example 4) was added 15 cm ^{3 at a} time, and the mixture was shaken at 30 ° C. for 24 hours using a thermostatic bath. Next, the aqueous phase was collected and the Rh ion concentration was measured using an atomic absorption photometer. The aqueous phase at the time when the extraction equilibrium was reached was collected, and the hydrochloric acid concentration was quantified by neutralization titration.

  Of the relationship between the distribution ratio of Rh (III) ions and the equilibrium chloride ion concentration when using the organic phase containing the compound of Example 4, the initial hydrogen ion concentration is 1.0 M. The case where the ion concentration is 3.0 M is shown in FIG. 6B.

  As shown in FIG. 6A, it was revealed that when the initial hydrogen ion concentration was 1.0 M, the distribution ratio of Rh (III) ions and the equilibrium chloride ion concentration showed a correlation of slope = −0.5. Further, as shown in FIG. 6B, when the initial hydrogen ion concentration is 3.0 M, it is clear that the distribution ratio of Rh (III) ions and the equilibrium chloride ion concentration show a correlation of slope = −2. It was.

Use Example 5: Relationship between distribution ratio and initial extractant compound concentration
In a 50 cm ³ Erlenmeyer flask, 15 cm ^{3 of} aqueous phase (1.0 or 3.0 M aqueous hydrochloric acid solution containing 1 mmol dm ^-3 rhodium chloride), organic phase (0.1, 0.18, 0.32 or 0.56 mol dm ^-3 ) compound of Example 4 Of chloroform solution containing 15 cm ³ ) and shaken at 30 ° C. for 24 hours using a thermostatic bath. Next, the aqueous phase was collected and the Rh ion concentration was measured using an atomic absorption photometer.

  FIG. 7 shows the relationship between the Rh (III) ion distribution ratio and the initial compound concentration when an organic phase containing the compound of Example 4 was used.

  As shown in FIG. 7, it is clear that the Rh (III) ion distribution ratio and the initial compound concentration show a correlation of slope = 2 in both cases where the initial hydrogen ion concentration is 1.0 and 3.0 M. It was. From this result, the compound of Example 4 is presumed to have two molecules coordinated to one molecule of Rh (III) ion.

Use Example 6: Extraction Equilibrium of Rh (III) Ion Based on the above results, the extraction equilibrium of Rh (III) ion was assumed as follows. In view of the complex equilibrium of Rh (III) -chloride complexes at various hydrochloric acid concentrations, RhCl ^5- is mainly present in the hydrochloric acid concentration range of this example, and therefore the organic phase containing the compound of this example is When used, it was assumed that RhCl ⁵⁻ was selectively extracted.

  The equilibrium constants of the equilibrium equations of equations (1) and (2) can be expressed as follows:

であり、本実施例の反応系では、実施例4の化合物はRh (III)と比較して大過剰に存在しているので、近似的には、

である。 Stoichiometrically,

In the reaction system of this example, the compound of Example 4 is present in a large excess compared to Rh (III).

It is.

  Substituting equation (3) into the above equation yields the following equation:

  If the above equation (5) is substituted into the equation (4) and rearranged, the distribution ratio D can be expressed as follows.

Here, α ₅ can be expressed by Equation (7).

  From the above, the distribution ratio D can be expressed by the following equation (8).

In equation (8), from the chloride ion concentration dependence,
K ₁ = 1.09 × 10 ^-1 (mol / dm ³ ) ^-2 ;
K ₂ = 1.61 × 10 ³ (mol / dm ³ ) ²
Got. The total stability constant of Rh (III) is the following value.
β ₁ = 2.81 × 10 ² (mol / dm ³ ) ^-1 ;
β ₂ = 3.47 × 10 ⁴ (mol / dm ³ ) ^-2 ;
β ₃ = 8.32 × 10 ⁵ (mol / dm ³ ) ^-3 ;
β ₄ = 1.20 × 10 ⁷ (mol / dm ³ ) ^-4 ;
β ₅ = 5.62 × 10 ⁸ (mol / dm ³ ) ^-5 ;
β ₆ = 2.69 × 10 ⁸ (mol / dm ³ ) ^-6 ;

  FIGS. 8A to D show the relationship between the results of experiments performed in Use Examples 2 to 5 and the calculated values calculated from Equation (8).

  As shown in FIGS. 8A to 8D, it is calculated from the extraction result of Rh (III) ion and the formula (8) when using the organic phase containing the compound (UDIM) of Example 4 performed in Use Examples 2 to 5. The calculated values agreed well. Therefore, it has been clarified that the extraction reaction of Rh (III) ions by the compound (UDIM) of Example 4 is represented by the equilibrium formulas of formulas (1) and (2) assumed above. In this case, the estimated structure of the complex of the compound of Example 4 (UDIM) and Rh (III) is shown in FIG.

Example 7: Pre-extraction experiment for precious metal ions (1)
Into a 50 cm ³ Erlenmeyer flask, add 10 cm of the aqueous phase (3.0 M aqueous hydrochloric acid solution containing 1 mmol dm ^-3 rhodium chloride, tetrachloroauric (III) acid tetrahydrate and hexachloroplatinum (IV) acid hexahydrate). ^{3. An} organic phase (0.5 mol dm ⁻³ chloroform solution containing the compound of Example 1, 4 or 5) was added by 10 cm ³ , and shaken at 30 ° C. for 24 hours using a thermostatic bath. The aqueous phase was collected and the concentration of each noble metal ion was measured using an atomic absorption photometer.

Into a 50 cm ³ Erlenmeyer flask, add the above organic phase, add an aqueous phase (desorbed aqueous solution) containing a predetermined concentration of back extractant, and shake it at 30 ° C for 24 hours using a thermostatic bath. It was. The aqueous phase was collected and the concentration of each pre-extracted noble metal ion was measured using an atomic absorption photometer.

  Table 1 shows the back extraction rates of Rh (III) ions, Au (III) ions, and Pt (IV) ions by various back extractants when the organic phase containing each Example compound was used. The back extraction rate (%) means the ratio of each pre-extracted precious metal ion to the total amount of each precious metal ion extracted into the organic phase in the extraction step.

  When the organic phase containing the compound of Example 1 (DIM) was used, the back extraction rate with 36% by mass hydrochloric acid was not high, but the organic phase containing the compound of Example 4 (UDIM) or 5 (NBIM) was used. The back extraction rate was over 70%. From the above results, the compounds of Example 4 (UDIM) and 5 (NBIM) are acidic containing Pt (IV), Pd (II) and Rh (III) ions, like a waste catalyst of an automobile three-way catalyst. It was suggested that it can be used to selectively recover Rh (III) ions from the treatment solution.

Use Case 8: Back extraction experiment for precious metal ions (2)
In a 50 cm ³ Erlenmeyer flask, 10 cm ³ of an aqueous phase (3.0 M aqueous hydrochloric acid solution containing 1 mmol dm ^-3 rhodium chloride) and 10 vol% 2-phase containing the compound of Example 3 (0.5 mol dm ^-3 Example 3) 10 cm ³ of a toluene solution containing ethylhexyl alcohol) was added, and the mixture was shaken at 30 ° C. for 24 hours using a thermostatic bath. The aqueous phase was collected and the Rh (III) ion concentration was measured using an atomic absorption photometer.

Into a 50 cm ³ Erlenmeyer flask, add the above organic phase, add an aqueous phase (desorbed aqueous solution) containing a predetermined concentration of back extractant, and shake it at 30 ° C for 24 hours using a thermostatic bath. It was. The aqueous phase was collected, and the Rh (III) ion concentration back-extracted using an atomic absorption photometer was measured.
Table 2 shows the back extraction rate of Rh (III) ions by various back extractants.

When the organic phase containing the compound of Example 3 (OLIM) was used, both the 36% by mass hydrochloric acid and the 8 mol dm ^-3 hydrochloric acid aqueous solution showed a high back extraction rate.

Use Case 9: Back extraction experiment for precious metal ions (3)
In a 50 cm ³ Erlenmeyer flask, water phase (3.0 M aqueous hydrochloric acid solution containing 1 mmol dm ^-3 rhodium chloride, palladium chloride, tetrachloroauric (III) acid tetrahydrate and hexachloroplatinum (IV) acid hexahydrate) 10 cm ³ , organic phase (0.5 mol dm ^-3 toluene solution containing 10% by volume of 2-ethylhexyl alcohol containing the compound of Example 3) 10 cm ^{3 at a} time, and using a thermostatic bath at 30 ° C. for 24 hours Shake it. The aqueous phase was collected and the concentration of each noble metal ion was measured using an atomic absorption photometer.

Into a 50 cm ³ Erlenmeyer flask, add the above organic phase, add an aqueous phase (desorbed aqueous solution) containing a predetermined concentration of back extractant, and shake it at 30 ° C for 24 hours using a thermostatic bath. It was. The aqueous phase was collected and the concentration of each pre-extracted noble metal ion was measured using an atomic absorption photometer.
Table 3 shows the back extraction rate of each noble metal ion by various back extractants.

  When 36 mass% hydrochloric acid was used, not only Rh (III) but also Pd (II) showed a high back-extraction rate.

  The extractant of the present invention can selectively extract Rh ions from a solution containing base metal and platinum group metal ions. This makes it possible to selectively recover Rh ions from a material containing Pt, Pd and Rh ions, such as a three-way catalyst for automobiles.

Claims (2)

The following formula I:

[Where:
R ¹ and R ² are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-18 alkyl, C _2-18 alkenyl or C _2-18 alkynyl, or substituted or unsubstituted straight Chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that R ¹ and R ² are not the same);
R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4 alkynyl, or substituted or unsubstituted straight A chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl, or
R ³ and R ⁴ are cycloalkyl or aryl fused to the imidazole ring together with the carbon atom on the imidazole ring to which they are attached (the cycloalkyl or aryl fused to the imidazole ring is unsubstituted, Or is substituted by one or more halogens]
A metal ion extractant comprising a compound represented by :
The extractant, wherein the metal ion is a platinum group metal ion selected from the group consisting of rhodium and palladium . An aqueous phase containing metal ions is represented by the formula I:

[Where:
R ¹ and R ² are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-18 alkyl, C _2-18 alkenyl or C _2-18 alkynyl, or substituted or unsubstituted straight Chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl (provided that R ¹ and R ² are not the same);
R ³ and R ⁴ are independently of each other hydrogen, substituted or unsubstituted linear or branched C _1-4 alkyl, C _2-4 alkenyl or C _2-4 alkynyl, or substituted or unsubstituted straight A chain or branched C _7-18 arylalkyl or C _8-18 arylalkenyl, or
R ³ and R ⁴ are cycloalkyl or aryl fused to the imidazole ring together with the carbon atom on the imidazole ring to which they are attached (the cycloalkyl or aryl fused to the imidazole ring is unsubstituted, Or is substituted by one or more halogens]
In in contact with the organic phase containing the compound represented by saw including an extraction step of extracting metal ions in the organic phase,
A method for recovering metal ions, wherein the metal ions are platinum group metal ions selected from the group consisting of rhodium and palladium .

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