JP3101948B2 - "Three-coordinate pyridyl podand compound, silver ion separating agent and silver ion recovery method using the compound". - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel three-coordinated pyridyl podand compound, a silver ion separating agent for separating and recovering silver ions from industrial wastewater such as a photographic processing solution or natural water using the compound. And its collection method.

[0002]

2. Description of the Related Art In order to protect nature and living environment, industrial waste liquid is made non-polluting, and the technology of reusing resources contained in this waste liquid is a large industry. A large amount of silver ions are contained in the photographic processing waste liquid generated from the photographic industry, and its recovery and reuse are important issues in this technical field, and many techniques have been proposed to solve this. I have. A typical example of this is disclosed in Japanese Patent Laid-Open No. 50-9883.
No. 7, JP-A-6-88276 and the like.
No. 0-22463 and the like, reverse osmosis method,
No. 51-17114, etc., the ion exchange method,
-111756, 53-76029 and 59-
JP-A-135278 and JP-A-3-252656 have proposed a sedimentation method in which a poorly soluble complex salt is formed by using an organic or inorganic compound, and the deposited precipitate is collected by filtration.
The present inventors have studied the correlation between the structure of crown ether and the ability to extract and transport metal ions, and found that the ring size of crown ether, the type of heteroatoms constituting the ring, and the substituents bonded to the heteroatoms. It has been found that there is a great difference in the selectivity and efficiency of metal ion extraction and transport depending on the type of metal. In particular, it has been found that aza or diaza crown ethers having a heteroaromatic ring bonded to a nitrogen atom enable selective extraction and transport of silver ions. These achievements are described in Org. Chem. , 1992, 57, 542.
-547 and 1993, 58, 4389-4397. However, the synthesis of these azacrown ethers has a problem in production and cost, such as a long reaction step and a step requiring high pressure. Further, from the viewpoint of the properties of the material, further improvement in high selectivity and high transportability of silver ions and their efficiency are required. As described above, azacrown ethers have various problems in practical use, and materials having various practical conditions are required.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have earnestly developed a new idea based on the accumulation of technologies relating to the correlation between the structure of aza or diaza crown ether or oligopyridine derivatives and the ability to extract and transport metal ions. As a result of the investigation, they have found that the three-coordinate pyridylpodand compound can extract and transport silver ions with high selectivity and high efficiency, and have completed the present invention. A first object of the present invention is to provide a novel three-coordinated pyridylpodand compound, a second object is to provide a silver ion separating agent comprising the derivative, and a third object is to provide a derivative of the derivative. It is an object of the present invention to provide a method for selectively extracting and transporting silver ions by using an organic solvent solution in which silver is dissolved, and recovering silver ions.

[0004]

Means for Solving the Problems The present invention relates to the general formula (1)

Embedded image A three-coordinate pyridylpodand compound represented by the formula: a silver ion separating agent comprising such a compound; an organic solvent solution in which such a compound is dissolved; and an organic solvent in which silver ions are selectively extracted by contact with an aqueous solution containing silver ions. The present invention relates to a method for recovering silver ions, which comprises contacting a solution with water to produce an aqueous solution containing silver ions. Or R ₆ . R ₃ , R ₄ or R ₅ each independently represents an alkyl group which may be branched, and typical examples include a methyl group, an ethyl group, a propyl group, a butyl group, an i-butyl group, an s-butyl group, and a t-group. -A butyl group, an octyl group, a dodecyl group, an octadecyl group, a docosanyl group and the like. R
₆ represents an alkyl group, an alkenyl group or an aralkyl group which may be branched. The optionally branched alkyl group of R ₆ represents the same alkyl group as defined for R ₃ . Examples of the alkenyl group include an allyl group, a 7-octenyl group, an L-menthyl group, a 3-methyl-2-butenyl group, and a 5-hexenyl group.
-Phenylethyl group, 4-phenylbutyl group, 2-phenylbutyl group, 6-phenylhexyl group, 4-methoxybenzyl group, 4-methylbenzyl group and the like. Suitable organic solvents in the present invention include dichloromethane, chloroform, dichloroethane, chlorobenzene, benzene, toluene, diisopropyl ether, nitromethane, ethyl acetate and the like.

[0005] The three-coordinate pyridylpodand compound according to the present invention can be synthesized through the following steps by a conventional method, for example.

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Here, Step 5 for synthesizing the target compound can proceed as follows. Alcohol (1mm
ol) and dimethylaminopyridine (2 mmol) in anhydrous dichloromethane at 0 ° C. over a few minutes is added dropwise a solution of 2,6-pyridinedicarboxylic acid dichloride (0.5 mmol) in anhydrous dichloromethane. After the dropwise addition, the mixture is stirred for a while at the same temperature, then returned to room temperature and further stirred for a while. The reaction mixture is then diluted with dichloromethane, water,
Wash with saturated saline. The organic layer is dried over anhydrous magnesium sulfate, the solvent is distilled off under reduced pressure, and the residue is purified by silica gel column chromatography.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

[0008]

Example 1 The following compounds can be mentioned as typical compounds according to the present invention.

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[0009]

Example 2 The synthesis of Compound 1 of the present invention will be described below for each step.

Reaction of Step 1 (When R ₁ = H) A mixed solution (8 ml) of 2,6-dibromopyridine (6 mmol) in anhydrous hexane: ether: tetrahydrofuran, 1: 2: 1 is added under a stream of argon. At 78 ° C., butyllithium (hexane solution, 6 mmol) was added, and the mixture was stirred at the same temperature for 15 minutes, and then added with dimethylformamide (9 mmol).
l) was added dropwise. The reaction temperature was raised to −50 ° C. for 30 minutes, and methanol (2 ml) was added, and the temperature was returned to room temperature. Thereafter, sodium borohydride (about 13 m
mol) was added and stirred for 20 minutes. Ethyl acetate (300 ml) was added to the reaction solution, washed with water (6 ml × 3) and saturated saline (6 ml), and dried over anhydrous magnesium sulfate. After evaporating the solvent under reduced pressure, the residue was purified by silica gel column chromatography (hexane containing 15% ethyl acetate) to obtain 2-bromo-6-hydroxymethylpyridine in a yield of 75%. After purification, it will gradually crystallize if left in a refrigerator for a long time. This has a melting point (mp) 3
2 to 34 ° C., and the results of nuclear magnetic resonance (NMR) and elemental analysis are as follows.

Reaction of Step 2 (R ₁ ） H) 2-bromo-6-hydroxymethylpyridine (10 mm
ol) in dimethylformamide (15 ml),
After addition of imidazole (40 mmol) at room temperature, t-
Butyldimethylsilyl chloride (11 mmol) was added in five portions and stirred for 1 hour. The reaction mixture was diluted with a mixed solvent of ethyl acetate: hexane: 1: 9 (200 ml), and washed with water (15 ml × 3) and saturated saline (15 ml). The extract was dried over anhydrous magnesium sulfate,
The solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane containing 0 to 10% ethyl acetate) to give oily 2-bromo-6-{(t
-Butyldimethylsilyl) oxymethyldipyridine was obtained in a yield of 93%.

Reaction of Step 3 (when R ₁ = H, R ₂ = H) 2-bromo-6-{(t-butyldimethylsilyl) oxymethyl} pyridine (1 mmol) in anhydrous hexane: ether: tetrahydrofuran, 1 : Butyllithium (1 mmol, 1.56 M hexane solution) was added dropwise to a mixed solution of 2: 1 (4 ml) at -78 ° C under an argon stream. After stirring at the same temperature for 15 minutes, dimethylacetamide (1.5 mmol) was added dropwise, and the mixture was stirred at the same temperature for 15 minutes.
After the completion of the reaction, water (8 ml) was added, and the mixture was returned to room temperature with vigorous stirring. Ethyl acetate: hexane, 3:
7 (100 ml) and extracted with water (4 ml).
× 3), and washed with a saturated saline solution (4 ml × 1). The extract was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was subjected to silica gel column chromatography (2.
5-5% hexane containing ethyl acetate)
Acetyl-6-{(t-butyldimethylsilyl) oxymethyl} pyridine was obtained with a yield of 82%. Thin layer chromatography indicated _Rf = 0.42 (hexane with 10% ethyl acetate).

Reaction of Step 4 (R ₁ = H, R ₂ = H) To a solution of methyl ketone (1 mmol) obtained in Step 3 in methanol (1 ml) was added sodium borohydride (1 mmol) at room temperature for 10 minutes. Stirred. Ethyl acetate (50 ml) was added to the reaction mixture to dilute it.
1) and washed with saturated saline (6 ml). The ethyl acetate extract was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (hexane containing 15 to 20% ethyl acetate) to obtain oily pyridylethanol in a yield of 93%.

[0013] To a solution of the above pyridylethanol (1 mmol) and paradimethylaminopyridine (DMAP, 2 mmol) in anhydrous dichloromethane (5 ml) was added a solution of 2,6-pyridinedicarboxylic acid dichloride (0.5 mmol) in anhydrous dichloromethane (2.5 ml) at 0 ° C. For 5 minutes. After stirring at the same temperature for 10 minutes, the mixture was returned to room temperature and further stirred for 30 minutes. The reaction mixture was diluted with dichloromethane (35 ml), washed three times with water (3 ml) and then with saturated saline. The organic layer was dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (dichloromethane containing 20% ethyl acetate) to obtain the target compound 1 in a yield of 92%. .

1 shows physicochemical properties and analysis results of the compound of the present invention.

[0015]

[0016]

[0017]

[0018]

Embodiment 3

Extraction experiment The compound according to the present invention as a carrier and the comparative compound
A solution in which 03 mmol was dissolved in 3 ml of dichloromethane was mixed with an aqueous solution in which 0.03 mmol of a metal perchlorate salt was dissolved in 3 ml of water, and the mixture was stirred at room temperature for 2 hours. Thereafter, the aqueous layer was separated, the metal ion concentration was determined by an atomic absorption method, and the extraction percentage was calculated by dividing the extracted metal ion amount (mol) by the initial addition amount (mol) of the metal ion to the aqueous phase. . Table 1 shows the results.

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From Table 1, it is clear that the compounds according to the present invention selectively extract silver ions. Further, the efficiency is twice or more as large as that of the comparative compound 2 of diaza crown ether, which is known to have very excellent properties in known compounds. Comparative Compound 3 is a crown ether similar to Comparative Compound 2, and has a high ability to extract silver ions. However, no selectivity was observed. Comparative compound 4 is a similar skeleton compound in which the pyridine ring in the center is replaced with a benzene ring, but almost no silver ion extraction ability is recognized. Comparative compound 1 is a compound to be created by the present inventors. Compared with the compound of the present invention, it has a structure in which substituents at both ends of the molecule are not present, and has a very high silver ion extraction ability, but is poor in selectivity. Further, the formed complex has poor solubility and precipitates as a precipitate.

Embodiment 4

Transport Experiment A carrier 0.0 was placed at the bottom of a U-shaped glass cell with an inner diameter of 2.0.
18 mmol (Comparative compounds 2 and 3 have 0.0372 mmol
l) is dissolved in 12 ml of dichloromethane, and AgClO ₄ , Pb (Cl) is placed on one arm of a U-shaped glass cell.
O ₄ ) ₂ , Cu (GlO ₄ ) ₂ , Ni (ClO ₄ ) ₂ ,
An aqueous solution in which 0.5 mmol / l of a mixture of the six metal salts of Co (ClO ₄ ) ₂ and Zn (ClO ₄ ) ₂ was dissolved in 5 ml of water was added, and 5 ml of water was added to the other arm, and dichloromethane was added at room temperature. The layers were stirred with a magnetic stirrer. The transport rate of silver ions is Ag (or ClO ₄ ) into water.
It was determined by dividing the amount of movement (mol) of ions by the transportation time (h). Table 2 shows the results.

From Table 2, it can be seen that the compounds of the present invention have a high silver ion transport rate, and in consideration of the extraction rate results in Table 1, a group of compounds having excellent selectivity and efficiency in extracting and transporting silver ions in high selectivity and efficiency. It is. Comparative Compound 3 is a crown ether having a heteroaromatic ring bonded thereto as in Comparative Compound 2, but has a very low silver ion transport rate. Comparative compound 4 has a structure very similar to that of the compound of the present invention, but has a very low silver ion transport rate. Comparative compound 1
Has a much lower silver ion transport rate than the compound of the present invention. On the other hand, the high selective extraction power of silver ions is larger than that of the compound of the present invention. Thus, it is considered that the substituents bonded to both ends of the basic skeleton play an important role in the transport performance of silver ions. The compound of the present invention has a special ether group or silyl ether group at both ends of the molecule, improves the solubility of the ligand alone and the silver complex in the solvent used, and improves the efficiency of silver ion separation and transport. be able to. Further, it has excellent hydrolysis resistance, and can extract and transport silver ions under a wide range of pH conditions. No decomposition is observed even if the mixture is stirred at room temperature for 24 hours under alkaline conditions of pH 12 in a dichloromethane-water system. The compound of the present invention has a non-cyclic structure, but when it encounters a silver ion in an organic solution, it becomes a cyclic structure similar to crown ether (not a completely closed ring), and a nitrogen atom of a pyridine ring or an ester oxygen atom constituting the ring The silver ion is appropriately stabilized by the coordination by the lone pair of electrons and the electrostatic interaction by the CO dipole, and the distortion of the cyclic structure due to the steric hindrance by the alkyl ether group or alkyl silyl ether group at both ends of the molecule. It is considered that silver ions are easily released when they are trapped or come into contact with water (water not containing silver ions) after being trapped. The silver ions transferred to the aqueous layer can be recovered by adding a salt, hydrogen sulfide, or the like to precipitate as a poorly soluble salt, or can be precipitated on the cathode surface by electrolysis and recovered. Further, from the state extracted with an organic solvent, the solvent can be distilled off to separate and recover as a complex salt. Comparative Compound 1 has a very high ability to form a highly selective complex and has a low transporting power, and thus is a material for insolubilizing and separating silver ions.

[0023]

As described above in detail, according to the present invention, silver ions can be selectively, efficiently and efficiently obtained from an image processing waste solution such as a photographic processing solution, a metal ion solution containing silver ions as impurities, or mineral water. It becomes possible to recover with purity.
Therefore, the present invention is useful in terms of resource reuse and environmental conservation.

Claims (3)

(57) [Claims] 1. A compound of the general formula (1) It represents the R _6. R ₃ , R ₄ or R ₅ each independently represents an alkyl group which may be branched, and R ₆ represents an alkyl group, an alkenyl group or an aralkyl group which may be branched. The three-coordinated pyridylpodand compound represented by). 2. A compound of the general formula (1) (The meaning of the symbol is the same as described above.) A silver ion separating agent comprising a three-coordinate pyridylpodand compound represented by the following formula: 3. A compound of the general formula (1) (The meaning of the symbol is the same as above.) An organic solvent solution in which a three-coordinate pyridyl podand compound represented by the following formula is dissolved is brought into contact with an aqueous solution containing silver ions to selectively extract silver ions. A method for recovering silver ions, comprising producing an aqueous solution containing silver ions by contacting with water.