JPH0474711A - Method for separating and purifying rare earth metal - Google Patents

Abstract

PURPOSE:To stably and readily recover a rare earth metal in a high yield by employing a water-insoluble organic solvent of formula I or II instead of a water-soluble complexing agent in a solvent extraction method. CONSTITUTION:A water-insoluble organic solvent containing a compound of objective I and/or II (but R1-4 are 8-20C saturated or unsaturated alkyl; X is O or NH) is brought into contact with an aqueous solution containing the com pound of a rare earth element to selectively extract the rare earth metal com pound in the aqueous phase. The rare earth metal extracted in the water- insoluble phase is reversely extracted with an aqueous solution containing a mineral acid.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for separating and purifying rare earth metals.

More specifically, the oil-soluble complexing agents ethylenediamine-N, N'-diacetic acid-N, N'-diacetic acid alkylamides or alkyl esters or diethylenetriamine-N,N',N''-triacetic acid-N, This invention relates to a method for separating and purifying rare earth metals using N''-diacetic acid alkylamides or alkyl esters.

[Prior art and its problems] Rare earth metals include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pg), samarium (S m), europium (Eu
), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (HO), erbium (Er), thulium (Tn+), ytterbium (Yb)
) is a general term for the 17 elements of lutetium (Lu).

Due to their unique properties, rare earth metals are currently used as luminescent materials,
It is used in various fields of advanced technology such as magnetic materials. However, in all applications, extremely high purity is required.

These rare earth metals are contained in small amounts of multiple types at the same time in ores such as monazite, banestite, and monotime. The chemical properties of these rare earth metals that are contained in small amounts at the same time are very similar7, and even if they are separated using normal methods, the purity is low, and the rare earth metals are obtained as a mixture of several types of rare earth metals. It is. As a method of refining these low-purity substances to even higher purity ones, rare earth metals present in an aqueous solution are extracted using an oil phase prepared by dissolving a conventional water-insoluble extractant in a water-insoluble solvent. A method of extracting and separating is known.

Here, specifically, the water-insoluble extractant is N-8-
Quinoline sulfonamide, E-2-hydroxy-5-nonylbenzophenone oxime, tri-n-octylphosphine oxyto, bis(2°4.4-)limethylpentyl)phosphinic acid, bis(2,4,4-trimethylpentyl) ) phosphinodithioate, triisobutylphosphine sulfide, bis(2,4,4-1-limethylpentyl)n-octylphosphine, 2-ethylhexylphosphonic acid-mono 2-ethylhexylate, tributyl phosphate, tricarbonate Butylmethylammonium salt, 2.
2. 2-1 Realkyl acetic acid etc. is used, the product name is Teha CYANEX 272.921.301.471
．． X, 925 (more than three pieces, Cyanamid ■), LIX
65N (Henke 1 company), A11quart 3
36 (Genera 1 Mills), Kelex
100 (Ashland), PC-88A (chemistry for dogs), Persatic Acid 10 (Shell Chemical)
etc. are known.

As the water-insoluble solvent, aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons are used.

Specific examples include mineral oil, paraffin oil, kerosene, light oil, naphtha, perchloroethylene, benzene, toluene, xylene, hexane, heptane, and cyclohexane.

This extraction method utilizes the fact that rare earth metal ions in an aqueous solution and an extractant in an oil phase form a complex at the oil-water interface, and the rare earth metal ions are incorporated into the oil phase. There are differences in the ability to form complexes with extractants depending on the type of rare earth metal, which makes it possible to separate and purify each rare earth metal. However, the above extraction method is not perfect; for example, it is difficult to separate yttrium from heavy rare earth elements such as erbium and holmium because there is no difference in their ability to form complexes.

Therefore, proposals have been made to increase the selectivity of rare earth metal separation. For example, in the above solvent extraction method, it is known that the separation selectivity between rare earth metals can be significantly improved by adding a water-soluble complexing agent to the aqueous phase containing rare earth metal ions during metal extraction. (Unexamined Japanese Patent Publication No. 1973-
No. 150717). Here, the water-soluble complexing agent is
Ethylenediaminetetraacetic acid salts, ethylenediamine-N,
N'-diacetates, diethylenetriamine-N, N,
Examples include N'N-N''-pentaacetic acid salts.

The following effects are assumed to be exerted by these water-soluble complexing agents on the separation and purification of rare earth metals.

The rare earth metal in the aqueous phase forms a complex with the water-soluble complexing agent, which inhibits complex formation between the extractant in the oil phase and the rare earth metal in the aqueous phase at the oil-water interface. It is thought that the degree of this inhibition differs between rare earth metals, resulting in a difference in the rate of extraction of rare earth metals into the oil phase, facilitating separation and purification. However, this method of separating rare earth metals by adding a complexing agent to the aqueous phase also has the following problems.

In other words, when performing solvent extraction of rare earth metals on an industrial scale by adding a water-soluble complexing agent to the aqueous phase, the troublesome problem of recovering the used water-soluble complexing agent must be solved. must not. Water-soluble complexing agents such as ethylenediaminetetraacetate, ethylenediamine-N, N"-diacetate, diethylenetriamine-N, N, N', N", N"-pentaacetate, etc. are expensive and industrial. It is not a disposable reagent.

Generally, it is not easy to efficiently recover highly water-soluble organic compounds from an aqueous solution. Concentration of aqueous solutions, crystallization, or separation by column chromatography requires considerable equipment and labor, and pH changes during recovery operations and decomposition of organic compounds due to heating operations require high recovery rates. Recovery is almost impossible. Naturally, the same applies to recovery of the water-soluble complexing agent. The cost of unrecovered water-soluble complexing agent and recovery operations naturally add to the price of rare earth metals, making them very expensive.

Solvent extraction of rare earth metals using a water-soluble complexing agent has the advantage of improving separation selectivity between rare earth metals, but unless the water-soluble complexing agent used can be recovered with a high recovery rate, It is impossible to use it industrially.

Therefore, an object of the present invention is to provide a complexing agent with high extraction selectivity that can replace a water-soluble complexing agent in a method for separating and purifying rare earth metals by solvent extraction, and which can be recovered stably, easily, and with a high recovery rate. The object of the present invention is to provide a separation and purification method using raw materials.

[Means for solving the problem] As mentioned above, water-soluble complexing agents significantly improve the selectivity in the separation and purification of rare earth metals, but in view of the fact that their water-solubility makes recovery difficult. The inventors believe that if the complexing agent that increases the separation selectivity of each rare earth metal is water-insoluble and oil-soluble like the extractant, it can be easily recovered in the oil phase together with the extractant and extracted. We believe that it is possible to reuse the rare earth metals after re-extracting them, and considering the effect of the water-soluble complexing agent on separation selectivity, we believe that the intended complexing agent also has the ability to form complexes with rare earth metals due to its molecular structure. As a result of continuing to check a large number of compounds that meet these conditions, they discovered that a specific compound exhibited significantly superior performance, and thus completed the present invention.

That is, the present invention provides an aqueous solution containing a compound made of a rare earth element, and a compound of the following general formula (1) (wherein R and R2 may be the same or different from each other, each having 8 to 20 carbon atoms, saturated or unsaturated). represents a saturated alkyl group, and X represents O or NH.) Ethylenediamine-N, N'-diacetic acid N,
N"-diacetic acid alkylamide or alkyl ester compound, and the following general formula (2) (wherein R3 and R
4 may be the same or different, each having 8 carbon atoms
~20 saturated or unsaturated alkyl groups, and X represents O or NH. ) of rare earth metals by contacting them with a water-insoluble organic solvent containing at least one of diethylenetriamine-NN', N"triacetic acid-N,N"-diacetic acid alkylamide or alkyl ester compounds. This is a separation and purification method.

Below, the content of the present invention will be described in further detail.

General formula (1) representing the oil-soluble complexing agent used in the present invention
, R1, R2, R3, and R4 in (2) have 8 to 2 carbon atoms.
0 saturated or unsaturated alkyl group. Alkyl groups with less than 8 carbon atoms can also improve the separation selectivity between rare earth metals, but the water solubility of the compound itself increases,
It is unsuitable for repeated use as an oil-soluble complexing agent because of loss of the oil-soluble complexing agent to the aqueous phase. Also, the number of carbon atoms is 2
Those exceeding 0 are effective - but there are problems in obtaining raw materials. Specific examples include octyl group, octenyl group, cetyl group, lauryl group, dodecenyl group, palmitoleyl group, stearyl group, oleyl group, etc. In addition to straight chain, branched alkyl groups can also be used. can.

The oil-soluble complexing agents of general formulas (1) and (2) used in the present invention can be synthesized by various methods, and there are no particular restrictions on the starting materials, production routes, types of intermediates, etc. .

An example of a method for producing (1a) having an oleyl group as R,, R2 and NH as X is shown below.

Ethylenediaminetetraacetic acid is converted into pyridine as shown in formula (A),
Acid anhydride (3) is synthesized by heating in acetic anhydride.

By reacting the obtained acid anhydride (3) with a saturated or unsaturated alkylamine suitable for the purpose, the desired compound of general formula (1) having two alkylamido groups is produced. As a specific example, when (3) is reacted with oleylamine, the reaction proceeds as shown in formula (B) to obtain compound (1a).

(1a) Next, a method for producing (2a) having oleyl groups as R3 and R4 and NH as X will be shown.

Diethylenetriamine-N, N, N', N''.

When N''-pentaacetic acid is treated with pyridine and acetic anhydride as shown in formula (C), anhydride (4) is obtained.

or an unsaturated alkylamine, the desired compound of general formula (2) having two alkylamide groups can be obtained. As a specific example, when (4) is reacted with oleylamine as shown in formula (D), a compound (2a) having two oleylamide groups is obtained.

When producing (1) or (2) using the obtained acid anhydride (4) and saturation according to the purpose, use (3) or (4) respectively as an intermediate raw material according to the purpose. By selecting an alkylamine (R1NH2, R2NH2), a desired compound can be freely produced.

Furthermore, in the general formulas (1) and (2), where X represents an oxygen atom, the compounds of the general formulas (3) and (4), respectively, are dehydrated with an alcohol having an alkyl group depending on the purpose.
It can be produced by reacting in dimethylformamide.

Furthermore, compounds in which X is NH in the general formula (1) can also be obtained by the production method shown in the following formula (E) in which R1 is an oleyl group.

(1a) That is, the compound (5) is synthesized by reacting ethylenecyaminetetraacetic acid and oleylamine, and then the compound (1a) is obtained by hydrolysis with a base. Furthermore, the compound (1) can be produced by using any alkylamine (R1NH2, R2NH2) instead of oleylamine.

Diethylenetriamine-N was prepared in a similar manner.

General formula (2) using N, N", N", N"-pentaacetic acid as raw material
Compounds of can also be produced.

In the present invention, compositions containing at least one compound represented by general formulas (1) and (2) can also be used.

Therefore, even if the compound represented by (1) or (2) is produced using saturated or unsaturated alkylamines with low purity as a raw material, a composition containing the compound (1) or (2) cannot be obtained. However, there are no problems with the performance of separating and refining rare earth metals.

Furthermore, when producing the compound (1) or (2) according to formulas (B) and (D), respectively, compositions containing various byproducts may be produced depending on the amount of alkylamine used and the reaction temperature. , this also does not cause any particular performance-42 problems.

When producing compounds (1) and (2) using formula (E), depending on the amount of base and reaction temperature, various byproducts may be produced as well, which is also a particular problem in the separation and purification of rare earth metals. does not occur.

The oil-soluble complexing agent or its composition synthesized as described above is used after being dissolved in a water-insoluble organic solvent, or the concentration thereof is 10
It is used in the range of ~103 mol/m3.

As the water-insoluble organic solvent used, aliphatic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons are used. Specific examples include mineral oil, paraffin oil, kerosene, light oil, naphtha, perchloroethylene, benzene, toluene, xylene, heptane, cyclohexane, carbon tetrachloride, dichloroethylene, and the like. In actual use, one type or a mixture of two or more types of these water-insoluble organic solvents is appropriately selected.

The extractant to be used together with the oil-soluble complexing agent or its composition, dissolved in a water-insoluble organic solvent if necessary, includes 2-
Ethylhexylphosphonic acid mono-2-ethylhexylate (PC-88A, Inuhe Kagaku ■), C(2-ethylhexyl) phosphoric acid (Tokyo Kasei ■), bis-(2,4,4-
)-limethylpentyl)phosphinic acid (CYANEX
272, Mikata Cyanamid ■), tributyl phosphate, tricaprylmethylammonium salt (Aliqu
art 336, General Mills Inc.), 2
, 2,2-trialkyl acetic acid (Persatic Acid IO, Shell Chemical), etc., are selected as appropriate depending on the type of rare earth metal to be separated and purified. 1 to 10 selected extractants or a mixture of two or more
It is used after being dissolved at a concentration of 4IIlo1/13. The presence of these extractants may also improve the solubility of the oil-soluble complexing agent used in water-insoluble organic solvents.

By contacting an extraction phase prepared by dissolving an oil-soluble complexing agent or its composition in an extractant and a water-insoluble organic solvent as necessary as described above with an aqueous solution containing a compound consisting of a rare earth element. , which separates and purifies rare earth metal compounds in aqueous solutions.

Although the aqueous phase differs depending on the rare earth metal compound to be separated and purified, it is usually adjusted to pH 5 or less using a pH adjuster, preferably pH 3 or less.

Hydrochloric acid, nitric acid, sulfuric acid, etc. are used as the pH adjuster, and various buffer solutions may also be used if necessary.

an extraction phase containing an oil-soluble complexing agent prepared as described above;
The aqueous phase to be extracted containing the rare earth metal compound is brought into contact with both phases using a fluidized liquid membrane type extraction device, such as a mixer-settler or a hollow fiber membrane type extraction device. As a result, the rare earth metal compound in the aqueous phase is selectively extracted into the water-insoluble phase or left in the aqueous phase, whereby the rare earth metal is separated and purified. In addition, the rare earth metals extracted into the water-insoluble phase are extracted with hydrochloric acid again.
By contacting with an aqueous solution containing nitric acid, sulfuric acid, etc., it is easily back-extracted to the aqueous phase side. During this time, there is little loss of the oil-soluble complexing agent used to the aqueous phase. As a result, the water-insoluble phase containing the oil-soluble complexing agent after back extraction can be used repeatedly.

Expensive water-soluble complexing agents such as ethylenediaminetetraacetate, diethylenetriamine-N,N.

When N', N'', N''-pentaacetate is used, these water-soluble complexing agents are added to the aqueous phase containing rare earth metals, so they need to be recovered from the aqueous phase after the extraction operation is completed. . However, as mentioned above, recovery of water-soluble complexing agents from dilute aqueous solutions is not easy.

It costs a lot of money and effort, and also requires considerable equipment.

Since the oil-soluble complexing agent used in the present invention is chemically stable and has almost no loss to the aqueous phase, the water-soluble complexing agent used in the present invention can be used in the separation and purification of rare earth metals. This eliminates the need for a complexing agent recovery operation and equipment, enables repeated extraction and back-extraction operations, and greatly reduces the cost required for separation and purification of rare earth metals.

[Function] The oil-soluble complexing agent used in the present invention is dissolved in the oil phase together with the extractant in order to improve the separation selectivity during the separation and purification of rare earth metals using a fluidized liquid membrane extraction device or the like. used. Although the details of the mechanism by which these oil-soluble complexing agents increase the selectivity in the separation and purification of rare earth metals are unknown, their effect is thought to be as follows.

Because the oil-soluble complexing agents used have two long unsaturated or saturated alkyl groups in their structure,
Like surfactants, it has interfacial adsorption ability. Because their interfacial adsorption capacity is greater than that of oil-soluble extractants such as PC-88A used in the extraction of rare earth metals such as holmium, erbium, and yttrium, oil-soluble complexing agents are preferentially used in oil and water. It is thought that it is adsorbed on the interface. This is thought to inhibit direct complex formation between rare earth metals and extractant molecules. However, oil-soluble complexing agents (1) and (2) have a weak but complexing ability with rare earth metals, and after bonding with rare earth metals at the interface,
It is believed that the PC-88A molecules swap and bind to the rare earth metal to extract the rare earth metal compound into the organic phase. At this time, the oil-soluble complexing agent is for holmium and erbium.
It is thought that the extraction rate of ythtrium is lower than that of holmium and erbium because it binds more strongly than ythtrium and quickly recombines with the extractant and is incorporated into the organic phase. As a result, holmium and erbium are extracted into the organic phase, and naturally the purity of yttrium in the aqueous phase is improved.

In addition, the oil-soluble complexing agent used has almost no water solubility,
Even during extraction and re-extraction of rare earth metals, they do not elute into the aqueous phase. Also, because it is chemically very stable, it hardly decomposes due to acids, heat, etc.

In other words, when actually used, if the extraction phase is adjusted by dissolving it in the oil phase together with the extractant, it can be used repeatedly. As a result, unlike when using a water-soluble complexing agent, there is no need for large-scale water-soluble complexing agent recovery equipment or labor-intensive operations, resulting in a significant cost reduction. become.

The separation and purification method of the present invention improves the separation selectivity of rare earth metals due to the above-mentioned effects of the oil-soluble complexing agent used, and also aims to industrially downsize equipment, save labor, and reduce costs. It is a very significant thing.

Furthermore, as is clear from the effect of the oil-soluble complexing agent used, the separation and purification method of the present invention is applicable not only to rare earth metals but also to the separation and purification of other metals, such as heavy metals.

[Examples] The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Production Example 1 Synthesis of oil-soluble complexing agent (1a) (1a) 91 g of ethylenediaminetetraacetic acid, 130 g of acetic anhydride, and 150 g of pyridine are placed in a reactor and stirred at 65° C. for 16 hours. After the reaction, the mixture is cooled to 20°C and precipitated crystals are filtered off. The crystals become white by filtration and washing with acetic anhydride and then diethyl ether. After washing, it was dried under reduced pressure to obtain 79 g of crystals of acid anhydride (3).

IR (Nujol, cm’) 1800.1760 (-CO-0-CO-).

Subsequently, 20 g of acid anhydride (3) and 45 g of oleylamine were added.
9 g was placed in a reactor and suspended in 200 ml of dioxane. Gradually raise the temperature to 70℃ in an oil bath and after melting,
Heat for a minute. After the reaction, it is concentrated under reduced pressure, and the residue is crystallized with ethanol, filtered, and dried to obtain 53 g of white crystalline oil-soluble complexing agent (la).

The physical property values measured for the obtained compound (1a) are shown.

(1) mp 137-138℃: (2) Elemental analysis measurement value (%) C69,43H11,18N 7.2
Theoretical value (%) C69 as 1C46H86N406,
86H10,96N 7.08゜(3) I R(
Nujol, cm') 3350.3220 (-NH
-, -COOH), 1670 (-CONH-, -C
(4) NMR (CDC13, δpp■)
0.88 (6H1t, J-7, 2xCF(3-), 1.
26 (44t(, s, 22x-C112-), 1.50
(4H, brs, 2x-C0NIICII-C11
2-), 2.00(8)(1m, 2x-Cf(-CH-
CH-Cll2-), 3.13 (411, brs, -N
-CH2CH2-N-), 3.21 (411, brs,
2x-CONI-CI2-), 3.61 (4H, brs
, 2xN-C112-COOtl), 3, Ei7 (4H
, brs, 2xN-CH2-CONII-), 5.34
(4H,brs,2x-CH-Cll-), 7.75(
2H, brs, 2x-CONI(-); (5) Solubility Soluble in toluene, benzene, chloroform, heptane, insoluble in water.

Production Example 2 In oil-soluble complexing agent (1), X is NH, R1, R2
is an octyl group, a 2-octenyl group, a 7-dodecenyl group,
Each compound having a cetyl group and a stearyl group is manufactured in Production Example 1.
It was synthesized by using the corresponding amine in place of oleylamine according to the synthesis method (1a) shown in (1a).

Production Example 3 In the oil-soluble complexing agent (1), X is an oxygen atom, R1,
A compound in which R2 has an octyl group, a cetyl group, a stearyl group, or an oleyl group was synthesized. As a synthetic intermediate, the compound (3) described in Production Example 1 was used. Compound (3), twice the mole of the corresponding alcohol, and dry N,
N-dimethylformamide (DMF) was placed in a reactor and heated at 85°C all day and night. After the reaction, it was concentrated under reduced pressure, and the residue was crystallized from ethanol to obtain each desired product.

Production Example 4 Synthesis of oil-soluble complexing agent (2a) (2a) 100 g of diethylenetriamine-N, N, N', N'', N''-pentaacetic acid, 156 g of acetic anhydride, and 130 g of pyridine were placed in a reactor and heated at 65°C for 24 hours. Heat for an hour. After heating, the mixture is cooled to room temperature and precipitated crystals are filtered off. The filtered crystals are washed with acetic anhydride and benzene and dried. As a result, 88 g of (4) was obtained as white crystals.

IR (Nujol, cm-1) 1820, 1770 (-Co-0-CO-).

1640 (-C00H).

20 g of acid anhydride (4), 32.9 g of oleylamine, and 300 ml of dioxane are placed in a reactor and refluxed in an oil bath for 1.5 hours while stirring. After refluxing, dioxane is concentrated under reduced pressure, and the residue is crystallized from ethanol. By filtering and drying the crystals, 24 g of white crystalline oil-soluble complexing agent (2a) is obtained.

The physical property values measured for the obtained compound (2a) are shown below.

(1) mp 164-166℃; (2) Elemental analysis measurement value (%) C67-06H10,71N 7.9
Theoretical value (%) CR7 as 7C5oH93N508,
30H10,51N 7.85; (3) I R(
Nujol, cm-1) 3350 (-CONH-)
, 1670 (-CONH-) , 162(1(-CO
(OH) ; (4) Solubility Soluble in toluene, benzene, chloroform, heptane, insoluble in water.

Production Example 5 In the oil-soluble complexing agent (2), each compound in which X is NH, R3, and R4 are an octyl group, a lauryl group, a 7-dodecenyl group, or a stearyl group can be synthesized by (2a) shown in Production Example 2. was synthesized by using the corresponding amine in place of oleylamine according to the method.

Production Example 6 In oil-soluble complexing agent (2), X is an oxygen atom, R3, R
Compounds in which 4 has an octyl group, a lauryl group, a stearyl group, and an oleyl group were synthesized.

As a synthetic intermediate, (4) of Production Example 4 was used.

(4) was heated and dissolved in DMF, and the corresponding alcohol was dissolved in 2
Double the mole was added and heated at 85°C for one day and night.

After the reaction, concentrate DMF under reduced pressure, then add ethanol or DMF.
Each compound was obtained by recrystallization from MF-ethanol.

Production Example 7 Synthesis of oil-soluble complexing agent (1a) (5)
(1a) Place 50 g of ethylenediaminetetraacetic acid and 46 g of oleylamine in a reactor, and add 30 ml of water. Add 5 ml of xylene. Heating is performed while stirring, and the temperature is raised while water and xylene are distilled out. After reacting at 200° C. for 2 hours, a reddish-brown solid is obtained by cooling to room temperature, which is purified by recrystallization with ethanol to obtain 120.9 g of crystal (5).

The entire amount of the obtained (5) and 100 ml of ethanol are placed in a reactor, a 5N-NaOH aqueous solution is added thereto, and the mixture is heated under reflux for 30 minutes. After cooling the reaction solution, add water to give 1.5g.
Dilute to pH 1.5 with 5N-HCΩ. The produced white precipitate is filtered and recrystallized from ethanol to obtain 11.8 g of (1a). The structure is NMR1
Confirmed by elemental analysis.

Example 1 The performance of the oil-soluble complexing agent used in the present invention was investigated using a hollow fiber membrane extraction device shown in FIG. Hollow fiber 1
is made by Japan Boretex, film thickness 1 mm, inner diameter 5 mm,
Using a porous hollow fiber Teflon membrane with a length of 30 cm (reaction area 25 cm), the hollow fiber was fixed in a glass tube 2 with an inner diameter of 8 mm, and an organic phase 3 was placed on the outside of the hollow fiber and an aqueous phase 4 was placed on the inside. It is designed to be able to flow using a metering pump, and is placed in a constant temperature bath 5.
The experiment was conducted while maintaining the temperature at 30°C. Prior to the experiment, degassed toluene or hebutane and ion-exchanged water were flowed inside and outside the hollow fibers for one hour to make the hollow fibers familiar with each solvent.

The adjusted aqueous phase of the test solution was 0. Adjust the pH to 2,05,2,2,2,3,2,5,2,8 with IN-nitric acid-0,1N-sodium nitrate, and the initial concentrations of holmium, yttrium, and erbium were each 0.5 mol/ I adjusted it to 11”.

The extraction phase uses toluene and PC-88A (2-ethylhexylphosphonic acid-mono-2-ethylhexylate)
The concentration was 50 mol/m'', and the oil-soluble complexing agent (
1a) was adjusted to 1.0 mol/m3.

The experiment was conducted by flowing an aqueous solution containing a rare earth metal adjusted to each pH and an organic phase containing (1a) and an extractant in parallel flow. Sampling was performed from each phase after the solution was allowed to flow for 1.5 hours and a steady state was reached. After back-extracting the organic phase with 6N-nitric acid, the rare earth metal concentration was determined by ICP emission spectroscopy.

Based on the measurement data, the membrane permeability coefficient PM is determined by the following formula:
(PM indicates how easily a metal can pass through a membrane. The higher the value, the faster the rate of dissolution into the organic phase. The larger the difference in PM value between rare earth metals, the easier the separation.

) was sought.

PM -Qorg CMorg/2πrLPM Membrane permeability coefficient (mol /5-rrr) Q Organic phase flow rate (m3/s) rg r Hollow fiber inner diameter (m) L Hollow fiber length (m) C Concentration of metal in organic phase ( mol/m3) org The relationship between the membrane permeability coefficient and pH of each metal is shown in FIG. As is clear from Figure 2, when the oil-soluble complexing agent (1a) is used, yttrium and holmium,
The difference in the membrane permeability coefficient of erbium is increasing. This large difference is due to the fact that oil-soluble complexing agents greatly contribute to the separation and purification of rare earth metals. In addition, unlike water-soluble complexing agents, there is no need for a recovery operation every time back extraction is performed, and there is almost no loss to the aqueous phase during rare earth metal extraction or back extraction, so it can be repeated many times without recovery operations. Therefore, the cost required for separation and purification will be greatly reduced.

Example 2 PC-88A used in Example 1, oil-soluble complexing agent (1
a) at 50 mol/m each 1. oa+ol/w
We repeatedly used a toluene phase containing 3 and investigated changes in its performance. As a result, as far as the membrane permeability coefficient is concerned,
Even after repeated use 30 times, no decrease in the contribution of rare earth metals to separation selectivity was observed.

Example 3 Instead of PC-88A used in Example 1, other extractants, di(2-ethylhexyl) phosphate, bis-(2,4,4-)limethylpentyl)phosphinic acid As in Example 1, it was confirmed that even if the metals were used, there were differences in the membrane permeability coefficients between the metals.

Comparative Example 1 During extraction, separation and purification of rare earth metals, a water-soluble complexing agent (
Changes in membrane permeability coefficient with respect to pH change with and without the addition of diethylenetriamine (N, N, NN'', N''-sodium pentaacetate) were investigated.

The aqueous phase is 0. Each pH was adjusted with IN-nitric acid-0 and IN-sodium nitrate, and the initial concentrations of holmium, erbium, and yttrium were each adjusted to 0.5 mol/3. Also, diethylenetriamine-N, N, N', N'',
Sodium N''-pentaacetate was added and adjusted to be 1.5 ol/m3. Hebutane was used as the organic phase, and extractant PC-88A was added and adjusted to be 50 ol/m3. Figure 3 shows the results of an experiment using a hollow fiber membrane extraction device.

As shown in FIG. 3, there is a difference in the membrane permeability coefficients of yttrium, holmium, and erbium when a water-soluble complexing agent is added, but there is almost no difference when no water-soluble complexing agent is added. Although the effect of adding a water-soluble complexing agent is confirmed as shown in FIG. 3, it is not easy to recover the water-soluble complexing agent from the aqueous phase after rare earth metal back extraction. In fact, an aqueous solution containing a water-soluble complexing agent (diethylenetriamine-N, N, N'
N'', N''-pentaacetic acid, approximately 0.6%) in 20% H
Although the pH was varied from 5 to 1 using C1, no crystals were deposited and could not be recovered. Further, an attempt was made to concentrate the aqueous solution under reduced pressure, but the solution gradually became colored, and even when concentrated to a concentration of about 10%, no precipitation occurred and the solution could not be recovered.

Furthermore, even if the same volume of methanol or isopropyl alcohol as the aqueous solution was added to the concentrated aqueous solution, diethylenetriamine-N, N, N', N", N"-pentaacetic acid could not be recovered, which shows that water-soluble complexes It can be seen that recovery of the curing agent is extremely difficult. Moreover, the repeated use 30 times described in Example 2 is unexpected. The oil-soluble complexing agent used in the present invention does not require any recovery operation (as in Example 2, it can be used repeatedly, and has great industrial significance).

Example 4 The aqueous phase was adjusted to pH 2.3 with 0.1N nitric acid-0.1N sodium nitrate, and the initial concentrations CMo of holmium, yttrium, and erbium were each adjusted to 0.5 mol/m. Toluene was used for the organic phase, and the extractant PC-88
The concentration CI of A (RO was 50 mol/m2) and the concentration Cs of the oil-soluble complexing agent (1a) was 0.05 to 2 mol/m2.
Performance was investigated using a hollow fiber membrane extractor in the range of l/m3. The results are shown in FIG. Yttrium, holmium, and erbium exhibit a sufficient difference in membrane permeability coefficient for separation at any concentration (1a). Incidentally, when compared with the case where C=0, in which (1a) is not added, the effect of the oil-soluble complexing agent used in the present invention is clear.

Example 5 In the oil-soluble complexing agent (1), X synthesized in Production Example 2 is NHSR, R2 is an octyl group, a 2-octenyl group,
Performance evaluation was performed under the same conditions as in Example 3 for those having 7-dodecenyl group, cetyl group, and stearyl group.

As a result, as in (1a), the concentration of each complexing agent was 10II
At IO11I113 or higher, a significant difference occurred between the membrane permeability coefficients of yttrium, holmium, and erbium, confirming the effect of the oil-soluble complexing agent (1).

Example 6 In the oil-soluble complexing agent (1), X synthesized in Production Example 3 is an oxygen atom, Rt and R2 are an octyl group, a cetyl group,
Performance evaluation was performed on those having a stearyl group and an oleyl group under the same conditions as in Example 3. As a result, at a concentration of each compound of 10 mol/m'' or higher, a significant difference occurred between the membrane permeability coefficients of yttrium, holmium, and erbium, confirming the effectiveness of each compound.

Example 7 The performance of the oil-soluble complexing agent (2a) was evaluated under the same conditions as in Example 3. The results are shown in Figure 5. The concentration of (2a) is 101
Differences occur in membrane permeability coefficients between rare earth metals at 101/II3 or higher, and at 1 agol/n+3, erbium,
A clear difference was seen between the metals holmium and yttrium, confirming the effect of the oil-soluble complexing agent (2a).

Example 8 In the oil-soluble complexing agent (2), one in which X, NH, R, and R4 synthesized in Production Example 5 have an octyl group, a uryl group, a 7-dodecenyl group, and a stearyl group, Performance evaluation was performed under the same conditions as in Example 5. As a result, (2a
), when the concentration of each complexing agent was 10-1/3 or more, there was a significant difference in the membrane permeability coefficient between the metals, confirming the effect of the oil-soluble complexing agent.

Example 9 The oil-soluble complexing agent (2) synthesized in Production Example 6 in which X has an oxygen atom and R and R4 have an octyl group, a lauryl group, a stearyl group, or an oleyl group was used as Example 5. Performance evaluation was performed under similar conditions. As a result, when the concentration of each complexing agent was 10' mol/3 or more, a significant difference occurred in the membrane permeability coefficient between each metal, confirming the effectiveness of each oil-soluble complexing agent.

Example 10 The effects on the separation of praseodymium (Pr) and neodymium (Nd) were investigated using the novel oil-soluble complexing agents (1a) and (2a). The aqueous phase has a concentration of each metal of 0.5-〇1/I3, and p
H is 0. It was adjusted to 2.85 with IN-nitric acid.

Toluene was used for the extraction phase, and the extractant was PC-88A (
50 mol/m3), oil-soluble complexing agent (1a), (2a
) was set at 1 mol/m'' each. For comparison, a separation experiment using only the extractant without adding an oil-soluble complexing agent was also conducted. The experimental method and measurement method were the same as in Example 1.

The results are shown in Figure 6, and (1a) and (2a)
), there was a difference in the membrane permeability coefficient of rare earth metals, confirming the effect of adding these oil-soluble complexing agents.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a hollow fiber membrane extraction device used in an example of the present invention to examine the performance of a novel oil-soluble complex-forming compound. FIG. 2 is a graph showing the results of Example 1 of the present invention,
Holmium when adding the new oil-soluble complexing agent (1a),
Membrane permeability coefficient and pH of each metal, yttrium and erbium
Indicates the relationship between FIG. 3 is a graph showing the results of Comparative Example 1 of the present invention,
Water-soluble complexing agent (diethylenetriamine N, N, N', N
Figure 4 is a graph showing the results of Example 4 of the present invention. and
The relationship between the added concentration of the novel oil-soluble complexing agent (1a) and the membrane permeability coefficient of each metal of holmium, yttrium, and erbium is shown. FIG. 5 is a graph showing the results of Example 6 of the present invention,
The relationship between the added concentration of the novel oil-soluble complexing agent (2a) and the membrane permeability coefficient of each metal of holmium, yttrium, and erbium is shown. FIG. 6 is a graph showing the results of Example 8 of the present invention,
The relationship between the membrane permeability coefficients of praseodymium and neodymium when novel oil-soluble complexing agents (1a) and (2a) are added and when they are not added is shown. Codes in the figure: 1...Hollow fiber; 2...Glass tube; 3.
...Organic layer; 4...Aqueous phase; 5...
・Thermostatic bath. Figure 2.0 3.0 og s Figure 4 Y Mouth H. △ Er Diagram

Claims (1)

[Claims] An aqueous solution containing a compound made of rare earth elements, and the following general formula (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) (In the formula, R_1 and R_2 may be the same or different from each other) Commonly, each represents a saturated or unsaturated alkyl group having 8 to 20 carbon atoms, and X represents O or NH. ▼(2) (In the formula, R_3 and R_4 may be the same or different and each represents a saturated or unsaturated alkyl group having 8 to 20 carbon atoms, and X represents O or NH.) A method for separating and purifying rare earth metals, which comprises contacting a water-insoluble organic solvent containing at least one type of compound.