JPS5929527B2 - Metal ion separation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for extracting and separating metal ions from an aqueous solution containing metal ions.

Specifically, the present invention relates to a method for extracting and separating specific metal ions from an aqueous solution containing one or more metal ions using an acidic phosphoric acid ester and an aliphatic amine as an extraction solvent, or for separating metal ions from each other. Therefore, the present invention is particularly effective in separating and purifying a specific cloth from a sheet mixture or separating it from each other.

In recent years, solvent extraction has been widely used as a separation and purification method on cloth, and the extraction solvent used is di(2-ethylhexyl)phosphoric acid (hereinafter referred to as D2EHPA).

) is the most commonly used.

D2EHPA is a type of cation exchange liquid, and is known as an excellent extraction solvent for separation and purification on cloth because it has a high separation coefficient between each cloth (and has a high extraction ability for each cloth).

However, in order to back-extract the cloth extracted with D2EHPA, the large extraction ability of D2EHPA on the cloth becomes an obstacle, and a large amount of concentrated acid must be used.

Conventionally, back extraction on a cloth from D2EHPA has been carried out using 5 to 6 N hydrochloric acid or nitric acid, and the number of stages is 3 when the back extraction operation is performed in parallel flow and 5 stages in the case of countercurrent flow. is considered necessary.

In addition, with heavy rare earths such as ytterbium and lutetium, which have particularly high distribution coefficients on cloth, even if a large amount of acid is used for back extraction, a small amount of heavy rare earths may remain in the solvent. In high-purity on-site manufacturing, there arises a problem that these remaining heavy rare earths become a source of contamination, making it difficult to obtain high-purity products.

The inventors of the present invention have made extensive studies to solve these problems in the prior art, and have found that separation can be easily carried out by a solvent extraction method using a mixed solvent of an acidic phosphoric acid ester and an aliphatic amine as an extraction solvent. We have arrived at the present invention by discovering that it is possible to back-extract ions on the surface and that the above-mentioned solvent extraction method can be applied not only to ions on the surface but also to metal ions in general.

An object of the present invention is to provide an industrially advantageous extraction and separation method for metal ions, particularly predominant ions, and the purpose is to extract and separate metal ions by bringing an aqueous solution containing metal ions into contact with an extraction solvent. In the method, an extractant of the general formula (wherein R1 represents a hydrogen atom, an alkyl group having 4 to 18 carbon atoms or an allyl group, and R2 represents an alkyl group having 4 to 18 carbon atoms or an allyl group) is used as an extraction solvent.

] and the general formula [wherein,
R3, R4 and R5 are hydrogen atoms or have 6 to 12 carbon atoms
represents an alkyl group.

] This can be easily achieved by using a mixed solvent of aliphatic amines shown in the following.

The present invention will be explained in detail below.

Metal ions to which the method of the present invention can be applied include yttrium, lanthanoids with atomic numbers 57 to 710, copper, zinc,
titanium, iron, nickel, scandium, zirconium,
Ions of transition metals such as hafnium, niobium, and tantalum,
Examples include ions of typical metals such as gallium and indium, but the present invention is particularly suitable for separating and purifying a specific ion from a mixture of yttrium and lanthanoids, or for mutually separating a mixture of yttrium and lanthanides. It is.

To prepare an aqueous solution containing ions of the metal, p
Salts of the metals soluble in the aqueous solution of pH 1 to 9, such as nitrates, chlorides, sulfates, etc., may be dissolved in the aqueous solution of pH 1 to 9.

Furthermore, the efficiency of separating metal ions from each other can be increased by coexisting a chelating agent such as diethylenetriaminepentaacetic acid in the aqueous solution containing metal ions.

In the method of the present invention, the general formula C1 is used as an extraction solvent.
A mixed solvent of an acidic phosphoric acid ester represented by , ll and an aliphatic amine represented by the general formula (II) is used.

Among acidic phosphoric acid esters and aliphatic amines, acidic phosphoric acid esters are involved in the extraction of metal ions, and aliphatic amines rather reduce the distribution coefficient of metal ions.

On the other hand, the ratio of the distribution coefficients of each metal ion, that is, the separation coefficient, is almost the same as when the acidic phosphate ester is used alone as the extraction solvent.

In addition, in the ion exchange extraction method using a cation exchange solution such as the method of the present invention, increasing the pH of the aqueous solution phase increases the distribution coefficient of metal ions. The amount of metal ions extracted per unit amount can be made equivalent to the case where acidic phosphate ester is used alone as the extraction solvent.

The acidic phosphoric acid esters used in the method of the present invention include di(2-ethylhexyl) phosphoric acid, dibutyl phosphoric acid, dioctyl phosphoric acid, monodecyl phosphoric acid, monododecyl phosphoric acid, etc., and in particular di(2-ethylhexyl) phosphoric acid. Phosphoric acid is preferred.

Examples of aliphatic amines include primary amines such as tert-icoxy/L/7mine, 1-(3-ethylpentyl)-4-ethyloctylamine, secondary amines such as di(2-ethylhexyl)amine, and trihexyl. amine, trin-
Octylamine, triisooctylamine, tri-n-
Tertiary amines such as laurylamine are used.

Lower alkyl amines have a high solubility in water and their solvent composition changes during use, making them unsuitable for use.
Higher alkylamines have high melting points and are difficult to handle.

The amount of aliphatic amine used is usually 0.1 to 1.5 mol, preferably 0.2 to 1 mol, per 1 mol of acidic phosphoric acid ester.
It is a mole.

In the method of the present invention, it is generally desirable to dilute the extraction solvent using an organic solvent as a diluent in order to reduce the viscosity of the extraction solvent and facilitate the extraction process.

Suitable diluents include petroleum fractions such as kerosene, paraffins such as hexane and decane, ethers such as isopropyl ether, and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene.

The amount of diluent used is such that the concentration of acidic phosphate ester is 0.1.
~1.5 mol/l, preferably 0.2-1.0 mol/l
It is preferable in terms of extraction operation to select such that 1.

As mentioned above, the method of the present invention involves ion exchange extraction using a cation exchange solution, so as the extraction progresses, the pH of the aqueous solution phase decreases.

In the method of the present invention, it is effective to adjust the pH of the aqueous solution phase after the extraction to 0 to 3, preferably 1 to 2; for example, the pH of the aqueous solution before metal ion extraction is
This can be done by adjusting H to the above pH after extraction, or by adding a base such as ammonia during the extraction operation.

Furthermore, the pH can be stably maintained within the above range by adding a potassium chloride-hydrochloric acid or sodium acetate-hydrochloric acid buffer to the metal ion-containing aqueous solution.

If the pH of the aqueous solution phase becomes too low, extraction of metal ions will not proceed sufficiently, and if it is too high, gelation of the acidic phosphate ester ion-exchanged with metal ions will occur, so care must be taken.

By performing the extraction operation described above, metal ions are extracted into the extraction solvent, but in order to isolate the metal as a suitable salt and recycle the extraction solvent, the metal ions can be back-extracted from the extraction solvent. is necessary.

Reverse extraction can be performed using mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid according to known methods, but when metal ions are extracted by the method of the present invention, the reverse extraction is more efficient than conventional methods. Since extraction can be performed, the amount of mineral acid used can be reduced, and the number of back extractions can be reduced.

Furthermore, as mentioned earlier, when an acidic phosphoric ester is used as an extraction solvent together with an aliphatic amine, the partition coefficient decreases, but the ion exchange capacity of the acidic phosphoric ester remains virtually unchanged; By increasing the pH of the containing aqueous solution, it is possible to obtain the same extraction efficiency as when using acidic phosphate ester alone as an extraction solvent, so the method of the present invention has great industrial value.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example I D2EHPA and tri-n-octylamine (hereinafter referred to as
It's called TOA.

) and 0.0.5.0.7 for D2EHPA, respectively.
Same as above except that 4 types of extraction solvents mixed in 5 and 1.0 times volume were diluted with kerosene to make the D2EHPA concentration 0.5 mol/l and toluene was used instead of kerosene solution and kerosene. Similarly, D2EHPA
A toluene solution of an extraction solvent with a concentration of 0.5 mol/l was prepared, and a total of eight types of extractants were prepared.

These extractants were mixed with an aqueous solution with a yttrium chloride concentration of 0.1 mol/l in a volume ratio of 1:1, and aqueous ammonia was added so that the pH of the aqueous solution phase became 1 after reaching extraction equilibrium. and adjusted it.

FIG. 1 shows the distribution coefficient of Y3+ when each extraction agent was used.

In Figure 1, the horizontal axis represents the capacity ratio of TOA to D2EHPA, the vertical axis represents the partition coefficient of Y3+ (Y3+ concentration in organic liquid phase/Y3+ concentration in aqueous solution phase), and curve 1 shows kerosene as a diluent. Curve 2 uses toluene as a diluent.

Example 2 D2EHPA concentration is 0.5 mol/l, TOA is D2E
100rI toluene solution containing 3/4 times the volume of HPA
Using 100rrLl of a 0.08 mol/l yttrium chloride aqueous solution and a 0.08 mol/l ytterbium chloride aqueous solution as extractants, each ion was extracted, and almost the entire amount of the ion was extracted. was extracted.

Next, the extractant from which the ions were extracted was mixed with 6N hydrochloric acid 20771.
1 and shaken for 20 minutes using a shaker to back-extract the ions on the table.

As a result, the back extraction rate of seat ions was 98.8% for Y3+.
, Yb3+ was 94.3%.

Furthermore, when the back extraction rate was repeated in the same manner using 2 oml of 6N hydrochloric acid, the back extraction rates of Y3+ and Yb3+ were 99.9% or more and 99.8% in total for the two times, respectively.

Comparative Example 1 An experiment was conducted in the same manner as in Example 2, except that a kerosene solution containing 5 mol/l of D2EHPAO was used instead of a toluene solution containing D2EHPA and TOA as an extractant. The rate is 80% for Y3+
, Yb3+ is 33%, and Y3+ is 9 after two back extractions.
6%, Yb3+ was back extracted by 56%.

When the same back-extraction was repeated again, a total of 99% of Y3+ and 74% of Yb3+ were back-extracted.

Example 3 An aqueous solution containing 0704 mol/l of yttrium chloride and ytterbium chloride, an aqueous solution containing 0.04 mol/l of yttrium chloride and dysprosium chloride, and 0.04 mol/l of yttrium chloride and erbium chloride, respectively. 3 of the aqueous solution containing
100 ml of each of the three types of extractants were mixed with 100 ml of extractant having the same composition as that used in Example 2, and almost all of the ions on the cloth were extracted.

Next, the extractant from which the ions on the cloth were extracted was mixed with 20 ml of 6N hydrochloric acid, and the mixture was shaken for 20 minutes to back-extract the ions on the cloth.

As a result, the back extraction rates of Dy3+, Er3+ and Yb3+ were 98.9%, 98.6% and 95.0%, respectively.
There was no significant difference in the back extraction rate of Y3+ among the three types, and the average was 98.8%.

The experiment was repeated in the same manner as above except that 10 ml of 6N hydrochloric acid was used in the back extraction.

FIG. 2 shows the relationship between the back extraction rate of each ion on the fabric and the amount of 6N hydrochloric acid used for back extraction.

In Figure 2, the vertical axis is the back extraction rate (%) of ions on the fabric;
The horizontal axis represents the amount of 6N hydrochloric acid (ml), curve 3 and curve 4.
, curve 5 and curve 6 are Dy3+, y3+, E
r3+ and Yb3+ are shown.

Example 4 Extraction agent with the same composition as that used in Example 2 [Extraction agent (I)]
and extractant (II) (volume ratio of D2EHPA and TOA 2
0.08 mol/l using 100TrLl of D2EHPA (toluene solution with a concentration of 0.5 mol/l)
Y3+ was extracted from 100 ml of yttrium chloride aqueous solution, and almost the entire amount of Y3+ was extracted.

Next, the extractant from which Y3+ was extracted was mixed with 20 WLl of 6N hydrochloric acid and shaken for 20 minutes to perform back extraction of Y3+.

In the back extraction, instead of using 20ml of 6N hydrochloric acid and shaking for 20 minutes, use 20rrll of 3N hydrochloric acid for 90 min.
An experiment similar to that described above was performed except for shaking for a minute.

The results are shown in Figure 3.

In Figure 3, the vertical axis represents the back extraction rate (%) of ions on the fabric, the horizontal axis represents the hydrochloric acid concentration (normal), and curve 7 represents the extraction agent (I
), Curve 8 is a curve showing the relationship between the back extraction rate of Y3+ and the hydrochloric acid concentration when extractant (II) is used.

Example 5 An experiment was carried out in the same manner as in Example 4 except that a 0.08 mol/l ytterbium chloride aqueous solution was used instead of a 0.08 mol/l yttrium chloride aqueous solution.

The results are shown in Figure 3. In Fig. 3, curve 9 is the extraction agent (
When using I), curve 10 is a curve showing the relationship between the back extraction rate of Y3+ and the hydrochloric acid concentration when extracting agent (II) is used.

Example 6 100 ml of a 0.07 mol/l erbium chloride aqueous solution was used as an extraction material, and a toluene solution containing D2EHPA and triisooctylamine (volume ratio of D2EHPA and triisooctylamine 2:1, D2EHPA concentration 0.5 mol/l) was extracted.
l) Almost the entire amount of Er3+ was extracted using 100 ml as an extractant.

Next, the extractant from which Er3+ was extracted was mixed with 10 ml of 6N hydrochloric acid and shaken for 20 minutes to back-extract Er3+.

As a result, the back extraction rate of Er3+ was 95.0%.

A toluene solution containing D2EHPA and tri-n-hexylamine as extractants (D2EHPA and tri-n-hexylamine)
Hexylamine volume ratio 3:11 D2EHPA concentration 0.
When the same experiment as above was repeated except that 5 mol/l) was used, the back extraction rate of Er3+ was 94.8%.

Example 7 0.05 mol/l yttrium chloride aqueous solution 100 ml
was used as the extraction material, and a toluene solution containing D2EHPA and di(2-ethylhexyl)amine (volume ratio of D2EHPA and di(2-ethylhexyl)amine 3:1, D
After extracting almost the entire amount of Y3+ using 100 ml of 2EHPA (concentration 0.5 mol/l) as an extractant, the extract from which Y3+ was extracted was mixed with 10 ml of 6N hydrochloric acid, shaken for 20 minutes, and Y3+ was back-extracted. did.

As a result, the back extraction rate of Y3+ was 982%.

An experiment similar to the above was conducted except that 100 ml of an aqueous ytterbium chloride solution of 0.05 mol/e was used as the extraction material, and the back extraction rate of Yb3+ was 90.3%.

Example 8 An aqueous solution containing 0.05 mol/l of yttrium chloride and 0.05 mol/l of ytterbium chloride is mixed with extractant 1)rnl of the same composition as used in example 2 until equilibrium is reached. After stirring, the extractant phase and the aqueous solution phase were separated, and the ion concentration on each surface of the two phases was measured, and the distribution coefficient of each ion on the fabric was determined.

The ratio of the obtained distribution coefficients (distribution coefficient of Yb''/distribution coefficient of y3+) is shown in FIG. 4 as the separation coefficient of Yb3+ with respect to ¥3+ (point 12).

Extraction was carried out in the same manner as above except that an aqueous solution containing 0.05 mol/l of chloride].lium and 0.05 mol/l of erbium chloride was used.

The obtained separation coefficient of Er3+ with respect to Y3+ is shown in FIG. 4 (point 13).

The same experiment as above was conducted except that an aqueous solution containing 0.05 mol/l of yttrium chloride and 0.05 mol/l of dysprosium chloride was used to determine the separation coefficient of Dya+ with respect to Y3+.

The results are shown in the fourth (point 14).

In Fig. 4, the vertical axis represents the separation coefficient of ions on cloth for Y3+ (partition coefficient of ions on cloth/partition coefficient of Y3+), the horizontal axis represents the type of seat, and curve 11 represents the separation coefficient of ions on cloth for Y3+. The separation coefficient of each ion on the fabric when used alone is shown.

[Brief explanation of the drawing]

FIG. 1 illustrates the results of Example 1, and Y3+
The relationship between the partition coefficient of and the volume ratio of extraction solvents D2EHPA and TOA is shown. FIG. 2 illustrates the results of Example 3, and shows the relationship between the back extraction rate of ions on the cloth and the amount of 6N hydrochloric acid. FIG. 3 illustrates the results of Example 4, and shows the relationship between the back extraction rate of ions on the cloth and the hydrochloric acid concentration. FIG. 4 illustrates the results of Example 8, and shows the separation coefficient for Y3+ of ions on the cloth.

Claims (1)

[Scope of Claims] 1. In a method of extracting and separating metal ions by bringing an aqueous solution containing metal ions into contact with an extraction solvent, the extraction solvent is a compound of the general formula [wherein R1 is a hydrogen atom, an alkyl group having 4 to 18 carbon atoms] R2 represents an alkyl group having 4 to 18 carbon atoms or an allyl group. ] and the general formula [wherein,
R3, R4 and R5 are hydrogen atoms or have 6 to 12 carbon atoms
represents an alkyl group. A method for separating metal ions, characterized by using a mixed solvent of aliphatic amines shown in ]. 2 Claim 1 in which the metal ions are ions on cloth
The method described in section.