JPS6183624A - Separation of europium - Google Patents

Abstract

PURPOSE:To obtain europium in high yield and purity, easily from a mixture of rare earth metals containing bivalent europium and trivalent rare earth metals other than europium, by adding a specific substance to the mixture. CONSTITUTION:A mineral acid solution of a rare earth metal mixture containing bivalent europium and trivalent rare earth metals other than europium is extracted with an extractant (e.g. acidic phosphoric acid ester, phosphonic acid ester, higher fatty acid, etc.) in the presence of absorbic acid (preferably 1-10mol of ascorbic acid per 1mol of europium), to separate europium from the mixture. The mineral acid solution of the rare earth metal mixture is preferably prepared by reducing a mineral acid solution of a rare earth metal mixture containing trivalent rare earth metal and trivalent rare earth metals other than europium with a reducing agent such as zinc or zinc alloy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for separating europium.
More specifically, the present invention relates to a method for separating europium from a rare earth mixture containing covalent europium and trivalent hosts other than hyperobium.

[Conventional technology]

Demand for europium has increased in recent years as a phosphor for televisions and high color rendering lamps, and the europium used for these applications must be of high purity.

However, in order to make europium highly pure, it is better to separate it using the same method as other parasitic elements.

The next two points are tsumashi.

■ Since the amount of europium in the ore is extremely small, in order to purify europium, it is necessary to remove large amounts of other rare earth elements.

■ There are no extractants or complexing agents suitable for separating europium from samarium and gadolinium, which are neighboring elements.

Therefore, one separation is extremely difficult.

However, unlike other parasitic elements, europium can exist as a divalent ion in an aqueous solution, and this property is used for separation.

That is, a rare earth solution containing 21-rubium is brought into contact with zinc under a nitrogen atmosphere to reduce europium to covalent, and then an organic solvent is added to extract the trivalent host element, and the covalent europium is extracted. A method has been proposed in which europium is separated from other diluents by leaving it on the aqueous phase side (for example, Japanese Patent Application Laid-open No. 2003-229003).

[Problem that the invention seeks to solve]

However, in this separation method, divalent europium is unstable and cannot be used during one separation.

There is a problem in that it is easily oxidized by oxidizing impurities such as trace amounts of oxygen present, resulting in a decrease in europium separation efficiency. ,% This tendency is remarkable in the first stage made of products other than europium, that is, in the stage where europium is a trace component.

[Means for solving problems]

As a result of various studies in view of the above-mentioned problems in separating divalent europium, the present inventors have found that the presence of a specific substance improves the separation efficiency between europium and other hosts. We discovered this fact and arrived at the present invention.

That is, 1. The gist of the present invention is a method for separating europium by extracting a mineral acid aqueous solution of rare earth mixed metal containing covalent europium and trivalent host other than europium using an extractant. The rare earth mixture used in the present invention refers to the group including ythtrium in a method for separating europium, which is characterized in that the separation is carried out in the presence of ascorbic acid. Mineral acid salts such as chlorides, sulfates, perchlorates, and salts of raw rare earth mixtures containing valent host, especially mineral acid aqueous solutions of chlorides, are reduced to reduce europium to a divalent state, etc. can be obtained by the following method.

Specifically, raw materials containing less than 1 normal europium i/% obtained from ores such as monazite and bastnaesite, or the residue of cerium group mixed rare metals obtained from these ores, are conventionally used. Other hosts, especially light rare earths (lanthanum, cerium), are separated by methods such as solvent extraction or ion exchange to increase the concentration of europium in the rare earths as much as possible. In addition, since it is difficult to separate samarium and gadolinium using conventional methods, 30% of a rare earth mixture of industrial 11-t europium, samarium, and gadolinium is used in
It is used as an aqueous mineral acid solution. The concentration of the trivalent host mixture aqueous solution is desirably at least /y7, and more preferably at least IOf/, because if it is too low, a large apparatus will be required for the following operations, which is not industrially advantageous.

Next, the host mixed aqueous solution containing trivalent europium is reduced to make europium in a divalent state. The refund method is
A method using a reducing agent, an electrolytic reduction method, etc. can be adopted, but as a reducing agent, it is preferable to use zinc powder with a large specific surface area and 1% zinc or a zinc alloy such as zinc amalgam. ~20 times the f is good.

If too little is used, the reduction rate of europium will be insufficient, and if too much is used, there will not be a big difference in the reduction rate, so it is economically unfavorable. is pg o, t~6. Preferably pHO,/~3
It is best to adjust it to If the pE is too low, the reduction efficiency of zinc will decrease, and if it is too high, the host component will precipitate as a hydroxide, making it undesirable.0The feature of the invention is the separation of divalent europium and trivalent other fabrics. It is preferable to have ascorbic acid present in the system especially from the time of zinc reduction.The amount of ascorbic acid used at this time is 1 to 10 moles per mole of europicum. For the reduction reaction, use an inert gas such as nitrogen to exclude oxygen from the mixture on the cloth, and if ascorbic acid is added, after the addition and mixing.

Add the zinc powder while stirring for at least 3 minutes.

Preferably, it is carried out for 70 minutes or more.

The obtained mineral acid aqueous solution of the host mixture containing monovalent europium and other trivalent fabrics can be used as is, or if solid zinc remains, after removing it by F separation etc. Extraction is performed using an extractant in the presence of ascorbic acid.

The trivalent cloth is extracted into an extractant phase, and the divalent europium is separated by remaining in the aqueous phase.

Extraction agents are used for extraction on cloth.The well-known extraction solvents are
Any difference can be used.
dimethyl-/'-methylbutyl)-! -Methyloctyl] phosphoric acid, an alkyl phosphoric acid ester having an alkyl group having 6 to 3 Q carbon atoms, -monoethylhexylphosphonic acid mono-λ-ethylhexyl ester, an alkyl group having 6 to 30 carbon atoms. Alkyl phosphonic acid alkyl ester with 5, naphthenic acid/♂0° naphthenic acid 23
0 etc. 7thenic acids, persaticill 9//,
Extraction solvents include tertiary fatty acids typified by persatic acids such as Persatic 10, higher fatty acids such as incaprylic acid, and the like as active ingredients.

Since the active ingredients listed above are liquids with high viscosity,
In order to facilitate the extraction operation, it is usually used after being diluted with an organic solvent. As an organic solvent.

Petroleum fractions such as crocene, aliphatic hydrocarbons such as hexane, octane, and decane, ether Q such as dibutyl ether and diisopropyl ether, alcohols such as n-hexanol, benzene, toluene, xylene, and diethylbenzene. aromatic hydrocarbons, etc., and the concentration of active ingredients is 0.00/comole/l.
, preferably 0.0! ~/,! It is preferable to use it as a solution in mol/l.

The amount of extractant used is that the amount of active ingredients in the extractant is at least 3 times the mole of the amount on cloth other than europium.

Preferably, it is selected so that the molar amount is about ♂ to lθ times. If the amount of active ingredients in the extractant is too small, the separation of europium and non-europium on the cloth will not be sufficient.Conversely, even if an excess of 10 is used, no special effect can be expected.

This is not a good idea as it requires a large device.

In order to efficiently separate europium from other fabrics during extraction using the above extractant, alkali metal hydroxide or ammonia is added to the mineral acid aqueous solution or extractant during extraction or to the host mixture. It is also possible to do so. If the amount of alkali metal hydroxide or ammonia used is too large, it is possible to increase the purity of europium, but europium will also migrate to the extractant phase, and the yield of europium will decrease. to be determined.

In the extraction operation of the present invention, in order to avoid oxidation of monovalent europium during the operation, it is desirable to exclude oxygen, and to remove oxygen by introducing an aqueous solution of the host mixture and an inert gas such as extractant Vc nitrogen. It is preferable to use it as oxygen and introduce an inert gas such as nitrogen into the extractor to remove oxygen.

From the acidic aqueous solution containing covalent europium obtained from the above extraction operation, europium is obtained as an oxalate, carbonate, hydroxide, etc. according to a conventional method.

As explained above, it is most preferable to add ascorbic acid before or during the reduction, but even if ascorbic acid is added during extraction, there are limitations regarding the situation in which ascorbic acid is present. Since migration can be restricted, this invention also includes adding to the mineral acid aqueous solution or extractant of the edible mixture after reduction of the present invention #i.

[For production]

Although the action of ascorbic acid in the present invention is not necessarily clear, it stabilizes the reduced divalent europium, inhibits the oxidation of europium to trivalent by oxygen in an aqueous solution, and is present during reduction by zinc. It is speculated that it sometimes acts as an auxiliary agent for zinc to improve the reduction efficiency of europium.

〔Effect of the invention〕

According to the method of the present invention, europium can be easily obtained in a high yield and with high purity by simply adding a specific substance, so it is extremely advantageous industrially.

〔Example〕

The present invention will be explained in more detail below by way of examples.

Examples/~G 4t of L-ascorbic acid, Of, was added to a dilute aqueous solution of chloride containing ≦-robium (trivalent on cloth) with a pH of 7 shown in Table 1, and nitrogen was added at a rate of 0.3t/min. 3 at flow rate
After bubbling for 0 minutes to remove dissolved oxygen,
Europium was reduced by adding /, /62 of zinc powder.

On the other hand, as an extraction agent, 1 gicoethylhexyl phosphate was added.
The ammonia water shown in Table 1 was added to the gecoethylhexyl phosphate extractant prepared by dissolving it in diethylbenzene to give a concentration of mol/lK. After removing the europium, an extraction operation was performed using an aqueous gold chloride solution obtained by reducing the europium.

Table 2 shows the results of measuring the concentration of europium in the aqueous phase relative to the total soil and the ratio of europium extracted in the extraction phase to the total europium.

Table 2 shows the results obtained by carrying out the same operations as in Comparative Examples/- to Examples/-, except that no L-ascorbic acid was added.

Table 1 Comparing Examples/~ and Comparative Examples/~.

When the same amount of ammonia water is added, the concentration of europium in the water phase is higher in the example.

That is, the purity of the separated europium is high.

Furthermore, less europium was extracted into the extraction phase together with other cloths in the examples, in other words.

The yield of europium in the aqueous phase is improved, Applicant Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (and 7 others)

Claims (7)

[Claims] (1) In a method of separating europium by extracting a mineral acid aqueous solution of a rare earth mixture containing divalent europium and trivalent rare earth other than europium using an extractant, the above separation is carried out in the presence of ascorbic acid. A method for separating europium, which is characterized by the following: (2) The method for separating europium according to claim 1, wherein the extraction agent is an acidic phosphoric acid ester, a phosphonic acid ester, or a higher fatty acid. (3) The method for separating europium according to claim 1 or 1, characterized in that ascorbic acid is present in 1 to 10 moles per mole of europium. (4) A mineral acid aqueous solution of a rare earth mixture containing tetravalent europium and a trivalent rare earth other than europium is used to form a rare earth mixture containing trivalent europium and a trivalent rare earth other than europium. The method for separating europium according to claim 1, 2 or 3, characterized in that europium is obtained by reducing a mineral acid aqueous solution. (5) Claim 4, characterized in that a reduction treatment is performed after ascorbic acid is added to a mineral acid aqueous solution of a rare earth mixture containing trivalent europium and a trivalent rare earth other than europium. Separation method for europium. (6) The method for separating europium according to claim 4 or 5, wherein the reduction treatment is performed using zinc or a zinc alloy. (7) Zinc or zinc alloy for europium
The method for separating europium according to claim 6, characterized in that 20 times equivalent amount is used.