JP2000351624A - Purification of niobium oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously carry out the purification of niobium oxide of several times to several ten times as much as ion exchange capacity by adjusting the concentration of niobium of an aqueous solution of hydrofluoric acid containing tantalum and niobium as ions to a specific value or a smaller than it and circulating the aqueous solution through an anion exchange resin. SOLUTION: The concentration of niobium in an aqueous solution of hydrofluoric acid is <=60 g/l calculated as niobium pentoxide. Crude niobium oxide containing a tantalum component is treated with hydrofluoric acid of <=15 times the molar amount of niobium oxide and tantalum (e.g. >=80% highly concentrated hydrofluoric acid) to dissolve tantalum and niobium. An undissolved substance is separated and removed and the solution is mixed with water and hydrofluoric acid and adjusted to a fixed concentration. High-purity niobium and tantalum can be readily recovered by previously removing a metal (cation) to become an impurity in a solution to be treated. An ore or a niobium alloy containing niobium and tantalum or industrial niobium oxide having about 98% purity can be purified by the method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for separating tantalum and niobium. Further, it is a method for obtaining high-purity niobium oxide.

[0002]

2. Description of the Related Art Niobium oxide is widely used in the fields of electronics and optics. In these fields, niobium oxide having high purity is required. In particular, niobium oxide having a low metal content has been demanded for use as a raw material for producing a lithium niobate single crystal.

For this reason, methods for purifying niobium oxide have heretofore been proposed, for example, methods such as fractional crystallization, solvent extraction, ion exchange resin, and distillation.

However, ores for obtaining niobium,
For example, columbite and niokalite coexist with tantalum together with niobium. And, niobium and tantalum are very similar in physical and chemical properties, so that it was extremely difficult to separate them. For this reason, many means have been proposed for recovering compounds containing these elements from ores together. For example, according to U.S. Pat.No. 2,962,327 and JP-A-58-176128, an ore containing niobium and tantalum is finely pulverized, and this is mixed with hydrofluoric acid and a mineral acid such as sulfuric acid. Treatment, dissolving niobium and tantalum together with iron, manganese, calcium, rare earth element and other metal impurities, and bringing this into contact with an organic solvent such as lower aliphatic ketone, ester or ether, especially methyl isobutyl ketone, etc. And a method of extracting and separating tantalum into an organic solvent phase, or flowing the solvent through an F-type anion exchange resin layer, once adsorbing niobium and tantalum to the anion exchange resin, separating from other impurities, and then fluorinating. A method of eluting and recovering with an aqueous solution of hydrochloric acid and ammonium chloride has been proposed.

Further, various means for separating niobium and tantalum have been studied. Conventionally, a method of separating niobium and tantalum by utilizing a difference between a salting-out agent concentration and a hydrogen ion concentration in an aqueous solution, that is, niobium. and in aqueous solutions for coexistence of tantalum by decreasing the concentration of hydrofluoric acid and a mineral acid, niobium is varied from NbF ₇ ^2-to NbOF ₅ ^2-, the other tantalum that there remains TaF ₇ ^2- Utilizing such a method, tantalum is extracted with an organic solvent such as methyl isobutyl ketone, or conversely, a method of re-extracting niobium from the tantalum and niobium once extracted into the organic solvent to the acidic aqueous solution side is used. I have.

In these methods, as described in JP-A-62-158118, since methyl isobutyl ketone is considerably dissolved in water, it is difficult to completely separate tantalum and niobium. The aqueous phase must be washed with methyl isobutyl ketone, such as by a step mixer settler. Therefore, JP-A-64-31937 discloses that an organic solvent selected from oxygen-containing organic solvents such as trioctylphosphine oxide or an alkylamine having an alkyl group having 4 or more carbon atoms is provided on a porous carrier such as activated carbon or polypropylene. A method of adsorbing tantalum using an adsorbent having immobilized or cross-linked thereto and removing the tantalum from a solution is disclosed. However, it is difficult to obtain an adsorbent obtained by crosslinking an organic solvent, and when the organic solvent is impregnated in a porous carrier, elution of the organic solvent into an aqueous phase becomes a problem.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present inventors
Various studies were made on a simpler and lower-cost means for separating niobium and tantalum, and the present invention was completed.

[0008]

That is, the present invention provides a hydrofluoric acid aqueous solution containing tantalum and niobium as ions.
The method for separating tantalum and niobium is characterized in that the niobium is adjusted to a concentration of 60 g / l or less, preferably 1 to 40 g / l in terms of niobium pentoxide, and is passed through an anion exchange resin layer.

According to the present invention, by flowing the above prepared aqueous solution through the anion exchange resin layer, tantalum is adsorbed on the anion exchange resin, and niobium flows out preferentially.

Therefore, according to the present invention, it is possible to easily recover high-purity niobium or tantalum by removing a metal (cation) as an impurity from the solution to be treated in advance. That is, the present invention purifies a crude niobium oxide such as an ore or a niobium alloy containing niobium and tantalum or a commercially available industrial niobium oxide having a purity of about 98% by a known treatment means, and a mixture of niobium and tantalum is obtained. After obtaining, the present invention is also useful as a purification method for obtaining niobium or tantalum with high purity.

Further, by dissolving the crude niobium oxide with a small amount of hydrofluoric acid (hereinafter referred to as hydrofluoric anhydride) having a high concentration of 80% by weight or more and separating an insoluble portion, anions in the solution are substantially reduced. It was found to contain only niobium and tantalum containing ions. Therefore, as another preferred embodiment of the present invention, a crude niobium oxide containing a tantalum component is treated with hydrofluoric acid in a molar amount of 15 mol times or less, preferably 1 to 14 mol times the amount of the tantalum, with respect to the niobium oxide and the tantalum. And after dissolving niobium, the concentration of niobium in the solution is adjusted to 60 g / l or less in terms of niobium pentoxide by separation and removal of undissolved substances and addition of water or hydrofluoric acid. Also provided is a method for separating tantalum and niobium, particularly a method for purifying niobium, which is characterized by being distributed.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention basically provides a method for separating niobium and tantalum from an aqueous solution in which an anion containing a niobium element and an anion containing a tantalum element are mixed. As a means for this, a tantalum-containing anion is selectively adsorbed on the anion exchange resin by passing through an anion exchange resin layer.
For this reason, as an obstacle to the separation, an anionic impurity can be cited. For example, it is not preferable that a large amount of sulfate ions, chloride ions, or complex anions containing other metals coexist. However, fluorine ions have little interference. Generally, the amount of impurity anions other than fluorine ions is preferably 0.5 mol / l or less.

Further, the present invention can be suitably used when niobium contains tantalum in an amount of impurities, for example, 10% by weight or less, preferably 1% by weight or less. From this viewpoint, it is preferable to use a commercially available industrial niobium oxide having a purity of niobium oxide of about 98% as the raw material used in the present invention. However, the raw materials for obtaining the mixture of niobium and tantalum used in the present invention are not limited to these, and minerals containing niobium and tantalum, for example, columbite, niokalite, tantalite, stroberite, samarskite, tin slag A substance containing niobium and tantalum, such as iron-niobium (tantalum) alloy, irrespective of the quantitative ratio thereof, is used. These raw materials are prepared by a conventionally known method or the above-mentioned small amount of hydrofluoric anhydride, that is, the reaction between niobium and tantalum and hydrofluoric acid in the raw mineral, Nb ₂ O ₅ + 14HF → 2H ₂ NbF ₇ + 5H ₂ O In consideration of Ta ₂ O ₅ + 14HF → 2H ₂ TaF ₇ + 5H ₂ O, the molar amount is not more than 15 mol times, preferably 1 to 14 mol times, especially 12 mol times with respect to niobium oxide and tantalum oxide in the raw material mineral substance. It was treated with ~ 14 times the molar amount of anhydrous hydrofluoric acid, NbF ₇ niobium and tantalum ^2-, NbOF ₅ ^2-, and TaF ₇
^2- is dissolved as a complex anion, and impurities insoluble in the environment, such as iron, manganese, calcium, and rare earths, are separated by a known separation means such as filtration or sedimentation separation, and niobium present in the solution is separated. Is 60 g / l in terms of niobium pentoxide
Hereinafter, water or hydrofluoric acid, particularly dilute hydrofluoric acid is added so as to be preferably 1 to 45 g / l, and more preferably 20 to 40 g / l for the reason described later. Of course, in the process after treating with hydrofluoric anhydride and dissolving niobium and tantalum,
After adjusting the concentration by adding water or dilute hydrofluoric acid, insoluble impurities may be separated and removed.

The aqueous solution thus obtained is passed through the anion exchange resin layer. In this case, the niobium concentration is adjusted to 6
By adjusting the content to 0 g / l or less, tantalum ions are selectively adsorbed to the anion exchange resin, and niobium flows out of the anion exchange resin layer. Needless to say, when the amount of tantalum adsorbed exceeds the limit of the adsorption capacity of the anion exchange resin and breaks through, the separation of niobium and tantalum becomes impossible. In that case, the separation operation may be stopped and the anion exchange resin may be regenerated by a known means.

In the present invention, the niobium concentration is adjusted to the above-mentioned 60 g.
It is important that the ratio be not more than / l. The effect of niobium concentration is shown in FIG. FIG. 1 shows the niobium solution concentrations (in terms of niobium pentoxide) shown in Examples 1 to 5 of the present specification and Comparative Example 1, and
It is a figure which shows the relationship with the amount of niobium pentoxide isolate | separated and collected. It is clear from FIG. 1 that when the niobium concentration reaches 70 g / l, it is no longer possible to separate niobium and tantalum. This fact is quite surprising.

Further, as can be understood from FIG. 1, the lower the concentration of niobium pentoxide, the larger the amount of niobium recovered. Especially 2
At 5 g / l or less, the recovered amount is further increased. Therefore, it is naturally preferable to use the concentration of 5 g / l or less.
Using a lower concentration would require processing a larger amount of the solution to obtain the same amount of niobium. Normally, niobium is recovered by introducing ammonium into the niobium solution and precipitating and separating niobium hydroxide. However, since the waste liquid contains a large amount of ammonium ions and fluorine ions, it is not possible to discard it as it is from the viewpoint of environmental pollution. It is possible, and measures such as introducing alkali such as lime into waste liquid and distilling and recovering ammonium must be taken. The optimum concentration considering the cost required for such waste liquid treatment is 2 in niobium pentoxide.
It is preferably from 0 to 40 g / l.

The type of the anion exchange resin in the present invention is not particularly limited. A commercially available anion exchange resin may be used. For example, as the ion exchange group, an anion exchange resin in which a quaternary ammonium base, an amino group, or the like is chemically bonded to the base resin directly or via another group is used. In addition, the base resin having a known structure can be used without any limitation. Generally, it is a styrene-divinylbenzene copolymer or the like. Specifically, commercially available strong basic anion exchange resin type I resin, strong basic anion exchange resin I
I-type resins, weakly basic anion exchange resins, polyamine-type chelate resins and the like can be used. Above all, a strongly basic anion exchange resin type I or a strongly basic anion exchange resin type II resin having a quaternary ammonium group is more preferable because the amount capable of continuously purifying niobium oxide is large.

For the contact between the aqueous solution of hydrofluoric acid-containing niobium oxide and the anion exchange resin, a column packed with an anion exchange resin in advance is used, and a packed column type adsorption method or the like in which the aqueous solution of hydrofluoric acid-containing niobium oxide is passed. Is preferred.

The anion exchange resin after contact with the hydrofluoric acid-containing niobium oxide may be reused after regeneration, if necessary. For the regeneration of the anion exchange resin, an aqueous solution of a mineral acid such as hydrochloric acid or sulfuric acid, or an aqueous solution of a water-soluble inorganic salt containing chlorine or fluorine such as ammonium chloride, sodium chloride, ammonium fluoride or sodium fluoride can be used. .

Since niobium purified according to the present invention is in an aqueous solution, it is preferable that the niobium be separated from the aqueous solution by a known method and converted into niobium oxide by a method such as firing. A method of baking at a temperature of about 1000 ° C. in a heating furnace such as an electric furnace after crystallizing an aqueous solution by adding an alkali such as ammonia or an alkali aqueous solution, and heating and evaporating water under atmospheric pressure or reduced pressure to remove niobium. After obtaining as a solid, a method such as a method of baking at about 1000 ° C. in a heating furnace while blowing steam can be used.

[0021]

When the present invention is used to purify niobium oxide, the purity of niobium oxide can be increased by a simple operation such as passing a hydrofluoric acid-containing niobium oxide aqueous solution through a commercially available anion exchange resin.

In the conventional purification of niobium oxide using an ion-exchange resin, the method involves once adsorbing the niobium oxide on the ion-exchange resin and then purifying the solution by flowing a separation solution. Although it is not possible to purify niobium oxide in an amount exceeding the exchange capacity of the resin, it is possible to continuously purify niobium oxide several to several tens times the ion exchange capacity by using the method according to the present invention. It becomes possible.

[0023]

EXAMPLES Example 1 A 1-liter transparent FEP resin (tetrafluoroethylene-
A container made of hexafluoropropylene copolymer) was charged with 140.4 g of niobium oxide containing 600 ppm of tantalum and a magnetic stirrer, and a SUS316 lid was attached. 145.6 g of hydrofluoric anhydride (13.8 times the molar amount of niobium oxide) was added to this container, and the mixture was stirred using a magnetic stirrer. Twenty minutes after the addition of hydrofluoric anhydride, the vessel was opened, 100 ml of pure water was added, and insolubles were removed by filtration. At this time, the amount of insolubles was 0.4 g. Next, the filtrate was diluted with pure water to make a total volume of 4 l, and 35 g / l
A hydrofluoric acid-containing aqueous solution of niobium oxide was prepared.

Next, Duolite A113 (manufactured by Sumitomo Chemical Co., Ltd., total exchange capacity: 1.3 eq / l) is applied to a column made of FEP resin (1/2 inch in inner diameter, 60 cm in length), which is a strongly basic anion exchange resin type I resin. After filling with 20 g and washing with 300 ml of 1 mol / l hydrofluoric acid aqueous solution, 150 ml of pure water
And washed.

The previously prepared 35 g / l niobium oxide solution was passed from the top of the column at a rate of 2.5 ml / min. The liquid flowing out from the lower part of the column was separated every 30 ml, and the tantalum concentration in the liquid was measured by inductively coupled plasma emission analysis. 2010m 35g / l niobium oxide solution
No tantalum is detected until after passing
When passing 040 ml, tantalum was detected.
At this time, the processing amount of niobium oxide was 70.4 g. 12.1 mol of niobium could be purified per liter of resin.

The liquids until tantalum is detected are collected,
Niobium was crystallized by adding 25% aqueous ammonia.
The crystals were separated by filtration with a polytetrafluoroethylene filter and washed with water, and the obtained crystals were fired at 900 ° C. for 6 hours to obtain 68.2 g of niobium oxide. The niobium oxide obtained here was dissolved in 50% hydrofluoric acid and inductively coupled plasma mass spectrometry was performed. As a result, the concentration of tantalum in the niobium oxide was 0.5 ppm or less based on the niobium oxide.

To regenerate the ion exchange resin, 600 ml of a 1 mol / l ammonium fluoride aqueous solution was passed through the column. After washing the column with 300 ml of pure water and passing a 35 g / l niobium oxide solution in the same manner as above, the amount of the solution in which tantalum was detected was 1950 to 1980 ml,
Niobium oxide treatment amount 68.3 g, niobium oxide amount after crystallization 6
With 6.2 g and a tantalum concentration of 0.5 ppm or less, almost the same results as in the first test were obtained. Examples 2 to 5 Example 1 except that the niobium oxide concentration was changed to the concentration shown in Table 1.
The ion exchange resin and the hydrofluoric acid-containing aqueous niobium oxide solution were continuously brought into contact with each other in the same manner as in the above. For each niobium oxide concentration, Table 1 shows the amount of the treatment solution from which tantalum was removed, the amount of niobium oxide treatment, the amount of niobium oxide after crystallization, and the concentration of tantalum contained in niobium oxide after crystallization.

[0028]

[Table 1] Comparative Example 1 A 70 g / l aqueous solution of hydrofluoric acid-containing niobium oxide was prepared in the same manner as in Example 1. When the ion-exchange resin was continuously contacted as in Example 1, tantalum was detected from the initial solution and could not be separated from niobium oxide.
Tantalum concentration in niobium oxide obtained by crystallizing and firing 30 ml of the initial solution as in Example 1 was 580 ppm based on niobium oxide. Examples 6 to 11 In the same manner as in Example 1, niobium oxide was purified by changing only the ion exchange resin. The ion exchange resin used was Diaion SA as a strongly basic anion exchange resin type I resin.
12A (Mitsubishi Chemical), Amberlite IRA400
(Manufactured by Organo), DIAION SA20AP (manufactured by Mitsubishi Chemical Corporation) as a strongly basic anion exchange resin II resin, and Duolite A368S as a weakly basic anion exchange resin.
(Sumitomo Chemical) Diaion WA20 (Mitsubishi Chemical) As a polyamine type chelate resin, Diaion CR20
(Mitsubishi Chemical).

Table 2 shows the resin used, the amount of the treating solution from which tantalum was removed, the amount of niobium oxide treated, the amount of niobium oxide after crystallization, and the concentration of tantalum contained in niobium oxide after crystallization.

[0030]

[Table 2] Comparative Example 2 A 35 g / l hydrofluoric acid-containing niobium oxide aqueous solution was prepared in the same manner as in Example 1. Next, Diaion HP20, which is a porous styrene-divinylbenzene copolymer, is used.
20 g (manufactured by Mitsubishi Chemical Corporation, specific surface area: 600 m ² / g) is immersed in 100 ml of an ether solution containing trioctylamine,
After filtration, the resin was air-dried to prepare a resin carrying trioctylamine. After packing in a column in the same manner as in Example 1, a 35 g / l aqueous solution of niobium hydrofluoride was passed through. As a result, tantalum was detected in a processing liquid amount of 60 ml, and the processed amount of niobium oxide was 2.1 g. Was. Also,
The amount of niobium oxide obtained by crystallization and firing in the same manner as in Example 1 was 1.5 g, and the concentration of tantalum in niobium oxide analyzed by inductively coupled plasma mass spectrometry was 40 ppm with respect to niobium oxide. there were.

As a regenerating solution, 600 ml of a 1 mol / l aqueous solution of ammonium fluoride was passed through a column filled with the treated resin, washed with water, and passed again with a 35 g / l solution of niobium oxide. As a result, tantalum was detected from the initial solution, and tantalum could not be separated from niobium oxide. Examples 12 to 15 Purification was performed in the same manner as in Example 1 except that the amount of hydrofluoric anhydride added to niobium oxide was changed when preparing an aqueous niobium oxide solution. Table 3 shows the molar ratio of hydrofluoric anhydride to niobium oxide, the amount of the treatment solution capable of removing tantalum, the amount of niobium oxide treatment, the amount of niobium oxide after crystallization, and the concentration of tantalum contained in niobium oxide after crystallization.

[0032]

[Table 3] Example 16 A 1-liter transparent FEP resin (tetrafluoroethylene-
Hexafluoropropylene copolymer), 139.2 g of niobium oxide containing 600 ppm of tantalum and 450 ppm of iron and a magnetic stirrer were placed in a container made of SUS316.
A lid made of steel was attached. In this container, 144.4 hydrofluoric acid was added.
g (13.8 times the molar amount of niobium oxide and tantalum) was added, and the mixture was stirred using a magnetic stirrer. 20 minutes after the addition of hydrofluoric anhydride, open the container and add
By adding 0 g, an aqueous solution of niobium fluoride was obtained. Next, the aqueous solution of niobium fluoride was passed through a 0.2 μm membrane filter made of polytetrafluoroethylene,
Insoluble matter was removed by filtration. At this time, the amount of insoluble matter was 0.5 g
Met.

The metal in the filtrate was analyzed by inductively coupled plasma emission spectroscopy.
ppm or less. The tantalum concentration was 600 ppm based on niobium oxide. Next, the filtrate was diluted with pure water to a total volume of 4 l to prepare a 35 g / l hydrofluoric acid-containing aqueous niobium oxide solution. An ion-exchange resin packed column equivalent to that used in Example 1 was prepared and passed under the same conditions as in Example 1 to obtain a solution of 35 g / l niobium oxide in 2010 m.
No tantalum is detected until after passing
When passing 040 ml, tantalum was detected.
At this time, the processing amount of niobium oxide was 70.4 g. 12.1 mol of niobium could be purified per liter of resin.

The liquids until tantalum is detected are collected,
Niobium was crystallized by adding 25% aqueous ammonia.
The crystals were separated by filtration with a polytetrafluoroethylene filter, washed with water, and calcined at 900 ° C. for 6 hours to obtain 68.5 g of niobium oxide. The niobium oxide obtained here was dissolved in 50% hydrofluoric acid and inductively coupled plasma mass spectrometry was performed. As a result, the concentration of tantalum in the niobium oxide was 0.5 ppm or less based on the niobium oxide.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the concentration of niobium and the amount of separated and recovered in the present invention.

Claims (2)

[Claims] An aqueous solution of hydrofluoric acid containing tantalum and niobium as ions is converted to niobium by conversion to niobium pentoxide.
A method for separating tantalum and niobium, comprising adjusting the concentration to not more than g / l and flowing the anion exchange resin layer. 2. A crude niobium oxide containing a tantalum component is treated with hydrofluoric acid in an amount of 15 mol times or less of the niobium oxide and the tantalum to dissolve the tantalum and the niobium. 2. The tantalum and niobium according to claim 1, wherein the concentration of niobium in the solution is adjusted to 60 g / l or less in terms of niobium pentoxide by adding water or hydrofluoric acid, and then flowing through the anion exchange resin layer. Separation method.