JP3407821B2 - Method for purifying oxide or hydroxide of tantalum or niobium - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a method for purifying tantalum or niobium oxides or hydroxides containing impurities, more specifically, a crude separation in the production process of tantalum or niobium oxides or hydroxides. The present invention relates to a method for purifying the obtained impurity-containing intermediate raw material or an insufficiently purified impurity-containing product.

[0002]

BACKGROUND OF THE INVENTION The most commonly practiced process on the industrial scale today for producing purified tantalum, niobium oxides or hydroxides is the solvent extraction process. In this solvent extraction method, an ore or concentrate is first subjected to dissolution treatment with hydrofluoric acid, and the acid concentration is adjusted with sulfuric acid to prepare a raw material liquid. When this raw material liquid is brought into contact with a solvent such as MIBK, tantalum and niobium compounds are extracted into the solvent, while impurities such as Fe compounds remain in the raffinate liquid and are removed. Next, the niobium compound is back-extracted by bringing the solvent containing the tantalum and the niobium compound into contact with dilute sulfuric acid, and the niobium compound is transferred to the aqueous phase to become an aqueous solution, while the tantalum compound remains in the solvent. By bringing the solvent containing the tantalum compound into contact with water, the tantalum compound is back-extracted to obtain an aqueous solution of the tantalum compound. Each of these aqueous solutions is neutralized with aqueous ammonia to form a precipitate of tantalum or niobium hydroxide, and then the tantalum or niobium hydroxide is recovered by filtration. In such a solvent extraction method, a mixer-settler or an extraction tower is used for extraction and back extraction.

At present, it is possible to obtain niobium oxide, niobium hydroxide or the like having a low purity as a raw material for niobium, and refining them produces tantalum and niobium at a lower cost than manufacturing from ore. be able to. Also,
At present, the above solvent extraction method is also used when purifying an impurity-containing intermediate raw material or an insufficiently purified impurity-containing product obtained by rough separation in the production process of tantalum or niobium oxide or hydroxide. There is.

Solvents used in the above solvent extraction method, especially MI
Since BK has a low flash point, it is restricted by the Fire Service Law regarding its handling and storage. Further, the vapors of these solvents are harmful to the human body, and it is necessary to take measures to secure a working environment. Further, when MIBK is used as a solvent, MIBK has a solubility in water, and therefore is lost little by little, so that supplementation is required. Since the above-mentioned solvent extraction method uses expensive hydrofluoric acid, not only the cost becomes high, but also many restrictions are imposed on the material and handling of the equipment, which not only complicates the equipment but also keeps the working environment. It also costs money.

[0005]

The present invention has been made in view of the above problems of the prior art, and the object of the present invention is to use potassium hydroxide which is inexpensive and easy to handle and simple equipment. To provide a novel purification method of tantalum or niobium oxide or hydroxide containing impurities.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above problems, and as a result, by using potassium hydroxide, oxides or hydroxides of tantalum or niobium containing impurities can be obtained. The present inventors have found that the purification of can be carried out at a normal pressure with simple equipment, and have reached the present invention.

That is, the method for purifying oxides or hydroxides of tantalum or niobium of the present invention is a method of purifying oxides or hydroxides of tantalum or niobium containing impurities in a potassium hydroxide concentration of 130 g / l or more, preferably 200 g. / L or more and a temperature of 25 ° C. or higher, preferably 60 ° C. or higher in potassium hydroxide aqueous solution at atmospheric pressure for 2 hours or more to dissolve tantalum or niobium oxide or hydroxide as a potassium salt,
The produced slurry containing insoluble impurities is filtered to remove impurities, an acid is added to the filtrate to precipitate a hydroxide of tantalum or niobium, and the precipitate is recovered.

In the present invention, the tantalum or niobium oxide or hydroxide containing impurities used as a starting material means the impurities contained in the tantalum or niobium oxide or hydroxide obtained in the crude separation process. It means an intermediate raw material or a product containing impurities that have not been sufficiently purified, such as F
e Nb (OH) ₅ with 0.055%, Nb ₂ O ₅ and Fe with 0.09% Fe content and 0.01% Ti content
Nb ₂ O ₅ with a content of 1.75% and a Ti content of 0.22%
Etc. can be illustrated.

In the present invention, first, an oxide or hydroxide of tantalum or niobium containing impurities, for example, niobium hydroxide (in the following description, the case where niobium hydroxide is used) is hydroxylated. Potassium concentration 1
It is added to an aqueous potassium hydroxide solution having a liquid temperature of 30 g / l or more and a liquid temperature of 25 ° C. or more, preferably heated. In this case, the raw material niobium hydroxide is preferably finely pulverized in advance.
The generated slurry is stirred for a predetermined time while being kept within a predetermined temperature range. After the lapse of a predetermined time, the slurry consists of an aqueous solution of niobium hydroxide potassium salt and insoluble impurities. Therefore, the slurry is filtered to remove the impurities, and an aqueous solution of potassium salt of niobium hydroxide is obtained. Collect. An acid is added to the recovered aqueous solution of niobium hydroxide potassium salt while stirring to neutralize it to around neutrality, whereby a niobium hydroxide precipitate is formed. By recovering this precipitate by filtration or the like, niobium hydroxide having an extremely small amount of impurities can be obtained. Instead of adding an acid to generate a niobium hydroxide precipitate, sodium hydroxide may be added to generate a sodium salt precipitate.

The present invention and its effects will be described in more detail based on the following examples.

[0011]

【Example】

Examples 1 to 7 Using a 2-liter polyethylene bottle as a dissolution tank,
The polyethylene bottle was immersed in an oil bath so that the liquid content of the polyethylene bottle was maintained at a constant temperature. A lid was provided to prevent evaporation of the liquid content of the polyethylene bottle, and this lid was provided with a hole for accommodating the rotating shaft of the stirrer. A small stirrer equipped with a Teflon stirring blade on the rotary shaft was used, and the rotary shaft was installed through the hole provided in the lid. Into this polyethylene bottle, 1 liter of an aqueous potassium hydroxide solution having a potassium hydroxide concentration shown in Table 1 was placed and maintained at the liquid temperature shown in Table 1. 200 g of niobium hydroxide having an Fe content of 0.029% pulverized with a small mixer was added to the polyethylene bottle and stirred for the time shown in Table 1. After stirring for a predetermined time, the resulting slurry was cooled, vacuum filtered with a Buchner funnel to remove insoluble impurities, and the filtrate was collected. The collected filtrate was sampled and the Nb and Fe concentrations were analyzed by ICP emission spectroscopy. The Nb distribution ratio in the filtrate and Fe / Nb ₂ O in the filtrate were analyzed.
A ratio (%) of ₅ was obtained. The results are shown in Table 1. Also,
Hydrochloric acid was added to the recovered filtrate to neutralize it to pH 7.0 or lower, and a niobium hydroxide precipitate was formed. Then, vacuum filtration was performed using a Buchner funnel to obtain niobium hydroxide.

[0012]

[Table 1]

As is clear from the data in Table 1, niobium hydroxide was dissolved as a potassium salt in a potassium hydroxide aqueous solution at a dissolution temperature of 25 ° C. or higher, a dissolution time of 2 hours or longer, and a potassium hydroxide concentration of 130 g / l or higher. However, it seems that the preferable conditions for industrially effective purification are a dissolution temperature of 60 ° C. or higher, a dissolution time of 2 hours or longer, and a potassium hydroxide concentration of 200 g / l or higher. However, it is expected that the dissolution (distribution ratio) of niobium hydroxide in the potassium hydroxide aqueous solution will reach a peak when the dissolution temperature is 70 ° C and the dissolution time is 6 hours. Therefore, the dissolution temperature is 70 ° C and the dissolution time is 6 hours. The degree seems to be the most economically advantageous condition. Further, as is clear from the data in Table 1, the purification method of the present invention significantly reduces impurities in the starting material.

Although the purification of niobium hydroxide containing impurities has been described above, it is clear that the purification method of the present invention can similarly purify niobium oxide, tantalum hydroxide, and tantalum oxide containing impurities. Although Fe has been exemplified as an impurity, it is clear that Ti, Mn and the like also have a similar removing effect.

[0015]

INDUSTRIAL APPLICABILITY In the purification method of the present invention, it is not necessary to use a solvent such as MIBK or hydrofluoric acid, which has been used in the conventional solvent extraction method, and it is inexpensive and easy to handle and potassium hydroxide is simple. It can be carried out with equipment, so that there are no restrictions on equipment materials, handling, and storage,
It is not necessary to take measures to secure the work environment. Further, the purification method of the present invention can be carried out by using a part of the equipment used in the conventional solvent extraction method as it is.

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Claims (2)

(57) [Claims] 1. Tantalum is obtained by treating tantalum or niobium oxide or hydroxide containing impurities in a potassium hydroxide aqueous solution having a potassium hydroxide concentration of 130 g / l or more and a temperature of 25 ° C. or more under atmospheric pressure for 2 hours or more. Alternatively, the niobium oxide or hydroxide is dissolved as a potassium salt, the produced slurry containing insoluble impurities is filtered to remove impurities, and acid is added to the filtrate to precipitate tantalum or niobium hydroxide. And recovering the precipitate, a method for purifying an oxide or hydroxide of tantalum or niobium. 2. Tantalum is obtained by treating tantalum or niobium oxide or hydroxide containing impurities in a potassium hydroxide aqueous solution having a potassium hydroxide concentration of 200 g / l or more and a temperature of 60 ° C. or more under atmospheric pressure for 2 hours or more. Alternatively, the niobium oxide or hydroxide is dissolved as a potassium salt, the produced slurry containing insoluble impurities is filtered to remove impurities, and acid is added to the filtrate to precipitate tantalum or niobium hydroxide. And recovering the precipitate, a method for purifying an oxide or hydroxide of tantalum or niobium.