JPH07252552A - Isolation and separation of tantalum and niobium - Google Patents

Abstract

PURPOSE: To separate and extract Ta and Nb with a high yield and without producing a large amount of byproducts by digesting raw materials containing Ta and Nb with a hydrofluoric acid and treating the formed solution with methylisobutylketone solution extraction process.

CONSTITUTION: Raw materials containing Ta and Nb are treated and digested with a hydrofluoric acid solution thereby producing a solution containing Ta and Nb in the form of their fluoro-complex compounds. After this solution, which contains Ta, Nb and other harmful impurities, is allowed to react with methylisobutylketone(MIBK) in a multistage mixer/precipitation tank apparatus, only Ta and Nb are separated and transferred into MIBK, the MIBK phase is washed with water for transferring Ta and Nb into water phase to separate them from the impurities such as Fe, Mg, Ti contained in raw materials as well as taking out the water solution of Ta, Nb with a high yield. The solution is subjected to an isolation process for isolating Ta compound and Nb compound, respectively in a high yield as raw materials for Ta₂O₅ and Nb₂O₅.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is a cooking using only hydrofluoric acid.
(digestion), separation of two elements from undesired associated elements and mutual separation by solvent extraction of tantalum and niobium fluoro complex compounds from the cooking solution with methyl isobutyl ketone (MIBK), and loaded MIB
It relates to a method for isolating both substances from raw materials containing both tantalum and niobium by washing phase K.

According to US Pat. No. 2,962,372, tantalum and niobium are extracted and separated by digestion with hydrofluoric acid and acidification with sulfuric acid or hydrofluoric acid. In this method, the tantalum and niobium fractions are dissolved together with several accompanying elements and the complex heptafluoride H ₂ TaF ₇ or H ₂ NbF ₇ or H ₂ NbOF ₅
To form. After filtering the insoluble residue (alkaline earth fluoride, rare earth fluoride), hydrofluoric acid containing tantalum and niobium, or hydrofluoric acid / sulfuric acid aqueous solution is used as an organic extractant in a multi-stage mixer / sedimentation tank device. For example, contact with methyl isobutyl ketone (MIBK).

The niobium fluoride and tantalum complexes dissolve in the organic ketone phase and are extracted together, but most impurities and associated elements such as iron, magnesium, titanium, etc. remain in the extracted raffinate. In practice, the process is carried out at a concentration of 150-200 g / l Nb ₂ O ₅ + Ta ₂ O _{5 in} the organic phase. Niobium is re-extracted from this organic phase with water or dilute sulfuric acid. In this case, the aqueous phase absorbs the niobium fluoride complex dissolved in the ketone, sulfuric acid and free hydrofluoric acid, while the tantalum fluoro compound remains dissolved in the organic phase.

The aqueous niobium solution is contacted with an even smaller amount of MIBK in order to remove traces of tantalum that are co-extracted. Hydrated niobium oxide (niobium hydroxide) is precipitated by adding ammonia gas or an aqueous ammonia solution. After re-extracting the tantalum from the organic phase with water or dilute ammonia solution, the tantalum is converted into a hydrated oxide with ammonia or by addition of potassium salt to K ₂ Ta.
It can be precipitated as F ₇ . K ₂ TaF ₇ is the starting material for the production of metallic tantalum.

In the above method, a considerable volume of highly contaminated effluent is produced. These effluents are hydrofluoric acid / sulfuric acid solutions containing metal salts from raffinate and washing acids, and very dilute NH ₄ F and NH ₄ from the precipitation process.
Included with F / (NH ₄ ) SO ₄ . This effluent must be treated. The process produces large amounts of gypsum / fluorspar sludge which must be discarded. Approximately 9 tons of discarded sludge is produced per ton of feed.

Cleaning of the MIBK phase with water or dilute sulfuric acid is known from US Pat. No. 3,117,833. The scrub solution resulting from this process is returned to the raffinate and contaminates the fluoride solution with a wash acid containing a significant amount of sulfuric acid.

German Patent No. 4,021 207 describes the use of hydrofluoric acid alone for the digestion of tantalum and niobium fluorocomplex compounds from the cooking solution by solvent extraction of methylisobutylketone to remove the undesirable 2
Disclosed is a method for separating these elements from a source containing both tantalum and niobium by separating elements and from each other and washing the laden MIBK phase with water or dilute sulfuric acid, MI loaded in that way
The BK phase is first washed separately with 8-16 N dilute sulfuric acid, followed by water and optionally dilute hydrofluoric acid, where the tantalum and niobium remain in the MIBK phase and the contaminated dilute sulfuric acid is extracted. It is separately discharged from and sent to the recovery of hydrofluoric acid.

The basic feature of this method is that tantalum and niobium are extracted from the hydrofluoric acid solution without the addition of a second inorganic acid. The further loaded MIBK phase is first purified with sulfuric acid and finally with water.

When washing with dilute sulfuric acid, it is washed out from the MIBK phase with a negligible amount of niobium.
Mainly co-extracted impurities from cooking solutions, which are sulfate / fluoride-sulfuric acid solutions (sulfuric su).
lphate / fluoride solution)
As a method is discharged separately. This step cannot be omitted because of the high purity of the product required. Then, the niobium fluoride complex dissolved in the ketone was re-used with water.
It is extracted, in which case the tantalum fluoro compound remains in the organic phase. Thereafter, niobium is precipitated as hydrated niobium oxide from the aqueous phase by adding ammonia gas or an aqueous ammonia solution.

After re-extracting the tantalum from the organic phase with water or dilute ammonia solution, the hydrated tantalum oxide can be precipitated or the complex salt K ₂ TaF ₇ can be produced by addition of potassium salt to produce metallic tantalum. Can be produced as a starting material.

The process disclosed in DE-A-4 021 207 also produces a considerable volume of highly contaminated effluent. These effluents were hydrofluoric acid solutions containing metal salts from the raffinate, and fluoride-sulfuric acid solutions from the washing acid, and very dilute N 2 from the precipitation process.
Included with H ₄ F and NH ₄ F / (NH ₄ ) SO ₄ solution. This effluent must be treated. The process produces large amounts of waste sludge, including gypsum and fluoride, which must be discarded. Approximately, about 2,500 kg of H ₂ SO ₄ are needed per ton of raw material used, yielding 4,300 kg of gypsum.

To overcome the above difficulties, it is necessary to avoid the formation of a mixture of sulfuric acid and hydrofluoric acid. This involves first dissolving the raw materials in a pure hydrofluoric acid solution,
Then extract useful materials from pure hydrogen fluoride solution,
It can also be achieved by performing the washing step only with dilute hydrofluoric acid instead of sulfuric acid. However, it is known that using only hydrofluoric acid as the cleaning acid gives unsatisfactory results. Thus, the use of a second inorganic acid, preferably sulfuric acid, has heretofore been absolutely necessary. According to DE-A-4 021 207, this second inorganic acid also plays a role in improving the degree of extraction and thus could not be omitted before.

The object of the present invention is thus to provide a method which does not have the above-mentioned drawbacks of the prior art.

[0014]

SUMMARY OF THE INVENTION These requirements require cooking with hydrofluoric acid alone, the extraction of tantalum and niobium fluoro complex compounds from the cooking solution by methyl isobutyl ketone (MIBK) solvent extraction of two elements from undesired associated elements. Separation and mutual separation, and washing of the loaded MIBK phase, the loaded MIBK phase is washed only with the aqueous phase, and the resulting washing aqueous solution is discharged separately from the extraction method, including both tantalum and niobium This can be achieved by a method of isolating both substances from the raw material. Thus, the use of the second inorganic acid can be omitted.

The low degree of extraction resulting from the absence of the second inorganic acid is compensated by the increased throughput of the organic phase. Furthermore, in contrast to the prior art, the organic phase loaded with tantalum and niobium is not washed with dilute sulfuric acid but only with pure water. During this washing step some of the niobium is re-extracted. This re-extract is discharged from the main stream as an aqueous wash solution along with impurities and small amounts of tantalum.

[0016]

Detailed Description of the Preferred Embodiments In a preferred embodiment of the method, the wash solution is replaced with fresh MIBK and MI.
The BK circuit is contacted with the organic phase containing tantalum returned before the washing step.

The resulting aqueous cleaning solution containing fluoride is preferably processed into an industrially pure niobium oxide product. The solution can be worked up separately using known methods for the isolation of niobium oxide and fluorides or hydrogen fluorides. In this way, technically pure niobium oxide is obtained, which is of sufficient quality to be used, for example, as a raw material for metal alloys or other niobium products of low purity. The proportion of niobium in this partial stream which is re-extracted from the MIBK phase in the acid-free wash stage is between 5 and 5% of the amount of niobium initially fed.
20% and depends on the phase ratio of the aqueous phase to the organic phase.
However, most of the niobium remains in the organic phase and is subjected to niobium / tantalum separation by known methods, such as the method described in German Patent No. 4,021 207, and further processed into pure components. About 95 of Niobium originally supplied
The majority of ~ 80% is thus obtained with a purity of> 99.9%. Some amount of niobium oxide emitted is> 98
It is produced at a temperature of ℃.

The sulfate-free raffinate from the total extraction can be processed by known methods to give fluorspar and / or hydrofluoric acid.

Thus, by omitting sulfuric acid, the method of the present invention reduces previously large quantities of gypsum production. In terms of volume, the amount of sludge dumped is reduced from 9-10 tons per ton of feed to about 7 tons.

The invention is illustrated by the following non-limiting examples.

[0021]

Example 1 A solution containing 90 g / l of Ta ₂ O ₅ and 92 g / l of Nb ₂ O ₅ was added to a conventional tantalum / water solution using a hydrofluoric acid aqueous solution.
Produced by cooking niobium raw material. 90 g / l Ta ₂
A 10 l / h cooking solution containing tantalum / niobium with O ₅ , 92 g / l Nb ₂ O ₅ was contacted with 1.30 l / h MIBK in a multistage mixer / settling tank apparatus. MIB loaded with tantalum and niobium obtained by this method
Phase K was washed countercurrently with 1.25 l / h of water at a flow rate of 10 l / h.

5 l / h of fresh M before draining this aqueous phase
Contacted with IBK. This new organic phase, now loaded with a small amount of tantalum, was combined with the mainstream organic phase from the total extraction.
A washed organic phase of 14.5 l / h and an aqueous phase containing niobium with 1.3 l / h of impurities were produced from all extraction stages.

The oxide produced from the solution gave the following analytical values: a) (T from the unwashed tantalum / niobium / MIBK phase
a, Nb) ₂ O ₅ 136 g / l C.I. O. [Total oxide] (Ta ₂ O ₅ + N
b ₂ O ₅ ) Nb ₂ O ₅ : 50.2% Ta ₂ O ₅ : 49.6% Fe: 160 ppm Ti: 630 ppm Mn: 210 ppm b) Washing tantalum / niobium / from the MIBK phase (Ta,
Nb) ₂ O ₅ 85 g / l C.I. O. _{(Ta 2 O 5 + Nb 2} O 5) Nb 2 O 5: 47.6% Ta 2 O 5: 52.9% Fe: <3ppm Ti: <4ppm Mn: <3ppm c) discharging the aqueous phase tantalum was removed Nb ₂ O _{5 from} 70 g / l NbO ₅ Ta ₂ O ₅ : <0.2% Fe: 0.24% Ti: 0.90% Mn: 0.30% The aqueous phase was initially filled with Nb ₂ It contained 11% of the amount of O ₅ .

Example 2 In a second test, the same unwashed tantalum / niobium / MIBK phase as in Example 1 was washed with a larger amount of water (2 l / h). An organic phase of comparable purity to the organic phase from Example 1 was obtained, in which case the tantalum-free aqueous phase contained 18% of the amount of Nb ₂ O ₅ initially fed.

The main features and aspects of the present invention are as follows.

1. A method of isolating both tantalum and niobium from a feed containing both tantalum and niobium by digestion essentially with hydrofluoric acid, comprising: (a) methyl tantalum and a niobium fluoro complex compound from a cooking solution. Isobutyl ketone (MIBK) solvent extraction to separate the two elements from undesired associated elements and to separate each other, and (b) washing the loaded MIBK phase, the loaded MIBK phase being the aqueous phase only. A method in which the obtained washing aqueous solution is discharged separately from the extraction method.

2. Contacting the wash solution with fresh MIBK and returning the organic phase to the MIBK circuit before the wash step
The method described in the section.

3. 3. The method according to 1 or 2 above, wherein the washing aqueous solution is further processed into a niobium oxide product having industrial purity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Walter Bürtss Germany 38667 Batharzburg Zütlingswiesen 4 (72) Inventor, Joachim Etzkert Germany 38667 Batharzburg Bismarck Schutlerse 25ar

Claims (1)

[Claims] 1. A method for isolating both tantalum and niobium from a feedstock containing both tantalum and niobium by digestion using essentially only hydrofluoric acid, comprising: (a) tantalum and niobium fluoro. Solvent extraction of the complex compound with methyl isobutyl ketone (MIBK) separates the two elements from undesired associated elements and separates them from each other, and (b) cleans the loaded MIBK phase, wherein A method characterized in that the loaded MIBK phase is washed only with an aqueous phase, and the resulting washing aqueous solution is discharged separately from the extraction method.