AU700944B2

AU700944B2 - Process for the isolation and separation of tantalum and niobium

Info

Publication number: AU700944B2
Application number: AU11623/95A
Authority: AU
Inventors: Walter Dr. Bludssus; Joachim Dr. Eckert
Original assignee: HC Starck GmbH
Current assignee: HC Starck GmbH
Priority date: 1994-02-11
Filing date: 1995-02-07
Publication date: 1999-01-14
Anticipated expiration: 2015-02-07
Also published as: AU1162395A; DE4404374C1; JPH07252552A; BR9500498A

Description

Our Ref: 536997 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 4 4 s 4

O

9 4 44 44 Applicant(s): H C Starck GmbH Co KG Im Schleeke 78-91 D-38642 GOSLAR

GERMANY

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Address for Service: Invention Title: Process for the isolation and separation of tantalum and niobium The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 -1- Process for the isolation and separation of tantalum and niobium BACKGROUND OF THE INVENTION The present invention relates to a process for the isolation of tantalum and niobium from raw materials containing both these substances.

According to U.S. Patent 2,962,372, tantalum and niobium S are extracted and separated by digestion with hydrofluoric acid and acidification with sulphuric acid or hydrofluoric acid. The tantalum and niobium fractions, together with a S* few accompanying elements, are dissolved in this process, forming complex heptafluorides H 2 TaF, or H 2 NbF 7 or H 2 NbOF.

After filtering out the insoluble residue (alkaline earth S fluorides, rare earth fluorides) the aqueous, hydrofluoric or hydrofluoric/sulphuric solution containing tantalum and e S niobium is brought into contact with an organic extractant, 0 such as 'for example methyl isobutyl ketone (MIBK) in a multi-stage mixer/settler unit.

The complex niobium and tantalum fluorides dissolve in the organic ketone phase and are extracted together, while the major part of the impurities and accompanying elements such as iron, magnesium, titanium etc. remain in the extraction raffinate. In practice, the process is performed at a concentration of 150 to 200 g/l of Nb 2 05 Ta 2 0 5 in the organic phase. The niobium is re-extracted from this organic phase with water or dilute sulphuric acid. The aqueous phase here absorbs the complex niobium fluorides, sulphuric acid and free hydrofluoric acid dissolved in the ketone, whereas the tantalum fluoro compounds remain dissolved in the organic phase.

Vt I I I I ed

II

4O 4 15 In order to remove any co-extracted traces of tantalum, the aqueous niobium solution is brought into contact with a further small quantity of MIBK. Hydrated niobium oxide (niobium hydroxide) is precipitated by the addition of gaseous ammonia or an aqueous ammonia solution. After reextraction of the tantalum from the organic phase with water or dilute ammonia solution, tantalum may be precipitated as the hydrated oxide with ammonia or as

K

2 TaF 7 by the addition of potassium salts. K 2 TaF 7 is a starting material for the production of metallic tantalum.

Considerable volumes of highly contaminated effluents are generated in the process described. These effluents include hydrofluoric/sulphuric solutions containing metal salts from the raffinate and washing acid, together with highly dilute NH 4 F and NH 4

F/(NH

4 2 S0 4 solutions from the precipitation processes. This effluent must be treated.

Treatment produces large quantities of gypsum/fluorite sludges, which must be disposed of. In approximate terms, approximately 9 to 10 tons of sludge for dumping is produced for each ton of feed material.

It is known from U.S. Patent 3,117,833 to wash the MIBK phase with water or dilute sulphuric acid. The scrub solution arising from this process is returned to the raffinate, so contaminating the fluoride solution with the washing acid, which contains significant quantities of sulphuric acid.

STA 57-FC

I--

German Patent 4 021 207 discloses a process for the isolation of tantalum and niobium from raw materials containing both these substances by digestion with hydrofluoric acid alone, separation of the two elements from unwanted accompanying elements and separation from each other by methyl isobutyl ketone (MIBK) solvent extraction of the tantalum and niobium fluoro complex compounds from the digestion solutions and washing the laden MIBK phase with water or dilute sulphuric acid, in which the laden MIBK phase is first separately washed with dilute 8-16 N sulphuric acid and then with water and optionally dilute hydrofluoric acid, wherein tantalum and niobium remain in the MIBK phase, the contaminated dilute sulphuric acid is separately discharged from the extraction S 15 process and sent for hydrofluoric acid recovery.

e* *0 An essential feature of this process is that tantalum and niobium are extracted from the hydrofluoric solution without adding a second mineral acid. Moreover, the laden MIBK phase is initially purified with sulphuric acid and 20 then finally with water.

On washing with dilute sulphuric acid, it is principally the impurities co-extracted from the digestion solution which are washed out of the MIBK phase, together with only negligible quantities of niobium, and are separately discharged from the process as a sulphuric sulphate/fluoride solution. Due to the requirement for elevated purity of the product, this stage is indispensable. The complex niobium fluoride dissolved in the ketone is then re-extracted with water, wherein the tantalum fluoro compounds, however, remain in the organic phase. The niobium is subsequently precipitated as pure hydrated niobium oxide from the aqueous phase by the addition of gaseous or aqueous ammonia.

STA 57-FC 3 1 N After re-extraction of the tantalum from the organic phase with water or dilute ammonia solution, either hydrated tantalum oxide may be precipitated or the complex salt

K

2 TaF 7 may be produced as a starting material for the production of metallic tantalum by the addition of potassium salts.

Considerable volumes of highly contaminated effluent are still produced in the process disclosed in German Patent 4 021 207. These effluents include hydrofluoric solutions containing metal salts from the raffinate and sulphuric fluoride solutions from the washing acid, together with highly dilute NH 4 F and NH 4

F/(NH

4 2

SO

4 solutions from the precipitation processes. This effluent '.must be treated. Treatment produces large quantities of *0 15 waste sludge containing gypsum and fluorite which must be disposed of. In approximate terms, some 2,500 kg of H 2

SO

4 are required for each ton of raw material used, giving rise to 4,300 kg of gypsum.

In order to overcome the stated difficulties, it is S: 20 necessary to avoid forming a mixt of sulphuric acid and hydrofluoric acid. This may be achieved by initially 0 dissolving the raw materials in pure aqueous hydrofluoric acid, then extracting the valuable materials from purely hydrofluoric solutions and also performing the washing stages only with dilute hydrofluoric acid instead of sulphuric acid. However, it is known that using hydrofluoric acid alone as the washing acid gives unsatisfactory results. The use of a second mineral acid, preferably sulphuric acid, has thus so far been absolutely necessary. According to German Patent 4 021 207, this second mineral acid is also responsible for increasing the degree of extraction and was thus previously deemed indispensable.

STA 57-FC 4 BB8~ba~F-asoaa~i~eaDar~- S29/10/98 The object of the present invention is thus to provide a process which does not suffer the disadvantages of the described prior art.

5 SUMMARY OF THE INVENTION These requirements are achieved by a process for the isolation of tantalum and niobium from raw material containing both, tantalum and niobium, and unwanted accompanying elements by I 10 a) digestion of the raw material with hydrofluoric acid alone to produce a digestion solution containing fluoro complexes of tantalum, niobium and accompanying elements, and b) separation of tantalum and niobium from the accompanying elements by 5 methyl isobutyl ketone (MIBK) solvent extraction of the tantalum and niobium 15 9 fluoro complexes from the digestion solution, and c) washing the MIBK phase with water, thereby removing residual accompanying elements and part of the niobium and tantalum from the MIBK phase, and d) bringing the aqueous washing solution into contact with fresh MIBK to recover tantalum from the aqueous washing solution, and e) returning the MIBK phase from step d) to before the washing step and f) processing the aqueous washing solution to technically pure niobium oxide product It is thus possible to dispense with the use of a second mineral acid.

1z.

N 9 rr -29/10/98 rr ,a r a r a a4 a a a r a a sc rr r I( O *abO o

I

t ~ro r t I; 1. a if rrpli a

I

*QI

II a r r r r* r The lower degree of extraction resulting from not using the second mineral acid is compensated for by increasing the throughput of the organic phase. Furthermore, in contrast with the prior art, the organic phase laden with tantalum and niobium is not washed with dilute sulphuric acid, but exclusively with pure water. A portion of the niobium is re-extracted during 'this washing stage. This re-extract, together with the impurities and a little tantalum is 10 discharged from the main stream as an aqueous washing solution.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In a preferred embodiment of the process, the aqueous washing solution is brought into contact with fresh MIBK and the organic phase containing tantalum returned to the MIBK circuit before the washing stage.

I T -1 I _Ww The aqueous washing solution containing fluoride which arises is preferably processed into a technically pure niobium oxide product. The solution may be separately worked up using known processes for the isolation of niobium oxide and fluorite or hydrogen fluoride. In this manner, technically pure niobium oxide is obtained, which is of sufficient quality for use as a precursor, for example for metal alloys or for other niobium products having low purity requirements. The proportion of niobium in this partial stream re-extracted in the acid-free washing stage from the MIBK phase is between 5 and 20% of the initially fed quantity of niobium, depending upon the phase ratio of the aqueous to the organic phase. The major part of the niobium, however, remains in the organic phase 15 and is subjected in a known manner, as for example described in German Patent 4 021 207, to the niobium/tantalum separation end further processed to pure components.

The major part, approximately 95 to 80% of the initially fed quantity of niobium, is thus obtained at a purity of 99.9%. The discharged partial amount of niobium oxide is produced at a purJ.y of 98%.

The sulphate-free raffinate from the total extraction may be processed in a known manner to yield fluorite and/or hydrofluoric acid.

By dispensing with sulphuric acid, the process according to the invention thus brings about a reduction in the previously large quantities of gypsum produced. In quantity terms, the amount of sludge for dumping is reduced from 9 o 10 tons to approximately 7 tons per ton of feed material.

The invention is illustrated with the following nonlimiting examples.

STA 57-FC 6 2

N.-

Example 1 Solutions containing 90 g/l of Ta20O and 92 g/l of were produced by digestion of a customary tantalum/niobium raw material with aqueous hydrofluoric acid. 10 1/h of a digestion solution containing tantalum/niobium with 90 g/1 of Ta 2 0 5 92 g/l of Nb 2 0 5 were brought into contact with 1.30 1/h of MIBK in a multi-stage mixer/settler unit. The MIBK phase laden with tantalum and niobium obtained in this manner was washed countercurrently at a flow rate of 10 1/h with 1.25 1/h of water.

99 9 15 940,49 4.04 0o Before discharge, this aqueous phase was brought into contact with 5 1/h of fresh MIBK. This new organic phase, now laden with a little tantalum, was combined with the main stream of the organic phase from the total extraction.

14.5 1/h of washed organic phase and 1.3 1/h of an aqueous solution containing niobium with the impurities from the total extraction stage were produced.

9 09 4 0* 20 994 Oxides produced from the solutions analyses: a) (Ta,Nb) 2 0 5 from the unwashed phase: 136 g/l C.O. [combined oxides] 50.2% Ta 2 Os: 49.6% Fe: 160 ppm Ti: 630 ppm Mn: 210 ppm yielded the following tantalum/niobium/MIBK (Ta 2 0 5 Nb205) b) (Ta,Nb 2 05 from the washed tantalum/niobium/MIBK phase: g/l C.O. (Ta 2 0 Nb20 Nb205: 47.6% Ta 2 0s: 52.9% STA 57-FC 7 Lk~--~Bf~B~C *8~nrrmarrssrr~ rsaa3L llhl~ -~isp Fe: 3 ppm Ti: 4 ppm Mn: 3 ppm *c *0 0c 0 15 0 0 0*0 0 0000 4 4, 0* C 0* c) Nb20 s from the discharged aqueous phase from which tantalum has been eliminated: g/l NbOs 5 0.2% Fe: 0.24% Ti: 0.90% Mn: 0.30% The aqueous phase contained 11% of the initially charged quantity of Example 2 In a second test, the same unwashed tantalum/niobium/MIBK phase as in example 1 was washed with a much larger quantity of water (2 1/h) An organic phase of purity comparable with that from example 1 was obtained, wherein, however, the aqueous, tantalum-free phase contained 18% of the initially fed quantity of GTA 57-FC 8

Claims

1. Process for the isolation of tantalum and niobium from raw material contain- ing both, tantalum and niobium, and unwanted accompanying elements by a) digestion of the raw material with hydrofluoric acid alone to produce a digestion solution containing fluoro complexes of tantalum, niobium and accompanying elements, and b) separation of tantalum and niobium from the accompanying elements by 10 methyl isojutyl ketone (M!IBK) solvent extraction of the tantalum and niobium fluoro complexes from the digestion solution, and c) washing the MIBK phase with water, thereby removing residual accompany- ing elements and part of the niobium and tantalum from the MIBK phase, and d) bringing the aqueous washing solution into contact with fresh MIBK to recover tantalum from the aqueous washing solution, and e) returning the MIBK phase from step d) to before the washing step and f) processing the aqueous washing solution to technically pure niobium oxide product.

2. A process for the production of tantalum and niobium substantially as hereinbefore described with reference to the examples. DATED this 29th day of October, 1998. H C STARK CO. KG By Its Patent Attorneys DAVIES COLLISON CAVE CI P 1 St/m-612PE Process for the isolation and separation of tantalum and I niobium Abstract ou 0 99 0 0 0c oo 9 09 0 0 0 9- 9 09 o 00 0 000 Process for the isolation of tantalum and niobium from raw materials containing both thes. substances by digestion with hydrofluoric acid alone, separation of the two elements from unwanted accompanying elements and separation from each other by methyl isobutyl ketone (MIBK) solvent extraction of the tantalum and niobium fluoro complex compounds from the digestion solutions and washing the loaden MIBK phase. STA 57-FC