AU653674B2

AU653674B2 - A process for isolating tantalum and niobium

Info

Publication number: AU653674B2
Application number: AU33906/93A
Authority: AU
Inventors: Walter Dr. Bludssus; Joachim Dr. Eckert
Original assignee: HC Starck GmbH
Current assignee: HC Starck GmbH
Priority date: 1992-03-06
Filing date: 1993-03-01
Publication date: 1994-10-06
Anticipated expiration: 2013-03-01
Also published as: BR9300739A; CN1041753C; CN1076731A; BE1006385A3; CA2090919C; CA2090919A1; DE4207145C1; AU3390693A; JPH0610074A; ATA19193A; AT398209B

Description

Our Ref: 457126 6 5 3 6 P/eg/011 b 6 7Reg~tion 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT e o Applicant(s): Address for Service: Invention Title: H. C. Starck GmbH Co. KG Im Schleeke 78-91 D-3380 GOSLAR 1

GERMANY

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 A process for isolating tantalum and niobium The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 St/bo/2E-w A process for isolating tantalum and niobium Field and Background of the Invention The present invention relates to a hydrometallurgical process for isolating tantalum and niobium from raw materials which contain tantalum and niobium by treatment with pure hydrofluoric acid or a mixture of hydrofluoric acid and sulphuric acid, followed by solvent extraction of the tantalum and niobium complexes from the treatment solution using methylisobutyl ketone and steam distillation of the organic ketone phase containing tantalum and niobium.

Tantalum and niobium occur together in most natural sources. Different proportions of the two elements, however, characterise the ores and their geological deposits. Niobium is in principle obtained from columbite ore and/or pyrochlore ore from Brazil and Canada and other regions. These ores, however contain only small amounts of tantalum.

Tantalum-rich ores, such as e.g. tantalite, contain correspondingly small amounts of niobium.

To isolate tantalum and niobium, however, it is mainly slags which are produced during the isolation of tin (Thailand, Brazil) which are also used. These tin slags are now regarded as the most important raw material source for the two elements, although they i* 25 only contain small amounts of niobium and tantalum. Also, very variable Ta/Nb ratios are 25 encountered in these tin slags.

0 Normally, the two metals and their compounds are isolated indirectly from raw materials containing very little tantalum and niobium, such as e.g. tin slags, by fusion metallurgical enrichment methods for the two elements. Only the synthetic tantalum/niobium 30 concentrates obtained in this way are available for economic wet chemical processing.

Among these tin slags there are now also those which, like natural columbite, contain tantalum in a very unfavourable Ta/Nb ratio, i.e. they contain small amounts of tantalum but are rich in niobium. The normal hydrometallurgical treatment and separation processes cannot be applied to these, for economic reasons, because these processes 35 require a Ta/Nb ratio of at least 1:3 in the concentrate which is used.

*oo STA 37-Foreign Countries 1 The conventional hydrometallurgical process for isolating tantalum or niobium, disclosed in US Patent 3,117,833, comprises treatment of the tantalum/niobium raw material in mineral acids, preferably hydrofluoric/sulphuric acid mixtures. Tantalum and niobium are thereby dissolved together as fluoro-complexes and subsequently separated first from accompanying elements and then from each other, using a multi-stage solvent extraction with MIBK (methylisobutyl ketone, 2-methyl-pentan one). Here, the fluoroniobates or fluorotantalates are selectively re-extracted in sequence and further processed to give pure tantalum or niobium compounds.

In detail, this takes place by selectively removing the niobium from the organic ketone phase which contains niobium and tantalum, e.g. with dilute sulphuric acid, while tantalum remaining in the organic phase may be re-extracted from that using water.

However, if materials which are rich in niobium but contain very little tantalum are used, then at this point the tantalum is present in very low concentration in the organic ketone phase. This means that there is a very poor volume/time yield, which makes the process uneconomical.

o In addition, US Patent 3,403,983 discloses a process for the preparation of an aqueous solution of niobium and/or tantalum fluoro-complexes from a solution of fluorocomplexes of these metals in a steam-volatile, organic solvent which is virtually 25 immiscible with water, wherein a solution of the fluoro-complexes of these metals in the organic solvent, which is obtained using the known multi-stage extraction of the metals from ores, is subjected to a steam distillation process with quantitative evaporation of the solvent to produce a non-distilled aqueous solution which contains the fluoro-complexes in a higher concentration than was present in the organic solvent.

3 This should mean that the problem of emulsion formation is avoided, the organic solvents are easily recovered and recycled, an aqueous solution of niobium and/or tantalum fluorocomplexes with three- to four-fold higher concentrations than in solution in the organic solvent is obtained and the aqueous product solution is highly suitable for the economic crystallisation of K 2 TaF 7 STA 37-FC -2- This does not apply in particular, therefore, to niobium/tantalum complexes which which contain very little tantalum.

It is the principal object of this invention to provide a process which is superior to those in the prior art and solves the above problems. In particular a process should be suitable Sfor economically isolating tantalum from starting materials which contain very little tantalum and at the same time are rich in niobium, using a wet cheraical treatment and extraction process, without an indirect fusion metallurgical process being required beforehand. In addition, all the niobium should also be isolated.

Summary According to the invention the problems are solved by treating the raw material containing tantalum er," niobium, e.g. tin slags, niobium ores and/or concentrates, with pure hydrofluoric acid or a mixture of hydrofluoric acid and sulphuric acid and extracting the acid solution first with MIBK (methylisobutyl ketone), wherein niobium and tantalum pass into the organic phase together. Normally, the sum of the transition metals, calculated as their oxides, is expressed as "combined oxides" (abbrev.: The niobium is not now selectively re-extracted from the organic phase using mineral acids or water, as is usual, but the ketone phase containing the C.O. is subjected to steam distillation. This measure means that both valuable substances are converted into an S 25 aqueous phase in a highly concentrated form. The tantalum is now selectively extracted from this aqueous phase using fresh ketone (MIBK), while the niobium remains in the aqueous phase.

,This invention thus comprises a hydrometallurgical process for isolating tantalum and niobium from raw materials containing tantalum and niobium by treatment with pure hydrofluoric acid or a mixture of hydrofluoric acid and sulphuric acid, followed by solvent extraction of the tantalum and niobium fluoro-complexes from the treatment solution using methylisobutyl ketone and steam distillation of the organic ketone phase containing tantalum and niobium, wherein the tantalum is selectively extracted from the newly produced aqueous phase with fresh methylisobutyl ketone, while all the niobium 35 remains in the aqueous phase.

STA 37-FC By selecting the ratio between the organic and aqueous phases, the amount of tantalum in the new MIBK phase may be adjusted to the desired concentration. If this organic phase is subjected to a further steam distillation process, there is another increase in the concentration of tantalum in the new aqueous phase. A preferred embodiment of the process according to the invention comprises treating the new organic ketone phase containing tantalum with steam and thereby re-extracting the tantalum. The new concentrated tantalum solution may then be further processed in known ways.

The process according to the invention is advantageously useable for various tantalum/niobium raw materials. It confers particular advantages if there is a Ta:Nb ratio o f <0.2 in the raw materials containing tantalum and niobium. Preferably, the process may be applied to columbite ores and/or tin slags with a Ta:Nb ratio of 1:5 to 1:15.

Detailed Description of Preferred Embodements The invention is explained in more detail in the following by way of example, without this being regarded as a limitation.

STA 37-FC Example A columbite ore with 35% by weight of Nb 2 05 and 4% by weight of Ta205, the remainder being SiO 2 FeO, MnO 2 TiO 2 and other impurities, was treated with strength pure hydrofluoric acid. This produced a solution with 135 g/1 of C.O.

Combined Oxides, Nb20 5 and Ta 2 0 5 and an acidity of 20 N. The Ta:Nb ratio in this starting solution was about 1:9, corresponding to the starting material. This feed solution was passed against an organic phase consisting of methylisobutyl ketone (MIBK) in a counter-stream solvent extraction unit. The raffinate was sufficiently free of valuable material, with 03 g/l of C.O. The ketone phase containing 89 g/1 of C.O. was now washed with a little 12 normal sulphuric acid, in order to remove residual impurities of other elements which had also been extracted. The ketone phase containing niobium and tantalum was sluiced out and subjected to steam distillation. 130 1/h TaNb MIBK were continuously fed to the top of a destillation column whereas 50 1/h steam were fed to the bottom of this column. The MIBK was totally distilled off and 35-40 I/h of a concentrated 2 Niobium- und Tantalum solution remained behind. These elements were present as fluoro-complexes in a concentration ratio of 20 g/1 Ta 2 05 and 180 g/1 Nb20 5 (Ta:Nb Due to the relatively low acidity of the aqueous phase of this steam distillation process the tantalum now was selectively extracted by contacting 40 1/h of this aqueous solution with 51/h of fresh unloaded MIBK while the niobium (180 g/1 Nb 2 0 5 remained in the aqueous p'iase and was worked up separately. The resulting organic phase 25 containing tantalum (with 140 g/1 Ta 2 0 5 was again treated with steam (31 Ta MIBK 11 steam) which totally removed the MIBK from the system and produced the concentrated aqueous solution of tantalum fluorid (with >200 g/1 of Ta20 5 equivalent).

SThis was converted into the endproduct potassium hepta fluorotantalate (1,4 kg) by the addition of KCl in the usual way as described for example in US Patent 3,051,547.

STA 37-FC Comparison example (according to US Patent 3,117,833) The niobium/tantalum solution produced from treatment of the ore used in example 1 was, as in example 1, passed against an organic phase consisting of methylisobutyl ketone (MIBK) in a counter-stream solvent extraction unit. The ketone phase, containing 90 g/1 0 of was now washed with a little 12 normal sulphuric acid, in order to remove residual impurities of other elements which had also been extracted. The niobium was selectively and completely converted into an aqueous phase, in the usual way, by stripping it from the ketone phase containing niobium and tant-um with 2 N sulphuric acid and this was used as a sulphmic acid niobium fluoride solution to isolate niobium hydroxide. The ketone phase, now only containing tantalum, with 7.5 g/1 of Ta 2 05, was freed of ketone by steam distillation and converted into an aqueous phase containing g/1 of Ta20 5 This solution, with the relatively low tantalum content, is not suitable for economic further processing since it either requires too much heat energy for evaporation or leaves behind too much salt-laden waste water, if tantalum hydroxide is produced from it.

S..

S. 0rs £555 5 5* S S STA 37-FC -6-

Claims

1. A hydrometallurgical process for isolating tantalum and niobium from raw materials containing tantalum and niobium by aqueous treatment with pure hydrofluoric acid or a mixture of hydrofluoric acid and sulphuric acid, followed by: solvent extraction of the tantalum and niobium fluoro-complexes from the aqueous treatment solution using methylisobutyl l-:tone and, then, steam distillation of the organic ketone phase which contains tantalum and niobium to produce a new aqueous phase, characterised in that the tantalum is selectively extracted from the new aqueous phase thus produced, using fresh methylisobutyl ketone, while essentially all the niobium remains in the aqueous phase.

2. A process according to claim 1, characterised in that the new organic ketone phase containing tantalum is treated again with steam and the tantalum is thereby re- extracted. 20

3. A process according to claim 2, wherein a Ta/Nb ratio of 50.2 is present in the precursor which contains tantalum and niobium.

4. A process according to claim 1, wherein a Ta/Nb ratio of <0.2 is present in the precursor which contains tantalum and niobium.

5. A process for isolating tantalum and niobium substantially as hereiinbefore described with reference to the examples. DATED this 28th day of July, 1994. H. C. STARCK GMBH CO. KG By Its Patent Attorney DAVIES COLLISON CAVE S STA 37-FC -7- A process for isolating tantalum and niobium Abstract of the Disclosure The present invention relates to a hydrometallurgical process for isolating tantalum and niobium from raw materials containing tantalum and niobium by treatment with pure hydrofluoric acid or a mixture of hydrofluoric acid and sulphuiic acid, followed by solvent extraction of the tantalum and niobium fluoro-complexes from the treatment solution using methylisobutyl ketone (MIBK) and steam distillation of the organic ketone phase containing tantalum and niobium, to produce a new aqueous which is contactable by fresh MIBK to selectively extract tantalum. C C Ce C C C C .C Ce cr *egg, 0 STA 37-Foreign Countries