AU620148B2

AU620148B2 - Improved process for obtaining impurity-free compounds of ta and/or nb from materials containing these metals

Info

Publication number: AU620148B2
Application number: AU41827/89A
Authority: AU
Inventors: Michele Menier; Christian Polak; Michele Prevost
Original assignee: Institut National Recherche Chimique Appliquee
Current assignee: Extramet SA; Institut National Recherche Chimique Appliquee
Priority date: 1988-09-06
Filing date: 1989-08-04
Publication date: 1992-02-13
Anticipated expiration: 2009-08-04
Also published as: KR900702063A; ES2016728A6; FR2636939A1; WO1990002823A1; BR8907079A; EP0386205B1; PT91504A; PT91504B; AU4182789A; EP0386205A1; JPH03502116A; FR2636939B1

Description

P AE0/49 62'0 t481DAE0/49 CT' AOJP DATE 10/05/90 APPLN. ID 41827 89 PCT NUMBER PCT/FR89/00410 DEMANDE INTERNATIONALE PUBLIEE EN VERTU DU TRAITE DE COOPERATION EN MATIERE DE BREVETS (PCT) (51) Classification Internationale des brevets 5 (11) Numnro de publication Internationale: WVO 90/02823 C22G 35/4 /0 OG3/00 A (43) Date de publication internationale: 22 mars 1990 (22.03.90) (21) Numniro de In demnande Internationale: PCT/FR89/00410 (74) Mandataire: RJNUY, SANTARELLI; 14, avenue de la Grande-Arm~e, F-75017 Paris (FR).

(22) Date de d~p~t international: 4 aodt 1989 (04.08.89) (81) Etats disign~s: AT (brevet europ~en), AU, BE (brevet euro- Donn~es relatives i la priorit6: r"en), BR, CH (brevet europ~en), DE (brevet europ~en),' europ~en), JP, KR, LU (brevet europ~en), NL (brevet 88/11 43 6sept mbre1988(06.0 .88) FIR R (b eveteurop en), E (brevet europ en), S.b ev (71) D~posants (pour tous les Etats d~signks sauf US): INSTITUT erpe) E(rvterpe)

S

NATIONAL DE RECHERCHE CITQUE APPLI- QUEE [FR/FR]; 18 bis, boulevard de la Bastille, F- Publike 75012 Paris (FRP). EXTRAMET [FR/FR]; Zone Indus- Avec rapport de recherchze internationale.

trielle de Cranves-Sah-s, B.P. 23, F-7438,1 Bonne (FR).

(72) Inventeurs et Inventeurs/Diposants (US seulement) POLAK, Christian [FR/FR]; Immeuble les Pitons, 37, route de Gen~ve, F- 74100 Ambilly MENJER, Mich~Ie [FR/FR]; 7/9, rue Baulant, F-75012 Paris PREVOST, Michle [FR/FR]; 15, rue J.-Ph.-Rameau, F-91440 Bures-sur- Yvette (FR).

(54) Title: IMPROVED PROCESS FOR OBTAINING IMPURITY-FREE COMPOUNDS OF Ta AND/OR Nb FROM MA- TERIALS CONTAINING THESE METALS (54)Titre: PROCEDE PERFECTIONNE D'OBTENTION DE COMPOSES DE Ta ET(OU) Nb EXEMPTS D'IMPURETES A PARTIR DE MATERTAUX CONTENANT CES METAUX (57) Abstract The process comprises the following steps: leaching with fluorosilicic acid with a minimal H 2 ,SiF 6 concentration of to 40% and greater to which a strong mineral acid, either HCI or H 2 S0 4 may be added; separation of Nb and/or Ta from the aqueous acid medium by liquid-liquid extraction using a suitable organic extractant; recovery of the niobiumn and/or tantalum from the organic phases by re-extraction in aqueous phase followed by precipitation by a base, and subsequent calcination; purification of the tantalum and/or niobiumn compounds to remove other undesirable elements, in particular silica, by carbochlorination.

(57) Abr Ce proc~d6 est caract~ris6 en ce qu'il comporte les 6tapes suivantes: lixiviation ,i lacide fluosilicique de concentration minimum de H 2 SiF 6 de pouvant allerjusqu'A 40% et plus, acide additionn6 ou non d'un acide mineral fort choisi parmi H-CI ou H- 2 S0 4 s~paracion du milieu aqueux acide de Nb et/ou Ta par extraction liquide-liquide, en faisant appel d~ un extractant organique appropri6; r~cup~ration du niobium et/ou du tantale des phases organiques I ir d~sextraction en phase aqueuse suivie d'une precipitation par une base, elle-m~me suivie d'une operation de calcination; purification des composes de tantale et/ou de niobiumn pour les d~barrasser d'autres 616ments ind~sirables, en particulier de silicc, par carboctiloration.

-1 Improved process for obtaining impurity-free compounds of Ta and (or) Nb from materials containing these metals The present invention relates to a process for obtaining compounds of Nb and (or) Ta free from mineral impurities from materials containing one or other of these metals or both of them.

These materials can be minerals belonging to the family of tantalite, columbite, microlite, pyrochlore or others or slag from tin ovens.

Until the sixties, the process known by the name "Marignac process" was the only industrial means of separation of niobium and tantalum using fractional crystallizations of double potassium salts, the niobium complex formed under these conditions being the least soluble.

This'procedure was supplanted at an industrial level by extraction techniques using a solvent after an acid leaching of the ore.

The acid mainly used for the leaching is hydrofluoric acid used either alone, or mixed with sulphuric acid; in addition co its effectiveness in the leaching process, the latter has specific properties which allow the treatment of ores rich in calcium (formation of insoluble calcium sulphate: Patent EP 0,041,459).

The separation phase of Nb and (or) Ta by extraction with a solvent is then carried out with concentrated fluosulphuric acid solutions. Among the known extractants of niobium and tantalum there can be cited methylisobutylketone (MIBK), cyclohexanone, tributylphosphate (TBP), amides of dialkylacetamide type or quaternary ammonium salts.

In spite of the useful performances obtained, a leaching carried out with hot concentrated HF shows a few disadvantages with regard to equipment, costs, and safety.

Therefore the tendency has been to diminish the consumption of HF; thus a pre-treatment of slag from tin ovens in an hydrofluoric or fluosilicic (H 2 SiFg) acid medium enables certain impurities to be made insoluble (United K States of America Patent 3,972,710). This process covers a 'AiLV B; ^w ,W

T

0 2 pre-treatment method, the function of which is the conversion of impurities into insoluble fluorides at the time of the second stage of leaching by HF, and therefore leads to a lowering of the ccnsumption of this acid. It is to be noted that the niobium and tantalum are given as insoluble to the fluosilicic leaching in the pre-treatment.

In the Patent (DE 3,441,582) H 2 SiF 6 combined with HF is recommended for the leaching on Nb and Ta concentrates containing alkali metals as impurities, the fluosilicic acid facilitates the separation of these in the form of insoluble alkaline fluosilicates, which has the effect of improving the solubilization of Nb and Ta. But, also in this case, it is the HF which is the solubilization agent for types of Nb and Ta.

To compensate for the disadvantages connected to the presence of HF it is also recommended that a controlled source of fluoride ions of fluoride complexes is used by the addition, in an acid medium (preferably HC1), of a salt that is normally insoluble in the considered medium (preferably CaF 2 (Patent Fr 2,316,343).

Moreover it is known that in certain cases, and for certain minerals, fluosilicic acid can be used to facilitate the leaching (WO 84/ 04759). However, nowhere is it suggested to use this acid for materials containing a non negligible proportion of Nb and Ta and with a view to the recovery of these metals reputed to be insoluble in H 2 SiF 6 In any case, it was never envisaged that in practice this latter acid would be used by itself for the leaching of niobium and tantalum minerals or concentrates, certain processes only envisaging the use of H 2 SiF 6 for lowering the consumption of HF which remains the principal agent for the Sleaching of niobium and tantalum.

Now the present invention proposes not only the improvement of leaching but also the recovery and purification of Nb and Ta starting with materials containing a non negligible proportion of these elements. More especially the invention aims at a process that avoids "iA resorting to HF. By not using HF, this p7:ocess avoids the 'T 1 3 harmful effects connected with this acid, and increases the separation and recovery yields of these metals.

The process of the invention envisages the use of fluosilicic acid for the leaching, the fluosilicic acid is advantageously used in an aqueous solution such as is commercially available and of a concentration that can be up to 40% or more of H 2 SiF 6 Nevertheless, the addition of a strong acid such as HCl, H 2 SO4, while increasing the acidity of the medium makes it possible, in certain cases, to appreciably increase the solubility of niobium and tantalum in the leaching solution.

According to one characteristic, the leaching temperature is between ambient temperature and the boiling point of the leaching medium, at the pressure under which the leaching takes place, preferably between 60 and 80 0

C,

when the leaching takes place under atmospheric pressure.

By proceeding in this way for the leaching, the Applicants have noticed in an unexpected fashion that not only is the use of hydrofluoric acid and its disadvantages avoided, but that the operation can take place with much weaker acids.

After the leaching stage, the process of the invention anticipates the separation and recovery of the dissolved niobium and/or tantalum compounds.

As for the separation, this will be performed on the fluosilicic leaching solution and more particularly by liquid-liquid extraction.

The choice of extractants among those known for niobium and tantalum will be orientated towards those most suitable A 30 to the metal sought and to the degree purity aimed for: advantageously MIBK or TBP will be chosen for the selective separation of tantalum; TBP will preferably be chosen for the co-extraction of the two metals and their later separation.

The extractant will be used pure or diluted as the case may be, in the latter case the diluent then will be the following, aliphatic or aromatic hydrocarbons such as those usually used for extraction by solvent. If appropriate,

S

-4 according to the standard process for liquid-liquid extraction, an additive will be included in the extractantdiluent mixture to suppress any possible third phase. As an example of such additives heavy alcohols such as decanol may be mentioned.

The recovery of niobium and tantalum from th organic phases is performed according to standard procedures for liquid-liquid extraction, by re-extraction into the aqueous phase followed by precipitation by a base, itself followed by a calcination operation.

The Ta and Nb compounds, generally obtained in the form of oxides, can cc1It in a small amount of silica which is detrimental to their purity; the third stage of the process of the invention therefore proposes to separate the tantalum and (or) the niobium from the silica.

This third stage brings together the hydrometallurgic advantages of the preceding stages by using pyrometallurgy (higher kinetics, significant production).

In accordance with the invention, a carbochlorination of the tantalum or of the niobium resulting from the extraction stage is invoked as the final purification stage of these compounds.

The carbochlorination has often been retained only in terms of a pre-concentration of material of low content with a view to a later hydrometallurgic treatment.

The separation of the Ta and Nb is sometimes effected by distillation of their mixtures in the form of chlorides obtained either by carbochlorination of the corresponding oxidised types, or by chlorination of impure metals. The techniques of chlorination or carbochlorination are not used for the purification of Nb or Ta compounds that are already separated.

Therefore the applied carbochlorination according to the invention consists of a simultaneous supply of carbon and chlorine to a bath of molten salts containing the items to be chlorinated. This supply can be achieved either by Ssimultaneously injecting chlorine and powdered carbon, or by A using chlorinated organic compounds such as CC1 4 it is also 1

Y~C~-

possible simultaneously to inject a hydrocarbon and chlorine. The molten salt constitutes an excellent reaction 4 medium with extremely useful physical chemical properties namely good thermal conductivity, significant calorific capacity, low viscosity, low vapour pressure. The reaction leads principally to the volatile chlorides of Ta (or Nb) and Si, as well as to carbon monoxide.

The chlorides of tantalum or niobium and of silicon thus obtained are finally separated due to the difference in their boiling temperatures, by successive condensations 239 0 C, NbCl 5 249 0 C, SiCl 4 57.4 0

C).

The employment of the three stages, leaching, extraction, carbochlorination are wit!in the standard procedures of hydrometallurgy and pyrometallurgy.

Most particularly the increase in separation and/or recovery yields will be observed due inter alia to the use of the leaching agent according to the invention. The scope and significance of the invention will emerge from the examples given hereafter with reference to the accompanying Figures 1 to 3.

EXAMPLES.

Example 1.

A mixture of tin slag from Thailand (Ta 2 0 5 13.6%, Nb 2 0 5 ground up beforehand (granulometry 25 to 50 p) and 31% fluosilicic acid (20 g of slag/litre) is agitated at Sa temperature of 60 70 0 C. After 30 minutes, 50% of the tantalum and niobium have passed into solution; after 4 hours the total solubilization is greater than 80% for Nb and Ta.

Example 2.

Using the same raw materials leaching is achieved at 60-70 0 C under magnetic agitation (approximately 700 revs/mn) for 4-5 hours, with 50 g/l of slag.

Nb and Ta solubilized: about 60% and about Example 3.

Using the same conditions as in Example 2 with 50 g/l AL/ of slag and an acid mixture 28% H 2 SiF 6 4N H 2

SO

4 the

T

6 following result is obtained: Nb and Ta solubilized 80% and Example 4.

The leaching of Ta and Nb is achieved starting with a tantalite mineral (Ta205 65%, Nb205 29.5% granulometry to 100 1 100 g of solid/1. acid) either with H 2 SiF 6 ,lone (34% industrial acid) or with a H 2 SiF 6 29% 5N H 2

SO

4 mixture. With the temperature, agitation and time conditions of Example 2, the total amounts of Nb and Ta solubilized are then:

H

2 SiF 6 about 40 (Nb) and about 26 (Ta)

H

2 SiF 6

H

2

SO

4 about 65 (Nb) and about 50 (Ta) Example The extraction of Nb and Ta is carried out at ambient temperature, 15 minutes agitation. The aqueous phases of Nb and Ta in H 2 SiF 6 stem directly from the leaching of the slag or are doped by addition of NbCl 5 and TaCl 5 the concentrations are respectively from 1 to 10 g/l and from 2 to 20 g/1 of Nb and Ta.

The solvent phase is 50% TBP in "Solvesso 150" (prebalanced with a fluosilicic acid phase). The concentration of H 2 SiF 6 varies from 5 to 31% and the ratio Va/Vo 1 (Va aqueous phase volume and Vo organic phase volume). The extraction curves are recorded in Figure 1.

An examination of these curves shows that Ta is extracted quantitatively across the whole acidity range and that the extraction of Nb rises with acidity

H

2 SiF 6 5% Ta extracted 98.5 Nb extracted about 2 t H 2 SiF 6 31% Ta extracted 98 Nb extracted about j 30 Example 6.

The extraction of Ta and Nb is achieved with the operating conditions of Example 5 starting with aqueous fluosilicic solutions (H 2 SiF 6 or 28% H 2 SiF 6 2N H 2 S0 4 stemming from the leaching of slag (Nb Ta 3 to 6 g/l) or of tantalite (Ta Nb 20,to 30 The extraction curves are recorded in Figure 2: they show that at a weak concentration of TBP selective extraction conditions for Ta /Att can be established whereas at strong concentrations there is MS S 4Tn

_I

I:?

i

I

i! t 7 co-extraction of the two metals (extraction totals greater than 80% with contact in the same conditions).

Example 7.

The conditions of temperature, time, and volume of phases are the same as in Example 5. The concentrations of Nb and Ta in the 32% H 2 SiF 6 2N H 2

SO

4 mixture are 7.6 g/l and 9.5 g/l (solution stemming from the leaching of tantalite), The use of different concentrations of TBP allows the successive recovery of tantalum then niobium. Thus, a first stage with a solvent consisting of 10% TBP with 4% decanol in the diluent allows the extraction of 97.5% of the tantalum the use of 50% TBP (same diluent) to treat the aqueous phase originating from Stage 1 allows the extraction of virtually all the remaining Nb and Ta.

Example 8.

This Example is given ai a comparison with reference to the curves in Figure 3. It was effected to compare the extraction totals of Nb and Ta with TBP (50% in "Solvesso 150" starting from the media HF H 2 S0 4 (Nb Ta 40 g/1) or H 2 SiF 6 (Nb Ta 3 to 30 Examination of the curves, obtained under the operating conditions of Example show that: the extraction of tantalum is quantitative with the two types of aqueous solutions in the acidity range investigated:

.H

2 SiF 6 from 5 to 31% i.e. 0.75 to 5.5N (curve 3a), .HF H 2

SO

4 from 0.5 N HF 2N H 2 S0 4 to 5N HF 9N H 2

SO

4 (curve 3b) 30 the extraction of Nb is negligible at weak acidity and it increases with this. If with fluo/sulphuric mixtures (curve 3c), strong acidities are required, such as 5N HF 9N H 2

SO

4 to attain an extraction total of 80%, with fluosilicic acid, an acidity of 5.5N is sufficient (curve 3d) to obtain the same result.

Example 9.

A fluosilicic solution originating from the leaching of p slag (Nb 2 g/l, Ta 2 g/l) is agitated volume for volume with >7 jT 0 'r' ,s J: 8 pure MIBK for 15 minutes at ambient temperature. In the range of acidity investigated (5 to 31% H 2 SiF 6 the extraction of Ta is practically quantitative and that of Nb is equal to or less than Example 450 g of Ta 2 0 5 obtained by precipitation of the hydroxide followed by calcination and containing 0.6% of SiO 2 is mixed with 35 g of carbon. After agglomeration into balls of about 1 cm in size (pellets), the product is chlorinated at 850 0 C using a stream of chlorine gas and 650 g of TaCl 5 is obtained containing 1.1% SiCL 4 Using a distillation column 610 g of TaCl 5 is recovered containing 20 ppm of SiCl 4 which is returned to the beginning of the manufacturing process.

It goes without saying that the present invention is only described purely by way of explanation and is in no way limiting.

11 Y;

Claims

1. Improved process for obtaining impurity-free compounds of niobium and/or tantalum from various materials containing one or other of these metals or both of them, the process being characterised in that it comprises the following stages of operation: leaching with a fluosilicic acid with a concentration of H 2 SIF 6 of 10% or more, which acid has added to it or not added to it a strong mineral acid chosen from HC1 or H 2 S0 4 separation of the acid aqueous medium of Nb and/or Ta by liquid-liquid extraction, using an appropriate organic extractant; recovery of niobium and/or tantalum from the organic phases by re-extraction into the aqueous phase followed by precipitation by a base, in turn followed by a calcination operation; purification of the tantalum and/or niobium to eliminate other Sundesirable elements, in particular silica, by carbochlorination.

2. The process of claim 1 wherein the concentration of fluosillcic acid in step has a concentration of H 2 SIF 6 of between 10% and

3. Process according to claim 1 or characterised in that the leaching temperature in stage is between ambient temperature and the boiling point of the leaching mixture at the pressure under which this is operating, preferably between 60°C and 80 0 C when this leaching is carried out under atmospheric pressure.

4. Process according to claim 1, 2 or 3 characterised in that the organic extractant is chosen from the following: methylbutylketone (MIBK), cyclohexanone, triutylphosphate (TBP), amides of dialkylacetamide type or quaternary ammonium salts. Process according to any one of claims 1 to 4, characterised in that the carbochlorination in stage is achieved using a supply of chlorine or chlorinated organic compounds in a bath of molten salts containing the items to be chlorinated; the carbon is supplied, if necessary, by the injection of graphite or powdered activated charcoal or a S i STA/1599w 4. TA 10 hydrocarbon, the reaction leading to the volatile chlorides of Ta or Nb, to chlorinated impurities and also to carbon monoxide. i I I;~ ,j