Method for extracting a refractory metal from an ore, a concentrate or a waste product

Abstract

The present invention relates to a method for extracting a refractory metal selected from Nb, Ta, Mo, W and V, from a solid material comprising the refractory metal in an oxidised form, the method using a layered double hydroxide, and the use of a layered double hydroxide for extracting or purifying a refractory metal selected from Nb, Ta, Mo, W and V.

Claims

1. A method for extracting a refractory metal M selected from Nb, Ta, Mo, W, V, and a mixture of at least two of said refractory metals, from a solid material comprising said refractory metal in an oxidized form, wherein said method comprises at least the following steps: i) a step of contacting said solid material with a first aqueous composition comprising a first layered double hydroxide which is insoluble in said first aqueous composition, said first layered double hydroxide containing interlayer anions A1n−, n being a positive integer, to form polyoxometallates of said refractory metal which are soluble in said first aqueous composition, said polyoxometallates having a negative charge q− such that q is a positive integer and q>n, ii) a first step of ion exchange in said first aqueous composition of said interlayer anions An—with said polyoxometallates from step i), to form a second layered double hydroxide which is insoluble in said first aqueous composition, and iii) a second step of ion exchange of said polyoxometallates with anions A2p− in a second aqueous composition comprising said anions A2p−, p being a positive integer, to form monomeric species of said refractory metal which are soluble in said second aqueous composition, said monomeric species having a negative charge m- such that m is a positive integer and m≤p.

2. The method as claimed in claim 1, wherein the solid material is an ore, a concentrate, or a ground material resulting from waste electrical or electronic equipment.

3. The method as claimed in claim 1, wherein the solid material is a material in the form of particles having an average size of less than 20 μm.

4. The method as claimed in claim 1, wherein the first layered double hydroxide is a material in the form of particles having an average size of less than 20 μm.

5. The method as claimed in claim 1, wherein the first aqueous composition has a pH selected in a range of from 3.5 to 12.5.

6. The method as claimed in claim 1, wherein the second aqueous composition has a pH selected in a range of from 7 to 11.

7. The method as claimed in claim 1, wherein the first layered double hydroxide is selected from layered double hydroxides conforming to the formula (I) below:
[M′II1-xM″IIIx(OH)2]x+A1n-x/n.sH2O, in which: M′II and M″III represent respectively divalent and trivalent metal cations, A1 is an n-valent interlayer anion selected from monovalent and divalent anions and selected from organic and inorganic anions, x, s, and n are positive numbers, x corresponds to the molar fraction of M″III/(M′II+M″III), and 0<x<1, M′II is selected from Ca2+, Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, and Zn2+, and M″III is selected from Al3+, Mn3+, Fe3+, Co3+, and Cr3+.

8. The method as claimed in claim 1, wherein said method further comprises, between steps ii) and iii), a step ii1) of solid/liquid separation to recover the second layered double hydroxide in the form of a solid.

9. The method as claimed in claim 1, characterized in that it wherein said method further comprises, after step iii), a step iv) of solid/liquid separation to recover the monomeric species of said refractory metal in solution.

10. The method as claimed in claim 9, wherein said method further comprises, after step iv), a step v) of precipitation of the refractory metal in the form of an oxide from the monomeric species of said refractory metal in solution.

11. The method as claimed in claim, wherein the mass ratio of the mass of said solid material to the mass of the first layered double hydroxide in step i) is from 1 to 100.

12. The method as claimed in claim 1, wherein the refractory metal is selected from Nb, Ta, and a mixture thereof, and in that step i) comprises the following substeps: ia) an alkaline treatment of said solid material at a temperature of less than or equal to 550° C., and ib) the mixing of the treated material from substep ia) with the first layered double hydroxide in the first aqueous composition, said first aqueous composition having a pH selected in a range of from 10 to 12.5.

13. The method as claimed in claim 1, wherein the refractory metal is selected from Nb, Ta, and a mixture thereof, and in that the second aqueous composition further comprises at least one complexing agent.

14. The method as claimed in claim 1, wherein the refractory metal is selected from W, Mo, V, and a mixture of at least two of said metals, and in that the first aqueous composition further comprises a compound capable of forming heteropolyanions selected from phosphates and silicates, the pH of the first aqueous composition being selected in a range of from 3.5 to 10.

15. The method as claimed in claim 1, wherein the concentration of solid matter in the first aqueous composition is from 1 to 400 g/l.

16. The method as claimed in claim 1, wherein in step i), the solid material and the first layered double hydroxide are in the form of an intimate mixture of solid particles dispersed in the first aqueous composition.

17. A method for extracting or purifying a refractory metal selected from Nb, Ta, Mo, W, V, said method implementing a first layered double hydroxide containing interlayer anions A1n−, n being a positive integer, and a mixture of at least two of said refractory metals, from a solid material comprising said refractory metal in an oxidized form, by a method as defined in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0154] The appended drawings illustrate the invention:

[0155] FIG. 1 represents a figure showing the performance of a layered double hydroxide used for extracting tungsten from a concentrated ore.

[0156] FIG. 2 represents a figure showing the performance of a layered double hydroxide used for extracting tantalum from a concentrated ore.

EXAMPLES

Example 1: Leaching of a Tungsten Oxide from a Pure Tungsten Oxide, Using Hydrotalcite of Formula Mg.SUB.6.Al.SUB.2.CO.SUB.3.(OH).SUB.16..4H.SUB.2.O as First Layered Hydroxide

[0157] 46 mg of tungsten oxide sold under reference 101921593 by Sigma Aldrich, comprising about 79% by mass of tungsten, and 50 mg of hydrotalcite as first layered double hydroxide were dispersed in 20 ml of water to form a first aqueous composition. The pH of the composition was adjusted to 4.5 using 1M phosphoric acid.

[0158] The first aqueous composition was stirred at ambient temperature for 24 hours, to allow the leaching of the tungsten in the form of polyoxometallates and the sorption of said polyoxometallates within the hydrotalcite in place of the carbonate anions, to form a second layered hydroxide.

[0159] The first aqueous composition was filtered to recover the second layered hydroxide.

[0160] 50 mg of the second layered hydroxide were dispersed in 20 ml of water to form a second aqueous composition containing a carbonate ion concentration of 10.sup.−2M. The pH of the composition was adjusted to 10 by addition of a 1M NaOH solution.

[0161] The second aqueous composition was stirred at ambient temperature for 24 hours, to allow the desorption of the polyoxometallates within the second layered hydroxide, and to form monomeric species of the tungsten in solution.

[0162] FIG. 1 [Ex. 1a) and Ex. 1b)] shows the tungsten extraction performance by the method as described in example 1 [Ex. 3b)], and, for comparison, the absence of extraction or negligible extraction of tungsten when the first aqueous composition does not comprise hydrotalcite [Ex. 3a)].

Example 2: Extraction of Tantalum from a Concentrated WEEE, Using the Compound of Formula Mg.SUB.6.Fe.SUB.2.(CO.SUB.3.).SUB.1.76.(OH).SUB.14.7..7.2H.SUB.2.O as First Layered Hydroxide

[0163] 1.5 g of motherboard containing about 0.1 to 0.4% by mass of tantalum in an oxidized form, supplied by Terrallova Développement (TND), were mixed with 1.36 g of sodium hydroxide and the mixture was heated at 400° C. for 5 hours. The alkaline treatment carried out in this way produced an intermediate solid material, which was then ground.

[0164] 575 mg of the intermediate solid material and 50 mg of a compound of formula Mg.sub.6Fe.sub.2(CO.sub.3).sub.1.76(OH).sub.14.7.7.2H.sub.2O as first layered double hydroxide were dispersed in 50 ml of water to form a first aqueous composition. The pH of the composition was adjusted to 12 by addition of a concentrated NaOH solution.

[0165] The first aqueous composition was stirred at ambient temperature for 24 hours, to allow the leaching of the tantalum in the form of polyoxometallates and the sorption of said polyoxometallates within the first layered double hydroxide in place of the carbonate anions, to form a second layered hydroxide.

[0166] The first aqueous composition was filtered to recover the second layered hydroxide.

[0167] 50 mg of the second layered hydroxide were dispersed in 25 ml of water to form a second aqueous composition containing a carbonate ion concentration of 10.sup.−2M. The pH of the composition was adjusted to 9 by addition of nitric acid. Then 6 mg of KH.sub.2PO.sub.4 were added, followed by 2.1 ml of a 30% by mass aqueous solution of H.sub.2O.sub.2.

[0168] The second aqueous composition was stirred at ambient temperature for 24 hours, to allow the desorption of the polyoxometallates within the second layered hydroxide and to form monomeric species of the tantalum in solution.

[0169] FIG. 2 [Ex. 2a) and Ex. 2b)] shows the tantalum extraction performance by the method as described in example 2 [Ex. 2b)], and, for comparison, the absence of extraction or low level of extraction of tantalum when the first aqueous composition does not comprise layered double hydroxide [Ex. 2a)].

Example 3: Extraction of Tantalum from a Concentrated Ore, Using the Compound of Formula Mg.SUB.6.Fe.SUB.2.(CO.SUB.3.).SUB.1.76.(OH).SUB.14.7..7.2H.SUB.2.O as First Layered Hydroxide

[0170] 2.5 g of a concentrated ore (coltan) comprising about 5 to 20% by mass of tantalum in an oxidized form, supplied by Terrallova Développement (TND), were mixed with 1.36 g of sodium hydroxide and the mixture was heated at 400° C. for 5 hours. The alkaline treatment carried out in this way produced an intermediate solid material, which was then ground.

[0171] 198 mg of the intermediate solid material and 25 mg of a compound of formula Mg.sub.6Fe.sub.2(CO.sub.3).sub.1.76(OH).sub.14.7.7.2H.sub.2O as first layered double hydroxide were dispersed in 50 ml of water to form a first aqueous composition. The pH of the composition was adjusted to 12 by addition of a concentrated NaOH solution.

[0172] The first aqueous composition was stirred at ambient temperature for 24 hours, to allow the leaching of the tantalum in the form of polyoxometallates and the sorption of said polyoxometallates within the first layered double hydroxide in place of the carbonate anions, to form a second layered hydroxide.

[0173] The first aqueous composition was filtered to recover the second layered hydroxide.

[0174] 25 mg of the second layered hydroxide were dispersed in 25 ml of a solution containing 0.06 mg of sodium carbonate to form a second aqueous composition. The pH of the composition was adjusted to 9 by addition of nitric acid. Then 6 mg of KH.sub.2PO.sub.4 were added, followed by 2.1 mL of 30% H.sub.2O.sub.2.

[0175] The second aqueous composition was stirred at ambient temperature for 24 hours, to allow the desorption of the polyoxometallates within the second layered hydroxide and to form monomeric species of the tantalum in solution.

[0176] FIG. 2 [Ex. 3a) and Ex. 3b)] shows the tantalum extraction performance by the method as described in example 3 [Ex. 3b)], and, for comparison, the absence of extraction or negligible extraction of tantalum when the first aqueous composition does not comprise layered double hydroxide [Ex. 3a)].