Processes for selective recovery of rare earth metals present in acidic aqueous phases resulting from the treatment of spent or scrapped permanent magnets

Patent metadata

Field	Value
Publication number	US-10464819-B2
Application number	US-201515511926-A
Country	US
Kind code	B2
Filing date	Sep 22, 2015
Priority date	Sep 24, 2014
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

The invention relates to a hydrometallurgical process which makes it possible to selectively recover at least one “heavy” rare earth metal, i.e. a rare earth metal with an atomic number at least equal to 62, that is in an acidic aqueous phase resulting from the treatment of spent or scrapped permanent magnets. It also relates to a hydrometallurgical process which makes it possible to selectively recover, on the one hand, at least one heavy rare earth metal present in an acidic aqueous phase resulting from the treatment of spent or scrapped permanent magnets and, on the other hand, at least one “light” rare earth metal, i.e. a rare earth metal with an atomic number at most equal to 61, that is also in this acidic aqueous phase. The invention has in particular an application in the recycling of rare earth metals present in spent or scrapped permanent magnets of the type Neodymium-Iron-Boron (or NdFeB) and, in particular, dysprosium, praseodymium and neodymium, and also in the recycling of samarium present in spent or scrapped permanent magnets of the type samarium-cobalt (or SmCo).

First claim

The invention claimed is:

1. A method for selective recovery of at least one rare earth metal TR1 having an atomic number at least equal to 62 from an acid aqueous phase A1, the aqueous phase A1 stemming from a processing of spent or scrapped permanent magnets and comprising one or more rare earth metals TR1, transition metals and an acid having a concentration from 0.2 mol/L to 6 mol/L, the acid being nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof, which method comprises:
a) extracting the rare earth metal TR1 from the aqueous phase A1, the extraction comprising putting the aqueous phase A1 in contact with an organic phase S1 not miscible with water, which comprises a diglycolamide having a total number of carbon atoms at least equal to 24 as an extractant, in an organic diluent, and then separating the aqueous phase A1 from the organic phase S1;
b) washing the organic phase S1 stemming from a), the washing comprising putting the organic phase S1 in contact with an acid aqueous phase A2 which comprises an acid identical with the acid of the aqueous phase A1, at a concentration at most equal to the acid concentration of the aqueous phase A1, and then separating the aqueous phase A2 from the organic phase S1; and
c) stripping the rare earth metal TR1 from the organic phase S1 stemming from b), the stripping comprising putting the organic phase S1 in contact with an acid aqueous phase A3 which has a pH at least equal to 3, and then separating the aqueous phase A3 from the organic phase S1.

2. The method of claim 1 , wherein the diglycolamide has the formula: R 1 (R 2 )N—C(O)—CH 2 —O—CH 2 —C(O)—N(R 3 )R 4 wherein each of R 1 to R 4 represents a linear or branched alkyl group comprising at least 5 carbon atoms.

3. The method of claim 1 , wherein the diglycolamide is N,N,N′,N′-tetraoctyl-3-oxapentanediamide, N,N,N′,N′-tetra(2-ethylhexyl)-3-oxapentanediamide, N,N,N′,N′-tetradecyl-3-oxapentanediamide or N,N,N′,N′-tetradodecyl-3-oxapentanediamide.

4. The method of claim 1 , wherein the organic phase S1 comprises from 0.05 mol/L to 1 mol/L of the diglycolamide.

5. The method of claim 1 , wherein the aqueous phase A2 comprises from 0.01 mol/L to 0.5 mol/L of the acid.

6. The method of claim 1 , wherein the aqueous phase A3 comprises from 0.0001 mol/L to 0.001 mol/L of nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof.

7. The method of claim 1 , wherein the strong acid of the aqueous phases A1 and A2 is nitric acid.

8. The method of claim 1 , which comprises a cycle, the cycle comprising a), b), c) and a purification of the organic phase S1 stemming from c).

9. The method of claim 1 , wherein the aqueous phase A1 stems from the processing of neodymium-iron-boron permanent magnets in nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof and the rare earth metal TR1 is dysprosium.

10. A method for selective recovery of at least one rare earth metal TR1 having an atomic number at least equal to 62 and of at least one rare earth metal TR2 having an atomic number at most equal to 61 from an acid aqueous phase A1, the aqueous phase A1 stemming from a processing of spent or scrapped permanent magnets and comprising one or more rare earth metals TR1, one or more rare earth metals TR2, transition metals and an acid having a concentration from 0.2 mol/L to 6 mol/L, the acid being nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof, which method comprises:
recovery of the rare earth metal TR1 from the aqueous phase A1, which recovery comprises:
a) extracting the rare earth metal TR1 from the aqueous phase A1, the extraction comprising putting the aqueous phase A1 in contact with an organic phase S1 not miscible with water, which comprises a diglycolamide having a total number of carbon atoms at least equal to 24 as an extractant, in an organic diluent, and then separating the aqueous phase A1 from the organic phase S1;
b) washing the organic phase S1 stemming from a), the washing comprising putting the organic phase S1 in contact with an acid aqueous phase A2, which comprises an acid identical with the acid of the aqueous phase A1, at a concentration at most equal to the strong acid concentration of the aqueous phase A1, and then separating the aqueous phase A2 from the organic phase S1; and
c) stripping the rare earth metal TR1 from the organic phase S1 stemming from b), the stripping comprising putting the organic phase S1 in contact with an acid aqueous phase A3 which has a pH at least equal to 3, and then separating the aqueous phase A3 from the organic phase S1; and
recovery of the rare earth metal TR2 from the aqueous phase A1 stemming from a), which recovery comprises:
d) extracting the rare earth metal TR2 from the aqueous phase A1 stemming from a), the extraction comprising putting the aqueous phase A1 in contact with an organic phase S2 not miscible with water, which comprises an extractant identical with the extractant of the organic phase S1, in an organic diluent, and then separating the aqueous phase A1 from the organic phase S2;
e) washing the organic phase S2 stemming from d), the washing comprising putting the organic phase S2 in contact with an acid aqueous phase A4, which comprises an acid identical with the acid of the aqueous phase A1, at a concentration at most equal to the acid concentration of the aqueous phase A1 stemming from a), and then separating the aqueous phase A4 from the organic phase S2; and
f) stripping the rare earth metal TR2 from the organic phase S2 stemming from e), the stripping comprising putting the organic phase S2 in contact with an acid aqueous phase A5 which has a pH at least equal to 3, and then separating the aqueous phase A5 from the organic phase S2.

11. The method of claim 10 , wherein the diglycolamide has the formula: R 1 (R 2 )N—C(O)—CH 2 —O—CH 2 —C(O)—N(R 3 )R 4 wherein each of R 1 to R 4 represents a linear or branched alkyl group comprising at least 5 carbon atoms.

12. The method of claim 10 , wherein the diglycolamide is N,N,N′,N′-tetraoctyl-3-oxapentanediamide, N,N,N′,N′-tetra(2-ethylhexyl)-3-oxapentanediamide, N,N,N′,N′-tetradecyl-3-oxapentanediamide or N,N,N′,N′-tetradodecyl-3-oxapentanediamide.

13. The method of claim 10 , wherein the organic phase S1 comprises from 0.05 mol/L to 1 mol/L of the diglycolamide.

14. The method of claim 10 , wherein the aqueous phase A2 comprises from 0.01 to 0.5 mol/L of the acid.

15. The method of claim 10 , wherein the aqueous phase A4 comprises from 0.2 mol/L to 4 mol/L of the acid.

16. The method of claim 10 , wherein each of the aqueous phases A3 and A5 comprises from 0.0001 mol/L to 0.001 mol/L of nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof.

17. The method of claim 10 , wherein the acid of the aqueous phases A1, A2 and A4 is nitric acid.

18. The method of claim 10 , which comprises a first and a second cycle, the first cycle comprising a), b) and c), the second cycle comprising d), e) and f), the first and second cycles further comprising a purification of an organic phase formed by grouping the organic phase S1 stemming from c) and the organic phase S2 stemming from f) and dividing the thereby purified organic phase into the organic phase S1 and the organic phase S2.

19. The method of claim 10 , wherein the aqueous phase A1 stems from the processing of neodymium-iron-boron permanent magnets in nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid or a mixture thereof and c

Assignees

• Commissariat Energie Atomique
• Commissariat A Lenergie Atomique Aux Energies Alternatives

Inventors

• Miguirditchian Manuel
• Haquin Victor
• Pacary Vincent
• Laucournet Richard
• Montuir Marc

Classifications

• C22B7/007 Primary

  by acid leaching · CPC title

• C01F17/276

  Nitrates · CPC title

• C01P2006/80

  Compositional purity · CPC title

• C22B60/026

  liquid-liquid extraction with or without dissolution in organic solvents · CPC title

• C22B59/00

  Obtaining rare earth metals · CPC title