Electrorecovery of metals

Patent metadata

Field	Value
Publication number	US-9580772-B2
Application number	US-201013257022-A
Country	US
Kind code	B2
Filing date	Mar 17, 2010
Priority date	Mar 17, 2009
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

A method and ionic liquid for the electrorecovery of metal from a metal salt including at least one metal ion. The method includes the steps of dissolving the metal salt in an ionic liquid, the ionic liquid including an ionic liquid cation and an ionic liquid anion; whereby the metal ion of the metal salt forms a metal complex in solution with at least the ionic liquid cation; and subjecting the metal complex to an electrical potential between a cathode and anode to recover metal at the cathode. The ionic liquid includes an ionic liquid cation and an ionic liquid anion, wherein the ionic liquid cation has an affinity for the metal ion which is at least about equal to that of the ionic liquid anion for the metal ion.

First claim

The invention claimed is:

1. A method for the electrorecovery of metal from a metal salt, the method including the steps of:
dissolving the metal salt in an ionic liquid to form a solution of metal ions in the ionic liquid,
the ionic liquid including an ionic liquid cation and an ionic liquid anion, whereby the metal ions in solution form metal complexes in solution with at least the ionic liquid cation, wherein the ionic liquid cation includes at least one heteroatom having a positive charge and at least one donor centre (D) having a lone pair of electrons with sufficient Lewis basicity for coordination to each metal ion to form a neutral or positive charge on the metal complexes or to reduce a size of a negative charge on the metal complexes as compared to their charge if coordination had occurred by the ionic liquid anion of the ionic liquid alone, wherein an affinity of the ionic liquid cation for the each metal ion is at least about equal to that of an affinity of the ionic liquid anion for each metal ion to be recovered; and
wherein the ionic liquid cation is such that a complex formation constant between each metal ion to be recovered and the ionic liquid cation allows sufficient bond formation with each metal ion in the dissolution process to form the metal complexes and ease of bond breaking allows metal recovery from the metal complexes at a cathode; and

subjecting the metal complexes to an electrical potential between the cathode and an anode to recover metal from the metal complexes at the cathode; and
wherein the metal is aluminium.

2. The method of claim 1 , wherein the heteroatom is selected from the group consisting of group VA and group VIA elements of the periodic table.

3. The method of claim 1 , wherein the donor centre (D) includes an atom selected from the group consisting of the group VA to group VIIA elements of the periodic table.

4. The method of claim 3 , wherein the donor centre (D) includes an atom selected from the group consisting of O, N, S and P.

5. The method of claim 3 , wherein the donor centre (D) includes an oxygen atom.

6. The method of claim 1 , wherein the ionic liquid cation is 1-alkyl-1,4-diazabicyclo[2.2.2]octane (C n DABCO).

7. The method of claim 6 , wherein the alkyl group (C n ) is C 1 to C 14 moiety that is saturated, unsaturated, branched or contains other functionalities.

8. The method of claim 1 , wherein the ionic liquid anion is bis(trifluoromethylsulfonyl)amide.

9. The method of claim 1 , wherein the metal complexes further include the ionic liquid anion.

10. The method of claim 1 , wherein the metal complexes are not negatively-charged.

11. The method of claim 1 , wherein co-ordination by the ionic liquid cation of the ionic liquid to the at least one metal ion forms a neutral or positively-charged metal complex among the metal complexes.

12. The method of claim 1 , wherein the donor centres (D) are present in a sufficient number to allow interaction with the at least one metal ion in preference to the ionic liquid anion that would otherwise co-ordinate to the metal ion.

13. A method of accelerating the rate of reduction of a metal complex at a negatively charged cathode during electrorecovery of metal from a metal salt in an ionic liquid, the method comprising:
wherein the metal salt includes at least one metal ion, and the ionic liquid includes an ionic liquid cation and an ionic liquid anion,
wherein the ionic liquid anion forms a first negatively charged metal complex with the at least one metal ion,
forming a metal complex less negatively charged than the first negatively charged complex by:
adding to the first negatively charged metal complex at least one ionic liquid cation including at least one heteroatom having a positive charge and at least one donor centre (D) having a lone pair of electrons with sufficient Lewis basicity for co-ordination to the at least one metal ion to form the less negatively charged metal complex; or
substituting at least one ionic liquid anion of the first negatively charged metal complex with an ionic liquid cation including at least one heteroatom having a positive charge and at least one donor centre (D) having a lone pair of electrons with sufficient Lewis basicity for co-ordination to the at least one metal ion to form the less negatively charged metal complex; and

wherein formation of the less negatively charged metal complex assists in the approach of the less negatively charged metal complex to the negatively charged cathode such that current density of the less negatively charged metal complex reaching the cathode per unit area is from 3 to 5 times higher than current densities achievable when non-coordinating cations are used.

14. The method of claim 13 , wherein the approach of the less negatively charged metal complex to the negatively charged cathode is assisted by reducing the Coulombic resistance to movement of the less negatively charged metal complex toward the negatively charged cathode.

15. The method of claim 13 wherein the metal is selected from the group consisting of transition metals, group IIIA to VIA metals, alkali earth metals, rare earth metals, and metalloids.

16. A method for the electrorecovery of metal from a metal salt including at least one metal ion, the method including the steps of:
dissolving the metal salt in an ionic liquid, the ionic liquid including an ionic liquid cation and an ionic liquid anion, whereby the anion is selected from:

and
whereby the metal ion of the metal salt forms a metal complex in solution with at least the ionic liquid cation, wherein the ionic liquid cation includes at least one heteroatom that has a positive charge and at least one donor centre (D) having a lone pair of electrons with sufficient Lewis basicity for co-ordination to the metal ion to form a metal complex less negatively charged than if co-ordination had occurred by the anion of the ionic liquid alone; and
subjecting the metal complex to an electrical potential between a cathode and anode to recover metal at the cathode;
wherein the metal is selected from the group consisting of transition metals, group IIIA to VIA metals, alkali earth metal; rare earth metals, and metalloids.

17. The method of claim 16 wherein the metal complex includes only the ionic liquid cation and not the ionic liquid anion.

18. The method of claim 16 wherein the ionic liquid is fluid enough at operating temperatures to allow transport of the complexed metal ions during the electrorecovery process.

19. A method for reducing the bulk concentration of metal ions required in the electrorecovery of metal from a metal salt including at least one metal ion, the method including the steps of:
dissolving the metal salt in an ionic liquid, the ionic liquid including an ionic liquid cation and an ionic liquid anion, whereby the metal ion of the metal salt forms a metal complex in solution with at least the ionic liquid cation, wherein the ionic liquid cation includes at least one heteroatom that has a positive charge and at least one donor centre (D) having a lone pair of electrons with sufficient Lewis basicity for co-ordination to the metal ion to form a metal complex less negatively charged than if co-ordination had occurred by the anion of the ionic liquid alone; and
subjecting the metal complex to an electrical potential between a cathode and anode to recover metal at the cathode;
wherein the metal is s

Assignees

• Rodopoulos Theo
• Horne Michael David
• Ruether Thomas
• Commw Scient Ind Res Org

Inventors

• Rodopoulos Theo
• Horne Michael David
• Ruether Thomas

Classifications

• C22B21/0015 Primary

  by wet processes (C22B21/02, C22B21/04 and C22B21/06 take precedence) · CPC title

• C25C3/00

  Electrolytic production, recovery or refining of metals by electrolysis of melts (C25C5/00 takes precedence) · CPC title

• Y02P10/234

  Cross-Sectional Technologies · mapped topic

• C25C3/18

  Electrolytes · CPC title

• C25C3/06

  of aluminium · CPC title