Electrorecovery of metals

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.

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.

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 selected from the group consisting of transition metals, group IIIA to VIA metals, alkali metals, alkali earth metal, rare earth metals, and metalloids;
• wherein the minimum concentration of metal ions in the ionic liquid is reduced to half or less than half of the concentration of metal ions in the ionic liquid for electrodeposition to occur compared to a method using an ionic liquid having non-coordinating cations.

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 metal ion in the ionic liquid,
• the ionic liquid including an ionic liquid cation and an ionic liquid anion, whereby the metal ion in solution forms a metal complex 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 the metal ion, and wherein the donor centres (D) are present in a sufficient number and are of sufficient Lewis basicity such that the ionic liquid cation interacts with the metal ion to be recovered in preference to the at least one ionic liquid anion that would otherwise co-ordinate to the metal ion such that interaction of the ionic liquid cation with the metal ion takes place to form a neutral or positive charge on the metal complex or to reduce a size of the negative charge on the metal complex as compared to their charge if coordination had occurred by the ionic liquid anion of the ionic liquid alone;
• and
• wherein the ionic liquid cation is such that a complex formation constant between the metal ion and the ionic liquid cation allows sufficient bond formation with the metal ion in the dissolution process to form the metal complex and ease of bond breaking allows metal recovery from the metal complex at the cathode;
• and
• subjecting the metal complex to an electrical potential between a cathode and anode to recover metal from the metal complex at the cathode;
• and
• wherein the metal is selected from the group consisting of transition metals, group IIIA to VIA metals, alkali metals, alkali earth metals, rare earth metals, and metalloids.