LEACHING OF PRECIOUS AND CHALCOPHILE METALS

1 . A process for recovery of one or more target metals, selected from precious metals and chalcophile metals as respectively herein defined, from materials containing precious and/or chalcophile metals, the process including:

leaching the material containing metals with an aqueous leaching solution containing:

a metal liberator comprising an amino acid; and

a metal retainer comprising one or more of ammonia, ammonium salts, carboxylic acids, carboxylic acid salts, dicarboxylic acids, dicarboxylic acid salts, hydroxy-carboxylic acids, hydroxy-carboxylic acid salts, ethylene diamine tetra-acetic acid (EDTA) and EDTA salts,

to produce a leachate containing the one or more target metals; and

(ii) extracting the one or more target metals from the leachate, wherein the one or more target metals are selected from gold, silver, palladium, platinum, copper, nickel, cobalt and zinc; and

wherein the metal retainer is present in solution at a concentration of at least 0.001 M.

2 . The process of claim 1 , wherein the amino acid comprises one or more of Glycine, Histidine, Valine, Alanine, Phenylalanine, Cysteine, Aspartic Acid, Glutamic Acid, Lysine, Methionine, Serine, Threonine, and Tyrosine.

3 . The process of claim 2 , wherein the amino acid comprises glycine or glutamic acid.

4 . The process of claim 1 , wherein the amino acid concentration in solution ranges from 0.01 to 250 grams per litre.

5 . The process of claim 1 , wherein the aqueous leaching solution is substantially free of intentional additions of thiourea and/or transition metal salts.

6 . The process of claim 1 , wherein the metal retainer comprises ammonia or an ammonium salt.

7 . The process of claim 6 , wherein the ammonium salt is selected from ammonium sulfate, ammonium halide, ammonium carbonate, ammonium nitrate, ammonium oxalate and ammonium acetate.

8 . The process of claim 1 , wherein the molar ratio between the one or more target metals in solution and the metal retainer is at least 1:2.

9 . The process of claim 1 , wherein the leaching is conducted in the presence of an oxidant selected from air (gaseous and dissolved states) and oxygen (gaseous and dissolved states).

10 . The process of claim 1 , wherein the leaching is conducted in the presence of a small amount of a catalyst.

11 . The process of claim 1 , wherein the leaching is conducted under alkaline conditions.

12 . The process of claim 1 , wherein the leaching is conducted under acidic conditions.

13 . The process of claim 1 , wherein the material containing the precious metal and/or chalcophile metal is selected from an ore, an ore concentrate, a waste material, a mining or metallurgical process intermediate or a metal-contaminated soil.

14 . The process of claim 1 , wherein the one or more target metals are non-precious metals.

15 . The process of claim 14 , wherein the one or more target metals are selected from nickel, cobalt and copper.

16 . The process of claim 15 , wherein the one or more target metals are selected from nickel and cobalt.

17 . The process of claim 13 , wherein the material containing metals is a nickel and/or cobalt ore.

18 . The process of claim 14 , wherein the one or more target metals is copper.

19 . The process of claim 13 , wherein the material containing metals is e-waste.

20 . The process of claim 1 , wherein the aqueous leaching solution includes a dissolved oxygen concentration of 0.1-100 milligrams per litre.

21 . The process of claim 1 , wherein the mass ratio of metal liberator: metal retainer is at least 2:1.

22 . A target metal recovered from the process of claim 1 .