Chloride heap leaching

1. A hydrometallurgical method of recovering copper from a material, in a heap, that contains a copper sulphide mineral which contains at least chalcopyrite comprising leaching the material in an acidic chloride solution or a mixed chloride/sulphate solution in the presence of dissolved oxygen and maintaining the mineral's surface potential within a range of 550 mV (vs. SHE) to 600 mV (vs. SHE) by controlling the chloride ion concentration at a level between 5 g/L to 100 g/L to control the ratio of Cu(II) to Cu(I) within the solution to cause dissolution of at least 40% of the copper sulphide in about 600 hours, and recovering copper from the solution.

2. The method according to claim 1 wherein the copper sulphide is in a low-grade transitional and hypogene ore.

3. The method according to claim 1 wherein the copper sulphide is in a low-grade supergene ore.

4. The method according to claim 1 wherein the pH of the solution is less than about 3.

5. The method according to claim 4 wherein the pH of the solution is between about 1 and about 2.

6. The method according to claim 1 which includes the steps of controlling the pH of the solution by the addition of H 2 SO 4 , HCl or HNO 3 .

7. The method according to claim 1 wherein the dissolved oxygen level is in excess of 1 ppm.

8. The method according to claim 1 wherein the chloride concentration is controlled by the addition of at least one of the following: HCl, NaCl, MgCl 2 , saline water, sea water or chloride-containing process water.

9. The method according to claim 1 comprising maintaining the mineral's surface potential within a range of 550 mV (vs. SHE) to 580 mV (vs. SHE).

10. The method according to claim 1 wherein the leaching solution contains less than about 5 g/L ferric ion.

11. The method according to claim 1 wherein the leaching solution does not contain any ferric ions.

12. The method according to claim 1 wherein the leaching is conducted at ambient temperature.