System and process for progressive refractory ore transformation for copper leaching
A hydrometallurgical process for processing metal ore includes a dynamic oxidative step in which the ore is irrigated with specific reactive liquid mixtures at low flow rates to progressively transform the ore and maintain conditions for enhanced recovery of metal from the ore by solvent-extraction/electrowinning. In embodiments, the systems and methods described herein may be used for obtaining copper metal from the refractory copper mineral chalcopyrite. A copper heap subjected to the electrochemical regimes established and maintained in the heap using these methods exhibit novel kinetics.
1. A method for recovering copper from copper ore, comprising:
activating crushed copper ore with an agglomerating solution comprising nitrate ions, sulfuric acid, at least one of ferric ions and ferrous ions, and an oxidizing agent;
forming a heap of the activated copper ore and allowing the heap to rest;
irrigating the heap after resting at a flow rate of 0.5-5 L/h·m 2 with a first reactive liquid mixture comprising nitrate ions, sulfuric acid, an oxidizing agent and at least one of ferrous and ferric ions;
subsequent to irrigating with the first reactive liquid mixture, irrigating the heap at a flow rate of 0.5-5 L/h·m 2 with a second reactive liquid mixture comprising sulfuric acid, nitrate ion, at least one of ferrous and ferric ions, an oxidizing agent and a copper-containing solution, until a molar ratio of dissolved copper to chalcopyrite in the heap in a range of 0.3:1 to 0.6:1 is reached; and
subjecting the heap to leaching with a leaching solution at a rate greater than 5 L/h·m 2 to obtain a copper-rich pregnant liquor solution (PLS).
2. The method according to claim 1 , wherein the flow rate of irrigating the heap with the first and second reactive liquid mixtures is in a range of 1-3 L/h·m 2 .
3. The method according to claim 1 , wherein said copper ore contains primarily copper sulfide species.
4. The method according to claim 1 , wherein said copper ore contains primarily chalcopyrite.
5. The method according to claim 1 , wherein the oxidizing agent in the agglomerating solution and in the first and second reactive liquid mixtures is selected from the group consisting of aqueous hydrogen peroxide, gaseous ozone in micro and nano bubbles, gaseous oxygen in micro and nano bubbles, air in micro and nano bubbles, and a mixture thereof.
6. The method according to claim 1 , wherein the agglomerating solution used in activating the crushed copper ore comprises: nitrate ion at a concentration in a range of 0.4 M to 3.2 M; sulfuric acid at a concentration in a range of 0.2 M to 3 M; at least one of ferrous and ferric ions at a concentration in a total amount of 0.03 M to 0.18 M and hydrogen peroxide at a concentration in a range of 0.02 to 0.06 M; and wherein an oxidation-reduction potential (ORP) of the agglomeration solution is higher than 770 mV vs. Standard Hydrogen Electrode (SHE).
7. The method according to claim 1 , wherein after said activating, the crushed copper ore has a moisture content in a range of 3 to 12 percent by weight.
8. The method according to claim 1 , wherein after forming the heap of the activated copper ore, the heap is allowed to rest without irrigation for 5 to 15 days.
9. The method according to claim 1 , comprising irrigating the heap at a flow rate of 0.5-5 L/h·m 2 with the first reactive liquid mixture until a molar ratio of dissolved copper to chalcopyrite in the heap is reached between 0.1:1 to 0.3:1.
10. The method according to claim 1 , wherein the first reactive liquid mixture comprises nitrate ion at a concentration in a range of 0.02 M to 0.4 M, sulfuric acid at a concentration in a range of 0.05 M to 1 M, at least one of ferrous and ferric ions at a concentration in a total amount of 0.02 M to 0.3 M, hydrogen peroxide at a concentration in a range of 0.03 M to 0.3 M; and a dissolved copper concentration less than 2 mM.
11. The method according to claim 1 , wherein the second reactive liquid mixture comprises nitrate ion at a concentration in a range of 0.02 M to 0.4 M, sulfuric acid at a concentration in a range of 0.05 M to 1 M, at least one of ferrous and ferric ions at a concentration in a total amount of 0.02 M to 0.3 M, hydrogen peroxide in a range of 0.03 M to 0.3 M; and copper ions in a concentration of 2 mM to 100 mM.
12. The method according to claim 1 , wherein the copper-containing solution comprises an aqueous stream obtained from the bottom of the heap after said irrigation with said first reactive liquid mixture.
13. The method according to claim 1 , wherein the copper-containing solution further comprises an aqueous stream obtained from the bottom of the heap after said irrigation with said second reactive liquid mixture.
14. The method according to claim 1 , wherein said leaching solution comprises nitrate ion, sulfuric acid, and at least one of ferric and ferrous ions.
15. The method according to claim 1 , wherein the leaching solution comprises nitrate ion at a concentration in a range of 1 mM to 160 mM, sulfuric acid at a concentration in a range of 0.05 M to 1 M, and ferric and/or ferrous ions at a concentration in a range of 1 mM to 180 mM.
16. The method according to claim 15 , wherein the leaching solution further comprises hydrogen peroxide at a concentration in a range of 0.01-0.3 M.
17. The method according to claim 16 , wherein the leaching solution further comprises copper ions.
18. The method according to claim 16 , wherein the PLS is subjected to solvent-extraction, and the leaching solution further comprises raffinate from the solvent extraction.
19. The method according to claim 1 , wherein the leaching step is conducted at an irrigation rate of 5-12 L/h·m 2 .
20. The method according to claim 1 , wherein after forming the heap and prior to irrigating the heap with the first reactive liquid mixture, the heap is allowed to rest between 5 to 15 days, followed by irrigating the heap with a third reactive liquid mixture,
wherein in said third reactive liquid mixture the concentration of nitrate ion is in a range of 0.4 M to 3.2 M, the concentration of sulfuric acid is in a range of 0.2 M to 3 M, the concentration of ferric and ferrous ions in a total amount of 0.03 M to 0.18 M and said third reactive liquid mixture further comprises an oxidizing agent.
21. The method according to claim 20 , wherein the oxidizing agent in the third reactive liquid mixture is selected from the group consisting of aqueous hydrogen peroxide, gaseous ozone in micro and nano bubbles, gaseous oxygen in micro and nano bubbles, air in micro and nano bubbles, and a mixture thereof.
22. The method according to claim 20 , wherein irrigating the heap with the third reactive liquid mixture is conducted at an irrigation rate of 0.5-5 L/h·m 2 .
23. The method according to claim 22 , wherein irrigating the heap with a third reactive liquid mixture is conducted until reaching a volume ratio of about 0.05-0.15 m 3 of said third reactive liquid mixture per ton of the copper ore.
24. The method according to claim 22 , wherein in said third reactive liquid mixture the concentration of hydrogen peroxide is in a range of 3 mM to 150 mM.
25. The method according to claim 1 , wherein the PLS is subjected to solvent extraction and electrowinning (SX/EW) process, and at least one of the agglomerating solution, the first reactive liquid mixture, the second reactive liquid mixture, the third reactive liquid mixture, and the leaching solution further comprises raffinate from the solvent extraction process.
26. The method according to claim 20 , wherein the agglomerating solution, the first reactive liquid mixture, the second reactive liquid mixture and the third reactive liquid mixture each has a redox potential higher than 770 mV (vs SHE).
27. The method according to claim 22 , wherein the heap irrigated with the first reactive liquid mixture, the second reactive liquid mixture and the third reactive liquid mixture, is maintained at a temperature in a range of about 30-45° C.
28. The method according to claim 1 , comprising rinsing the heap after leaching to recover residual leaching solution.
29. The method according to claim 1 , further comprising subjecting the PLS to solvent extraction to obtain a copper-rich electrolyte stream.
30. The method according to claim 29 , further comprising subjecting the copper-rich electrolyte stream to electrowinning to obtain copper cathodes.