Process for making copper metal powder, copper oxides and copper foil

• US 5,670,033 A
• Filed: 10/18/1995
• Issued: 09/23/1997
• Est. Priority Date: 04/19/1993
• Status: Expired due to Term

• Current Assignee: Nikko Materials USA, Inc. (Eternal Materials Co., Ltd.)
• Original Assignee: Electrocopper Products Limited
• Inventors: Peckham, Peter, Burgess, David P., Jenkins, Jackson G., Kohut, Stephen J., Haines, Ronald K., Gort, Wendy M.
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Mee, Brendan
• Application Number:
  US08/544,619
• Time in Patent Office: 706 Days
• Field of Search: 205/74, 205/580, 205/581, 205/583, 205/584, 205/77, 423/24, 423/27, 423/28, 423/41, 75/429
• US Class Current: 205/74
• CPC Class Codes: C01G 3/02 Oxides; Hydroxides
• CPC Class Codes: C01P 2006/10 Solid density
• CPC Class Codes: C01P 2006/80 Compositional purity
• CPC Class Codes: C25C 1/12 of copper
• CPC Class Codes: C25C 5/02 from solutions
• CPC Class Codes: C25D 1/04 Wires; Strips; Foils

Abstract

This invention is directed to a process for making copper metal powder from copper-bearing material, comprising: (A) contacting said copper-bearing material with an effective mount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution; (B) contacting said copper-rich aqueous leaching solution with an effective amount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution; (C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution; (D) contacting said copper-rich extractant with an effective amount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant; (E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution; (F) advancing said first electrolyte solution to an electrolytic cell equipped with at least one first anode and at least one first cathode, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode; and (G) removing copper metal powder from said first cathode. In one embodiment the first electrolyte solution used in step (F) is characterized by a chloride ion concentration of up to about 5 ppm. In one embodiment the first electrolyte solution used in step (F) contains at least one triazole. In one embodiment the copper metal powder is convened to copper foil. In one embodiment the copper metal powder is converted to cuprous oxide, cupric oxide or a mixture thereof; these copper oxides can be readily dissolved in sulfuric acid and used to make copper foil.

Claims

1. A process for making copper metal powder from a copper-bearing material, comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B) contacting said copper-rich aqueous leaching solution with an effective mount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution;

(C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution;

(D) contacting said copper-rich extractant with an effective mount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant;

(E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution;

(F) advancing said first electrolyte solution into an electrolytic cell equipped with at least one first anode and at least one first cathode, said electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective mount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode; and

(G) removing copper metal powder from said first cathode.

2. The process of claim 1 with the steps of:

(H) dissolving said copper powder from step (G) in an aqueous sulfuric acid solution to form a second electrolyte solution;

(I) flowing said second electrolyte solution in an electroforming cell between a second anode and a second cathode, said second cathode being a rotating cathode, and applying an effective amount of voltage across said second anode and said second cathode to deposit copper foil on said second cathode; and

(J) removing said copper foil from said second cathode.

3. The process of claim 1 with the step of:

(H'"'"') calcining said copper metal powder from step (G) to form cupric oxide, cuprous oxide, or a mixture thereof.

4. The process of claim 3 with the steps of:

(H) dissolving said cupric oxide, cuprous oxide or mixture thereof in an aqueous sulfuric acid solution to form a second electrolyte solution;

(I) flowing said second electrolyte solution in an electroforming cell between a second anode and a second cathode, said second cathode being a rotating cathode, and applying an effective amount of voltage across said second anode and said second cathode to deposit copper foil on said second cathode; and

(J) removing copper foil from said second cathode.

5. The process of claim 1 with the step of

(H") heat treating said copper metal powder from step (G) in a reducing atmosphere at a temperature below about 375°

C.

6. The process of claim 1 wherein said extractant in step (B) comprises (i) at least one oxime characterized by a hydrocarbon linkage with at least one --OH group and at least one ═

NOH group attached to different carbon atoms on said hydrocarbon linkage, (ii) at least one betadiketone, or (iii) at least one ion-exchange resin.

7. The process of claim 1 wherein said first electrolyte solution in step (F) is characterized by the presence of at least one triazole.

8. The process of claim 1 wherein said first electrolyte solution in step (F) is characterized by the presence of benzotriazole.

9. The process of claim 1 wherein said first anode in step (F) is a dimensionally stable insoluble anode.

10. The process of claim 1 wherein said first anode in step (F) a titanium anode that is coated with a platinum family metal or metal oxide.

11. The process of claim 1 wherein the concentration of free chloride ions in said first electrolyte solution in step (F) is up to about 2 ppm.

12. The process of claim 1 wherein said first electrolyte solution formed in step (E) has a copper ion concentration in the range of about 2 to about 60 grams per liter and a free sulfuric acid concentration in the range of about 70 to about 290 grams per liter.

13. A process for making copper metal powder from a copper-bearing material, comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B) contacting said copper-rich aqueous leaching solution with an effective amount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution;

(C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution;

(D) contacting said copper-rich extractant with an effective amount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant;

(E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution;

(F) advancing said first electrolyte solution into an electrolytic cell equipped with at least one first anode and at least one first cathode, said electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode;

(G) removing copper metal powder from said first cathode;

(H) dissolving said copper powder from step (G) in an aqueous sulfuric acid solution to form a second electrolyte solution;

(I) flowing said second electrolyte solution in an electroforming cell between a second anode and a second cathode, said second cathode being a rotating cathode, and applying an effective amount of voltage across said second anode and said second cathode to deposit copper foil on said second cathode; and

(J) removing said copper foil from said second cathode.

14. The process of claim 13 wherein said second electrolyte solution has a copper ion concentration in the range of about 40 to about 150 grams per liter and a free sulfuric acid concentration in the range of about 70 to about 170 grams per liter.

15. The process of claim 13 with the step of applying to at least one side of said foil from step (J) at least one roughened layer of copper or copper oxide.

16. The process of claim 13 with the step of applying to at least one side of said foil from step (J) at least one metallic layer, the metal in said metallic layer being selected from the group consisting of indium, zinc, tin, nickel, cobalt, copper-zinc alloy and copper-tin ahoy.

17. The process of claim 13 with the step of applying to at least one side of said foil from step (J) at least one metallic layer, the metal in said metallic layer being selected from the group consisting of tin, chromium, and chromium-zinc alloy.

18. The process of claim 13 with the steps of applying to at least one side of said foil from step (J) at least one roughened layer of copper or copper oxide, then applying to said roughened layer at least one first metallic layer, the metal in said first metallic layer being selected from the group consisting of indium, zinc, tin, nickel, cobalt, copper-zinc alloy and copper-tin alloy, then applying to said first metallic layer at least one second metallic layer, the metal in said second metallic layer being selected from the group consisting of tin, chromium, and chromium-zinc alloy.

19. A process for making copper metal powder from a copper-bearing material, comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B) contacting said copper-rich aqueous leaching solution with an effective amount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution;

(C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution;

(D) contacting said copper-rich extractant with an effective amount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant;

(E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution;

(F) advancing said first electrolyte solution into an electrolytic cell equipped with at least one first anode and at least one first cathode, said electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode;

(G) removing copper metal powder from said first cathode;

(H'"'"') calcining said copper metal powder from step (G) to form cupric oxide, cuprous oxide, or a mixture thereof;

(H) dissolving said cupric oxide, cuprous oxide or mixture thereof from step (H'"'"') in an aqueous sulfuric acid solution to form a second electrolyte solution;

(I) flowing said second electrolyte solution in an electroforming cell between a second anode and a second cathode, said second cathode being a rotating cathode, and applying an effective amount of voltage across said second anode and said second cathode to deposit copper foil on said second cathode; and

(J) removing copper foil from said second cathode.

20. The process of claim 19 wherein said second electrolyte solution has a copper ion concentration in the range of about 40 to about 150 grams per liter and a free sulfuric acid concentration in the range of about 70 to about 170 grams per liter.

21. The process of claim 19 with the step of applying to at least one side of said foil from step (J) at least one roughened layer of copper or copper oxide.

22. The process of claim 19 with the step of applying to at least one side of said foil from step (J) at least one metallic layer, the metal in said metallic layer being selected from the group consisting of indium, zinc, tin, nickel, cobalt, copper-zinc alloy and copper-tin alloy.

23. The process of claim 19 with the step of applying to at least one side of said foil from step (J) at least one metallic layer, the metal in said metallic layer being selected from the group consisting of tin, chromium, and chromium-zinc alloy.

24. The process of claim 19 with the steps of applying to at least one side of said foil from step (J) at least one toughened layer of copper or copper oxide, then applying to said roughened layer at least one first metallic layer, the metal in said first metallic layer being selected from the group consisting of indium, zinc, tin, nickel, cobalt, copper-zinc alloy and copper-tin alloy, then applying to said first metallic layer at least one second metallic layer, the metal in said second metallic layer being selected from the group consisting of tin, chromium, and chromium-zinc alloy.

25. A process for making copper metal powder from a copper-bearing material, said process including sequential steps (A), (B-1), (C-1), (B-2), (C-2), (E), (F) and (G), said process comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B-1) contacting said copper-rich aqueous leaching solution with an effective amount of at least one copper-bearing water-insoluble extractant from step (C-2) to transfer copper ions from said copper-rich aqueous leaching solution to said copper-bearing extractant to form a copper-rich extractant and a first copper-depleted aqueous leaching solution;

(C-1) separating said copper-rich extractant from said first copper-depleted aqueous leaching solution, advancing said copper-rich extractant to step (D);

(B-2) contacting said first copper-depleted aqueous leaching solution from step (C-1) with an effective amount of at least one copper-depleted extractant from step (E) to transfer copper ions from said first copper-depleted aqueous leaching solution to said copper-depleted extractant to form a copper-bearing extractant and a second copper-depleted aqueous leaching solution;

(C-2) separating said copper-bearing extractant from said second copper-depleted aqueous leaching solution, recirculating said copper-bearing extractant to step (B-1);

(D) contacting said copper-rich extractant from step (C-1) with an effective mount of at least one aqueous stripping solution to transfer copper ions from said copper-rich extractant to said stripping solution to form a first electrolyte solution and a copper-depleted extractant;

(E) separating said first electrolyte solution from said copper-depleted extractant, recirculating said copper-depleted extractant to step (B-2);

(F) advancing said first electrolyte solution to an electrolytic cell equipped with at least one first anode and at least one first cathode, said first electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective mount of voltage across said first anode and said first cathode to deposit copper powder on said first cathode; and

(G) removing copper metal powder from said first cathode.

26. A process for making copper foil from a copper-bearing material, said process including sequential steps (A), (B-1), (C-1), (B-2), (C-2), (D), (E), (F), (G), (H), (I) and (J), said process comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B-1) contacting said copper-rich aqueous leaching solution from step (A) with an effective mount of at least one copper-bearing water-insoluble extractant from step (C-2) to transfer copper ions from said copper-rich aqueous leaching solution to said copper-bearing extractant to form a copper-rich extractant and a first copper-depleted aqueous leaching solution;

(C-1) separating said copper-rich extractant from said first copper-depleted aqueous leaching solution, advancing said copper-rich extractant to step (D);

(B-2) contacting said first copper-depleted aqueous leaching solution from step (C-1) with an effective mount of at least one copper-depleted extractant from step (E) to transfer copper ions from said first copper-depleted aqueous leaching solution to said copper-depleted extractant to form a copper-bearing extractant and a second copper-depleted aqueous leaching solution;

(C-2) separating said copper-bearing extractant from said second copper-depleted aqueous leaching solution, recirculating said copper-bearing extractant to step (B-1);

(D) contacting said copper-rich extractant from step (C-1) with an effective mount of at feast one aqueous stripping solution to transfer copper ions from said copper-rich extractant to said stripping solution to form a first electrolyte solution and a copper-depleted extractant;

(E) separating said first electrolyte solution from said copper-depleted extractant, recirculating said copper-depleted extractant to step (B-2);

(F) advancing said first electrolyte solution from step (E) to an electrolytic cell equipped with at least one first anode and at least one first cathode, said first electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective mount of voltage across said first anode and said first cathode to deposit copper powder on said first cathode;

(G) removing copper powder from said first cathode;

(H) dissolving said copper powder from step (G) in a sulfuric acid solution to form a second electrolyte solution and placing said second electrolyte solution in an electroforming cell equipped with a second anode and a second cathode, said second cathode being a rotating cathode;

(I) flowing said second electrolyte solution between said second anode and second cathode, and applying an effective amount of voltage across said second anode and second cathode to deposit copper foil on said second cathode; and

(J) removing said copper foil from said second cathode.

27. A process for making cuprous oxide, cupric oxide or a mixture thereof from a copper-bearing material, said process including sequential steps (A), (B-1), (C-1), (B-2), (C-2), (D), (E), (F), (G) and (H'"'"'), said process comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B-1) contacting said copper-rich aqueous leaching solution from step (A) with an effective amount of at least one copper-bearing water-insoluble extractant from step (C-2) to transfer copper ions from said copper-rich aqueous leaching solution to said copper-bearing extractant to form a copper-rich extractant and a first copper-depleted aqueous leaching solution;

(C-1) separating said copper-rich extractant from said first copper-depleted aqueous leaching solution, advancing said copper-rich extractant to step (D);

(B-2) contacting said first copper-depleted aqueous leaching solution from step (C-1) with an effective amount of at least one copper-depleted extractant from step (E) to transfer copper ions from said first copper-depleted aqueous leaching solution to said copper-depleted extractant to form a copper-bearing extractant and a second copper-depleted aqueous leaching solution;

(C-2) separating said copper-bearing extractant from said second copper-depleted aqueous leaching solution, recirculating said copper-bearing extractant to step (B-1);

(D) contacting said copper-rich extractant from step (C-1) with an effective mount of at least one aqueous stripping solution to transfer copper ions from said copper-rich extractant to said stripping solution to form a first electrolyte solution and a copper-depleted extractant;

(E) separating said first electrolyte solution from said copper-depleted extractant, recirculating said copper-depleted extractant to step (B-2);

(F) advancing said first electrolyte solution from step (E) into an electrolytic cell equipped with at least one first anode and at least one first cathode, said first electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective mount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode;

(G) removing copper metal powder from said first cathode; and

(H'"'"') calcining said copper metal powder at a sufficient temperature and for an effective period of time to form cuprous oxide, cupric oxide or a mixture thereof.

28. A process for making copper foil from a copper-bearing material, said process including sequential steps (A), (B-1), (C-1), (B-2), (C-2), (D), (E), (F), (G), (H'"'"'), (H), (I) and (J), said process comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B-1) contacting said copper-rich aqueous leaching solution from step (A) with an effective mount of at least one copper-bearing water-insoluble extractant from step (C-2) to transfer copper ions from said copper-rich aqueous leaching solution to said copper-bearing extractant to form a copper-rich extractant and a first copper-depleted aqueous leaching solution;

(C-1) separating said copper-rich extractant from said first copper-depleted aqueous leaching solution, advancing said copper-rich extractant to step (D);

(B-2) contacting said fast copper-depleted aqueous leaching solution from step (C-1) with an effective mount of at least one copper-depleted extractant from step (E) to transfer copper ions from said first copper-depleted aqueous leaching solution to said copper-depleted extractant to form a copper-bearing extractant and a second copper-depleted aqueous leaching solution;

(C-2) separating said copper-beating extractant from said second copper-depleted aqueous leaching solution, recirculating said copper-bearing extractant to step (B-1);

(D) contacting said copper-rich extractant from step (C-1) with an effective amount of at least one aqueous stripping solution to transfer copper ions from said copper-rich extractant to said stripping solution to form a first electrolyte solution and a copper-depleted extractant;

(E) separating said first electrolyte solution from said copper-depleted extractant, recirculating said copper-depleted extractant to step (B-2);

(F) advancing said first electrolyte solution from step (E) into an electrolytic cell equipped with at least one first anode and at least one first cathode, said first electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode;

(G) removing copper metal powder from said first cathode;

(H'"'"') calcining said copper metal powder to form cuprous oxide, cupric oxide or a mixture thereof; and

(H) dissolving said cuprous oxide, cupric oxide or mixture thereof from step (H'"'"') in a sulfuric acid solution to form a second electrolyte solution and placing said second electrolyte solution in an electroforming cell equipped with a second anode and a second cathode, said second cathode being a rotating cathode;

(I) flowing said second electrolyte solution between said second anode and second cathode, and applying an effective amount of voltage across said second anode and second cathode to deposit copper foil on said second cathode; and

(J) removing said copper foil from said second cathode.

29. A process for making copper metal powder from a copper-bearing material, said process including sequential steps (A), (B-1), (C-1), (B-2), (C-2), (E), (F) and (G), said process comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B-1) contacting said copper-rich aqueous leaching solution with an effective mount of at least one copper-bearing water-insoluble extractant from step (C-2) to transfer copper ions from said copper-rich aqueous leaching solution to said copper-bearing extractant to form a copper-rich extractant and a first copper-depleted aqueous leaching solution;

(C-1) separating said copper-rich extractant from said first copper-depleted aqueous leaching solution, advancing said copper-rich extractant to step (D);

(B-2) contacting said first copper-depleted aqueous leaching solution from step (C-1) with an effective amount of at least one copper-depleted extractant from step (E) to transfer copper ions from said first copper-depleted aqueous leaching solution to said copper-depleted extractant to form a copper-bearing extractant and a second copper-depleted aqueous leaching solution.

(C-2) separating said copper-bearing extractant from said second copper-depleted aqueous leaching solution, recirculating said copper-bearing extractant to step (B-1);

(D) contacting said copper-rich extractant from step (C-1) with an effective mount of at least one aqueous stripping solution to transfer copper ions from said copper-rich extractant to said stripping solution to form a first electrolyte solution and a copper-depleted extractant;

(E) separating said first electrolyte solution from said copper-depleted extractant, recirculating said copper-depleted extractant to step (B-2);

(F) advancing said first electrolyte solution to an electrolytic cell equipped with at least one first dimensionally stable insoluble anode and at least one first cathode, said first electrolyte solution being characterized by the presence of at least one triazole and by a free chloride concentration of up to about 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper powder on said first cathode; and

(G) removing copper metal powder from said first cathode.

30. A process for making copper metal powder from a copper-bearing material, comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B) contacting said copper-rich aqueous leaching solution with an effective amount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution;

(C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution;

(D) contacting said copper-rich extractant with an effective amount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant;

(E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution;

(F) advancing said first electrolyte solution into an electrolytic cell equipped with at least one first anode and at least one first cathode, said electrolyte solution being characterized by the presence of at least one triazole and a free chloride concentration of up to 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode; and

(G) removing copper metal powder from said first cathode.

31. A process for making copper metal powder from a copper-bearing material, comprising:

(A) contacting said copper-bearing material with an effective amount of at least one aqueous leaching solution to dissolve copper ions in said leaching solution and form a copper-rich aqueous leaching solution;

(B) contacting said copper-rich aqueous leaching solution with an effective amount of at least one water-insoluble extractant to transfer copper ions from said copper-rich aqueous leaching solution to said extractant to form a copper-rich extractant and a copper-depleted aqueous leaching solution;

(C) separating said copper-rich extractant from said copper-depleted aqueous leaching solution;

(D) contacting said copper-rich extractant with an effective amount of at least one aqueous stripping solution to transfer copper ions from said extractant to said stripping solution to form a copper-rich stripping solution and a copper-depleted extractant;

(E) separating said copper-rich stripping solution from said copper-depleted extractant to form a first electrolyte solution;

(F) advancing said first electrolyte solution into an electrolytic cell equipped with at least one first anode and at least one first cathode, said electrolyte solution being characterized by a free chloride concentration of up to about 5 ppm, and applying an effective amount of voltage across said first anode and said first cathode to deposit copper metal powder on said first cathode;

(G) removing copper metal powder from said first cathode; and

(H'"'"') calcining said copper metal powder from step (G) to form cupric oxide, cuprous oxide, or a mixture thereof.