Separation and recovery of copper metal from ammoniacal solutions

Abstract

Copper is recovered from solutions containing cupric ammoniacal complexes by reducing copper in the complexes to the cuprous state and thereafter precipitating the copper as cuprous acetylide by passing acetylene through the solution. After the cuprous acetylide is separated from the solution and washed thoroughly, it is reacted with acetonitrile and an acid to form acetylene and a cuprous-acetonitrile complex: Cu(CH.sub.3 CN).sub.2.sup.+. The solution containing this complex is then flash distilled to remove the acetonitrile and to disproportionate unstable cuprous ions into copper metal and cupric ions. Following the disproportionation, the components are separated and copper metal is collected. SUBACKGROUND OF THE INVENTIONThis invention relates to the recovery of copper from ammoniacal solution which may also contain nickel, cobalt, and other ions. In practicing the invention, very pure copper metal is obtained without the need to employ ion exchangers, acid stripping, electrowinning, or electrorefining.It is known that copper (as well as nickel and cobalt) can be leached from the ores with ammoniacal leach liquors. One method of separating the copper values from such leach liquors while leaving the nickel and other metals in the raffinate, is disclosed in U.S. Pat. No. 2,440,612 to M. Lichtenwalter entitled Separation of Copper. In accordance with the process disclosed therein, the copper is recovered from the ammoniacal leach solutions by first reducing the copper values to the cuprous state and then precipitating the reduced copper by reacting it with acetylene to yield insoluble copper actylide which may be separated from the solution by filtration. If silver, mercury, or gold components are present in the leaching solution with the copper, these will also be precipitated out.In addition to the above process, it is known that solutions of cuprous salts can be thermally or electrochemically disproportionated to produce copper and solutions of cupric salts. This method is disclosed in U.S. Pat. No. 3,865,744 to Alan J. Parker et al. In general, this method involves reacting a cuprous salt with a ligand, i.e., an organic nitrile, to form a cuprous nitrile complex such as Cu(CH.sub.3 CN).sub.2.sup.+. The solution containing the complex can then be distilled to produce copper powder, a cupric salt, and an organic nitrile.The present invention provides a method of isolating and purifying copper utilizing a novel combination of the above two known copper recovering processes.SUMMARY OF THE INVENTIONThe process of the present invention produces copper metal from an ammoniacal solution containing cuprous ions. The process comprises the steps of precipitating the cuprous ions from the ammoniacal solution as a cuprous acetylide, separating and washing the cuprous acetylide precipitate, acid hydrolyzing the cuprous acetylide in the presence of a cuprous ion stabilizing ligand, e.g., a nitrile, and disproportionating the resulting cuprous complex to produce copper metal and cupric salt.The process of the present invention is characterized by the use of reactions which take place at or near ambient temperatures and pressures, and thus a system for utilizing the process can be built at a relatively low cost. In addition, many of the reagents in the process can be recycled, allowing further cost savings, and the process is quite energy efficient. Also, upwards of 99% of the available copper can be recovered and the product metal is of very high purity.Accordingly, it is an object of the present invention to provide a process for obtaining pure copper from ammoniacal copper containing solutions which avoids the necessity of electrowinning the copper, is capable of continuous operation on an industrial scale with a relatively low capital outlay, involves reactions which occur at or near ambient temperatures and pressures, and employs reagents which are neither unduly corrosive nor consumed.Another object of the invention is to provide such a copper recovery process which is energy efficient and significantly diminishes the quantities of waste involved when compared with prior art processes by regenerating and recycling reagents.Still another object of the invention is to quantitatively separate copper from ammoniacal solutions containing copper and other metals such as nickel, cobalt, iron, manganese, etc., without using an ion exchanger.Another object of the invention is to produce copper of very high purity by precipitating cuprous ions from solutions as a cuprous acetylide, separating the cuprous acetylide precipitate, reacting the acetylide with an acid and a nitrile to form a cuprous-nitrile complex, and disproportionating the cuprous ion to produce copper metal.

Description

Claims

1. A process for producing copper metal from a solution containing Cu.sup.+ ions comprising the steps of:

a. precipitating the Cu.sup.+ ions from the solution as a cuprous acetylide;

b. separating the cuprous acetylide precipitate from the solution;

c. reacting the cuprous acetylide with an acid and a nitrile to form a soluble cuprous-nitrile complex;

d. removing the nirile from the complex and disproportionating the Cu.sup.+ ion to produce copper metal and Cu.sup.++ ions.

2. The process as set forth in claim 1 wherein step (a) is effected by passing gaseous C.sub.2 H.sub.2 through anammoniacal solution of cuprous ions.

3. The process as set forth in claim 1 wherein step (a) is effected by passing an acetylenic compound having the formula RC.tbd.CH, where R is an alkyl group having 1-6 carbon atoms, through an ammoniacal solution of cuprous ions.

4. The process as set forth in claim 1 wherein step (a) is effected by passing 3, 3 dimethyl-1-butyne through the solution.

5. The process as set forth in claim 1 wherein the nitrile reacted in step (c) is CH.sub.3 CN.

6. The process as set forth in claim 1 wherein a member selected from the group consisting of methanol, ethanol, acetone, and mixtures thereof is added to the cuprous-nitrile to form an azeotrope and to aid in the formation of the soluble nitrile in step (c).

7. The process as set forth in claim 1 wherein the solution of Cu.sup.+ ions in step (a) comprises an aqueous ammoniacal solution containing the complex cuprous ammine ion Cu(NH.sub.3).sub.2.sup.+.

8. The process as set forth in claim 1 wherein said solution is a basic solution and contains an anion chosen from the group consisting of OH.sup.-, Cl.sup.-, SO.sub.4.sup.=, NO.sub.3.sup.-, C.sub.2 H.sub.3 O.sub.2.sup.-, CO.sub.3.sup.=, PO.sub.4.sup..tbd., HCO.sub.3.sup.-, HPO.sub.4.sup.=, H.sub.2 PO.sub.4.sup.-, and mixtures thereof.

9. The process as set forth in claim 8 wherein said solution contains the SO.sub.4.sup.= anion.

10. The process as set forth in claim 1 wherein step (d) is effected by distillation of the cuprous-nitrile complex.

11. The process as set forth in claim 1 wherein an acetylenic compound is produced in step (c) and is reused in step (a).

12. The process as set forth in claim 1 wherein nitrile is produced in step (d) and is reused in step (c).

13. The process as set forth in claim 1 wherein in step (c) the cuprous acetylide is reacted with an acid and 2-hydroxy-cyanoethane and wherein in step (d) the copper metal is produced by one electron electrowinning.

14. The process as set forth in claim 13 wherein acid is produced during the electrowinning of step (d) and is reused in step (c).

15. The process as set forth in claim 14 wherein acidis produced during the electrowinning of step (e) and is reused to dissolve acetylide in step (d).

16. A process for producing copper metal from a solution containing Cu(NH.sub.3).sub.4.sup.++ comprising the steps of:

a. reducing the Cu(NH.sub.3).sub.4.sup.++ to Cu(NH.sub.3).sub.2.sup.+ ;

b. precipitating the Cu.sup.+ from the Cu(NH.sub.3).sub.2.sup.+ ion as a cuprous acetylide;

c. separating the cuprous acetylide from the solution;

d. reacting the cuprous acetylide with an acid and a nitrile to form a cuprous nitrile complex;

e. removing the nitrile from the complex to disproportionate the Cu.sup.+ to produce copper metal and Cu.sup.++ ions.

17. The process of claim 16 wherein step (a) is effected by contacting the Cu(NH.sub.3).sub.4.sup.++ with CO.

18. The process of claim 16 wherein step (b) is effected by passing gaseous C.sub.2 H.sub.2 through the solution of cuprous ions.

19. The process of claim 16 wherein step (b) is effected by passing an acetylenic compound having the formula RC.tbd.CH, where R is an alkyl roup having 1-6 carbon atoms, through the solution.

20. The process of claim 16 wherein step (b) is effected by passing 3, 3 dimethyl-1-butyne through the solution.

21. The process of claim 16 wherein the nitrile is CH.sub.3 CN.

22. The process of claim 16 wherein a substance chosen from the group consisting of methanol, ethanol, acetone, and mixtures thereof is added to the cuprous-nitrile to form an azeotrope and to aid in dissolution of acetylide in step (d).

23. The process of claim 16 wherein said solution is a basic solution and contains an anion chosen from the group consisting of OH.sup.31, Cl.sup.31, SO.sub.4.sup.30, NO.sub.3.sup.31, C.sub.2 H.sub.3 O.sub.2.sup.31, CO.sub.3.sup.32, PO.sub.4.sup.32, and mixtures thereof.

24. The process of claim 16 wherein step (e) is effected by distillation of the cuprous-nitrile complex.

25. The process of claim 16 wherein an acetylenic compound is produced in step (d) and is resued in step (b).

26. The process of claim 16 wherein nitrile is produced in step (e) and reused in step (d).

27. The process as set forth in claim 16 wherein in step (d) the cuprous acetylide is reacted with an acid and 2-hydroxy-cyanoethane and wherein in step (e) the copper metal is produced by one electron electrowinning.

28. A process for producing copper metal from a solution containing Cu.sup.++ ions comprising the steps of:

a. reducing the Cu.sup.++ ions to Cu.sup.+ ions in the presence of ammonia;

b. precipitating the Cu.sup.+ as Cu.sub.2 C.sub.2 ;

c. separating the Cu.sub.2 C.sub.2 from the solution;

d. reacting the Cu.sub.2 C.sub.2 with acetonitrile and sulfuric acid to form a solution containing a cuprous acetonitrile complex;

e. removing the acetonitrile from said complex in solution to disproportionate the Cu.sup.+ and to form Cu.sup.o and Cu.sup.++.

29. The process of claim 28 wherein step (a) is effected by passing CO through the solution.

30. The process of claim 28 wherein step (b) is effected by passing C.sub.2 H.sub.2 through the Cu.sup.+ containing solution.

31. The process of claim 28 wherein C.sub.2 H.sub.2 is produced in step (d) and reused in step (b).

32. The process of claim 28 wherein acetonitrile is produced in step (e) and reused in step (d).