Leaching Copper-Containing Ores

Abstract

A method of leaching copper-containing ores includes leaching copper-containing ores or concentrates or tailings of the ores or concentrates with a leach liquor in the presence of an additive that enhances the dissolution of copper from copper minerals in the ores and concentrates by forming a complex between (a) sulfur, that has originated from copper minerals in the ores, and (b) the additive. A method of leaching copper-containing ores includes leaching copper-containing ores or concentrates or tailings of the ores or concentrates with a leach liquor includes leaching copper-containing ores or concentrates or tailings of the ores or concentrates with a leach liquor in the presence of a nitrogen-containing organic complexing additive that forms a complex between sulfur, that has originated from copper minerals in the ores, and the additive.

Claims

1. A method of leaching copper-containing ores containing chalcopyrite and/or enargite, concentrates of the ores, or tailings of the ores or the concentrates, comprising leaching the copper-containing ores containing chalcopyrite and/or enargite, the concentrates of the ores, or the tailings of the ores or the concentrates with a leach liquor in the presence of an additive that enhances dissolution of copper from copper minerals in the ores and the concentrates by forming a complex between (a) sulfur, that has originated from copper minerals in the ores, and (b) the additive, wherein the concentration of the additive is up to 10 g/L in the leach liquor, and wherein leaching includes controlling the pH of the leach liquor to be less than 2.5.

2. The method according to claim 1, wherein the complex comprises sulfur from the copper minerals and the additive, with the additive breaking down a passivating layer or reducing a formation of a passivating layer and therefore increasing access for leaching copper from copper minerals during the method.

3. The method according to claim 1, wherein the additive comprises a nitrogen-containing complexing agent that includes at least two nitrogen atoms spaced by two carbon atoms to permit the additive to form complexes between sulfur, that has originated from copper minerals in the ores, and the additive.

4. The method according to claim 1, wherein the additive is a compound that contains molecular scaffold (I) or a polymer that contains molecular scaffold (I) repeated through the polymer: ##STR00005## wherein, the two nitrogen atoms are each independently substituted or unsubstituted, each nitrogen atom is selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amino group; the two carbon atoms may each be substituted or unsubstituted; the bonds between the nitrogen atoms and carbon atoms in the scaffold may be single bonds or multiple bonds; and the bonds between the two carbon atoms in the scaffold may be single bonds or multiple bonds.

5. The method according to claim 1, wherein the additive is a compound of formula (II) or a polymer formed from two of more monomers of formula (III): ##STR00006## wherein, in formula (II) and (III), R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, or alkylamino groups, or the substituents on each of the two nitrogens together form an alkyl or alkynyl group that connect the two nitrogens to form a ring; R.sup.7, R.sup.8, R.sup.9 and R.sup.10 are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl or alkynyl, OC(O)R where R is alkyl, alkenyl or alkynyl, amino, alkylamino, alkenylamino, alkynylamino, C(O)NH.sub.2, C(O)NHR where R is alkyl, alkenyl or alkynyl, C(O)NR.sub.2 where R is alkyl, alkenyl or alkynyl, or R.sup.7 and R.sup.8 together and/or R.sup.9 and R.sup.10 together may be selected from O, NH, or NH where R is alkyl, alkenyl or alkynyl; and in formula (III), R.sup.1 or R.sup.2 are each independently selected from the groups defined for R.sup.1 and R.sup.2 above or are connected to another monomer of formula (III).

6. (canceled)

7. The method according to claim 1, wherein leaching includes controlling the temperature to be less than 100 C.

8. The method according to claim 1, wherein leaching includes controlling the temperature to be at least 5 C.

9. The method according to claim 1, wherein leaching includes controlling the oxidation potential of the leach liquor during an active leaching phase to be less than 900 mV, wherein the oxidation potential is determined with respect to a standard hydrogen electrode.

10. (canceled)

11. The method according to claim 1, wherein leaching includes controlling the pH of the leach liquor to be greater than 0.5.

12. The method according to claim 1, wherein leaching includes bioleaching with microorganisms to assist leaching of copper.

13. The method according to claim 1, wherein leaching includes adding chemical oxidants to the leach liquor.

14. The method according to claim 1, includes recovering copper from the leach liquor in downstream copper recovery steps.

15. The method according to claim 1, includes adding the additive to the leach liquor continuously or periodically during the method to maintain a required concentration during the method.

16. The method according to claim 1, includes adding the additive to ore fragments prior to the leaching.

17. The method according to claim 16, includes forming agglomerates of ore fragments and adding the additive to agglomerates prior to the leaching.

18. The method according to claim 16, includes forming agglomerates of ore fragments and adding the additive while forming agglomerates.

19. The method according to claim 16, includes forming agglomerates of ore fragments, wherein the additive is polyethylenimine (PEI), and the forming agglomerates includes: (a) forming a PEI solution having a pH greater than pH 4.5; (b) optionally heating the solution to at least 50 C. to speed up dissolution/dilution of the PEI; and (c) adding the PEI solution to ore fragments at the start of the forming agglomerates.

20. The method according to claim 1, includes regenerating the leach liquor and recycling the regenerated leach liquor to heap.

21. The method according to claim 20, includes adjusting the concentration of the additive in the regenerated leach liquor to maintain a concentration of up to 10 g/L in the leach liquor.

22. The method according to claim 20, includes adding or removing the additive to the regenerated leach liquor to maintain a concentration of up to 10 g/L in the leach liquor.

23. A method of leaching copper-containing ores, concentrates of the ores, or tailings of the ores or concentrates, that includes leaching the copper-containing ores, the concentrates or the tailings of the ores or the concentrates with a leach liquor in the presence of a nitrogen-containing organic complexing additive that forms a complex between sulfur, that has originated from copper minerals in the ores, and the additive wherein the additive is a degradation product that forms under conditions of the leach.

24. The method defined in claim 23, wherein the complex comprises sulfur in a passivating layer on copper minerals and the additive, with the complex breaking down the passivating layer or reducing formation of the layer and therefore allowing greater access for leaching copper from copper minerals during the method.

25. (canceled)

26. The method defined in claim 23, wherein the degradation product is a degradation product of another additive.

27. The method defined in claim 23, wherein the nitrogen-containing organic complexing additive includes at least two nitrogen atoms.

28. The method defined in claim 27 wherein each of the at least two nitrogen atoms in the additive is present as a primary amine group, a secondary amine group, or a tertiary amine group.

29. The method defined in claim 23 wherein the nitrogen-containing complexing additive includes at least two nitrogen atoms spaced by two carbon atoms to permit the additive to form the complex.

30. The method defined in claim 23 wherein the additive is a compound that contains molecular scaffold (I) or a polymer that contains molecular scaffold (I) repeated through the polymer: ##STR00007## wherein, the two nitrogen atoms are each independently substituted or unsubstituted, each nitrogen atom is selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amino group; the two carbon atoms may each be substituted or unsubstituted; the bonds between the nitrogen atoms and carbon atoms in the scaffold may be single bonds or multiple bonds; and the bonds between the two carbon atoms in the scaffold may be single bonds or multiple bonds; or the additive is a compound of formula (II) or a polymer formed from two of more monomers of formula (III): ##STR00008## wherein, in formula (II) and (III), R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, and alkylamino groups, or the substituents on each of the two nitrogens together form an alkyl or alkynyl group that connect the two nitrogens to form a ring; R.sup.7, R.sup.8, R.sup.9 and R.sup.10 are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl or alkynyl, OC(O)R where R is alkyl, alkenyl or alkynyl, amino, alkylamino, alkenylamino, alkynylamino, C(O)NH.sub.2, C(O)NHR where R is alkyl, alkenyl or alkynyl, C(O)NR.sub.2 where R is alkyl, alkenyl or alkynyl, or R.sup.7 and R.sup.8 together and/or R.sup.9 and R.sup.10 together may be selected from , NH or NH where R is alkyl, alkenyl or alkynyl; and in formula (III), R.sup.1 or R.sup.2 are each independently selected from the groups defined for R.sup.1 and R.sup.2 above or are connected to another monomer of formula (III).

31. A method of leaching copper-containing ores, concentrates of the ores, or tailings of the ores or the concentrates, comprising leaching the copper-containing ores, the concentrates of the ores, or the tailings of the ores or the concentrates with a leach liquor in the presence of an additive that enhances dissolution of copper from copper minerals in the ores and the concentrates by forming a complex between (a) sulfur, that has originated from copper minerals in the ores, and (b) the additive, wherein the additive is a compound of formula (II) or a polymer formed from two of more monomers of formula (III): ##STR00009## wherein, in formula (II) and (III), R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, and alkylamino groups, or the substituents on each of the two nitrogens together form an alkyl or alkynyl group that connect the two nitrogens to form a ring; R.sup.7, R.sup.8, R.sup.9 and R.sup.10 are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl or alkynyl, OC(O)R where R is alkyl, alkenyl or alkynyl, amino, alkylamino, alkenylamino, alkynylamino, C(O)NH.sub.2, C(O)NHR where R is alkyl, alkenyl or alkynyl, C(O)NR.sub.2 where R is alkyl, alkenyl or alkynyl, or R.sup.7 and R.sup.8 together and/or R.sup.9 and R.sup.10 together may be selected from O, NH or NH where R is alkyl, alkenyl or alkynyl; and in formula (III), R.sup.1 or R.sup.2 are each independently selected from the groups defined for R.sup.1 and R.sup.2 above or are connected to another monomer of formula (III).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0128] The present invention is described further with reference to the accompanying drawings of which:

[0129] FIG. 1 illustrates the steps in one embodiment of a method of heap leaching agglomerates of fragments of copper-containing ore that contains chalcopyrite and/or enargite with a leach liquor containing an additive in accordance with the present invention;

[0130] FIG. 2 illustrates the enhancement of copper dissolution from relatively pure chalcopyrite mineral grains with the addition of examples of additives in accordance with the invention, with this improvement resulting in copper extraction being higher than the baseline conditions where no additive was added to the test;

[0131] FIG. 3 illustrates cases where no enhancement of copper dissolution occurred from relatively pure chalcopyrite mineral grains with the addition of samples of additives that do not meet the requirements of the additives in accordance with the invention;

[0132] FIG. 4 illustrates cases where a negative enhancement of copper dissolution occurred from relatively pure chalcopyrite mineral grains with the addition of samples of additives that do not meet the requirements of the additives in accordance with the invention;

[0133] FIG. 5 illustrates the enhancement of copper dissolution from a low copper grade (<1.5 wt. %) ore sample leached at 50 C. with the addition of examples of additives in accordance with the invention, with this improvement resulting in copper extraction being higher than the baseline conditions where no additive was added to the test;

[0134] FIG. 6 illustrates the enhancement of arsenic dissolution from a low copper grade (<1.5 wt. %) ore sample leached at 50 C. with the addition of examples of additives in accordance with the invention, with this improvement resulting in arsenic extraction being higher than the baseline conditions where no additive was added to the test;

[0135] FIG. 7 illustrates the enhancement of copper dissolution from a low copper grade (<1.5 wt. %) ore sample leached at 30 C. with the addition of examples of additives in accordance with the invention, with this improvement resulting in copper extraction being higher than the baseline conditions where no additive was added to the test;

[0136] FIG. 8 illustrates the enhancement of arsenic dissolution from a low copper grade (<1.5 wt. %) ore sample leached at 30 C. with the addition of examples of additives in accordance with the invention, with this improvement resulting in arsenic extraction being higher than the baseline conditions where no additive was added to the test;

[0137] FIG. 9 is a graph of copper extraction profiles for a chalcopyrite/enargite ore sample leached with and without the addition of the additive polyethylenimine at 50 C.; and

[0138] FIG. 10 is a graph of arsenic extraction profiles for a chalcopyrite/enargite ore sample leached with and without the addition of the additive polyethylenimine at 50 C.

DESCRIPTION OF EMBODIMENT

[0139] The following description is in the context of heap leaching agglomerates of copper-containing ore fragments.

[0140] It is noted that not all of the experimental work that has been carried out is reported in the specification and that the overall results of the work are positive and indicate invention is applicable to tank, vat and heap leaching.

[0141] Further to the preceding paragraph, it is noted that the invention extends to heap, vat and tank leaching copper-containing ores that are in the form of fragments or in the form of agglomerates of fragments.

[0142] It is also noted that the invention also extends to heap, vat, and tank leaching concentrates of copper-containing ores, with the ore concentrates being in any suitable form, including unagglomerated and agglomerated forms.

[0143] It is also noted that the invention also extends to heap or vat or tank leaching tailings of the ores or concentrates produced for example in flotation or other downstream processing of ores or concentrates.

[0144] As noted above, the invention comprises leaching copper-containing ores or concentrates of the ores or tailings of the ores or concentrates with a leach liquor in the presence of an additive that enhances the dissolution of copper from copper minerals in the ores and concentrates by forming a complex between (a) sulfur, that has originated from copper minerals in the ore, and (b) the additive. Nitrogen-containing organic complexing additives are specific examples of the additive.

[0145] The flow sheet of FIG. 1 shows the steps in one embodiment of a method of heap leaching agglomerates of fragments of copper-containing ore that contains chalcopyrite and/or enargite with a leach liquor containing an additive in accordance with the invention.

[0146] The method includes the steps of forming agglomerates of copper containing ore in an agglomeration station 3, forming a heap 5 from the agglomerates, supplying a leach liquor 15 to the heap 5 and taking copper into solution, collecting leach liquor after it has passed through the heap, recovering copper from solution in the leach liquor from the heap in a copper recovery circuit 17, for example by solvent extraction, and regenerating the leach liquor from the heap and recycling the regenerated leach liquor to the heap.

[0147] With reference to FIG. 1, the following feed materials are transferred to the agglomeration station 3 and are mixed together and form agglomerates:

[0148] (a) fragments of copper containing ore that includes chalcopyrite and/or enargite that have been crushed to a suitable particle size distribution, identified by the numeral 7 in the Figure;

[0149] (b) optionally an activation agent, such as silver, in this embodiment as a silver solution (but could be in a solid form), typically having an added concentration of silver of less than 5 g silver per kg copper in the ore in the agglomerates, identified by the numeral 9 in the Figure;

[0150] (c) an acid, typically sulfuric acid, identified by the numeral 11 in the Figure in any suitable concentration; and

[0151] (d) microorganisms, identified by the numeral 13 in the Figure, of any suitable type and in any suitable concentration.

[0152] The agglomerates produced in the agglomeration station 3 are subsequently used in the construction of the heap 5.

[0153] For example, the agglomerates produced in the agglomeration station 3 may be transferred directly to a heap construction site. Alternatively, the agglomerates may be stockpiled and used as required for a heap. The agglomeration station 3 and the heap 5 are typically in close proximity However, this is not essential and may not be the case.

[0154] By way of example only, the heap may be a heap of the type described in International publication WO2012/031317 in the name of the applicant and the disclosure of the heap construction and leaching process for the heap in the International publication is incorporated herein by cross-reference.

[0155] In a heap leaching operation, copper in the chalcopyrite and other copper-containing minerals in the agglomerates is leached from the agglomerates in the heap 5 via the supply of the leach liquor 15 and is taken into solution in the leach liquor as the leach liquor passes through the heap 5.

[0156] The leached copper is recovered from the leach liquor in the downstream copper recovery circuit 17.

[0157] The recovered copper 19 is transferred for further processing and the leach liquor 23 is transferred to and regenerated in a regeneration circuit 21 and recycled to the heap 5 as leach liquor 15 to leach more copper from the chalcopyrite and other copper-containing minerals in the agglomerates in the heap 5.

[0158] The agglomeration station 3 may be any suitable construction that includes a drum, conveyor (or other device) for mixing the feed materials for the agglomerates and agglomerating the feed materials. The agglomeration conditions in the agglomeration station 3 are selected to form agglomerates of the required size and mechanical properties for the heap 5.

[0159] Mixing and agglomerating the feed materials for the agglomerates may occur simultaneously. Alternatively, mixing the feed materials may be carried out first and agglomerating (for example initiated by the addition of the acid) may be carried out after mixing has been completed to a required extent. Moreover, the timing of adding and then mixing and agglomerating feed materials may be selected to meet the end-use requirements for the agglomerates. For example, it may be preferable in some situations to start mixing fragments containing chalcopyrite and then adding silver in a solution or in a solid form of silver, acid, and microorganisms progressively in that order at different start and finish times in the agglomeration step. By way of particular example, it may be preferable in some situations to start mixing fragments containing chalcopyrite and then adding silver in a solution or in a solid form and acid together, and then adding microorganisms at different start and finish times in the agglomeration step.

[0160] The additives of the invention may be added to the leach liquor 15 in the required concentrations. Typically, the concentration of the additive is up to 10 g/L, up to 5 g/L, up to 2.5 g/L, up to 1.5 g/L, up to 1.25 g/L, or up to 1 g/L, in the leach liquor.

[0161] Alternatively, or in addition, the additives of the invention may be added during forming agglomerates in the agglomeration station 3.

[0162] The applicant has found that in situations where the additive is a polymer-like additive, such as longer chain organic substances, such as polyethylenimine (PEI), it may be preferred to add the additive while forming agglomerates in the agglomeration station 3 rather than adding the additive to leach liquor.

[0163] For example, one specific sequence of steps that has been found to be successful is as follows: [0164] Form a PEI solution of pH greater than 4.5. [0165] Ensure that the makeup solution does not contain constituents that can cause the precipitation/polymerization of the PEI. [0166] Optionally heat the solution to at least 50 C. to speed up the dissolution/dilution of the PEI. [0167] Add the PEI solution at the start of agglomerating ore fragments before any acids/raffinate/etc. are added.

[0168] As indicated above, a Group company of the applicant has carried out leach testing to investigate the impact of a number of additives in leach liquors on chalcopyrite mineral samples and chalcopyrite/enargite ores.

[0169] The leach tests are described in the Examples below.

EXAMPLES

[0170] As described above, test work conducted by a Group company of the applicant has shown that additives in the form of a nitrogen-containing organic complexing agent comprising two nitrogen atoms spaced by two carbon atoms can be used to enhance the dissolution of copper from copper-containing ores.

[0171] The additives tested include ethylenediamine, polyethylenimine, imidazole, bipyridyl, phenanthroline, 8-amineoquinoline, cysteine, glycine, arginine, picoline, putrescine, and spermidine.

[0172] The work has shown that additives ethylenediamine, polyethylenimine, and imidazole can be used to enhance the dissolution of copper from copper minerals in copper-containing ores.

[0173] Based on the test work and the experience of the inventors, it is expected that other compounds comprising at least two nitrogen atoms spaced by two carbon atoms, in particular compounds which are able to form a complex with sulfur that has originated from copper minerals in the ore, such as a complex with sulfur in a passivating layer on copper minerals in the ore, would have the same effect.

[0174] The test work using additive-containing liquor was conducted in small scale leaching reactors.

[0175] The following results were obtained with low grade chalcopyrite mineral samples containing greater than 90% chalcopyrite. Low grade describes ores containing less than 2 wt. % copper, this material was a mixture of chalcopyrite and enargite, plus some background secondary copper sulfide minerals.

[0176] 1 Reactor Test Work

[0177] 1.1 Experimental Procedure

[0178] Reactor leaching tests were all conducted at a pH less than 1.8, typically around 1.2. The oxidation potential of the solution was maintained at approximately 700 mV determined with respect to the standard hydrogen electrode to simulate conditions that may be seen when leaching copper ores. The examples in FIGS. 2, 3 and 4 involved the leaching of a chalcopyrite mineral sample containing approximately 90% chalcopyrite mineral, with the remainder being non-reactive gangue minerals. The copper grade in the sample was 29%. The initial leach solution was an acidified iron solution at 2 g/L Fe(III) added as a sulfate. These tests were maintained at 50 C. In these methods, additives ethylenediamine, polyethylenimine, and imidazole were tested separately. Specifically, 1 g/L of one of each additive was added to the start of each test.

[0179] 1.2 Impact of Additives

[0180] FIG. 2 is a graph that depicts copper extraction profiles (% extraction versus leach days) for chalcopyrite mineral samples leached with leach liquor containing additives ethylenediamine, polyethylenimine, and imidazole. The Figure also includes a copper extraction profile for a baseline test with the same leach liquor without an additive. FIG. 2 shows that there was an improvement observed for the leaching of chalcopyrite minerals with leach liquors in tests with the additives ethylenediamine, polyethylenimine, and imidazole compared to the results in the baseline test.

[0181] 1.3 Comparative Examples Showing Compounds that Do Not Improve Leaching

[0182] FIG. 3 is a graph that depicts copper extraction profiles for chalcopyrite mineral samples leached with leach liquors in tests with the additives cysteine, glycine, arginine, picoline, putrescine, spermidine, proline and ethanolamine The Figure also includes a copper extraction profile for a baseline test with the same leach liquor without an additive. The Figure shows that there was no improvement observed with the leach liquors containing the additives.

[0183] FIG. 4 is a graph that depicts copper extraction profiles for chalcopyrite mineral samples leached with leach liquors in tests with additives bipyridyl, phenanthroline, and 8-amineoquinoline. The Figure also includes a copper extraction profile for a baseline test with the same leach liquor without an additive. The Figure shows that there was a negative impact on leaching with the leach liquors containing the additives.

[0184] 2 Column Test Work

[0185] 2.1 Experimental Procedure

[0186] Column leaching tests were all conducted at a pH of less than 1.8, typically around 1.2. The examples in FIGS. 5, 6, 7 and 8 involved the leaching of a chalcopyrite and enargite ore sample containing approximately 1.3 wt. % copper and 0.07 wt. % arsenic, with approximately 8 wt. % pyrite and the remainder being non-sulfide gangue minerals. The initial leach solution was an acidified 5 g/L ferric iron solution (in the sulfate form). Iron and sulfur oxidizing moderate thermophile bacteria were added to maintain the oxidation potential between 650 and 700 mV determined with respect to the standard hydrogen electrode. In these methods, 1 g/L of the additive ethylenediamine was added at the start of each test.

[0187] 2.2 Impact of Additive

[0188] FIG. 5 is a graph that depicts copper extraction profiles for a chalcopyrite/enargite ore sample leached with (red squares) and without (blue crosses) the addition of the additive ethylenediamine at 50 C. The Figure also includes a copper extraction profile for the same leach liquor without an additive.

[0189] FIG. 6 is a graph that depicts arsenic extraction profiles for a chalcopyrite/enargite ore sample leached with (red squares) and without (blue crosses) the addition of the additive ethylenediamine at 50 C. The Figure also includes an arsenic extraction profile for the same leach liquor without an additive.

[0190] FIG. 7 is a graph that depicts copper extraction profiles for a chalcopyrite/enargite ore sample leached with (green triangles) and without (blue crosses) the addition of the additive ethylenediamine at 30 C. The Figure also includes a copper extraction profile for the same leach liquor without an additive.

[0191] FIG. 8 is a graph that depicts arsenic extraction profiles for a chalcopyrite/enargite ore sample leached with (green triangles) and without (blue crosses) the addition of the additive ethylenediamine at 30 C. The Figure also includes a copper extraction profile for the same leach liquor without an additive.

[0192] It is evident from each of FIGS. 5-8 that the additive ethylenediamine had a positive impact on leaching the chalcopyrite/enargite ore samples, with improvements observed in each Figure compared to the baseline results.

[0193] FIG. 9 is a graph that depicts copper extraction profiles for a chalcopyrite/enargite ore sample leached with (orange circles) and without (blue crosses) the addition of the additive polyethylenimine at 50 C. The Figure also includes a copper extraction profile for the same leach liquor without an additive.

[0194] FIG. 10 is a graph that depicts arsenic extraction profiles for a chalcopyrite/enargite ore sample leached with (orange circles) and without (blue crosses) the addition of the additive polyethylenimine at 50 C. The Figure also includes an arsenic extraction profile for the same leach liquor without an additive.

[0195] It is evident from each of FIGS. 9-10 that the additive polyethylenimine had a positive impact on leaching the chalcopyrite/enargite ore samples, with improvements observed in each Figure compared to the baseline results.

[0196] 3 Summary

[0197] The above Examples, particularly the Figures presenting the results of the experimental work in the Examples, illustrate the effectiveness of the use of additives in accordance with the invention.

[0198] The Examples indicate that some additives were successful, and some additives were not successful. The successful additives reported above are ethylenediamine, polyethylenimine, and imidazole. The unsuccessful additives reported above are bipyridyl, phenanthroline, 8-amineoquinoline, cysteine, glycine, arginine, picoline, putrescine, spermidine, proline and ethanolamine.

[0199] The applicant developed the above-described mechanism invention and additive-specific invention in the process of analysing the results of the above Examples and experimental work on the above-mentioned and other additives.

[0200] Specifically, the applicant identified characteristics of additives that make it possible to form complexes comprising (a) sulfur, that has originated from copper minerals in the ore, and (b) additives that can enhance leaching of copper-containing ores or concentrates of the ores.

[0201] Many modifications may be made to the invention as described above without departing from the spirit and scope of the invention.