REDUCTION OF CHALCOPYRITE BY AN AQUEOUS PHASE REDUCANT TO ENABLE HYDROMETALLURGICAL EXTRACTION OF COPPER

Abstract

A copper concentrate such as chalcopyrite is contacted with an aqueous solution includes acids and a reducing agent, such as vanadium (II) ions, chromium (II) ions, or tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40). The aqueous solution reduces the copper in the copper concentrate, which can then dissolve into the solution for recovery therefrom, or precipitate out of solution as copper compounds or elemental copper for recovery in as a solid phase product. The solid phase product can then be isolated, dissolved, and further electrowinned to recover a copper product from the copper concentrate. Oxidized reducing agent can be recovered in an electrochemical device with ferrous iron reactants. Hydrometallurgical routes to convert copper concentrates to copper are potentially less expensive and less polluting than current pyrometallurgical processing and an advantageous response to environmental and economic pressures for increased copper production.

Claims

1. A method of producing a copper product from a copper concentrate, the method comprising: providing a composition including a copper concentrate; contacting the composition with an aqueous solution including one or more chemical reducing agents; reacting at least a portion of the copper concentrate with the chemical reducing agent to reduce copper within the copper concentrate; and isolating a solid phase reaction product, the solid phase reaction product including a copper product.

2. The method according to claim 1, wherein the copper concentrate includes chalcopyrite.

3. The method according to claim 1, further comprising: contacting the solid phase reaction product with an acidic stream to produce a dissolved copper product, the acidic stream including one or more acids.

4. The method according to claim 3, wherein the acidic stream includes a concentration of iron (III) sulfate, sulfuric acid, or combinations thereof.

5. The method according to claim 3, electrowinning the dissolved copper product to isolate the copper product and a recycled acid.

6. The method according to claim 1, wherein the step of isolating a solid phase reaction product further comprises: isolating a liquid phase reaction product, the liquid phase reaction product including an oxidized chemical reducing agent; and feeding the liquid phase reaction product to an electrochemical device.

7. The method according to claim 6, further comprising: reducing the oxidized chemical reducing agent at the electrochemical device to a recycled chemical reducing agent; and contacting the recycled chemical reducing agent with the composition.

8. The method according to claim 6, further comprising: isolating a second copper product from the liquid phase reaction product.

9. The method according to claim 1, wherein the chemical reducing agents include vanadium (II) ions, compounds including vanadium (II) ions, chromium (II) ions, compounds including chromium (II) ions, tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40), or combinations thereof.

10. The method according to claim 9, the chemical reducing agents include vanadium (II) sulfate, chromium (II) chloride, or combinations thereof.

11. The method according to claim 1, wherein the step of isolating a solid phase reaction product further comprises: isolating a gaseous reaction product, the gaseous reaction product including hydrogen sulfide; contacting the gaseous reaction product with a stream of ferric iron to form a ferrous iron effluent stream and an elemental sulfur effluent stream; and recycling the ferrous iron effluent stream to the electrochemical device.

12. A system for producing a copper product from a copper concentrate, the system comprising: a source of copper concentrate; a reduction reactor in communication with the source of copper concentrate, the reduction reactor including: an acidic aqueous solution including one or more chemical reducing agents; and at least a first product outlet; a solid phase product outlet stream in communication with the first product outlet; a dissolution reactor in communication with one or more acid inlet streams and the solid phase product outlet stream, the dissolution reactor producing a dissolved copper product stream; and a copper isolation electrowinning reactor in fluid communication with the dissolved copper product stream, the copper isolation electrowinning reactor producing a copper product and a recycled acid stream in fluid communication with the dissolution reactor.

13. The system according to claim 12, wherein the copper concentrate includes chalcopyrite.

14. The system according to claim 12, wherein the chemical reducing agents include vanadium (II) ions, compounds including vanadium (II) ions, chromium (II) ions, compounds including chromium (II) ions, tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40), or combinations thereof.

15. The system according to claim 14, the chemical reducing agents include vanadium (II) sulfate, chromium (II) chloride, or combinations thereof.

16. The system according to claim 12, wherein the acid inlet stream includes a concentration of iron (III) sulfate, sulfuric acid, or combinations thereof.

17. The system according to claim 13, wherein the reduction reactor further comprises a second product outlet, and wherein the system further comprises: a liquid phase product outlet stream in fluid communication with the second product outlet, the liquid phase product stream including oxidized chemical reducing agent; an electrochemical device in fluid communication with the liquid phase outlet stream; and a recycled chemical reducing agent stream produced by the electrochemical device and in fluid communication with the reduction reactor.

18. The system according to claim 17, wherein the reduction reactor further comprises a third product outlet, and wherein the system further comprises: a gaseous phase product outlet stream in fluid communication with the third product outlet, the gaseous phase product outlet stream including hydrogen sulfide; a gaseous treatment reactor in fluid communication with the gaseous phase product outlet stream; a ferric iron feedstream provided from the electrochemical device to the gaseous treatment reactor; a ferrous iron feedstream provided from the gaseous treatment reactor to the electrochemical device; and an elemental sulfur effluent stream.

19. A method for indirect reduction of chalcopyrite, comprising: providing a composition including a concentration of chalcopyrite; contacting the composition with an acidic aqueous solution including one or more acids and one or more chemical reducing agents, wherein the one or more acids include sulfuric acid, hydrochloric acid, or combinations thereof, and wherein the one or more chemical reducing agents include vanadium (II) ions, compounds including vanadium (II) ions, chromium (II) ions, compounds including chromium (II) ions, tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40), or combinations thereof; reacting the chalcopyrite with the chemical reducing agents to reduce at least a portion of the copper included therein; separating a solids reaction product stream, a liquid reaction product stream, and a gaseous reaction product stream, wherein: the solids reaction product stream includes copper, copper compounds, or combinations thereof, the liquid reaction product stream includes oxidized chemical reducing agent, and the gaseous reaction product stream includes H.sub.2S; providing the oxidized chemical reducing agent to an electrochemical device; reducing the oxidized chemical reducing agent at the electrochemical device to a recycled chemical reducing agent; contacting the recycled chemical reducing agent with the composition; treating the gaseous reaction product stream with a concentration of ferric iron to generate a sulfur product and a concentration of ferrous iron; recycling the ferrous iron to the electrochemical device; contacting the solids reaction product stream with one or more acids to produce a dissolved copper product stream; and electrowinning the dissolved copper product stream to isolate a copper product and a recycled acid.

20. The method according to claim 19, wherein the acidic aqueous solution has a concentration of about 0.01M to about 10 M of reducing agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings show embodiments of the disclosed subject matter for the purpose of illustrating the invention. However, it should be understood that the present application is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

[0022] FIG. 1 is a chart of a method of producing a copper product from a copper concentrate according to some embodiments of the present disclosure;

[0023] FIG. 2 is a schematic representation of a system of producing a copper product from a copper concentrate according to some embodiments of the present disclosure;

[0024] FIG. 3 portrays a graph of the percent of Fe.sup.2+ released from chalcopyrite (CuFeS.sub.2) during the reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and 39 g/L of concentrate and direct reduction in 1MH.sub.2SO.sub.4;

[0025] FIG. 4 portrays a graph of x-ray diffraction (XRD) results for mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0026] FIG. 5 portrays a graph of XRD results for mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0027] FIG. 6A depicts pictures of mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0028] FIG. 6B portrays scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) results of mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0029] FIGS. 6C-6D portray XRD spectra for mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0030] FIG. 7 portrays a graph of XRD results for mineral products after 60 minutes of reaction between 1M VSO.sub.4, 39 g/L CuFeS.sub.2 concentrate, and various initial concentrations of H.sub.2SO.sub.4;

[0031] FIG. 8A portrays a graph of the release of Fe.sup.2+ ions to solution during the progression of the reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0032] FIG. 8B portrays a graph of the extraction of Cu.sup.2+ from mineral products by a solution comprising 1M H.sub.2SO.sub.4 and 0.5M Fe.sub.2(SO.sub.4).sub.3 subsequent to the reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate;

[0033] FIG. 9A portrays a graph of the release of Fe.sup.2+ ions to solution during the progression of the reaction between 1M VSO.sub.4, 39 g/L CuFeS.sub.2 concentrate, and various initial concentrations of H.sub.2SO.sub.4;

[0034] FIG. 9B portrays a graph of the extraction of Cu.sup.2+ from mineral products by a solution comprising 1M H.sub.2SO.sub.4 and 0.5M Fe.sub.2(SO.sub.4).sub.3 subsequent to the reaction between 1M VSO.sub.4, 39 g/L CuFeS.sub.2 concentrate, and various initial concentrations of H.sub.2SO.sub.4;

[0035] FIG. 10 depicts pictures of the reaction between 1M CrCl.sub.2, 4M HCl and 78 g/L of the CuFeS.sub.2 concentrate at a) 0 s, b) 2 s, c) 3 s, d) 5 s, and e) 1 min;

[0036] FIG. 11A portrays a graph of the release of Fe.sup.2+ ions to solution during the progression of the reaction between 1M CrCl.sub.2, 4M HCl, and various loadings of CuFeS.sub.2 concentrate;

[0037] FIG. 11B portrays a graph of the release of Fe.sup.2+ ions to solution during the progression of the reaction between 1M CrCl.sub.2, 39 g/L CuFeS.sub.2 concentrate, and various initial concentrations of HCl;

[0038] FIG. 12 depicts optical microscopy images of the mineral products after reaction between various chalcopyrite concentrate loadings, 1M CrCl.sub.2, and 4M HCl for 60 minutes;

[0039] FIG. 13 portrays a graph of XRD results for mineral products after reaction between various chalcopyrite concentrate loadings, 1M CrCl.sub.2, and 4M HCl for 60 minutes;

[0040] FIG. 14 portrays a graph of XRD results for mineral products after reaction between 39 g/L of the chalcopyrite concentrate with 1M CrCl.sub.2 and various initial concentrations of HCl for 60 minutes;

[0041] FIG. 15 depicts SEM images of mineral products after reaction with 1M CrCl.sub.2 and 4M HCl for 60 minutes;

[0042] FIG. 16 portrays a graph of EDS results for the mineral products after reaction with 1M CrCl.sub.2 and 4M HCl for 60 minutes;

[0043] FIG. 17A portrays a graph of XPS results for mineral products after reaction with 1M CrCl.sub.2 and 4M HCl for 60 minutes for Cu;

[0044] FIG. 17B portrays a graph of XPS results for mineral products after reaction with 1M CrCl.sub.2 and 4M HCl for 60 minutes for Cl;

[0045] FIG. 18 portrays a graph showing extraction of Cu.sup.2+ from mineral products by 0.5M Fe.sub.2(SO.sub.4).sub.3 subsequent to the reaction between 1M CrCl.sub.2, 4M HCl, and various loadings of CuFeS.sub.2 concentrate, and further between 1M CrCl.sub.2, 39 g/L CuFeS.sub.2 concentrate, and various initial concentrations of HCl; and

[0046] FIG. 19 portrays a graph summarizing the energy requirements for various metallurgical processes.

DESCRIPTION

[0047] Referring now to FIG. 1, some embodiments of the present disclosure are directed to a method 100 of producing a copper product from a copper concentrate. As used herein, the term copper concentrate refers to a composition including a concentration of copper, the extraction of which is desired. In some embodiments, the copper concentrate is a copper-containing mineral or combination of copper-containing minerals. In some embodiments, the copper concentrate is naturally occurring. In some embodiments, the copper concentrate includes a concentration of chalcopyrite. In some embodiments, the copper concentrate is man-made. In some embodiments, the copper concentrate is a waste product, e.g., from an industrial process. By way of example, certain mining processes produce waste products that include copper, but may have an arsenic content that is too high or an actual copper content that is too low to be processed by traditional processes for the purpose of isolating the copper component. However, the systems of the methods of the present disclosure are capable of extracting the copper component even from these traditionally untapped sources of copper.

[0048] Still referring to FIG. 1, some embodiments of the present disclosure include the production of a copper product from a copper concentrate via indirect reduction of the concentrate, e.g., from chalcopyrite. The reductive treatment processes consistent with the present disclosure are in contrast to the oxidative treatment more commonly pursued in the literature. At 102, a composition including the copper concentrate is provided. In some embodiments, the composition is provided to any suitable reaction vessel capable of containing the chemical reactions described below with respect to the various embodiments of the present disclosure. At 104, the composition is contacted with an aqueous solution including one or more chemical reducing agents. In some embodiments, the reducing agent is configured to reduce copper within the copper concentrate. In some embodiments, the reducing agent is also configured to be regenerated following oxidation via one or more electrochemical processes. In some embodiments, chemical reducing agents include reducing ions, compounds including the reducing ions, or combination thereof. In some embodiments, the chemical reducing agents include vanadium (II) ions, compounds including vanadium (II) ions, chromium (II) ions, compounds including chromium (II) ions, or combinations thereof. In some embodiments, the chemical reducing agents include vanadium (II) sulfate, chromium (II) chloride, tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40), or combinations thereof. In some embodiments, the aqueous solution has a concentration of about 0.01M to about 10 M of reducing agent.

[0049] In some embodiments, the aqueous solution is acidic. In some embodiments, the aqueous solution includes one or more acids. In some embodiments, the acids include sulfuric acid, hydrochloric acid, or combinations thereof. In some embodiments, the reaction vessel also includes one or more inert species, such as FeS.sub.2, silicates, other materials, or combinations thereof.

[0050] At 106, at least a portion of the copper concentrate is reacted with the chemical reducing agent to reduce copper within the copper concentrate. Without wishing to be bound by theory, reactions between the aqueous solution with reducing agent and the copper concentration are provided below. In these exemplary embodiments, chalcopyrite is chemically reduced by the reducing agents. Reactions 3 and 4 show reactions between CuFeS.sub.2, VSO.sub.4, and H.sub.2SO.sub.4. The products Cu.sub.2S and Cu.sup.0 are thermodynamically stable at low pH and reductive conditions. These reactions resemble Reactions 1 and 2 above but use the V.sup.2+ ion as an electron mediator to improve the electrochemical performance.

2CuFeS.sub.2+6H.sup.++2V.sup.2+.fwdarw.Cu.sub.2S+2Fe.sup.2++3H.sub.2S+2V.sup.3+[3]

Cu.sub.2S+2H.sup.++2V.sup.2+.fwdarw.2Cu+H.sub.2S+2V.sup.3+[4]

[0051] A violent reaction was observed upon adding CuFeS.sub.2 concentrate to the acidic V.sup.2+ solution. The rapid release of a gaseous species is consistent with the generation of H.sub.2S shown in Reactions 3 and 4. The liquid phase samples were measured with GC-MS to confirm the presence of dissolved H.sub.2S.

[0052] Reaction 5 shows a reaction between CrCl.sub.2 and HCl.

CuFeS.sub.2+4H.sup.++Cr.sup.2+.fwdarw.Cu.sup.++Fe.sup.2++2H.sub.2S+Cr.sup.3+[5]

[0053] Again, a violent reaction was observed upon adding the CuFeS.sub.2 concentrate to the solution of CrCl.sub.2 and HCl, consistent with the evolution of gaseous species predicted in Reaction 5. Although the cost of these reducing agents is high relative to copper, processes can be leveraged to efficiently regenerate the reducing agent, e.g., a vanadium redox flow battery, or similar electrochemical cell to regenerate V.sup.2+ at high current densities. In some embodiments, the reduction reactions occur homogeneously, e.g., within the entire reaction vessel or across the entirety of the copper concentrate. As evidenced by Reactions 3-5 above, reacting step 106 generates a copper product that can be isolated and used, or further processed for use, in whatever downstream process desired by the user. In some embodiments, the copper product is elemental copper. In some embodiments, the copper product is present as a copper-containing compound, which can be subsequently processed to isolate elemental copper therefrom, as will be discussed in greater detail below. In some embodiments, at least a portion of the copper product precipitates out of solution during or after reacting step 106. In some embodiments, at least a portion of the copper product precipitates out of solution in the reaction vessel. In some embodiments, at least a portion of the copper product precipitates out of solution as elemental copper. In some embodiments, at least a portion of the copper product precipitates out of solution as a copper compound. In some embodiments, at least a portion of the copper product remains in solution.

[0054] At 108, a solid phase reaction product is isolated. In some embodiments, the solid phase reaction product includes one or more species that precipitated out of solution during or in response to step 106, e.g., the copper product. As discussed above, in some embodiments, the solid phase reaction product includes solid elemental copper, solid copper-containing compounds, or combinations thereof. In some embodiments, the solid phase reaction product includes at least a portion of the copper product. In some embodiments, the solid phase reaction product includes all of the copper product. In some embodiments, at 110, at least a portion of the solid phase reaction product is contacted with an acidic stream. The acidic stream is effective to solubilize the copper product in the solid phase reaction product and produce a dissolved copper product. In some embodiments, the acidic stream include one or more acids. In some embodiments, the acidic stream includes a concentration of iron (III) sulfate, sulfuric acid, or combinations thereof. In some embodiments, the solid phase reaction product includes mineral inerts. Without wishing to be bound by theory, the inerts mostly include pyrite and silicates, although there may be trace amounts of rhenium- and arsenic-including compounds. It may be economically advantageous to recover rhenium-including inerts for rhenium production, and it may be environmentally advantageous to recover arsenic-including inerts for their conversion to benign forms.

[0055] At 112, the dissolved copper product is electrowinned, e.g., is provided to an electrowinning reactor, to isolate the copper product and produce a recycled acid. In some embodiments, the recycled acid is recycled for use during contacting step 110.

[0056] Still referring to FIG. 1, at 114, a liquid phase reaction product is isolated. In some embodiments, the liquid phase reaction product is isolated 114 as a result of the solid phase reaction product being isolated at step 108 as discussed above. In some embodiments, the liquid phase reaction product includes an oxidized chemical reducing agent, e.g., V.sup.3+ and/or Cr.sup.3+. In some embodiments, the liquid phase also includes Fe.sup.2+ ions in sulfuric acid. In some embodiments, the high solubility of oxidized reducing agent may be leveraged for its separation from Fe.sup.2+. In some embodiments, a biological reactor is used to oxidize V.sup.3+ and Fe.sup.2+ and hence facilitate their separation. In some embodiments, at 116, a second copper product is isolated from the liquid phase reaction product by any suitable means.

[0057] At 118, the liquid phase reaction product is fed to an electrochemical device. At 120, the oxidized chemical reducing agent is reduced at the electrochemical device. In some embodiments, the electrochemical device includes a concentration of ferrous iron or other reactant effective to help reduce the oxidized chemical reducing agent. In some embodiments, the oxidizing chemical reducing agent is reduced to a recycled chemical reducing agent. Without wishing to be bound by theory, in an exemplary embodiment, the cathodic reaction of the electrochemical device is given by Reaction 6, while the anodic reaction is given by Reaction 7.

V.sup.3++e.sup.?.fwdarw.V.sup.2+[6]

Fe.sup.2+.fwdarw.Fe.sup.3++e.sup.?[7]

[0058] Membrane crossover of the vanadium species may be mitigated by the application of high current densities, which are also desirable to achieve high reaction rates. Crossover of the iron species may lower the efficiency of the electrochemical cell but may not lead to long-term damage due to the downstream separation of iron. At 122, the recycled chemical reducing agent is contacted with the composition, e.g., at the reaction vessel.

[0059] Still referring to FIG. 1, at 124, a gaseous reaction product is isolated. In some embodiments, the gaseous phase reaction product is isolated 124 as a result of the solid phase reaction product being isolated at step 108, the liquid phase product being isolated at step 114, or combinations thereof. In some embodiments, the gaseous reaction product includes hydrogen sulfide. In some embodiments, at 126, the gaseous reaction product is contacted with a stream of ferric iron. Without wishing to be bound by theory, in an exemplary embodiment, the gaseous reaction product is treated with ferric ions for the recovery of protons by Reaction 8 below.

2Fe.sup.3++H.sub.2S.fwdarw.2Fe.sup.2++2H.sup.++S.sup.0[8]

[0060] In some embodiments, the protons produced by this reaction are transported across the separator of an electrochemical device, and are thus recovered. In some embodiments, the stream of ferric iron is provided from the electrochemical device. In some embodiments, contacting step 126 forms a ferrous iron effluent stream and an elemental sulfur effluent stream. In some embodiments, the ferrous iron effluent stream is recycled to the electrochemical device. In some embodiments, sulfur product in the elemental sulfur effluent stream is recycled for use in one or more downstream processes. In some embodiments, sulfur product in the elemental sulfur effluent stream is discarded.

[0061] Referring now to FIG. 2, some embodiments of the present disclosure are directed to a system 200 for producing a copper product from a copper concentrate. In some embodiments, system 200 includes a source 202 of copper concentrate. As discussed above, in some embodiments, the copper concentrate from the source is naturally occurring, man-made, or combinations thereof. In some embodiments, the copper concentrate includes a concentration of chalcopyrite, a waste product, e.g., from an industrial process, or combinations thereof.

[0062] In some embodiments, system 200 includes a reduction reactor 204, e.g., the reaction vessel described above with respect to method 100. In some embodiments, reduction reactor has one or more inputs 204A and one or more outputs 204B. In some embodiments, system 200 is configured to provide copper concentrate from source 202 to reduction reactor 204. In some embodiments, reduction reactor 204 is in communication with source 202 of copper concentrate, e.g., via input 204A. In some embodiments, reduction reactor 204 includes an aqueous solution 206. As discussed above, in some embodiments, aqueous solution 206 includes one or more chemical reducing agents. In some embodiments, chemical reducing agents include reducing ions, compounds including the reducing ions, or combination thereof. In some embodiments, the chemical reducing agents include vanadium (II) ions, compounds including vanadium (II) ions, chromium (II) ions, compounds including chromium (II) ions, or combinations thereof. In some embodiments, the chemical reducing agents include vanadium (II) sulfate, chromium (II) chloride, tungstozincic acid (H.sub.6ZnW.sub.12O.sub.40), or combinations thereof. In some embodiments, aqueous solution 206 has a concentration of about 0.01M to about 10M of reducing agent. In some embodiments, aqueous solution 206 is acidic. In some embodiments, the aqueous solution includes one or more acids. In some embodiments, the acids include sulfuric acid, hydrochloric acid, or combinations thereof.

[0063] In some embodiments, system 200 is configured to provide chemical reducing agents to reduction reactor 204. In some embodiments, chemical reducing agents are provided from a source 208 of chemical reducing agents, e.g., at an input 204A. In some embodiments, at least a portion of the chemical reducing agent in aqueous solution 206 is in the form of a recycle stream generated by system 200 itself via one or more other components, as will be discussed in greater detail below. In some embodiments, system 200 is configured to provide one or more acids to reduction reactor 204. In some embodiments, the acids are provided from a source 210 of acids, e.g., at an input 204A. In some embodiments, at least a portion of the acid in aqueous solution 206 is in the form of a recycle stream provided by system 200 itself via one or more other components.

[0064] As discussed above, reduction reactor 204 is configured to react at least a portion of the copper concentrate with the chemical reducing agent to reduce copper within the copper concentrate and separate a copper product from the copper concentrate. In some embodiments, at least a portion of the copper product precipitates out of solution in reduction reactor 204. In some embodiments, at least a portion of the copper product precipitates out of solution as elemental copper. In some embodiments, at least a portion of the copper product precipitates out of solution as a copper compound. In some embodiments, at least a portion of the copper product remains in solution.

[0065] Still referring to FIG. 2, system 200 includes a solid phase product outlet stream 212. In some embodiments, solid phase product outlet stream 212 is in communication with and removed from reduction reactor 204 by an outlet, e.g., first product outlet 204B. As discussed above, in some embodiments, solid phase product outlet stream 212 includes solid elemental copper, solid copper-containing compounds, or combinations thereof. In some embodiments, solid phase product outlet stream 212 includes at least a portion of the copper product. In some embodiments, solid phase product outlet stream 212 includes all of the copper product.

[0066] In some embodiments, the solid phase reaction product stream 212 is provided to a dissolution reactor 214. In some embodiments, system 200 is configured to provide one or more acids to dissolution reactor 214. In some embodiments, dissolution reactor 214 is in communication with one or more acid inlet streams 216. As discussed above, at least a portion of solid phase product outlet stream 212 is contacted with acid, e.g., from acid inlet stream 216. The acid is effective to solubilize the copper product in solid phase product outlet stream 212 and produce a dissolved copper product stream 218. In some embodiments, acid inlet stream 216 includes a concentration of iron (III) sulfate, sulfuric acid, or combinations thereof. In some embodiments, dissolved copper product stream 218 is sent to an electrowinning reactor 220, which produces and/or separates a copper product 221 and a recycled acid stream 222. In some embodiments, at least a portion of recycled acid stream 222 is fed back to dissolution reactor 214 for use in the dissolution of solid phase product outlet stream 212 in that reactor.

[0067] Still referring to FIG. 2, system 200 includes a liquid phase product outlet stream 224. In some embodiments, liquid phase product outlet stream 224 is in communication with and removed from reduction reactor 204 by an outlet, e.g., second product outlet 204B. As discussed above, in some embodiments, liquid phase product outlet stream 224 includes oxidized chemical reducing agent, e.g., V.sup.3+ and/or Cr.sup.3+. In some embodiments, the liquid phase also includes Fe.sup.2+ ions in sulfuric acid. In some embodiments, iron (II) ion species, a second copper product, e.g., dissolved copper product, or combinations thereof, are removed from liquid phase product outlet stream via one or more streams 225. In some embodiments, the high solubility of oxidized reducing agent may be leveraged for its separation from Fe.sup.2+. In some embodiments, liquid phase product outlet stream 224 includes a concentration of dissolved copper product, which can be isolated and recovered, e.g., via an electrowinning process.

[0068] In some embodiments, at least a portion of liquid phase product outlet stream 224 is fed to an electrochemical device 226. As discussed above, electrochemical device 226 includes a concentration of ferrous iron or other reactant effective to help reduce the oxidized chemical reducing agent. In some embodiments, the oxidized chemical reducing agent is reduced to a recycled chemical reducing agent and removed from electrochemical device 226 as a recycled chemical reducing agent stream 228. In some embodiments, recycled chemical reducing agent stream 228 is provided back to reduction reactor 204, e.g., at input 204A. In some embodiments, at least a portion of the ferrous iron is oxidized and removed as ferric iron feed stream 230, as will be discussed below.

[0069] Still referring to FIG. 2, system 200 includes a gaseous phase product outlet stream 232. In some embodiments, gaseous phase product outlet stream 232 is in communication with and removed from reduction reactor 204 by an outlet, e.g., third product outlet 204B. As discussed above, in some embodiments, gaseous phase product outlet stream 232 includes hydrogen sulfide gas. In some embodiments, ferric iron feed stream 230 and gaseous product outlet stream 232 are combined in a gaseous treatment reactor 234. The reaction between stream 230 and stream 232 forms a ferrous iron effluent stream 236 and an elemental sulfur effluent stream 238. In some embodiments, ferrous iron effluent stream 236 is recycled to electrochemical device 226 for use in reducing oxidized chemical reducing agent. In some embodiments, sulfur product in elemental sulfur effluent stream 238 is recycled for use in one or more downstream processes. In some embodiments, sulfur product in elemental sulfur effluent stream 238 is discarded.

[0070] Systems consistent with embodiments of the present disclosure include any additional miscellaneous components, e.g., conduits, power supplies, controllers, product collection reservoirs, etc., to facilitate the reduction of chalcopyrite and isolation of copper product, as will be clear to those of skill in the art.

Examples

[0071] In an exemplary embodiment, a sample of chalcopyrite mineral concentrate was provided. The sample was analyzed with energy dispersion X-ray diffraction and found to have the composition according to Table 2 below:

TABLE-US-00002 TABLE 2 Mineralogy of chalcopyrite concentrate Mineral Chemical Formula Percent Chalcopyrite CuFeS.sub.2 78.3 Pyrite FeS.sub.2 12.9 K-feldspar KAISi.sub.3O.sub.8 2.9 Plagioclase NaAlSi.sub.3O.sub.8 2.9 Quartz SiO.sub.2 2.2 Molybdenite MoS.sub.2 0.85
In addition to the concentrate shown in Table 2, three other versions of concentrate were provided with varying quantities of copper and other inerts. The processes of the present disclosure was determined to be compatible with concentrates of a wide range in purities. The CuFeS.sub.2 concentrate was sieved (?140+270 mesh) to confine the particle size to be within 53-106 ?m. The concentrate was subsequently rinsed with DI water and 1M H.sub.2SO.sub.4 to remove any soluble iron and copper ions generated during natural concentrate oxidation occurring in transport and storage.

[0072] In a first exemplary embodiment, CuFeS.sub.2 concentrate pulp densities of 39, 78, 117, or 234 g/L were added to a 250 mL Erlenmeyer flask containing 25 mL of a solution including 1M VSO.sub.4 and 4M H.sub.2SO.sub.4. For other experiments, a CuFeS.sub.2 concentrate pulp density of 39 g/L was added to a solution including 1M VSO.sub.4 and various H.sub.2SO.sub.4 concentrations. The reaction was conducted in a fume hood due to the rapid release of H.sub.2S gas. Liquid phase 100 ?L samples were taken at time points of 0, 5, 10, 20, 40, and 60 minutes, which were subsequently diluted for the measurement of Fe.sup.2+ and Cu.sup.+ content. After the reduction, the mineral particles were filtered from solution and allowed to air dry prior to characterization.

[0073] An iCE 3300 AAS was used to measure the release of iron and copper ions into solution from CuFeS.sub.2 during its reduction. The characteristic wavelengths for the iron and copper measurements were 248.3 nm and 324.8 nm, respectively. Standards ranging from 0-4 ppm were measured immediately before the samples to construct linear (R2>0.995) calibration curves.

[0074] A PANalytical XPert3 Powder XRD was used to measure the bulk mineral phase of the reaction products. The XRD was operated with filtered Empyrean Cu Ka radiation (k=0.15418 nm), a tube voltage of 45 kV, and a current of 40 mA. The mineral products were placed on a silicon crystal zero-diffraction plate (MTI Corporation) and were adhered in place with Apiezon grease. The samples were scanned continuously in the range of 10-100? with a step size of 0.0065? on a spinning plate with a revolution time of 2.0 s. A PIXcellD detector was used to record the peak intensity for the subsequent analysis of the mineral composition.

[0075] A Zeiss Sigma VP SEM was used to capture images of the mineral products after reaction. The SEM-EDS analysis was operated at an accelerating potential of 6 kV and base pressure of approximately 1?10.sup.?5 torr. Samples were supported on carbon tape and were coated with gold using a Cressington 108 Auto Sputter Coater. The sputtering was conducted under argon gas flow with 0.1 mbar of pressure for 20 s to obtain a 1 nm coating of AuPd. A Bruker XFlash Detector was used for EDS analysis to analyze elemental composition.

[0076] A sample of the mineral products was digested in aqua regia for copper extraction, and an equivalent sample of the mineral products was leached in a solution including 0.5M Fe.sub.2(SO.sub.4).sub.3 in 1M H.sub.2SO.sub.4. The percent of copper released was determined by the ratio of copper extracted by the two leachants.

[0077] The H.sub.2S gas was rapidly released and qualitatively measured with a Sensorcon detector. The release of gas ensued immediately upon the addition of the concentrate and concluded within minutes of reaction time. Liquid phase samples were measured with gas chromatography-mass spectroscopy (GC-MS) to confirm the presence of dissolved H.sub.2S, while no other gases were detected. The H.sub.2S gas may be oxidized to innocuous S.sup.0 in an industrial process.

[0078] FIG. 3 shows the percent of Fe.sup.2+ released from CuFeS.sub.2 concentrate during its direct electrochemical reduction (Reactions 1-2) and its reduction by VSO.sub.4 (Reactions 3-4). It was experimentally validated that Fe.sup.2+ within the concentrate was inert, and therefore the measurement of Fe.sup.2+ was a suitable proxy for CuFeS.sub.2 conversion. The figure demonstrates that the use of an electron mediator is kinetically advantageous to the direct electrochemical reduction of CuFeS.sub.2 concentrate. VSO.sub.4 enables 100% release of Fe.sup.2+ from CuFeS.sub.2 concentrate within 60 minutes despite the relative high concentrate loading of 39 g/L. The direct electrochemical reduction requires extended durations to achieve complete conversion of concentrate due to the proclivity of the hydrogen evolution reaction to take place for slurry electrodes. The direct electrochemical reduction results shown in FIG. 3 utilized the same experimental procedure denoted in the literature with an applied current density of 10 mA/cm2.

[0079] FIG. 4 shows the XRD characterization of the mineral products immediately following the reductive leaching by VSO.sub.4. The predominant peaks of the unreacted CuFeS.sub.2 concentrate sample correspond to CuFeS.sub.2, FeS.sub.2, and SiO.sub.2, which is consistent with the mineralogy shown in Table 2. The peaks corresponding to CuFeS.sub.2 diminished in the spectra of the reacted mineral products and peaks corresponding to the mineral products emerged. The results show the progression of the copper-containing solids from CuFeS.sub.2 to Cu.sub.2S and Cu.sup.0, which is consistent with Reactions 3 and 4. The XRD spectra corroborate that FeS.sub.2 and silicates were inert during the reductive leaching by VSO.sub.4.

[0080] FIG. 5 shows the shift in the mineral products from Cu.sup.0 to CuSO.sub.4.Math.5H.sub.2O during an air-drying step. Sulfuric acid still coated on the samples reacted with air as shown by Reaction 9 to produce CuSO.sub.4.Math.5H.sub.2O. Without wishing to be bound by theory, it is hypothesized that galvanic interactions between Cu.sup.0 and FeS.sub.2, studied in iron-containing systems, may also occur in vanadium-containing systems and have a secondary effect.

2Cu.sup.0+2H.sub.2SO.sub.4+O.sub.2.fwdarw.2CuSO.sub.4+2H.sub.2O[9]

[0081] FIGS. 6A-6D show the characterization of the mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of CuFeS.sub.2 concentrate (Reactions 3 and 4 above) and after air-drying (Reaction 9). FIG. 6A shows optical microscopy images of the mineral products, which were obtained with a Keyence VHX-5000 microscope. The appearance of the mineral products differed significantly from the unreacted CuFeS.sub.2 concentrate. The mineral products were blue in appearance, which may be indicative of CuSO.sub.4.Math.5H.sub.2O. FIG. 6B shows the SEM-EDS results of the mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of concentrate. The unreacted chalcopyrite concentrate sample shows peaks corresponding to the characteristic energies of C, 0, Fe, Cu, Al, Si, and S, which is consistent with the mineralogy shown in Table 2. The presence of the C peak is an artifact of placing the samples on carbon tape prior to analysis. The reacted samples show diminishments in the Fe and S peaks due to the release of Fe.sup.21 ions to solution and the release of H.sub.2S as a gas, respectively. The reacted samples also show diminishments in the Al and Si peaks due to their decreasing mass fractions within the samples. The predominant peaks of the reacted samples are Cu, S, and O, which is consistent with the formation of CuSO.sub.4.Math.5H.sub.2O. The elongation of the O peak within the spectra is consistent with this product. Without wishing to be bound by theory, the absence of a V peak within the indicates that V does not precipitate to the solid phase during the progression of the reaction.

[0082] FIG. 6C shows XRD spectra for the mineral products after 60 minutes of reaction between 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and various loadings of concentrate. The predominant peaks of the unreacted CuFeS.sub.2 concentrate sample corresponded to CuFeS.sub.2, FeS.sub.2, and SiO.sub.2, which is consistent with the mineralogy shown in Table 2. The peaks corresponding to CuFeS.sub.2 diminished in the spectra of the reacted mineral products and peaks corresponding to the mineral products emerged. FIG. 6D shows the region of the XRD spectra used to identify the mineral products. The XRD spectra of the mineral products are consistent with the formation of CuSO.sub.4.Math.5H.sub.2O, which is consistent with the SEM-EDS data set.

[0083] FIG. 7 shows that XRD spectra consistent with CuSO.sub.4.Math.5H.sub.2O was reproducible for experiments conducted between 1M VSO.sub.4, 39 g/L of concentrate, and initial H.sub.2SO.sub.4 concentrations of 0.5M and 1M. The pH of the solution subsequent to the reactions were below one for all of these experiments, indicating that these reactions were not pH limited. No vanadium salt was observed to precipitate from solution for any of these conditions, which indicates that the process has potential for high vanadium recovery and recycle. The pH of these solutions were below one, suggesting that these reactions were not pH limited. Vanadium redox flow batteries (VRFBs) typically operate with H.sub.2SO.sub.4 concentrations ranging from 2-4M, and therefore, a downstream vanadium (II) regeneration step may benefit from relatively high acid concentrations.

[0084] FIG. 8A shows the percent of Fe.sup.2+ released as a function of time for a slurry including 1M VSO.sub.4, 4M H.sub.2SO.sub.4, and CuFeS.sub.2 concentrate loadings of 39, 78, 117, and 234 g/L. The figure shows that approximately 100% of Fe.sup.2+ was released from CuFeS.sub.2 during the reduction, which is consistent with Reactions 3 and 4. Without wishing to be bound by theory, the incomplete release of Fe.sup.2+ for the experiments conducted with concentrate loadings of 117 and 234 g/L suggests the complete utilization of V.sup.2+.

[0085] FIG. 8B shows the results for the subsequent extraction of Cu.sup.2+ from the mineral products by reaction with a solution including 0.5M Fe.sub.2(SO.sub.4).sub.3 in 1M H.sub.2SO.sub.4 for 60 minutes. Reaction 10 shows the dissolution of CuSO.sub.4.Math.5H.sub.2O, which was characterized to be the final mineral product for reactions between 1M VSO.sub.4, 4M H.sub.2SO.sub.4 and 39 g/L of chalcopyrite concentrate.

CuSO.sub.4.fwdarw.Cu.sup.2++SO.sub.4.sup.2?[10]

[0086] The results show that virtually all of the Cu.sup.2+ can be extracted from the 39 g/L mineral products within minutes. The 39 g/L samples were also solubilized in 1M H.sub.2SO.sub.4. The aqueous solution may go to solvent extraction and electrowinning for the production of metallic copper. Without wishing to be bound by theory, the incomplete copper extraction for higher pulp densities is partly related to the incomplete conversion of CuFeS.sub.2 shown by the XRD analysis above. It is shown that virtually no Cu.sup.2+ is extracted from the CuFeS.sub.2 concentrate, and therefore, the reductive treatment directly leads to the extraction of copper.

[0087] FIG. 9A shows that approximately 100% of Fe.sup.2+ was released from CuFeS.sub.2 for the concentrate loading of 39 g/L and H.sub.2SO.sub.4 concentrations of 0.5M, 1M, and 4M. FIG. 9B shows the mineral products react completely with a solution including 0.5M Fe.sub.2(SO.sub.4).sub.3 in 1M H.sub.2SO.sub.4 for the complete recovery of copper. These results indicate that the reduction step may not depend on acid concentration as long as there are a sufficient number of protons available to facilitate the reaction.

[0088] In a second exemplary embodiment, CuFeS.sub.2 concentrate pulp densities of 39, 78, 117, or 234 g/L were added to a 250 mL Erlenmeyer flask containing 25 mL of a solution including 1M CrCl.sub.2 and 4M HCl. For other experiments, a CuFeS.sub.2 concentrate pulp density of 39 g/L was added to a solution including 1M CrCl.sub.2 and various HCl concentrations. Thirdly, for other experiments, a CuFeS.sub.2 concentrate pulp density of 39 g/L was added to a solution including 1M CrCl.sub.2, 4M HCl, and various concentrations of FeCl.sub.2. The reaction was conducted in a fume hood due to the rapid release of H.sub.2S gas, shown in FIG. 10. Liquid phase 100 ?L samples were taken at time points of 0, 5, 10, 20, 40, and 60 minutes, which were subsequently diluted for the measurement of Fe.sup.2+ and Cu.sup.+ content. After the reduction, the mineral particles were filtered from solution and allowed to air dry prior to characterization.

[0089] An iCE 3300 AAS was used to measure the release of Fe.sup.2+ and Cu.sup.+ ions into solution from CuFeS.sub.2 during its reduction. The characteristic wavelengths for the iron and copper measurements were 248.3 nm and 324.8 nm, respectively. Standards ranging from 0-4 ppm were measured immediately before the samples to construct linear (R2>0.995) calibration curves.

[0090] A PANalytical XPert3 Powder XRD was used to measure the bulk mineral phase of the reaction products. The XRD was operated with filtered Empyrean Cu Ka radiation (k=0.15418 nm), a tube voltage of 45 kV, and a current of 40 mA. The mineral products were placed on a silicon crystal zero-diffraction plate (MTI Corporation) and were adhered in place with Apiezon grease. The samples were scanned continuously in the range of 10-100? with a step size of 0.0065? on a spinning plate with a revolution time of 2.0 s. A PIXcellD detector was used to record the peak intensity for the subsequent analysis of the mineral composition.

[0091] A PHI 5500 XPS equipped with an Al x-ray source was used to measure the elemental composition of the reaction product surfaces. The base pressure of the chamber was approximately 1?10.sup.?8 torr. Samples were supported on carbon tape.

[0092] A Zeiss Sigma VP SEM was used to capture images of the mineral products after reaction. The SEM-EDS analysis was operated at an accelerating potential of 6 kV and base pressure of approximately 1?10.sup.?5 torr. Samples were supported on carbon tape and were coated with gold using a Cressington 108 Auto Sputter Coater. The sputtering was conducted under argon gas flow with 0.1 mbar of pressure for 20 s to obtain a 1 nm coating of AuPd. A Bruker XFlash Detector was used for EDS analysis to analyze elemental composition.

[0093] A sample of the mineral products was digested in aqua regia for complete copper extraction, and an equivalent sample of the mineral products was leached in a solution including 0.5M Fe.sub.2(SO.sub.4).sub.3 in 1M H.sub.2SO.sub.4. The percent of copper released was determined by the ratio of copper extracted by the two leachants.

[0094] FIG. 10 shows pictures of the reaction between 1M CrCl.sub.2, 4M HCl, and 78 g/L CuFeS.sub.2 concentrate after 0, 2, 3, 5, and 60 seconds of reaction time. The pictures show the rapid release of H.sub.2S gas, which was qualitatively measured with a Sensorcon detector. The release of gas ensued immediately upon the addition of the concentrate and concluded within a minute of reaction time. The liquid phase samples were measured with gas chromatography-mass spectroscopy (GC-MS) to confirm the presence of dissolved H.sub.2S for similar experiments.

[0095] The evolution of gaseous H.sub.2S coincided with the release of Fe.sup.2+ ions to solution, which is consistent with Reaction 5 above. FIG. 11A shows the percent of Fe.sup.2+ released as a function of time for a slurry including 1M CrCl.sub.2, 4M HCl, and CuFeS.sub.2 concentrate loadings of 39, 78, 117, and 234 g/L. The reaction kinetics were rapid considering that approximately 100% of Fe.sup.2+ was released from CuFeS.sub.2 within 5 minutes for the CuFeS.sub.2 concentrate loadings of 39, 78 and 117 g/L. The release of Fe.sup.2+, however, was limited for the CuFeS.sub.2 concentrate loading of 234 g/L suggesting the complete utilization of Cr.sup.2+. Without wishing to be bound by theory, measurements of Fe.sup.2+ release exceeding 100% may indicate a minor error in the estimation of composition shown in Table 2 due to both the error in XRD quantification and the sieving of the concentrate to be within 53-106 m. Experiments were conducted while purging the headspace of the reactor with argon and similar results were observed, indicating that small amount of oxygen present in the system did not oxidize Cr.sup.2+ to any significant level for the experiments shown. The release of Cu.sup.+ to solution during the progression of the reaction was measured, but the quantitative results were inconsistent due to the precipitation of the Cu.sup.+ ion out of solution. The pH of the solutions after the reduction experiments were below zero, indicating that these reactions were not pH limited.

[0096] FIG. 11B shows the percent of Fe.sup.2+ released as a function of time for slurries including 1M CrCl.sub.2, 39 g/L of CuFeS.sub.2 concentrate, and initial HCl concentrations of 0M, 0.5M, 1M, and 4M. The pH of the solution after the reduction step was approximately 2.5 for the slurries with initial HCl concentrations of 0M, 0.5M, and 1M, indicating that these reactions were pH limited. The pH of the solution after the reduction step may be leveraged to facilitate a separation between Fe.sup.2+ and Cr.sup.3+, which may be desirable prior to the reduction of Cr.sup.3+ to Cr.sup.2+ by an electrolysis unit. These results suggest that the proton has a greater stoichiometric number than CuFeS.sub.2, which is consistent with Reaction 5. Experiments conducted with initial HCl concentrations of 2M and 3M were found to not be pH limited.

[0097] FIG. 12 shows images of the mineral products after 60 minutes of reduction with the Cr.sup.2+ ion obtained with a Keyence VHX-5000 microscope. Without wishing to be bound by theory, the results indicate that the mineral product is affected by the CuFeS.sub.2 concentrate loading. The 39 g/L CuFeS.sub.2 loading yielded a green product, which is consistent with the appearance of CuCl as well as other potential CuCl complexes. The various mineral products were characterized and shown to yield different amounts of copper recovery. The mineral products post reaction with various HCl concentrations yielded the same trend in appearance.

[0098] FIG. 13 shows the XRD spectra for the various chalcopyrite concentrate loadings subsequent to reaction with the Cr.sup.2+ ion, and FIG. 14 shows the XRD spectra for the mineral samples subsequent to reaction with the Cr.sup.2+ ion and various initial HCl concentrations. The predominant peaks of the unreacted CuFeS.sub.2 concentrate were consistent with CuFeS.sub.2, FeS.sub.2, and SiO.sub.2, as shown in Table 2. The relative intensity of the peaks associated with CuFeS.sub.2 diminished for the reacted mineral products, consistent with the Fe.sup.2+ release measured by AAS. The peaks associated with the reaction products emerged for the mineral products with high conversion of CuFeS.sub.2. The predominant mineral product was determined to be copper chloride (CuCl) from the spectra. Secondary products, such as Cu.sub.2(OH).sub.3Cl, were consistent with the spectra. Reaction 11 shows the precipitation of CuCl out of solution, which is the primary product formed. Reaction 11 is shown for simplicity whereas the chemistry taking place is more complicated and a variety of CuCl complexes may precipitate. The precipitation of CuCl out of the solution containing 4M HCl was unexpected considering that the molar ratio of Cl/Cu was 36 in the system. However, the molar ratio of Cl/Cr was 6, and therefore, complexes formed between Cl.sup.? and Cr.sup.3+ may lower the number of Cl.sup.? ions available to stabilize Cu.sup.+. The concentration of Cu.sup.+ in solution after 60 minutes of reduction was approximately 0.07M, which is close to the solubility limit of 0.233M reported at 2M HCl in the literature 36. It is estimated that 40% of copper in the system remained in the bulk solution as Cu.sup.+ and 60% precipitated out of solution for the experiments conducted with a concentrate loading of 39 g/L and an acid concentration of 4M HCl.

Cu.sup.++Cl?.fwdarw.CuCl[11]

[0099] The XRD data, in conjunction with the AAS data, indicate that the FeS.sub.2 and silicates were inert during the reductive treatment. Experiments were conducted between 39 g/L CuFeS.sub.2 concentrate, 1M CrCl.sub.2, 4M HCl and initial ferrous chloride (FeCl.sub.2) concentrations of 0, 0.5M, 1M, and 2M. Without wishing to be bound by theory, it was determined that the reduction process can tolerate initial FeCl.sub.2 concentrations of 1M and below. The Fe.sup.2+ precipitated out of solution for the experiment conducted with an initial FeCl.sub.2 concentration of 2M.

[0100] FIG. 15 shows SEM results for the mineral products after reaction with 1M CrCl.sub.2 and 4M HCl for 60 minutes. The mineral products develop some mossy features, which may be related to the growth of CuCl. FIG. 16 shows EDS results for the mineral samples post reduction with the Cr.sup.2+ ion. The unreacted CuFeS.sub.2 concentrate samples show peaks corresponding to Cu, Fe, S, Si, and O. The reacted samples show the diminishment in the Fe and S peaks, which is consistent with the release of Fe.sup.2+ to solution and the release of H.sub.2S as a gas. The minor S peak present in the 39 g/L sample may be related to the presence of unreacted FeS.sub.2 in the mineral products. The reacted samples also show the emergence of the Cl peak, which is consistent with the formation of CuCl. The Cu peak elongates for the reacted samples due to the increasing mass fraction of Cu within the samples. No peak corresponding to Cr was observed in the spectra, indicating that the presence of Cr within the samples is minor. The samples were digested in aqua regia and the mass fraction of Cr within the samples was estimated to be 1-3%. Without wishing to be bound by theory, the presence of chromium is thought to be an artifact of the procedure used to filter and dry the mineral products.

[0101] FIGS. 17A-17B shows the XPS spectra of Cu (FIG. 17A) and Cl (FIG. 17B) for the mineral samples post reduction with the Cr.sup.2+ ion. The Cr element was not observed on the mineral products, which further indicates that the samples were not comprised of chromium. Similarly, Fe and S were not observed on the surface of the mineral reaction products, which is consistent with the release of Fe.sup.2+ and H.sub.2S from the surface of the particles into the solution phase. The absence of a sulfur passivation layer may account for the rapid kinetics of the reduction reaction. The various copper peaks indicate the presence of several copper-containing products. For instance, the peaks at the binding energies of 944 and 935 eV are assigned to Cu.sub.2(OH).sub.3Cl and CuCl, respectively. The Cu scans also show an observable shift in binding energy from the CuFeS.sub.2 concentrate standard. The emergence of a Cl peak for the reacted samples is consistent with the formation of CuCl complexes.

[0102] FIG. 18 shows the extraction of Cu.sup.2+ from the mineral products by 0.5M Fe.sub.2(SO.sub.4).sub.3. Reaction 12 shows the leaching reaction of CuCl by the Fe.sup.31 oxidant, which goes to completion within minutes.

CuCl+Fe.sup.3+.fwdarw.Cu.sup.2++Cl.sup.?+Fe.sup.2+[12]

[0103] The results show that virtually all of the Cu.sup.2+ can be extracted from the 39 g/L mineral product within minutes. In experiments, not shown, the 39 g/L sample was solubilized in 1M H.sub.2SO.sub.4. The aqueous solution may go to solvent extraction and electrowinning for the production of metallic copper. The incomplete copper extraction for higher pulp densities is at least partly related to the incomplete conversion of CuFeS.sub.2 shown in FIGS. 11A-11B. Also, potential intermediates formed, such as Cu.sub.2(OH).sub.3Cl, may be refractory for copper leaching and undesirable. It is shown that virtually no Cu.sup.2+ is extracted from the CuFeS.sub.2 concentrate, and therefore, the reductive treatment directly leads to the extraction of copper.

[0104] Methods and systems of the present disclosure are advantageous to provide a transformative hydrometallurgical process to lower the costs of copper production and thereby sustain the use of copper throughout the global transition to renewable energy technologies. These embodiments enable the hydrometallurgical production of copper, which is more environmentally and economically sustainable than the current state of the art. Hydrometallurgical processing is preferred and used for other copper-mineral reserves such as copper oxides. The focal point of the hydrometallurgical process is the reductive treatment of chalcopyrite, which is in contrast to the oxidative treatment more commonly pursued in the literature. Without wishing to be bound by theory, the chemical reduction of CuFeS.sub.2 is advantageous at least because it obviates the hydrogen evolution reaction and circumvents engineering challenges associated with slurry electrodes. Although the cost of vanadium and chromium are high relative to copper, a VRFB, or iron chromium flow battery (ICFB) may be leveraged to efficiently regenerate V.sup.2+ or Cr.sup.2+ at high current densities. The mineral products were leached by solutions including 1M H.sub.2SO.sub.4 and 1.5M Fe.sup.31 in 1M H.sub.2SO.sub.4 to demonstrate that the mineral products yield complete copper extraction.

[0105] A process flow diagram and associated technoeconomic analysis suggests that the reduction of chalcopyrite by an aqueous reductant may be competitive with the pyrometallurgical standard for copper production. Table 3 shows the investment and operating costs for steps in the hydrometallurgical process. The direct ($3.1/kg of Cu) and indirect ($2.4/kg of Cu) costs of copper production sum to $5.5/kg of Cu, which is lower than the estimated cost of the pyrometallurgical process.

TABLE-US-00003 TABLE 3 Estimated investment and operating costs of the chemical reduction of CuFeS.sub.2 Investment cost Operating Cost Component ($/tonne of Cu per year) ($/kg of Cu) Open-Pit Mining 10,000 0.5 Ball Milling/Flotation 10,000 1.3 Electrochemical Device ~650 ~0.3 Ore Reduction Reactor ~500 ~0.05 Ore Dissolution Reactor ~500 ~0.05 H.sub.2S Treatment Reactor ~500 ~0.05 Electrowinning ~1000 0.15

[0106] It was assumed that the reduction and dissolution reactors have the same investment and operating costs as a solvent extraction plant, which includes the costs of a mixer, pumps, and storage tanks. This assumption was reasonable because the fast kinetics of the reactions lead to relatively small reactor volumes. The investment cost of the electrochemical device was estimated from scaling-up reported costs of a VRFB. It was estimated that a 20 MW VRFB is required to match the copper output of a typical smelter, which processes 4,000 tonnes of CuFeS.sub.2 concentrate per day. The mass fraction of concentrate was assumed to be 0.3 and the nominal voltage of the electrochemical cell was assumed to be 1.35 V to perform these calculations. The operating cost of the electrochemical device was estimated from the industrial cost of electricity and assuming that one mole of vanadium is lost for every 20 moles of copper that is produced. The operating cost of the electrochemical device may fluctuate depending on the quality of the vanadium/iron separation and the selling price of V.sub.2O.sub.5.

[0107] FIG. 19 shows the estimated energy requirement for the pyrometallurgical, electrometallurgical, and hydrometallurgical routes for Cu production after the ore has been mined and concentrated. The pyrometallurgical route has the highest energy requirement of approximately 13 kJ/lb Cu, which correlates to the release of significant amounts of CO.sub.2. The electrometallurgical route has similar energy requirements due in part to the high energy requirements of the electrochemical cell. It was assumed that the electrochemical cell operates with a cell potential of 2.5 V and a faradaic efficiency of 40% to estimate its energy requirement. The hydrometallurgical route for Cu production is estimated to use approximately 8 kJ/lb Cu, which represents a significant reduction in global CO.sub.2 emissions. It was assumed that the electrochemical cell operates with a cell potential of 1.35 V and a faradaic efficiency of 95% to estimate its energy requirement. Also, it was assumed that a V/Fe separation step has the same energy requirement as conventional solvent extraction.

[0108] As discussed above, the global mining industry is interested in hydrometallurgical routes to convert chalcopyrite to copper due to environmental and economic pressures. The embodiments of the present disclosure are potentially less expensive and less polluting than current pyrometallurgical processing, and would also allow increased domestic production of copper in the USA.

[0109] Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.