WO2025222254A1

WO2025222254A1 - Hydrometallurgical process for copper

Info

Publication number: WO2025222254A1
Application number: PCT/AU2025/050405
Authority: WO
Inventors: James William VAUGHAN; David Andrew Mann
Original assignee: University of Queensland UQ
Current assignee: University of Queensland UQ
Priority date: 2024-04-23
Filing date: 2025-04-23
Publication date: 2025-10-30
Anticipated expiration: 2026-10-23

Abstract

The present disclosure relates to hydrometallurgical processes for obtaining copper metal from a copper-containing feedstock. The processes include solubilising copper in the feedstock to obtain a solution comprising cuprous ions and reducing the cuprous ions to obtain a copper deposit at a cathode from which the copper deposit is subsequently stripped. The present disclosure further relates to electrolytic cells for obtaining copper metal from a copper-containing feedstock.

Description

"Hydrometallurgical process for copper" Technical Field [0001] The present disclosure relates to hydrometallurgical processes for obtaining copper metal from a copper-containing feedstock. The present disclosure further relates to electrolytic cells for obtaining copper metal from a copper-containing feedstock. Background [0002] Primary copper production starts with the mining of copper-bearing ores, with the great majority of copper ores being sulfides. Copper is typically produced from these ores by one of two process routes: pyrometallurgical (dry) or hydrometallurgical (wet). [0003] Pyrometallurgical processes, which account for approximately 80% of primary copper production, typically involve grinding sulfide ore, floating the sulfide minerals to create a copper concentrate, smelting the concentrate to make a copper matte, converting the matte to blister copper, casting anodes and electrorefining the anodes to high purity metallic copper. The process steps to convert copper concentrate to anode quality copper metal consume about 8.9 GJ/t-Cu, with total energy for copper production being about 33 GJ/t-Cu. [0004] Hydrometallurgical processes account for the remaining 20% of copper production and the typical process involves leaching, solvent extraction and electrowinning. The hydrometallurgical approach requires about 14.7 GJ/t-Cu, largely for the electrowinning step. [0005] The relatively high energy consumption of the hydrometallurgical electrowinning step is related to the copper being present in cupric form such that two electrons are required per copper ion in order to form metallic copper at the cathode. Also, conventional electrowinning involves evolving oxygen gas at the anode which requires a high electrowinning cell potential, about 2 V. [0006] While providing copper in cuprous form in the solution to undergo electrowinning would reduce the electricity requirement to one electron per copper ion, it has been found that electrowinning of such materials leads to a copper deposit having undesirable physical properties, such as the copper deposit growing in a dendritic form which increases the complexity of the equipment required and results in additional materials handling steps. Furthermore, copper recovered in this dendritic form does not meet required purity specifications to be considered high grade copper and therefore needs additional processing steps including washing, drying, melting, casting and electrorefining. [0007] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application. Summary [0008] According to one aspect of the present disclosure, there is provided a hydrometallurgical process for obtaining copper metal from a copper-containing feedstock, the process comprising: - solubilising copper in the feedstock in an aqueous media comprising a stoichiometric excess of halide complexing agent and an oxidative lixiviant to obtain a solution and a solid residue, the solution comprising cuprous ions; - electrolytically reducing cuprous ions in the solution as catholyte to obtain a copper deposit at a first electrode as a cathode coupled with a second electrode as an anode; - electrolytically stripping the copper deposit from the first electrode as an anode coupled with a third electrode as a cathode and obtaining copper metal at the third electrode. [0009] According to another aspect of the present disclosure, there is provided a hydrometallurgical process to obtain copper from a copper-containing feedstock, the process comprising: - solubilising copper in the feedstock in an aqueous media comprising a stoichiometric excess of halide complexing agent and an oxidative lixiviant to obtain a solution and a solid residue, the solution comprising cuprous ions; and - electrolytically reducing cuprous ions in the solution as a catholyte to obtain the copper as a deposit at a first electrode as a cathode of an electrolytic cell and coupled with a second electrode as an anode of the electrolytic cell, the first electrode comprising a cylindrical shell defining a cell volume configured to receive the second electrode comprising an anodic cylinder therein. [0010] According to a further aspect of the present disclosure, there is provided an electrolytic cell for obtaining copper metal from a chloride solution comprising cuprous ions, the electrolytic cell comprising: - a first electrode comprising a cylindrical shell and defining a cell volume, the cell volume configured to receive, respectively: - a second electrode as an anodic cylinder; and - a third electrode as a cathodic cylinder, wherein the first electrode coupled with the second electrode electrolytically reduce cuprous ions in the solution to obtain a copper deposit at the first electrode as a cathode and the third electrode coupled with the first electrode electrolytically strips the copper deposit from the first electrode as an anode to obtain copper metal at the third electrode. Brief Description of Drawings [0011] Embodiments of the present disclosure will now be described by way of example only with reference to the accompanying drawings in which: [0012] Figure 1 shows a cutaway side view of a cylindrical electrolytic cell in an electrowinning configuration in accordance with an embodiment of the present disclosure; and [0013] Figure 2 shows a cutaway side view of a cylindrical electrolytic cell in an electrorefining configuration in accordance with an embodiment of the present disclosure; and [0014] Figure 3 shows a picture of copper electrodeposited onto the first cylindrical cathode. General terms [0015] With regards to the definitions provided herein, unless stated otherwise, or implicit from context, the defined terms and phrases include the provided meanings. Unless explicitly stated otherwise, or apparent from context, the terms and phrases below do not exclude the meaning that the term or phrase has acquired by a person skilled in the relevant art. The definitions are provided to aid in describing particular embodiments, and are not intended to limit the claimed invention, because the scope of the invention is limited only by the claims. Furthermore, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular. [0016] All publications discussed and/or referenced herein are incorporated herein in their entirety. [0017] Throughout this disclosure, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e., one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. For example, reference to “a” includes a single as well as two or more; reference to “an” includes a single as well as two or more; reference to “the” includes a single as well as two or more and so forth. [0018] Each example of the present disclosure described herein is to be applied mutatis mutandis to each and every other example unless specifically stated otherwise. The present disclosure is not to be limited in scope by the specific examples described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the disclosure as described herein. [0019] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the examples, steps, features, methods, processes, and compositions, referred to or indicated in this specification, individually or collectively, and any and all combinations or any two or more of said steps or features. [0020] The term “and/or”, e.g., “X and/or Y” shall be understood to mean either “X and Y” or “X or Y” and shall be taken to provide explicit support for both meanings or for either meaning. [0021] As used herein, the term “about”, unless stated to the contrary, typically refers to a range of up to +/- 10% of the designated value, and includes smaller ranges therein, for example +/- 5% or +/- 1% of the designated value. [0022] It is to be appreciated that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. [0023] Throughout the present specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be interpreted as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible sub- ranges as well as individual numerical values within that range, unless specifically indicated. For example, description of a range such as from 1 to 5 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 5, from 3 to 5 etc., as well as individual and partial numbers within the recited range, for example, 1, 2, 3, 4, 4.5, 4.75, and 5, unless where integers are required or implicit from context. This applies regardless of the breadth of the disclosed range. Where specific values are required, these will be indicated in the specification. [0024] Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Description of Embodiments [0025] In the following description, reference is made to the accompanying drawings which form a part hereof, and which is shown, by way of illustration, several embodiments. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure. [0026] According to one aspect of the present disclosure, there is provided a hydrometallurgical process for obtaining copper metal from a copper-containing feedstock. [0027] In broad terms, the process comprises the steps of leaching, electrowinning (100A), and electrorefining (100B). [0028] The copper-containing feedstock may comprise a copper sulfide compound, with the solid residue comprising elemental sulfur. The copper sulfide compound may comprise iron, with the solid residue comprising an iron precipitate. In some embodiments, the iron is precipitated from a homogenous solution and recovered from the process in a separate stream from the elemental sulfur. In some embodiments, the copper-containing feedstock comprises chalcopyrite and/or chalcocite and/or bornite and/or covellite. [0029] In another embodiment, the copper-containing feedstock may comprise copper in combination with precious metals and/or other base metals. The base metals may comprise iron, tin, aluminium, nickel, cobalt, lead, zinc, selenium, indium, gallium, and combinations thereof. The precious metals may include gold, silver, and/or platinum group metals (ruthenium, rhodium, palladium, osmium, iridium). In some embodiments, the copper-containing feedstock comprises waste electrical and electronic equipment (WEEE), also referred to herein as e-waste. [0030] A number of reactions are occurring during the process of the present disclosure. By way of non-limiting example, some key reactions during the leaching, electrowinning, and electrorefining are summarised as follows (without specifying the aqueous phase speciation): [0031] Leaching 2Cu²⁺ + Cu2S → 4Cu⁺ + S Cu²⁺ + CuS → 2Cu⁺ + S 3Cu²⁺ + CuFeS2 → 4Cu⁺ + Fe²⁺ + 2S Fe³⁺ + 2H2O → FeOOH + 3H⁺ 3Fe³⁺ + Na⁺ + 2SO^42- + 6H²O → NaFe³(SO⁴)²(OH)⁶ + 6H⁺ Cu⁺ + Fe³⁺ → Cu²⁺ + Fe²⁺ O2(g) + 4H⁺ + 4e- → H2O Ag → Ag⁺ + e- S + 4H2O → H2SO4 + 6e- + 6H⁺ [0032] Electrowinning (Cathode) Cu⁺ + e- → Cu Cu²⁺ + e- → Cu⁺ Fe³⁺ + e- → Fe²⁺ 2H⁺ + 2e- → H2(g) Ag⁺ + e- → Ag [0033] Electrowinning (Anode) [0034] Electrorefining (Cathode) Cu²⁺ + 2e-→ Cu [0035] Electrorefining (Anode) Cu → Cu²⁺ + 2e- [0036] According to the present disclosure, the process comprises solubilising copper in the feedstock in an aqueous media comprising a stoichiometric excess of halide complexing agent and an oxidative lixiviant to obtain a solution (210) and a solid residue, the solution (210) comprising cuprous ions. This step may broadly be referred to herein as “leaching”. [0037] Preferably, the conditions of solubilisation are selected to maximise oxidant utilisation so as to minimise cupric ions in the solution being returned to electrowinning. [0038] The pH of the aqueous media may be controlled in a particular pH range during the solubilisation of copper in the feedstock. In parts of the process, the pH range may be selected to reduce solubility of certain impurities of the feedstock. For example, the pH range may be adjusted to promote precipitation of impurities from solution such as iron, arsenic, aluminium and sulfate. [0039] The pH of the aqueous media may be controlled in a range of 1 to 3 during the solubilisation of copper in the feedstock. Preferably the pH of the aqueous media is controlled in a range of 1.5 to 2.5. [0040] The pH of the aqueous media may be controlled by any suitable material. For example, the pH of the aqueous media may controlled by the addition of hydrochloric acid, sulfuric acid, sodium hydroxide, sodium carbonate, copper hydroxide, calcium oxide, calcium carbonate, magnesium oxide, and/or magnesium carbonate. [0041] Solubilisation may be conducted at a temperature of up to the boiling temperature of the aqueous media. It will be appreciated that higher temperatures lead to improved leaching kinetics, however also increase energy requirements and may require more expensive equipment that is suitable for use with such higher temperatures. In some embodiments, where the boiling temperature is estimated at around 107°C, an operating temperature is controlled in a range of 45°C to 107°C during the solubilisation of copper in the feedstock. [0042] The copper may be solubilised in any suitable manner. For example, the copper may be solubilised in an agitated reactor. In an embodiment, the agitated reactors are operated in a counter-current fashion with respect to the feedstock and the aqueous media with solid-liquid separation in between stages. [0043] The oxidative lixiviant may comprise cupric ions. The oxidative lixiviant may comprise cupric ions of cupric halides. For example, the oxidative lixiviant may comprise cupric ions of cupric chloride, cupric bromide, and/or cupric iodide. In certain embodiments, the oxidative lixiviant comprises cupric ions of cupric chloride or other halide. [0044] The oxidative lixiviant may comprise ferric ions. The oxidative lixiviant may comprise ferric ions of ferric halides. For example, the oxidative lixiviant may comprise ferric ions of ferric chloride, ferric bromide, and/or ferric iodide. In certain embodiments, the oxidative lixiviant comprises ferric ions of ferric chloride. [0045] Additional oxidants may be utilised during the leaching phase to provide the desired solubility and valency of the metal ions prior to electrowinning. By way of non-limiting example, solubilisation may include introducing to the aqueous media sodium hypochlorite (NaOCl), sodium perchlorate (NaClO4), hypochlorous acid (HOCl), calcium peroxide (CaO2), ^{sodium persulfate (Na2S2O8), peroxymonosulfuric acid (H2SO5), peroxydisulfuric acid (H2S2O8),} hydrogen peroxide (H2O2), air, oxygen (O2), ozone (O3), or chlorine gas (Cl2). [0046] The stoichiometric excess of halide complexing agent may comprise halides derived from the cupric halide and/or ferric halide in combination with one or more halide salts. The halide salts may comprise chloride salts, bromide salts, iodide salts, or combinations thereof. The halide salts may comprise sodium halides, potassium halides, calcium halides, magnesium halides, lithium halides, or combinations thereof. [0047] In some embodiments, the stoichiometric excess of halide complexing agent comprises chloride derived from cupric chloride and/or ferric chloride in combination with one or any combination of sodium chloride, potassium chloride, calcium chloride and magnesium chloride. [0048] Cupric ions may be formed from the oxidation of cuprous ions in the solution as anolyte (220) at the second electrode (120) as the anode, the anolyte (220) comprising cupric ions returned to the aqueous media. [0049] The method further comprises electrolytically reducing cuprous ions in the solution (210) as catholyte (230) to obtain a copper deposit at a first electrode (110) as a cathode coupled with a second electrode (120) as an anode. In certain embodiments, aqueous solution streams (220) and (230) are combined. This step may broadly be referred to herein as “electrowinning” (100A), an embodiment of which is shown in Figure 1. [0050] In certain embodiments, other metals in the solution (210) such as silver may also be deposited at the first electrode (110) during electrowinning (100A). [0051] The process may further comprise physical and/or chemical treatment of the process solution (210) and solid residue. The physical and/or chemical treatment may be selected to recover sulfur or other metals such as gold, cobalt, nickel, zinc and lead as by-products. Physical treatments may be used on the residue to recover unreacted copper sulfides for recycling back to the leach, and to remove gangue materials and impurity precipitates prior to electrowinning. The process may further comprise solid-liquid separation of the solution and solid residue prior to electrolytically reducing (100A) the cuprous ions in the solution (210). [0052] An operating temperature may be controlled up to the boiling temperature for the solution (210) during the electrolytic reduction (100A) of cuprous ions in the solution. In some embodiments, an operating temperature may be controlled in a range of 45°C to 107°C during the electrolytic reduction of cuprous ions in the solution. [0053] The process may further comprise returning catholyte (230) at least partially depleted of cuprous ions to the aqueous media. [0054] The method further comprises electrolytically stripping the copper deposit from the first electrode (110) as an anode coupled with a third electrode (130). This step may broadly be referred to herein as “electrorefining” (100B), an embodiment of which is shown in Figure 2. [0055] In certain embodiments, the conditions for electrorefining (100B) may be such that other metals or metal compounds present on the first electrode (110) from the electrowinning step (100A) are insoluble and therefore remain as solid deposits on the first electrode (110) as copper is stripped from the first electrode (110). After electrorefining (100B), these metals may then be harvested and, optionally, undergo further separation and processing steps. [0056] In some embodiments, an operating temperature may be controlled in a range of 45°C to 75°C during the electrolytic stripping (100B) of the copper deposit from the first electrode (110). [0057] During the electrolytic stripping (100B), copper metal deposits on the third electrode (130). At the completion of the electrolytic stripping step (100B), the copper may be harvested from the third electrode (130). For example, the copper may be harvested by mechanical action or melting of the copper. In an embodiment, the copper is harvested by selective melting from a reusable third electrode (130). In an embodiment, the copper is harvested by mechanical separation from a reusable third electrode (130). [0058] The copper metal may be obtained at the third electrode (130) as electrolytic copper. [0059] Referring to Figures 1 and 2, in some embodiments, a first electrolytic cell may comprise the first electrode (110) and the second electrode (120) during the electrolytic reduction (100A) of cuprous ions in the solution (210) at the first electrode (110). [0060] As shown for example in Figure 1, the first electrode (110) and the second electrode (120) may be partitioned by a diaphragm (140) to form a cathode compartment and an anode compartment. The diaphragm (140) can minimise the mixing between the catholyte (230) and anolyte (220) such that oxidant generated at the anode (120) is not consumed at the cathode (110). In some embodiments, the solution (210) is separately introduced into the cathode compartment as catholyte (230) via inlet (160) and into the anode compartment as anolyte (220) via inlet (170). In some embodiments, the catholyte (230) exiting 100A is separately introduced into the cathode compartment of a subsequent cell in series and anolyte (220) is separately introduced to the anode compartment of a subsequent cell. [0061] Preferably, electrolytically stripping (100B) the copper deposit is undertaken with the same cylindrical electrode as in electrowinning (100A) cuprous ions in the solution (210) or (220). That is, in some embodiments, for example as shown in Figure 2, the cell configuration for electrorefining (100B) comprises the first electrode (110) and the third electrode (130) where the reduction of cuprous or cupric ions at the third electrode occurs during the electrolytic stripping (100B) of the copper deposit from the first electrode (110). In embodiments where a diaphragm (140) is utilised during the electrolytic reduction (100A), the diaphragm is removed from the electrolytic cell prior to the electrolytic stripping (100B). Electrolyte (240) may be introduced to the cell via either one or both of inlets (160, 170), with any unused inlet closed. For example, in the embodiment of Figure 2, electrolyte (240) is introduced to the cell via inlet (160) and inlet (170) is closed. [0062] The first electrode (110) and/or the third electrode (130) may be formed of a material comprising one of titanium, stainless steel, inconel, hastelloy, monel, carbon and copper. [0063] The second electrode (120) is an inert anode and may comprise one of titanium, carbon, titanium coated with mixed metal oxide, titanium coated with carbon, porous carbon or titanium coated with carbon felt. [0064] The first electrode (110) may be in the form of a cylindrical shell that defines a cell volume. In such embodiments, the cell volume defined by the first electrode (110) is configured to receive the second electrode (120). The second electrode (120) may comprise an anodic cylinder. The cell volume defined by the first electrode (110) is further configured to receive the third electrode (130). The third electrode (130) may comprise a cathodic cylinder. Preferably, the third electrode (130) has a greater surface area than the second electrode. [0065] The described cylindrical first electrode (110) arrangement allows for a second electrode (120) that is relatively smaller than the first electrode (110). As the second electrode (120) is typically relatively more expensive, this can reduce the capital cost of the equipment during initial set-up. Moreover, the relatively smaller second electrode (120) provides that the rate limiting step during electrowinning (100A) is the anode reaction, which helps to promote a dense and non-dendritic copper deposit. [0066] Although the present disclosure will be primarily described with regard to the above described cylindrical geometry, it will be appreciated that other arrangements and geometries may be utilised. For example, in some embodiments, the electrolytic cell may be defined by an alternating pair of first electrode (110) and second electrode (120), in the form of flat plates that are positioned in a spaced, parallel configuration. [0067] During electrowinning (100A), the first electrode (110) and the second electrode (120) are co-axially positioned and spaced apart, defining an annular volume between the respective surfaces. The first electrode (110) and second electrode (120) are preferably sufficiently spaced to allow for a suitable amount of copper on the surface of the first electrode (110) while keeping the power requirements due to the resistance in the solutions (210, 220, 230) at a reasonable level. In an embodiment, the first electrode (110) and the second electrode (120) are spaced from 0.5 cm to 4 cm. [0068] The ratio of first electrode:second electrode (110:120) surface area is from 1.05:1 to 6.0:1, for example from 1.2:1 to 6.0:1, or from 2.0:1 to 6.0:1. In one embodiment, the ratio of first electrode:second electrode (110:120) surface area is 5.62:1. In another embodiment, the ratio of first electrode:second electrode (110:120) surface area is 2.54:1. [0069] During electrorefining (100B), the first electrode (110) and the third electrode (130) are co-axially positioned and spaced apart, defining an annular volume between the respective surfaces. The first electrode (110) and third electrode (130) are preferably sufficiently spaced to allow for a suitable amount of copper on the surface of the third electrode (130) while keeping the power requirements due to the resistance in the electrolyte (240) at a reasonable level. In an embodiment, the first electrode (110) and the third electrode (130) are spaced from 0.5 cm to 4 cm. [0070] The ratio of first electrode:third electrode (110:130) surface area is from 1.05:1 to 6.0:1. [0071] It will be appreciated that the second and third electrodes (120, 130) may be interchangeable within the cell volume defined by the first electrode (110) such that the steps of electrowinning (100A) and electrorefining (100B) may be undertaken in the same electrolytic cell. [0072] Prior to receiving the third electrode (130) in the cell volume, catholyte (230) and anolyte (220) may be discharged from the cell volume, for example via drain (150), and an electrolyte (240) introduced into the cell volume. The electrolyte (240) may be any suitable electrolyte (240) for electrorefining (100B). For example, the electrolyte (240) may comprise sulfuric acid and copper sulfate. [0073] The electrolytic cell may undergo various treatment steps in between alternating electrowinning (100A) and electrorefining cycles (100B). [0074] In some embodiments, the cell volume may be flushed at various points in the process. The flushing may assist in removing contaminants and recovering precious metal containing materials such as insoluble slime from the electrolytic cell. For example, during electrorefining (100B), it may be expected that some precious elements such as silver, gold, platinum and palladium will remain on the first electrode (110). The slimes may fall to the bottom of the electrolytic cell during electrorefining (100B) or during the flushing cycle following electrorefining. The recovered insoluble slime may undergo further processing to recover any precious elements present within the slime. [0075] It will be appreciated other metals present in the copper-containing feedstock may be recovered at many points during the process, including from pre-processing, during leaching, and from the electrolytic steps (100A, 100B) as described above. In some embodiments, precious metals such as silver, gold, platinum and palladium may be separated from the leach solution prior to electrowinning (100A) by adsorption onto activated carbon, by electrochemical reduction onto a relatively reactive metal such as zinc, iron, aluminium, titanium, magnesium or copper, and/or by selective precipitation techniques. [0076] Flushing the electrolytic cell may be undertaken during and/or after discharge of catholyte (230), anolyte (220), and/or electrolyte (240) from the cell. Additionally or alternatively, flushing may be undertaken after obtaining copper metal at the third electrode (130). [0077] The flushing may be conducted using a cell flush solution comprising weak acid, and/or weak acid in halide brine, and/or water. The flushing may further comprise high pressure washing of the cell. Additionally or alternatively, the flushing may comprise chemically cleaning of the cell, for example with nitric acid. [0078] The electrolytic cell may undergo pretreatment prior to electrowinning (100A). In some embodiments, a solution comprising copper sulfate may be used prior to electrowinning (100A) to precoat the first electrode (110) with a layer of copper thereby reducing the hydrogen generation potential that can occur in the initial stages of electrowinning (100A). Such pre- coating of the first electrode (110) may further assist in improving current efficiency, improving copper electrodeposit morphology, and reducing acid consumption. [0079] If carbon is used as the first electrode (110), the carbon may first undergo a pre- treatment to apply a conductive polymeric coating to improve deposit adherence and/or deposit morphology. [0080] A number of electrolytic cells may be provided in series. The process may then comprise electrolytically reducing cuprous ions in catholyte partially depleted of cuprous ions by the first electrolytic cell in one or more additional electrolytic cells to obtain a copper deposit at a first electrode (110) as a cathode coupled with a second electrode (120) as an anode of each of the one or more additional electrolytic cells. [0081] In some embodiments, the fluid in the cell will be oscillated up and down via a repetitive pulsing action on the fluid by a mechanical device or using compressed gas, to provide enhanced mass transfer during the electrochemical reactions. This will enable efficient operation of the cells in a batch mode of operation or when the continuous solution flow is slow. [0082] In some embodiments, the first electrode (110) may be subjected to nitric acid prior in between alternating electrowinning (100A) and electrorefining (100B) cycles, that is prior to introduction of the second electrode (120) or third electrode (130) into the cell volume. [0083] It will be appreciated that processes in accordance with the present disclosure can allow for the electrochemical production of high-quality copper with significant reductions in the energy required to produce the copper. EXAMPLES [0084] Aspects of the present disclosure are now described further in the following non- limiting examples. [0085] Experimental apparatus and materials [0086] A 3 L stainless steel vessel was used in a first test (SE1) to hold the solids and most of the liquor; it corroded and failed. [0087] Subsequent tests (SE2-SE6) used a 2 L glass vessel, however it was found some of the silica was leached into the solution. [0088] In the final 2 experiments (SE7 and SE8) a 2 L plastic vessel was used to prevent silica contamination. [0089] The electrolyte used had a composition of 175 g/L NaCl, 1g/L HCl and 30 g/L Cu(I)Cl made up with deionised water (DI). The electrolyte was filtered and reused for each of the experiments. [0090] An overhead stirrer was used in conjunction with a Teflon impeller in the liquor holding tank. A TPS WP-80D pH meter was used to measure the pH and ORP in the holding tank. The vessel was heated using an IKA C-MAG HS10 hotplate. A nitrogen sparger was used for the holding tank along with plastic wrap to minimise exposure to the atmosphere. The contents of the holding tank were recirculated through the electrowinning cell using a peristaltic pump. [0091] The cell unit was a stainless-steel tubular cathode (~ 800 mL volume) that uses a conductive graphite rod anode; the cathode surface area was 459 cm² and the anode surface area was 81.5 cm² with a 3 cm cathode-anode spacing. [0092] A DC Teledyne power supply unit of 12 V and 30 A was used to provide power to the electrowinning cell. [0093] Experimental procedures (1) [0094] The feed tank was placed onto a hotplate and the stirring unit, the pH probe, ORP probe, hotplate thermocouple, stirring rod, sparger, and inlet and outlet tubes were lowered into the vessel. [0095] The inlet tube was placed close to the liquid surface in the feed tank to minimise solids intake. The inlet tube feeds to the bottom of the electrowinning cell via the peristaltic pump. The holding tank and cell unit were insulated to minimise heat losses. [0096] The electrolyte solution was then gradually poured into the holding tank with the solids, and the overhead stirrer started. Once the liquor was at the desired temperature, the pump was started. This was left to run until the air in the cell unit was displaced. [0097] The pH was adjusted using concentrated 32% HCl to a desired level. An initial sample was taken for ICP analysis. The electrodes were connected and the power supply then turned on, with the voltage being controlled and the current being allowed to drift. In most tests, the pH was maintained at the desired level through addition of the same acid however in test SE5 the pH was left to drift and in SE8 acid was added at regular intervals regardless of pH. [0098] The tests were run for 5 hours, with the exceptions of tests SE1 (due to vessel failure) and SE2 (due to runtime issues). Samples were taken for ICP analysis every 30 minutes for the first 2 hours and then every 60 minutes thereafter. ICP samples were filtered using a 0.45- micron syringe filter. Conditions were kept constant (see summary provided in Table 1 below), although in some tests (SE1 and SE7) voltage and stirring rate were varied. Insoluble material was present in the filtered ICP samples (made with 10% HNO3). After one week at room temperature the material dissolved and was later identified as a copper silicate phase. [0099] At the completion of each test, the power supply, stirring, heating and pumping were turned off. The contents in the tubes, holding tank, and cell were drained to recover the electrolyte solution. This solution was then pressure filtered to remove any solids. The cell was opened, and any entrained solids were removed using DI water. The solids were recovered and placed in an oven at 105°C overnight to allow a mass balance reconciliation. The holding tank and cell were then reconnected. A 2L 5% nitric acid solution was then run through the call overnight to recover the plated copper. The recovered copper solution was then sampled and sent to ICP for analysis to determine amount of copper plated. _{. . i} ⁿ M e_r ^V _{g i} 2 _{; i} ⁿ _. P R^. _{g . .} ^d _{l t} o_s ^a o o ^t _i ⁿ d ^{t t} n d _e ^m ^{s d} 0 _i ^{d o}C c 8 7 _. ^e p ba m T ^e _T d H p _i ^er _a ⁸ _.1 ⁸ _.1 ⁹ _.1 ⁸ _.2 ⁴ _.2 ⁸ _.1 ¹ _.3 V e m₎ i _T ^h ₍ 2 4 5 5 5 5 5 5 g _i ⁿ ^d _a o ₎ _{L .} ⁴ _. ¹ _. ⁶ _. 1 9 9 s ^L _/ g ₍ 77 0 6 ⁷4 _. ²6 51 81 81 d 5 5 9 9 i_l o _S _{l e} _i ^{ar r t} _e _{a i} ^{c e} _{t i} ^tr e_e t p ^r _tn ^t _e ⁱ _c _a p ^o _yp o ^e _c ^h _tn _c ^l M Cn _a ^o _c ^l o ^y C _S h C _ah C t _x _s ⁱ ^e _r _T ^t _a 1 E 2 E 3 E 4 5 6 7 8 M _{S S S} ^E _S ^E _S ^E _S ^E _S ^E _S [0100] Results (1) [0101] The results of the tests are summarised Tables 2-5 below. In addition, it was observed that the copper deposited in accordance with the described tests was smooth and showed no indication of dendritic copper. [0102] In considering the results, it is important to note that the solids added into the experiments varied, with SE1 using copper concentrate, SE2-6 using synthetic chalcocite and SE7-8 using a raw chalcopyrite sample. With reference to Table 2, Test SE3 has the best results with regard to Test 2 having the highest current density and current efficiency, and the lowest specific energy and acid consumption. The chalcopyrite tests yielded relatively poorer results with lower current densities and efficiencies and higher energy and acid consumption compared to the chalcocite tests. Nitrogen sparging was found to improve the process. [0103] With reference to Table 2, specific energy consumptions as low as 1.29 kWh/kg-Cu (4.64 GJ/t-Cu) were achieved with the process. Despite relatively low current efficiencies, this represents significant energy saving compared with conventional copper electrowinning which requires about 2 kWh/kg-Cu (7.2 GJ/t-Cu) even when operating at approximately 90% current efficiency. With reference to Table 2, the requirement for acid addition is largely related to oxygen ingress into the solution as well as the corrosion of the stainless steel. Table 2: Summary of energy and acid consumption d SE8 15.7 16.6 2.31 1.97 Table 3: Initial solids loadin and recovered solids SE8 500 (13% H2O) 380 5 5 0 2 08 46 3 8 8 3 2 0 9 6 _S 7 5 9 4 6 1 3 2 8 10 0 7 1 5 1 0 1 6 7 7 8 9 0 2 7 7 8 9 1 1 1 1 1 1 87 7 _i 1 7 1 1 8 3 1 8 4 1 0 3 2 9 6 1 5 7 3 N 8 1 1 0 6 2 8 2 1 8 7 1 9 2 1 9 8 1 9 9 2 84 2 0 0 0 0 0 1 qⁱ _l 2 1 la 3 4 ⁿ _i 2 4 9 8 9 9 7 7 0 8 0 9 5 7 F ^e 9 9 0 8 8 3 3 1 8 89 29 94 58 12 _{: F} 8 7 5 0 6 5 1 9 9 9 6 5 81 13 39 16 73 12 00 29 0 ^e _l 4 b 5 1 4 1 6 1 8 1 8 9 7 8 a u 8 2 8 5 6 1 2 9 7 8 2 0 9 7 C 4 2 6 4 3 7 2 0 1 1 3 33 52 92 23 T 41 71 71 23 73 52 12 43 76 2 1 4 78 88 02 5 1 4 0 _r 6 2 C 4 3 3 2 39 29 61 3 6 1 2 32 23 o 5 6 6 3 6 5 6 7 7 9 11 C 6 8 7 9 1 0 0 6 6 5 9 9 9 4 _a 0 0 25 6 4 0 0 7 8 4 6 1 C 6 71 0 0 0 0 0 21 85 _i B 0 0 0 0 0 0 22 08 2 2 1 3 3 5 82 B 2 1 2 1 2 2 01 24 8 2 0 _l 1 1 2 92 73 41 41 A 91 21 31 81 8 91 51 41 2 E 3 4 5 6 7 8 1 S ^E _S ^E _S ^E _S ^E _S ^E _S ^E _S ^E 2 3 4 5 6 7 8 S ^E _S ^E _S ^E _S ^E _S ^E _S ^E _S ^E _S [0104] Experimental procedures (2) [0105] The previous experimental conditions were maintained with the following changes. [0106] The cylindrical cathode in the previous series of experiments was a stainless-steel tubular cathode (~ 800 mL volume). However, the stainless steel cathode failed due to excessive corrosion and was replaced with a carbon tubular cathode (~ 200 ml volume) that uses a conductive graphite rod anode. The cathode surface area in this experimental set-up was 242 cm² and the anode surface area was 87.8 cm² with a 1.015 cm cathode-anode spacing. [0107] Second, a jacketed comproportionation reactor was added between the feed tank and the electrowinning cell. This reactor was packed with copper wire and copper shavings and heated to 60°C with a recirculating water bath. The reactor was fed from the feed tank via a peristaltic pump to the base of the reactor. The reactor discharge from the top of the reactor gravity fed the electrowinning cell to the base of the cell. [0108] Third, the liquor being recirculated did not contain any solids. The liquor used was the same liquor used for all of the experiments which was filtered through a 0.45 µm membrane filter and the pH adjusted to ~1.5 prior to beginning the first experiment with the carbon (graphite) cathode cell. [0109] Results (2) [0110] In a first experiment with the graphite anode and graphite cathode cell, the cell voltage was maintained between 0.8 and 1.2 V for a total of 75 hours total run time. The cell was then opened and a large non-dendritic copper deposit was seen at the cathode. Overall, this test with the graphite cell had a current efficiency of approximately 62% with about 139 g of copper deposited and associated electrowinning specific energy consumption of 0.6 kWh/kg-Cu. [0111] In a second experiment with the graphite anode and graphite cathode cell, the anode was enclosed in a porous polypropylene (PP) mesh tube diaphragm with a spacing of ~5 mm for the entire length and the cell reassembled. [0112] The electrowinning experiment was repeated with the anode with the diaphragm separator which improved specific energy consumptions to 0.4 kWh/kg-Cu (1.44 GJ/t-Cu) and associated current efficiency of 80%. An image of the electrowon copper is shown in Figure 3 where it can be seen that the copper is evenly deposited, dense, and non-dendritic. The copper deposited from this experiment was subsequently electrorefined through conventional copper electrorefining electrolyte solution comprising dissolved copper sulfate and sulfuric acid that was circulated through the cell. The electrorefined copper was deposited onto a titanium cathode and the purity of the copper was measured to be 99.94 weight % copper, based on partial dissolution in nitric acid and solution assay. [0113] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS: 1. A hydrometallurgical process for obtaining copper metal from a copper-containing feedstock, the process comprising: - solubilising copper in the feedstock in an aqueous media comprising a stoichiometric excess of halide complexing agent and an oxidative lixiviant to obtain a solution and a solid residue, the solution comprising cuprous ions; - electrolytically reducing cuprous ions in the solution as catholyte to obtain a copper deposit at a first electrode as a cathode coupled with a second electrode as an anode; - electrolytically stripping the copper deposit from the first electrode as an anode coupled with a third electrode as a cathode and obtaining copper metal at the third electrode. 2. The hydrometallurgical process of claim 1, wherein the oxidative lixiviant comprises cupric ions and/or ferric ions. 3. The hydrometallurgical process of claim 2, wherein the oxidative lixiviant comprises cupric ions of cupric halides and/or ferric ions of ferric halides. 4. The process of claim 3, wherein the stoichiometric excess of halide complexing agent is derived from the cupric halides and/or ferric halides in combination with one or more halide salts. 5. The process of any one of the preceding claims, wherein the stoichiometric excess of halide complexing agent comprises chloride derived from cupric chloride and/or ferric chloride in combination with one or any combination of sodium chloride, potassium chloride, calcium chloride and magnesium chloride. 6. The process of any one of the preceding claims, wherein a first electrolytic cell comprises the first electrode and the second electrode during the electrolytic reduction of cuprous ions in the solution at the first electrode, and reduction of cuprous or cupric ions at the third electrode during the electrolytic stripping of the copper deposit from the first electrode. 7. The process of claim 6, wherein the first electrode and the second electrode are partitioned by a diaphragm to form a cathode compartment and an anode compartment. 8. The process of claim 7, wherein the solution is separately introduced into the cathode compartment as catholyte and into the anode compartment as anolyte. 9. The process of any one of claims 6 to 8, wherein the first electrolytic cell comprises the first electrode as a cylindrical shell defining a cell volume configured to receive, respectively: - the second electrode comprising an anodic cylinder; and - the third electrode comprising a cathodic cylinder. 10. The process of claim 9, wherein the third electrode has a greater surface area than the second electrode. 11. The process of claim 9 or claim 10, wherein: - a ratio of surface area of first electrode:second electrode is from 1.05:1 to 6:1; - a ratio of surface area of first electrode:third electrode is from 1.05:1 to 6:1; - the second electrode is spaced from the first electrode by from 0.5cm to 4cm; and/or - the third electrode is spaced from the first electrode by from 0.5cm to 4cm. 12. The process of claim 9 or 10 comprising: - discharging catholyte and anolyte from the cell volume; and - introducing an electrolyte into the cell volume, prior to receiving the third electrode in the cell volume. 13. The process of claim 11 comprising subjecting the first electrode to nitric acid before and/or after receiving the second electrode and/or the third electrode in the cell volume. 14. The process of any one of claims 11 to 13 comprising flushing the cell volume during and/or after discharging catholyte and anolyte or electrolyte from the cell volume and/or after obtaining copper metal at the third electrode to recover insoluble slimes. 15. The process of any one of the preceding claims comprising recovering one or more precious metals such as silver, gold, platinum or palladium, from the copper-containing feedstock, wherein the one or more precious metals are recovered from: - precious metals solubilised in the solution during solubilisation of copper; - the solid residue formed during solubilisation of copper; - precious metal deposited on the first electrode during the electrolytic reduction of cuprous ions; and/or - recovered insoluble slimes from electrolytic steps. 16. The process of any one of claims 6 to 15 comprising electrolytically reducing cuprous ions in catholyte partially depleted of cuprous ions by the first electrolytic cell in one or more additional electrolytic cells to obtain a copper deposit at a first electrode as a cathode coupled with a second electrode as an anode of each of the one or more additional electrolytic cells. 17. The process of any one of the preceding claims comprising returning catholyte at least partially depleted of cuprous ions to the aqueous media. 18. The process of any one of the preceding claims, wherein: - the first electrode and/or the third electrode comprising one of titanium, stainless steel, inconel, monel, hastelloy, carbon and copper; and/or - the second electrode is an inert anode comprising one of titanium, carbon, titanium coated with mixed metal oxide, titanium coated with carbon, porous carbon or titanium coated with carbon felt. 19. A hydrometallurgical process to obtain copper from a copper-containing feedstock, the process comprising: - solubilising copper in the feedstock in an aqueous media comprising a stoichiometric excess of halide complexing agent and an oxidative lixiviant to obtain a solution and a solid residue, the solution comprising cuprous ions; and - electrolytically reducing cuprous ions in the solution as a catholyte to obtain the copper as a deposit at a first electrode as a cathode of an electrolytic cell and coupled with a second electrode as an anode of the electrolytic cell, the first electrode comprising a cylindrical shell defining a cell volume configured to receive the second electrode comprising an anodic cylinder therein. 20. An electrolytic cell for obtaining copper metal from a chloride solution comprising cuprous ions, the electrolytic cell comprising: - a first electrode comprising a cylindrical shell and defining a cell volume, the cell volume configured to receive, respectively: - a second electrode as an anodic cylinder; and - a third electrode as a cathodic cylinder, wherein the first electrode coupled with the second electrode electrolytically reduce cuprous ions in the solution to obtain a copper deposit at the first electrode as a cathode and the third electrode coupled with the first electrode electrolytically strips the copper deposit from the first electrode as an anode to obtain copper metal at the third electrode.