Method for producing granulated copper

Abstract

A method for producing copper particulates on the surface of a reduced metal. The method may include contacting the reduced metal with an aqueous solution comprising a copper(II) salt and a halide. The molar ratio of the halide to the copper(II) in the copper(II) salt may be at least about 3:1. Particulate copper may be produced on the surface of the reduced metal and is optionally removed from the surface of the reduced metal by shaking, washing, and / or brushing, and / or optionally by agitation and / or circulation of the aqueous solution.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 202,486, filed June 14, 2021, the entire contents of which are incorporated herein by reference.

[0002] FIELD OF THEINVENTION The present disclosure relates to a method for producing particulate copper metal comprising reducing a copper(II) salt in the presence of a halide. [Background technology]

[0003] The following paragraphs are not an admission that anything described therein is prior art or part of the knowledge of the person skilled in the art.

[0004] The first recorded displacement of copper from a solution of copper sulfate by elemental iron appears to have been published around 1775 by Torburn Olof Bergman, who wrote that "...iron added to a solution (of copper sulfate) is immediately observed to be covered with a copper-coloured pellicle, for it produces a portion of the phlogiston necessary for the reduction of copper, and thereby renders itself soluble without giving off any combustible air." 1 In this account, copper appears as a film (pellicle) on the surface of iron immersed in a copper sulfate solution. In more recent sources, this appearance is described as the copper being precipitated as "cement," and the process as "cementation."

[0005] An early patent describing the production of copper from chloride-rich copper solutions is US Pat. No. 86,754. The use of chlorides in the production of copper from ores is based on two distinctly independent methods. The first method, which has been widely used, is in the generation of suitable lixiviants such as FeCl2, FeCl3, CuCl2, and CuCl, which act on sulfide ores to solubilize the copper. The second method was first described by Hunt and Douglas in the above-mentioned patent and in subsequent updates by the same authors (US Pat. No. 227,902 and US Pat. No. 364,174). US Pat. No. 227,902 instructs the addition of "some soluble chloride, such as common salt, in the ratio of 2 pounds of salt to each pound of dissolved copper (i.e., a molar ratio of chloride to copper of slightly more than 2:1)." No explanation or justification for this amount of NaCl is provided in the patent.

[0006] U.S. Patent No. 3,902,896 discloses the use of an additive to produce copper deposits that flake off of a surface. The method identifies the additive as a thiosulfate salt used in a weak acid solution.

[0007] WO 2009 / 007792(A1) discloses a method for producing copper from a solution containing copper(II) salts. The method comprises a first step of reducing at least a portion of the copper(II) salts to copper(I) salts, solubilizing the copper(I) salts to produce soluble copper(I) complexes (optionally in the presence of a soluble halide), and reducing the soluble copper(I) complexes to copper in a second reduction step. The use of sulfite is proposed for the first partial reduction reaction to produce Cu(I). This first partial reduction produces only catalytic amounts of Cu(l), since the subsequent reduction to produce Cu(0) produces more Cu(l) to be reduced until all the copper in the solution is reduced to the metal. The solubilization step can be carried out simultaneously with complexation with chloride. The complexation reaction is proposed to include the addition of an "excess" chloride, which is then added to the solution to produce CuCl4. 3- This suggests that it is necessary to generate

[0008] The effect of chloride on the properties of copper produced by reduction reactions has been reported to depend on the chloride concentration; at low concentrations, the presence of chloride has been reported to enhance the lightness of the copper that can be plated, but high chloride concentrations result in overall surface roughening. Surface roughening is considered undesirable in the industry, and publications reporting on the issue typically document the appearance of this roughening effect at chloride concentrations up to 2.5M. For example, Kao et al. 2 reported that the presence of chloride caused the precipitation of CuCl on the surface of copper during reduction. This phenomenon was observed at chloride concentrations up to 2.5 M, but at this concentration the effect was small. At high levels of chloride (9 M LiCl), soluble higher complexes of copper (e.g., CuCl2 or CuCl 2- The formation of CuCl prevents any accumulation of CuCl and allows for complete reduction of copper.

[0009] Several authors have commented on the importance of the anion concentration on the surface morphology of deposited copper. 3,4,5 For example, Carneval et al. teach that it is important to control the chloride ion concentration between 60 and 80 ppm; below 30 ppm the deposit will be dull, streaky, rough, and step-plated; above 120 ppm the deposit will be coarse-grained, dull, and the anode will polarize and stop plating. Carneval et al. also show that the elongation of the copper deposit in each case is greater than 10 mg L -1 Carneval et al. further noted that, among the halides, Cl was found to be sufficient over a wide range of concentrations (40-150 mg L−1) to maintain the stress at the null value. -1 ) and is most effective over a range of approximately 50 mg / L -1 It is taught that the presence of chloride is optimal to allow for increased microhardness without increasing internal stresses, and that the chloride ions do not affect throwing power.

[0010] Copper crystals have been precipitated using iron as the reducing metal from aqueous copper(II) sulfate in the presence of sodium chloride. For example, Rychkov et al. reported the formation of copper crystals using a system in which successive layers of copper sulfate, sodium chloride, filter paper, and an iron source were immersed in a saturated solution of sodium chloride. 6 Similarly, Mathur et al. disclose experiments in which copper metal crystals were formed using a system in which copper(II) sulfate crystals were placed at the bottom of a jar, this layer was covered with sodium chloride powder, filter paper was placed on the salt, an iron plate was placed on top of the paper, and the jar was then filled with a saturated solution of sodium chloride to about 1.5 inches above the iron plate. 7 In both of these examples, the purpose was to illustrate the formation of copper crystals. In neither case did the authors investigate the reaction with any other purpose than the production of macroscopic crystalline copper. The paper by Rychov et al. describes an exercise for high school students, in which they asked the students to vary the parameters of the reaction and then perform crystallographic measurements on the copper crystals. In the second case, it appears to be for aesthetic purposes. The method description in the paper does not describe any optimization of either crystal size or yield, and there is no reported information on the amounts of reagents used. Summary of the Invention

[0011] Introduction The following is intended to introduce the reader to the following detailed description, but is not intended to define or limit the claimed subject matter.

[0012] There is a continuing need for processes for the deposition of particulate copper metal on reduced metal surfaces, e.g., copper leaching processes, that facilitate the removal and collection of copper metal from the reduced metal surface. Such hydrometallurgical processes can free up smaller, isolated deposits for copper extraction that were previously thought to be uneconomical to develop using conventional, larger-scale pyrometallurgical processes that involve significant greenhouse gas emissions. Energy usage is significantly reduced because the energy stored in recycled iron is effectively reused in chemical extraction processes.

[0013] Copper was advantageously reduced to granular metallic copper in a single step from a solution containing copper, sulfuric acid, and a halide (NaCl). The advantage of the method described herein is that the granular copper produced on the surface of the reduced metal can be weakly attached to the surface and can therefore be removed from the surface by techniques such as shaking, washing, and / or brushing the metal, and / or assisted by agitation and / or circulation of the aqueous solution. Thus, the weakly bound copper on the iron surface can be easily collected and washed clean of the supernatant solution, and then melted into a suitable form, for example as a copper anode that can be placed in an electrolytic cell to produce cathodic copper in a form acceptable for trading on the London Metal Exchange. This method differs from the cementation method, which occurs when the copper in the solution is present mainly as hydrated cations. In this case, the copper tends to be more strongly held to the surface, described as a "skin" or cement, and must be removed by more aggressive scraping.

[0014] Accordingly, the present disclosure includes a method of producing granular copper metal, the method comprising: contacting a reduced metal with an aqueous solution, the aqueous solution comprising: (i) a copper(II) salt; (ii) a halide; The molar ratio of halide to copper(II) in the aqueous solution is at least about 3:1, and particulate copper is produced on the surface of the reduced metal and optionally removed from the surface of the reduced metal by shaking, washing, and / or brushing, and / or optionally by agitation and / or circulation of the aqueous solution.

[0015] Other aspects and features of the teachings disclosed herein will become apparent to those of ordinary skill in the art upon review of the following description of specific examples of the present disclosure. [Brief description of the drawings]

[0016] The drawings included herein are for purposes of illustrating various examples of the disclosed devices and techniques and are not intended to limit the scope of the teachings in any way.

[0017] [Figure 1] Illustrated are exemplary photographs of copper deposits on an iron rod from a weakly acidic (pH 2) solution containing 0.8371 M CuSO4 and various amounts of NaCl (2, 3, 4, and 5 equivalents from the second to the bottom row) according to examples of the disclosure compared to copper deposits on an iron rod from an acidic (pH 2) solution containing 0.8371 M CuSO4 and no NaCl (top row) at 30, 60, 90, 120, and 150 minutes from left to right. [Diagram 2] Illustrated are exemplary photographs of copper deposits on an iron rod from solutions containing 0.8388 M CuSO4 and various amounts of NaCl (3 or 5 equivalents) according to examples of the present disclosure (top row, center and right photographs, respectively) compared to copper deposits on an iron rod from a solution containing 0.8388 M CuSO4 and no NaCl (top row, left image) after 2 hours, as well as the iron rod after removal of the copper deposits (bottom images, 0, 3, and 5 equivalents of NaCl from left to right). [Diagram 3] 1 is a plot showing the percentage of copper grains having sizes greater than 860 μm, 250-860 μm, 88-250 μm, and less than 88 μm from a small scale method compared to a large scale method for preparing copper grains according to examples of the present disclosure, from left to right. [Figure 4] 1 is a plot showing the percentage of copper grains having sizes from left to right of greater than 860 μm, 250-860 μm, and 88-250 μm resulting from a method for preparing copper grains using 3.5 equivalents of NaCl compared to a duplicate run using 4.1 equivalents of NaCl according to an example of the present disclosure. [Diagram 5] 1 is a plot showing particle size distribution and reaction yield as a function of reaction time for a method for preparing copper particles from a stock solution of CuSO4 using 5 equivalents of NaCl according to an example of the present disclosure. Values ​​are the average of three experiments. [Figure 6]FIG. 1 is a plot showing particle size distribution and reaction yield as a function of reaction time for a method for preparing copper nuggets from an exotic copper ore leach solution compared to a stock solution of CuSO4 using 5 equivalents of NaCl according to an example of the present disclosure. [Figure 7] 1 shows exemplary photographs of copper deposits on iron bars from solutions according to examples of the present disclosure including, from left to right, 0.1432M, 0.2772M, 0.3867M, and 0.5100M CuSO4 and 4.5 equivalents of NaCl after 120 minutes. [Figure 8A] 1 shows copper metal produced from an exemplary 4:1 initial chloride to copper ratio. [Figure 8B] 1 shows copper metal produced from a comparative 1:1 initial chloride to copper ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Various devices or methods are described below to provide examples of embodiments of each claimed invention. The embodiments described below do not limit the claimed inventions, and any claimed invention may encompass devices and methods other than those described below. The claimed inventions are not limited to devices and methods having all of the features of any one device or method described below, nor are they limited to features common to more than one or all of the devices or methods described below. The devices or methods described below may not be embodiments of the claimed invention. Any inventions disclosed in the devices or methods described below that are not claimed herein may be the subject of other means of protection, such as a continuing patent application, and the applicants, inventors, and / or owners do not intend to abandon, abandon, or offer to the public any such inventions by their disclosure in this document.

[0019] I. Definition Unless otherwise indicated, the definitions and examples set forth in this section and other sections are intended to be applicable to all examples and aspects of the disclosure described herein where they are suitable, as would be understood by one of skill in the art.

[0020] In understanding the scope of the present disclosure, as used herein, the term "comprising" and its derivatives are intended to be open-ended terms specifying the presence of stated features, elements, components, groups, integers, and / or steps, and do not exclude the presence of other unstated features, elements, components, groups, integers, and / or steps. The above also applies to words having similar meanings, such as the terms "including" and "having" and their derivatives. As used herein, the term "consisting" and its derivatives are intended to be open-ended terms specifying the presence of stated features, elements, components, groups, integers, and / or steps, and exclude the presence of other unstated features, elements, components, groups, integers, and / or steps. As used herein, the term "consisting essentially of" is intended to specify the presence of stated features, elements, components, groups, integers, and / or steps, as well as the presence of those that do not substantially affect the basic and novel properties of the features, elements, components, groups, integers, and / or steps.

[0021] As used herein, terms of degree such as "substantially," "about," and "approximately" refer to a reasonable amount of deviation from the modified term such that the end result is not significantly altered. If this deviation does not negate the meaning of the word it modifies, these terms of degree should be interpreted as including at least ±5% deviation from the modified term.

[0022] As used herein, the term "and / or" means that the listed items may be present or used either individually or in any combination. In effect, the term means that "at least one of" or "one or more" of the listed items are used or present.

[0023] As used in this disclosure, the singular forms "a," "an," and "the" include plural references unless the content clearly dictates otherwise.

[0024] As used herein, the term "suitable" means that the selection of a particular reagent or condition will depend on the reaction being performed and the desired outcome, but nevertheless can generally be made by one of ordinary skill in the art knowing all the relevant information.

[0025] As used herein, the term "reduced metal" refers to a metal that reduces copper(II) to copper(0) in the methods of the present disclosure.

[0026] As used herein, the term "halide" refers to halogen anions and includes chloro and bromo.

[0027] As used herein, the term "granule" refers to a particle of any size having a generally irregular shape.

[0028] As used herein, the term "crystal" refers to a solid material whose components (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure to form a crystal lattice that extends in all directions.

[0029] II. Method Copper was advantageously reduced to granular metallic copper in a single step from a solution containing copper, sulfuric acid, and a halide (NaCl). This one-step reduction is advantageous over other methods because it does not rely on an intermediate step in which copper is reduced from a +2 to a +1 oxidation state, for example, prior to the reduction of Cu(l) to Cu(0). In the disclosed method, copper ore may in some instances be leached with sulfuric acid to obtain a solution containing copper(II) salts, after which sodium chloride or sulfuric acid containing sodium chloride may be added. In both cases, the chloride concentration is adjusted so that essentially all of the copper in the pregnant liquor is converted to CuCl4. 2-is present in a sufficiently high concentration to ensure that the copper is in the form of CuCl3-, e.g., about 3 to 5 times the molar concentration of copper(II) in the solution containing the copper(II) salt. For example, at a molar concentration of about 3:1, it will be appreciated that a significant portion is likely to be CuCl3- at the start of the reaction. As the copper precipitates, the predominant species will be CuCl4 2- The solution containing copper(II) salts was exposed to the reduced metal, which in these examples was an iron rod. The temperature was ambient. Under these conditions, copper was produced on the surface of the iron in the form of visible grains that in some examples grew to a size of more than 1 mm. Copper grains having a grain size of more than 88 μm accounted for 99% of the copper, and 79% had a grain size of more than 250 μm. An advantage of the method described herein is that the granular copper produced on the surface of the reduced metal surface is weakly attached to the surface and can therefore be removed from the surface by techniques such as shaking, washing, and / or brushing the metal, and / or optionally by agitation and / or circulation of the aqueous solution.

[0030] Accordingly, the present disclosure includes a method of producing granular copper metal, the method comprising: contacting a reduced metal with an aqueous solution, the aqueous solution comprising: (i) a copper(II) salt; (ii) a halide; The molar ratio of halide to copper(II) in the aqueous solution is at least about 3:1, and particulate copper is produced on the surface of the reduced metal and optionally removed from the surface of the reduced metal by shaking, washing, and / or brushing, and / or optionally by agitation and / or circulation of the aqueous solution.

[0031] In some examples, the molar ratio of the halide to copper(II) in the aqueous solution is about 3: 1. In some examples, the molar ratio of the halide to copper(II) in the aqueous solution is at least 3: 1. In some examples, the molar ratio of the halide to copper(II) in the aqueous solution is from about 3: 1 to about 5: 1.

[0032] The reducing metal can be any suitable reducing metal. For example, one skilled in the art will readily appreciate that sodium (Na) and potassium (K) metals are too reactive for the present method, e.g., reacting with water in aqueous solutions. Thus, sodium, potassium, and similar metals would not be understood to be suitable reducing metals for the presently disclosed method. In contrast, iron (Fe) has the advantage of being low cost, and in the presently disclosed examples, it has been observed that the adhesion of granular copper to the surface of the metal is weak, forming suitable macroscopic granular copper. Thus, iron is desirably reactive, e.g., to provide copper as easy-to-handle particles for subsequent work-up. Thus, in some examples, the reducing metal is iron. Other reducing metals that may be useful in the presently disclosed method are zinc (Zn), aluminum (Al), calcium (Ca), and / or magnesium (Mg). Thus, in some examples, the reducing metal is selected from iron, zinc, aluminum, calcium, magnesium, and combinations thereof. In some examples, the reducing metal is included in a suitable alloy. For example, suitable alloys of iron include steel (an alloy containing iron, carbon, and optionally other elements, where the carbon is present in an amount of about 2% by weight or less, based on the total weight of the alloy) and cast iron (an alloy containing iron, carbon, silicon, and optionally other elements, where the carbon is present in an amount of greater than 2% by weight, based on the total weight of the alloy).

[0033] The reduced metal may be in any suitable form. For example, a form having a high surface area may be advantageous. Suitable forms include plates, rods, bars, beams, scrap, or combinations thereof. Thus, in some examples, the reduced metal is in the form of plates, rods, bars, beams, scrap, or combinations thereof. In some examples, the reduced metal is in the form of plates having a substantially flat surface.

[0034] The halide is any suitable halide. For example, copper bromide would be expected by one of skill in the art to react similarly to copper chloride. In some examples, the halide is chloride, bromide, or a combination thereof. In some examples, the halide is chloride.

[0035] In some examples, the halide is present in a graininess-promoting amount. In some examples, the graininess-promoting amount is an amount that results in the production of copper grains on the surface of the reduced metal, desirably weakly adhered to the surface. In contrast, an amount less than the graininess-promoting amount can result in, for example, "cementing" of copper on the surface of the reduced metal. In some examples, when the halide is a chloride, the graininess-promoting amount of the halide is such that at least substantially all of the copper in the aqueous solution comprising a copper(II) salt and a chloride is converted to CuCl4. 2 In the form of CuCl3, the amount is sufficiently high that the copper(II) salt is in the form of chloride, e.g., a concentration that is at least about three times the molar concentration of copper(II) in the aqueous solution. Again, at the beginning of the reaction, a significant portion may be CuCl3, and as the reaction proceeds, the predominant species becomes CuCl4. 2- It becomes.

[0036] The halide is introduced into the aqueous solution by any suitable means, the selection of which can be made by one of skill in the art. In some examples, the halide is introduced into the aqueous solution in the form of a suitable alkali metal salt or alkaline earth metal salt. In some examples, the alkali metal salt or alkaline earth metal salt is a sodium salt or a calcium salt, i.e., the halide is introduced into the aqueous solution in the form of a sodium salt or a calcium salt. In some examples, for example, when calcium chloride, or another chloride source, is the chloride source in the method of the present disclosure, the presence of calcium and other such "spectator ions" may cause side reactions, for example, precipitation of sulfate as gypsum (CaSO4). In such examples, one of skill in the art will understand that other agents may be added to address such side reactions. For example, a precipitating agent may be added to specifically remove calcium.

[0037] The concentration of the copper(II) salt in the aqueous solution may be any suitable concentration. For example, a suitable concentration is lower than the solubility limit of the copper(II) salt. A person skilled in the art may easily determine the solubility limit of a particular copper(II) salt under particular conditions. In some examples, the concentration of the copper(II) salt in the aqueous solution is at least about 0.5M. In some examples, the concentration of the copper(II) salt in the aqueous solution is about 0.5M to about 0.9M.

[0038] The copper(II) salt used to prepare the aqueous solution is any suitable copper(II) salt. In some examples, the aqueous solution is prepared by combining CuSO4 (copper(II) sulfate) or CuCl2 (copper(II) chloride) with a halide. In some examples, the copper(II) salt used to prepare the aqueous solution is CuSO4 (copper(II) sulfate).

[0039] The aqueous solution may be prepared by any suitable means, the selection of which may be made by one of skill in the art. In some examples, the aqueous solution is prepared by a method that includes adding a halide salt to an aqueous solution that includes a copper(II) salt.

[0040] In some examples, the aqueous solution containing copper (II) salts is obtained from a process that includes leaching copper ore. Such processes are well known in the art, and the selection of a suitable process can be made by one of ordinary skill in the art. The selection of a suitable process can depend, for example, on whether the copper ore includes copper oxide ore or copper sulfide ore. For example, copper oxide ore is readily acid leachable with a dilute solution of an acid, such as sulfuric acid. Thus, in some examples, the copper ore is a copper oxide ore and is leached with sulfuric acid. In some examples, the copper ore includes malachite, azurite, cuprite, chrysocolla, or a combination thereof. In contrast, copper sulfide ores such as chalcocite, covellite, bornite, chalcopyrite, or combinations thereof may also be useful for producing aqueous solutions containing copper(II) salts, but are not readily acid leachable without processing conditions such as, but not limited to, pre-roasting (i.e., to produce copper oxides that are readily leachable with acids such as sulfuric acid), pressure leaching, grinding, and / or bioleaching. Thus, an advantage of using copper oxide ores to produce aqueous solutions containing copper(II) salts in the methods of the present disclosure is that it may avoid the use of expensive processing steps such as pre-roasting, which are energy intensive and would produce potentially polluting compounds such as sulfur dioxide.

[0041] In some examples, the aqueous solution further comprises an acid. In some examples, the acid is selected from sulfuric acid, hydrochloric acid, and nitric acid, or a mixture thereof. In some examples, the acid is sulfuric acid. In some examples, the method may include adding an acid to the aqueous solution comprising the copper(II) salt. In some examples, for example, where the copper(II) salt is obtained from a method comprising leaching a copper ore, sulfuric acid is already present in the aqueous solution comprising the copper(II) salt as a result of the leaching conditions.

[0042] In some examples, the aqueous solution has a pH of about 1 to about 4, about 2 to about 3, about 2, or about 3. At low pH (i.e., less than 2), the aqueous solution may attack the iron to produce hydrogen gas. This may produce trace amounts of hydrogen arsenide and may form elemental arsenic in the granular copper at the surface of the reduced metal. This contamination of the copper with arsenic may adversely affect electrical conductivity. However, at high pH (i.e., greater than 3), solid Fe(III) may precipitate from the aqueous solution. The inventors believe that a pH of 2 to 3 may be optimal.

[0043] The reagents can be adjusted to establish a desired initial pH for the method. In some examples, the method can include adding an acid to an aqueous solution containing a copper(II) salt to obtain a desired pH. As noted above, the acid can be sulfuric acid.

[0044] In some examples, the method can include adding a base to the aqueous solution containing the copper(II) salt to obtain a desired pH. In some examples, the aqueous solution further includes an inorganic base. In some examples, the base is sodium hydroxide.

[0045] In some instances, Norman Toro et al. 8 As outlined in, if the halide is chloride and the chloride is combined with sulfuric acid, the chloride and subsequently Cu(l)Cl and / or CuCl2 can act as auxiliary leaching agents, resulting in the extraction of copper and precipitation of sulfur.

[0046] In some examples, contacting the reduced metal with the aqueous solution is for a period of at least about 1 hour, hi some examples, the period of time is from about 1 hour to about 3 hours or about 2 hours.

[0047] In some instances, the granular copper is removed from the surface of the reduced metal by shaking, washing, and / or brushing. In some instances, the granular copper does not require scraping or other such means to be removed from the surface of the reduced metal.

[0048] In some examples, greater than about 90% of the granular copper produced has a particle size greater than about 88 μm. In some examples, greater than about 95% of the granular copper produced has a particle size greater than about 88 μm. In some examples, greater than about 99% of the granular copper produced has a particle size greater than about 88 μm.

[0049] In some examples, greater than about 70% of the granular copper produced has a particle size greater than about 250 μm. In some examples, greater than about 75% of the granular copper produced has a particle size greater than about 250 μm. In some examples, greater than about 79% of the granular copper produced has a particle size greater than about 250 μm.

[0050] In some instances, the granular copper produced is copper crystallites.

[0051] In some instances, removal of particulate copper from the surface of the reduced metal can be assisted by stirring and / or circulating the aqueous solution. In such instances, the particulate copper may also not require scraping or other such means to be physically removed. Instead, the copper particles are removed from the surface of the reduced metal by gravity and allowed to grow on the surface of the reduced metal until they reach a sufficient size to be assisted by the flow of the solution in the vicinity of the reduced metal. Stirring and / or circulating the aqueous solution without creating turbulence also increases the reaction rate at the reduced metal.

[0052] In some examples, the temperature during contacting is from about 4° C. to about 40° C. In some examples, the temperature during contacting is ambient temperature, for example, from about 15° C. to about 25° C.

[0053] The teachings of the present disclosure can provide several environmental benefits. The methods herein rely primarily on chemical potential and their energy requirements can be very low compared to other approaches to copper production, including smelting or other hydrometallurgical methods (such as solvent extraction and electrowinning), which can also generate significant pollution. As mentioned above, processing steps such as pre-roasting, which are energy intensive and / or can generate compounds such as sulfur dioxide, can be avoided. The methods herein can also be carried out on-site at the deposit or other location of the copper source, including recovery from tailing ponds and waste heaps. On-site production of granular copper can reduce the transportation and storage requirements of the resulting product, thereby further reducing greenhouse gas emissions resulting from long-distance transportation of low-value copper concentrates as opposed to high-value, high-purity copper.

[0054] The following examples of the disclosure are intended to be illustrative but non-limiting. EXAMPLES

[0055] Example 1: Effect of NaCl concentration on copper deposition (a) A 0.8371 M CuSO4 solution was added to each of five 100 mL beakers (50 mL each). In each beaker, NaCl was dissolved as follows: solution no. 1-0 g (0 eq.), solution no. 2-4.627 g (1.9 eq.), solution no. 3-7.266 g (3.0 eq.), solution no. 4-9.755 g (4.0 eq.), solution no. 5-12.146 g (5.0 eq.). The pH of the solutions was adjusted to 2 with H2SO4. An iron rod was placed at an angle into the beaker. The reaction was checked at 30 minute intervals to determine the relative quality and quantity of precipitated grains (Figure 1). Overall, the copper grain size appeared to increase with increasing NaCl concentration over the course of 120 minutes. After that point, the grains either became too heavy and fell off the iron into the solution or began to grow indistinctly on the surface (concentration dependent). The solution without NaCl had copper plated onto the iron and was very difficult to remove. In all other solutions, the copper was easily removed by simply shaking an iron rod in the solution or tapping the side of the beaker. The yields of all solutions were similar after standing for 24 hours (#1: 81%, #2: 88%, #3: 76%, #4: 89%, #5: 91%).

[0056] (b) The reaction described in (a) was repeated using 0.8331 M CuSO4 solution (50 mL in each of three beakers) with 3.0 (7.216 g), 4.0 (9.693 g), and 5.0 (12.187 g) equivalents of NaCl added. No pH adjustment was made for this reaction. The reaction was stopped after 2 hours. Overall, the most copper particles precipitated from solution #3 (5 equivalents). The yields were similar, but solution #1 (3 equivalents) had the highest yield at 65% (#2: 53%, #3: 58%).

[0057] (c) The reaction described in (b) was repeated with 50 mL of 0.8388 M CuSO4 solution in each of three beakers. To the first solution (0 equiv., no. 1), no NaCl was added. To the other two solutions, 7.326 g (3.0 equiv., no. 2) and 12.208 g (5.0 equiv., no. 3) of NaCl were dissolved. The pH of the solutions was adjusted to 2 with H2SO4. The reaction was stopped at the 2 hour mark (Figure 2, top image). As in the first experiment, the solution without NaCl resulted in copper plating on the iron, which was difficult to remove (Figure 2, bottom image). As a result, no yield was obtained for this reaction. The particle size from solution no. 3 (5 equiv.) was larger than that of solution no. 2 (Figure 2, top image). Both yields were similar (88% and 85%, respectively).

[0058] (d) This reaction (described in more detail in Example 2(a)) was compared to larger scale solutions with 3.5 and 4.1 equivalents of NaCl (250 mL of 0.8308 M and 0.8303 M CuSO4 solutions, respectively). The 4.1 equivalent solution appeared to have larger grains than the 3.5 equivalent solution.

[0059] In general, the surface copper grain size appeared to increase with increasing NaCl concentration. The overall yield of copper precipitate did not appear to be significantly affected by NaCl concentration. The effectiveness of the copper removal from the iron is remarkable, especially when compared to solutions with no added NaCl. Concentrations of NaCl equivalent to at least 3 equivalents resulted in the production of grains of similarly good quality.

[0060] Example 2: Determination of Copper Particle Size (a) Two reactions were run simultaneously. The first solution contained 0.8308M CuSO4 and 3.5 equivalents of NaCl. The second solution contained 0.8303M CuSO4 and 4.1 equivalents (upper balance) of NaCl. Each solution was poured into a container lined with horizontal Fe rods. The reactions were left for 2 hours to obtain the optimum particle size. Following reaction work-up, the copper was passed through a series of three sieves (860 μm, 250 μm, and 88 μm) to determine the size distribution of the particles produced. The particle size distribution for solution #1 was as follows: 59% >860 μm, 24% 250-860 μm, 16% 88-250 μm, and <1% <88 μm. The particle size distribution of solution number 2 was 47% over 860 μm, 29% between 250 and 860 μm, 21% between 88 and 250 μm, and approximately 3% below 88 μm.

[0061] (b) The reaction described in (a) was repeated using a 0.8306 M CuSO4 solution and 4.1 equivalents of NaCl. The particle size distribution was as follows: 54% >860 μm, 25% between 250-860 μm, 21% between 88-250 μm, and less than 1% less than 88 μm.

[0062] (c) The reaction described in (a) was completed using a 0.76M CuSO4 leach solution and 5 equivalents (55 g) of NaCl obtained from an exotic copper ore sample. The sample was described as being copper clay, copper albite and copper silica. However, the inventors have identified it as an exotic copper ore containing primarily chrysocolla with minor amounts of malachite. The particle size distribution was determined to be 18% >860 μm, 49% 250-860 μm, 33% 88-250 μm and less than 1% less than 88 μm.

[0063] (d) The experiments described in more detail in Examples 3(a), 3(b) and 3(c) were designed to test the effect of reaction time on grain quality, but particle size distribution was measured as well. For comparison, only data from solutions run for 120 minutes are used. Experiments were run with 50 mL of 0.8541M, 0.8310M and 0.8342M CuSO4 with 4.8, 4.9 and 4.9 equivalents of NaCl added, respectively. The copper particle size distribution was as follows: an average of 1.5% (0.6%, 2%, 2%) was greater than 860 μm, an average of 54% (54%, 58%, 49%) was between 250 and 860 μm, an average of 36% (35%, 34%, 39%) was between 88 and 250 μm, and an average of 9% (11%, 6%, 11%) was less than 88 μm.

[0064] Overall, the larger scale experiments generally produced a greater proportion of grains over 860 μm, with over 80% of the grains being larger than 250 μm (Figure 3). The exception to this was the exotic copper ore leach solution where the majority of the grains were between 250 and 860 μm (although almost 70% were still over 250 μm). Without wishing to be limited by theory, this may be due to concentration differences (see below). The small scale reaction produced the greatest amount of grains in the 250-860 μm range, but approximately 90% were between 88-860 μm. This differs from the large scale reaction, where there was a much higher percentage of large grains (over 860 μm) and fewer in the lower range (88-250 μm). The maximum grain size appeared to increase with increasing NaCl concentration, but the overall size distribution determined above does not appear to be significantly affected by changes in NaCl concentration (Figure 4). However, these reactions were not run to completion. Without wishing to be limited by theory, if the solution was left to become non-productive, the proportion of particles may change, as there is an increase in small particles after 120 minutes. Without wishing to be limited by theory, this may be due to the CuSO4 concentration, as it has been shown that the quality of the copper particles depends on the CuSO4 concentration, with smaller particles seen at lower concentrations.

[0065] Example 3: Effect of reaction time on particle size and yield (a) A solution of 0.8541 M CuSO4 and 5 equivalents NaCl was divided into four beakers (50 mL each). The reactions were worked up at 30, 60, 90, and 120 minutes, respectively. The yields of the reactions were 44%, 72%, 75%, and 92%, based on the initial CuSO4 in the solution. The efficiencies of each reaction were 78%, 90%, 96%, and 97%, based on the amount of iron consumed. The solids from each solution were then passed through the sieves described above. The particle size distribution results were as follows in Table 1 below. [Table 1]

[0066] Under these conditions, the reaction time that produced the highest percentage of grains in the larger size range was 120 minutes.

[0067] (b) The reaction described in Example 3(a) was repeated using a 0.8310M CuSO4 solution with 5 equivalents of NaCl. This time the reaction was worked up after 30, 60, 90, 120 and 150 minutes. The yields based on the CuSO4 used were 34%, 59%, 78%, 93%, and 87%, respectively. The efficiency of the reaction based on the iron consumed was 77%, 87%, 91%, 94%, and 90%, respectively. The particle size distribution results are shown in Table 2 below. [Table 2]

[0068] The results are generally consistent with those in Example 3(a).

[0069] (c) The experiment described in Example 3(a) was repeated using a 0.8342M CuSO4 solution and 5 equivalents of NaCl. As in Example 3(b), the reaction was worked up after 30, 60, 90, 120 and 150 minutes. The reaction yields were 31%, 59%, 81%, 85% and 92%, respectively. The reaction percent efficiencies were 70%, 87%, 93%, 93% and 94%, respectively. The particle size distribution results are shown in Table 3 below. [Table 3]

[0070] The results of this experiment are generally consistent with those of Examples 3(a) and 3(b), except that the yield was improved at 150 minutes over 120 minutes, but not in Example 3(b).

[0071] (d) Reactions similar to those in Example 3(a)-(c) were carried out using exotic copper ore leach solution (0.6107M) spiked with 5 equivalents of NaCl. The reactions were worked up after 90, 120 and 150 minutes. The yields were 57%, 65% and 76%, respectively. The percent efficiency of the reaction was 89%, 89% and 94%, respectively. The particle size distributions were as shown in Table 4 below. [Table 4]

[0072] The yields were significantly lower than the stock solution, but the particle size distribution did not appear to be significantly affected after 90 minutes and was comparable to the stock solution results. Yields were comparable when the reaction was extended.

[0073] (e) The reaction from Example 3(d) was repeated using a 0.6055M stock solution and 5 equivalents of NaCl. The yields were found to be 70%, 78% and 83% at 90, 120 and 150 minutes, respectively. The efficiencies were 92%, 95% and 96%, respectively. The particle size distributions were as shown in Table 5 below. [Table 5]

[0074] The results were in good agreement with the experiments in Examples 3(a)-3(c) using stock solutions.

[0075] Figure 5 shows a more detailed analysis than Figure 4 of the reaction with a 5:1 chloride to copper ratio. The plot shows the particle size distribution and reaction yield as a function of reaction time. Overall, the reaction time that gave favorable values ​​in both yield and grain quality in the stock solution was 120 minutes. The particle size distribution appeared to be fairly consistent after 90 minutes. For the leach solution, a slightly longer time of 150 minutes or even longer may be useful to achieve the same yield as seen in the stock solution. The particle size distribution in this experiment is similar to the reaction with a 4:1 chloride to copper ratio.

[0076] Example 4: Effect of CuSO4 concentration (a) Four 50 mL solutions were prepared using 4.5 equivalents of NaCl and CuSO4 concentrations of 0.1432M, 0.2772M, 0.3867M, and 0.5100M. The reaction was allowed to proceed for 120 minutes. The reaction yield increased with increasing CuSO4 concentration up to 0.3867M, after which the yield remained essentially constant (No. 1: 59%, No. 2: 67%, No. 3: 75%, No. 4: 73%). Without wishing to be limited by theory, the particle size was qualitatively highest for the 0.51M solution and decreased with decreasing CuSO4 concentration (Figure 7).

[0077] (b) The reaction of Example 4(a) was repeated using solutions of 0.1757M, 0.2748M, 0.3762M and 0.5120M CuSO4 with 5 equivalents of NaCl. The yield in this case increased with increasing [CuSO4] (No. 1: 54%, No. 2: 73%, No. 3: 75%, No. 4: 78%). Similar results were obtained in terms of particle size as in Example 4(a). Concentrations below 0.51M did not appear to give good quality particles.

[0078] (c) The experiment was repeated using 3.5 equivalents of NaCl and CuSO4 concentrations of 0.1432 M, 0.2544 M, 0.3942 M, and 0.5193 M. Solution #4 (0.5193 M CuSO4) gave the best solids, but none of the solutions produced good quality pellets. The yield increased with increasing [CuSO4] up to 0.3942 M, where it essentially leveled off (#1: 62%, #2: 76%, #3: 86%, #4: 85%).

[0079] Overall, yields generally increased with increasing CuSO4 concentration up to about 0.38 M. Below 0.51 M CuSO4, the precipitated copper appeared to be non-particulate. The concentration of NaCl used in this example did not appear to affect these results.

[0080] Example 5: Grain appearance and comparison of various halide:copper ratios Using a procedure similar to that described in Example 1(a), copper was precipitated as coarse, chunky grains at a high initial chloride to copper molar ratio (4:1), as shown in Figure 8 A. At a low initial chloride to copper molar ratio (1:1), the precipitated copper had a greater tendency to form dendrites, as shown in Figure 8B.

[0081] Consider In this method, no pre-reduction of copper(II) is required, and the reduction proceeds smoothly, with Cu(II) in solution being smoothly reduced to granular metallic copper. Without wishing to be limited by theory, the redox regime in operation is based on the following redox reaction: CuCl x n- +2e -1 <->Cu 0 +xCI -1 , where x=3 or 4, and n=1 or 2. (1)

[0082] In contrast, the redox reaction scheme proposed in WO 2009 / 007792(A1) is as follows: Cu +1 +e -1<->Cu E 0 =0.52V (2) Cu 2+ +2e -1 <->Cu E 0 =0.34V (3)

[0083] In reactions 2 and 3, Cu 1+ and Cu 2+ The concentration of is determined from equilibrium, where only a small amount of copper is present as an uncomplexed ion in a solution containing a large amount of chloride. Cu +1 +4Cl - <->CuCl4 -3 (4) Cu +2 +4CI - <->CuCl4 -2 (5)

[0084] In the method of WO 2009 / 007792(A1), the preliminary reduction is in fact a reaction with tetrachlorocuprate(II). 9 to tetrachlorocuprate(I), but no potential value for this reaction has been reported. CuCl4 -2 +e -1 <->CuCl4 -3 (6)

[0085] In the absence of literature values ​​for the various equilibria, it is difficult to predict the importance of the effect of complex formation on the progress of the reaction. However, in the examples disclosed herein, which include the use of sufficient amounts of NaCl, pre-reduction is not required. Copper precipitated smoothly and no evidence of CuCl was observed. High levels of chloride had a significant effect on the course of this reaction. Other suitable halides may have a similarly significant effect on the outcome of this reduction, both in terms of copper deposition and product purity. For example, copper bromide is expected to react similarly to copper chloride.

[0086] Although the above description provides examples of one or more devices or techniques, it will be understood that other devices or techniques are possible within the scope of the following claims.

[0087] Full citations for the literature referenced herein 1 Cited by Jack T. Gentry Bachelor of Science in Metallurgical engineering thesis, Montana School of Mines 1950 2 YLKao,KCLi,GCTu,CAHuang.Microstructura study of the effects of chloride ion on electroplating of copper in copper sulfate-sulfuric acid bath.J.Electrochem.Soc.,2005,152,C605-C611 3 David W.Hardesty,Anion effects in copper deposition.J.Electrochem.Soc.,1970,117,168-172. 4 G. Carneval, J. Babczuk de Cusminsky. The influence of the anion on copper electrocrystallization. J. Electrochem Soc., 1981, 128, 1215-1221 5 Jack W. Dini, Dexter D. Snyder. Electrodeposition (Chapter 2) in Modern Electroplating. Mordechay Schlesinger, Milan Paunavic, Section 2.4.2, p36. 6 DARychkov et al.,28th European Crystallographic Meeting,ECM 28,UK,2013 Acta Cryst.2013,A69,s664. 7Mathur et al.,J.Chern.Educ.1962,39:11,A897. 8 Norman Toro et al.,Metals 2019,9,780. 9 H.Zhou,J.Chang,A.Boika,AJBard,Anal.Chem.,2013,85,7696-7703.

Claims

1. 1. A method for producing granular copper metal, comprising contacting a reduced metal with an aqueous solution, The aqueous solution is (i) a copper(II) salt; and (ii) a halide; The method wherein said granular copper is produced on the surface of said reduced metal.

2. 2. The method of claim 1, wherein the molar ratio of said halide to said copper(II) in said aqueous solution is at least about 3:

1.

3. 3. The method of claim 1 or 2, wherein the molar ratio of the halide to the copper(II) in the aqueous solution is from about 3:1 to about 5:

1.

4. 3. The method of claim 1 or 2, wherein the reduced metal is iron.

5. 3. The method according to claim 1 or 2, wherein the halide is introduced into the aqueous solution in the form of a sodium or calcium salt.

6. 3. The method of claim 1 or 2, wherein the halide is a chloride.

7. 3. The method of claim 1 or 2, wherein the concentration of the copper (II) salt in the aqueous solution is at least about 0.5 M.

8. 3. The method of claim 1 or 2, wherein the concentration of the copper(II) salt in the aqueous solution is from about 0.5 M to about 0.9 M.

9. The aqueous solution is ４ or CuCl ２ 3. The method of claim 1 or 2, wherein the compound is prepared by combining

10. The copper (II) salt is CuSO ４ The method according to claim 1 or 2,

11. 3. The method of claim 1 or 2, wherein the contacting of the reduced metal with the aqueous solution is for at least about 1 hour.

12. 3. The method of claim 1 or 2, wherein the contacting of the reduced metal with the aqueous solution is for about 1 hour to about 3 hours.

13. The method of claim 1 or 2, wherein the aqueous solution has a pH of about 2 to about 3.

14. 3. The method of claim 1 or 2, comprising adjusting the pH of the aqueous solution by adding an acid.

15. The method of claim 1 or 2, wherein the aqueous solution comprises an acid.

16. 16. The method of claim 15, wherein the acid is selected from sulfuric acid, hydrochloric acid, nitric acid, and mixtures thereof.

17. 16. The method of claim 15, wherein the acid is sulfuric acid.

18. 3. The method of claim 1 or 2, comprising adjusting the pH of the aqueous solution by adding a base.

19. 20. The method of claim 18, wherein the base is an inorganic base.

20. 20. The method of claim 18, wherein the base is sodium hydroxide.

21. 3. The method of claim 1 or 2, wherein the aqueous solution is prepared by a process comprising adding the halide salt to an aqueous solution containing the copper(II) salt.

22. 3. The method of claim 1 or 2, wherein the aqueous solution containing the copper (II) salt is obtained from a process comprising leaching a copper ore.

23. 23. The method of claim 22, wherein the copper ore is leached with sulfuric acid.

24. 3. The method of claim 1 or 2, comprising removing the particulate copper from the surface of the reduced metal by shaking, washing, and / or brushing.

25. 3. The method of claim 1 or 2, comprising removing the particulate copper from the surface of the reduced metal without scabbing.

26. 3. The method of claim 1 or 2, comprising stirring and / or circulating the aqueous solution.

27. 3. The method of claim 1 or 2, wherein greater than about 95% of the granular copper produced has a particle size greater than about 88 μm.

28. 3. The method of claim 1 or 2, wherein greater than about 75% of the granular copper produced has a particle size greater than about 250 μm.

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