Leaching of precious metals and chalcophilic metals

Abstract

A process for recovering one or more target metals from a material containing a noble metal and / or a chalcophile metal, the target metal being selected from noble metals and chalcophile metals as defined herein, the process comprising: (i) leaching the metal-containing material with an aqueous solution to produce a leachate containing the target metal, the aqueous solution comprising: a “metal releaser” containing an amino acid; and a “metal retainer” comprising one or more of ammonia, ammonium salts, carboxylic acids, carboxylates, dicarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, hydroxycarboxylates, ethylenediaminetetraacetic acid (EDTA), and EDTA salts; and (ii) extracting the metal from the leachate.

Description

Technical Field

[0001] A process is disclosed for recovering one or more target metals from materials containing precious metals and / or chalcophile metals, the target metals being selected from precious metals and chalcophile metals. This process can be used to recover metals from ores, concentrates, or tailings, or from other metal-containing materials, including jewelry, electronic waste, and other waste materials. This process can be particularly used for leaching low-grade ores, concentrates, or tailings in in-situ, heap leaching, or vat leaching methods. It can also be used for leaching process intermediates and / or secondary materials or waste. Waste can include any solid material generated through human activities, manufacturing, or processing, such as, but not limited to, municipal waste, electronic and electrical waste (“e-waste”), mineral tailings, dust, leaching residues, slag, electrolytic deposition and electrolytic refining slime and sludge, any other metal-containing slime and sludge, and scum. Metal-containing materials can also include contaminated soil.

[0002] As used herein, the term "precious metal" refers to gold (Au), silver (Ag), and the platinum group metals: ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). However, among these precious metals, this process is particularly suitable for the recovery of one or more of gold, silver, palladium, and platinum, and therefore the discussion will focus on these precious metals.

[0003] As used herein, the term "chalcophile metal" refers to copper (Cu), nickel (Ni), cobalt (Co), zinc (Zn), lead (Pb), cadmium (Cd), thallium (Tl), indium (In), mercury (Hg), gallium (Ga), tin (Sn), and bismuth (Bi). However, among these chalcophile metals, this process is particularly suitable for the recovery of Ni, Co, Zn, and Cu, and more specifically for Ni, Co, and Cu; therefore, the discussion will focus on these chalcophile metals. This process is more selective for these metals compared to other metals such as iron, magnesium, manganese, silicon, and aluminum. This process is even more particularly suitable for the recovery of nickel and cobalt, such as from nickel and cobalt ores, by increasing the leaching properties and stability of these metals in the leaching solution.

[0004] As used herein, the term "lixiviant" refers to a solvent that ensures phase transfer (i.e., from a solid state to a liquid solution state of a substance), thereby forming a complex with the target metal, which would otherwise be insoluble in the liquid state if not in the presence of the lixiviant. Background Technology

[0005] The recovery of sulfide-loving and / or precious metals is typically carried out via hydrometallurgical processes. Different types of reagents have previously been used to leach copper and / or precious metals, often depending on the pH regime of the ore environment. Many of these reagents have undesirable properties such as toxicity, cost, lack of selectivity, and low extraction rates, as detailed below.

[0006] Some ores are associated with alkaline environments. Traditionally, cyanide can be used as a possible leaching agent in alkaline environments. However, cyanide is highly toxic.

[0007] Compared to the alkaline-associated ores mentioned above, many ores are associated with acidic conditions in their immediate environment or with prior acidic pre-oxidation processes. In these environments, acidic leaching processes are more commonly used. However, these acidic processes can also have accompanying problems. Many leaching agents are used in acidic environments (such as thiocyanates, chloride-chloride systems, hypochlorites, bromides, and acidic thioureas in the presence of oxidants). For example, acidic thioureas are an alternative leaching system to alkaline cyanides used to extract gold from some gold deposits. However, the use of these leaching agents is problematic, at least due to their toxicity and cost.

[0008] The inventors have previously proposed using amino acids as potential leaching agents for leaching target metals, such as thiophilic metals and / or noble metals. Amino acids are attractive alternatives to other more conventional leaching agents because they are environmentally safe and relatively inexpensive. However, it has been found that target metals can exhibit limited solubility when amino acids are used alone. Moreover, these leaching agents may require the presence of other types of substances (such as catalysts) in the solution, which could introduce contaminants in downstream processing. Furthermore, the amino acid-based leaching systems previously developed by the inventors are generally only effective under limited physicochemical conditions, particularly within a limited range of solution pH.

[0009] It is desirable to provide an amino acid-based leaching process and leaching solution that improves the solubility of chalcophilic metals and / or noble metals. It is also desirable to provide an amino acid-based leaching process and leaching solution that is effective under a wider range of process conditions. Furthermore, it is desirable to provide a leaching process and leaching solution that is effective under a wider range of solution pH conditions. Finally, it is desirable to provide a leaching process and leaching solution that limits the addition of new reagents, thereby simplifying the chemical composition of the system.

[0010] The foregoing references to the background art do not constitute an admission that the art constitutes part of the common knowledge of those skilled in the art. Nor are the references mentioned above intended to limit the application of the devices and methods disclosed herein. Summary of the Invention

[0011] The inventors have surprisingly discovered that using a leaching solution containing one or more metal release agents comprising amino acids (or their derivatives, such as salts) and one or more metal retention agents synergistically enhances the dissolution rate and / or extent of thiophilic metals and / or noble metals in solution over a wide pH range.

[0012] As used herein, the term "metal liberator" refers to a type of leaching agent used to release a target metal from a leached material. In this application, the metal liberator is a leaching agent that typically contains amino acids or derivatives thereof, which ensures phase transfer (i.e., from a solid state to a liquid solution state of the substance), thereby allowing the ions of the target metal to form an aqueous complex with the leaching agent.

[0013] As used herein, the term "metal retainer" refers to an aqueous type that complexes with the released ions of the target metal and extends the solubility limit of the released ions.

[0014] It has been found that amino acids themselves cannot retain significant concentrations of the target metal in solution upon release. This property is not necessarily a problem when the material being treated contains low concentrations of the target metal, such as in low-grade ores. Precious metals (such as gold) are typically found in low-grade ores, in the range of parts per million (g / t). In contrast, sulfophilic metals (such as nickel and cobalt) are typically found in ores in percentage (or at least 1%) fractions, a difference of four or five orders of magnitude. In the latter case, due to the presence of more target metal, a "metal retainer" is needed to hold the sulfophilic metal in solution, while amino acids act as "metal releasers." For example, glycine typically cannot retain more than about 5 g / L of copper and more than about 8 g / L of nickel in solution. This can be problematic when treating materials with high levels of the target metal, such as e-waste. For example, e-waste may have a high copper content, which translates to a correspondingly high copper concentration in solution, such as about 30 to 50 g / L.

[0015] The inventors have discovered that including one or more metal retainers in the leaching solution can significantly increase the amount of the target metal retained in the solution. However, when the target metal is a noble metal, the need for metal retainers may be less significant.

[0016] The inventors have also discovered that including one or more metal retainers in the leaching solution can significantly expand the physicochemical conditions for the solubility of the target metal in the solution, particularly the pH range.

[0017] In a first aspect, a process is disclosed for recovering one or more target metals from a material containing a noble metal and / or a chalcophile metal, the target metal being selected from noble metals and chalcophile metals as defined herein, the process comprising:

[0018] (i) Leaching a metal-containing material with an aqueous solution to produce a leachate containing the target metal, the aqueous solution containing:

[0019] "Metal releasers" containing amino acids, and

[0020] "Metal retainers" include one or more of the following: ammonia, ammonium salts, carboxylic acids, carboxylic acids, dicarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, hydroxycarboxylic acids, ethylenediaminetetraacetic acid (EDTA), and EDTA salts; and

[0021] (ii) Extracting metals from the leachate.

[0022] In the second aspect, the target metal recovered through the above-described process is disclosed.

[0023] As used herein, the term "amino acid" refers to an organic compound containing both a carboxyl (-COOH) and an amino (-NH2) functional group. For ease of discussion, the term "amino acid" as used herein is intended to include derivatives of amino acids. Derivatives may include amino acid salts, such as alkali metal salts, like sodium glycinate or potassium glycinate, or alkaline earth metal salts, such as calcium or ammonium salts. Derivatives may alternatively or additionally include peptides.

[0024] In many cases, amino acids contain a –CHR or CH2 group. In most cases, the amino (-NH2) group and the carboxyl (-COOH) group are attached to the same -CHR or -CH2 linker, and are called primary α-amino acids. The “R” group in the -CHR linker can take any organic structure, from aliphatic hydrocarbon groups to complex organic structures, including aromatic groups, heterocyclic groups, and polynuclear groups, or various other organic groups. In its simplest form, the R group is simply hydrogen, in which case the molecule is reduced to the simplest primary α-amino acid, called glycine. Amino acids can include one or more of glycine, histidine, valine, alanine, phenylalanine, cysteine, aspartic acid, glutamic acid, lysine, methionine, serine, threonine, and tyrosine.

[0025] In embodiments, the amino acid may be glycine (Gly) (chemically defined by the formula NH₂CH₂CO₂H). Glycine is a simple amino acid, easy and inexpensive to produce on an industrial scale, and has the highest potential for industrial use. The following discussion will focus primarily on the use of glycine and its salts as amino acids; however, it should be understood that the invention extends to other amino acids, particularly glutamic acid. “Glycine” can refer to the amino acid commonly known by that name, or any of its salts (such as sodium glycinate or potassium glycinate). Other common names for glycine include aminoacetic acid or aminoethanoic acid. In embodiments, the amino acid is provided in an aqueous solution of an alkaline or alkaline earth metal hydroxide (such as sodium hydroxide, potassium hydroxide, or calcium hydroxide).

[0026] Glycine and / or its salts are preferred amino acids because they:

[0027] • Large-scale production and mass supply;

[0028] • Low production cost;

[0029] • Easy to transport;

[0030] • Chemical and thermal stability;

[0031] It has high solubility in water;

[0032] • Low price; and

[0033] • Low molecular weight.

[0034] While other amino acids can be used to replace glycine (or other amino acids besides glycine), they are generally more expensive, and any performance advantage is usually not justified by the additional cost. Glycine has very high solubility in water, is thermally stable, and is stable in the presence of mild oxidizing agents such as dilute hydrogen peroxide, manganese dioxide, and oxygen. It is a non-toxic, environmentally safe, and stable reagent. It is also relatively inexpensive and can be purchased in bulk. From an economic perspective, the ability to easily regenerate, recover, and reuse glycine in acidic solutions is one of its most important properties.

[0035] In another embodiment, the amino acid is glutamic acid. Glutamic acid, like glycine, is also cheaper and available in bulk. However, its molecular weight is significantly higher than that of glycine (147.13 g / mol, compared to 75.05 g / mol), meaning it may be more difficult to process than glycine.

[0036] The concentration of amino acids in the solution can vary between 0.01 g / L and 250 g / L. In some embodiments, the concentration can be as high as 50 g / L. The minimum concentration can be 0.01 g / L, although it is typically at least 0.1 g / L. In some embodiments, the concentration of amino acids is at least 0.3 g / L. The concentration of amino acids is preferably at least 1 g / L. In embodiments, the concentration of amino acids is at least 5 g / L, and can be at least 7 g / L. In another embodiment, the concentration of amino acids is at least 10 g / L.

[0037] The solution should preferably be substantially free of one or more potentially harmful substances that are intentionally added, such as thiosulfates, thiocyanates, thioureas, chlorine, bromine, substances containing hydrofluoric acid, transition metal salts, and strong oxidizing agents such as H₂O₂. In most cases, this means that the solution is substantially free of these harmful substances. However, there is a possibility that these harmful substances may be generated in situ in the solution due to unintended reactions.

[0038] Metal retention agents are preferably selected from the group consisting of:

[0039] Ammonia, ammonium salts, carboxylic acids, carboxylic acids, dicarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids, hydroxycarboxylic acids, ethylenediaminetetraacetic acid (EDTA) and EDTA salts.

[0040] Examples of carboxylates and dicarboxylate salts include salts of acetic acid, salts of oxalic acid (e.g., ferric oxalate), salts of malonic acid, and salts of formic acid.

[0041] Examples of hydroxycarboxylic acids and their salts include salts of gluconic acid, citric acid, fumaric acid, tartaric acid, succinic acid, lactic acid, and malic acid.

[0042] In one embodiment, the metal retainer comprises ammonia or an ammonium salt. The ammonium salt may comprise ammonium sulfate. Alternatively, the ammonium salt may be an ammonium halide, such as ammonium chloride, ammonium bromide, or ammonium iodide. In another embodiment, the ammonium salt may be ammonium carbonate. In another embodiment, the ammonium salt may be ammonium nitrate. In another embodiment, the ammonium salt may be ammonium oxalate. In another embodiment, the ammonium salt may be ammonium acetate.

[0043] In this process, ammonia or ammonium ions are used to form complexes with the target metal to enhance its solubility, rather than being simply added to adjust the solution pH. Therefore, ammonia or ammonium ions must be present in the solution at a sufficient concentration to perform the function of a metal retainer.

[0044] The concentration of the metal retainer will depend on the type and amount of the target metal to be leached from the material. In one embodiment, the concentration of the metal retainer is at least 0.001 M. In another embodiment, the concentration of the metal retainer is at least 0.005 M. In another embodiment, the concentration of the metal retainer is at least 0.01 M. In another embodiment, the concentration of the metal retainer is at least 0.05 M. In another embodiment, the concentration of the metal retainer is at least 0.1 M. In another embodiment, the concentration of the metal retainer is at least 0.2 M. In another embodiment, the concentration of the metal retainer is at least 0.5 M. In another embodiment, the concentration of the metal retainer is at least 0.7 M. In another embodiment, the concentration of the metal retainer is at least 0.75 M. In another embodiment, the concentration of the metal retainer is at least 0.8 M. In another embodiment, the concentration of the metal retainer is at least 0.9 M. In another embodiment, the concentration of the metal retainer is at least 1.0 M. In another embodiment, the concentration of the metal retainer is at least 1.2 M. In another embodiment, the concentration of the metal retainer is at least 1.5 M. In another embodiment, the concentration of the metal retainer is at least 1.7 M. In yet another embodiment, the concentration of the metal retainer is at least 2 M.

[0045] The concentration of the metal retainer can be a maximum of 2.5 M. In one embodiment, the concentration of the metal retainer can be a maximum of 2 M. In another embodiment, the concentration of the metal retainer is a maximum of 1.5 M. In another embodiment, the concentration of the metal retainer is a maximum of 1.25 M. In another embodiment, the concentration of the metal retainer is a maximum of 1.2 M. In another embodiment, the concentration of the metal retainer is a maximum of 1 M. In another embodiment, the concentration of the metal retainer is a maximum of 0.75 M.

[0046] When the metal retainer contains ammonia or ammonium ions, the equivalent ammonia concentration for leaching noble metals can be at least 50 ppm (3 mmol / L). In an embodiment, the minimum ammonia concentration for leaching noble metals can be 100 ppm (6 mmol / L). When the metal retainer contains ammonia or ammonium ions, the equivalent ammonia concentration for leaching chalcophilic metals can range from a minimum of 1,000 ppm (60 mmol / L). In both cases, the maximum ammonia concentration can be 85,000 ppm (5 mol / L).

[0047] The mass of the metal retainer in the solution can be at least half the mass of the metal releaser in the solution. The mass ratio of the metal releaser to the metal retainer can be 10:1 or lower, such as 7:1 or lower. In one embodiment, the mass ratio of the metal releaser to the metal retainer is 5:1 or lower, such as 3:1 or lower. In another embodiment, the mass ratio of the metal releaser to the metal retainer is 2:1 or lower, such as 2:1.5 or lower. In another embodiment, the mass ratio of the metal releaser to the metal retainer can be 2:1.7 or lower. In another embodiment, the mass ratio of the metal releaser to the metal retainer can be 2:1.8 or lower. In another embodiment, the mass ratio of the metal releaser to the metal retainer can be 1:1 or lower. In another embodiment, the mass ratio of the metal releaser to the metal retainer can be 1:1.5 or lower.

[0048] In the leachate, the molar ratio between the target metal ions and the metal retainer in the solution can be at least 1:2. The molar ratio can be as high as 1:8. In one embodiment, the molar ratio can be at least 1:2.5. In another embodiment, the molar ratio can be at least 1:3. In yet another embodiment, the molar ratio can be at least 1:4. In still another embodiment, the molar ratio can be at least 1:5.

[0049] The leaching process can be carried out in the presence of an oxidizing agent. Preferably, the oxidizing agent is not a strong oxidizing agent such as H₂O₂. Examples of simple oxidizing agents that can be used include air (gaseous and dissolved) and oxygen (gaseous and dissolved). Other oxidizing agents may include halogens, iron or copper ions, ozone, nitrates, chlorites, hypochlorites, persulfates, and iodine may also be used.

[0050] The leaching process can be carried out with an additional small amount of catalyst included in the leaching solution. The catalyst may be selected from iodine and / or iodides, bromine and / or bromides, thiourea and cyanides, or mixtures thereof.

[0051] The leaching solution can be acidic, neutral, or alkaline. In one embodiment, the solution pH is at least 3. In another embodiment, the solution pH is at least 3.5. In another embodiment, the solution pH is at least 4. In another embodiment, the solution pH is less than 13. In another embodiment, the solution pH is less than 12. In another embodiment, the solution pH is less than 11. In another embodiment, the solution pH is not higher than 10.5. In another embodiment, the solution pH is not higher than 10.

[0052] In one embodiment, the leaching step (i) is carried out under acidic conditions. The process can be carried out using a moderately acidic solution with a pH range of 0 to 7. In another embodiment, the pH range is 1 to 6. In yet another embodiment, the pH is 3 to 6. In yet another embodiment, the pH is 4 to 6.

[0053] In another embodiment, the leaching step (i) is carried out under alkaline conditions. This process can be performed using a leaching agent with a solution pH less than 13. In another embodiment, the solution pH is at least 12. In another embodiment, the solution pH is at least 11. In another embodiment, the solution pH is not higher than 10.5. In another embodiment, the solution pH is not higher than 10.

[0054] If necessary, a pH adjuster can be added to the solution to adjust the pH. To lower the pH, the pH adjuster can be any acid (organic or inorganic), such as sulfuric acid. Acids can also form due to the in-situ oxidation of sulfide minerals in the presence of oxygen (or other oxidizing agents) and water, or from naturally acidic water and water derived from drainage from acidic mines or acidic rocks. If it is desired to increase the pH, an alkaline substance, such as NaOH, can be added to the solution.

[0055] Materials containing precious metals and / or chalcophile metals may comprise ores or concentrates (collectively referred to herein as “ores” for ease of discussion). The material may alternatively comprise waste, including mining waste such as tailings, industrial waste such as fly ash, or electronic waste (“e-waste”), such as computers, keyboards, televisions, mobile phones, etc. The material may be electrical waste and municipal waste. The material may be slag, slag, dust, and matte derived from pyrometallurgical processing operations. The material may be intermediates from mining or metallurgical processes, such as sediments, residues, or metal-containing sludge or slime (e.g., derived from electrolytic deposition and electrolytic refining). The material may be metal-contaminated soil. While the following discussion will focus on the use of recycling processes for treating ores, it should be understood that it is not limited thereto and applies to all solid materials containing precious metals and / or chalcophile metals.

[0056] Materials containing precious metals and / or chalcophile metals most often appear in ores as sulfide minerals, but oxides, arsenides, thioarsenides, native metals, tellurides, sulfates, carbonates, chlorides, silicates, hydroxylated salts, and hydroxide minerals may also be common.

[0057] In this implementation plan, the process recovers non-precious metals. The process is suitable for the recovery of nickel, cobalt, or copper. It is particularly suitable for the recovery of nickel and cobalt, such as from nickel and cobalt ores.

[0058] This process can be applied to recover metals, such as copper, from electronic waste.

[0059] In one embodiment, leaching can occur “in situ” or “in place” (i.e., in the underground rock mass using a well site). In another embodiment, leaching can include dump leaching, such as by leaching blasted but uncrushed particles typically smaller than 200 mm. In another embodiment, leaching can include heap leaching, such as by leaching coarsely crushed particles typically smaller than 25 mm. In another embodiment, leaching can include barrel leaching, such as by leaching finely crushed particles typically smaller than 4 mm. In another embodiment, leaching can include stirred tank leaching, such as by leaching abrasive materials whose particles are typically smaller than about 0.1 mm / 100 micrometers. In another embodiment, leaching can be carried out in a pressure leaching autoclave and can include leaching particles typically smaller than 100 micrometers.

[0060] When the metal retainer contains ammonia or ammonium ions, given that ammonia is volatile and potentially toxic, the leaching process preferably does not include in-situ leaching, heap leaching, or heap leaching.

[0061] The recovery process can be carried out within a certain temperature range, wherein the water remains liquid under a given system pressure. In one embodiment, the process is carried out at ambient temperature or a moderately elevated temperature. The process can be carried out at temperatures ranging from -10°C to 200°C, such as from 0°C to 100°C. In cases of elevated temperatures, the temperature can be at least 30°C, such as at least 40°C. The maximum temperature can be the boiling point of the solution. In one embodiment, the process can be carried out at temperatures up to 75°C. In one embodiment, the process is carried out at temperatures between 20°C and 65°C.

[0062] The recovery process can be conveniently carried out at atmospheric pressure (from average altitude to low atmospheric pressure approximately 6000 meters above average altitude). However, in some embodiments, the process can be carried out at high pressure or below atmospheric pressure. The pressure range can be from 0.01 bar to 1000 bar. However, it is typically from 0.5 bar to 1.5 bar.

[0063] The leaching step can be carried out in the presence of a variable amount of dissolved oxygen, which can be provided, for example, via aeration or oxidation. The dissolved oxygen (DO) concentration in the solution can vary between 0.1 and 100 mg / L (e.g., 2 to 30 mg / L), depending on the oxygen demand (OD) of the CPM in the solution and the pressure of the leaching process.

[0064] This process can use various types of water, namely tap water, river water, seawater, as well as brine and high-salinity brine containing a large amount of dissolved salts, including sodium, magnesium, calcium, chloride, sulfate and carbonate ions.

[0065] Materials containing noble metals and / or chalcophilic metals react with a leaching agent to leach the target metal into the leachate. Not wishing to be limited by theory, it is believed that metal-releasing agents (typically amino acids) dissolve the target metal from the material. The presence of metal-retaining agents further enhances the release of the metal from the material and also results in a greater degree of complexation with the target metal than with amino acids alone.

[0066] The ratio of solid material containing precious metals and / or chalcophile metals to the leaching agent can vary. For example, in in-situ leaching, the solid-liquid ratio may be high, such as up to 100:1. In stirred tank leaching, the solid-liquid ratio may be much lower, such as approximately 50:50 or 1:1 by weight (i.e., 50 kg solids to 50 kg aqueous solution). In the case of leaching concentrates, this ratio can be even lower, such as approximately 10 kg solids per 90 kg aqueous solution (i.e., 1:9). Apart from the presence of some metal / mineral-containing solids, there is no minimum amount of solids relative to the liquid phase (containing the leaching agent).

[0067] Therefore, the leaching system used in the disclosed process contains at least the following components:

[0068] • Solid materials containing the target noble metal and / or chalcophilic metal.

[0069] • Ionized solvents, such as water.

[0070] • Optionally, a pH adjuster such as a strong inorganic acid (e.g., sulfuric acid) or a base (e.g., NaOH) can be used.

[0071] Metal release agents, which typically contain amino acids.

[0072] Metal retainers comprise one or more of the following: ammonia, ammonium salts, carboxylic acids, carboxylates, dicarboxylic acids, dicarboxylate salts, hydroxycarboxylic acids, hydroxycarboxylates, ethylenediaminetetraacetic acid (EDTA), and EDTA salts. Metal retainers can be prepared in advance before being added to the solution or formed in situ in the solution.

[0073] Once leached, the metal can be recovered from the aqueous solution using one of a series of extraction steps.

[0074] Possible recovery steps may include chemical recovery, such as by recovering solid metals (e.g., by electrolytic deposition of metal, hydrogen precipitation of metal powder, or as metal sulfide precipitates). Precious metals may also be recovered via zinc cementation (e.g., the Merrill Crowe process commonly used to recover precious metals from solution). Alternative recovery steps may include the use of ion exchange (IX) resins, solvent extraction (SX) organic solvents, activated carbon, molecular recognition (MR) resins, or coated adsorbents (CA), which may include polyethyleneimine (PEI)-coated diatomaceous earth, ferrofluids, and CPM-selective organic adsorbents grafted onto a solid matrix. It is preferable not to recover metals by adding carbonizing agents (such as CO2 or carbonates) that precipitate the metal as metal carbonates.

[0075] When the target metal is a chalcophile metal, the recovery step may include solvent extraction (SX). The recovery step may further include an electrolytic deposition (EW) step. In an embodiment, the recovery step includes solvent extraction and electrolytic deposition (SX / EW). In SX / EW, metal ions are selectively extracted from an aqueous leaching solution into a solvent. The metal ions are then stripped from the solvent and deposited onto an electrode using an electrolytic process.

[0076] When the target metal is a precious metal, the recovery step may include adsorbing the precious metal onto activated carbon. The activated carbon and the adsorbed precious metal are then separated and processed to recover the adsorbed metal. Attached Figure Description

[0077] Although any other form may fall within the scope of the apparatus and methods set forth in the invention description, specific embodiments will now be described by way of example only with reference to the accompanying drawings, in which:

[0078] Figure 1 This is a graph showing the nickel recovery rate (%) versus time (hours) in a solution with a pH of 10 and a solid content of 40% at room temperature, containing the following as leaching agents:

[0079] GlyAmm: 46.3 g / L glycine, 63 g / L (0.5 M ammonium sulfate) (rhombic);

[0080] Glycine (triangle): 46.3 g / L

[0081] Amm: 63 g / L (0.5 M ammonium sulfate) (square).

[0082] Figure 2This is a graph showing the cobalt recovery (%) versus time (hours) in a solution with a pH of 10 and a solid content of 40% at room temperature, containing the following as leaching agents:

[0083] GlyAmm: 46.3 g / L glycine, 63 g / L (0.5 M ammonium sulfate) (rhombic);

[0084] Glycine (triangle): 46.3 g / L

[0085] Amm: 63 g / L (0.5 M ammonium sulfate) (square).

[0086] Figure 3 This is a graph showing the percentage of copper extraction from chalcopyrite using amino acid solutions relative to time (hours) in the absence or presence of different additives (0.3 M). The amino acid solutions are glycine (cross), glutamic acid (open circle), glycine and ammonia (closed circle), glutamic acid and ammonia (square), glycine and acetate (rhombus), and glycine and citrate (triangle).

[0087] Figure 4 This is a graph showing the percentage of copper extraction with glycine solution relative to time (hours) in the absence of (square) or presence of (circle) ammonia. Detailed Implementation

[0088] Example

[0089] The following describes non-limiting embodiments of a process for recovering one or more elements selected from precious metals and chalcophile metals. The following abbreviations are used for the leaching agent: "GlyAmm" for the system glycine-ammonium, where "Gly" refers to glycine and "Amm" refers to ammonium. The pressure and temperature for all embodiments are 1 atmosphere and room temperature (20°C), respectively.

[0090] Example 1.

[0091] At room temperature, the hydrocyclone overflow of nickel ore containing 0.67% Ni was leached with a solution at pH 10, 40% solids content, containing 46.3 g / L glycine and 63 g / L (0.5 M ammonium sulfate) (GlyAmm). Under the same conditions, the nickel recovery rate versus time was compared with the nickel recovery rate versus time using two other leaching agents [containing 46.3 g / L glycine (Gly) and 63 g / L (0.5 M ammonium sulfate) (Amm), respectively]. The results are presented as follows: Figure 1It can be seen that the nickel recovery rate when leaching with GlyAmm solution (rhombus shape) is significantly higher than that when leaching with Gly solution (triangular shape) or Amm solution (square shape). Furthermore, the nickel recovery rate when leaching with GlyAmm solution is greater than the sum of the recovery rates when using Gly and Amm solutions, indicating a synergistic effect of GlyAmm solution.

[0092] Example 2.

[0093] At room temperature, the overflow of a hydrocyclone containing 0.15% Co was leached with a solution at pH 10, 40% solids content, containing 46.3 g / L glycine and 63 g / L (0.5 M ammonium sulfate) (GlyAmm). Under the same conditions, the cobalt recovery as a function of time was compared with the cobalt recovery as a function of time using two other leaching agents [containing 46.3 g / L glycine (Gly) and 63 g / L (0.5 M ammonium sulfate) (Amm), respectively]. The results are presented as follows: Figure 2 Similar to nickel recovery in Example 1, it can be seen that the cobalt recovery rate when leached with GlyAmm solution (rhombus) is significantly higher than that when leached with Gly solution (triangle) or Amm solution (square). Furthermore, the cobalt recovery rate when leached with GlyAmm solution is greater than the sum of the recovery rates using Gly and Amm solutions, indicating a synergistic effect of GlyAmm solution.

[0094] Example 3.

[0095] Crushed chalcopyrite concentrate was leached using two solutions: a Gly solution containing 0.5 M glycine in a bottle roller and a GlyAmm solution containing 0.5 M glycine and 1 M ammonia. Leaching was carried out at room temperature, pH 10, and a bottle roller speed of 100 rpm in both cases. The results are presented in Table 1. It can be seen that the recovery rates of precious metals gold and silver were significantly higher in the GlyAmm system (up to 5 times the gold recovery). Copper recovery was also much higher with GlyAmm leaching: 85%, compared to only 50% with glycine alone.

[0096] Table 1

[0097]

[0098] BDL = Below detection limit

[0099] Example 4.

[0100] Chalcopyrite containing 22.1% copper was leached with various amino acid-based solutions under the following conditions: 10 g / L amino acids, 1% solids content, particle size: 100%-45 μm, pH 10.5, room temperature. The results are as follows: Figure 3As shown, copper extraction (%) is plotted against leaching time (hours). The amino acid solutions contain glycine or glutamic acid alone, or glycine or glutamic acid simultaneously with 0.3 M of different corresponding additives. The amino acid solutions are glycine (cross-shaped), glutamic acid (open circle), glycine and ammonia (closed circle), glutamic acid and ammonia (square), glycine and acetate (rhombus), and glycine and citrate (triangle).

[0101] The results showed that leaching with glycine or glutamic acid was enhanced in the presence of a metal retainer (such as ammonia, acetate, or citrate ions). Generally, for any given leaching time, glycine-based solutions provided higher recoveries than glutamic acid-based solutions. Figure 3 Of the three metal retainers shown, ammonia provided the greatest improvement in copper solubility, and the combination of glycine and ammonia provided the highest copper recovery (90% recovery after 48 hours of leaching).

[0102] Example 5.

[0103] A mixed hydroxide precipitate containing 30% Ni and 2.5% Co (MHP - an intermediate product generated during the hydrometallurgical processing of laterite nickel ore) was leached using corresponding glycine solutions with and without ammonia. In each case, the solution conditions were: 40 g / L glycine, 1% solids content, pH 10, carried out at room temperature, and a leaching time of 4 hours. The GlyAmm solution also contained 0.3 M ammonia.

[0104] The results are listed in Table 2 below:

[0105] Table 2

[0106] glycine glycine-ammonia Ni% 98.8 100 Co% 75.3 98.6

[0107] While a slightly higher nickel recovery was achieved when ammonia was present in the leaching solution, the cobalt recovery was significantly higher (>20%) when using GlyAmm solution.

[0108] Example 6.

[0109] A mixture of copper and nickel (sulfate) salts was dissolved at room temperature in an alkaline solution (pH 10.5) containing amino acids, with and without additional metal retaining agents. Each solution contained 1 M amino acid and, where appropriate, 1 M metal retaining agent. The results are listed in Table 3 below.

[0110] Table 3

[0111]

[0112] The results showed that under the specific sample conditions, relatively low copper and nickel recoveries were observed when the sample was treated with a solution containing either glutamic acid or glycine itself. Recovery significantly improved when metal retainers were added to the amino acid solutions individually. In most cases, the nickel concentration was higher than the copper concentration in each solution. Similar recoveries were observed when ammonia or citrate ions were used as metal retainers. Slightly higher recoveries were observed when gluconic acid was used as a metal retainer. The highest recoveries were obtained using a combination of glycine and EDTA.

[0113] Example 7

[0114] A sample of copper oxide ore containing 66% malachite, 16.7% quartz, and 3.35% hematite was leached in 20 g / L glycine at pH 10.5 and room temperature, in the absence and presence of 0.3 M ammonia. The results are as follows: Figure 4 As shown, this is a graph of copper recovery rate (%) versus leaching time (hours). Squares represent copper recovery rates in the absence of ammonia, and circles represent copper recovery rates in the presence of ammonia. In the presence of ammonia, the copper recovery rate reaches 100% after 6 hours. However, in the absence of ammonia, the maximum recovery rate is only about 90%.

[0115] Example 8

[0116] Samples containing metal oxide alkaline battery waste (containing 43% Zn, 51% Mn, and 0.5% Cu) were leached for 24 hours at pH 10.5 and room temperature, in the absence of and presence of 0.4 M ammonia, respectively, in a solution containing 20 g / L glycine. Samples were also leached in a solution containing 20 g / L glutamate and 0.4 M ammonia. The results are shown in Table 4.

[0117] Table 4

[0118] glycine glycine-ammonia Glutamic acid-ammonia Zn% 32 85.2 81.3 Cu% 70.2 85 80.7 Mn% 0.1 2.1 0.5

[0119] The results showed excellent selectivity for zinc and copper relative to manganese. Furthermore, the recovery rates of each of the zinc and copper were significantly improved when the waste was leached with a combination of glycine and ammonia compared to leaching with glycine alone. Moreover, leaching with a combination of glycine and ammonia further improved the recovery rates of both metals compared to leaching with glutamic acid and ammonia.

[0120] Example 9

[0121] At room temperature, a material comprising nickel sulfide as pyrite and containing 17% Ni, 0.45% Co, and 0.15% Zn is leached with a glycine-based solution at pH 10 containing 20 g / L of amino acid (glycine). In the first leaching solution, a mixture of glycine (20 g / L) and ammonia (10 g / L NH3) is used to leach the pyrite. If necessary, the pH is readjusted to pH 10 during the leaching process by further adding ammonia. In the second leaching solution, a solution containing only glycine is used, and the pH is readjusted with sodium hydroxide (NaOH) if necessary.

[0122] The results of leaching with the first and second solutions are presented in Tables 5 and 6, respectively.

[0123] Table 5

[0124] Ni Co Zn S Fe Mg Metals contained (g) 4.46 0.122 0.041 2.729 2.172 3.90 Metal (g) leached from the residue 0.746 0.04 0.009 1.0943 1.4823 3.24 Metal leached from the solution (g) 3.65 0.092 0.028 1.9520 0.457 0.27 Total leachate (g) 4.40 0.128 0.037 3.0463 1.9393 3.51 Recovery rate, % 81.9 75.5 69.1 71.53 21.0 6.86 Recovery rate, % solution / residue 83.0 71.95 75.10 64.1 23.6 7.6

[0125] Table 6

[0126] Ni Co Zn S Fe Mg Metals contained (g) 4.458 0.122 0.041 2.729 2.172 3.902 Metals leached from the residue (g) 0.860 0.038 0.022 0.589 1.503 3.296 Metal (g) leached from the solution 3.007 0.070 0.011 1.877 0.230 0.079 Total leachate (g) 3.867 0.109 0.033 2.466 1.733 3.375 Recovery rate, % 67.4 57.8 27.1 68.8 10.6 2.0 Recovery rate, % solution / residue 77.8 64.6 33.8 76.1 13.3 2.3

[0127] The results in Tables 5 and 6 show that the recovery rates of nickel, cobalt, and zinc are significantly better when using a leaching solution containing ammonia and glycine compared to a leaching solution containing only NaOH for pH adjustment.

[0128] The same material was also leached with an acidic leaching solution containing glycine and citric acid at a pH of 4. This solution contained 20 g / L glycine and 20 g / L citric acid. The results are shown in Table 7 below.

[0129] Table 7

[0130] Ni Co Zn S Fe Mg Metals contained (g) 4.46 0.122 0.041 2.729 2.172 3.90 Metals leached from the residue (g) 0.879 0.04 0.008 1.0777 1.1507 2.41 Metal (g) leached from the solution 3.45 0.085 0.029 1.9820 0.857 0.47 Total leachate (g) 4.33 0.122 0.037 3.0597 2.0077 2.88 Recovery rate, % 77.4 69.9 71.6 72.63 39.4 12.05 Recovery rate, % solution / residue 79.7 69.40 79.18 64.8 42.7 16.3

[0131] The results in Table 7 show that relatively high recoveries of Ni, Co, and Zn were achieved even at acidic pH by using glycine and citric acid solutions instead of glycine and ammonia solutions for leaching. Acidic leaching can be desirable for certain types of ore materials and electronic waste. However, it is worth noting that under these acidic conditions, the selectivity of the target metal relative to other elements in the material, particularly Fe and Mg, is reduced. Therefore, a neutralization step may need to be included after the leaching step, followed by precipitation of other elements from the solution.

[0132] Example 10

[0133] Extraction of precious metals, including palladium and platinum, from nickel concentrate using leaching solutions containing amino acids and ammonia has been tested. Table 8 lists the metal content of the tested nickel concentrates containing precious metals and PGM metals.

[0134] Table 8

[0135]

[0136] Table 9 lists the leaching conditions using a solution at pH 10.2 containing 0.5 mol / L glycine and 1.1 mol / L ammonia, as well as the metal (%) extracted from Ni concentrate containing precious metals and PGM (palladium and platinum) metals.

[0137] Table 9

[0138] Leaching conditions and metal extraction Ni concentration solid,% 10 Ammonia, molar 1.1 glycine, mole 0.5 Duration of stay, in hours 72 Ni extraction, % 90.9 Co extract, % 85.5 Pd extraction, % 44.5 Au extraction, % 60.1 Pt extraction, % 19.9 Ag extraction, % 51.2

[0139] The results in Tables 8 and 9 show that high recoveries of Ni and Co, as well as reasonable to good recoveries of noble metals including Au, Ag, Pd, and Pt, can be achieved at alkaline pH by leaching with glycine and ammonia solutions.

[0140] Example 11

[0141] Extraction of precious metals, including palladium and platinum, from oxide samples containing gold and platinum group metals (PGMs) using a leaching solution containing amino acids and ammonia has been tested. Table 10 lists the metal content of the oxide samples tested.

[0142] Table 10

[0143]

[0144] In the glycine-ammonia system, increasing one or more of temperature, pH, glycine concentration, and dissolved oxygen increased the amount of precious metals (including palladium and platinum) extracted. The leaching solution contained 0.5 mol / L glycine and 1.1 mol / L ammonia at a pH of 10.2. The solids content, leaching conditions, and percentage of extracted metals are listed in Table 11 below.

[0145] Table 11

[0146] Leaching conditions and metal extraction oxide samples solid,% 12.5 Ammonia, molar 1.1 glycine, mole 0.5 Duration of stay, in hours 48 Pd extraction, % 44.1 Au extraction, % 52.1 Pt extraction, % 17.9

[0147] The results in Tables 10 and 11 demonstrate that reasonable to good recoveries of precious metals including Au, Pd, and Pt can be achieved at alkaline pH by leaching with glycine and ammonia solutions.

[0148] Although many specific process implementations have been described, it should be understood that the process can be implemented in many other forms.

[0149] In the following claims and the preceding description, unless the context requires otherwise due to explicit language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, that is, to specify the presence of the said feature but not to exclude the presence or addition of further features in the various embodiments of the apparatus and methods disclosed herein.

Claims

1. A process for recovering one or more target metals from a material containing noble metals and / or chalcophile metals, said target metals being selected from noble metals and chalcophile metals, said process comprising: (i) Leaching the metal-containing material with an aqueous leaching solution to produce a leachate containing the target metal, the aqueous leaching solution comprising: "Metal release agent" comprises an amino acid or a derivative thereof, said amino acid or derivative thereof for releasing a target metal from a material to form a releasing ion of the target metal, said releasing ion of the target metal forming an aqueous complex with the amino acid or derivative thereof; and "Metal retaining agents" comprise one or more of ammonia, ammonium salts, carboxylic acids, and carboxylate salts, wherein the metal retaining agent complexes with the releasing ions of the target metal and extends the solubility limit of the released ions; and (ii) Extracting the metal from the leachate, wherein one or more target metals are selected from gold, silver, palladium, platinum, copper, nickel, cobalt, and zinc; and in: • When the metal retainer is selected from one or more carboxylic acids and carboxylates, the metal retainer is present in the solution at a concentration of at least 0.001 mol / L; • When the metal retainer is selected from one or more of ammonia or ammonium salts, the metal retainer is present in the solution at a concentration between 6 mmol / L and 5 mol / L.

2. The process according to claim 1, wherein the carboxylic acid is selected from dicarboxylic acids, hydroxycarboxylic acids, and ethylenediaminetetraacetic acid (EDTA).

3. The process according to claim 1, wherein the carboxylate is selected from dicarboxylate, hydroxycarboxylate and EDTA salt.

4. The process according to claim 1, wherein the amino acid comprises one or more of the following: glycine, histidine, valine, alanine, phenylalanine, cysteine, aspartic acid, glutamic acid, lysine, methionine, serine, threonine, and tyrosine.

5. The process according to claim 4, wherein the amino acid comprises glycine or glutamic acid.

6. The process according to any one of claims 1 to 5, wherein the concentration of amino acids in the solution ranges from 0.01 g to 250 g per liter.

7. The process according to any one of claims 1 to 5, wherein the metal retainer comprises ammonia or an ammonium salt.

8. The process according to claim 7, wherein the ammonium salt is selected from ammonium sulfate, ammonium halide, ammonium carbonate, ammonium nitrate, ammonium oxalate, and ammonium acetate.

9. The process according to any one of claims 1 to 5, wherein the molar ratio between the target metal ions in the solution and the metal retaining agent is 1:2 to 1:

8.

10. The process according to any one of claims 1 to 5, wherein the leaching is carried out in the presence of an oxidant selected from gaseous and dissolved air, and gaseous and dissolved oxygen.

11. The process according to any one of claims 1 to 5, wherein the leaching is carried out under alkaline conditions.

12. The process according to any one of claims 1 to 5, wherein the leaching is carried out under acidic conditions.

13. The process according to any one of claims 1 to 5, wherein the material containing precious metals and / or chalcophilic metals is selected from ores, concentrates, waste, mining or metallurgical process intermediates or metal-contaminated soil.

14. The process according to any one of claims 1 to 5, wherein the one or more target metals are non-precious metals.

15. The process of claim 14, wherein the one or more target metals are selected from nickel, cobalt and copper.

16. The process of claim 15, wherein the target metal is selected from nickel and cobalt.

17. The process according to any one of claims 1 to 5, wherein the metal-containing material is nickel ore and / or cobalt ore.

18. The process according to claim 15, wherein the target metal is copper.

19. The process according to any one of claims 1 to 5, wherein the metal-containing material is electronic waste.

20. The process according to any one of claims 1 to 5, wherein the leaching solution comprises a dissolved oxygen concentration of 0.1-100 mg per liter.

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