Leaching method

Abstract

A process for leaching of gold / copper bearing sulphide mining material, the process comprising two leaching stages, a gold leaching stage in which gold is leached from the material using a gold leach solution, and a copper leaching stage in which copper is leached from the material using a copper leach solution.

Description

[Technical field]

[0001] The present invention relates to a method for leaching gold, copper and optionally other valuable metals such as silver from metal-bearing materials including mined ores and mining wastes (leaching).

[0002] The term "mined" material includes mined material that is removed from a mine and transported directly for downstream processing, and mined material that is stored and transported from within the storage area for downstream processing.

[0003] The invention is particularly, but not exclusively, concerned with leaching gold and copper, and optionally other valuable metals such as silver, from mined materials in the form of mined ores.

[0004] The term "mined" ore, as used herein, is understood to include, but is not limited to, (a) crude ore, and (b) crude ore that has been subjected to at least primary crushing or similar or further size reduction after the material has been mined and before it is sorted.

[0005] The term "ore" is understood herein to mean a naturally occurring rock or deposit containing one or more valuable minerals, usually valuable metals, that can be extracted, processed and sold profitably.

[0006] The present invention also relates in particular, but not exclusively, to leaching any one or more of: (a) gold / copper-bearing ore (which may be in the form of agglomerates of ore fragments); (b) ore concentrate; and (c) ore or concentrate tailings produced, for example, by flotation or other downstream processing of the ore or concentrate.

[0007] The invention also relates to leaching gold / copper bearing sulfide materials, such as gold / copper bearing sulfide ores, particularly but not exclusively, sulfide ores containing copper minerals such as chalcopyrite (CuFeS2) and / or enargite (Cu3AsS4). The sulfide ores may contain other copper minerals. The sulfide ores also contain gold.

[0008] It should be noted that the present invention also extends to the leaching of metal-bearing materials that have been classified by mine operators as being waste and therefore as being "uneconomical" to recover the metals from using conventional recovery options (i.e., processing options that were used in commercial mines prior to the present invention).

[0009] It is also noted that metalliferous materials may include concentrates of materials, including concentrates of mined materials, including concentrates of mined ores.

[0010] The term "concentrate" is understood herein to mean the result of increasing the concentration of a target (i.e., desired) metal or metal-containing mineral in an input material. [Background technology]

[0011] Gold and copper are valuable metals and the economically viable mining and recovery of these metals from metal-bearing materials, including mined ores and other mined materials, represents an increasingly complex and multifaceted technical challenge.

[0012] Focusing initially on copper, in the leaching of copper-bearing mined material in the form of ore (including copper-bearing sulfide ores such as chalcopyrite and / or enargite or other copper-bearing sulfide minerals), the particle size of the ore is typically reduced from crude ore size, for example by crushing and grinding operations, to allow processing by heap leaching, vat leaching, or other reactor leaching options.

[0013] These leaching processes include the application of acids and oxidizing agents to dissolve copper into solution. The copper is then recovered from the acid solution by a variety of recovery options including solvent extraction and electrowinning (SX / EW), cementation to more active metals such as iron, hydrogen reduction, and direct electrowinning. The acid solution is regenerated and recycled to leach more copper from the ore.

[0014] Leaching may be enhanced by the use of microorganisms.

[0015] Generally, leaching can result in lower metal recovery rates than other process options for recovering copper from sulfide ores (e.g., grinding and flotation), in which a copper-bearing concentrate is produced which is then smelted to produce copper metal.

[0016] It is known that it is difficult to leach more than 20-40% by weight of the total copper from chalcopyrite by heap leaching.

[0017] The low copper recovery from chalcopyrite is often associated with the formation of a passive film on the surface of the chalcopyrite, which is thought to consist of decomposition products from the dissolution reaction.

[0018] Applicants have developed techniques for leaching copper from copper-bearing sulfides, such as gold / copper-bearing sulfide ores and sulfide wastes.

[0019] Applicant's technology is described and claimed in International Application Publication Nos. PCT / AU2016 / 051024, PCT / AU2018 / 050316, and PCT / AU2019 / 050383, the disclosures of which are incorporated herein by cross-reference.

[0020] It is known that gold may be present in copper-bearing materials such as gold / copper-bearing sulfide ores and sulfide waste materials.

[0021] These ores are the focus of this invention and are hereinafter referred to as "gold / copper bearing ores".

[0022] There are clear economic advantages to leaching both gold and copper from such gold / copper bearing ores. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] International Application No. 2017 / 070747 [Patent Document 2] International Application No. 2018 / 184071 [Patent Document 3] International Application No. 2019 / 213694 Summary of the Invention [Problem to be solved by the invention]

[0024] However, leaching gold and copper from gold / copper-bearing ores presents technical challenges that make it difficult to do efficiently and cost-effectively.

[0025] The above statements are not intended to be an admission of common knowledge in Australia or anywhere else. [Means for solving the problem]

[0026] Applicant has identified conditions that allow for the leaching of gold from a gold / copper bearing material, such as a gold / copper bearing mined ore, in one step, and for the leaching of copper from a gold / copper bearing material, such as a gold / copper bearing mined ore, in another step of the process, efficiently and cost effectively.

[0027] Broadly speaking, the present invention provides a process for leaching gold / copper bearing materials, such as gold / copper bearing mined ores and waste materials, which comprises two leaching stages, a gold leaching stage in which gold is leached from the material using a gold leach solution, and a copper leaching stage in which copper is leached from the material using a copper leach solution.

[0028] The gold / copper bearing material may be mined ore.

[0029] The mined ore may be a copper sulfide-containing ore.

[0030] The mined ore may be chalcopyrite ore.

[0031] The term "chalcopyrite ore" is understood herein to mean an ore that contains the mineral chalcopyrite. The ore may also contain other copper-bearing minerals. The ore may also contain pyrite.

[0032] The gold / copper bearing material may be mined material that has been classified as waste by the mine operator and is, for example, stored at the mine.

[0033] In the gold leaching stage, leaching conditions can be selected such that substantially no copper is leached.

[0034] In the case of gold / copper bearing ores, ores with low acid solubility for copper are typically preferred for the present process, since taking copper into solution during the gold leaching process can complicate downstream processing of the leachate. This problem is less likely to occur if the gold is leached first, followed by copper leaching.

[0035] It is noted that the copper-bearing ore concentrates of interest to applicants are typically primarily copper sulfide minerals that are insoluble in acid (unless they are very old, in which case surface oxidation will have occurred).

[0036] In the copper leaching stage, leaching conditions can be selected such that substantially no gold is leached.

[0037] Leaching conditions may be selected such that in the gold leaching stage, substantially no copper is leached and in the copper leaching stage, substantially no gold is leached.

[0038] The term "substantially not leached" in the context of copper is understood herein to mean that less than 5% by weight, typically less than 1% by weight, more typically less than 0.5% by weight of copper in a gold / copper-bearing material, such as a gold / copper-bearing ore, is leached in the gold leaching stage.

[0039] The term "substantially not leached" in the context of gold is understood herein to mean that less than 5% by weight, typically less than 1% by weight, more typically less than 0.5% by weight of gold in a gold / copper-bearing material, such as a gold / copper-bearing ore, is leached in the copper leaching stage.

[0040] Carrying out at least one leach under conditions which leach gold or copper without substantially leaching other metals is advantageous in that it provides the opportunity to: (a) Optimizing the conditions of the leaching step to maximize recovery of leached metals. (b) Simplify and optimize downstream recovery of leach metals from solution from the leaching stage.

[0041] The gold leaching step may be carried out before the copper leaching step.

[0042] The gold leaching step may follow the copper leaching step.

[0043] The following description focuses on the use of the above method for leaching gold / copper-bearing material in the form of gold / copper-bearing mined ores, it being emphasized that the invention also relates to the use of the above method for leaching gold / copper-bearing material in the form of gold / copper-bearing waste, such as in waste dumps.

[0044] In this regard, the present invention provides a method for leaching a gold / copper bearing mined ore which includes two leaching stages, a gold leaching stage in which gold is leached from the ore using a gold leach solution, and a copper heap leaching stage in which copper is leached from the ore using a copper leach solution.

[0045] The mined ore may be a copper sulfide-containing ore.

[0046] This method is (a) a gold leaching stage comprising leaching gold from the ore with a gold leach solution to produce a gold-containing solution and a gold-depleted ore; (b) a copper leaching step, comprising leaching copper from the gold-deficient ore with a copper leach solution to produce a copper-containing solution; may include.

[0047] This method is (a) a copper leaching step comprising leaching copper from the ore with a copper leach solution to produce a copper-containing solution and a copper-depleted ore; (b) a gold leaching step, comprising leaching gold from the copper-deficient ore with a gold leach solution to produce a gold-containing solution; It may include a reverse leaching step sequence having

[0048] The gold leaching stage may be a heap leaching stage.

[0049] The gold leaching step may be carried out on the agglomerates of ore fragments.

[0050] The copper leaching stage may be a heap leaching stage.

[0051] The copper leaching step may be carried out on the agglomerates of ore fragments.

[0052] The term "fractions" is understood herein to mean mined or processed (e.g., crushed) material of any suitable size, taking into account the material handling and throughput of the equipment used to carry out the method. It is also noted that the term "fractions" as used herein may be understood by those skilled in the art to be more appropriately described as "particles." It is intended that both terms be used synonymously.

[0053] The method may include forming a heap of ore and sequentially performing gold and copper leaching steps on the ore in the heap.

[0054] Alternatively, the method may include forming a heap of ore and carrying out a gold leaching step, thereafter forming an agglomerate of gold-deficient ore, forming a heap of the agglomerates and carrying out a copper leaching step on the gold-deficient ore in the agglomerates in the heap.

[0055] Alternatively, the method may include forming an agglomerate of ore, forming a heap, and sequentially carrying out gold and copper leaching steps on the agglomerated ore in the heap.

[0056] The method may include a heap washing step between successive leaching steps.

[0057] The heap cleaning stage has the following advantages: (a) the recovery of residual gold in the heap or in leachate retained in the heap; and (b) a dilution effect on components within the heap, or on components of the leachate retained within the heap, that may adversely affect the effectiveness of subsequent leaching stages within the heap; can be provided.

[0058] The method may include forming an agglomerate of ore, forming a heap of the agglomerates, and sequentially performing copper leaching and gold leaching steps on the agglomerate ore in the heap.

[0059] Alternatively, the method may include forming a heap of ore and carrying out a copper leaching step, thereafter forming an agglomerate of copper-deficient ore, forming a heap of the agglomerates and carrying out a gold leaching step on the copper-deficient ore in the agglomerates in the heap.

[0060] Alternatively, the method may include forming a heap of ore and sequentially carrying out copper and gold leaching steps on the ore in the heap.

[0061] The method may include a heap washing step between successive leaching steps.

[0062] The heap cleaning stage has the following advantages: (a) recovery of residual copper in the heap or in leachate retained in the heap; and (b) dilution effects on components in the heap, or of the leachate retained in the heap, that may adversely affect the effectiveness of subsequent leaching stages in the heap; and can be provided.

[0063] It should be noted that the present invention is not limited to heap leaching of ores.

[0064] One option, among many others, is vat leaching the ore. Another option is dump leaching the ore. Another option is a stirred tank in which the ore is leached.

[0065] Typically, the gold leaching step is carried out under acidic conditions.

[0066] Typically, the gold and copper leaching steps are carried out under acidic conditions and, in practice, it is difficult to convert to basic conditions in one leach after a previous leach has been carried out under acidic conditions, or vice versa.

[0067] The gold leaching step may be a thiourea-based leaching carried out under acidic conditions.

[0068] The gold leaching stage may be a thiourea-based leach, where thiourea (CS(NH2)2) acts as a gold complexing / extracting agent that facilitates leaching of gold from the ore.

[0069] The present invention is not limited to thiourea-based leaching, but extends to any suitable leaching conditions that optimize gold leaching preferentially over copper leaching. Other options include, by way of example, bromide / bromine (or halide in general), thiocyanate (SCN-), and ethylenethiourea.

[0070] The gold leaching stage may involve controlling the concentrations of oxidizing agents such as ferric iron, peroxides, and permanganates in the leachate.

[0071] The gold leaching step may involve controlling the ferric concentration in the leachate so that copper is not leached.

[0072] For example, in some embodiments, the gold leaching stage may involve controlling the ferric concentration in the leachate to be between 0 and 5 g / L.

[0073] The choice of ferric concentration in the leachate is important in terms of the influence of ferric on the leaching conditions. For example, if the ferric concentration is too high, this may affect the control of the oxidation potential of the leachate to a target potential of, for example, 440 mV. Also, if the iron concentration is too high, oxidation of the ore may begin (as a side reaction) and other elements such as Cu may be unintentionally leached.

[0074] The gold leaching step may be carried out under ambient temperature conditions.

[0075] The gold leaching stage may involve controlling the heap temperature to at least 5°C, typically at least 10°C, more typically at least 20°C.

[0076] The gold leaching stage may involve controlling the heap temperature to below 50°C, typically below 40°C, more typically below 30°C.

[0077] The gold leaching step may involve controlling the pH of the leachate in the range of pH 1-4.

[0078] The gold leaching step may involve controlling the pH of the leachate in the range of pH 1-3.

[0079] It should be noted that if the pH becomes too high in the case of thiourea-based gold leaching step (a), the ferric iron present due to the partial oxidation of thiourea will start to flocculate out of solution.

[0080] The gold leaching stage may involve controlling the Eh of the leachate in the range of 350-550mV, typically 400-500mV.

[0081] The gold leaching stage may be carried out for any suitable period of time, taking into account factors such as the concentration of gold and the capital and operating costs for the type of leaching. For a typical heap leaching process, the leaching time is at least one month.

[0082] Options other than thiourea-based leaching include thiocyanate leaching at a pH in the range of 0.75-3.5, typically at a pH in the range of 1.0-3, more typically at a pH in the range of 1.5-2.5, and even more typically at a pH of about 2.0. Thiocyanate leaching can be performed at an Eh in the range of 600-700 mV. Other options include halide, bromide, iodide, and chloride.

[0083] The method may include selecting mining and leaching operation conditions, including, but not limited to, ore crush size, leaching reagent addition options, leaching reagent concentrations, leaching temperature, leaching time, ferric ion concentration, pH, and Eh of the leachate for the gold leaching stage and the copper leaching stage.

[0084] The method may include a separate recovery step for recovering gold and copper from the respective gold-bearing and copper-bearing solutions from the leaching step to produce recovered gold and copper streams and recovered gold-bearing and copper-bearing solutions.

[0085] Typically, the process involves separate gold and copper leaching steps and separate gold and copper recovery steps.

[0086] In the case of a thiourea-based gold leaching step, the process may include a residual thiourea removal step in which thiourea is removed from the recovered gold-bearing solution from the gold recovery step and a thiourea-depleted solution is used in the copper leaching step.

[0087] Some methods for recovering gold from the gold / thiourea solution from the gold leaching stage include electrochemical, activated carbon adsorption, ion exchange adsorption, agglomeration with metal powder, and reduction with sulfur dioxide gas.

[0088] The recovered gold- and copper-bearing solutions from the recovery stage can be reclaimed and recycled to the heap as part of the leachate.

[0089] The copper leaching stage may involve controlling the heap temperature to less than 75°C, typically less than 65°C, typically less than 60°C, typically less than 55°C, typically less than 50°C, more typically less than 45°C.

[0090] The copper leaching step may involve controlling the heap temperature to at least 10°C, typically at least 20°C, typically at least 30°C, more typically at least 40°C.

[0091] Typically, the copper leaching stage involves controlling the heap temperature in the range of 55-65°C to accommodate ambient temperatures in a variety of climates. Currently, the target heap temperature is 60°C.

[0092] The copper leaching stage may involve controlling the oxidation potential of the leach solution during the active leaching phase of the process to less than 700mV, typically less than 660mV, typically in the range of 600-660mV, more typically 630-660mV, all potentials relative to a standard hydrogen electrode. It should be noted that the oxidation potential will change during the leaching process, and as more copper is leached the oxidation potential is likely to be higher, and the reference to the "active leaching phase" is intended to acknowledge this change in potential.

[0093] Typically, the copper leaching step is carried out under acidic conditions.

[0094] The copper leaching stage may involve controlling the pH of the leach solution to less than 3.2, typically less than 3.0, typically less than 2.0, typically less than 1.8, typically less than 1.5, typically less than 1.2, typically less than 1.0.

[0095] The copper leaching step may involve controlling the pH of the leach solution to be greater than 0.3, typically greater than 0.5, typically greater than 1.

[0096] Typically, the copper leaching stage involves controlling the pH of the leach solution to between 0 and 2, more typically between 1 and 1.4, preferably pH 1.2.

[0097] The optimum pH range for any given situation will vary depending on a variety of factors including mineralogy, heap temperature, leach composition, etc.

[0098] The copper leaching step can include any suitable leaching time.

[0099] The copper leaching step may include providing silver in a form and within a specified concentration range that successfully catalyzes the leaching of copper from the ore.

[0100] The above-mentioned PCT / AU2016 / 051024 (Patent Document 1) discloses the addition of silver.

[0101] The copper leaching step may include providing silver at a concentration of less than 2 g Ag / kg Cu ​​to catalyse the leaching of copper.

[0102] Typically the silver concentration is less than 1.5 g Ag / kg Cu.

[0103] More typically, the silver concentration is less than 1 g Ag / kg Cu.

[0104] Even more typically, the silver concentration is less than 0.5 g Ag / kg Cu.

[0105] Even more typically, the silver concentration is less than 0.4 g Ag / kg Cu.

[0106] Gold / copper bearing ores may in some circumstances have naturally occurring silver.

[0107] Naturally occurring silver in gold / copper-bearing ores may have catalytic properties for copper leaching. Naturally occurring silver is found in the form of native silver, argentite (AgS), chlorargillite (AgCl), as naturally occurring silver inclusions in copper minerals and pyrite, and as silver-sulfur salts (e.g., tetrahedrite (Cu,Fe,Zn,Ag 12 Sb4S 13 AgSbS), pyragilite (AgSbS), proustite (AgAsS).

[0108] If naturally occurring silver is present that has catalytic properties towards copper leaching, the operator may take this into account and select a lower concentration of added silver than would otherwise be the case.

[0109] As an example, there may be cases where no silver needs to be added.

[0110] This method is (a) forming agglomerates of silver with fragments of ore; (b) leaching the agglomerates, for example in an agglomerate heap, with a leach liquor in a copper leaching stage; may include.

[0111] The agglomeration step (a) may include forming agglomerates by mixing the ore fragments and silver together in an agglomeration step.

[0112] The agglomeration step (a) may involve adding silver to the ore fragments and then mixing the ore fragments together in an agglomeration step to form agglomerates.

[0113] The agglomeration step (a) may comprise forming agglomerates of the ore fragments in an agglomeration step and then adding silver to the agglomerates.

[0114] The agglomerates formed in the aggregation step (a) may have a low total silver concentration.

[0115] As noted above, the fragments in the agglomerates may already have naturally occurring low silver concentrations prior to the addition of silver in agglomeration step (a), and some or all of the naturally occurring silver may have catalytic properties for copper leaching. In practice, this is a factor to be considered when determining the amount of silver to add during agglomeration step (a) so that the overall active silver concentration remains within the required concentration range. To distinguish between the naturally occurring silver concentrations in ores such as chalcopyrite ore and the silver that is added during the agglomeration step, the added silver will hereinafter be referred to as "added silver" or a similar term.

[0116] The added silver and total silver concentrations in the agglomerates are expressed herein as grams of silver per kilogram of copper in the ore in the agglomerates. The necessary concentration of silver added in the agglomeration step to achieve a selected agglomerate silver concentration (naturally occurring silver and added silver) can be readily determined by one skilled in the art. It is also recognized that there are different measures of silver concentration in the patent and non-patent literature, and that it may be difficult to compare the different ranges disclosed in the literature.

[0117] The added silver concentration in the agglomerates may be less than 2 grams of silver per kilogram of copper in the ore in the agglomerates, typically less than 1.5 grams of silver per kilogram of copper in the ore in the agglomerates, more typically less than 1 gram of silver per kilogram of copper in the ore in the agglomerates, and even more typically less than 0.5 grams of silver per kilogram of copper in the agglomerates, and even more typically less than 0.4 grams of silver per kilogram of copper in the ore in the agglomerates.

[0118] The agglomeration step (a) may involve adding silver to the ore fragments by any suitable means and in any suitable form.

[0119] The added silver can be in the form of a solid, for example, the added silver can be present in a pyrite concentrate that is added to the ore during the flocculation process.

[0120] The added silver may be present in solution.

[0121] The added silver may be in the form of a solid that becomes mobile when dissolved in the leachate, or it may be aggregated or otherwise deposited on the surface of the ore.

[0122] Typically, the additive silver is added to the ore pieces while they are being mixed.

[0123] The flocculation step (a) may comprise dispersing the added silver on the surfaces of particles of the copper-containing mineral in the ore fragments.

[0124] The agglomeration step (a) may include dispersing the added silver within the ore fragments.

[0125] The agglomeration step (a) may involve adding silver to the ore fragments in the form of an aerosol, where the term "aerosol" is understood to mean a colloidal suspension of particles, typically in the form of a powder, in air or gas.

[0126] The agglomeration step (a) may involve adding silver in solution to the ore fragments in the form of a mist or spray, the terms "mist" and "spray" being understood to mean small droplets of silver solution suspended in the air.

[0127] The choice of mist / spray / aerosol as a vehicle for adding the silver solution to the ore fragments allows for maximizing the delivery of low concentrations of silver to a substantially larger mass (and surface area) of the ore fragments. The mist / spray / aerosol approach allows for the delivery of silver to a significant portion of the ore fragments.

[0128] Typically, the agglomeration step (a) may involve adding silver to the ore pieces in the form of a mist, spray, or aerosol while the ore pieces are being mixed.

[0129] Typically, the agglomeration step (a) involves using a low concentration of silver compared to the amount of copper-bearing ore fragments.

[0130] The agglomeration step (a) may also include forming an agglomerate by mixing an acid, typically sulfuric acid, with the ore fragments and silver. The acid may be added simultaneously with, before or after the silver solution. The acid concentration added may be less than 50 kg H2SO4 / tonne of dry ore, typically less than 30 kg H2SO4 / tonne of dry ore, less than 10 kg H2SO4 / tonne of dry ore, or less than 5 kg H2SO4 / tonne of dry ore. Typically the acid concentration is between 0.5 and 10 kg H2SO4 / tonne of dry ore.

[0131] The flocculation step (a) may also include forming a floc by mixing a microorganism capable of assisting in the leaching of copper with the ore fragments and silver. The microorganism may be added simultaneously with, before or after the silver solution. The microorganism may be one or more of mesophilic or thermophilic (moderate or extreme) bacteria or archaea. The microorganism may be a bacteria or an archaea. The microorganism may be a mesophilic acidophile or a thermoacidophile.

[0132] The aggregation step (a) may comprise simultaneously mixing and agglomerating the fragments.

[0133] The aggregation step (a) may involve mixing the fragments in one step and then agglomerating the mixed fragments in a next step. There may be an overlap between the mixing and aggregation steps.

[0134] The ore fragments may contain fissures to facilitate dispersion of the silver solution with the fragments.

[0135] The added silver may be present in an aqueous solution.

[0136] The added silver may be in a soluble form, such as silver nitrate.

[0137] The added silver may be in an insoluble or sparingly soluble form, such as silver sulfate, silver chloride, silver sulfide, etc. The term "sparely soluble" is understood herein to mean a salt having a solubility of less than 0.01 mole / liter.

[0138] The added silver may be present in a pyrite concentrate that is added to the ore during the flocculation process.

[0139] The copper leaching step may include providing additives other than silver to the copper leaching step (for example additives described in the above-mentioned PCT / AU2019 / 050383).

[0140] PCT / AU2019 / 050383 is based on the recognition that leaching of copper-bearing ores or ore concentrates, or tailings of ores or concentrates, may be enhanced through the formation of complexes between (a) sulfur derived from copper minerals in the ore, and (b) additives that result in an increased dissolution rate.

[0141] As an example, sulfur may be present in a passivation layer on copper minerals and a complex may be formed between the additive and sulfur in the passivation layer to either disrupt the passivation layer or reduce the formation of the layer, thus allowing greater access for leaching copper from the copper minerals.

[0142] PCT / AU2019 / 050383 (Patent Document 3) discloses a specific group of nitrogen-containing complexing agents that are effective additives, including compounds that contain the following molecular scaffold, or polymers that contain the molecular scaffold that is repeated throughout the polymer: [ka] Where: the two nitrogen atoms are each independently substituted or unsubstituted, and each nitrogen atom is selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amine group; the carbon atoms may each be substituted or unsubstituted; The bond between the nitrogen atom and the carbon atom in the scaffold may be a single bond or a multiple bond; The bond between two carbon atoms in the scaffold may be a single bond or a multiple bond.

[0143] The concentration of the nitrogen-containing complexing agent additive in the leachate may be up to 10 g / L, typically up to 5 g / L, typically up to 2.5 g / L, typically up to 1.5 g / L, typically up to 1.25 g / L, more typically up to 1 g / L.

[0144] The process may include continuously or periodically adding a nitrogen-containing complexing agent additive to the leachate during the process to maintain the required concentration during the process.

[0145] The additive may be added to the ore prior to leaching.

[0146] The method of addition may be to add to the agglomerates of ore fragments prior to leaching.

[0147] For example, additives may be added while forming the agglomerates of ore fragments.

[0148] The copper leaching step (b) may include supplying a leachate to a heap of agglomerates from the agglomeration step (a), flowing the leachate over the heap to leach copper from the agglomerates, collecting the leachate from the heap, treating the leachate, and recovering the copper from the leachate.

[0149] The leach solution may contain microorganisms that aid in the leaching of copper.

[0150] The microorganism may be one or more of mesophilic or thermophilic (moderate or extreme) bacteria or archaea. The microorganism may be a bacterium or an archaea. The microorganism may be a mesophilic or thermophilic acidophilic bacterium.

[0151] The copper leaching step may include carrying out the leaching step with a leach solution in the presence of silver and an activator that activates the silver such that it promotes copper leaching.

[0152] The activator may be any suitable reagent capable of activating silver such that it promotes the extraction of copper.

[0153] The activator can be any one or more of silver complexing ligands such as chloride, iodide, bromide, and thiourea.

[0154] The activator may be present in the process by spraying or otherwise dispersing in liquid or solid form onto the ore fragments or ore concentrate, including before, during, or after agglomeration if agglomeration is performed, or as a component of the leach solution.

[0155] When an activator is present in the method as a component of the leachate, the method can include providing a selected concentration or range of concentrations of the activator in the leachate.

[0156] The selected concentration or concentration range of the activator in the leachate may be one or more of the following active steps: (a) adding an activator to the leachate; (b) removal of the activating agent from the leachate; (c) addition of an activator in the flocculation step; (d) mixing of different ore types taking into account the soluble activators in the ores; (e) Selection of water source / type and blending / mixing with respect to the concentration of activator in the ore (e.g., use of seawater); (f) Any other anthropogenic intervention in one or more inputs to the leaching process that may affect the concentration of soluble activator in the leaching process. This may be the result of:

[0157] The selected concentration or concentration range of activator may be different from the background concentration of activator in the leachate, ore, or concentrate. The present invention requires making an assessment of the required concentration or concentration range of activator for a given ore or concentrate, and evaluating the available water source(s) and related conditions and controlling the process such that the required concentration or concentration range of activator is present, e.g., taking into account steps (a)-(e) above.

[0158] The method can include monitoring the concentration of any one or more silver complexing ligands, such as chloride, iodide, bromide, and thiourea.

[0159] The copper leaching step may be carried out in the presence of a low concentration or range of concentrations of an activator selected from any one or more silver complexing ligands such as chloride, iodide, bromide, and thiourea.

[0160] The meaning of the term "low concentration" with respect to chloride, iodide, bromide, thiourea, or other silver complexing ligands will vary in any given situation depending on many factors, including the mineralogy of the ore, the physical characteristics of the ore fragments (e.g., fragment size and particle size distribution), the characteristics of the aggregates (e.g., size and porosity), the copper concentration in the ore, the silver concentration (naturally occurring in the ore fragments and added as part of the aggregates), the composition of the leachate, and, in the case of heap leaching, the characteristics of the heap, including the porosity of the heap.

[0161] Low concentrations of chloride may be up to 5 g / L, typically up to 4 g / L, typically up to 2.5 g / L, typically up to 1.5 g / L, typically up to 1.25 g / L chloride, more typically up to 1 g / L in the leachate.

[0162] A low concentration of chloride may be greater than 0.2 g / L, typically greater than 0.5 g / L, and more typically greater than 0.8 g / L.

[0163] Low concentrations of iodide and bromide can be the same as for chloride.

[0164] Low concentrations of thiourea can be less than 10 g / L in the leachate.

[0165] Typically, it is not necessary for the leach solution to contain thiosulfate or other additives to inhibit precipitation of silver chloride, silver iodide, or silver bromide.

[0166] The method may include reducing the size of the mined ore prior to the leaching step.

[0167] By way of example, the method may include crushing the mined ore prior to the leaching step. The mined ore may be crushed using any suitable means.

[0168] The method may include crushing the mined ore in a primary crushing step prior to the leaching stage.

[0169] The term "primary crushing" is understood here to mean the crushing of the ore to a maximum dimension of 250-150 mm in the case of copper-bearing ores in which the copper is in the form of sulfides. It should be noted that for ores containing different precious metals the maximum dimensions may be different.

[0170] The method may involve crushing the mined ore in a primary crushing step, then crushing it in a secondary, optionally tertiary, optionally quaternary crushing step prior to the agglomeration step (a).

[0171] The present invention also provides a leaching process for leaching a gold / copper-bearing material, comprising the steps of: (a) a gold leaching unit operation comprising leaching gold from a material with a gold leach solution to produce a gold-containing solution and recovering gold from the solution; (b) a copper leaching unit operation leaching copper from the material with a copper leach solution to produce a copper-containing solution and recovering copper from the solution; The present invention provides a leaching operation, comprising:

[0172] The mined material may be a copper sulfide-containing ore.

[0173] The present invention also provides a heap leaching operation for leaching gold / copper bearing material, comprising: (a) a heap of mined material and / or agglomerated fragments of mined material; (b) a leachate supply unit for supplying gold leachate to the heap for carrying out a gold leach step on material in the heap; and (c) a leachate supply unit for supplying copper leachate to the heap for carrying out a copper leach stage on material in the heap, either before or after the gold leach stage; (d) a gold recovery unit for recovering gold from the gold-bearing solution discharged from the heap during the gold leaching stage to produce a recovered gold stream and a recovered gold-bearing solution; (e) a copper recovery unit for recovering copper from the copper-bearing solution discharged from the heap during the copper leaching stage to produce a recovered copper stream and a recovered copper-bearing solution; The present invention provides heap leaching operations, including

[0174] The heap leaching operation may include a regeneration unit for regenerating the recovered gold-bearing solution.

[0175] The heap leaching operation may include a regeneration unit for regenerating the recovered copper-bearing solution.

[0176] A heap can contain multiple lifts.

[0177] The mined material may be a gold / copper sulfide bearing ore.

[0178] The mined material may be gold / copper sulfide bearing waste.

[0179] The invention is further described below, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0180] [Figure 1] 1 is a flow sheet of one embodiment of a method for leaching gold and copper from mined materials according to the present invention. [Diagram 2] 1 is a flow sheet of one embodiment of a method for leaching gold and copper from mined materials according to the present invention. [Diagram 3] 1 is a flow sheet of one embodiment of a method for leaching gold and copper from mined materials according to the present invention. [Figure 4] FIG. 1 is a graph of gold extraction versus time for Example 1 of the process of the present invention. [Diagram 5] 1 is a graph of copper extraction versus time for Examples 2-4 of the process of the present invention. [Figure 6] 1 is a graph of copper extraction versus time for Examples 5-7 of the process of the present invention. [Figure 7] FIG. 1 is a graph of gold extraction versus time for Example 8 of the process of the present invention. [Figure 8] 1 is a graph of copper extraction versus time for Example 8 of the process of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0181] The present invention enables gold to be leached from a gold / copper bearing material, such as a gold / copper bearing mined ore, in one step and copper to be leached from a gold / copper bearing material, such as a gold / copper bearing mined ore, in a separate step of the process, efficiently and cost effectively.

[0182] Some copper deposits contain large amounts of gold. However, the gold grade in such deposits may not be high enough to justify conventional gold leaching processes using cyanide. Even if the gold is extracted using cyanide, an expensive neutralization process is required to make the residue suitable for safe extraction of copper by acid leaching.

[0183] An embodiment of the present invention uses mild conditions to recover gold and subsequently extract copper, without the need for intermediate neutralization of the residue. An additional advantage is that the reagents used for leaching gold may also be beneficial for leaching copper. The term "mild conditions" includes, by way of example, thiourea-based leaches carried out at ambient temperature (25°C).

[0184] Experiments have shown that it is possible to leach up to 60% of the gold into solution under mild conditions, such as a thiourea-based leach carried out at ambient temperature (25°C).

[0185] These experiments also show that copper remains in the ore, providing the opportunity to recover it in a subsequent leaching step, an important feature as no other unwanted elements are co-extracted during each leaching step.

[0186] The present invention makes it possible to extract gold contained in some copper deposits into solution, the recovery of gold adding value to copper leaching operations using techniques such as those of the Applicant described and claimed in the above mentioned International Applications PCT / AU2016 / 051024, PCT / AU2018 / 050316 and PCT / AU2019 / 050383.

[0187] 1 to 3 are flowsheets of three embodiments of the method for leaching gold and copper from gold / copper bearing ores according to the present invention. These are not the only embodiments of the present invention.

[0188] Flow sheet of Figure 1 The flow sheet in Figure 1 is: (a) Within the box on the left side of the diagram, a gold leaching operation, generally identified by the reference numeral 3; (b) Within the box on the right side of the diagram, a copper leaching operation, generally identified by the numeral 5; Includes.

[0189] Referring to the figure, the gold / copper bearing mined material, in this embodiment crushed and crushed pieces of ore, is formed into a heap and leachate 35 is supplied to the top of the heap in a heap leaching stage 7 and allowed to percolate into the heap.

[0190] Gold is leached from the gold / copper bearing mined ore and taken into solution in leaching stage 7.

[0191] At the end of the gold heap leaching stage 7, the gold-depleted ore 41 is transferred to the copper leaching operation 5 for processing, as further described below. The end of the gold leaching stage 7 may be determined by leaching time, or remaining gold being a threshold concentration, or any other suitable factor.

[0192] The gold-containing solution 37 (referred to as “Au“PLS”” in the figure) discharged from the leaching stage 7 is transferred to the gold recovery stage 11.

[0193] Gold is recovered from the gold-containing solution 37 in a gold recovery stage 11, discharged and further processed to produce a gold product 13.

[0194] Recovered solution 39 is discharged from the gold recovery stage 11 and transferred to the leaching stage 7 where it becomes part of the feed leachate to the leaching stage 7.

[0195] The gold leaching stage 7 may be any suitable stage other than heap leaching, such as leaching in a stirred vat / tank in any other suitable vessel.

[0196] In the embodiment shown in Figure 1, the gold leaching stage 7 is a thiourea-based leaching carried out at ambient temperature (25°C) and the leachate fed to this stage has a pH of 1.5, a thiourea concentration of 5g / L and an iron concentration of 0.3g / L.

[0197] In any given situation, heap leaching times will vary depending on a variety of factors, but will typically be at least several days and up to several months.

[0198] It should be noted that the pH, thiourea concentration, and iron concentration mentioned above are for stirred reactor tests performed on minus 2 mm particles at ambient temperature.

[0199] Also note that ambient temperatures vary widely by location and season, and as long as the temperature in the heap is above freezing, gold will leach, but it will leach more slowly than if the heap temperature was 20°C or 25°C. Thiourea leaching typically produces very little heat.

[0200] In the copper leaching operation 5, gold depleted ore 41 is transferred to an agglomeration unit 15 and fed with the following feed materials: (b) silver-17 (as a silver solution in this embodiment (but solid form is also possible), typically at a silver loading concentration of less than 5 g silver per kg copper in the ore in the agglomerates); (c) any suitable concentration of sulfuric acid 19; (d) microorganisms 21 of any suitable type and in any suitable concentration; (e) an activator 23 (e.g., silver complexing ligands including chloride, iodide, bromide, and thiourea); The mixture is agglomerated using

[0201] The agglomeration unit 15 may be of any suitable structure, including a drum, conveyor (or other device) for mixing the feed material for agglomeration and agglomerating the feed material. Mixing and agglomeration of the feed material for agglomeration may occur simultaneously. Alternatively, mixing of the feed material may be performed first, and agglomeration (e.g., initiated by the addition of acid) may be performed after mixing is completed to the required extent. Furthermore, the timing of adding the feed material, then mixing, and agglomeration may be selected to meet the end-use requirements of the agglomerate. For example, in some circumstances it may be preferable to start mixing the ore fragments, then gradually add silver in solution or in solid form, acid, and microorganisms, in that order, at different start and end times within the agglomeration step. As a specific example, in some circumstances it may be preferable to start mixing the ore fragments, then add silver in solution or in solid form and acid together, and then add microorganisms at different start and end times of the agglomeration step.

[0202] Applicants have discovered that adding silver to the ore pieces as a solution in a fine mist or spray, or as solid particles in an aerosol, while the ore pieces are being mixed in a suitable mixer, such as a drum mixer, is a particularly suitable method of achieving the desired dispersion of silver on the ore pieces.

[0203] It is noted that the above-mentioned patent specifications of international applications PCT / AU2016 / 051024, PCT / AU2018 / 050316 and PCT / AU2019 / 050383 in the name of the applicant provide information regarding suitable flocculation conditions, the use of additives in addition to silver, and other steps of the copper leaching operation 5.

[0204] The clumps generated by the clumping unit 15 are then used to build a heap 25 .

[0205] Copper is then leached from the gold-depleted ore in the agglomerates in the heap 25 by supplying a suitable leach solution 43 to the heap. The copper leaching stage is operated for a suitable period of time. Typically, the copper leaching stage is operated for at least several months.

[0206] Heap 25 may be any suitable heap.

[0207] By way of example, the heap may be of the type described in patent specification PCT / AU2011 / 001144 (WO2012 / 031317) in the name of the applicant, the disclosures of the heap construction and heap leaching process in the international application publication are incorporated herein by cross-reference.

[0208] The aggregates produced by the aggregate unit 15 can be transported directly to a heap construction site. Alternatively, the aggregates can be stored and used as a heap as needed. The aggregate unit 15 and the heap 25 can be in close proximity. However, similarly, the aggregate unit 15 and the heap 25 do not have to be in close proximity.

[0209] Copper-containing solution 45 is discharged from heap 25 and transferred to copper recovery unit 27 .

[0210] Copper is recovered from the copper-containing solution 45 and processed in downstream processing units to form the copper product 29.

[0211] Recovered copper solution 47 is discharged from copper recovery unit 27 and transferred to regeneration unit 31 to produce leachate 43 that is recycled to heap 25. Make-up leachate may be added if necessary.

[0212] Flowsheet of Figure 2 The flow sheet in Figure 2 is a gold leaching operation generally identified by the numeral 3; a copper leaching operation, generally identified by the numeral 5; Includes.

[0213] The flowsheet of FIG. 2 includes all of the unit operations of the flowsheet of FIG. 1, with the same reference numbers used to describe the same components.

[0214] The flowsheet of FIG. 2 also includes transferring a portion 49 of the recovered gold solution 39 to the thiourea removal stage 31, removing thiourea from the solution, and transferring a thiourea-depleted solution 51 from the solid-liquid unit 9 to the gold-depleted ore stream 41 which is transferred to the copper leaching operation 5.

[0215] The thiourea depleted solution 51 may be required as a make-up solution for the copper leaching operation 5.

[0216] One thiourea removal option is activated carbon adsorption, after which the thiourea is desorbed from the carbon and reused in the process.

[0217] Flowsheet of Figure 3 The flowsheet of FIG. 3 is in reverse order to the flowsheets of FIGS. 1 and 2, in that the copper leaching operation 5 precedes the gold leaching operation 3.

[0218] The same reference numbers are used to describe the same features.

[0219] In this embodiment, at the end of the heap leaching stage 25, the gold leaching stage 7 of the gold leaching operation 3 is carried out on the existing heap.

[0220] Specifically, the copper-depleted solids from the copper leach do not physically move (as indicated by dashed line 53).

[0221] A thiourea-based gold leach solution is simply introduced into the heap, with washing steps between the leaching stages.

[0222] A heap leaching operation may be a multiple lift operation that adds new lifts to existing lifts after copper leaching is completed. EXAMPLES

[0223] <Example 1> A laboratory scale test run has been carried out by the Applicant according to the flowsheet in Figure 1, with a gold leaching step using thiourea, a solid / liquid separation step and gold-depleted solids transferred to be used as feedstock for a copper leaching step based on the above mentioned patent specifications of the Applicant's technology described in International Applications PCT / AU2016 / 051024, PCT / AU2018 / 050316 and PCT / AU2019 / 050383.

[0224] The results of the test work are as follows: (a) In the gold leaching stage, approximately 45.5% gold recovery, i.e., extraction of gold from the ore, was achieved. (b) No copper was detected in the gold-bearing solution from the gold leaching stage after 48 hours.

[0225] FIG. 4 is a graph of gold extraction versus time for the test runs.

[0226] The results of the test work indicate the feasibility of a two-stage heap leaching process in which gold is first extracted at near ambient temperatures (without bacteria), followed by copper leaching at elevated temperatures, using bacteria and under more oxidizing conditions than the gold leaching stage, as shown in Figures 1 and 2.

[0227] <Examples 2 to 8> The following examples describe leaching tests carried out on the following ore samples: [Table 1] [Table 2] [Table 3]

[0228] Examples 2 to 8 are summarized as follows. Examples 2 to 4 are sequences of gold leaching and subsequent copper leaching for ore type A. Examples 5-7 are sequences of copper leaching followed by gold leaching for ore type A. Example 8 is a gold leaching sequence followed by copper leaching of ore type B.

[0229] <Example 2> gold leaching process Example 2 was carried out according to the flow sheet of FIG.

[0230] 300 g of ore type A, stage-ground to approximately 2 mm in size, was mixed with 700 g of a pH 1.5 solution having the following composition: 3 g / L ferric sulfate and 5 g / L thiourea, with air being bubbled into the reactor at 1 L / min. The reactor contents were stirred using an overhead impeller and the temperature was maintained at 25° C. in a water bath during the test. Leaching was maintained for 10 days, with subsamples of the liquid collected at pre-set times. After leaching for 10 days, the residue was filtered from the solution. The solid residue was washed successively using two 500 mL lots of pH 1.5 solution, followed by thorough mixing and subsequent filtration for 10 minutes at each washing step. After the acid wash, the leach residue was washed using 1 L of deionized water for 10 minutes. The slurry was then filtered to produce a washed cake, which was then dried at 40° C. until all water was removed.

[0231] copper leaching process The residue from the above gold leaching process was subsequently subjected to a copper leaching process, where a slurry density of 20% was targeted. All the residues recovered from the gold leaching process were leached without any pre-treatment.

[0232] The composition of the leaching solution is as follows: [Table 4]

[0233] The test was maintained at 60°C using a water bath with a pH 1.2 target and an Eh target of 700mV. A bacterial inoculum was introduced after 30 days of operation. Samples were taken at predetermined times to track the extraction rate of Cu and analyzed for elemental composition. At the end of the test, the residue was filtered from the solution. The solid residue was washed successively using two 500mL lots of pH 1.2 solution. Each washing step was then thoroughly mixed followed by filtration for 10 minutes. After the acid wash, the leach residue was washed using 1L of deionized water for 10 minutes. The slurry was then filtered to produce a washed cake which was then dried at 40°C until all water was removed.

[0234] The final solid residue was analyzed for gold and other elements. Gold analysis was done by fire testing which gave an indication of any total gold still present in the residue. The residue was also analyzed using a cyanide leach to measure the cyanide soluble gold still present in the leach residue.

[0235] <Example 3> gold leaching process Example 3 was carried out similarly to Example 2 for ore type A, except that the thiourea concentration was reduced to 2.5 g / L. All other steps were similar.

[0236] copper leaching process The copper leaching step was carried out in a similar manner to Example 2.

[0237] <Example 4> gold leaching process Example 3 was carried out similarly to Example 2 for ore type A, except that the thiourea concentration was reduced to 1.25 g / L. All other steps were similar.

[0238] copper leaching process The copper leaching step was carried out in a similar manner to Example 2.

[0239] <Example 5> Example 5 was carried out according to the flow sheet of FIG.

[0240] copper leaching process Ore type A was subjected to the bulk copper leaching process. The ore was crushed to a size of approximately 2 mm. A slurry density of 20% was targeted for the copper leaching process. The composition of the leach solution was as follows: [Table 5]

[0241] The test used a hot plate and was maintained at 60°C with a pH target of 1.2 and an Eh target of 700mV. A bacterial inoculum was introduced after 23 days of operation. Samples were taken at pre-determined times to follow the extraction rate of Cu. At the end of the leaching period, the residue was separated from the liquid and washed thoroughly with an acidic solution of pH 1.2. The washed solid was then rinsed using deionized water followed by solid-liquid separation. The washed solid was dried at 40°C. The dried solid was mixed and divided into pieces of typically 300g for the subsequent gold leaching steps in this example and in Examples 6 and 7.

[0242] gold leaching process A portion of the copper leach residue described in the copper leaching step above was mixed with 700 g of a pH 1.5 solution having the following composition: 3 g / L ferric sulfate and 5 g / L thiourea, and air was bubbled into the reactor at 1 L / min. The reactor contents were mixed using an overhead impeller and the temperature was maintained at 25° C. in a water bath during the test. The leach was maintained for 10 days and subsamples of the liquid were collected at pre-set times. After leaching for 10 days, the residue was filtered from the solution. The solid residue was washed successively using 500 mL of pH 1.5 water by thoroughly mixing followed by filtration for 10 minutes at each wash step. After the acid wash, the leach residue was washed for 10 minutes using 1 L of deionized water. The slurry was then filtered to produce a washed cake, which was then dried at 40° C. until all water was removed.

[0243] <Example 6> Example 6 was carried out according to the flow sheet of FIG.

[0244] copper leaching process The copper leaching process was carried out as part of the bulk copper leaching described in Example 5. A portion of the leach residue was then used in the gold leaching process.

[0245] gold leaching process The residue from the copper leaching process was carried out in the same manner as the gold leaching process of Example 5. However, the thiourea concentration was 2.5 g / L. All other test conditions were as described in Example 5.

[0246] <Example 7> Example 7 was carried out according to the flow sheet of FIG.

[0247] copper leaching process The copper leaching process was carried out as part of the bulk copper leaching described in Example 5. A portion of the leach residue was then used in the gold leaching process.

[0248] gold leaching process The residue from the copper leaching process was carried out in the same manner as the gold leaching process of Example 5. However, the thiourea concentration was 1.25 g / L. All other test conditions were as described in Example 5.

[0249] <Example 8> gold leaching process Example 8 was carried out similarly to Example 2, except that the ore was crushed ore type B and the leaching period was only 6 days. All other steps were similar, except for one additional washing step which involved washing with thiourea in an acidic solution at pH 1.5 prior to the acid washing step.

[0250] copper leaching process 100 g of the residue from the gold leaching process was divided and used in the copper leaching process, targeting a slurry density of 10%. A low sulfate leach solution of the following composition was used: [Table 6]

[0251] The test used a hot plate and was maintained at 60°C with a pH target of 1.2. The test used a jacketed reactor and was maintained at 60°C with a pH target of 1.2 and no Eh target. A bacterial inoculum was also introduced at the start of the copper leaching process. As with the other examples, samples were taken at predetermined times to follow the rate of Cu extraction.

[0252] <Result> Ore Type A Testing - Gold Leaching First, Copper Leaching Second Gold Leaching Results [Table 7]

[0253] Gold extraction was calculated as the percentage of soluble gold (i.e., cyanide-soluble gold) extracted by thiourea leaching.

[0254] Gold leaching results show that in the presence of 5 g / L thiourea, maximum Au extraction occurred at 64% (Example 2). At 2.5 g / L (Example 3) and 1.25 g / L (Example 4) thiourea, gold extraction was 27% and 35%, respectively.

[0255] Copper Leaching Results The copper leaching results for Examples 2 to 4 are summarized in FIG.

[0256] The figure is a graph of copper extraction versus time.

[0257] The graph includes a line for day 30, which indicates when ferrous oxidizing microorganisms and sulfur oxidizing microorganisms were added to the leaching of each example.

[0258] The graph shows that 65%-70% of the Cu in the feedstock was leached in the Cu leaching processes of Examples 2-4 under the conditions tested.

[0259] These results indicate that the Au leaching step before Cu leaching does not hinder Cu extraction and good Cu extraction can be achieved.

[0260] The copper extraction process can be further optimized as previously shown by the applicant in the above-mentioned patent specifications of international applications PCT / AU2016 / 051024 (Patent Document 1), PCT / AU2018 / 050316 (Patent Document 2) and PCT / AU2019 / 050383 (Patent Document 3).

[0261] Ore Type A Testing - Copper Leaching First, Then Gold Leaching Copper Leaching Results Bulk copper leaching was carried out as described for Examples 5, 6, and 7, and the bulk leaching residue was then used in the Au leaching tests described in Examples 5-7.

[0262] FIG. 6 is a graph of copper extraction versus time.

[0263] The graph includes a line for day 23, which indicates when bacteria was added to the leach of each example.

[0264] The graph shows that 65% of the Cu in the feedstock was leached in a 37 day bulk Cu leaching process under the conditions tested.

[0265] The copper extraction process can be optimized as previously shown by the applicant in the above-mentioned patent specifications of international applications PCT / AU2016 / 051024 (Patent Document 1), PCT / AU2018 / 050316 (Patent Document 2) and PCT / AU2019 / 050383 (Patent Document 3).

[0266] Gold Leaching Results Leaching of the residue from the copper leaching process of Examples 5-7 showed that gold could still be significantly extracted from the residue.

[0267] For example, based on the leaching solution data, it was found that the best extraction was obtained within 48 hours.

[0268] The leaching results show that high gold extraction was obtained when copper was leached first, as shown by the higher gold extraction values ​​for Examples 5, 6, and 7 (see table below) compared to Examples 2, 3, and 4 (see table above).

[0269] Referring to the table below, 86% of the soluble gold was extracted in the presence of 5 g / L thiourea in Example 5. Similarly, 90% and 73% of the gold was extracted in Example 6 (2.5 g / L thiourea) and Example 7 (1.25 g / L thiourea), respectively.

[0270] The high extraction yield is probably due to some of the gold being present in the chalcopyrite and / or pyrite crystal lattice. Such gold is commonly referred to as refractory gold, or "invisible gold". When the copper leaching step is first performed, distortion of the chalcopyrite / pyrite crystal lattice occurs. This creates voids (or pathways) for the gold leaching agent to reach the remaining gold and cause its dissolution. This process is not possible if the chalcopyrite and / or pyrite lattice is still intact. In such cases, if the ore is porous or crushed fine enough that the gold is exposed to the leaching agent, usually only a small portion of the gold is available for leaching. Importantly, complete destruction of the gold-holding sulfide minerals is not necessarily required to release the majority of the gold for subsequent dissolution by the gold leaching agent.

[0271] Before leaching the copper leach residue, it is advisable to wash the residue thoroughly. This is because the copper present in the solution will consume the thiourea reagent. Copper forms a copper-thiourea complex, which means that there may be less thiourea available for gold leaching. Applicant managed to wash the copper thoroughly to prevent copper interference with the gold leaching. It should be noted that such thorough washing / rinsing is not really practical in heap leaching, as some of the dissolved copper will always remain in the heap. Therefore, in practice, for heap leaching, some rinsing is preferred, if practical. [Table 8]

[0272] Ore Type B Testing - Au Leach First, Then Cu Leach - Example 8 FIG. 7 is a graph of gold extraction versus time for ore type B in Example 8.

[0273] The graph shows that nearly 30% of the gold was extracted within three days.

[0274] The residue from the Au leaching test was subjected to copper leaching as previously described.

[0275] FIG. 8 is a graph of copper extraction versus time.

[0276] The graph shows that nearly 100% of the copper was extracted within 60 days.

[0277] These results indicate that additional value can be extracted from the ore by first leaching the gold, followed by the copper.

[0278] The copper leaching process was not affected by the gold extraction process.

[0279] Many modifications can be made to the above-described embodiments of the invention without departing from the spirit and scope of the invention.

[0280] By way of example, the embodiment described in relation to Figures 1 and 2 includes a gold heap leaching operation 3 on the ore fragments followed by a copper leaching operation 5 on the agglomerate of gold-depleted ore 41, however the invention is not so limited and extends to forming a single heap of ore fragments or an agglomerate of ore fragments and carrying out gold and copper leaching steps on the material in succession, with washing steps between the steps.

[0281] By way of example, the embodiments described in relation to Figures 1-3 relate to gold / copper bearing ores, however the invention is not so limited and extends generally to gold / copper bearing materials including materials classified as waste.

[0282] By way of example, the present invention extends to the leaching of any one or more of gold / copper bearing ore concentrates and ore or concentrate tailings produced, for example, by flotation or other downstream processing of the ore or concentrate.

[0283] By way of example, the invention extends to the leaching of agglomerates of fragments of gold / copper bearing material.

[0284] By way of example, the embodiments described in relation to Figures 1-3 relate to gold and copper leaching, however the invention is not so limited and extends to the leaching of gold, copper and other valuable metals (e.g. silver) from mined materials.

[0285] By way of example, the embodiments described in connection with Figures 1-3 and the Examples include the use of certain additives, but the invention is not limited thereto. For example, if the pyrite concentrate added to the agglomerate contains refractory gold (i.e., the gold is trapped in the pyrite and not significantly contained in the copper sulfide minerals contained in the concentrate), it may be advantageous to first leach the copper, thereby oxidizing the pyrite and liberating the gold, which can then be recovered in a subsequent gold leaching step.

Claims

1. A method for leaching gold / copper-containing sulfide mining materials, A thiourea-based gold leaching step in which gold is leached from the material using a gold leaching solution, A copper leaching step is performed in which copper is leached from the material using a copper leaching solution and with the help of microorganisms. A leaching method comprising two heap leaching steps, having [a specific characteristic].

2. The method according to claim 1, wherein in the gold leaching stage, leaching conditions are selected such that substantially no copper is leached out.

3. The method according to claim 1 or 2, wherein in the copper leaching stage, leaching conditions are selected such that substantially no gold is leached out.

4. The method according to claim 1 or 2, comprising recovering gold and copper from the respective gold-containing solution and copper-containing solution from the leaching step, and a separate recovery step for producing a stream of recovered gold and copper and recovered gold-containing and copper-containing solutions.

5. The method described above is: (a) The gold leaching step includes leaching gold from the material using the gold leaching solution to produce a gold-containing solution and a gold-deficient ore, (b) The copper leaching step includes leaching copper from the gold-deficient ore using the copper leaching solution to produce a copper-containing solution. The method according to claim 1 or 2, including the method according to claim 1 or 2.

6. The method described above is: (a) The copper leaching step includes leaching copper from the material using the copper leaching solution to produce a copper-containing solution and a copper-deficient ore, (b) The gold leaching step, which includes leaching gold from the copper-deficient ore using the gold leaching solution to produce a gold-containing solution The method according to claim 1 or 2, including the method according to claim 1 or 2.

7. The method according to claim 5, comprising forming a heap of the material and successively performing the gold leaching step and the copper leaching step on the ore in the heap.

8. The method according to claim 6, comprising forming a heap of the material and successively performing the copper leaching step and the gold leaching step on the ore in the heap.

9. The method according to claim 5, further comprising a heap washing step between consecutive gold leaching and copper leaching steps.

10. The method according to claim 1 or 2, comprising performing the gold leaching step under ambient temperature conditions.

11. The method according to claim 1 or 2, comprising carrying out the gold leaching step under acidic conditions.

12. In the gold leaching step, thiourea (CS(NH ２ ) ２ The method according to claim 1 or 2, wherein the substance acts as a gold complexing / extracting agent that promotes the leaching of gold from the material.

13. The method according to claim 1 or 2, further comprising controlling the concentration of ferric in the gold leaching solution so that copper does not leach out during the gold leaching step.

14. The method according to claim 1 or 2, comprising performing the copper leaching step under acidic conditions.

15. The method according to claim 1 or 2, wherein the copper leaching step includes providing silver as a copper leaching catalyst at a concentration of less than 2 g of silver per 1 kg of copper.

16. The method according to claim 1 or 2, wherein the copper leaching step is carried out using the copper leaching solution in the presence of silver and an activator that activates the silver so that the silver promotes the leaching of copper.

17. The method according to claim 1 or 2, comprising controlling the heap temperature to less than 75°C in the copper leaching step.

18. The method according to claim 1 or 2, comprising controlling the pH of the leaching solution to less than 3.2 in the copper leaching step.

19. A leaching operation for leaching gold / copper-containing sulfide mining material, (a) A thiourea-based gold leaching unit operation, in which gold is leached from the material using a gold leaching solution to produce a gold-containing solution, and gold is recovered from the solution, (b) A copper leaching unit operation, in which copper is leached from the material using a copper leaching solution and with the help of microorganisms to produce a copper-containing solution, and copper is recovered from the solution, A leaching operation, including the leaching process.

20. A heap leaching operation for leaching gold / copper-containing sulfide mining material, (a) a heap of aggregated fragments of mining material and / or mining ore, (b) A leaching supply unit that supplies a gold leaching solution to the heap in order to carry out a thiourea-based gold leaching step on the material in the heap, (c) A leachate supply unit that supplies copper leachate to the heap in order to carry out a copper leaching step with the help of microorganisms against the material in the heap, (d) A gold recovery unit that recovers gold from the gold-containing solution discharged from the heap during the gold leaching step, and generates a recovered gold stream and a recovered gold-containing solution, (e) A copper recovery unit for recovering copper from the copper-containing solution discharged from the heap during the copper leaching process, and for generating a recovered copper stream and a recovered copper-containing solution, Heap leaching operations, including those mentioned above.

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