Leaching copper-containing ores

Abstract

The invention relates to leaching copper-containing ores. A method of leaching copper-containing ores, such as chalcopyrite ores, with a leach liquor in the presence of silver and an activator that activates the silver whereby the silver enhances copper extraction from the copper ores. The application makes it possible to achieve higher copper recovery from chalcopyrite (and other copper-containing minerals) in the form of ore fragments.

Description

[0001] This application is a divisional application of an application with an application date of April 6, 2018, application number 201880034761.5, and invention name “Leaching of copper-containing ore”. Technical Field

[0002] The present invention relates to the leaching of copper-containing ores and concentrates of copper-containing ores.

[0003] The present invention relates to heap leaching, vat leaching and tank leaching of copper-containing ores. The ore may be in the form of fragments. The ore may be in the form of agglomerates of the fragments.

[0004] The present invention relates to heap, vat and tank leaching of concentrates of copper-containing ores.The ore concentrates may be in any suitable form, including unagglomerated and agglomerated forms.

[0005] The present invention particularly, but not exclusively, relates to a chalcopyrite (CuFeS 2 ) are hereinafter referred to as "chalcopyrite ore" and "chalcopyrite ore concentrate", respectively. The chalcopyrite ore and the chalcopyrite ore concentrate may contain other copper minerals.

[0006] The present invention particularly, but not exclusively, relates to a method of heap leaching agglomerates of fragments of chalcopyrite ore.

[0007] The present invention particularly, but not exclusively, relates to a method of bioleaching agglomerates of fragments of chalcopyrite ore in a heap via the use of microorganisms. Background Art

[0008] In conventional heap leaching of copper sulfide-containing minerals, including chalcopyrite ore, the mined ore is piled into a heap, aerated by direct injection of air through an aeration pipe extending into the heap and / or by natural convection of exposed areas of the heap, and flushed with an acidic solution for extracting copper into solution. Copper is then recovered from the acid solution by a range 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 through the heap to leach more copper from the ore in the heap. The ore in the heap may include agglomerates of fragments of the ore. Leaching may be assisted by the addition of ferrous and sulfur-oxidizing microorganisms.

[0009] Typically, heap and dump leaching (hereinafter collectively referred to as "heap leaching") provides lower metal recoveries than other metallurgical process options for recovering copper from copper-bearing ores, such as grinding and flotation, which produces a copper-bearing concentrate that is then smelted to produce metallic copper.

[0010] Heap leaching therefore tends to be reserved for lower grade ore types which have at least some readily recoverable copper, but where the crushing / grinding costs per unit of copper (or copper equivalent - i.e. when by-product credits from, for example, gold and silver are taken into account) are too high to support a concentrator approach, or where mineral release and other characteristics (e.g. arsenic content) will not support the production of a directly usable or saleable concentrate.

[0011] Standard best industry practice is to use agglomerates of mined and subsequently crushed ore fragments in a heap. Typically, the mined ore is processed through a number of crushing steps, namely a primary crushing step and a secondary crushing step, and in some cases a tertiary crushing step, and the crushed ore fragments are agglomerated in an agglomeration step, typically using an acid.

[0012] It is well known that it is difficult to extract more than 20-40 wt.% of total copper from chalcopyrite by heap leaching. The low copper recovery is generally believed to be related to the formation of a passive film on the surface of chalcopyrite.

[0013] International application PCT / AU2016 / 051024 in the name of the applicant relates to leaching chalcopyrite ore (and other copper-containing ores). The disclosure in this international application is incorporated herein by cross-reference.

[0014] An important focus of this international application is heap leaching of fragments or agglomerates of fragments of chalcopyrite ore.

[0015] This international application describes and claims an invention based on the discovery by the applicant, through a group of companies of the applicant, that high recoveries of copper (greater than 60 wt. % of total copper) can be achieved by leaching agglomerates of: (a) fragments of chalcopyrite ore (and other copper-bearing ores) and (b) silver.

[0016] The International application describes that agglomerates may be formed by adding silver (a) to mined ore fragments prior to or during agglomeration of the ore fragments, or (b) to already formed agglomerates of ore fragments.

[0017] In particular, as reported in the international application, the applicants have found that the low concentration of silver dispersed on the surface of the chalcopyrite in the agglomerates, typically less than 2 g of silver per kg of copper in the chalcopyrite ore, enables higher copper recoveries (greater than 60 wt.%) from the ore to be achieved in shorter leaching times than when leaching agglomerates without silver dispersed in the agglomerates. This is an important finding, particularly in the context of leaching lower grade chalcopyrite ores, i.e. ores containing less than 1.5 wt.% copper, typically less than 1.25 wt.% copper, and typically less than 1 wt.% copper, and typically less than 0.5 wt.% copper. This is also an important finding in the context of leaching other lower grade copper-containing ores.

[0018] The above description should not be taken as an admission of common general knowledge in Australia or elsewhere. Overview of public content

[0019] The invention particularly relates to leaching mined and crushed and agglomerated ore fragments containing chalcopyrite.

[0020] The present invention was made in the course of further research and development work related to the invention of international application PCT / AU2016 / 051024.

[0021] The present invention enables higher copper recoveries to be achieved from chalcopyrite (and other copper-bearing minerals) in the form of ore fragments.

[0022] Testwork carried out by the applicant's group of companies has shown that various activators, including for example complexing agents, can be used to activate silver in or added to chalcopyrite ore and thereby enhance the catalytic effect of silver in the leaching of chalcopyrite.

[0023] In particular, test work has shown that chloride has a synergistic effect with silver in enhancing copper extraction from chalcopyrite-containing copper ores.

[0024] The same synergistic effect applies to the extraction of copper from concentrates of chalcopyrite-containing copper ores.

[0025] The same synergistic effect is expected to apply to other halides, such as iodide and bromide, due to the complexing behavior of halides.

[0026] Another agent which has been shown in the applicant's test work to increase chalcopyrite extraction by activation of silver is thiourea. It is expected that other complexing agents, particularly other sulfur-containing ligands, will have the same effect.

[0027] Applicants believe that activation occurs via agents that (a) move silver to the chalcopyrite surface and / or (b) enhance the reactivity of silver on the chalcopyrite surface.

[0028] More particularly, the applicant has found in column and stirred reactor leach tests in further research and development work that good leaching results for (a) fragments of chalcopyrite ore and (b) agglomerates of silver are obtained using leachates containing low concentrations of chloride in the leachate, typically 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, more typically up to 1 g / L.

[0029] These results are obtained with lower grade chalcopyrite ores, ie ores containing less than 1.5 wt.%, typically less than 1.25 wt.%, typically less than 1 wt.% copper and typically less than 0.5 wt.% copper.

[0030] The synergistic effect of chloride and silver is contrary to applicant's expectations and the teachings of the literature.

[0031] Based on the literature, applicants had expected to find that chloride in the leachate would tend to precipitate the silver as silver chloride before the silver or chloride had a chance to function beneficially in the leaching system.

[0032] For example, International Patent Publication WO 00 / 37690 (UBC) reports that when chloride is present in the leachate, thiosulfate can be added to inhibit precipitation of silver as silver chloride. For example, page 6, lines 7-10 of WO 00 / 37690 states "....the present invention recognizes that delivery of catalytic amounts of silver to the ore may be facilitated, where there is chloride in the silver solution, by adding a thiosulfate, such as ammonium thiosulfate, to the silver solution in an amount effective to inhibit the precipitation of the soluble silver as silver chloride (the present invention recognizes that in the presence of chloride in the silver solution, by adding a thiosulfate, such as ammonium thiosulfate, to the silver solution in an amount effective to inhibit the precipitation of the soluble silver as silver chloride, the delivery of catalytic amounts of silver to the ore can be facilitated)". In addition, WO 00 / 37690 states on page 16, lines 17-19, "Examples 28-30 (PVD ore) and 32-34 (K ore) demonstrate that the addition of thiosulfate to a silver solution can counteract the effect of the presence of chloride ions in the solution, ie counteract the precipitation of silver chloride." Examples 28-30 were conducted with KCl as part of the nutrient medium, wherein KCl was present in an amount of 0.15 g / 15 L of medium. In summary, the disclosure in WO 00 / 37690 indicates that chlorides can be detrimental to the use of silver in leaching fragments of chalcopyrite ore (and ores containing other copper-containing minerals).

[0033] By way of further example, Munoz, JA et al., "Silver catalyzed bioleaching of low-grade copper ores," Part II: Stirred Tank Tests. Hydrometallurgy Vol. 88, 2007, pp. 19-34, discloses that the benefits of silver addition on copper extraction are inhibited when 5 g / L Cl is present in solution in the leachate.

[0034] The synergistic effects described above apply to heap, vat and tank leaching of copper-bearing ores in the form of fragments or in the form of agglomerates of fragments.

[0035] The synergistic effects described above also apply to heap, vat and tank leaching of concentrates containing copper ores.The ore concentrate may be in any suitable form, including unagglomerated and agglomerated forms.

[0036] Generally speaking, the present invention provides a method of leaching a copper-containing ore, such as chalcopyrite ore, with a leachate in the presence of silver and an activator that activates the silver such that the silver enhances the extraction of copper from the copper ore.

[0037] In general, the present invention also provides a method of leaching a concentrate of a copper-containing ore, such as chalcopyrite ore, with a leachate in the presence of silver and an activator which activates the silver, whereby the silver enhances the extraction of copper from the copper ore concentrate.

[0038] The method may include any of the following: (a) Heap or barrel or tank leaching of ore fragments, (b) agglomerates of ore fragments from heap or vat or tank leaching, (c) heap or drum or tank leaching of ore concentrates, and (d) Agglomerates of ore concentrates obtained by heap or barrel or tank leaching.

[0039] The present invention provides a method for leaching a copper-containing ore (such as chalcopyrite ore) and a concentrate of the ore, wherein the method comprises leaching the copper-containing ore or a concentrate of the ore with a leachate in the presence of silver and an activator in a heap or in a reactor such as a vat or tank, wherein the activator activates the silver so that the silver enhances copper extraction.

[0040] The activating agent may be any suitable agent that can activate silver such that the silver enhances the extraction of copper from chalcopyrite-containing copper ores and ore concentrates.

[0041] The activator may be any one or more than one silver complexing ligands such as chloride, iodide, bromide and thiourea.

[0042] Although iron is essential to the leaching process, both in the form of pyrite to generate heat and in the form of iron ions that oxidize sulfide minerals in the ore, neither pyrite nor iron ions are considered "activators" in the context of the present invention.

[0043] The activating agent may be present in the process by being sprayed or otherwise distributed 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 a leachate.

[0044] When an activating agent is present in the process as a component of the leachate, the process may comprise providing a selected concentration or range of concentrations of the activating agent in the leachate.

[0045] The selected concentration or concentration range of the activating agent in the leachate may be the result of any one or more of the following positive steps: (a) adding an activating agent to the extract; (b) removing the activating agent from the leachate; (c) adding an activating agent during the agglomeration step; (d) blending of different ore types taking into account soluble activators in the ore; (e) selection and blending / mixing of water source / type with respect to activator concentration in the ore (e.g. use of seawater); (f) Other human intervention in one or more inputs to the leaching process which may affect the concentration of the soluble activating agent in the leaching process.

[0046] The selected concentration or concentration range of the activator may be different from the background concentration of the activator in the leachate, chalcopyrite ore or concentrate. The present invention requires an assessment of the desired concentration or concentration range of the activator for a given ore or concentrate, and an assessment of the available water sources and associated conditions and control of the process, e.g. taking into account steps (a) to (e) above, such that the desired concentration or concentration range of the activator is present.

[0047] The method may include monitoring the concentration of any one or more than one silver complexing ligands such as chloride, iodide, bromide and thiourea.

[0048] The term "chalcopyrite ore" is understood herein to mean an ore containing chalcopyrite. The ore may also contain other copper-containing minerals. The ore may also contain pyrite.

[0049] The term "chips" is understood herein to mean mined or processed (e.g., pulverized) material of any suitable size taking into account the material handling and processing capabilities of the equipment used to implement the method. It should also be noted that the term "chips" as used herein may be understood by some skilled in the art to be better described as "particles". The intention is to use the two terms as synonyms.

[0050] The term "ore concentrate" is understood herein to mean ore in any concentrated form formed by any suitable option, such as flotation, or otherwise on ore beneficiation.

[0051] The term "mined" ore is understood herein to include, but is not limited to, (a) run-of-mine material and (b) run-of-mine material that has undergone at least one stage of crushing or similar or further size reduction after the run-of-mine material has been mined. The term "mined" ore also includes mined material in stockpile.

[0052] The leaching step may be carried out in the presence of a low concentration or range of concentrations of an activating agent selected from any one or more than one silver complexing ligands such as chloride, iodide, bromide and thiourea.

[0053] The meaning of the term "low concentration" in relation to chlorides, iodides, bromides, thioureas and other silver complexing ligands in any given case will depend on a number of factors, including the mineralogy of the ore, the physical characteristics of the ore fragments such as fragment size and particle size distribution, the characteristics of the agglomerates such as size and porosity, the copper concentration in the ore, the silver concentration (both native in the ore fragments and added as part of the agglomerates), the composition of the leachate, and, in the case of heap leaching, the characteristics of the heap including heap porosity.

[0054] The low concentration 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, more typically up to 1.25 g / L, and more typically up to 1 g / L chloride in the leachate.

[0055] The 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.

[0056] The low concentrations for iodide and bromide can be the same as for chloride.

[0057] The low concentration of thiourea can be less than 10 g / L in the extract.

[0058] Typically, the leachate solution need not contain thiosulfate or other additives to inhibit the precipitation of silver chloride, iodide or bromide.

[0059] The leachate may include microorganisms to assist in the leaching of the copper.

[0060] The microorganism may be one or more than one of a mesophilic or thermophilic (moderate or extreme) bacterium or archaea. The microorganism may be an acidophilic bacterium or archaea. The microorganism may be a thermoacidophile.

[0061] The method may include adding an activating agent to the leachate continuously or periodically during the course of the method to maintain a desired concentration during the method.

[0062] In the case where the process recycles (optionally after regeneration) the leachate from the leaching step, the process may comprise adjusting the concentration of the activating agent in the regenerated leachate to maintain the concentration.

[0063] Leaching may be any suitable option for leaching the agglomerates.

[0064] For example, the leaching may be a vat leaching or a tank leaching.

[0065] By way of further example of particular interest to the applicant, the leaching may be heap leaching.

[0066] Heap leaching may include supplying a leachate to a heap of agglomerates from the agglomeration step, and allowing the leachate to flow through the heap and leach copper from the agglomerates, and collecting the leachate from the heap, processing the leachate and recovering copper from the leachate.

[0067] Heap leaching may include controlling the heap temperature to be below 85°C, typically below 75°C, typically below 65°C, typically below 60°C, typically below 55°C, typically below 50°C, and more typically below 45°C.

[0068] Heap leaching may include controlling the heap temperature to at least 5°C, typically at least 10°C, typically at least 20°C, typically at least 30°C, and more typically at least 40°C.

[0069] Heap leaching may include controlling the oxidation potential of the leachate to less than 900 mV, typically less than 850 mV, typically less than 700 mV, typically less than 660 mV, typically in the range of 600 mV-660 mV, more typically in the range of 630 mV-660 mV, all relative to a standard hydrogen electrode, during the active leaching stage of the step. It should be noted that the oxidation potential will vary during heap leaching and may be higher when most of the copper has been leached, and reference to an "active leaching stage" is intended to recognize such potential variation.

[0070] Heap leaching may include controlling the pH of the leachate to less than 3.2, typically less than 3.0, typically less than 2.5, typically less than 2.0, typically less than 1.8, typically less than 1.5, typically less than 1.2, and typically less than 1.0.

[0071] Heap leaching may involve controlling the pH of the leachate to be greater than 0.3, typically greater than 0.5.

[0072] Heap leaching may include recovery of copper from the leachate in a downstream copper recovery step.

[0073] The leachate may be regenerated and recycled to the heap.

[0074] Heap leaching may include adjusting the concentration of the activating agent in the regenerated leachate to maintain the concentration.

[0075] Concentration adjustment may include adding an activator to the regenerated leachate to maintain the concentration.

[0076] Concentration adjustment may include removing activating agent from the regenerated leachate to maintain the concentration.

[0077] Concentration adjustment may include removing degradation / decomposition products from the regenerated leachate to maintain the concentration.

[0078] The ore may include a copper-containing ore having naturally occurring silver. The naturally occurring silver in the copper-containing ore may or may not have catalytic properties for copper leaching. The naturally occurring silver in the copper-containing ore may be in one or more of a variety of forms, including, but not limited to, native silver, argentite (Ag 2 S), silver chloride (AgCl); as a silver inclusion compound in copper minerals and pyrite; and as a silver sulfosalt, such as tetrahedrite (Cu,Fe,Zn,Ag 12 Sb 4 S 13 ), Ag 3 Sb 3 ) and Ag( 3 AsS3 ).

[0079] In the presence of naturally occurring silver that has catalytic properties for copper leaching, the operator may take this into account and choose a lower concentration of added silver than would otherwise be the case. By way of example, it may not be necessary to add any silver.

[0080] In the case of chalcopyrite ore, the invention involves dispersing silver in a certain form and within a defined concentration range on the surface of the chalcopyrite.

[0081] Typically, the defined concentration range is less than 2 g Ag / kg Cu.

[0082] Agglomeration may include forming agglomerates by mixing the ore fragments and the silver together in an agglomeration step.

[0083] Agglomeration may include forming agglomerates by adding silver to the ore fragments in an agglomeration step and then mixing the ore fragments together.

[0084] Agglomeration may include forming agglomerates of the ore fragments in an agglomeration step and then adding silver to the agglomerates.

[0085] Agglomerates formed during agglomeration may have a low overall silver concentration.

[0086] As mentioned above, the fragments in the agglomerate may already have a naturally occurring low silver concentration prior to the addition of silver in the agglomeration, and some or all of the naturally occurring silver may or may not have catalytic properties for copper leaching. In practice, this is a factor to be considered when determining the amount of silver added during agglomeration so that the overall active silver concentration remains within the desired concentration range. To distinguish between the naturally occurring silver concentration in the chalcopyrite ore and the silver added during the agglomeration step, the added silver is hereinafter referred to as "added silver" or similar terminology.

[0087] Added silver and total silver concentrations in agglomerates are expressed herein as g silver per kg copper in ore in the agglomerates. The concentration of added silver required to achieve a selected agglomerate silver concentration (naturally occurring and added) in the agglomerates can be readily determined by a skilled artisan. Furthermore, it is recognized that different measures of silver concentration exist in the patent and non-patent literature, and that comparisons of the different ranges disclosed in the literature can be challenging.

[0088] The added silver concentration in the agglomerates may be less than 5 g silver per kg copper in the ore in the agglomerates.

[0089] The added silver concentration in the agglomerates may be less than 2 g silver per kg copper in the ore in the agglomerates.

[0090] The added silver concentration in the agglomerates may be less than 1 g silver per kg copper in the ore in the agglomerates.

[0091] The added silver concentration in the agglomerates may be less than 0.5 g silver per kg copper in the ore in the agglomerates.

[0092] The added silver concentration in the agglomerates may be greater than 0.02 g silver per kg copper in the ore in the agglomerates.

[0093] The added silver concentration in the agglomerates may be greater than 0.05 g silver per kg copper in the ore in the agglomerates.

[0094] The added silver concentration in the agglomerates may be greater than 0.1 g silver per kg copper in the ore in the agglomerates.

[0095] The added silver concentration in the agglomerates may be greater than 0.2 g silver per kg copper in the ore in the agglomerates.

[0096] Agglomeration may comprise adding silver to the chalcopyrite ore fragments by any suitable means and in any suitable form.

[0097] The added silver may be in solid form.

[0098] The added silver may be in soluble form.

[0099] The added silver may be in solution.

[0100] The added silver may be in an aqueous solution.

[0101] The added silver may be in a solid form which becomes mobile when dissolved with the leachate. It may precipitate or otherwise be deposited on the chalcopyrite surface.

[0102] The added silver may be in an insoluble form or in a slightly soluble form, such as silver sulfate or silver chloride or silver sulfide. The term "slightly soluble" is understood herein to mean a salt having a solubility of less than 0.05 mol / l.

[0103] Typically, the added silver is added to the ore fragments while the ore fragments are being mixed together.

[0104] Agglomeration may include dispersing the added silver on the surface of the chalcopyrite in the chalcopyrite ore fragments.

[0105] Agglomeration may include dispersing the added silver within the chalcopyrite ore fragments.

[0106] Agglomeration may involve adding silver to the chalcopyrite ore fragments in the form of an aerosol, wherein the term "aerosol" is understood to mean a colloidal suspension of particles, typically in powder form, in air or a gas.

[0107] Agglomeration may involve adding silver in solution to the chalcopyrite ore fragments in the form of a mist or spray, wherein the terms "mist" and "spray" are understood to mean small droplets of silver solution suspended in air.

[0108] Typically, agglomeration may involve adding silver in the form of a mist or spray or aerosol to the chalcopyrite ore fragments while the ore fragments are being mixed.

[0109] Agglomeration may involve adding an activating agent to the ore fragments in solid or liquid form.

[0110] Agglomeration may include forming agglomerates by mixing an acid, typically sulfuric acid, but also dilute hydrochloric acid, with the chalcopyrite ore fragments and silver. The acid may be added simultaneously with the silver solution or before or after the silver solution. The dose rate of the added acid may be less than 100 kg H 2 SO 4 / dry ton of ore, typically less than 50 kg H 2 SO 4 Typically less than 30 kg H / dry tonne of ore 2 SO 4 / dry ton of ore, and can be less than 10kg H 2 SO 4 / dry ton of ore or less than 5 kg H 2 SO 4 / dry ton of ore. Typically, the acid dosage rate is 0.5-10 kg H 2 SO 4 / dry ton of ore.

[0111] Agglomeration may include forming agglomerates by also mixing a pregnant leach solution or raffinate with the chalcopyrite ore fragments and silver.

[0112] Agglomeration may include forming agglomerates by also mixing a microorganism that can assist in the leaching of copper with the chalcopyrite ore fragments and the silver. The microorganism may be added simultaneously with the silver solution or before the silver solution or after the silver solution. The microorganism may be as described above. In particular, the microorganism may be one or more than one of a mesophilic, thermophilic (moderate or extreme) or psychrophilic bacteria or archaea. The microorganism may be an acidophilic bacteria or archaea. The microorganism may be a thermoacidophile.

[0113] Agglomeration may include simultaneously mixing and agglomerating the fragments.

[0114] Agglomeration may comprise mixing the fragments in one step and then agglomerating the mixed fragments in a subsequent step. There may be overlap between the mixing step and the agglomeration step.

[0115] The fragments of chalcopyrite ore may include fractures to facilitate dispersion of the silver solution with the fragments.

[0116] The method may include reducing the size of the mined ore prior to agglomeration.

[0117] By way of example, the method may comprise comminuting the mined ore prior to agglomeration.The mined ore may be comminuted using any suitable means.

[0118] The method may comprise comminuting the mined ore in a primary comminution step prior to agglomeration.

[0119] The term "primary comminution" is understood herein to mean comminuting the ore to a maximum size of 250 mm to 150 mm in the case of copper-containing ores in which the copper is in the form of sulphides. It should be noted that the maximum size may be different for ores containing different valuable metals.

[0120] The method may comprise comminuting the mined ore in a primary comminuting step and then in a secondary comminuting step and possibly a tertiary comminuting step and possibly a quaternary comminuting step prior to agglomeration.

[0121] The present invention also provides a pile of material, wherein the material comprises agglomerates as described above.

[0122] The present invention also includes a heap leaching method comprising: (a) forming a pile of material, wherein the material comprises agglomerates as described above; and (b) leaching valuable metals from the ore in the heap with a leachate containing an activator which activates the silver, whereby the silver enhances the extraction of copper from the chalcopyrite-containing copper ore.

[0123] Heap leaching may include recovery of copper from the leachate in a downstream copper recovery step.

[0124] The leachate may be regenerated and recycled to the heap.

[0125] Heap leaching may include adjusting the concentration of the activating agent in the regenerated leachate to maintain the concentration.

[0126] Concentration adjustment may include adding an activator to the regenerated leachate to maintain the concentration.

[0127] Concentration adjustment may include removing activating agent from the regenerated leachate to maintain the concentration.

[0128] The method may further comprise recovering the leached metal as a metal product. Typically, this step comprises recovering the leached metal from the solution of the enriched leachate.

[0129] The method may comprise forming a heap of the copper-bearing ore or concentrate without mixing the ore or concentrate with further particulate or agglomerated feed material, such as pyrite.

[0130] The present invention also provides a method for leaching a copper-containing ore, wherein the copper-containing ore is, for example, chalcopyrite ore, the method comprising: (a) crushing the mined copper-bearing ore in a crusher and forming fragments; (b) forming agglomerates of the ore fragments, silver, acid and optionally microorganisms in an agglomeration station; (c) forming a pile of said agglomerates; (d) supplying a leachate to the heap and collecting the leachate after the leachate has passed through the heap, wherein the leachate leaches copper from the ore fragments as the leachate passes through the heap; (e) recovering copper from the leachate; and (f) regenerating and recycling the regenerated leachate to the heap; And the method is characterized by leaching copper from the fragments in the heap in the presence of an activating agent, which activates silver, whereby the silver enhances copper extraction.

[0131] The method may comprise providing a low concentration of an activating agent to the leachate.

[0132] The method can include forming agglomerates with an activating agent.

[0133] Generally speaking, the advantages of the present invention provide the opportunity for microbially assisted heap leaching of silver-containing agglomerates of chalcopyrite ore fragments, especially fragments of low grade ores (i.e., less than 1.5 wt. % copper), at relatively low heap temperatures with high recoveries at relatively low operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0134] The present invention is further described with reference to the accompanying drawings, in which: Figure 1 The figure shows the steps in one embodiment of a method for heap leaching fragments of chalcopyrite ore and agglomerates of silver with a leachate containing an activator, including any one or more than one of chloride, iodide, bromide, thiourea and other silver complexing ligands, to activate or mobilize silver according to the present invention; Figure 2is a graph depicting a copper extraction profile for a chalcopyrite containing ore for copper leach extraction with chloride addition and / or silver addition; and Figure 3 and Figure 4 is a graph showing the copper extraction profile for a chalcopyrite containing ore for copper leach extraction with thiourea and / or silver addition. Description of the implementation plan

[0135] The following description is in the context of heap leaching agglomerates of copper-containing ore fragments, wherein an activator is added to the leachate. However, it should be noted that the present invention extends to barrel leaching and tank leaching of copper-containing ores in the form of fragments or in the form of agglomerates of fragments. It should also be noted that the present invention also extends to heap leaching, barrel leaching and tank leaching of concentrates of copper-containing ores, wherein the ore concentrate is in any suitable form, including unagglomerated form and agglomerated form. It should also be noted that the activator can be present in the method by any suitable option, and the present invention is not limited to adding the activator to the leachate. By way of example, the activator can be added in the agglomeration step. By way of example, the activator can be sprayed or otherwise distributed on the ore fragments or ore concentrate in liquid form.

[0136] Reference Figure 1 , the following feed materials are transferred to agglomeration station 3 and agglomerated as described below: (a) fragments of chalcopyrite ore which have been crushed to a suitable particle size distribution, identified in the accompanying drawings by the number 7; (b) silver, in this embodiment as a silver solution (but may be in solid form), typically having an added concentration of less than 5 g silver per kg copper in the ore in the agglomerate, identified in the accompanying drawings by the number 9; (c) an acid, typically sulfuric acid, in any suitable concentration, indicated in the accompanying drawings by the numeral 11; (d) microorganisms, identified in the accompanying drawings by numeral 13, of any suitable type and in any suitable concentration; and (e) Optionally, an activator, such as a silver complexing ligand, including chlorides, iodides, bromides and thioureas, identified by numeral 15 in the Figure.

[0137] The agglomerates produced in the agglomeration station 3 are subsequently used for the construction of a pile 5 .

[0138] Agglomerates produced in the agglomeration station 3 can be directly transferred to the pile building position. Alternatively, the agglomerates can be stored and used according to the needs of the pile. The agglomeration station 3 and the pile 5 can be in close proximity. However, likewise, the agglomeration station 3 and the pile 5 may not be in close proximity.

[0139] Figure 1 The method of agglomerating mined ore fragments illustrated in the drawings is suitable for forming agglomerates that can be used in a standard heap. More particularly, the invention does not extend to a specific shape and size of the heap, and does not extend to a specific method of building a heap from agglomerates, and does not extend to specific operating steps of a heap leaching process for the heap.

[0140] By way of example only, the heap may be of the type described in International Publication WO 2012 / 031317 in the name of the applicant and the disclosure of the heap construction and leaching process of the heap in that International Publication is incorporated herein by cross reference.

[0141] In a heap leaching operation, copper in the chalcopyrite and other copper-containing minerals in the agglomerates are leached from the agglomerates in the heap 5 via supply of a leachate 23 containing any one or more activators, such as silver complexing ligands including chlorides, iodides, bromides and thioureas, at low concentrations to the leachate, typically 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, more typically up to 1 g / L.

[0142] As described above, silver complexing ligands such as chlorides, iodides, bromides, and thioureas mobilize silver to the chalcopyrite surface and / or enhance the reactivity of silver on the chalcopyrite surface.

[0143] The low concentration of any one or more than one silver complexing ligands such as chloride, iodide, bromide and thiourea may be the result of any one or more than one of the following active steps: (a) adding chloride, iodide, bromide and thiourea to the leachate as described above; (b) removing chloride, iodide, bromide and thiourea from the leachate; (c) adding chloride, iodide, bromide and thiourea in the agglomeration step as described above as an optional step; (d) Mixing of different ore types taking into account soluble chlorides, iodides, bromides, and thioureas in the ores; (e) Selection and blending / mixing of water sources / water types with respect to soluble chlorides, iodides, bromides and thioureas in the ore; (f) Other human intervention in one or more of the inputs to the heap leaching process which may affect the concentrations of soluble chloride, iodide, bromide and thiourea in the heap.

[0144] In a downstream copper recovery step 17, the leached copper is recovered from the leachate.

[0145] The recovered copper 19 is transferred for further processing and the leachate is regenerated in a regeneration loop 21 and recycled to the heap 5 with make-up leachate, as may be required for leachate 23 .

[0146] Chloride, iodide, bromide and thiourea may be added to the leachate 23 continuously or periodically to maintain the desired low concentrations in the leachate.

[0147] The method involves monitoring the concentrations of chloride, iodide, bromide and thiourea in the leachate 23 and adjusting the addition rate, as may be necessary, to maintain the desired low concentrations.

[0148] Agglomeration station 3 can be any suitable structure, and this structure includes for mixing the feed material for agglomerate and for making the feed material agglomerate drum, conveyor (or other device). Mixing and agglomeration of the feed material used for agglomerate can occur simultaneously.Selectively, can first mix the feed material, and can carry out agglomeration (for example, by adding acid to cause) after mixing has been completed to the desired degree.In addition, can select to add and then mix and make the time of agglomeration of feed material, to meet the end-use requirement for agglomerate.For example, in some cases, it is preferable to start mixing the fragments of chalcopyrite ore, and then gradually add silver in solution or silver, acid and microorganism in solid form in the order of silver, acid and microorganism at different start times and end times in the agglomeration step.By the way of specific example, in some cases, it is preferable to start mixing the fragments of chalcopyrite ore, and then add silver and acid in solution or in solid form together, and then add microorganism at different start times and end times in the agglomeration step.

[0149] As stated above, the applicant has: (a) column leach testing to investigate the effects of chloride and thiourea in the leachate on the bioleaching, i.e. microbiologically assisted leaching, of (a) chalcopyrite ore fragments and (b) silver agglomerates; and (b) Reactor leaching tests to investigate the effect of thiourea in the leachate on the leaching of (a) fragments of chalcopyrite ore and (b) agglomerates of silver.

[0150] Column leaching tests and reactor leaching tests are described in the Examples below.

[0151] 1 Overview As described above, test work carried out by the applicant's group of companies has shown that a variety of silver complexing agents, including chlorides and thioureas, can be used to activate silver (as that term is described above) in or added to chalcopyrite ore and thereby enhance the catalytic effect of silver in the leaching of chalcopyrite.

[0152] Test work has shown that chlorides act synergistically with silver in enhancing copper extraction from chalcopyrite-containing copper ores. This was an unexpected result since the literature suggests that chlorides in the leachate will actually tend to precipitate the silver as silver chloride and thereby reduce or eliminate the catalytic effect of the silver.

[0153] Test work has shown that thiourea is another agent that acts synergistically with silver in enhancing copper extraction from chalcopyrite-containing copper ores through activation of the silver.

[0154] It is expected that other complexing agents, particularly other sulfur-containing ligands and silver complexing ligands, will have the same effect.

[0155] Test work using chloride-containing and thiourea-containing liquids has been carried out in leaching columns. Test work with thiourea-containing liquids has been carried out in small-scale leaching stirred reactors.

[0156] 2-column test work 2.1 Experimental Procedure The ore samples were crushed to < 12 mm, where P 80 9 mm, and about 10 kg of this material was added to the agglomeration drum with water and concentrated acid. In tests with added silver, silver nitrate or silver sulfate was dissolved in the water used for agglomeration, and this was added as a mist that was sprayed onto the ore during agglomeration. After mixing, the agglomerated ore was loaded into a 1 m high, 0.1 m diameter column and allowed to solidify at room temperature for 2-5 days before leaching began. During leaching, the temperature of the column was controlled at 50°C using a heating jacket and the column was heated at 0.102 Nm 3 / h / t aeration. The column was inoculated with ferrous and sulfur oxidizing microorganisms. An irrigation solution initially containing about 15 g / L of ferric iron as ferric sulfate, 5 g / L to 7 g / L of aluminum as aluminum sulfate, and 0.1 g / L to 0.5 g / L of magnesium as magnesium sulfate was passed through a dripper at 10 L / h / m 2is pumped to the top of the column and collected at the bottom of the column. If necessary, the pH of the collected leach solution is adjusted to a target pH of 1.2 before being recycled back to the top of the column. If the solution copper concentration exceeds 8 g / L due to copper leaching, the solution is subjected to ion exchange to remove copper and reduce the solution copper concentration to maintain it at less than 8 g / L. At the beginning of leaching, the perfusate has a total sulfate concentration of between 20 g / L and 80 g / L. If the total sulfate concentration in the solution exceeds 120 g / L due to the addition of sulfuric acid as a result of leaching of gangue minerals or oxidation of sulfide minerals, the solution is diluted to maintain a maximum sulfate concentration of 120 g / L. When used, chloride sufficient to achieve a solution concentration of 1 g / L is added to the leach solution as lithium chloride, or thiourea sufficient to achieve a solution concentration of 1 g / L is added to the leach solution.

[0157] The composition of the ore used is shown in Table 1. Copper was present mainly as chalcopyrite. The ore contained 0.5 g Ag / kg Cu ​​as naturally occurring silver.

[0158] Table 1: Ore composition

[0159] 2.2 Effect of Chloride Addition on Silver— Figure 2 Figure 2 (Copper extraction with added chloride and / or added silver in column leach tests) shows the copper extraction profile obtained when the ore was leached at 50°C with a solution having an initial sulfate concentration of 80 g / L. The figure shows that the addition of 0.25 g Ag / kg Cu ​​(added to the ore during agglomeration, C296) and / or 1 g / L chloride (added to the leach solution, C335) significantly accelerated copper extraction compared to the control test (C274) in which neither silver nor chloride was added. However, after 100 days, the addition of both 0.25 g Ag / kg Cu ​​and 1 g / L chloride (C334) gave the highest copper extraction, with about 87% extraction after 100 days - compared to about 80%, 75% and 60% for chloride, silver and control, respectively, after the same period of time.

[0160] 3 Stirred Reactor Test Work— Figure 3 3.1 Experimental Procedure Stirred reactor tests were performed on ore samples that were crushed to -2 mm and agglomerated with 2 kg / t sulfuric acid and added silver (if used). The agglomerated ore samples were left to cure for two days before mixing with sufficient solution containing 80 g / L sulfate (liquid composition as described in Section 2.1) to obtain a 10% slurry. The slurry was stirred and maintained at 50°C in a water bath where pH and E h Controlled at 1.2 and 700 mV respectively.

[0161] In selected tests, thiourea was added to the leach slurry after two weeks of leaching in an amount sufficient to achieve a solution concentration of 1 g / L.

[0162] The ore samples used for these tests were the same as those in Table 1.

[0163] 3.2 Effect of thiourea on silver Figure 3 (Copper Extraction with Added Thiourea and / or Added Silver in Reactor Leach Tests) shows the copper extraction profile for copper leaching extraction with thiourea and / or silver addition over a 50 day period. Adding 1.0 g Ag / kg Cu ​​in the agglomerate significantly facilitated copper extraction (LR024) compared to a control test (LR029) in which neither silver nor thiourea was added. Adding 1 g / L thiourea after two weeks of leaching also facilitated copper extraction (LR028). The highest copper extraction was achieved when both 1.0 g Ag / kg Cu ​​of silver and 1 g / L of thiourea were added to the leaching (LR025) - about 98%, compared to about 85%, 78%, and 45% for the silver, chloride, and control, respectively, after the same period of time.

[0164] 4-column test work— Figure 4 4.1 Experimental Procedure Used to generate Figure 4 The experimental procedures for the results depicted in Figure 2 Same, except thiourea was used instead of chloride, a lower initial sulfate solution was used, 20 g / L sulfate (composed of ferric sulfate), and a lower temperature, 30°C, was used.

[0165] The ore samples used for these tests were the same as those summarized in Table 1.

[0166] 4.2 Effect of thiourea on silver Figure 4(Copper extraction with added thiourea and / or added silver in column leaching tests) shows that the addition of 0.25 g Ag / kg Cu ​​(added to the ore during agglomeration, C276) or 1 g / L thiourea (added to the leaching solution, C429) only slightly improved copper extraction compared to the control test (C278) in which neither silver nor thiourea was added - 50%, 40% and 37% for thiourea, silver and control, respectively, after the same time period. However, the addition of both 0.25 g Ag / kg Cu ​​and 1 g / L thiourea (C428) gave the highest copper extraction - about 78%. This extraction improvement was significantly higher than the additive impact of these additives.

[0167] from Figure 2-Figure 4 It is evident from the results of the test work reported in that the silver / chloride and silver / thiourea combinations greatly enhance the leaching of chalcopyrite ore.

[0168] Many modifications may be made to the embodiments of the invention described above without departing from the spirit and scope of the invention.

[0169] By way of example, this embodiment relates to Figure 1 It is described as a series of consecutive steps, in which the fragments are directly transferred to the agglomeration station 3 and then directly formed into a pile 5. The invention is not limited to this embodiment, and there may be a storage of agglomerates after the station 3. Furthermore, the station 3 and the pile 5 may not be located in the same area, and it may be necessary to transport agglomerates located in different locations between the station 3 and the pile 5.

[0170] By way of another example, although Figure 1 The embodiments are described in the context of mixing ore fragments and silver and forming agglomerates of the ore fragments and silver and then forming a heap of the agglomerates, but the invention is not so limited and extends to mixing run ore and silver and then forming a heap from the run ore.

[0171] By way of another example, although Figure 1 The embodiments are described in the context of forming agglomerates by mixing ore fragments and silver together in an agglomeration step, but the invention also extends to the following options: (a) forming agglomerates by adding silver to ore fragments in an agglomeration step and then mixing the ore fragments together; and (b) forming agglomerates of the ore fragments in an agglomeration step and then adding silver to the agglomerates.

[0172] By way of another example, although Figure 1Embodiments are described in the context of forming agglomerates by mixing together ore fragments, silver, acid and microorganisms in an agglomeration step, but the invention is not limited to forming agglomerates with acid and microorganisms. In other words, acid and microorganisms are optional additives in agglomerates.

Claims

1. A method for leaching copper-containing ore, the method comprising: (a) assessing the amount of naturally occurring silver in a copper-bearing ore, said naturally occurring silver having catalytic properties for copper leaching; (b) forming silver-containing agglomerates of (i) fragments of a copper-containing ore, (ii) an acid, (iii) optionally silver and (iv) optionally a microorganism, wherein when silver addition is desired, the agglomerate forming step comprises any of: (i) mixing the ore fragments and the added silver together in the agglomeration step, (ii) adding the silver to the ore fragments in the agglomeration step and then mixing the ore fragments together, and (iii) adding the silver to the agglomerates after the agglomerates have been formed, wherein the amount of added silver is determined by taking into account the catalytic properties of the naturally occurring silver in the ore for copper leaching, and wherein the concentration of added silver in the agglomerates is less than 0.5 g silver per kg of copper in the ore in the agglomerates; (c) forming a pile of said agglomerates; (d) adding an activating agent to the leachate to form a leachate comprising the activating agent; (e) flushing the pile of silver-containing agglomerates in the pile with the leachate, thereby enhancing the catalytic effect of the silver on the extraction of copper from the copper-containing ore by the activator added to the leachate, wherein the activator is any one or more than one of chloride, iodide, bromide and thiourea; (f) monitoring the concentration of the activating agent; (g) adding the activating agent to the leachate continuously or periodically during the course of the process to maintain a desired concentration during the process so that a desired concentration or concentration range of the activating agent is present; and (h) recovering copper from the leachate.

2. The method of claim 1, wherein the leaching is selected from the group consisting of heap leaching, vat leaching and tank leaching.

3. The method of claim 1, wherein the selected concentration or concentration range of the activating agent in the leachate is produced by any one or more of the following active steps: (a) adding the activating agent to the leachate; (b) removing the activating agent from the leachate; (c) adding the activating agent during the agglomeration step; (d) mixing different ore types taking into account said activating agent in said ore; (e) selecting and mixing / blending water source / water type with respect to said activating agent in said ore; (f) other human intervention on one or more inputs to the leaching process, said other human intervention being capable of affecting the concentration of said activating agent in said leaching process.

4. The method of claim 1, wherein said leaching is carried out in the presence of a low concentration or range of concentrations of said activating agent.

5. A process as claimed in claim 4, wherein the leaching is carried out in the presence of low concentrations of chloride, iodide and bromide up to 5 g / L in the leachate.

6. The method of claim 5, wherein the low concentration of chloride is greater than 0.8 g / L.

7. The process as claimed in claim 4, wherein said leaching is carried out in the presence of low concentration of chloride, greater than 0.2 g / L.

8. The process as claimed in claim 4, wherein the leaching is carried out in the presence of thiourea at a low concentration of less than 10 g / L in the leachate.

9. The process of claim 4, wherein said low concentration of chloride, iodide and bromide is up to 4 g / L in said leachate.

10. The method of claim 1, comprising adding said activating agent to said leachate to maintain a desired concentration during said method.

11. The method of claim 1 , comprising leaching a pile of agglomerates with said leachate.

12. A method as claimed in claim 11 wherein heap leaching comprises bioleaching with microorganisms to assist in the leaching of copper.

13. The method of claim 11, wherein heap leaching comprises controlling the heap temperature to be less than 85°C.

14. A method as claimed in claim 11, comprising controlling the oxidation potential of the leachate to less than 900 mV relative to the standard hydrogen electrode during the active leaching stage of the heap leach.

15. The method of claim 11, comprising recovering copper from the leachate in a downstream copper recovery step.

16. A method as claimed in claim 15, comprising regenerating the leachate and recycling the regenerated leachate to the pile of agglomerates.

17. The method of claim 11, wherein heap leaching comprises controlling the heap temperature to be less than 50°C.

18. The method of claim 1, wherein the added silver concentration in the agglomerates is greater than 0.02 g silver per kg copper in the ore in the agglomerates.

19. A method as claimed in claim 18, wherein the added silver concentration in agglomerates is greater than 0.2 g silver per kg copper in the ore in agglomerates.

20. The method of claim 1 including step (a)(i) or (a)(ii) and comprising adding silver in solution or in solid form to the chalcopyrite ore fragments.

21. The method of claim 1, comprising forming agglomerates further by mixing microorganisms capable of assisting in the leaching of copper.

22. The method of claim 1 including step (a)(i) or (a)(ii) and comprising adding silver as a spray or mist to the chalcopyrite ore fragments.

23. The method of claim 1 including step (a)(i) or (a)(ii) and comprising adding silver as an aerosol to the chalcopyrite ore fragments.

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