Leaching copper-containing material

Abstract

A method of leaching copper-containing material, such as ores containing chalcopyrite and / or enargite, concentrates of the ores, or tailings of the ores or the concentrates, comprising a step of leaching the copper-containing material with a leach liquor at a pH of less than 7 in the presence of an additive including a carboxylic acid functional group that enhances dissolution of copper from copper minerals in the copper-containing material by forming a complex between (a) sulfur, that has originated from copper minerals in the copper-containing material, and (b) the additive.

Description

[0001] Leaching Copper-Containing Material

[0002] Technical Field

[0003] The present invention relates to leaching copper-containing material, where the term “material” includes, for example, ores and waste materials such as tailings.

[0004] The present invention relates particularly, although not exclusively, to leaching any one or more of (a) copper-containing ores (which may be in the form of agglomerates of ore fragments), (b) concentrates of the ores, and (c) tailings of the ores or concentrates produced for example by flotation or other downstream processing of ores or concentrates.

[0005] The present invention relates particularly, although not exclusively, to leaching copper- containing sulfidic ores, such as sulfidic ores that contain copper minerals such as chalcopyrite (CuFeS2) and / or enargite (CU3ASS4). The sulfidic ores may contain other copper minerals.

[0006] The present invention relates particularly, although not exclusively, to a method of leaching copper-containing ores, particularly copper-containing sulfidic ores, using an additive to enhance dissolution of copper in the ores.

[0007] Background Art

[0008] In the leaching of copper-containing ores (including copper-containing sulfidic ores such as chalcopyrite and / or enargite or other copper-containing sulfide minerals), the particle size of the ores is typically reduced from run-of-mine size, for example by crushing and grinding operations, to allow processing via heap leaching, vat leaching or reactor leaching options.

[0009] These leaching processes involve the application of an acid and an oxidant to dissolve copper into solution. Copper is subsequently recovered from the acidic solution by a range of recovery options including solvent extraction and electrowinning (SX / EW), cementation onto more active metals such as iron, hydrogen reduction, and direct electrowinning. The acidic solution is regenerated and recycled to leach more copper from the ores. Leaching may be assisted by the use of ferrous iron oxidising and sulfur oxidizing microorganisms, as well as oxidants such as SO2 / O2, H2O2, and Fe(III), etc.

[0010] Generally, leaching may provide lower metal recoveries than other process options for recovering copper from sulfidic ores, such as milling and flotation, that produce copper- containing concentrates that are then smelted to produce copper metal.

[0011] It is known that it is difficult to leach more than 20-40 wt.% of the total copper from chalcopyrite by heap leaching. The low copper recovery is often thought to be associated with the formation of a passive film on the surface of the chalcopyrite that may be composed of degradation products from the dissolution reaction.

[0012] Leaching processes suitable for recovering copper from chalcopyrite in an alkaline environment have also been developed. In one such process, a mixture of glycine and ammonia is used to recover copper from chalcopyrite at a pH of 10.5. The glycine is used as a lixiviant which complexes with copper ions to effect phase transfer of the copper in the ore from solid to liquid and the ammonia complexes with the liberated copper ions to extend the solubility limit of these ions.

[0013] A Group company of the applicant is involved in a research and development project relating to leaching of copper-containing ores (including copper-containing sulfidic ores such as chalcopyrite and enargite).

[0014] International (PCT) Patent Application PCT / AU2019 / 050383 (WO2019 / 213694) in the name of the applicant relates to an invention that was made during the course of the project.

[0015] The invention of PCT / AU2019 / 050383 (WO2019 / 213694) is based on a realisation that leaching copper-containing ores or concentrates of the ores or tailings of the ores or concentrates produced for example by flotation or other downstream processing of ores or concentrates can be enhanced via the formation of a complex comprising (a) sulfur, that has originated from copper minerals in the ores, and (b) an additive.

[0016] International (PCT) Patent Application PCT / AU2019 / 050383 (WO2019 / 213694) identifies a number of specific additives. The disclosure in PCT / AU2019 / 050383 (WO2019 / 213694) is incorporated by crossreference.

[0017] The Group company of the applicant has carried out further research and development work and found a number of other additives that provide enhanced copper extraction efficiency compared to the additives of the invention of PCT / AU2019 / 050383 (WO2019 / 213694) and otherwise known to the applicant.

[0018] The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere.

[0019] Summary of the Disclosure

[0020] In general terms, the invention is a method of leaching copper-containing material, where the term “material” encompasses as-mined material or from stockpiles that are considered to be too low in grade to be economically processed in flotation and other wet processing systems for recovering copper from the material and includes, for example, ores, concentrates of the ores, and waste materials such as tailings of the ores. Examples of such material include ores containing chalcopyrite and / or enargite, concentrates of the ores, or tailings of the ores or the concentrates.

[0021] The method comprises a step of leaching the copper-containing material with a leach liquor at a pH of less than 7 in the presence of an additive including a carboxylic acid functional group that enhances dissolution of copper from copper minerals in the material by forming a complex between (a) sulfur, that has originated from copper minerals in the material, and (b) the additive.

[0022] The term “additive” is understood herein to encompass a reagent that is added into the reaction mixture and a reagent that is formed in-situ rather than added into the reaction mixture which enhance dissolution of copper from copper minerals in the material.

[0023] In general terms, the advantages of the invention include providing an opportunity for microorganism-assisted and / or chemically assisted leaching of copper minerals in copper-containing material, particularly low-grade ores (i.e. typically less than 2.0 wt.% copper, typically less than 1.5 % copper, typically less than 1.0 % copper), at relatively low temperatures and at comparatively low operating costs with high recoveries. One disadvantage of some existing copper extraction additives is that acid is required to maintain the low pH environment for the additives to perform optimally, for example to maximise oxidant, particularly ferric, concentration. This increases operational cost. Use of an additive that can operate under high acidic pH environment is desirable as it reduces acid consumption and raffinate bleed neutralisation requirements, particularly when treating high acid consuming copper ores.

[0024] Without being bound by theory, it is believed that the positioning of the carboxylic acid group relative to the other functional groups and / or charge of the additive influence(s) the protonation of the additive and allow(s) the additive to form a complex with sulfur under a wider acidic pH range.

[0025] The complex may comprise sulfur from the copper minerals and the additive, with the additive breaking down a passivating layer or reducing a formation of a passivating layer and therefore increasing access for leaching copper from copper material during the method.

[0026] The method may include any one of the following categories of leaching steps:

[0027] (a) heap or vat or tank leaching copper-containing material fragments, particularly ore fragments;

[0028] (b) heap or vat or tank leaching agglomerates of copper-containing material fragments, particularly ore fragments;

[0029] (c) heap or vat or tank leaching ore concentrates;

[0030] (d) heap or vat or tank leaching agglomerates of ore concentrates; and

[0031] (e) heap or vat or tank leaching tailings of the ores or concentrates produced for example in flotation or other downstream processing of ores or concentrates.

[0032] In particular, one leaching category that is of particular interest to the applicant, is heap leaching agglomerates of ore fragments or ore concentrates or tailings of the ores or concentrates. The term “fragment” is understood herein to mean any suitable size of mined or treated (e.g. crushed) material having regard to materials handling and processing capabilities of the apparatus used to carry out the method. It is also noted that the term “fragment” as used herein may be understood by some persons skilled in the art to be better described as “particles”. The intention is to use both terms as synonyms.

[0033] The additive may also include an amine functional group.

[0034] The amine functional group and the carboxylic acid functional group may be spaced by at least one carbon atom to permit the additive to form complexes between sulfur, that has originated from copper minerals in the material, and the additive.

[0035] The amine functional group and the carboxylic acid functional group may be spaced by one carbon atom.

[0036] The additive may be selected to enhance copper extraction efficiency by at least 1% compared to leaching efficiency without the additive.

[0037] The additive may be selected to enhance copper extraction efficiency by at least 5%.

[0038] The additive may be selected to enhance copper extraction efficiency by at least 20%.

[0039] The additive may be a compound that contains molecular scaffold (I) or a polymer that contains molecular scaffold (I) repeated through the polymer: wherein, the nitrogen atom is independently substituted or unsubstituted, and selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amino group; wherein the carbon atom adjacent to the nitrogen atom may be substituted or unsubstituted; and wherein the bonds between the nitrogen atom and carbon atoms in the scaffold may be single bonds or multiple bonds. A skilled person would understand a “molecular scaffold” to be a molecular core to which functional groups are attached.

[0040] The additive may be a compound of formula (II): wherein,

[0041] R1and R2are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, or alkylamino groups, or the substituents on the nitrogen atom together form an alkyl or alkynyl group that connect to form a ring R3and R4are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(=O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl or alkynyl, OC(=O)R where R is alkyl, alkenyl, or alkynyl, amino, alkylamino, alkenylamino, or alkynylamino, C(0)NH2, C(O)NHR where R is alkyl, alkenyl, or alkynyl, C(0)NR2 where R is alkyl, alkenyl, or alkynyl.

[0042] The additive may be selected from the group comprising iminodiacetic acid (IDA), diethylenetriamine pentaacetic acid (DTP A), trans-l,2-diaminocyclohexane-A, N, N', N'- tetraacetate (CDTA), [ethyleneA / '.sfoxonitrilo)]- tetraacetate (EGTA), phenyldiaminetetraacetic acid (PDTA), triethylenetetraaminehexaacetic acid (TTHA), alanine, and sarcosine

[0043] For each of the complexes, sulfur is derived from the dissolution of the copper minerals in the material, such as chalcopyrite or enargite.

[0044] The applicant believes that these complexes are preferentially formed over existing intermediary phases and thereby break down or reduce the formation of passivating layers on the copper mineral surfaces and therefore allow greater access for leaching copper from the minerals in the material.

[0045] The applicant also believes that the additive may react directly with the sulfur from the mineral to enhance leaching via reducing the activation energy, i.e. have a catalytic effect. It is preferred that the additive be sufficiently water soluble to be able to enhance copper extraction into the leach solution.

[0046] The additive may be a degradation product that forms under the conditions of the leach and is an effective additive in the terms of the invention.

[0047] By way of example, the degradation product may be a degradation product of another said additive.

[0048] The concentration of the additive 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, and more typically up to 1 g / L, in the leach liquor.

[0049] The method may include adjusting the concentration of the additive in the regenerated leach liquor to maintain the concentration at 1 g / L in the regenerated leach liquor.

[0050] The method may include adding the additive to the leach liquor continuously or periodically during the method to maintain a required concentration during the method.

[0051] The method may include adding the additive to copper-containing material fragments, particularly ore fragments prior to the leaching step.

[0052] The method may include forming agglomerates of copper-containing material fragments, particularly ore fragments and adding the additive to agglomerates prior to the leaching step.

[0053] The method may include forming agglomerates of copper-containing material fragments, particularly ore fragments and adding the additive while forming agglomerates.

[0054] The method may include forming agglomerates of copper-containing material fragments, particularly ore fragments, wherein the additive is either sarcosine or triethylenetetraaminehexaacetic acid (TTHA), and the method of forming agglomerates may include:

[0055] (a) forming an additive solution having a pH less than 7; (b) optionally heating the solution to at least 40 °C to speed up dissolution and / or dilution of the additive; and

[0056] (c) adding the additive solution to the copper-containing material fragments at the start of the forming agglomerates.

[0057] The method may include regenerating the leach liquor and recycling the regenerated leach liquor.

[0058] The method may include adjusting the concentration of the additive in the regenerated leach liquor to maintain a concentration of up to 10 g / L in the leach liquor.

[0059] The method may include adding or removing the additive to the regenerated leach liquor to maintain a concentration of up to 10 g / L in the leach liquor.

[0060] The method may include adjusting the concentration of the additive in the regenerated leach liquor to maintain the concentration at 1 g / L in the regenerated leach liquor.

[0061] The concentration adjustment may include adding the additive to the regenerated leach liquor to maintain the concentration.

[0062] The concentration adjustment may include removing the additive from the regenerated leach liquor to maintain the concentration.

[0063] The method may include bioleaching with microorganisms.

[0064] The microorganisms may be one or more than one of psychrotolerant or mesophilic or thermophilic (moderate or extreme) bacteria or archaea. The microorganisms may be acidophilic bacteria or archaea. The microorganisms may be thermophilic acidophiles.

[0065] The method may include adding chemical oxidants to the leach liquor.

[0066] The method may include adding ferric ions to the leach liquor as a chemical oxidant.

[0067] The chemical oxidants may also include any one or more of pyrolusite, permanganate ions, peroxide ions, and chlorate ions.

[0068] The method may include adding chloride ions to the leach liquor. Suitably, the concentration of chloride added to the leach liquor is less than 5g / L, less than 3g / L or less than Ig / L. The method may include controlling the temperature of the leach liquor to be less than 100 °C, less than 65 °C, less than 60 °C, less than 55 °C, or less than 50 °C.

[0069] The method may include controlling the temperature of the leach liquor to be at least 30 °C or at least 40 °C or at least 50 °C. It is believed that controlling the temperature of the leach liquor to be at least 40°C enhances sulfur complexation and / or chalcopyrite dissolution.

[0070] The method may include controlling the oxidation potential of the leach liquor during an active leaching phase to be less than 900 mV, less than 800 mV, in a range of 500 to 800 mV, or in a range of 600 to 750 mV, wherein the oxidation potential is determined with respect to a standard hydrogen electrode.

[0071] It is noted that the oxidation potential will change during leaching and is likely to be higher when much of the copper has been leached and the reference to “active leaching phase” is intended to acknowledge this potential change.

[0072] The method may include controlling the pH of the leach liquor to be less than 4.

[0073] The method may include controlling the pH of the leach liquor to be less than 3.2.

[0074] The method may include controlling the pH of the leach liquor to be less than 2.5.

[0075] The method may include controlling the pH of the leach liquor to be in a range of 1.2 to 2.5.

[0076] Controlling the pH to be in an acidic environment, particularly up to pH 2.5 may reduce acid consumption and raffinate bleed neutralisation requirements when treating high acid consuming copper material, particularly ores.

[0077] The method may include recovering copper from the leach liquor in downstream copper recovery steps.

[0078] Typically, the downstream recovery steps include recovering copper from solution in pregnant leach liquor.

[0079] The method may include supplying the leach liquor to a heap of agglomerates of copper-containing material fragments, particularly ore fragments and allowing the leach liquor to flow through the heap and leach copper from agglomerates and collecting leach liquor from the heap, processing the leach liquor and recovering copper from the liquor.

[0080] The method may include a step of agglomerating copper-containing material fragments, particularly ore fragments for use in forming the heap.

[0081] The agglomeration step may include mixing together an acid, typically sulfuric acid but could also be dilute hydrochloric or nitric acid, with copper-containing material fragments, particularly ore fragments. The added acid dose rate may be less than 100 kg TbSO dry t ore, typically less than 50 kg E SCh / dry t ore, typically less than 30 kg EbSCfl / dry t ore, and may be less than 10 kg EbSCh / dry t ore or less than 5 kg EbSCh / dry t ore. Typically, the acid dose rate is 0.5 - 10 kg EbSO dry t ore.

[0082] The agglomeration step may include mixing together pregnant leach solution or raffinate with copper-containing material fragments, particularly ore fragments.

[0083] The agglomeration step may include mixing microorganisms that can assist leaching copper-containing material fragments, particularly ore fragments. The microorganisms may be one or more than one of mesophilic, thermophilic (moderate or extreme) or psychrotolerant bacteria or archaea. The microorganisms may be acidophilic bacteria or archaea. The microorganisms may be thermophilic acidophiles.

[0084] The agglomeration step may include simultaneously mixing and agglomerating copper- containing material fragments, particularly ore fragments.

[0085] The agglomeration may include mixing copper-containing material fragments, particularly ore fragments in one-step and then agglomerating the mixed fragments in a subsequent step. There may be overlap between the mixing and agglomeration steps.

[0086] The method may include reducing the size of a mined material prior to the agglomeration step.

[0087] By way of example, the method may include crushing the mined material prior to the agglomeration step. The mined material may be crushed using any suitable means. The method may include crushing the mined material in a primary crushing step prior to the agglomeration step.

[0088] The term “primary crushing” is understood herein to mean crushing material to a top size of 250 to 150 mm in the case of copper-containing ores where the copper is in the form of sulfides. It is noted that the top size may be different for material containing different valuable metals.

[0089] The method may include crushing the mined material in a primary crushing step and then a secondary and possibly tertiary and possibly quaternary crushing step prior to the agglomeration step.

[0090] The invention also provides a heap of material, with the material including the abovedescribed agglomerates of material fragments.

[0091] The invention also includes a method of heap leaching that includes:

[0092] (a) forming a heap of material, with the material including the above-described agglomerates; and

[0093] (b) leaching valuable metal from the material in the heap with a leach liquor.

[0094] Heap leaching may include recovering copper from the leach liquor in downstream copper recovery steps.

[0095] The leach liquor may be regenerated and recycled to the heap.

[0096] The leaching step may include adding the additive during the step.

[0097] The method may also include recovering the leached metal as a metal product. Typically, this step includes recovering the leached metal from solution in a pregnant leach liquor.

[0098] The method may include forming heaps of the copper-containing material.

[0099] Brief Description of the Drawings

[0100] The present invention is described further with reference to the accompanying drawings of which: Figure 1 illustrates the steps in one embodiment of a method of heap leaching agglomerates of fragments of copper-containing ore that contains chalcopyrite and / or enargite with a leach liquor containing an additive in accordance with the present invention;

[0101] Figure 2 is a graph illustrating the copper extraction efficiency of sarcosine at pHs ranging from 1.2 to 2.5 on chalcopyrite mineral samples;

[0102] Figure 3 is a graph illustrating the copper extraction efficiency of various additives according to the present invention at a pH of 1.2 on chalcopyrite mineral samples;

[0103] Figure 4 is a graph illustrating the copper extraction efficiency of various additives according to the present invention at a pH of 2.5 on chalcopyrite mineral samples; and

[0104] Figure 5 is a graph illustrating the copper extraction efficiency of sarcosine, TTHA and EGTA according to the present invention at a pH of 2.5 on chalcopyrite rich ore samples.

[0105] Description of Embodiment

[0106] The following description is in the context of heap leaching agglomerates of copper- containing ore fragments

[0107] It is noted that not all of the experimental work that has been carried out is reported in the specification and that the overall results of the work are positive and indicate invention is applicable to tank, vat and heap leaching.

[0108] Further to the preceding paragraph, it is noted that the invention extends to heap, vat and tank leaching copper-containing material that are in the form of fragments or in the form of agglomerates of fragments.

[0109] It is also noted that the invention also extends to heap, vat, and tank leaching concentrates of copper-containing material, with the concentrates being in any suitable form, including unagglomerated and agglomerated forms. It is also noted that the invention also extends to heap or vat or tank leaching tailings of the material or concentrates produced for example in flotation or other downstream processing of material or concentrates.

[0110] As noted above, the invention comprises leaching copper-containing material with a leach liquor in the presence of an additive that enhances the dissolution of copper from copper minerals in the material by forming a complex between (a) sulfur, that has originated from copper minerals in the material, and (b) the additive. Nitrogencontaining organic complexing additives are specific examples of the additive.

[0111] The flow sheet of Figure 1 shows the steps in one embodiment of a method of heap leaching agglomerates of fragments of copper-containing ore that contains chalcopyrite and / or enargite with a leach liquor containing an additive in accordance with the invention.

[0112] The method includes the steps of forming agglomerates of copper containing ore in an agglomeration station 3, forming a heap 5 from the agglomerates, supplying a leach liquor 15 to the heap 5 and taking copper into solution, collecting leach liquor after it has passed through the heap, recovering copper from solution in the leach liquor from the heap in a copper recovery circuit 17, for example by solvent extraction, and regenerating the leach liquor from the heap and recycling the regenerated leach liquor to the heap.

[0113] With reference to Figure 1, the following feed materials are transferred to the agglomeration station 3 and are mixed together and form agglomerates:

[0114] (a) fragments of copper containing ore that includes chalcopyrite and / or enargite that have been crushed to a suitable particle size distribution, identified by the numeral 7 in the Figure;

[0115] (b) optionally an activation agent, such as silver, in this embodiment as a silver solution (but could be in a solid form), typically having an added concentration of silver of less than 5 g silver per kg copper in the ore in the agglomerates, identified by the numeral 9 in the Figure; (c) an acid, typically sulfuric acid, identified by the numeral 11 in the Figure in any suitable concentration; and

[0116] (d) microorganisms, identified by the numeral 13 in the Figure, of any suitable type and in any suitable concentration.

[0117] The agglomerates produced in the agglomeration station 3 are subsequently used in the construction of the heap 5.

[0118] For example, the agglomerates produced in the agglomeration station 3 may be transferred directly to a heap construction site. Alternatively, the agglomerates may be stockpiled and used as required for a heap. The agglomeration station 3 and the heap 5 are typically in close proximity. However, this is not essential and may not be the case.

[0119] By way of example only, the heap may be a heap of the type described in International publication W02012 / 031317 in the name of the applicant and the disclosure of the heap construction and leaching process for the heap in the International publication is incorporated herein by cross-reference.

[0120] In a heap leaching operation, copper in the chalcopyrite and other copper-containing minerals in the agglomerates is leached from the agglomerates in the heap 5 via the supply of the leach liquor 15 and is taken into solution in the leach liquor as the leach liquor passes through the heap 5.

[0121] The leached copper is recovered from the leach liquor in the downstream copper recovery circuit 17.

[0122] The recovered copper 19 is transferred for further processing and the leach liquor 23 is transferred to and regenerated in a regeneration circuit 21 and recycled to the heap 5 as leach liquor 15 to leach more copper from the chalcopyrite and other copper-containing minerals in the agglomerates in the heap 5.

[0123] The agglomeration station 3 may be any suitable construction that includes a drum, conveyor (or other device) for mixing the feed materials for the agglomerates and agglomerating the feed materials. The agglomeration conditions in the agglomeration station 3 are selected to form agglomerates of the required size and mechanical properties for the heap 5.

[0124] Mixing and agglomerating the feed materials for the agglomerates may occur simultaneously. Alternatively, mixing the feed materials may be carried out first and agglomerating (for example initiated by the addition of the acid) may be carried out after mixing has been completed to a required extent. Moreover, the timing of adding and then mixing and agglomerating feed materials may be selected to meet the end-use requirements for the agglomerates. For example, it may be preferable in some situations to start mixing fragments containing chalcopyrite and then adding silver in a solution or in a solid form of silver, acid, and microorganisms progressively in that order at different start and finish times in the agglomeration step. By way of particular example, it may be preferable in some situations to start mixing fragments containing chalcopyrite and then adding silver in a solution or in a solid form and acid together, and then adding microorganisms at different start and finish times in the agglomeration step.

[0125] The additives of the invention may be added to the leach liquor 15 in the required concentrations. Typically, the concentration of the additive is up to 10 g / L, up to 5 g / L, up to 2.5 g / L, up to 1.5 g / L, up to 1.25 g / L, or up to 1 g / L, in the leach liquor.

[0126] Alternatively, or in addition, the additives of the invention may be added while forming agglomerates in the agglomeration station 3.

[0127] As indicated above, a Group company of the applicant has carried out leach testing to investigate the impact of a number of additives in leach liquors on chalcopyrite mineral samples and chai copy rite / enargite ores.

[0128] The leach tests are described in the Examples below.

[0129] Examples

[0130] The test work using additive-containing liquor was conducted in small scale leaching reactors. The following results were obtained with low grade chalcopyrite mineral samples containing less than 2 wt.% copper.

[0131] Carboxylic acid tests

[0132] Reactor leaching tests were conducted at a pH of 1.2 and a pH of 2.5. The pH was maintained at the desired value by adding an acid (H2SO4) or a base (LiOH). The oxidation potential of the solutions was maintained at approximately 700 mV determined with respect to the standard hydrogen electrode to simulate conditions that may be seen when leaching copper ores. The oxidation potential was maintained at the desired value by adding an oxidant (H2O2) or a reductant (Li2SO3). The initial leach solutions were acidified iron solutions at ~2 g / L Fe(III) added as a sulfate. The tests were maintained at 50 °C. Baseline tests were carried out at pH 1.2 without any additive. Tests with additives were carried out with additive concentrations of 1 g / L.

[0133] The following additives were tested: IDA, DTP A, TTHA, EGTA, PDTA, CDTA, sarcosine, and alanine.

[0134] The tests results are summarised in Figures 2-4 for the chalcopyrite mineral samples. Figure 2 is a graph illustrating the copper extraction efficiency of sarcosine at pHs ranging from 1.2 to 2.5.

[0135] Figure 3 is a graph illustrating the copper extraction efficiency of various additives according to the present invention at a pH of 1.2.

[0136] Figure 4 is a graph illustrating the copper extraction efficiency of various additives according to the present invention at a pH of 2.5.

[0137] The tests showed:

[0138] (a) a faster dissolution rate for chalcopyrite at the higher pH 2.5;

[0139] (b) an improvement with the additives IDA, DTP A, PDTA and CDTA at both pH 1.2 and 2.5; and

[0140] (c) significant improvement with the additives sarcosine, EGTA, TTHA and alanine at pH 2.5. tests with chalcopyrite / enaraite ore

[0141] In order to facilitate testing the impact of ferric ions on copper extraction at pH 2.5, leach tests were undertaken with a chalcopyrite / enargite ore crushed to Pioo 12 mm in 80 g / L sulfate start solution (low ferric) at 50 °C with the oxidation potential maintained at 700 mV.

[0142] The test results are presented in Figure 5.

[0143] Figure 5 shows that copper extraction involving the use of carboxylic acid additives can be further enhanced by that the addition of ferric ions. Specifically, Figure 5 show that:

[0144] (i) the copper extraction efficiency of TTHA at pH 2.5 after 60 days increases from 18% to -65%;

[0145] (ii) the copper extraction efficiency of EGTA at pH 2.5 after 60 days increases from

[0146] 12% to -40%; and

[0147] (iii) the copper extraction efficiency of Sarcosine at pH 2.5 after 30 days increases from 10% to 30%. The results show that the addition of ferric ions improves the copper extraction efficiency by at least 300%.

[0148] Many modifications may be made to the invention as described above without departing from the spirit and scope of the invention.

Claims

CLAIMS1. A method of leaching copper-containing material, comprising a step of leaching the copper-containing material, with a leach liquor at a pH of less than 7 in the presence of an additive including a carboxylic acid functional group that enhances dissolution of copper from copper minerals in the material by forming a complex between (a) sulfur, that has originated from copper minerals in the material, and (b) the additive.

2. The method according to claim 1, wherein the complex comprises sulfur from the copper minerals and the additive, with the additive breaking down a passivating layer or reducing a formation of a passivating layer and therefore increasing access for leaching copper from the copper-containing material during the method.

3. The method according to claim 1 or claim 2, wherein the additive also includes an amine functional group.

4. The method according to claim 3, wherein the amine functional group and the carboxylic acid functional group are spaced by at least one carbon atom to permit the additive to form complexes between sulfur, that has originated from copper minerals in the coper-containing material, and the additive.

5. The method according to any one of the preceding claims, wherein the additive is selected to enhance copper extraction efficiency by at least 1%.

6. The method according to any one of the preceding claims, wherein the additive is a compound that contains molecular scaffold (I) or a polymer that contains molecular scaffold (I) repeated through the polymer:wherein, the nitrogen atom is independently substituted or unsubstituted, and selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amino group; wherein the carbon atom adjacent to the nitrogen atom may besubstituted or unsubstituted; and wherein the bonds between the nitrogen atom and carbon atoms in the scaffold may be single bonds or multiple bonds.

7. The method according to any one of the preceding claims 1 to 5 wherein the additive is a compound of formula (II):wherein,R1and R2are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, or alkylamino groups, or the substituents on the nitrogen atom together form an alkyl or alkynyl group that connect to form a ringR3and R4are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(=O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl or alkynyl, OC(=O)R where R is alkyl, alkenyl, or alkynyl, amino, alkylamino, alkenylamino, or alkynylamino, C(O)NH2, C(O)NHR where R is alkyl, alkenyl, or alkynyl, C(O)NR2 where R is alkyl, alkenyl, or alkynyl.

8. The method according to any one of claims 1 to 5, wherein the additive is selected from the group comprising iminodiacetic acid (IDA), diethylenetriamine pentaacetic acid (DTP A), transd,2-diaminocyclohexane- / V,A(A', A'-tetraacetate (CDTA), [ethylene / vsfoxonitrilo)]- tetraacetate (EGTA), phenyldiaminetetraacetic acid (PDTA), triethylenetetraaminehexaacetic acid (TTHA), alanine, and sarcosine.

9. The method according to any one of the preceding claims, wherein the concentration of the additive is up to 10 g / L in the leach liquor.

10. The method according to any one of the preceding claims, includes controlling the temperature of the leach liquor to be less than 100 °C.

11. The method according to any one of the preceding claims, includes controlling the oxidation potential of the leach liquor during an active leaching phase to be less than 900 mV, wherein the oxidation potential is determined with respect to a standard hydrogen electrode.

12. The method according to any one of the preceding claims, includes controlling the pH of the leach liquor to be less than 3.2.

13. The method according to any one of the preceding claims, includes bioleaching with microorganisms.

14. The method according to any one of the preceding claims, includes adding ferric ions as an oxidant to the leach liquor.

15. The method according to any one of the preceding claims, includes recovering copper from the leach liquor in downstream copper recovery steps.

16. The method according to any one of the preceding claims, includes adding the additive to the leach liquor continuously or periodically during the method to maintain a required concentration during the method.

17. The method according to any one of claims 1 to 14, includes adding the additive to copper-containing material fragments prior to the leaching step.

18. The method according to any one of claims 1 to 14, includes forming agglomerates of copper-containing material fragments and adding the additive to agglomerates prior to the leaching step.

19. The method according to any one of claims 1 to 14, includes forming agglomerates of copper-containing material fragments and adding the additive while forming agglomerates.

20. The method according to any one of claims 1 to 14, includes forming agglomerates of copper-containing material fragments, wherein the additive is either sarcosine or triethylenetetraaminehexaacetic acid (TTHA), and the agglomerate forming step includes:(a) forming an additive solution having a pH less than 7;(b) optionally heating the solution to at least 40 °C to speed up dissolution and / or dilution of the additive; and(c) adding the additive solution to the copper-containing material fragments at the start of forming agglomerates.

21. The method according to any one of the preceding claims, includes regenerating the leach liquor and recycling the regenerated leach liquor.

22. The method according to claim 21, includes adjusting the concentration of the additive in the regenerated leach liquor to maintain a concentration of up to 10 g / L in the leach liquor.

23. A method of leaching copper-containing material, that includes leaching the copper-containing material with a leach liquor at a pH of less than 7 in the presence of a carboxylic acid-containing organic complexing additive that forms a complex between sulfur, that has originated from copper minerals in the material, and wherein the additive is a degradation product that forms under conditions of the leach.

24. The method defined in claim 23, wherein the complex comprises sulfur in a passivating layer on copper minerals and the additive, with the complex breaking down the passivating layer or reducing formation of the layer and therefore allowing greater access for leaching copper from copper minerals during the method.

25. The method defined in claim 23 or claim 24, wherein the degradation product is a degradation product of another additive.

26. The method according to any one of claims 23 to 25, wherein the additive includes an amine functional group.

27. The method according to claim 26, wherein the amine functional group and the carboxylic acid functional group are spaced by at least one carbon atom to permit the additive to form complexes between sulfur, that has originated from copper minerals in the copper-containing material, and the additive.

28. The method according to any one of claims 23 to 27, wherein the additive is selected to enhance copper extraction efficiency by at least 1%.

29. The method according to any one of claims 23 to 28, wherein the additive is a compound that contains molecular scaffold (I) or a polymer that contains molecular scaffold (I) repeated through the polymer:wherein, the nitrogen atom is independently substituted or unsubstituted, and is selected from the group consisting of a primary amine group, a secondary amine group, and a tertiary amino group; the carbon atom adjacent the nitrogen atom may be substituted or unsubstituted; and the bonds between the nitrogen atom and carbon atoms in the scaffold may be single bonds or multiple bonds; or the additive is a compound having the following formula:wherein,R1and R2, are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, and alkylamino groups, or the substituents on the nitrogen atom together form an alkyl or alkynyl group that connect to form a ring; andR3and R4are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(=O)R where R is alkyl, alkenyl, or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl, or alkynyl, OC(=O)R where R is alkyl, alkenyl, alkynyl, amino, alkylamino, alkenylamino, alkynylamino, C(0)NH2, C(O)NHR where R is alkyl, alkenyl, or alkynyl, C(0)NR2 where R is alkyl,alkenyl, or alkynyl, or R7and R8together and / or R9and R10together may be selected from =0, =NH or =NH where R is alkyl, alkenyl or alkynyl.

30. A method of leaching copper-material comprising leaching the copper- containing material with a leach liquor at a pH of less than 7 in the presence of an additive that enhances dissolution of copper from copper minerals in the ores by at least 1% by forming a complex between (a) sulfur, that has originated from copper minerals in the material, and (b) the additive, wherein the additive is a compound having the following formula:wherein,R and R- are each independently selected from a lone pair electron, H, alkyl groups, alkenyl groups, alkynyl groups, and alkylamino groups, or the substituents on the nitrogen atom together form an alkyl or alkynyl group that connect to form a ring; are each independently selected from H, alkyl, alkenyl, alkynyl, OH, alkyloxy groups, alkenyloxy groups, alkynyloxy groups, C(=O)R where R is alkyl, alkenyl or alkynyl, C(O)OH, C(O)OR where R is alkyl, alkenyl, or alkynyl, OC(=O)R where R is alkyl, alkenyl, or alkynyl, amino, alkylamino, alkenylamino, or alkynylamino, C(0)NH2, C(O)NHR where R is alkyl, alkenyl, or alkynyl, C(0)NR2 where R is alkyl, alkenyl, or alkynyl.

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