OA18658A - Process for selective recovery of Chalcophile Group Elements. - Google Patents

Abstract

A process for the selective recovery of at least one Chalcophile Group Element ("CPM") as herein defined from a material containing the CPM and one or more non Chalcophile Group Elements ("NCE") as herein defined, said process including: contacting the material with an alkaline solution containing a lixiviant comprising an amino acid or derivative thereof in order to selectively leach the CPM from the material to produce a CPM containing leachate and a NCE containing residue; and recovering the CPM from the leachate.

Description

PROCESS FOR SELECTIVE RECOVERY OF CHALCOPHILE GROUP ELEMENTS

TECHNICAL FIELD

A process is disclosed for the sélective extraction and recovery of a range of éléments that belong to an economically important group of éléments, herein defined as “chalcophile group éléments”, over other less economically important éléments. The process may be used for sélective recovery from ores, or ore concentrâtes. However, the disclosure is to be broadly interpreted, in that the process may be used for sélective recovery from other métal containing materials, such as process intermediates and/or secondary or waste materials.

BACKGROUND ART

Many economically significant éléments are locked in minerai or rock matrices in nature with significant amounts of acid consuming minerais and other non-economic or gangue éléments. If the target metals are of a high enough grades in the ore and mineralised predominantly as sulfides, they are amenable to beneficiation and upgrading by flotation followed by subséquent smelting and refining, which is the conventional metallurgical process to treat sulfides. However, due to exhaustion of high grade ore resources and reserves amenable to the conventional mine-mill-float-smelt-refine Processing, various hydrometallurgical approaches hâve been evaluated. Where a minerai concentrate can be produced from an ore, another Processing option may be to replace the smelting step (which is capital intensive) with a hydrometallurgical step. Hydrometallurgical Processing often includes leaching in the acidic région or, (less commonly) in the alkaline région. While alkaline leaching has been used previously to leach some metals, such as gold and copper, from ores, there has been very little success in leaching other metals in alkaline solutions, other than by the toxic compounds such as ammonia and cyanide, and because of the large quantities of ammonia or cyanide required, with commensurate cost and safety implications, these alternative processes hâve not had much industrial application.

Except for gold and silver leaching, alkaline cyanide leaching has never gained wide acceptance. As gold and silver ores become more mineralogically complex and the relative inability to sufficiently recover the (cyanide) reagent, (particularly due to the many deportment and conversion reactions of cyanide), even cyanide is being reviewed as an acceptable lixiviant. As many métal sulfides are cyanicides (cyanide destroyers) and cyanide is easily destroyed using stronger oxidants (such as hydrogen peroxide), cyanide consumption tends to be very high with complex ligand chemistry where multiple cyanide complexes are possible and changes between the complexes are sensitive to cyanide to métal ratios and pH. The formation of thiocyanate,

- 2 cyanate, ferrocyanide/ferricyanide and volatile hydrocyanic acid ail contribute to loss mechanisms of cyanide, making for poor lixiviant recovery in some Systems. In addition, cyanides, such as sodium cyanide, and cyanides of other alkali (such as potassium) metals and alkali earth metals (such as calcium), pose a number of challenges, principally due to their toxicity, regulatory restrictions, high carbon footprint and low selectivity in low grade ores.

The current alternative lixiviants to cyanide also pose many challenges. Despite sodium thiosulfate being proposed as an alternative lixiviant for gold, it is expensive, it requires additional copper (as Cu²⁺) as an oxidant (if not already présent in the gold ore) and volatile and noxious ammonia to stabilise the leaching System. It is applicable to only a limited number of gold ores. Further, it cannot economically be produced at site, it requires complex downstream séparation and it Is not biodégradable.

Ammonia leaching per se has not gained acceptance except for a few niche cases, and has been found to be unsuitable for whole-ore leaching. Ammonia (the lixiviant) can vaporise, be oxidised, is poisonous, and much of it is required, whilst at the same time, the solubility of ammonia gas in water is limited and decreases with température. (As used herein, the reference to “ammonia” includes ammonium hydroxide).

In contrast to the above mentioned alkaline processes, the acidic leach processes hâve been more commonly employed. These acidic processes hâve numerous problème, and the most commonly used acid, sulfuric acid (either added or produced during sulfide oxidation) will be discussed below:

• In biological oxidation processes during leaching target métal sulfides are oxidised and dissolved in acidic media. It is important to maintain the pH below 3 to ensure that the main oxidant (ferrie iron) remains dissolved. Above this pH the ferrie is precipitated and the oxidant is lost from solution.

• Many minerai deposits contain many acid consuming and alkaline minerais such as calcite, magnesite, dolomite, trôna, siderite, etc., consuming the acid and raising the pH that may lead to unwanted and unintended métal précipitation. This is particularly problematic in Systems where pH may vary in time and spatial direction, such as in heap, dump, vat and in-situ leaching.

• In the pH région (pH<2) where oxygen and ferrie iron are effective oxidants, significant dissolution of silica (SiO₂), magnésium, iron and aluminium is possible. These reactions consume acid, but more problematically, these compounds are sensitive to pH variation, with the potential to precipitate as gelatinous précipitâtes that cannot be efficiently separated from the target métal containing mother liquor.

• As most ore deposits contain significant amounts of calcium, the reaction with sulfuric acid produces a gypsum precipitate which increases the viscosity and may lead to lowering of the porosity of heaps and in-situ leach Systems.

• When acids corne in contact with carbonate minerais they release carbon dioxide. This is problematic in in-situ leaching where gas bubbles may block pores.

• Many sulfides co-produce elemental sulfur as a leach product. This elemental sulfur can severely passivate target minerais and metals to be leached, or stop leaching altogether. It is particularly problematic when precious metals are associated with sulfides. Elemental sulfur can also lead to pore blockages in Systems dépendent on good ore porosity.

• Acids are often indiscriminate in their dissolution action, often dissolving significant amounts of non-target metals. This leads to poorer contrai of solution chemistry.

• Materials of construction tend to be problematic. Oxygenated aqueous sulfuric acid is highly corrosive to most metallic materials of construction.

• Hydrogen peroxide is not an effective oxidant in acidic media as it tends to décomposé very quickly (faster than the required oxidation rate) to release oxygen.

• Electrowinning processes (from sulfate solutions) hâve to deal with acid mist génération during métal recovery processes.

• Sulfide précipitation processes hâve to deal with the risk of highly poisonous and noxious hydrogen sulfide formation in acidic medium.

Other acidic media such as hydrochloric acid with NaOCI, chlorine or oxygen as oxidants are highly corrosive and also tend to be indiscriminate in their dissolution of minerais. Even more gangue minerais are soluble in hydrochloric acid (compared to sulfuric acid), thereby releasing even more unwanted species into solution. Neutralisation of excess acid is problematic as the chloride ion that remains in the leach circuit remains soluble and tends to accumulate in leach Systems.

Other acids (nitric, hydrofluoric, phosphoric, other halogen acids) hâve problème with noxious vapours, décomposition, price, availability, neutralisation ability, materials of construction, etc.

Most acids are either indiscriminate in minerai dissolution, or do not hâve sufficient sélective complexing ability, or hâve significant problems with reagent recovery and recycle. Occupational safety, health and environmental aspects, while being dealt with as a matter of

- 4 necessity, tend to be much more problematic in acidic media, partîcularly for métal recovery processes such as electrowinning and sulfide précipitation. The solubility of silica and the potential of gel précipitation together with other gelatinous précipitâtes from dissolved iron and alumina, créâtes large problems with potential “crud” formation in solvent extraction circuits or sticky/slimy coatings onto IX resin beads which may retard the efficiency of the extraction and refining operations.

The above référencés to the background art do not constitute an admission that the art forms a part of the common general knowledge of a person of ordinary skill in the art. The above référencés are also not intended to limit the application of the apparatus and method as disclosed herein.

SUMMARY OF THE DESCLOSURE

In order to facilitate discussion of the présent disclosure, référencé will be made to the Goldschmidt classification of the Periodic Table, which is a geological, rather than Chemical, classification of the éléments. The Goldschmidt Periodic Table is set out in Figure 1.

The Goldschmidt Periodic Table classifies the éléments into 5 broad groups: Lithophile (“rock”-loving / rock forming or silicate-loving éléments), Siderophile (iron-loving), Chalcophile (sulfur/sulfide-loving), Atmophile and Synthetic. The présent discussion will focus on the Chalcophile (cp) and Siderophile (sp) transition metals.

The présent disclosure is based on the surprising discovery that a group of éléments comprising respective members of the chalcophile éléments and the siderophile éléments, (herein after collectively referred to as Chalcophile Group Eléments”, or “CPMs”) can be selectively leached over non- Chalcophile Group Eléments (or “NCEs”) by leaching using an alkaline solution containing an amino acid or dérivative thereof as the primary lixiviant. The leach may occur with or without the use of a catalyst. Alkaline amino acid leaches can progress without the aid of the catalysts, but the use of small amounts of catalyst may improve the rate of leaching and lower the température at which high leach rates (with amino acids) can be obtained.

The CPMs, and their respective Goldschmidt classifications, include cobalt (sp), nickel (sp), copper (cp), zinc (cp), rhodium (sp), palladium (sp), gold (sp), silver (cp), cadmium (cp), indium (cp), iridium (sp), platinum (sp), mercury (cp), gallium, (cp), germanium (cp), arsenic (cp), bismuth (cp), tin (cp), lead (cp) and thallium (cp).

The inventors hâve recognised that the siderophile members of the CPMs listed above also hâve a high affinity for sulfur in addition to their affinity for iron (as alloys), and tend to be more noble or less reactive (LR) partîcularly with respect to their affinity for oxygen to form oxides. Some other metals (iron, molybdenum, manganèse, ruthénium, osmium, rhénium) are also

- 5 classified as siderophiles in the Goldschmidt classification System, but are more reactive (MR) siderophiles. These more reactive (MR) siderophiles hâve a high affinity for oxygen and tend to form stable oxides, compared to the less reactive (LR) / more noble siderophiles in the same rows of the periodic table. The divide between the LR and MR siderophiles is therefore between Groups 8 and 9 of the Periodic Table, with the LR siderophiles to the right of that line and the MR siderophiles to the left of that line.

The CPMs therefore comprise the LR siderophiles and the chalcophiles up to and including some of the Group 14 éléments of the Periodic Table. In other words, the CPMs comprise: Co, Ni, Cu, Zn, Ga, Ge, Rh, Pd, Ag, Cd, In, Sn, Ir, Pt, Au, Hg, Tl, Pb and Bi. In an embodiment, the CPMs may comprise: Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, Cd, In, Sn, Ir, Pt, Hg, Tl, Pb and Bi. In another embodiment, the CPMs may comprise: Co, Ni, Zn, Ga, Ge, Rh, Pd, Cd, In, Sn, Ir, Pt, Hg, Tl, Pb and Bi. In a further embodiment, the CPMs may comprise Co, Ni, Zn, Ga, Ge, Cd, In, Sn, Hg, Tl, Pb, Bi.

In one embodiment, the CPMs may comprise siderophile and chalcophile éléments in Periodic Table Groups 9-12 (the version of the Periodic Table is shown in Figure 1)..

In another embodiment, the CPMs may include siderophile éléments in Periodic Table Groups 9 and 10. The CPMs may additionally or instead comprise chalcophile éléments in Group 12.

The non-Chalcophile Group Eléments (NCEs) comprise ail éléments that are not members of the CPMs and comprise:

• MR-siderophiles • the lithophiles (Ip) (the “rock”-loving / rock forming or silicate-loving éléments), form the major components of the earth’s crust, and are often found as oxides, carbonates, silicates, alumino-silicates, and hydroxylated silicates or minerais containing halogen groups (fluoride and chloride in particular). They constitute the major gangue minerai (i.e. waste minerai) components in ores where the scarce metals of the chalcophile metals (CPMs) are targeted for économie recovery. The lithophiles include:

o the alkali metals (lithium, sodium, potassium, i.e. éléments of Group 1 of the Periodic Table);

o alkaline earth metals (béryllium, magnésium, calcium, strontium, barium, i.e. éléments of Group 2);

o the lanthanides (“Rare Earths”), the actinides (including uranium and

- 6 thorium) and the reactive and oxygen-loving metais (forming very stable oxides) such as Groups 3 - 8 in the Periodic Table.

· The éléments normally associated with non-metals as normally found in Groups 13 to 18 in the Periodic Table (PT), to the right (larger Group Numbers) of the semi/half metallic éléments (the semi-metals being boron, Silicon, arsenic, and tellurium); and • Other lithophile éléments such as boron, aluminium, Silicon, phosphorus, oxygen, and the halogens.

In a first aspect there is disclosed a process for the sélective recovery of at least one Chalcophile Group Element (“CPM”) as herein defined from a material containing the CPM and one or more non Chalcophile Group Eléments (“NCE”) as herein defined, said process including:

(i) contacting the material with an alkaline solution containing a lixiviant comprising an amino acid or dérivative thereof in order to selectively leach the CPM from the material to produce a CPM containing leachate and a NCE containing residue; and (ii) recovering the CPM from the leachate.

As used herein, the term amino acid” means an organic compound containing both a carboxyl (—COOH) and an amino (—NH₂) functional group. In many cases, the amino acid contains a -CHR or CH₂ group. In most cases the amino (-NH₂) group and the carboxyl (-COOH) group connects to the same -CHR or -CH₂ connecting group and are referred to primary a-aminoacids. The “R” group in the -CHR connecting group can take on any organic structure, such as aliphatic hydrocarbon groups to complex organic structures including aromatic groups, heterocyclic groups, and poly-nuclear groups or various other organic groups. In its simplest form, the R-group is only hydrogen, in which case the molécule reverts to the simplest primary a-aminoacid, called glycine.

The material containing the CPM and one or more NCEs may comprise an ore or an ore concentrate (herein coilectively referred to as “ore” for easy discussion). The material may alternatively comprise a waste material, including mining waste such as tailings, industrial waste such as fly ash, or electronic waste (“e-waste”), such as computers, keyboards, télévisions, mobile phones, etc. While the following discussion will focus on the use of the sélective recovery process for treating ores, it is to be understood that it is not limited thereto and is applicable to ail solid CPM-containing materials.

The CPMs most often occur as sulfide minerais in ores, although oxides, arsenides, sulfoarsenides, native metais, sulfates, carbonates, chlorides, silicates, hydroxylated-salts and

- 7 hydroxide minerais of the CPMs may also occur commonly. The naturel minerais of these CPMs are often hosted as small minerai grains in silicate host rocks (the matrix), that also contain métal oxides and carbonates of the alkaline earth metals and the Lithophile (Ip) metals (metals in Groups 3-6). In hydrometallurgy these lithophile (Ip) and reactive metals are either quite refractory to leaching in moderately alkaline solution or, if soluble, are unwanted in leach liquors where CPMs from Group 9-12 are targeted for économie recovery. As used herein, a “moderately alkaline solution (MAS)” refers to aqueous solutions with a pH range of between 7 and 13. These minerais of the lithophile (Ip) and more reactive siderophiles (MR sp) are often wholly or partially acid soluble. In addition many of these lithophiles also become soluble in strongly alkaline (pH>13) solutions.

The minerai groupings, as pertaining to the invention, therefore are:

• Lithophile metals and their minerais (Ip) • Less reactive siderophile (LR-sp) • More reactive siderophile (MR-sp) • Chalcophile metals and minerais (cp) • Chalcophile Metals including Less reactive siderophiles (CPM = cp + LR-sp)

It would be therefore be désirable to hâve a process that selectively leaches the CPMs in a moderately alkaline solution (MAS) in a pH range of 7<pH<13, whilst not dissolving the MR sp and Ip components, which would lead to uneconomic reagent consumption and treatment costs.

In addition, it would also be désirable if the reagent used to perform the leaching of the CPMs could be recovered in a simple and économie manner, and recycled for reuse.

Moreover, it is désirable that minerais from metals in Groups 1-8 do not significantly react and consume leaching reagents or alter pH or oxidation- réduction potential (“ORP” or “Eh) of the reacting System. Once leached, it is also désirable that CPMs can be recovered from solution using a range of processes known to those skilled in the art. In addition, due to the cost of most reagents, it is désirable that recovery of the reagents can be achieved without dégradation of the reagents. This may comprise the reagents being retained or restored to their original state using either much cheaper reagents or energy (such as in electrowinning).

Accordingly, there is disclosed a process for the sélective recovery of at least one CPM by leaching with an alkaline solution containing an amino acid or a sait thereof. The sait may be an alkali métal sait, for example, a sodium or potassium giycinate. Alternatively, the sait may be an alkaline earth sait (for example its calcium sait).

The alkaline solution may contain more than one amino acid or sait thereof.

- 8 The alkaline solution may also contain an oxidant, such as where the CPM is présent in a form/compound/mineral that requires oxidation to obtain the CPM in its oxidised state and any bonded non-metal or semi-metal (such as sulfur, arsenic, bismuth, antimony) into its oxidised anionic State (for example, but not limited to, sulfur to sulfate, arsenic to arsenate, antimony to antimonite) Conversely, where the CPM is présent in an oxidised form, such as an carbonate, oxide, sulfate or hydroxide, an oxidant may not be required.

The alkaline solution should preferably be substantially free of intentional additions of detrimental species such as thiosulfate or ammonia containing species, for the reasons set out under “Background Art” above. In most cases, this will mean that the alkaline solution is substantially free of those detrimental species. However, there may be cases where those detrimental species arise in situ in solution due to unintended reactions in solution.

Accordingly, in a second aspect there is provided a process for the sélective recovery of at least one Chalcophile Group Element (“CPM”) as herein defined from a material containing the CPM and one or more non Chalcophile Group Eléments (“NCE) as herein defined, said process including:

(i) contacting the material with an alkaline lixiviant that is substantially free from added thiosulfate or ammonia and that contains an amino acid or sait thereof in order to selectively leach the CPM from the material to produce a CPM containing leachate and a NCE containing residue; and (ii) recovering the CPM from the leachate.

While the amino acid or amino acid sait is an effective lixiviant on its own, the alkaline solution may additionally include a small amount of a catalyst which enhances the leaching function of the amino acid or its sait and/or may reduce the température requirements for the leaching process. Thus the primary lixiviant is still the amino acid or its sait. The catalyst may comprise one or more of the following species: iodine and/or iodide mixtures, bromine and/or bromide mixtures, thiourea, copper salts, and cyanide in its various salts, or mixtures of these species. In one embodiment, the catalyst comprises a cyanide sait (such as sodium cyanide). In another embodiment, the catalyst is the sparsely soluble copper cyanide (CuCN) which become soluble in an alkaline glycine environment and catalyses the leaching of the CPM. The catalyst may increase the rate of leaching the CPM. The catalyst may particularly increase the rate of leaching of precious metals, as well as chalcophile base metals.

In ail cases where the catalyst is added, the weight ratio of amino acid to the catalyst is greater than 2:1 (conversely, the catalyst preferably does not make up more than 33 weight% of

- 9 the combinée! mass of amino acid and catalyst). The weight ratio of amino acid to the catalyst may be greater than 3:1. However, typically the ratio of amino acid (e.g. glycine) to the catalyst is higher, such as a minimum of 10:1. In an embodiment, the minimum weight ratio of amino acid to the catalyst is 100:1. The weight ratio may be as high as 1000:1, particularly where high ratios of CPM base metals (e.g. Ni, Cu, Co, Zn, Pb) to CPM precious metals (Au, Ag Pt, Pd, Rh, Ir) are présent.

The catalyst concentration in the alkaline solutions may be a maximum of 300 ppm (or 300 milligram / kg solution) whereas typical minimum amino acid concentrations are greater than 1200 milligram per kg solution. As catalysts can be expensive, irrecoverable ortoxic, it is normally aimed to minimise their use in a mixed System insofar as only to increase the rate of the amino acid leach reaction. In contrast, the amino acid is the lixiviant and “carrier” of the métal in solution and therefore needs to be présent in greater concentration. Accordingly, the catalyst is présent in lesser quantity than the amino acid lixiviant.

In an embodiment, the sélective leaching of the CPMs leaves the bulk of the pre-existing NCE minerais of the host rock/ore/concentrate in the leach residue.

In an embodiment, the leaching may take place “in situ or “in place” (i.e., in the underground rock mass through use of a well-field). In another embodiment, the leaching may comprise dump leaching, such as by leaching blasted but uncrushed particles typically smaller than 200 mm. In another embodiment, the leaching may comprise heap leaching, such as by leaching coarse crushed particles typically smaller than 25 mm. In another embodiment, the leaching may comprise vat leaching, such as by leaching fine crushed, particles typically smaller than 4 mm. In another embodiment, the leaching may comprise agitated tank leaching, such as by leaching milled matériel having particles typically smaller than about 0.1 mm/100 micromètre. In another embodiment, the leaching may take place in pressure leaching autoclaves and may comprise leaching particles that are typically smaller than 100 micromètre.

The process involves the use of amino acids or their salts (especially alkali métal / alkaline earth salts). The amino acid may comprise an alpha amino acid. The amino acid may comprise one or more of Glycine, Histidine, Valine, Alanine, Phenylalanine, Cysteine, Aspartic Acid, Glutamic Acid, Lysine, Méthionine, Serine, Threonine, and Tyrosine.

In an embodiment, the amino acid may be glycine (Gly) (chemically defined by the formula NH2CH2CO2H). Glycine is a simple amino acid that is easy and cheap to produce on an industrial scale with the highest probability of industrial use. The following discussion will focus on the use of glycine and its salts as the amino acid, however, it is to be understood that the invention

- 10 extends to other amino acids. “Glycine” may refer to the amino acid commonly known by this name, or any of its alkaline métal salts (such as sodium or potassium glycinate). Other common names for glycine include aminoacetic acid or aminoethanoic acid. In an embodiment, the amino acid is provided in an aqueous solution of an alkali, or alkaline earth, métal hydroxide (such as sodium or potassium hydroxide or calcium hydroxide).

Glycine and/or its salts are the preferred amino acid because of their:

• large scale production and bulk availability;

• low cost of production;

• ease of transport;

• low price; and • low molecular weight.

While other amino acids may be used instead of (or in addition to) glycine, they are typically more costly and any performance benefit often cannot be justified by the additional costs that are incurred. Glycine has a very high solubility in water, as do the CPM glyclnates. It is thermally stable, and stable in the presence of mild oxidants such as dilute hydrogen peroxide, manganèse dioxide and oxygen. It is non-toxic and many of the CPM glycinates hâve low or lower toxicity (compared their équivalent cyanides, halides or sulfates). It is an environmentally safe and stable reagent. The ability to easily regenerate, recover and reuse glycine in alkaline solutions is one of its most important attributes from an économie perspective. The alkaline nature of the leach allows cheap materials of construction such as mild Steel.

The amino acid concentration in solution may vary from 0.1 to 240 grams per litre. The amino acid concentration may be a minimum of 3.75 grams per litre and in an embodiment may be a minimum of 16 grams per litre. The maximum amino acid concentration may be 60 grams per litre and in another embodiment, the amino acid concentration is a maximum of 37.8 grams per litre.

The source of alkalinity in the alkaline solution may comprise an aqueous solution of an alkali métal hydroxide, such as sodium or potassium hydroxide. The alkali métal hydroxide concentration may be a minimum of 0.4 grams per litre, such as from 0.9 grams per litre. The maximum alkali métal hydroxide concentration may be 17.4 grams per litre, and in an embodiment it is a maximum of about 10 grams per litre.

In another embodiment, the alkaline solution may comprise an aqueous solution of an alkaline earth hydroxide, such as calcium hydroxide. The alkaline earth métal hydroxide concentration may be a minimum of 0.8 grams per litre, such as from 1.5 grams per litre. The maximum alkaline earth métal hydroxide concentration may be about 20 grams per litre, and in an

- 11 embodiment it is a maximum of about 15 grams per litre.

The source of alkalinity does not include ammonia, which as noted previously, is substantially absent from the alkaline solution due to toxicity and solubility issues.

The sélective recovery process may be conducted over a range of températures. In an embodiment, the process is conducted at ambient or mildly elevated températures. The process may be conducted from -10 °C to 200 °C, such as from 0°C to 100°C. In one embodiment, the process is conducted at a température between 25 °C to 65°C.

The sélective recovery process may conveniently be conducted at atmospheric pressure (from mean sea level to low atmospheric pressures at altitudes of around 6000 meters above mean sea level). However in some embodiments, the process may be conducted at elevated pressure or at a pressure below atmospheric.

In an embodiment, the oxidant may comprise a mild oxidant. The oxidant may comprise an oxygen containing gas, such as oxygen or air. In another embodiment, the oxidant may comprise a peroxide, such as a dilute aqueous solution of hydrogen peroxide.

The leaching step (i) may occur in the presence of variable amounts of dissolved oxygen which may, for example, be provided via aération or oxygénation. Dissolved oxygen (DO) concentrations may vary from 0.1-100 milligrams per litre in solution, such as from 8 to 30 mg/L, depending on the oxygen demand (OD) of the CPMs in solution and the pressure of the leaching process.

Alternatively, or in addition, the oxidant may comprise a peroxide, such as hydrogen peroxide. The concentration of peroxide may be greater than 0.01%, such as at least 0.5%. In an embodiment, the peroxide concentration may be less than 5%, such as less than 3%.

The leaching step (i) is conducted under alkaline conditions. In an embodiment, the process is conducted using a moderately alkaline solution having a pH range of between 7 and 13. In another embodiment, the pH range is between 7 and 11.5. In another embodiment, the pH is between 8 and 10.

The process can be used with various water types, i.e. tap water, river water, sea water, as well as saline and hypersaline brines with significant dissolved salts containing sodium, magnésium, calcium, chloride, sulfate and carbonate ions in solutions.

The CPM containing material and the alkaline lixiviant react to leach the CPM into the leachate. Without wishing to be limited by theory, it is believed that leaching forms a métal glycinate complex (MGC), or a métal amino-acid complex (MAAC). As used herein, the term MGC Is also meant to include MAAC. The MGC refers to glycinate complexes of the CPMs, as opposed

- 12 to the NCEs. Although métal glycinate complexes of the NCEs exist in the acidic région (pH<7), these NCEs are not readily complexed in the MAS pH région (ie 7 to 13), allowing sélective leaching of the CPMs.

The ratio of solid CPM containing material to the alkaline lixiviant can vary. For example, in the case of in-situ leaching, the solid to liquid ratio is likely to be high, such as up to 100:1. In agitated tank leaching the solid to liquid ratio is likely to be much lower, such as around 40:60, or 2:3, on a weight basis (i.e. 40 kg of solid to 60 kg of aqueous solution). In the case of leaching minerai concentrâtes, the ratio may be even lower, such as around 10 kg of solids per 90 kg of aqueous solution (ie, 1:9).

It may be bénéficiai to add copper salts (e.g. cupric sulfate) to the leachant during the leaching step. This addition can be bénéficiai when the CPMs are présent in the ore as an oxidisable form, such as native metals or sulfides. However, it may not be bénéficiai if the CPMs are not oxidisable, such as if they are présent as oxides, carbonates or silicates. Concentration of initial copper in solution from low levels up to 1 weight% (at the start of leaching) can be used. It has been found that the copper glycinate has two stable complex forms, both the cuprous and cupric glycinate, as by the following reactions:

Cu²⁺ + (H2NCH2COOy θ Cu{NH2CH2C00y, log K = 8.6 Cu²⁺ + 2(H2NCH₂C00y θ Cu(/VH₂CH₂COO)₂ , log K = 15.6

Cu⁺ + 2(H₂NCH₂C00y w Cu(NH₂CH₂COOy , log K = 10.1

The stability of both the cuprous (monovalent) and cupric (divalent) States créâtes a very useful redox-couple, whereby the cupric glycinate complex can serve as an oxidant to oxidise minerais (particularly CPM metals and sulfides), itself being reduced to the cuprous glycinate form which, in turn, gets re-oxidised to cupric glycinate by air, oxygen (or oxygen-enriched air), hydrogen peroxide or alternative oxidants such as manganèse dioxide. The minerai to be leached therefore reduces the cupric glycinate to it cuprous form, and a convenient oxidant, such as air, restores the cupric glycinate oxidant. The use of copper salts is not mandatory in this process, but may accelerate the leaching reactions.

The NCE containing residue may be separated from the CPM containing leachate using such solid-liquid séparation steps as filtration, centrifuging or sédimentation. Thickening may be conducted before solid-liquid séparation.

The clarified liquid from the thickener and the filtrate can be combined for métal recovery

- 13 in step (ii).

Once leached, CPMs may be recovered from aqueous solution in step (ii) using one of a range of extraction steps. The CPMs are typically présent in the leachate as amino acid (glycinate) complexes. The recovery step may also include régénération of the glycine lixiviant. The amino acid can then be recycled and reused, if desired, after any required pH correction The regenerated species may be either free aqueous glycine or its aqueous glycinate anion. This step encompasses ail methods which precipitate/transfer the CPM into another concentrated phase whilst regenerating the glycine lixiviant in the MAS range.

A first possible recovery step (ii) may comprise Chemical recovery of the CPM such as by recovering the métal in a solid State (such as electrowon métal, hydrogen precipitated métal powders, or as a métal sulfide precipitate). The solution, stripped of its CPM is now referred to as the “barrens” or barren leach solution (BLS). The recovery step enables release of the amino acid in solution for reuse. Removal of the CPMs and/or release of the glycine may occur as stated above through the formation of various CPM solid products directly from the prégnant leach solution (PLS).

A second possible recovery step (ii) comprises recovery of the CPMs through an intermediate upgrading step where the CPM is adsorbed onto, or dissolved into, another waterinsoluble (non-aqueous) phase, such as ion-exchange (IX) resins, solvent extraction (SX) organic solvents, granular activated carbon (GAC), molecular récognition (MR) resins, or coated adsorbents (CA’s), which may include polyethylene immine (PEI) coated diatomaceous earth, ferrofluids, and CPM-selective organic adsorbents grafted onto solid matrices.

Once CPMs are adsorbed onto/dissolved into the upgrading phase (which has a very high affinity for the CPM so that it removes/strips the CPM from the MGC in solution and releases the glycine/glycinate anion into solution), the CPM-enriched non-aqueous phase can be stripped to release the CPM again into another aqueous solution at a much increased concentration. The refined aqueous solution (RAS) can then be subjected to electrowinning, hydrogen gas précipitation, hydrolysis-precipitation or précipitation as CPM sulfides (single or mixed with other CPMs). The regenerated glycine will be in the BLS, but not necessarily in the RAS. The benefit of the second possible recovery step is that it allows refining of the targeted métal from the glycinate solution, should it be preferred.

The recovered métal can then be removed by an appropriate means. One example is to remove as electroplated / electrowon métal (EWM) from a cathode of an electrolytic cell (e.g. for Co, Ni, Cu, Ag, Zn, Cd, Pt, Pd, Rh, Ir, Au and Hg). In another example, removal is by précipitation as a mixed métal precipitate (MMP) using hydrogen gas (typically Ni, Cu, Pd, Ag, Pt, Au) and

- 14 subséquent métal filtration. In another example, removal is as a sulfide precipitate through addition of hydrogen sulfide, alkali métal sulfides or alkali métal hydrogen sulfides to form stable mixed métal sulfide précipitâtes (MSP). MSP and MMP are convenient and sought-after process intermediates for further processing, such as industrial smelting (metals such as Co, Ni, Cu, Zn, Ag, Cd, Hg, Pb and platinum group metals). The métal sulfide or precipitated metal/alloy powders are removed from solution using sédimentation, centrifuging or filtration. This EWM, MSP or MMP stream is the saleable métal (or métal sulfide) stream.

The process may further include a preconditioning step prior to the leaching step (i). This step is optional and the need for it may dépend on the type of material being treated. The preconditioning step may be described in co-pending patent application entitled “Preconditioning Process” in the name of applicant, the entire disclosure of which is incorporated herein by reference. The preconditioning step, treats a passivating coating on the métal containing material, with an alkaline solution of sulfurous acid and sulfite ions. The passivating coating may comprise elemental sulfur, iron oxide and/or iron hydroxide. The preconditioning step enables réactivation of the passivated surfaces of the ore to enhance leaching.

Where the alkaline leachant comprised a hydroxide solution, the process may further include a step of regenerating or restoring the hydroxide after the recovery step (ii). In the case of regenerating/restoring alkali métal hydroxide, this may be effected by addition of lime (as either calcium oxide or calcium hydroxide) to the barren leach solution. Alternatively, régénération may be effected by addition of caustic soda (NaOH). Régénération may be désirable, for example, where the original CPMs occurred mostly as sulfide minerais, and the sulfur in the sulfide minerai is oxidised to a mixture of sulfite (SO₃)²' and sulfate (SO₄)²' ions in solution. Some minor dissolution of silicate minerais might also hâve led to some silica dissolution as alkali métal silicates. The addition of lime or quicklime or slaked lime or milk of lime reacts with any one or more of alkali metals sulfates and sulfites, carbonates, phosphates and silicates in the barren leach solution to precipitate a mixed precipitate including one or more of insoluble or poorly soluble hydrated calcium sulfates (e.g. gypsum and anhydrite), calcium sulfite, carbonates (calcite, aragonites), phosphate (apatite, hydroxyapatite, fluorapatite or chlorapatite), phosphogypsum, calcium silicate (wollastonite) and dicalcium silicate. Often traces of lithophile metals which might hâve dissolved during the primary leaching stage are also co-precipitated with this mixed calcium rich precipitate. In the process, alkali métal hydroxide (sodium or potassium hydroxide) is regenerated and the pH for leaching is re-established, prior to recycle to the leach reactor (heap/tank/in-situ, etc.). In the case where caustic soda solution is added instead of lime, the sulfates/sulfites may need to be removed with an alternative technology such as nanofiltration, to prevent accumulation in the recycle. Other combinations of lime and caustic are also

- 15 possible, e.g. to precipitate the sulfates with lime and do the final pH adjustment with caustic soda.

The calcium rich mixed precipitate may then be separated by solid-liquid séparation such as filtration, centrifuging or sédimentation, preceded by thickening or counter current décantation, if necessary. In this manner, the barren leach solution may hâve its amino acids regenerated as well as its hydroxide regenerated for reuse.

The regenerated hydroxide and/or amino acid containing aqueous solution, herein referred to as the restored/regenerated barren solution or “RBS”, may then be recycled to the leaching step (i). Small amounts of sodium phosphate may be used to remove the last traces of calcium in the RBS, if required.

CPM sulfide minerais often hâve arsenic présent in small but significant amounts, in minerai forms such as enargite and arsenian pyrite and arsenopyrite (among others). Arsenic can be problematic in alkaline solutions as it remains quite stable in solution (as arsenite/arsenate) and may cause environmental problems. To prevent the accumulation of arsenic in the PLS, BLS and RBS, a number of potential options exist, such as:

o Sélective removal from the RBS using nano-filtration of calcium arsenite/arsenate either from the main process stream or a bleed stream from the main stream.

o Addition of a small amount of lead nitrate which will precipitate the arsenic as the highly insoluble lead arsenate.

o Removing a bleed solution of the RBS (sufficient to prevent the accumulation of arsenate) and acidify the solution to mildly acidic (pH of around 3) and precipitate the arsenic as iron/ferric arsenate (the minerai scorodite) using ferrie chloride or ferrie sulfate. The whole RBS solution does not hâve to be treated, only a small bleed stream.

o Précipitation as sodium arseno-sulfide with elemental sulfur and NaSH.

If environmentally deleterious and toxic mercury, cadmium and/or thallium are présent in the ore, they may be also solubilised in the alkaline glycine solution. If the CPMs are recovered by précipitation as sulfides (using, for example, hydrogen sulfide, sodium hydrogen sulfide (NaSH) or sodium sulfide), cadmium, mercury and thallium sulfides may also co-precipitate. If so, they may become penalty éléments if the mixed chalcophile métal sulfide précipitâtes are sold to smelters and refiners. However, these downstream smelters and refiners often hâve sufficient treatment and recovery technologies to remove and recover these more toxic CPMs. Hydrogen précipitation of CPMs from solution may lead to a MMP contaminated with some of the unwanted/deleterious

- 16 CPMs. However, sélective SX, IX and the use of sélective adsorbents may limit the deportment of the deleterious CPMs so that these metals do not contaminate the targeted CPMs, if intermediate upgrading and refining steps are used prior to electrowinning or précipitation of the targeted CPMs.

The disclosed sélective recovery process described above can be applied to most minerai resources and process intermediates containing CPMs, but has particular benefits where the host rock / material has significant amounts of alkaline minerais such as calcite, dolomite, trôna and other acid consuming minerais (in addition to the conventional rock forming silicate minerais), which can make conventional acid-based leach processes uneconomical. It also has particular use for ores with significant iron minéralisation, be it sulfide (e.g. pyrite, pyrrhotite, marcasite), oxide (hématite, magnetite, maghemite), hydroxide and hydroxi-oxide (goethite, limonite, iron hydroxide), of basic sulfate salts (such as jarosites). These iron minerais would hâve partially leached in acidic medium, whilst remaining quite stable in alkaline medium, and not consuming any significant amounts of reagents (in alkaline medium). The CPMs form stable MGC's, whilst the NCE’s do not form stable metal-glycinate complexes allowing differential dissolution and précipitation.

In acidic leach processes aluminium, magnésium and silica often dissolve to a significant extent. Magnésium is very difficult to remove from aqueous solution and aluminium and dissolved silica may lead to the précipitation of gelatinous précipitâtes with small changes in pH, leading to very difficult solid-liquid séparation and significant prégnant leach solution (PLS) losses with the filter residue and creating environmentally hazardous leach residues. Conversely, leaching in alkaline media prevent the précipitation of gels, whilst magnésium and alumina are not significantly dissolved if the alkaline pH is kept between 7 and 13, or in the MAS range. Minor amounts of silica do dissolve but no gel formation risk is présent. The dissolved silica (as silicates) can be precipitated as a crystalline calcium silicate during the lime treatment stage.

BR1EF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the apparatus and method as set forth in the Summary, spécifie embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is the Goldschmidt Periodic Table;

Figure 2 shows a flowsheet for a first embodiment of a sélective recovery process;

Figure 3 shows a flowsheet for a second embodiment of a sélective recovery process.

- 17 Figure 4 is a graph of % copper extraction vs time for chalcopyrite leaching in alkaline glycine solutions at leaching conditions: 0.1 M Glycine, Room Température (23°C), pH 10.5, controlled dissolved oxygen (DO) level.

Figure 5: is a graph of % copper extraction vs time for chalcopyrite concentrate leaching for different peroxide concentrations. Leaching conditions: 0.1M glycine, % H₂O₂, pH 10.5, 60 °C.

Figure 6: is a graph of % copper extraction vs time for chalcopyrite concentrate leaching at different températures. Leaching conditions: 0.1 M glycine, 2.5% H₂O₂, pH 10.5

Figure 7: is a graph of Zn concentration (mg/L) vs time for sphalerite leaching in glycine solutions. Conditions: Glycine: 60 g/l, H₂O₂: 0.48%, Minerai: 10 g/l.

Figure 8: is a graph of Pb concentration (mg/L) vs time for galena leaching in glycine solutions at two different pH values. Conditions: Glycine: 60 g/l, H₂O₂: 0.48%, Minerai: 10 g/l.

Figure 9 is a graph of % copper extraction vs time for malachite leaching in glycine solutions at different peroxide concentrations.

Figure 10 is a graph of % copper extraction vs time for malachite leaching in glycine solutions at various glycine to copper ratios.

Figure 11 is a graph of % copper extraction vs time for chalcopyrite leaching in alkaline barren glycine solutions at controlled DO (20 ppm), room température (23°C) and pH 10.5.

Figure 12 is a graph showing the extraction of gold from a gravity gold concentrate, using cyanide only compared to using glycine in alkaline solution with copper cyanide as a catalyst.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

An example of a first embodiment of a flowsheet for the présent process to treat CPM containing ores in the MAS range, where the CPM may be mineralised in a mixture of minerai types but with sulfide CPM minerais as the prédominant type of CPM minéralisation, is shown in Figure 2. Figure 2 shows the process flowsheet 10 for the treatment of ores/concentrates 11 containing chalcophile metals (CPMs) with significant CPM sulfide minéralisation. The ores/ concentrâtes 11 may be pre-treated such as by ultrafine grinding and/or with alkaline preconditioning prior to glycine addition, which may enhance the effects of leaching. Leaching 12 is conducted using NaOH 14 (or KOH) and glycine 16 in the presence of an oxidant 18 (eg, air/O₂ or H₂O₂). The leach slurry 20 is thickened 22 and filtered 24 to produce a filtered leach residue 26 and prégnant leach solution 28. The PLS 28 is treated in a first précipitation step 30 for métal recovery and glycine recovery by NaSH 32 or Na₂S or H₂S addition. The resulting CPM sulfide product slurry is again thickened 34 and filtered 36 to produce the final CPM sulfide product 38.

- 18 The filtrate 40 is treated with hydroxide 44 (eg, NaOH, Ca(OH)₂) in a second précipitation step 42 for calcium sulfate/sulfite précipitation.

Figure 3 shows a second embodiment of a flowsheet for treating CPM containing ores or concentrâtes in which like référencé numerals refer to like steps. Figure 3 shows how the process flowsheet 110 can be simplified for CPM-containing ores which do not hâve significant CPM sulfide minéralisation, but rather in the form of oxides, carbonates, halides, hydroxides, etc. When CPM is mineralised predominantly in non-sulfide forms, the flowsheet may be simplified as shown in Figure 3. The addition of oxidant (118) may be optional, depending on the degree of oxidation of the CPM containing ore/concentrate. Another différence from the first embodiment 10 is that the second embodiment 110 does not include the second précipitation step 42, Again, the métal recovery and glycine recovery is by NaSH addition.

In the second embodiment 110, lime suspension and/or milk of lime (Ca(OH)₂) 114 can be added directly to the leach step 112 (instead of sodium/potassium hydroxide as in the first embodiment 10). The pretreatment step may also be eliminated and caustic soda (sodium hydroxide) régénération may be eliminated. As calcium hydroxide is normally a less expensive reagent than alkali métal hydroxide (such as sodium hydroxide), and no sulfide is oxidised to sulfate and sulfite, no caustic régénération and calcium sulfate/sulfite précipitation is required.

The CPM Sulfide Précipitation step in Figures 2 and 3 can be replaced by any of the following:

• Direct electrowinning to crude electroplated métal (at cathode).

• Hydrogen précipitation of métal granules/powders (hydrogen added in pressurised reactor vessel).

• Adsorption onto GAC, IX, MR resin, or into SX organic solvent after which the CPM is stripped/eluted into RAS which can again be recovered by CPM Sulfide Précipitation, to produce MSP, hydrogen précipitation to produce MMP or electrowinning to produce EWM, or other métal réduction or précipitation steps.

It is expected that lime consumption for the présent process would be similar or less than the lime amounts used to neutralise acidic taiiings from acid leach processes.

EXAMPLES

Non-limiting Examples of a process for the sélective recovery of at least one Chalcophile Group Element are described below.

- 19 Example 1. Chalcopyrite (CuFeS₂) leaching

Naturel Chalcopyrite concentrate was leached in alkaline glycine solutions. The chalcopyrite had the following composition (wt %):

Table 1: Concentration of metals in chalcopyrite

Element	Cu	As	Fe	Si	Ni	Al	Co	Pb	S
Conc. (%) in chalcopyrite	22.6	0.167	23.1	4.27	0.005	0.293	0.076	0.072	23.1
The effect of various	evels o	oxidant in the lix	viant is shown in Figures 4 and 5. Figure 4

shows the effect of increased dissolved oxygen (such as by injection of air or oxygen). The effect of varying hydrogen peroxide is shown in Figure 5. Both figures indicate increased copper dissolution with higher amounts of oxidant in solution. For example, at high dissolved oxygen (DO), or higher concentrations of oxidizing agents such as peroxide, the rate of copper extraction is higher than using air only as oxidant. Oxygenated solutions with high DO lead to faster extraction rates than with air alone.

The effect of température on leaching is shown in Figure 6. There is a steady increase in copper solubility as the température of leaching increases from around room température to 60 °C. Higher températures therefore increase the rate of leaching of copper from its minerais.

The dissolution of copper and impurities after leaching is shown in Table 2.

Table 2: Leach solution concentration of metals after leaching chalcopyrite in alkaline glycine solution.

Element

Cu

As

S

Fe

Si

Ni

Co

Pb

K

Mn

Mg

Al

Conc (mg/l)

1243

9.13

952

11.4

2.76

<0.2

7.6

10.1

15.6

<0.2

5.2

<0.2

It is clear that whilst the CPM copper dissolves in the alkaline glycinate solution, the NCEs:

iron, magnésium, aluminium, Silicon do not dissolve to a great extent.

Example 2. Leaching of sphalerite (zinc sulfide)

Sphalerite (zinc sulfide) was leached in alkaline glycine solutions under bottle rail condition with air as oxidant. The extraction of zinc as the leach proceeds over time for two different pH’s are shown in Figure 7. Initially higher dissolution of zinc is évident at pH of 11.5, although the overall rate is slower than that at pH 9, meaning the same overall amount of Zn is leached after around 100 hours. It therefore appears that the lower pH favors Zn extraction kinetics, but only initially.

- 20 Example 3. Leaching results from mixed galena (lead sulfide):

Galena (lead sulfide) was leached in alkaline glycine solutions under bottle roll condition with air as oxidant. The extraction of lead as the leach proceeds over time for 2 different pH’s are shown in Figure 8. The Conditions of leaching were: Glycine: 60 g/l, H₂O₂: 0.48%, Minerai: 10 g/L It can be seen that significantly higher Pb extraction was achieved at a pH of 9 as compared with a pH of 11.5. Lead extraction was therefore favored by slightly lower pH, aithough still remaining within MAS. Operation of the disclosed process within the MAS is very important to retain selectivity over the NCE’s. If operation moves into the acidic région (eg, pH<7) it can start to dissolve metals and minerais indiscriminately, which is undesirable.

Example 4. Leaching of malachite (copper carbonate):

A sample of natural malachite with hématite (Fe₂O₃), goethite (FeO(OH)) and quartz contaminants was leached under various glycine concentrations. A quantitiative X-Ray diffraction diffractogram confirmed the mineralogy of the malachite ore to be:

XRD- Analysis	Phase	Goethite	Hématite	Malachite	Quartz	Amorphous Content
weight %	1.7	3.3	66	16.7	12

The effects of peroxide concentrations and glycine to copper ratios on copper extraction are given in Figures 9 and 10. Figure 9 shows copper extraction from malachite leaching in glycine solutions at different peroxide concentrations. The effect of various glycine to copper ratios on malachite leaching is given in Figure 10. When peroxide is used as an oxidant, copper extraction is enhanced with increasing peroxide concentration from 0.1% to 1% peroxide. In the System without peroxide, air was still présent as an oxidant and under the particular conditions illustrated, the steady ingress of air was effective for copper extraction. Figure 10 shows an increase in solubility as the glycine concentration increases from 3:1 to 8:1. While increasing the glycine: CPM ratio favors extraction of copper intialiy, the final extraction of copper is sufficient at a 50% stoichiometric excess.

Example 5. Leaching of cobalt-bearing nickel latente

This example gives the end resuit after 90 hours of leaching in glycine solution in the MAS pH range, and shows the dissolution of CPMs and the relative non-dissolution of NCE’s:

- 21 Table 3: Leach solution concentration of metals after leaching latérite in alkaline glycine solution.

Category

CPM

NCE

NCE

NCE

CPM

NCE

NCE

NCE

NCE

NCE

NCE

CPM

NCE

NCE

Element

Co

Ca

Mg

Fe

Ni

SI

Zr

Al

Sr

Ti

Ba

S

Cr

Mo

Solution Concentration (mg/l)

so

2.5

0.3

3.0

77.0

2.0

<0.02

3.0

<0.02

<0.02

0.4

250

0.1

<0.02

Table 4. The latérite had the following composition (wt % for each element):

Si	Mg	Fe	Ni	Al	Ca	Mn	Cr	Zn	Na	Cu	Co	Ti
9.29	6.91	30.73	1.55	2.71	0.17	0.55	1.44	0.03	0.03	0.01	0.08	0.05

It is clear that while Silicon, magnésium, iron and aluminium predominate while cobalt and nickel are at low concentration levels in the latérite ore, the final leach solution contains mostly nickel and cobalt in solution, showing the sélective leaching of these éléments.

Example 6. Précipitation and recovery of copper from copper glycinate solutions with NaSH (sodium bisulfide / sodium hydrogen sulfide) and glycinate/glycine reuse for leaching

Stoichiometric addition of NaSH solution to a copper glycinate solution, with NaSH in a 1:1 molar ratio to the copper in solution, lead to précipitation of 99.1% of the copper to form a covellite precipitate, as confirmed by X-Ray diffractogram.

The copper can be recovered from glycine solution by sulfide (NaSH) précipitation. Sulfide ions hâve been added to the prégnant liquor in different Cu:S²‘ molar ratios in order to recover copper from the glycine solution. The copper recovery reaches up to 99.1% as copper sulfide at Cu:S²' molar ratio of 1: 0.70 in only 10 minutes contact time. Table 5 shows the copper concentration in the leach solution before and after NASH précipitation. The barren solution after NASH précipitation containing 12.5 mg/L copper-glycinate has been used to leach copper from fresh chalcopyrite concentrate. The barren solution was found to leach copper from chalcopyrite at a similar rate to that of the fresh solution (Figure 11 ), illustrating the ability to reuse the solution. The conditions of leach in Figure 11 are: alkaline barren glycine solutions at controlled DO (20 ppm), room température (23°C) and pH 10.5.

Table 5: Copper concentration in the leach solution before and after sulfide (NASH) précipitation.

Sample ID	Cu, mg/L
Before précipitation	1243
After précipitation Cu:S2' Molar ratio of 1 : 0.70	11.5
After précipitation Cu:S2'Molar ratio of 1 : 0.50	226.3

Example 7. Recovery of copper from copper glycinate leach solution uslng solvent extraction and stripping.

This serves as an example of the extraction of copper (or other CPMs) from its glycinate 5 solution using solvent extraction and stripping. Sometimes, the low copper (or other CPMs) concentration in the final leach solution from chalcopyrite may not be at a suitable concentration for copper recovery by either electrowinning or sulfide précipitation. The application of solvent extraction (SX) may be required to get high copper (or other CPMs) concentration to be suitable for any further copper (or other CPMs) recovery processes. Solvent extraction (SX) experiments show that copper glycinate (or other MGC’s) can be easily extracted from the alkaline aqueous medium (Aq) using a 10% (v/v) LIX 84I in ShellSol D70. Copper extraction reaches up to 99.4% and high copper extraction was obtained at different equiiibrium pHs. The stripping of the organic phase (Or) in sulfuric acid shows also that ail the copper can be stripped back in sulfuric acid medium (so that it can be electrowon using conventional electrowinning technology if required).

Table 6 shows the copper extraction from aqueous medium and the stripping of copper from organic medium.

Table 6 Copper extraction from copper glycinate aqueous (Aq) solution using LIX 841 at 40 °Cand 1:1 Or/Aq ratio.

Concentration in Aq, (mg/L)	Extraction, (%)	Stripping, (%)
Sample ID	Equip. pH	Cu	Cu	Cu
Feed	11.5	3596
Test 1	8.8	43.9	98.8	-
Test 2	9.4	65.6	98.2	100

Test 3

10

22.3

99.4

100

Example 8. Sélective leaching of platinum group metals, nickel and copper from a PGM ore

An ore material containing nickel, copper and platinum and having the Chemical and mineralogical composition shown in Table 7 was ground to a particle size of P80= 67 micron. Samples were leached in an alkaline glycine solution at a solids density of 10wt% whilst stirring the solution at a rotational rate of 600 rpm and under varying conditions of glycine concentration, solution température, pH and oxygen flow rate. The results of four leaches are identified as Experiments 1 to 4 and are set out in Tables 8 to 11, respectively.

Table 7 Chemical and Mineralogical Composition of Ore Material

Chemical analysis	Drum 1	Drum 2	Mineralogical analysis	Drum 1	Drum 2
Content (%)	Content (%)
Fe	13.50	13.60	Major phases
Cr	9.30	10.40	Chromite (FeCr2O4)	73.89	78.12
Mg	6.9450	7.18	Chlorite - Clinochlore [(Mg,Fe,Li)6AISi3O10(OH)8] [(Mg,Fe2+)5AI2Si3O10(OH)8]	16.55	11.16
Al	5.1100	5.35
Ca	0.4070	0.42
Ti	0.2630	0.3190
Na	0.02375	0.0310
Ni	0.2950	0.31
Mn	0.2310	0.23
Zn	0.1170	0.12
Cu	0.0648	0.0646
Si*	3.61	2.64
S*	0.37	0.78
C*	0.04	0.11
V	0.0551	0.0609
Co	0.03175	0.0314
As	0.0157	0.0185

Content (g/t)	Minor phases	Content (%)
P	31.35	51.4	Olivine (Mg2+,Fe2+)2SiO4	3.63	3.23
Ga	33.6	34	Ferrotschermakite Ca2[(Fe2\Mg)3AI2](Si6AI2)O22(OH)2	2.59	1.95
Sr	24.8	28.1	Pentiandite [(Fe,Ni)9S8]	0.51	1.51
Se	5.59	16.1	Ankerite ÊCa(Fe,Mg,Mn)(CO3]2	0.38	0.91
Pd	6.56	15.20	Chalcopyrite (CuFeS2)	0.54	0.65
Pt	7.11	12.80	Magnesiogedrite [(Mg.Fe^laSieAlîO^OHH	0.71	0.62
Sc	10.7	12.3	Hematite/Magnetite [Fe2O3/Fe3O4]	0.17	0.25
Pb	7.34	6.42
Te	5.385	5.73
Ba	4.66	5.44
Zr	4.975	5.41
Sb	4.895	5.23

* From Tescan analysis

Chemical analysis	Drum 1 Drum 2	Mineralogical analysis	Drum 1 Drum 2
Content (g/t)	Content (%)
Y	0.911	1.09	Traces phases
Sn	1.615	1.05	Chromferide [Fe3Cr-|.x(x=0,6)]	0.03	0.02
Nd	0.754	0.99	Molten Lead	0.41	0.26
La	0.677	0.905	Rammelsbergite (NiAs2)	0.10	0.80
Rb	0.615	0.708	Columbite [(Fe,Mn)Nb2O6]	0.32	0.23
Nb	0.575	0.698	llmenite (FeTiO3)	0.09	0.06
Ru	0.557	0.659	Garnet - Pyrope [X3 2+Y23+Si3O12][Mg3AI2(SiO4)3] X represents Ca, Fe2+, Mn or Mg Y represents Al, Cr or Fe3+	0.01	0.01
Th	0.373	0.629	Bornite (Cu5FeS4)	0.01	0.10
Ta	0.463	0.615	Calcite (CaCO3)	0.00	0.01
Au	3.67	0.56	Chalcopyrite + As	0.01	0.03
Dy	0.319	0.519	Lautite (CuAsS)	0.00	0.01

Gd	0.272	0.427	Enstatite (Mg2Si2O6)	0.01	0.00
Ag	0.681	0.378	Covellite (CuS)	0.00	0.02
Er	0.196	0.348	Oregonite (S-bearing) [Ni2FeAs2]	0.01	0.01
Sm	0.224	0.332	Chaîcocite (Cu2S)	0.00	0.01
Cs	0.262	0.323	Sperrylite (PtAs2)	0.00	0.02
Tb	0.212	0.316	Albite (NaAISi3O8)	0.00	0.01
Yb	0.163	0.295	Biotite K(Mg,Fe)3(AISi3O10)(F,OH)2	0.01	0.00
Pr	0.222	0.292
Mo	0.220	0.244
U	0.232	0.238
Cd	0.200	0.168
Hf	0.143	0.16
Ho	<0.100	0.116
W	4.305	2.44
Ce	1.75	2.34
Bi	1.87	1.66
Ge	1.25	1.33
K	<0.100	<0.100

Table 8 Experiment 1 Leach Results

EXPERIMENT 1 Mass solid: 100 g [Glycine]: 40 g/L Solution volume: 1000 mL Température of the solution: 60°C Solid density: 10% Rotational rate: 600 rpm Alkalinity level (pH): 11 Oxygen flow rate: 500 mL/min
Leaching time (hour)	0	3	24	48	72	96
	Cu(ll)	0	28.5	40.5	46.5	51.5	57.5
Ni(ll)	0	127	146	159	174	189

LEACH SOLUTION (ppm)	Cr(lll)	0	1	0.5	0.5	0.5	1
Fe(ll)	0	0.5	0.5	0.5	0.5	0.5
Pt(ll)	0	0.001	0.002	0.002	0.001	0.001
Pd(ll)	0	0.027	0.118	0.193	0.233	0.28
PERCENTAGE EXTRACTION	Cu(ll)	0.00	47.50	67.16	76.73	84.55	93.44
Ni(ll)	0.00	45.36	51.88	56.22	61.21	65.81
Cr(lll)	0.00	0.01	0.00	0.00	0.00	0.01
Fe(ll)	0.00	0.00	0.00	0.00	0.00	0.00
Pt(ll)	0.00	0.28	0.55	0.55	0.27	0.27
Pd(ll)	0.00	6.57	28.57	46.49	55.84	66.42

Table 9 Experiment 2 Leach Results

EXPERIMENT 2 Mass solid: 100 g [Glycine]: 10 g/L Solution volume: 1000 mL Température of the solution: 40°C Solid density: 10% Rotational rate: 600 rpm Alkalinity level (pH): 11 Oxygen flow rate: 500 mL/min
Leaching time (hour)	0	3	24	48	72	96
LEACH SOLUTION (ppm)	Cu(ll)	0	19	29	34	37	38.5
Ni(ll)	0	92.5	132	140	144	144
Crflll)	0	0.5	0.5	0.5	0.5	0.5
Fe(ll)	0	0.5	0.5	0.5	0.5	0.5
Pt(ll)	0	0.001	0.001	0.001	0.001	0.001
Pd(ll)	0	0.001	0.006	0.018	0.03	0.047
PERCENTAGE	Cu(ll)	0.00	31.67	48.09	56.10	60.74	62.56
Ni(ll)	0.00	33.04	46.91	49.50	50.66	50.14
Cr(lll)	0.00	0.00	0.00	0.00	0.00	0.00

EXTRACTION	Fe(ll)	0.00	0.00	0.00	0.00	0.00	0.00
Pt(ll)	0.00	0.28	0.27	0.27	0.27	0.27
Pd(ll)	0.00	0.24	1.45	4.34	7.19	11.15

Table 10 Experiment 3 Leach Results

EXPERIMENT 3 Mass solid: 100 g [Glycine]: 40 g/L Solution volume: 1000 mL Température of the solution: 80°C Solid density: 10% Rotational rate: 600 rpm Alkalinity level (pH): 12.5 Oxygen flow rate: 500 mL/min
Leaching time (hour)	0	3	24	48	72	96
LEACH SOLUTION (ppm)	Cu(ll)	0	31.5	46	53.5	65.5	78
Ni(ll)	0	130	155	182	215	257
Cr(lll)	0	1	1.5	1.5	2.5	3
Fe(ll)	0	0.5	0.5	0.5	0.5	0.5
Pt(ll)	0	0.001	0.001	0.004	0.004	0.013
Pd(ll)	0	0.143	0.398	0.488	0.603	0.735
PERCENTAGE EXTRACTION	Cu(ll)	0.00	52.50	72.83	57.96	56.77	67.60
IXIi(ll)	0.00	46.43	52.59	42.25	39.93	47.73
Cr(lll)	0.00	0.01	0.01	0.01	0.01	0.01
Fe(ll)	0.00	0.00	0.00	0.00	0.00	0.00
Pt(ll)	0.00	0.28	0.26	0.72	0.57	1.87
Pd(ll)	0.00	34.79	92.00	77.18	76.29	92.99

Table 11 Experiment 4 Leach Results

EXPERIMENT 4

Mass solid: 100 g

Solution volume: 1000 mL

[Glycine]: 40 g/L Température of the solution:

80°C Solid density: 10% Rotational rate: 600 rpm Alkalinity level (pH): 12.5 Oxygen flow rate: 0 L/min
Leaching time (hour)	0	3	24	48	72	96
LEACH SOLUTION (ppm)	Cu(ll)	0	25.5	40	45	47.5	49
Ni(ll)	0	106	152	166	180	201
Cr(lll)	0	0.5	0.5	0.5	1.5	2
Fe(ll)	0	0.5	0.5	0.5	0.5	0.5
Pt(ll)	0	0.001	0.002	0.004	0.004	0.004
Pd(ll)	0	0.086	0.393	0.402	0.366	0.353
PERCENTAGE EXTRACTION	Cu(ll)	0.00	42.50	66.33	71.25	67.29	61.25
Ni(ll)	0.00	37.86	54.01	56.32	54.64	53.84
Cr(lll)	0.00	0.00	0.00	0.00	0.01	0.01
Fe(ll)	0.00	0.00	0.00	0.00	0.00	0.00
Pt(ll)	0.00	0.28	0.55	1.05	0.94	0.83
Pd(ll)	0.00	20.92	95.14	92.92	75.69	64.42

The results show sélective leaching of the targeted metals platinum, palladium, nickel and copper from a PGM ore, over iron and chromium. Sélective extraction of the target metals was enhanced by elevated températures and in the presence of an oxidant. However, in ail cases, minimal 5 dissolution of the NCEs Or and Fe occurred.

Example 9. Extraction of metals from electronic scrap (e-waste).

Printed circuit boards having the composition set out in Table 12 were ground to a particle size of 80% passing 106 micron and leached using alkaline glycine solutions at room température ίο and in a bottle being rolled at 100 rpm, with the bottle neck open to air. Aside from any incidental introduction of air via the open bottle neck there was no deliberate addition of oxidant to the System. The ground e-waste contained both CPMs (Au, Pt, Ag, Pd, Pb, Ni, Co, Zn and Gu) as well as NCEs (Fe, Cr and Al)

The leach conditions are set out in Table 13. The concentration of glycine in the alkaline 15 leaching solution was 30 g/L and the pH was 11. The ratio of solids (e-waste) to alkaline leachant was approximately 4 g solids per litre of leachnat. The température was ambient, at approximately 23 °C.

- 29 The resulting concentrations and percentage extractions of the CPMs Au, Ag, Zn, Pb, Cu and Ni leached from the circuit boards are presented in Table 14, Ail CPMs were able to be extracted without significant dissolution of the NCEs. Under the conditions of this Example, there was higher extraction of Zn, Pb and Cu as compared with Au, Ag and Ni.

Table 12

Métal	Unit	Content
Au	ppm	368
Pt	ppb	65
Ag	ppm	557
Pd	PPm	55
Al	%	6.4
Fe	%	2.5
Pb	ppm	26700
Cu	%	55.2
Ni	PPm	3560
Co	PPm	20
Cr	PPm	70
Zn	%	5.8

Table 13

Reagent	llnits	Amount
Glycine	g	15
Water	mL	500

E-waste	g	2.001
NaOH	g	7.2
PH		11
Temp	c	RT-23

Table 14

Sample	Au	Ag	Zn	Pb	Cu	Ni
Time, hour	mg/L	ug/L	mg/L	mg/L	mg/L	mg/L
2	0.001	17	23.6	113	61.2	<0.1
4	0.002	28	43.2	175	404	0.4
6	0.007	95	120	230	701	0.8
24	0.005	62	165	338	1490	0.8
Ext, kg/t	0.001	0.0155	41.2	84.5	372.3	0.2
Ext, %	0.34	1.73	80.94	76.50	72.52	6.49

Example 10: Extraction of metals from electronic scrap using glycine with cyanide 5 as catalyst.

Printed circuit boards having the composition (metals only) set out in Table 15 were ground to a particle size of 80% passing 106 micron and leached using alkaline glycine solutions including a small quantity of cyanide as a catalyst. The ratio of glycine to cyanide was approximately 58:1. The leach was conducted at room température and in a bottle being rolled at 100 rpm, with the ίο bottle neck open to air. Aside from any incidental introduction of air via the open bottle neck there was no deliberate addition of oxidant to the System. The ground e-waste contained both CPMs (Au, Pt, Ag, Pd, Pb, Ni, Co, Zn and Cu) as well as NCEs (Fe, Cr and Al)

The leach conditions are set out in Table 16. The concentration of glycine in the alkaline leaching solution was 30 g/L and the pH was 11. The ratio of solids (e-waste) to alkaline leachant

- 31 was approximately 4 g solids per litre of leachant. The température was ambient, at approximately 23 °C.

The resulting concentrations and percentage extractions overtime of Au, Ag, Zn, Pb, Cu and Ni leached from the circuit boards are presented in Table 17. As can be seen by comparison with Example 9, the percent extractions for ali metals except Pb increased significantly over a given time period, indicating the catalytic effect of CN on the rate of leaching.

Table 15

Métal	Unit	Content
Au	ppm	368
Pt	ppb	65
Ag	ppm	557
Pd	ppm	55
Al	%	6.4
Fe	%	2.5
Pb	ppm	26700
Cu	%	55.2
Ni	ppm	3560
Co	ppm	20
Cr	ppm	70
Zn	%	5.8

îo Table 16

Reagent	Units	Amount
Glycine	g	15

NaCN	g	0.257
Water	mL	500
E-waste	g	2.003
NaOH	g	7.0
pH		11

Table 17

Elément	Au	Ag	Zn	Pb	Cu	Ni
Time, hour	pg/L	pg/L	mg/L	mg/L	mg/L	mg/L
2	83.7	66	54.5	69.7	199	0.5
4	373	168	125	99.8	571	1.1
6	380	156	152	96.9	739	1.2
24	400	88	258	82.2	1620	2.0
Ext, kg/t	0.099	0.0220	64.4	20.5	404.3	0.499
Ext, %	37.61	8.84	97.78	24.29	87.65	20.68

Example 11: Extraction of gold using glycine with sparsely soluble copper cyanide added 5 as catalyst.

This example shows the effect of adding water-insoluble CuCN (copper (mono) cyanide or copper cyanide) as a catalyst during the glycine leaching of gold. It is shown that the use of cyanide on its own as a lixiviant did not give a high gold leach rate, but the use of alkaline glycine in the presence of copper cyanide catalyst significantly improved the leach rate. Figure 12 shows the extraction of gold from a gravity-gold concentrate containing 0.2% gold and 3.7% Gu. The leach conditions are 7 g/L Glycine, 3.4 g/L CuCN at pH 11.0 (added NaOH 2.4 g/L), 10% solids at room température.

- 33 Whilst a number of spécifie process embodiments hâve been described, it should be appreciated that the process may be embodied in many other forms.

In the daims which follow, and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” and variations such as “comprises” or “comprising” are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the apparatus and method as disclosed herein.

Claims (12)

1. A process for the sélective recovery of at least one Chalcophile Group Element (“CPM”) as herein defined from a materiaî containing the CPM and one or more non Chalcophile Group Eléments (“NCE”) as herein defined, said process including:

5 (i) contacting the materiaî with an alkaline solution containing a lixiviant comprising an amino acid or dérivative thereof in order to selectively leach the CPM from the materiaî to produce a CPM containing leachate and a NCE containing residue; and (ii) recovering the CPM from the leachate.

2. The process of daim 1, wherein the alkaline solution is substantially free from thiosulfate or îo ammonia containing species.

3. The process of claim 1 or 2, wherein the alkaline solution further includes an oxidant.

4. The process of any preceding claim, wherein the CPM comprises one or more of Co, Ni, Cu, Zn, Ga, Ge, Rh, Pd, Ag, Cd, In, Sn, Ir, Pt, Au, Hg, Tl, Pb and Bi , preferably the CPM comprises one or more of Co, Ni, Zn, Ga, Ge, Rh, Pd, Ag, Cd, In, Sn, Ir, Pt, Hg, Tl, Pb and Bi.

155. The process of any preceding claim, wherein the alkaline solution has a pH in the range of 7 to 13, preferably in the range of 7 to 11.

5, more preferably between 8 and 10.

6. The process of any preceding claim, wherein the amino acid comprises glycine.

7. The process of any preceding claim, wherein the amino acid concentration in solution is from 0.1 to 240 grams per litre, preferably from 3.75 grams per litre to 60 grams per litre.

208. The process of any preceding claim, further including a preconditioning step prior to step (i), comprising treatment of a passivating coating on the materiaî with an alkaline solution of sulfurous acid and sulfite ions..

9. The process of any preceding claim, wherein the alkaline solution additionally includes a small amount of a catalyst selected from iodine and/or iodide, bromine and/or bromide, thiourea, copper

25 salts, and cyanides, or mixtures thereof.

10. The process of claim 9 wherein the weight ratio of amino acid to the catalyst is not less than 2:1, preferably not less than 10:1.

11. The process of any preceding claim, wherein the alkaline solution has a dissolved oxygen (DO) concentration from 0.1-100 milligrams per litre in solution, such as from 8 to 30 mg/L.

12. The process of any preceding claim, wherein the alkaline solution additionally contains copper salts, such as cupric sulfate or copper cyanide.

513. The process of any preceding claim, wherein step (ii) includes régénération of and recycling of the amino acid lixiviant to step (i).

14. A process for the sélective recovery of at least one Chalcophile Group Element (“CPM”) as herein defined from a material containing the CPM and one or more non Chalcophile Group Eléments (“NCE”) as herein defined, said process including:

10 (i) contacting the material with an alkaline lixiviant that is substantially free from thiosulfate or ammonia containing species and that contains an amino acid or sait thereof in order to selectively leach the CPM from the material to produce a CPM containing leachate and a NCE containing residue; and (ii) recovering the CPM from the leachate.

1515. A Chalcophile Group Element recovered using the process of claim 1 or 15.