Non-cyanide leach processing for metal recovery

Abstract

A process of leaching a metal, such as gold, from a feed source includes combining the feed source with a salt (such as a chloride salt) and / or a leaching reagent, such as a 3% solution to a 35% solution of sodium dichloro-s-triazinetrione dihydrate or a 3% solution to a 35% solution of anhydrous sodium dichloro-s-triazinetrione or a 3% solution to a 35% solution of trichloro-s-triazinetrione or a 3% solution to a 35% solution of calcium hypochlorite in a leach medium to form a feed slurry, and leaching a metal from the feed slurry to form a pregnant leach liquor followed by recovering the metal from the pregnant leach liquor and recycling residual leach solution to form additional feed slurry. The process is cyanide-free and / or arsenic free.

Description

PatentAttorney Docket No. 134465-5027-WONON-CYANIDE LEACH PROCESSING FOR METAL RECOVERYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is based on and claims the benefit of priority to U.S. Provisional Application No. 63 / 680,840, filed August 8, 2024, the entire disclosure of which is hereby incorporated by reference.TECHNICAL FIELD

[0001] The present disclosure relates to recovering one or more metals from rock, ore, waste materials, etc. by leaching comminuted or crushed feed materials with a leaching reagent comprised of a chloride-based leaching solution and an indifferent salt, preferably a chloride salt, which improves leach performance through improved dissolution as well as recovery of a pregnant solution from the leach residue solids. The process is cyanide free and / or arsenic free. Precious metals, such as gold, silver, platinum, palladium, rare earth elements, such as cerium, dysprosium, erbium, europium, gadolinium, holmium, lanthanum, lutetium, neodymium, praseodymium, promethium, samarium, scandium, terbium, thulium, ytterbium, and yttrium, and other valuable metals such as lithium, copper, nickel, cobalt, tin, lead, aluminum, antimony, magnesium, manganese can be recovered by processes of the present disclosure. The disclosed processes can be implemented to treat various feed materials including, for example tailings from, mining and resources extraction, mining waste, industrial waste such as coal ash, dredging spoils, etc.BACKGROUND

[0002] Metals can be recovered from metal bearing rock, ore or waste materials by a leach system such as an acid or alkaline leaching system etcetera. Water is typically used in such a process as well as a transport medium in such leach operations. Conventional processes for leaching metals from ore require diluting a slurry with subsequent thickening and often also filtration of solids to achieve effective liquid-solids separation.DBl / 161307018.1 1PatentAttorney Docket No. 134465-5027-WO

[0003] When a high amount of clays or other small micron sized particles are present, the leach is hindered because of worse slurry rheology and poor contacting and therefore low dissolution mechanics. Often post leach liquid-solids separation becomes so difficult that the necessary pregnant solution separation from the leach residue makes the whole process uneconomical.

[0004] Additionally, conventional processes utilize cyanide and / or arsenic in the processing, leading to increased handling requirements and environmental concerns.

[0005] There is a need to improve the performance of leaching metals from feed materials as well as a need to improved liquid-solids separation of a pregnant solution from leach residue. Furthermore, there is a need for ore and leach processing solutions that do not use harmful or environmental hazardous constituents, such as arsenic and cyanide.SUMMARY OF THE DISCLOSURE

[0006] Advantage of the present disclosure is the combined improvement of both the leach dissolution as well as subsequent pregnant solution recovery from the residue solids.

[0007] The advantages of the present disclosure results in increased leach rates due to increased ionic activity in the leach. These and other advantages are satisfied, at least in part, by a process of leaching a metal in a leach medium including a leaching reagent comprising, consisting essentially of, or consisting of a chloride-based leaching solution from one or more sources of a chloride salt, preferably a sodium chloride salt, and an indifferent salt including, consisting essentially of, or consisting of a chloride salt, preferably a sodium chloride salt. The chloridebased leaching solution can be a 3% solution to a 35% solution of any chloride salt or combination thereof, alternatively, a 3% solution to a 30% solution of any chloride salt or combination thereof or a 3% solution to a 25% solution of any chloride salt or combination thereof or a 3% solution to a 20% solution of any chloride salt or combination thereof, where the % solution (also called mass concentration) is defined as the mass of a constituent divided by the volume of the solution.

[0008] Sources of chloride salt include sodium chloride (NaCl), calcium hypochlorite Ca(OCl)2, a source of sodium hypochlorite (NaClO), such as commercial bleach, sodium dichloro- s-triazinetrione dihydrate (CsftCENsNaOs), anhydrous sodium dichloro-s-triazinetrione (CsCENsNaOs), trichloro-s-triazinetrione (C3CI3N3O3), and FeCh. The sources of chloride salt are combined to create an oxidative leaching solution.DB1 / 161307018.1 2PatentAttorney Docket No. 134465-5027-WO

[0009] Also the oxidant for the leaching process can be generated several methods, including industrial electrolysis of salt solutions or brines from a natural body of water such as seawater. These methods allow chlorine to be generated efficiently, even from seawater sources, which are readily available in many coastal areas. The most common method of producing chlorine involves the electrolysis of aqueous solutions (e.g., brine) containing sodium chloride (NaCl). In an electrolysis cell, chlorine gas (CL) is produced at the anode, while hydrogen gas (H2) and sodium hydroxide (NaOH) are produced at the cathode. Impurities in seawater such as magnesium and calcium can interfere with the electrolysis process and may require purification steps.

[0010] Before electrolysis, the brine (seawater, or saltwater solution) may be purified to remove impurities that may interfere with the electrolysis process. Purification may involve: (i) filtration: removes insoluble particles (sand, dirt, etc.) from the brine, (ii) precipitation of impurities: calcium and magnesium ions in seawater can form insoluble salts, so they are removed by chemical precipitation (for example, lime (CaO) can be added to remove calcium as calcium carbonate (CaCCh), (iii) ion exchange (one preferred purification method in this application): an ion-exchange process may be used to remove specific ions from the brine, particularly in seawater processing, and (iv) membrane filtration - membranes such as microfiltration (MF), ultrafiltration (UF), or nanofiltration (NF) can be employed to remove fine particles, organic matter, and divalent ions like calcium and magnesium.

[0011] An additional advantage of the present disclosure is that the leaching reagent, as well as the other constituents used in the metal recovery process, are cyanide-free and arsenic-free, which results in a metal recovery process that has reduced handling safety requirements, has reduced worker exposure concerns, and is more environmentally friendly than processes that employ cyanide and / or arsenic.

[0012] A still further advantage of the present disclosure is the reduction in dissolution of minerals introducing impurities to the pregnant solution.

[0013] Additional advantages of the present disclosure include improved liquid-solids separation such as increased efficiency in an amount of liquid-solids separation at a constant feed solids concentration and throughput or at a higher specific throughput rate at constant feed solids concentration and thickener and filter separation performance. Such improvements translate to smaller apparatus requirements and lower operating costs. Further, such processes are suitable for large scale operations with high solids loading in the liquid-solids separation operations.DB1 / 161307018.1 3PatentAttorney Docket No. 134465-5027-WO

[0014] Further advantages entail requiring less feed dilution and mixing of the leach slurry to achieve acceptable flocculation, which translates to a smaller thickener or elimination of thickeners from the process.

[0015] These and other advantages are satisfied, at least in part, by a process of leaching a metal from a feed source by combining the feed source with a leaching reagent comprising, consisting essentially of, or consisting of a solution of sodium hypochlorite, and an indifferent salt including, consisting essentially of, or consisting of a chloride salt, preferably a sodium chloride salt in a leach medium to form a feed slurry; leaching a metal or salt thereof from the feed slurry to form a leach slurry containing a pregnant leach liquor having metal salts dissolved therein and leach solids residue; separating the pregnant leach liquor from the leach solids residue; recovering metal salts from the pregnant leach liquor and forming a residual leach solution having a concentration of the indifferent salt dissolved therein of at least about 0.4 wt%; and recycling the residual leach solution to form additional feed slurry.

[0016] The processes of the present disclosure are suitable for large scale operations such as in the mining industry and can form feed slurry at a rate of at least two metric tonnes in a 24 hour period, e.g., feed slurry is formed at a rate of at least 1-2 metric tonnes in a 10 hour period such as at a rate of least 1-2 metric tonnes in a 5 hour period, or 1 hour period. The processes of the present disclosure are also suitable for liquid-solids separation operations (thickener and / or fdtration) in which a slurry has a high solids concentration, e.g., greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% of solids during the liquid-solids separation operation.

[0017] Such leaching operations can be used with high clay content ore or rock such as sedimentary rock that is composed primarily of clay-sized particles, e.g., claystone, mudstone, etc. In an aspect of the present disclosure, the process includes leaching a clay rich material, e.g., an ore or rock having more than 30% clay sized particles of less than 10 microns.

[0018] Ores are often leached at solids concentrations not unlike that of a thickener underflow. An advantage of the present disclosure is an effective flocculation at an elevated solids concentration, thus making possible additional dewatering of the leach slurry by gravity or mechanical separation after flocculation without the extensive dilution conventionally required for flocculation.DB1 / 161307018.1 4PatentAttorney Docket No. 134465-5027-WO

[0019] An additional advantage of the present disclosure is accelerated dewatering under compression. The increased dewatering rate under compression applies to membrane press pressure filtration with pressures up to 25 bar, and also for the consolidation in tailings storage facilities under self-weight compression.

[0020] Another advantage of processes of the present disclosure is that the residual leach solution includes a high concentration of the indifferent salt and can be recycled back to the leach system operation to form additional leach slurry which significantly improves the economics of the process.

[0021] Embodiments include one or more of the following features individually or combined. For example, in some aspects, the feed source including a metal or metal salt can comprise rock, ore or a waste material such as from spent electronic equipment such as spent batteries, or spent circuit boards, which can contain precious metals such as gold, silver, platinum, palladium, etc. and other valuable metals such as lithium, copper, nickel, cobalt, tin, lead, aluminum, antimony, magnesium, manganese, etc. In other embodiments, the leach medium is at ambient temperature, or is a temperature of at least 30 °C, or at a temperature in the range of 25-35 °C. In further embodiments, water for the leach medium or the leach medium is heated by a natural source.

[0022] Additional advantages of the disclosed leaching solution, leaching process, and methods for recovering one or more metals will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment is shown and described, simply by way of illustration of the best mode contemplated of carrying out the inventions. As will be realized, other and different embodiments are contemplated and / or are possible, and the several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Reference is made to the attached drawings, wherein elements having the same reference numeral designations represent similar elements throughout.

[0024] FIG. l is a schematic illustration of a leaching flowsheet that can be used in practicing certain aspects of the present disclosure.DB1 / 161307018.1 5PatentAttorney Docket No. 134465-5027-WO

[0025] FIG. 2 is another schematic illustration of a leaching flowsheet that can be used in practicing certain aspects of the present disclosure.

[0026] FIG. 3 shows the Oxidation-Reduction Potential (ORP) values (in mV) and pH values as a function of leaching time (minutes) for leaching processes using a leaching solution with combinations of chloride salts.

[0027] FIG. 4 is a schematic illustration of an electrolysis flowsheet that can be used in practicing certain aspects of the present disclosure.DETAILED DESCRIPTION OF THE DISCLOSURE

[0028] The present disclosure includes leaching a feed source including a metal or metal salt using a leaching process that comprises (i) a leaching reagent including a solution of sodium hypochlorite in which the sodium hypochlorite is in an amount of 3% solution to 35%, alternatively, 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution or 3% solution to 12% solution, or including a solution of sodium dichloro-s-triazinetrione dihydrate in which the sodium dichloro-s-triazinetrione dihydrate is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution, or including a solution of anhydrous sodium dichloro-s-triazinetrione in which the sodium dichloro-s-triazinetrione is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution, or including a solution of calcium hypochlorite in which calcium hypochlorite is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution, and (ii) an indifferent salt.

[0029] In aqueous solution, the hypochlorite ion (CIO ) is unstable and tends to undergo disproportionation into chloride (CL) and chlorate (CIOs ) ions, especially when heated. Due to this instability, it may be advantageous to use alternative oxidizing agents in the leach solution. Water-soluble oxidants such as metal chlorates (e.g., sodium chlorate), chlorites, or chlorine dioxide can be added directly to provide similar oxidative potential. These compounds can serve as effective substitutes for hypochlorite, delivering equivalent redox chemistry in situ without relying on unstable hypochlorite solutions.

[0030] Chloride / hypochlorite solutions are an alternative leaching reagent to cyanide for gold extraction. These solutions can dissolve gold across a wide pH range, making them more versatileDB1 / 161307018.1 6PatentAttorney Docket No. 134465-5027-WO than cyanide. The solution pH determines the dominant oxidizing species: pH > 7.5: Hypochlorite ion (OC1-) is predominant. pH 3.5-7.5: Hypochi orous acid (HOC1) is the main oxidizing agent. pH < 3.5: Molecular chlorine (Ch) evolves at low pH . Among these species, hypochi orous acid (HOC1) is identified as the most effective for gold leaching. HOC1 facilitates the formation of the gold chloride complex [AuCk]-. It is potentially less toxic than cyanide, effective across a broader pH range, and may be suitable for ores that respond poorly to cyanide leaching. However, the effectiveness may vary depending on ore mineralogy. Proper pH control is needed to maintain the desired oxidizing species. Chloride-based systems can be corrosive, requiring appropriate materials for processing equipment. They may be particularly useful for refractory ores or those with high copper content and could be an option for environmentally sensitive areas where cyanide use is restricted. While promising, more research may improve the process for various ore types. Scale-up and industrial implementation studies are necessary to assess its viability as a widespread cyanide alternative. This chloride / hypochlorite leaching system represents one of several promising alternatives to cyanide in gold extraction. Its ability to operate effectively across a wide pH range and its potentially lower toxicity makes it an interesting option for further development in the field of hydrometallurgy.

[0031] In some embodiments, the process may include electrolysis of a saline source to generate the chloride-based leaching solution that contains hypochlorous acid (HOC1). During electrolysis, chlorine gas (Ch) evolves at the anode (bubbles form), hydrogen gas (H2) evolves at the cathode (bubbles form), and HOC1 forms in the solution when the pH is controlled between 5.5-6.5. Hydrochloric acid or sodium hydroxide may be used to control the pH to the desired range. An example of the electrolytic process is illustrated in FIG. 4. The saline source may include filtered seawater (natural or artificial), a made-up solution that includes sodium chloride, or a rejected stream from a desalination process or a combination of such saline sources.

[0032] In some embodiments, the saline source includes a rejected stream from a desalination process. The rejected stream is the portion of the incoming feedwater that is not converted into fresh water and is instead discharged because it contains elevated concentrations of salts and other impurities than the original feedwater. In some embodiments, the rejected stream may include sodium chloride at a concentration of 70 g / L to 300 g / L. Repurposing the rejected stream may reduce the volume of waste to be discharged, making final disposal more manageable andDB1 / 161307018.1 7PatentAttorney Docket No. 134465-5027-WO environmentally friendly. For example, electrolysis of the rejected stream may generate the chloride-based leaching solution and / or active chloride species for leaching.

[0033] The indifferent salt improves the overall process of metal or metal salt dissolution in the leach step and improves the liquid-solids separation.

[0034] In the leaching process, a feed source including a metal or metal salt or a compound containing the metal in elemental state or an oxidized state is prepared by, for example, processing the feed source in a mechanical destabilization process. The mechanical destabilization process typically starts with crushing the feed source with the optional addition of water to form a processed feed source, which is then storable and / or can be transported to the leach system. In aspects of processes of the present disclosure, a leaching reagent and an indifferent salt in a leach medium is combined with the feed source to form a feed slurry.

[0035] The feed source including a metal or metal salt can comprise rock or ore. Leaching metal-based rock or ore includes mechanical destabilizing the ore, e.g., crushing, grinding, milling (including high energy milling). The feed source including a metal or metal salt can also comprise a waste material, such as from spent electronic equipment (such as spent batteries, or spent circuit boards), which can contain precious metals such as gold, silver, platinum, palladium, etc. and other valuable metals such as lithium, copper, nickel, cobalt, tin, lead, aluminum, antimony, magnesium, manganese, etc. A mechanical destabilization process of waste material can include crushing the waste material and separating undesirable solids, e.g., scrap paper, plastics, outer metallic bodies. Whether the feed source originates from rock or ore or from waste material, after mechanical destabilization, the process can include optionally sieving the crushed material to a certain size.

[0036] After mechanical destabilization, the processed feed source is processed in a leach system to convert the target metal into soluble salts that can be separated from unwanted solids. The leach system extracts metal with a leaching reagent, typically in an aqueous medium, to form a pregnant solution. The pregnant solution is then further processed to precipitate solids and then separate the solids from the liquid. The separated solids are then further processed, such as by concentrating, to recover the one or more metals while the residual leach solution can be recycled back to the leach system.

[0037] As noted herein, in some embodiments the leaching reagents for the leach system include a solution of sodium hypochlorite in which the sodium hypochlorite is in an amount of 3% solution to 35%, alternatively, 3% solution to 30% solution or 3% solution to 25% solution or 3%DB1 / 161307018.1 8PatentAttorney Docket No. 134465-5027-WO solution to 20% solution or 3% solution to 12% solution. In other embodiments, the leaching reagents for the leach system include a solution of sodium dichloro-s-triazinetrione dihydrate (CbH iCh sNaO?) in which the sodium dichloro-s-triazinetrione dihydrate is in an amount of 1% solution to 35%, alternatively, 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution or 3% solution to 12% solution. In other embodiments, the leaching reagents for the leach system include a solution of anhydrous sodium dichloro-s-triazinetrione (CsChNsNaCh) in which the anhydrous sodium dichloro-s-triazinetrione is in an amount of 1% solution to 35%, alternatively, 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution or 3% solution to 12% solution. In other embodiments, the leaching reagents for the leach system include a solution of trichloro-s-triazinetrione (C3CI3N3O3) in which trichloro-s-triazinetrione is in an amount of 1% solution to 35%, alternatively, 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution or 3% solution to 12% solution. In other embodiments, the leaching reagents for the leach system include a solution of calcium hypochlorite in which calcium hypochlorite is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to 20% solution. In various embodiments, sodium hypochlorite or sodium dichloro-s-triazinetrione dihydrate or anhydrous sodium dichloro-s-triazinetrione or trichloro-s-triazinetrione or calcium hypochlorite may be used as the sole source of chloride in the leach system.

[0038] In some embodiments, leaching reagents for the leach system may also include acids, such as sulfuric acid, hydrochloric (HC1) acid, etc. Use of chlorides, e.g., including HC1 acid, for leaching metals such as gold is known but has not found significant commercial use because of problems associated with corrosion due to high chloride concentrations in leach solutions, among other issues. However, chloride leach systems have a few advantages. The chloride chemistry is well understood. The chemistry is clean in that outcomes can be readily predicted, and the chemistry readily controlled. The main chemical advantages of the chloride leach system are: (1) Higher ionic activities are possible and therefore also higher reaction rates which results in smaller leach equipment; (2) The solubilities of many metals are higher because of complexing, resulting in higher leach recoveries and also in higher concentrations in the leach product solution which in turn results in higher metal recoveries in the recovery step; (3) The chloride leach system allows selective metal separation; (4) Often the lixiviant regeneration is more straightforward; and (5) The energy consumption for subsequent electrolysis if used is lower due to the higher electrolyteDBl / 161307018.1 9PatentAttorney Docket No. 134465-5027-WO solution conductivity. The chloride low pH leach is typically only used for materials with few acid-consuming minerals, thus limiting the acid consumption. The chloride leach can be either low-pH oxidative or low-pH non-oxidative.

[0039] In other embodiments, leaching reagents for the leach system may be acid free.

[0040] In certain aspects of the present disclosure, an indifferent salt is used as an augmenting reagent in a leach system, particularly in an acidic leach system. Certain indifferent salts are known to increase dissolution rates of metals from ore. Further, indifferent salts can improve liquid-solids separation of the leach slurry and thus further improve the efficiency of the metal recovery process.

[0041] As used herein an indifferent salt is a salt that is highly soluble in water, disassociating in to one or more cations and anions, and remains dissolved in an aqueous phase of the leaching process without precipitating from a slurry throughout the process and remains dissolved in any recycled aqueous liquid. The disassociated cations or anions of the indifferent salt further do not chemically react to form coagulates or chemically react with components of a slurry such as polymer flocculant during the process or undergo oxidation or reduction reactions during the process. Such indifferent salts are advantageous since they remain dissolved in the aqueous phase of compositions and can be substantially recovered in an aqueous phase and thus subsequently used to treat additional ore or slurry. As used herein, “highly soluble” means a soluble salt that has a solubility greater than 0.1 M (moles per liter) in water. Salts with solubility values above this threshold are classified as Category I. Highly soluble salts readily dissociate into their constituent ions when dissolved in water. This dissociation allows for a high concentration of ions in the solution.

[0042] An indifferent salt, such as sodium chloride, also can be used as an augmenting reagent in a chloride leach system. For example, addition of sodium chloride is known to increase the chloride activity, thereby improving a chloride leach. Sodium chloride as an augmenting reagent can be used when the system has another source of chloride, such as, for example, a solution of sodium hypochlorite.

[0043] The objective of leaching rock and ore is to liberate and dissolve one or more target metals (or salts thereof) such as precious metals, such as gold and silver, base metals, platinum group metals, rare earth elements, heavy metals, alkali metals such as lithium, and alkaline metals, etc. At times, additional complexing agents are used for precious metal extraction and are addedDB1 / 161307018.1 10PatentAttorney Docket No. 134465-5027-WO to leach process to ensure that the liberated metals remain in solution, typically called a pregnant solution. For example, organosulfur compounds such as thiourea can be used.

[0044] It has also been conventional to use cyanide as a complexing agent for precious metal extraction. However, for various health and environmental reasons, it is beneficial to minimize or eliminate the use of cyanide from the process. Thus, the disclosed leaching process does not use cyanide, i.e., is a cyanide-free process, and the resulting pregnant solution is cyanide-free.

[0045] Similarly, other hazardous reagents, such as arsenic, are also not used in the disclosed leaching process, i.e., the leaching process is arsenic-free, and the resulting pregnant solution is arsenic-free.

[0046] Once target metals are in solution, the pregnant solution is processed to separate the solution from the unwanted remaining solids, which is an effective method for both separation and often simultaneous upgrading of the solids. The metals are selectively removed from the pregnant solution by a variety of methods such as for example precipitation, cementation, electrolysis, or carbon or resin loading. This selective removal upgrades the metal content further.

[0047] In one specific application, refractory gold or silver ores are extracted from the host mineral in a leach system utilizing a solution of sodium hypochlorite in which the sodium hypochlorite is in an amount of 3% solution to 12% solution. In the leaching system, chlorine is formed from the sodium hypochlorite. This chlorine then forms hydrochloric (HC1) acid, which reacts in the leaching system as disclosed herein. The chloride from the sodium hypochlorite leach enhances leach kinetics. An augmenting reagent can optionally be used in conjunction with the sodium hypochlorite leach.

[0048] The electrochemical potential (Eh) of the system can be further controlled by an electrochemical potential controlling reagent, such as ferrous chloride, to improved leaching system performance. At certain pH values and with an electrochemical potential controlling reagent, the chloride acts as a complexing ligand to keep gold and silver in solution, thus eliminating the need of cyanide or other complexing agents such as thiourea to keep the precious metals in solution to allow separation from the remaining not leached gangue solids by liquidsolids separation, be it thickening or filtration or filtration with a filter cake wash.

[0049] The gold and silver are readily precipitated from the pregnant solution and once precipitated can be recovered again by liquid-solids separation as a concentrate from the remaining barren solution.DB1 / 161307018.1 11PatentAttorney Docket No. 134465-5027-WO

[0050] In the case of lithium extraction, processes of the present disclosure can improve the economics of recovering the lithium from lithium-hosted, lithium-rich clays or clay-rich lithium minerals. The presence of lithium in clays can be as impurities, as inclusions, in lattice cavities, by adsorption on particle surfaces or edges or by isomorphous substitution. These clays present a challenge in the dewatering of the leach residue and the efficient recovery of the pregnant solution from the leach residue consisting of clays.

[0051] However, processes of the present disclosure are suitable for high clay content ores such as sedimentary rock that is composed primarily of clay-sized particles, e g., claystone, mudstone, etc. In an aspect of the present disclosure, the process includes leaching a clay rich ore, e.g., an ore having more than 30%, 40%, 50% of clay sized particles of less than 10 microns.

[0052] In another aspect of the present process, lithium can be leached from sedimentary rock, such as claystone found in Nevada, USA, by treating such rock with a leach medium that includes a high concentration of an indifferent salt (without an acid or chloride source).

[0053] A total dissolved indifferent salt concentration of the indifferent salt should preferably be (on solution basis) at least of at least 0.5 wt% and preferably no less than about 0.75 wt%, such as at least about 1 wt%, 1.5 wt%, 2 wt% and even at least about 2.5 wt% 3 wt%, 4 wt%, 5 wt%, 10 wt% etc. In addition, the leach medium is preferably at a temperature of at least about 20 °C, such as at least about 25 °C, 30 °C, 32 °C (about 90 °F), 33 °C, 35 °C, 37 °C (about 99 °F), 38 °C (about 100 °F), 40 °C, 42 °C, 45 °C. Advantageously, water used for the leach medium or the leach medium itself can be heated by natural sources, i.e., sources of heat that occur naturally at a leach site, such as by solar radiation, geothermal heating, and / or other natural sources available at the site for a large scale operation.

[0054] The addition of an indifferent salts such as is the case with sodium chloride to a slurry system can also markedly improve flocculation, floccule aggregation, settling and consolidation of particles from a slurry with a clear release of solution. The flocculation and subsequent dewatering are improved with or without addition of polymer flocculant, although the addition of a nominal amount of polymer flocculant further disproportionally improves liquid-solids separation performance.

[0055] FIGS. 1 and 2 illustrate generalized leaching 100 flowsheets. As illustrated, a feed source is provided to a mechanical destabilizer (110). The feed source can comprise ore, rock etc. including one or more metals of interest. The feed source can also comprise, or alternativelyDB1 / 161307018.1 12PatentAttorney Docket No. 134465-5027-WO comprise, a waste material such as from spent electronic equipment, e.g., spent batteries, spent circuit boards, etc., which include one or more metals of interest. The feed source can also comprise, or alternatively comprise, tailings from mining and resource extraction, mining waste, industrial residues such as coal ash, or dredging spoils. Metals of interest from such feed sources can include gold, silver, platinum, palladium, etc. and other valuable metals such as lithium, copper, nickel, cobalt, tin, lead, aluminum, antimony, magnesium, manganese, etc.

[0056] Mechanical destabilization (110) grinds, mills, such as with a high energy mill, crushes, etc. the feed source to liberate solid particles and promote the leach process. The mechanically destabilized feed source, i.e., processed feed source, can then be sent to a leach system (112) in which a feed slurry (not shown) is formed by combining the feed source with a leach medium including water with one or more leaching reagents and one or more indifferent salts. In one aspect of the present disclosure, the leaching reagent includes a solution of sodium hypochlorite in which the sodium hypochlorite is in an amount of 3% solution to 12% solution. Augmenting reagents, such as for example ferric chloride, can also be added to the leach system (112). An electrochemical potential controlling reagent, if desired, can also be added to the leach system (112) and can be either be an oxidant such as oxygen or hydrogen peroxide in the case of an oxidative leach, or a reducing agent such as ferrous chloride, alcohol or hydrocarbon required in a non-oxidative leach.

[0057] Most metals are soluble in a chloride leach medium through complexing. For example, depending on the electrochemical potential, gold and silver are complexed by the chloride in the medium and remain soluble. In the case of lithium leach, a chloride leach is especially favorable due to the high solubility of lithium chloride. A number of chloride process leach routes are possible. One such route is the roasting of ore feed in the presence of a chloride source, such as for example potassium chloride. Other chloride sources are also possible. Lithium in a lithium containing ore can be converted in the roast to lithium chloride, which then on contacting with water will leach due to the high solubility of lithium chloride in water. This process route is more applicable for lithium ores refractory to an acid leach and when lithium is present in the clay through isomorphous substitution, as for example in Hectorite.

[0058] Another process route is the direct leach of lithium with acid, of which one possibility is hydrochloric acid formed from sodium dichloro-s-triazinetrione dihydrate, anhydrous sodium dichloro-s-triazinetrione, trichloro-s-triazinetrione (C3CI3N3O3), and / or calcium hypochlorite. TheDB1 / 161307018.1 13PatentAttorney Docket No. 134465-5027-WO presence of indifferent salts increases the chloride concentration which improves the leach kinetics. The addition of an indifferent salt can reduce the leach of higher valent ion and therefore unwanted impurities. Further, the indifferent salt together with a polymer flocculant improves liquid-solids separation of high clay ore.

[0059] The target metal or metals are leached from the feed slurry in leach system (112) with the leach medium to form a leach slurry (114) containing a pregnant leach liquor of metal salts and leach solids residue. Advantageously, water used for the leach medium or the leach medium itself can be heated by natural sources to room temperature or to a temperature of at least about 20 °C, such as at least about 25 °C, 30 °C, 32 °C (about 90 °F), 33 °C, 35 °C, 37 °C (about 99 °F), 38 °C (about 100 °F), 40 °C, 42 °C, 45 °C. The pregnant leach liquor and leach solids residue of the leach slurry are then separated.

[0060] Processes of the present disclosure are suitable for large scale operations such as in the mining industry and can form feed slurry at a rate of at least two metric tonnes in a 24 hour period, e.g., feed slurry is formed at a rate of at least 1-2 metric tonnes in a 10 hour period such as at a rate of least 1-2 metric tonnes in a 5 hour period, or 1 hour period. With such large scale operations thickeners are employed to increase the rate of processing the feed material during the operation.

[0061] As illustrated in FIG. 1, leach slurry (114) can undergo a liquid-solids (L / S) separation operation (120) such as by thickening (122) followed by filtration (124), e.g., bed filtration, to separate the pregnant leach liquor from the leach solids residue. The liquid-solids separation can be implemented using other liquid-solids separation systems such as for example centrifuging, crossflow filtration or counter-current decantation. An advantage of the processes of the present disclosure is that the liquid-solids separation operation (thickening and / or filtration) can be carried out with a leach slurry having a high solids concentration, e.g., greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% of solids during the liquid-solids separation operation.

[0062] Typically, the filter cake (leach solids residue) is washed (wash water) to recover as much of the pregnant solution as possible. Filtration is an attractive liquid-solids separation technology as the dilution of the leach solution within the circuit is minimized. Leach residues high in clay are typically difficult to filter, often rendering the whole leach extraction process uneconomical. The presence of clays will also introduce operational issues in terms of cloth blinding and residual sticky cake adhering to the cloth prevents proper filter press closure, causingDB1 / 161307018.1 14PatentAttorney Docket No. 134465-5027-WO operational maintenance costs and the loss of valuable online filtration time or loss in throughput. However, it was found that including a sufficiently high concentration of indifferent salt within the leach medium during the leaching operation allows liquid-solids separation by filtration even with feed materials high in clays, e.g., at and above 1 to 5 %. In addition, filtration of the leach slurry can be carried out at a high solids concentration, e.g., greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% of solids during filtration.

[0063] FIG. 2 shows a liquid-solids separation operation that does not include a thickening step in which leach slurry (114) can undergo a liquid-solid separation directly by filtration (124a). That is, separating the pregnant leach liquor from the leach solids residue can occur directly from the leach slurry (114) by filtration without a prior thickening step even with a high solids loading and in a large scale operations in which feed slurry and / or leach slurry is formed at a rate of at least two metric tonnes in a 24 hour period, e.g., the slurry is formed at a rate of at least 1-2 metric tonnes in a 10 hour period such as at a rate of least 1-2 metric tonnes in a 5 hour period, or 1 hour period. Such a filtration step can be carried out with the leach slurry having a high solids concentration, e.g., greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% of solids during filtration.

[0064] Typically, the leach solids residue, e.g., filter cake, is washed (wash water) to recover as much of the pregnant solution as possible. As explained for FIG. 1, filtration is an attractive liquid-solids separation technology as the dilution of the leach solution within the circuit is minimized and filtration is enhanced by including a sufficiently high concentration of indifferent salt within the leach medium during the leaching operation.

[0065] Metal salts dissolved in the pregnant solution can be selectively recovered by a variety of methods such as for example precipitation, cementation, electrolysis, or carbon or resin loading. As shown in the examples of FIGS. 1 and 2, metal salts can be recovered from the pregnant leach liquor (132) by adding reagents that precipitate the metal salts in a precipitation operation (140). However, other recovery mechanisms such as for example cementation, electrolysis, carbon or resin loading can be used in place of or in addition to precipitation.

[0066] In the case of precipitation or cementation, the metal or metal salts precipitated as solid form can be removed from the remaining now essentially barren solution (residual leach solution) by another liquid-solid separation system operation (150). In this example, a product slurry isDB1 / 161307018.1 15PatentAttorney Docket No. 134465-5027-WO formed by precipitated metal or metal salts in a residual leach solution and the solids are separated from the product slurry.

[0067] Such a liquid-solid separation system operation can include, for example, thickening followed by filtration to form a concentrate (160) of the metal and metal salts and a residual leach solution (170). However, other liquid-solid separation systems can be used in place of or in addition to by thickening followed by filtration such as, for example, centrifuging, crossflow filtration or counter-current decantation. Depending on the chemistry, a leach solution regeneration step may or may not be required.

[0068] An advantage of the processes of the present disclosure is that leaching with a chloridebased solution from one or more sources of chloride salt can occur without the use of cyanide or arsenic, and the processing of product slurry having a high solids concentration can still occur.

[0069] Another advantage of the processes of the present disclosure is that the liquid-solids separation operation (thickening and / or filtration) of the product slurry can be carried out with a product slurry having a high solids concentration, e.g., greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% of solids during the liquid-solids separation operation even in a large scale operation. Further, precipitated metal and / or metal salts can be directly filtered from the residual leach solution to form the concentrate (160) without a prior thickening step even in large scale operations. That is, separating metal salts from the pregnant leach liquor in the product slurry can occur directly from the product slurry by filtration without a prior thickening step even with high solids loading and in a large-scale operation.

[0070] Another advantage of processes of the present disclosure is that the residual leach solution (170) includes a high concentration of the indifferent salt, e.g., the same or higher concentration or very close to the same concentration of the indifferent salt, as the concentration of the indifferent salt in the leach medium at the start of the leach system 112 because the indifferent salt remains in solution during the process. There may be some increase in the amount of indifferent salt depending on the feed source or there may be some loss due to various steps in the process. However, in an aspect of processes of the present disclosure, the residual leach solution has a concentration of the indifferent salt dissolved therein of at least about 0.4 wt%, such as at least 0.5 wt% and preferably no less than about 0.70 wt%, such as at least about 1 wt%, etc. and up to and including the amount in the leach medium.DB1 / 161307018.1 16PatentAttorney Docket No. 134465-5027-WO

[0071] As shown in FIGS. 1-2, the residual leach solution (170) can be recycled back to the leach system (112) to form additional leach slurry which significantly improves the economics of the process.

[0072] Further, an effective liquid-solids separation improves the overall efficiency of the metal recovery process. Effective liquid-solids separation steps can improve recycling of leaching reagents thus limiting the cost of replenishing leaching reagent in the circuit, as well as reducing downstream complications where remaining solution is unwanted.

[0073] In an aspect of the present disclosure, the overall efficiency of the leach system can be improved by including an indifferent salt to the system. The indifferent salt can be added with the leaching reagents in the leach system. Alternatively, or in addition thereto, the indifferent salt can be included at the liquid-solid separation stage of the process. The addition of an indifferent salt at a sufficient concentration in the leach medium of a slurry can improve the liquid-solid separation process and thus improve the overall process of metal recovery.

[0074] As shown in the example of FIGS. 1 and 2, an indifferent salt is added in the leach system (112). For example, the chloride concentration in a leach system can be increased by the addition of a soluble indifferent chloride salt. Typically, the soluble salt is added at the same time as the other leach components are added. For example, sodium chloride is one such augmenting reagent that can be added to promote the solution ionic activity. The increased ionic activity in turn improves the leach kinetics. Typically, sodium chloride concentrations of greater than 1 % up to 5% or less, alternatively, 3.5 % or less or 3.0 % or less, in the leach medium are sufficient to achieve the enhanced ionic activity. The sodium chloride as ionic additive fits well into the chloride leach system.

[0075] Further, including an indifferent salt can minimize subsequent unwanted precipitation reactions. The addition of an indifferent salt to the leach process improves the subsequent liquidsolids separation step(s) and appears indifferent to the type of system employed for liquid-solids separation, thus improving the overall leaching efficiency. It is advantageous to include indifferent salts that do not interfere with the leach and the recovery steps. In the case of a chloride leach system, it is advantage to utilize indifferent salts of chloride, e.g., sodium chloride which is inexpensive and relatively benign.DB1 / 161307018.1 17PatentAttorney Docket No. 134465-5027-WO

[0076] Any use of chloride as an augmenting reagent as well as indifferent salts including if / how chloride from indifferent salt has to be balanced against the presence of chloride from the chloride-based leaching solution from one or more sources of a chloride salt.

[0077] The present invention asserts that the balance of different chloride species affects the amount of chloride consumed during leaching. Leaching can be performed as a co-current, countercurrent, or alternative process, and is most conveniently conducted at atmospheric pressure — pressurization is not necessary. The leaching process is carried out at temperatures ranging from ambient up to the boiling point of the leaching solution, with a preferred range of 25- 40 °C. The oxidation-reduction potential (ORP) should be at least 800 mV, alternatively at least 900 mV, and preferably between 1020-1100 mV. The chloride concentration in the solution is preferably at least 100 g / L, with atypical range of 200-300 g / L, and can vary within specific ranges as needed. The chloride concentration in the lixiviant is most effective in the 1-400 g / L range, preferably 100-400 g / L range, particularly 200-300 g / L.

[0078] After the feed slurry is leached, unwanted solids are removed from the process. In one aspect of the present disclosure, the aqueous medium in any slurry of the process includes a sufficient concentration of indifferent salt to improve separation of solids from the aqueous phase of the slurry. It was found that by adding indifferent salt in a sufficient quantity (1 to 5 wt%) to a feed source, efficient aggregation of solid particles and efficient flocculation results. In certain embodiments, it was found to result a cake with a solids concentration higher than 65 wt% (solid concentration > 65 wt%). It was further found that this process is considerably more efficient than conventional coagulation methods in that flocculation can be carried out at higher feed solids concentrations, requires less mixing and is effective with minerals such as for example clays that traditionally have been refractory to liquid-solids separation. The floccule aggregates formed are more robust and less prone to shear. The flocculation is more efficient in capturing fine and ultrafine particles, which results in a cleaner overflow liquid.

[0079] In one aspect of a process of leaching a metal from a feed source, a slurry formed from either a leach slurry or product slurry or other slurries include the solution of sodium hypochlorite as the sole chloride source. In such a case, the solution of sodium hypochlorite can be at a sufficient concentration that the slurry can be directly filtered to remove solids without diluting the slurry and / or without use of a thickener apparatus or thickening step. In another aspect of a process of leaching a metal from a feed source, thickeners are used to facilitate liquid-solids separation.DB1 / 161307018.1 18PatentAttorney Docket No. 134465-5027-WO

[0080] In other aspects of a process of leaching a metal from a feed source, the solution of sodium hypochlorite can include a second source of chloride salt, such as sodium chloride, as an augmenting reagent with even further advantageous effect including direct filtration.

[0081] Advantageously, the process of the present disclosure results in an increased liquidsolids separation efficiency of at least 25% as compared to slurry without the added indifferent salt. The comparison is done at constant feed solids concentration and throughput.

[0082] When employing a thickener, the processes of the present disclosure can have as increased rate of sedimentation of solids, an increased overflow liquid throughput, and / or an increased percentage by mass of solids of thickener underflow slurry as compared to slurry in the thickener apparatus without the added indifferent salt. Each of the rate of sedimentation of solids, overflow liquid throughput, percentage by mass of solids of thickener underflow slurry can individually be increased by at least 25%, e.g., by at least 50%, 75%, 100%, 125% or higher, as compared to a slurry in the thickener apparatus without the added indifferent salt. Without being bound to theory, the reasons for the separation efficiency improvement lies in the robust nature of the formed floccule aggregates and their increased settling rate in the upper part of the thickener, as well as in the higher hydraulic conductivity and consequent higher dewatering rate of the solids bed in the lower part of the thickener, as well as the improved fines and ultra-fines capture when treating (or combining) the feed source with the indifferent salt.

[0083] In practicing aspects of the present process, thickening a slurry includes treating the slurry with at least one polymer flocculant or solution thereof. The slurry can be treated in the thickener apparatus with the at least one polymer flocculant concurrent with or subsequent to treating the slurry with the indifferent salt. In some embodiments of the application, the feed source can be combined with the at least one polymer flocculant in the thickener apparatus concurrent with or subsequent to combining the feed source with the indifferent salt. The process can further comprise removing underflow slurry and overflow aqueous liquid from the sediment tank as two distinct streams.

[0084] In thickeners using conventional coagulation and flocculation reagents, the feed slurry typically is diluted prior to thickening operations to a solids concentration of concentration between 2% and 10% solids (by weight). However, an advantage of practicing aspects of the process of the present disclosure is that dilution of the slurry into a thickener or fdter can be minimized and even eliminated. Hence in practicing aspects of processes of the present disclosure,DB1 / 161307018.1 19PatentAttorney Docket No. 134465-5027-WO the leach slurry and / or product slurry can have a solids concentration of greater than 10 wt% solids, such as greater than 15 wt% solids and greater than 20 wt%, 25 wt% and even higher than 50 wt% during liquid-solids separation operations even in a large scale operation. This significantly reduces the cost of diluting the feed. Such costs would be incurred in pumping and mixing supernatant with the thickener feed. Other costs are reduced in that the thickener feedwell is reduced in size and complexity. The thickener diameter is reduced further reducing the capital costs. The reduction in costs is at least 25% and greater than 30%, 40% and even 50%.

[0085] Further, the solids loading rate for a feed source treated according to processes of the present disclosure can be greater than typically achieved in thickeners. Typical solids loading rate for coarse sand is about 1.0 to 1.5 (metric tonne / hour) / meter squared ((t / h) / m2) and for typically feed slurries between about 0.3 and 1.0 (t / h) / m2. Advantageously, the solids loading rate for a feed source to be treated (or combined) with an indifferent salt and optionally polymer flocculant can be greater than 2 (t / h) / m2, such at least about 2.5 (t / h) / m2and at least about 3, 3.5, 4, 4.5, 5 and 6 (t / h) / m2. The improvement in solids loading rate results in a substantial reduction of thickener cross sectional area, which either translates to smaller diameter thickener or alternative less thickeners, representing a substantial savings in capital costs.

[0086] In high-rate thickeners, solids contents in the underflow are of the order of 50% by weight, depending on the nature of the feed source and conditions of thickener operation (feed rate, etc.). Higher solids concentrations in the underflow slurry can at times be obtained using high- density, high-compression or paste thickeners. These are taller than conventional thickeners to increase the self-consolidating weight on the solids in the formed bed. They also have steeper floor slopes to enhance the movement of settled slurry to the discharge point. The higher bed solids density of these thickeners relative to high-rate thickeners greatly increases the rake torque, requiring a higher rake drive capability. In addition, as the solids density increases near the base of the thickener, hydraulic conductivity decreases, lowering the rate of water release. High density thickeners are more expensive than high-rate thickeners and there is a trade-off between cost, the ability to pump thickener underflow and the amount of water recovered.

[0087] An indifferent salt preferably has a solubility in water of greater than 2 g of salt per 100 g of water (i.e., a salt / water solubility of 2g / 100g) at 20 °C. Preferably the indifferent salt has a water solubility of at least about 5 g / 100 g at 20 °C, e.g., at least about 10 g / 100 g of salt / water at 20 °C. Indifferent salts that are useful in practicing processes of the present disclosure include saltsDB1 / 161307018.1 20PatentAttorney Docket No. 134465-5027-WO having a monovalent cation without multivalent cations, e.g., alkali halide salts such as sodium chloride, potassium chloride; also salts having monovalent cations without multivalent cations such as sodium and potassium nitrate, sodium and potassium phosphates, sodium and potassium sulfates, etc. are useful in practicing processes of the present disclosure. Other indifferent salts having monovalent cations useful in practicing processes of the present disclosure include ammonium based salts without multivalent cations such as ammonium chloride (NH4Q), ammonium bromide (NH4Br), ammonium carbonate ((NH4)2COa), ammonium bicarbonate (NH4HCO3), ammonium nitrate (NH4NO3), ammonium sulfate ((NH4)2SO4), ammonium hydrogen sulfate (NH4HSO4), ammonium dihydrogen phosphate (NH4H2PO4), ammonium hydrogen phosphate ((NFU^HPCh), ammonium phosphate ((NF rPC ), etc. Mixtures of such salts can also be used.

[0088] Certain ammonium-based salts are useful for inclusion when practicing the present disclosure since residual ammonium-based salts on the concentrated solids can be beneficial to plant life. In fact, many of the ammonium-based salts are useful as fertilizers, e.g., ammonium chloride, ammonium nitrate, ammonium sulfate, etc. Many of the monovalent cation sulfate and phosphate salts are also useful as fertilizers. In certain embodiments of the present disclosure, the indifferent salt or salts used in the processes of the present disclosure can preferably be non-toxic and beneficial to plant life to aid in environmental remediation and the restoration of mine sites.

[0089] When a sufficiently high concentration of the indifferent salt is included in treating (or combining with) ore, rock or a feed source, the indifferent salt can destabilize and consolidate solids in a slurry. For a relatively short process times with a relatively low energy input, a total dissolved indifferent salt concentration of the indifferent salt should preferably be on solution basis at least of at least 0.5 wt% and preferably no less than about 0.75 wt%, such as at least about 1 wt%, 1.5 wt%, 2 wt% and even at least about 2.5 wt% 3 wt%, 4 wt%, 5 wt%, 10 wt% etc. Determination of the concentration of the indifferent salt dissolved in the aqueous fraction includes the amount added together with any indifferent salt that may already be part of the aqueous fraction of the feed source prior to addition of indifferent salt to the process.

[0090] The indifferent salt(s) can be combined with the feed source of the present disclosure as a solid, e.g., combining the salt as a powder with the feed source. Alternatively, the salt can be in a solution to treat (or combine with) the feed source, e.g., by combining an aqueous salt solution with feed source in the thickener apparatus. In some aspects of the present disclosure, an aqueousDB1 / 161307018.1 21PatentAttorney Docket No. 134465-5027-WO solution of the indifferent salt can be used having a concentration of no less than about 1 wt%, e.g., greater than about 2 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 20 wt%, 30 wt% and even as great as a 40 wt% or as an aqueous salt slurry. The feed source and indifferent salt solution should be mixed at a ratio sufficient to destabilize and consolidate solids in the slurry.

[0091] In some embodiments of the present processes, the leach medium may include a polymer flocculant. A concentration of the polymer flocculant in the leach medium may have a range of not less than zero to up to about 0.005 wt % or up to about 0.01 wt % or up to 0.04 wt % or up to 0.05 wt % or up to 0.1 wt % or up to 0.2 wt % or up to 0.4 wt %.

[0092] In some embodiments of the present processes, it can be more advantageous to use a natural source of the indifferent salt or salts such as in a natural body of water including such salts in sufficiently high concentration such as at least about 2 wt% and even at least about 3 wt% or greater. For example, ocean or seawater can be used as a source of indifferent salts, which can significantly improve the economics of the process under certain conditions. The vast majority of seawater has a salinity of between 31 g / kg and 38 g / kg, that is, 3.1-3.8%. On average, seawater in the world’s oceans has a salinity of about 3.5% (35 g / L, 599 mM). Seawater includes a mixture of salts, containing not only sodium chloride as sodium cations and chlorine anions (together totaling about 85% of the dissolved salts present), but also sulfate anions and calcium, potassium and magnesium cations. There are other ions present (such as bicarbonate), but these are the main components. Another natural source of highly soluble salts that can be used as a source of highly soluble salts includes a hypersaline body of water, e.g., a hypersaline lake, pond, or reservoir. A hypersaline body of water is a body of water that has a high concentration of sodium chloride and other highly soluble salts with saline levels surpassing ocean water, e.g., greater than 3.8 wt% and typically greater than about 10 wt%. Such hypersaline bodies of water are located on the surface of the earth and also subsurface, which can be brought to the surface as a result of ore mining operations.

[0093] In other embodiments of the present processes, it can be advantageous to use a brine produced in desalinization of salt water as a source of an indifferent salt(s). The brine can be used alone as a source of the indifferent salt(s) or in combination with another source of indifferent salt(s) such as seawater.

[0094] In other embodiments of the present processes, it can be advantageous to use artificial seawater as a source of an indifferent salt(s). The artificial seawater can be used alone as a sourceDB1 / 161307018.1 22PatentAttorney Docket No. 134465-5027-WO of the indifferent salt(s) or in combination with another source of indifferent salt(s) such as seawater. The artificial seawater may contain about 3.5% by weight of sodium chloride. Artificial seawater can be prepared by mixing one or more suitable salts with water; suitable salts include sodium chloride (NaCl), magnesium chloride hexahydrate (MgCh 6H2O), sodium sulfate (Na2SC>4), calcium chloride dihydrate (CaC12-2H2O), potassium chloride (KC1), sodium bicarbonate (NaHCCh), potassium bromide (KBr), boric acid (H3BO3), strontium chloride hexahydrate (SrChAFBO), and sodium fluoride (NaF).

[0095] Although indifferent salts can destabilize and consolidate solids in a slurry, adding one or more polymer flocculant(s) can reduced the time for sedimentation and increase overflow output. Hence, one or more polymer flocculants(s) can be added concurrent with or subsequent to treating (or combining) the feed source with the indifferent salt in the thickener apparatus.

[0096] Polymers that are useful in practicing the present disclosure include water-soluble flocculating polymers such as polyacrylamides or copolymers thereof such as nonionic polyacrylamides and copolymers thereof, an anionic polyacrylamide (APAM) such as a polyacrylamide-co-acrylic acid, and a cationic polyacrylamide (CP AM), which can contain comonomers such as acryloxyethyltrimethyl ammonium chloride, methacryloxyethyltrimethyl ammonium chloride, dimethyldiallyammonium chloride (DMDAAC), etc. Other water-soluble flocculating polymers useful for practicing the present disclosure include a polyamine, such as a polyamine or quaternized form thereof, e g., polyacrylamide-co-dimethylaminoethylacrylate in quaternized form, a polyethyleneimine, a polydiallyldimethyl ammonium chloride, a polydicyandiamide, or their copolymers, a polyamide-co-amine, polyelectrolytes such as a sulfonated polystyrenes can also be used. Other water-soluble polymers such as polyethylene oxide and its copolymers can also be used. The polymer flocculants can be synthesized in the form of a variety of molecular weights (MW), electric charge types and charge density to suit specific requirements. Advantageously, the flocculating polymer used in practicing processes of the present disclosure do not include use of activated polysaccharides or activated starches, i.e., polysaccharides and starches that have been heat treated, in sufficient amounts to lower the density of the floc to below the density of the tailings water from which they are separated. Such activated polysaccharides and activated starches when used in sufficiently high dosages tend to form low density flocs which rise to the surface of an aqueous composition, which can cloud overflow liquid.DB1 / 161307018.1 23PatentAttorney Docket No. 134465-5027-WO

[0097] The amount of polymer(s) used to treat (or combine with) a feed source should preferably be sufficient to flocculate the solids in the feed slurry. The amount of polymer(s) used to treat feed source can be characterized as a dosage based on the weight percent of the solids in the feed source. In some embodiments of the present disclosure, one or more polymer flocculant(s) can be used to treat feed source at a dosage (weight of the flocculant(s) to weight of the solids in the slurry) of no less than zero and up to about 0.005 wt%, e.g., up to about 0.01 wt% and in some implementations up to about 0.015 wt%, 0.020 wt%, 0.025 wt%, 0.03 wt%, 0.04 wt%, even up to about 0.07 wt %, 0.09 wt %, 0.1 wt %, 0.2 wt %, or 0.4 wt%.

[0098] Because indifferent salts and polymer flocculants that are preferably water soluble are used in the process of the present disclosure, the temperature of thickening slurries in a thickener apparatus may not be elevated above ambient temperature to practice the process. In certain embodiments, treating a feed source according to the various embodiments herein can be carried out at about ambient temperature or no more about 2 to about 5 °C above ambient temperature.

[0099] In practicing aspects of the present process, thickening slurry includes treating a feed source with an indifferent salt or solution thereof in a thickener apparatus including a sediment tank and separating and recovering overflow aqueous liquid, e.g., clarified water, from the sediment tank after treating the feed source. The process can include combining a feed source with a concentration greater than 2 wt% solids, such as greater than 15 wt% and even greater than 20 wt% solids and higher such as 50%, with an indifferent salt in the feed. With sufficient concentration of the indifferent salt in the aqueous phase of the feed slurry, the solids settle to the bottom of the tank under the pull of gravity and can be pushed towards the outlet port by rakes. Advantageously, the solids loading rate for a feed source to be treated (or combined) with an indifferent salt and optionally polymer flocculant can be greater than 1.0 (t / h) / m2, such at least about 2.5 (t / h) / m2and at least about 3, 3.5, 4, 4.5, 5 and 6 (t / h) / m2. As the result of the possibility to feed the liquid-solids separation unit at a higher solids concentration by using an indifferent salt with polymer and because of the higher solids loading rates achievable, substantially less liquidsolids separation surface will be required, reducing either the size or the number of the units required, thus reducing the capital and operating cost requirement substantially.

[0100] Clarified water can exit a thickener sediment tank through an overflow port or lip of the tank. Conventional overflow clarity is typically in the range of 500 ppm to 5000 ppm. But to achieve such low overflow clarity, the solids loading rate is relatively kept low. An advantage ofDB1 / 161307018.1 24PatentAttorney Docket No. 134465-5027-WO the present disclosure is that even with a very high solids loading rates (e.g., at least about 4, 5 and 6 (t / h) / m2, the overflow clarity remains lower than 5000 ppm, such as lower than 2500 ppm, 1000 ppm and even lower than 500 ppm or 300 ppm. Such overflow clarity can be determined by a turbidity detector. A reduction in overflow clarity reduces upstream and downstream complications that would have been caused by the presence of suspended solids. The reduction in suspended solids eliminates a build-up of slimes within the process, introducing also a circulating load. Slimes increase the reagent consumption. Slimes also change the rheology of the slurries, thus impacting extraction processes negatively. Downstream slimes can be the cause of impurities being introduced, requiring expensive cleaning process steps. Substantial savings are therefore realized through the production of a clear pregnant solution recovery in the liquid-solids separation step.

[0101] Settling performance and the final solids content of the settled solids (thickener underflow slurry) is enhanced by the indifferent salt at sufficient concentration in the slurry. An advantage of treating (or combining) feed source with an indifferent salt according to aspects of the present disclosure is that a rise rate of the feed slurry can be very low even with a high solids loading rate because of being able to process a high feed solids concentration, otherwise not possible. For example, a rise rate of the feed slurry can be less than 3 (meter / hour) (m / h) at a solids loading rate (t / h) / m2between about 3 to 6 and even less than 2 m / h at a solids loading rate about 1.5 (t / h) / m2. The possibility of feeding the liquid-solids separation units at a high solids concentration results in the use of smaller units thus substantially reducing the capital and operating costs.

[0102] Advantageously, since the indifferent salt is highly water-soluble salt, the indifferent salt remains almost entirely in the aqueous phase of the feed slurry and can be recovered with overflow aqueous liquid, e.g., clarified water, from the sediment tank after treating the feed source. In certain embodiments of the present disclosure, the overflow liquid, e.g., clarified water, recovered from the feed slurry has a concentration of the indifferent salt that is similar to the concentration of the indifferent salt in the feed slurry. Some loss of indifferent salt may be due to loss with removing underflow slurry. However, it is preferable that the directly recovered overflow aqueous liquid has a concentration of the indifferent salt dissolved therein of at least about 0.4 wt%, such as at least 0.5 wt% and preferably no less than about 0.70 wt%, such as at least about 1 wt%, etc. The separated overflow liquid including the dissolved indifferent salt can be used to treatDB1 / 161307018.1 25PatentAttorney Docket No. 134465-5027-WO additional tailings in the thickener apparatus. In addition, the separated overflow liquid including the dissolved indifferent salt can be concentrated prior to use to treat additional feed slurry such as by nano filtration, reverse osmosis, combinations thereof, etc.

[0103] Advantageously, the treatment of the leach residue with indifferent salt and polymer improves the consolidation rate in thickening, filtration and later in the filter storage facility.

[0104] EXAMPLES

[0105] FIG. 3 shows the Oxidation-Reduction Potential (ORP) values (in mV) and pH values as a function of leaching time (minutes) for leaching processes using a leaching solution with combinations of chloride salts, e.g., NaCl and sodium dichloro-s-triazinetrione dihydrate. In FIG. 3, the evolution of ORP and pH over time during a leaching test is shown, demonstrating a well- controlled oxidative environment desirable for chloride-based gold leaching. ORP started around 1000 mV — preferred for HOG and Ch-driven dissolution — and gradually declined over the first 180 minutes due to oxidant consumption or metal extraction, before recovering between 250-300 minutes, likely due to delayed oxidant release or air exposure. The system maintained strong oxidizing conditions throughout. Concurrently, pH began near 6.5-7, desirable for HOC1 stability, dipped slightly to ~5.5-6.0 due to CL hydrolysis or mineral buffering, and then stabilized around pH 6, supporting efficient metal recovery without chlorine loss. The system maintained oxidizing conditions (ORP > 850 mV) and favorable pH (5.5-6.5) for more than 5 hours. This supports the effectiveness of the oxidant dosing and buffering strategy — suitable for both heap and agitated leaching when reagent delivery is managed appropriately.

[0106] Embodiments

[0107] Embodiment 1 : A process of leaching precious metal values from a feed source, the process comprising the steps of a) Contacting the comminuted ore with a diluted solution of a chloride source, and allowing a soaking time of at least 10 minutes, preferably between 10 minutes and 3 hours. b) Dissolving or adding the second source of chloride to the solution of step (a), c) Allow a contact time of at least 1 hour for the solution from (b), preferably between 1 to 24 hours. d) Adding an indifferent salt to the solution from step (c) to complete the leaching process.DB1 / 161307018.1 26PatentAttorney Docket No. 134465-5027-WO g) Recovering the precious metal.

[0108] Embodiment 2: The material has a pulp density in the range of 8 to 50 %, preferably 10 to 35 %.

[0109] Embodiment 3: An oxidant leaching solution is in contact with comminuted ore. The oxidative leach solution also preferably contains a primary and secondary source of chloride, such as a water-soluble salt. A sufficient mount of a base, such as sodium chloride, is added to the primary leach solution.

[0110] Embodiment 4: The secondary source of chloride plays a catalytic role in the process. The secondary leach solution, while containing the same chemical components as the primary leach solution, is a base and preferably has a pH of 4-9, preferably 4-7 and an oxidate reduction potential (ORP) of at least 800 mV, alternatively at least 900 mV, and more preferably 1020 mV to 1100 mV.

[0111] Embodiment 5: The order of the addition of the chloride sources as part of the initial leaching solution can be changed without impacting the leaching process.

[0112] Embodiment 6: The chloride source agent (or combination of chloride source agents) is adjusted so the pH of the leach solution in the range of 4-9, preferably 4-7, and the ORP is at least 800 mV, alternatively at least 900 mV, and more preferably 1020 mV to 1100 mV.

[0113] Embodiment 7: A chloride source, such as sodium chloride (NaCl), calcium hypochlorite Ca(OCl)2, a source of sodium hypochlorite (NaClO) as commercial bleach, sodium dichloro-s-triazinetrione dihydrate (CsH+ChNsNaOs), anhydrous sodium dichloro-s-triazinetrione (CsChNsNaCh), trichloro-s-triazinetrione (C3CI3N3O3), and ferrous chloride (FeCh), are combined to create an oxidative leaching solution.

[0114] Embodiment 8: Leaching can be performed as a co-current, countercurrent, or alternative process, and is most conveniently conducted at atmospheric pressure — pressurization is not necessary.

[0115] Embodiment 9: The total chloride concentration from all sources in the solution is preferably at least I / L, with a typical range of 2-200 g / L, and can vary within specific ranges as needed.

[0116] Embodiment 10: The chloride concentration in the lixiviant is in the range of 1-200 g / L, particularly 2-200 g / L.DB1 / 161307018.1 27PatentAttorney Docket No. 134465-5027-WO

[0117] Embodiment 11 : The process may include a reagent management system (RMS) to (i) recover and recycle reagents, (ii) concentrate the leach solution thereby leading to downstream effects (e.g., in the size of the solutions for the Merrill-Crowe process), (iii) generate the indifferent salt, and (iv) produce species in situ through electrolysis for the leaching process, enabling on- demand reagent production integrated within the process flow. The RMS is designed to align with a zero-discharge policy. It is preferred that all, and at least most, i.e., greater than 95%, materials, reagents, and solutions utilized in the process are fully recovered, recycled, or repurposed within the system, eliminating or substantially eliminating the need for waste disposal. For example, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.25%, at least 99.5%, at least 99.75%, at least 99.9% or each of the materials, reagents, and solutions are recovered recycled, or repurposed within the system. Also for example, no more than 5%, no more than 4%, no more than 3%, no more than 2%, no more than 1%, no more than 0.75%, no more than 0.5%, no more than 0.25% of materials, reagents, and solutions used in the process are waste. Accordingly, the sustainability of the leaching process may improve and environmental impact may be reduced.

[0118] The RMS may include: (i) filters, such as sand filters, cartridge filters, and membrane filters (e.g., filters for ion exchange, reverse osmosis, nanofiltration, ultrafiltration, and / or microfiltration) for purifying seawater or saltwater solution to remove impurities that may interfere with the electrolysis process, (ii) an electrolytic cell to electrolyze the purified seawater or saltwater solution to generate the oxidant for the leaching process, (iii) an evaporator to reduce a volume of wastewater in tailings and / or the residual leach solution, leaving behind a more concentrated slurry or solids, and (iv) a solid-liquid separator (e.g., a clarifier and / or a filter press) to separate the solids in the slurry from the liquid. The equipment in the RMS are fluidly connected to each other.

[0119] Embodiment 12: The process may include electrolysis of a saline source to generate the chloride-based leaching solution that contains hypochlorous acid (HOC1). During electrolysis, chlorine gas (CI2) evolves at the anode (bubbles form), hydrogen gas (H2) evolves at the cathode (bubbles form), and HOC1 forms in the solution when the pH is controlled between 5.5-6.5. Hydrochloric acid or sodium hydroxide may be used to control the pH to the desired range. An example of the electrolytic process is illustrated in FIG. 4. The saline source may include filteredDB1 / 161307018.1 28PatentAttorney Docket No. 134465-5027-WO seawater (natural or artificial), a made-up solution that includes sodium chloride, or a rejected stream from a desalination process or a combination thereof.

[0120] Embodiment 13: A process of leaching precious metal values from a feed source; the process comprising the steps of: a) contacting a comminuted ore formed from the feed source with at least one chloride salt for a first residence time of at least 1 hour, preferably between 1 to 24 hours, to form a slurry; b) adding an indifferent salt to the slurry to form a leach solution; c) holding the leach solution for a second residence time to effect a leaching process; and d) concentrating the leach solution to form a concentrated leach solution and a recovered chloride salt, wherein the recovered chloride salt includes the at least one chloride salt; e) recovering a metal from the concentrated leach solution, and f) recycling the recovered chloride salt to step (a), wherein a total amount of chloride source agent adjusts a pH of the leach solution to a range of 4 to 9, preferably 4 to 7, or 4 to 6 and wherein an oxidation / reduction potential (ORP) of the leach solution is at least 800 mV, preferably at least 900 mV, and more preferably 1020 mV to 1100 mV. At least step (d) among the steps of the process may be performed by RMS.

[0121] Embodiment 14: The process may further include step (g): recovering, by a reagent management system, at least 95% of the indifferent salt from the concentrated leach solution, wherein the concentrating of the leach solution to form a concentrated leach solution and a recovered chloride salt is performed by the reagent management system, wherein the reagent management system recovers at least 95% of the at least one chloride salt to form the recovered chloride salt, wherein the recycling of the recovered chloride salt is performed by the reagent management system, and wherein the reagent management system is configured to recycle at least 95% of the at least one chloride salt.

[0122] Only the preferred embodiments of the present invention and examples of its versatility are shown and described in the present disclosure. It is to be understood that the present invention is capable of use in various other combinations and environments and is capable ofDB1 / 161307018.1 29PatentAttorney Docket No. 134465-5027-WO changes or modifications within the scope of the inventive concept as expressed herein. Thus, for example, those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific substances, procedures and arrangements described herein. Such equivalents are considered to be within the scope of this invention and are covered by the following claims.DBl / 161307018.1 30

Claims

PatentAttorney Docket No. 134465-5027-WOCLAIMSWHAT IS CLAIMED IS:

1. A process of leaching a metal from a feed source, the process comprising: combining the feed source with a leaching reagent and an indifferent salt in a leach medium to form a feed slurry; leaching the metal and a metal salt from the feed slurry to form a leach slurry containing a pregnant leach liquor having metal salts dissolved therein and leach solids residue; separating the pregnant leach liquor from the leach solids residue; and recovering the metal salts from the pregnant leach liquor and forming a residual leach solution having a concentration of the indifferent salt dissolved therein of at least about 0.4 wt%, wherein the leaching reagent includes a chloride-based leaching solution from at least one chloride salt.

2. The process of claim 1, wherein the at least one chloride salt in the chloride-based leaching solution is sodium hypochlorite.

3. The process of claim 2, wherein the sodium hypochlorite is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution.

4. The process of claim 1, wherein the at least one chloride salt in the chloride-based leaching solution is (i) sodium dichloro-s-triazinetrione dihydrate, (ii) anhydrous sodium dichloro-s- triazinetrione, (iii) trichloro-s-triazinetrione, (iv) calcium hypochlorite, or any combination of (i)- (iv).

5. The process of claim 4, wherein (i) the at least one chloride salt in the chloride-based leaching solution is sodium dichloro-s-triazinetrione dihydrate, and the chloride-based leaching solution includes sodium dichloro-s-triazinetrione dihydrate in an amount of 1% solution to 35% solutionDB1 / 161307018.1 31PatentAttorney Docket No. 134465-5027-WO or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(ii) the at least one chloride salt in the chloride-based leaching solution is anhydrous sodium dichloro-s-triazinetrione, and the chloride-based leaching solution includes anhydrous sodium dichloro-s-triazinetrione in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(iii) the at least one chloride salt in the chloride-based leaching solution is trichloro- s-triazinetrione, and the chloride-based leaching solution includes trichloro-s-triazinetrione in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(iv) the at least one chloride salt in the chloride-based leaching solution is calcium hypochlorite, and the chloride-based leaching solution includes calcium hypochlorite in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution.

6. The process according to any one of the preceding claims, wherein the process is cyanide free.

7. The process according to any one of the preceding claims, wherein the process is arsenic free.

8. The process according to any one of the preceding claims, wherein the leach medium further comprises a polymer flocculant, wherein a concentration of the polymer flocculant in the leach medium is up to 0.4 wt%, and wherein a concentration of the indifferent salt dissolved in the leach medium is 1 wt% to 30 wt%.

9. The process according to claim 8, wherein the indifferent salt is an alkali halide salt.

10. The process according to claim 8, wherein the indifferent salt is a chloride-based salt.

11. The process according to claim 8, wherein the indifferent salt is sodium chloride.DB1 / 161307018.1 32PatentAttorney Docket No. 134465-5027-WO12. The process according to any one of the preceding claims, further comprising recycling the residual leach solution to form additional feed slurry, wherein the recycling of the residual leach solution is performed by a reagent management system, and wherein at least 95% of the residual leach solution is recycled.

13. The process according to any one of the preceding claims, wherein the metal is a precious metal.

14. The process according to any one of claims 1-12, wherein the metal includes gold, silver, or both.

15. The process according to any one of claims 1-12, wherein the metal is a rare earth element.

16. The process according to claim 13, further comprising recovering the precious metal from the recovered metal salts.

17. The process according to any one of the preceding claims, wherein separating the pregnant leach liquor from the leach solids residue includes introducing the leach slurry to a thickener apparatus to separate the leach slurry into an underflow slurry and an overflow liquid with an increase in liquid-solids separation rate and / or efficiency of at least 25% as compared to the leach slurry in the thickener apparatus without the added indifferent salt.

18. The process according to any one of the preceding claims, wherein the feed slurry is formed at a rate of at least two metric tonnes in a 24 hour period and separating the pregnant leach liquor from the leach solids residue occurs directly from the leached slurry by filtration without a prior thickening step.

19. The process according to any one of claims 1-18, wherein the feed slurry is formed at a rate of at least two metric tonnes in a 24 hour period and separating the pregnant leach liquor from the leach solids residue occurs when the leach slurry has a solids concentration of greater than 10 wt% solids.DB1 / 161307018.1 33Patent Attorney Docket No. 134465-5027-WO20. The process according to any one of claims 1-18, wherein the feed slurry is formed at a rate of at least two metric tonnes in a 24 hour period and recovering the metal salts from the pregnant leach liquor includes separating the metal salts from the pregnant leach liquor in a product slurry having a solids concentration of greater than 10 wt% solids.

21. The process of claim 18, wherein separating the metal salts from the pregnant leach liquor in the product slurry occurs directly from the product slurry by filtration without a prior thickening step.

22. The process according to any one of the preceding claims, wherein the feed source comprises ore, rock, tailings, mining waste, coal ash, dredging spoils, or waste electronic equipment, and preferably the feed source comprises a lithium containing sedimentary rock.

23. The process according to any one of the preceding claims, wherein the leach medium is at a temperature of at least room temperature, preferably at least 25°C.

24. The process according to any one of the preceding claims, wherein the leach medium is at a temperature of room temperature to 45° C.

25. The process according to any one of the preceding claims, wherein water for the leach medium or the leach medium is heated by a natural source.

26. The process of claim 1, further comprising generating in situ the chloride-based leaching solution via electrolysis of a saline source.

27. The process of claim 26, wherein the saline source includes seawater or a rejected stream from a desalination process or a combination thereof.DB1 / 161307018.1 34PatentAttorney Docket No. 134465-5027-WO28. A process of leaching precious metal values from a feed source, the process comprising the steps of: a) contacting a comminuted ore formed from the feed source with at least one chloride salt for a first residence time of at least 1 hour, preferably between 1 to 24 hours, to form a slurry; b) adding an indifferent salt to the slurry to form a leach solution; c) holding the leach solution for a second residence time to effect a leaching process; and d) concentrating the leach solution to form a concentrated leach solution and a recovered chloride salt, wherein the recovered chloride salt includes the at least one chloride salt; e) recovering a metal from the concentrated leach solution, and f) recycling the recovered chloride salt to step (a), wherein a total amount of chloride source agent adjusts a pH of the leach solution to a range of 4 to 9, preferably 4 to 7, or 4 to 6, and wherein an oxidation / reduction potential (ORP) of the leach solution is at least 800 mV, preferably at least 900 mV, and more preferably 1020 mV to 1100 mV.

29. The process of claim 28, wherein the at least one chloride salt in the chloride-based leaching solution is sodium hypochlorite.

30. The process of claim 29, wherein the sodium hypochlorite is in an amount of 3% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution.

31. The process of claim 28, wherein the at least one chloride salt in the chloride-based leaching solution is (i) sodium dichloro-s-triazinetrione dihydrate, (ii) anhydrous sodium dichloro-s- triazinetrione, (iii) trichloro-s-triazinetrione, (iv) calcium hypochlorite, or any combination of (i)- (iv).

32. The process of claim 31, wherein (i) the at least one chloride salt in the chloride-based leaching solution is sodium dichloro-s-triazinetrione dihydrate, and the chloride-based leaching solutionDB1 / 161307018.1 35Patent Attorney Docket No. 134465-5027-WO includes sodium dichloro-s-triazinetrione dihydrate in an amount of 1% solution to 35% solution or 3% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(ii) the at least one chloride salt in the chloride-based leaching solution is anhydrous sodium dichloro-s-triazinetrione, and the chloride-based leaching solution includes anhydrous sodium dichloro-s-triazinetrione in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(iii) the at least one chloride salt in the chloride-based leaching solution is trichloro- s-triazinetrione, and the chloride-based leaching solution includes trichloro-s-triazinetrione in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution, or(iv) the at least one chloride salt in the chloride-based leaching solution is calcium hypochlorite, and the chloride-based leaching solution includes calcium hypochlorite in an amount of 1% solution to 35% solution or 2% solution to 30% solution or 3% solution to 25% solution or 3% solution to a 20% solution.

33. The process of claim 31, wherein either sodium dichloro-s-triazinetrione dihydrate or anhydrous sodium dichloro-s-triazinetrione is a first chloride source agent, wherein the indifferent salt is a second chloride source agent, and wherein a total chloride concentration in the leach solution from the first chloride source agent and the second chloride source agent is at least 100 g / L.

34. The process of claim 33, where the total chloride concentration is 1-400 g / L, preferably 100- 400 g / L, preferably 200-300 g / L.

35. The process of according to any one of claims 28-34, wherein the leaching can be performed as a co-current, countercurrent, or alternative process.

36. The process of claim 35, wherein the leaching is performed at atmospheric pressure and at a temperature from room temperature to 45° C.DB1 / 161307018.1 36Patent Attorney Docket No. 134465-5027-WO37. The process of any one of claims 28-36, wherein the metal includes gold, silver, or both.

38. The process of any one of claims 28-36, wherein the metal includes a rare earth element.

39. The process of any one of the claims 28-38, wherein the feed source comprises ore, rock, tailings, mining waste, coal ash, dredging spoils, or waste electronic equipment.

40. The process of any one of the claims 28-39, further comprising step (g): recovering, by a reagent management system, at least 95% of the indifferent salt from the concentrated leach solution, wherein the concentrating of the leach solution to form a concentrated leach solution and a recovered chloride salt is performed by the reagent management system, wherein the reagent management system recovers at least 95% of the at least one chloride salt to form the recovered chloride salt, wherein the recycling of the recovered chloride salt is performed by the reagent management system, and wherein the reagent management system is configured to recycle at least 95% of the at least one chloride salt.

41. The process of claim 40, wherein the reagent management system is configured to recover, recycle, or repurpose at least 95% of materials, reagents, and solutions utilized in the process.DB1 / 161307018.1 37

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