Homocysteine and derivatives thereof for separation of minerals from ores

Abstract

A method for separation of minerals in an ore is provided. The method includes: introducing into a separation apparatus a slurry including the ore to be separated, water, and an effective amount of homocysteine or a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof: NR1R7-CH(XR2)((CH2)nSH) (I); and separating some or all of the ore into a plurality of minerals.

Description

HOMOCYSTEINE AND DERIVATIVES THEREOFFOR SEPARATION OF MINERALS FROM ORESFIELD

[0001] The invention relates to methods and compositions useful for separation of valuable minerals from ores.BACKGROUND

[0002] Froth flotation is a mineral processing technique used to amass valuable minerals found in low concentrations in ore deposits throughout the earth’s crust. An application of froth flotation is the separation of different valuable minerals from one another taking advantage of different surface interactions with water and air. To this end, many reagents are commercially used by mineral processing companies around the world. One class of such reagents is called depressants, which selectively interact with certain minerals to make them hydrophilic and sink (or depress) in the flotation process, while other minerals in the same process remain hydrophobic and float to the top of the flotation cell, typically by associating with, attaching to, and / or being enveloped by bubbles introduced by sparging with a gas. Commercially used depressants, especially those used to separate molybdenum from copper, can be toxic to workers and the environment, are typically difficult to remove from water and typically have the disadvantage of emitting hydrogen sulfide gas.

[0003] The production of valuable metals via mining relies on the effective separation of different minerals present in deposits throughout the earth’s crust. Two metals that are often found together in such mineral deposits are copper (Cu) and molybdenum (Mo). In the raw ore, these metals are generally found in sulfide mineral including, among others, chalcopyrite (CuFeSi), bornite (Cu5FeS4), covellite (CuS), chalcocite (CU2S) and molybdenite (M0S2). The most common co-existing minerals are chalcopyrite and molybdenite. A concentrate product including valuable chalcopyrite and molybdenite is often the result of the froth flotation process in which less valuable minerals such as silicates and carbonates are typically discarded. Such chalcopyrite / molybdenite concentrate (referred to in the field as Cu-Mo concentrate) may include 1-30 wt% Cu and much smaller quantities of Mo, for example from ppm level up to 10 wt%. In order to transform the mineral concentrates to Cu and Mo metals, the associated minerals must be separated. For thisreason, a process called “reverse Mo flotation” is utilized in which molybdenite is caused to float by the effect of a collector (mercaptans, kerosene, diesel fuel, etc.), while the copper sulfide minerals are caused to sink (or depress) by the effect of a depressant.

[0004] Currently, the most common depressant for Cu-Mo separation by reverse flotation is sodium hydrosulfide (NaSH). This reagent is added to the Cu-Mo concentrate in an aqueous solution or slurry at relatively high pH (> 11) before the reverse flotation stage, binding to the copper sulfide mineral and making it hydrophilic. Importantly, any remaining NaSH in the process water can be removed by lowering the pH with an acid or a base with a lower pH (< 11) so that NaSH transforms into hydrogen sulfide (H2S) and sodium hydroxide (NaOH). This selective transformation of NaSH allows recirculation of process water upstream to the first stage of mineral processing without the NaSH depressant interfering in the flotation of the valuable minerals.

[0005] A problem associated with the use of NaSH in reverse Mo flotation is the health and environmental impact associated with toxic H2S release and also the large volume of NaSH needed for reaching a great efficiency.

[0006] Accordingly, replacement of NaSH by depressants with lower or minimal environmental impact is an active area of innovation in many mineral processing plants. Alternative depressants such as Nokes reagent (a reaction product of NaOH and phosphorous pentasulfide), sodium thioglycolate and disodium carboxymethyl trithiocarbonate have been tested and sparingly utilized in the field with limited success. Notably, it is difficult to remove an excess of these depressants from the process water to allow recirculation upstream. As mentioned above, NaSH is easily removed from process water through i) pH decrease by acid addition and ii) H2S removal as a gas, but as noted above, the evolution of HzS gas is typically undesirable.

[0007] Other, less toxic depressants have not been as effective as older, more common compounds.

[0008] Yin, et al.; Journal of Molecular Liquids 282 (2019) 177 - 186 discloses the use of L- cysteine as a depressant.

[0009] Yin, et al.; Minerals Engineering 156 (2020) 106438 discloses L-cysteine as a depressant.

[0010] U.S. Patent No. 4,196,073 discloses a process for separating molybdenite from copper sulfide and other metal sulfide minerals with which it is associated in a metallurgical concentrate through use of a copper sulfide depressant which is a compound having at least one nitrogen atom, at least one thio group and at least one hydrophilic group.

[0011] U.S. Patent No. 7,776,844 discloses an N-(phosphonoalkyl)-amino acid, a related compound or a derivative thereof, the N-(phosphonoalkyl)-amino acid, related compound or derivative thereof being in a form as a free acid, salt, partial salt, lactone, amide or ester, or in stereoisomeric or non-stereoisomeric form, other than N-(phosphonomethyl)-glycine or N,N- bis(phosphonomethyl)-glycine.

[0012] U.S. Patent No. 9,511,378 discloses collector compositions including an amidoamine and an amine and methods for making and using same to purify one or more crude materials.

[0013] Chinese Patent Publication No. CN 107138286 A discloses L-cysteine and its salt in metal sulfide ore flotation.

[0014] Chinese Patent Publication No. CN 113617532 A discloses a combined inhibitor for flotation separation of lead-sulfur sulfide ores and application thereof, in which the combined inhibitor includes L-cysteine and sodium poly naphthalenesulfonate.SUMMARY

[0015] The present disclosure provides a method for using a depressant comprising the amino acid homocysteine (typically comprising L-homocysteine), a metal salt or derivative thereof, a compound having structure of Formula (I) below, a reaction product thereof with CS2, or a combination thereof, to selectively react and / or complex (associate) with a first metal in a mixed metal ore more than a second metal in the mixed metal ore, allowing separation of ores comprising the first metal from ores combining the second metal in a medium, such as an aqueous medium. Thereafter, any remaining free and / or associated depressant, which is typically soluble in the medium, can be substantially isolated / removed from the medium (for example, by crystallization or insolublization, such as by introduction of an oxidant) under suitable conditions such as for solid / liquid extraction, followed by recirculation of medium back to the ore separation process. The method can be a cost-effective and an environmentally friendly alternative to other processes that use higher amounts of depressants, depressants that are more toxic, and / or depressants which are more difficult to remove from the metals / ores / minerals and from the medium (water) used in a separation process. Surprisingly, homocysteine, salts and derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof can in fact be at least as effective as traditional depressants (such as NaSH) and more effective thancysteine as a depressant, even though homocysteine differs from cysteine only by a single methylene group.

[0016] The present disclosure describes the use of the amino acid homocysteine, metal salts or derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof as a depressant for sulfide-containing minerals, in particular for (common) copper-containing minerals such as chalcopyrite, chalcocite, bornite, cubanite, covellite, etc., especially with relation to molybdenum-containing minerals such as molybdenite. In mineral separations using aqueous media, it can be important for depressants to be water soluble or water miscible (in particular, water compatible). A particularly impactful property of a depressant comprising homocysteine, metal salts or derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof as part of a flotation circuit is that, after it does its job selectively making soluble or miscible, for instance, the copper-containing mineral in relation to the molybdenum-containing mineral in aqueous separation, it can then be made readily insoluble, for instance by oxidization to the corresponding disulfide, which can then precipitate out of the aqueous medium. This property in particular can allow for the recirculation of medium with at least partial, and typically substantial, reduction in depressant to the separation step and / or to the beginning of the process (e.g., the slurrying of the minerals), thereby reducing and / or minimizing any effect of the depressant on performance of flotation agents upstream. The inventors have found that homocysteine, metal salts or derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof as a Cu depressant in inverse Mo aqueous flotation has the potential to reduce and / or eliminate health and environmental issues associated with NaSH and / or H2S, mitigate explosivity risks related to H2S release, and resolve performance issues of alternative depressants (such as limited facility to separate out depressant or in situ reaction products thereof from process water for water recirculation). Homocysteine, metal salts or derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof can inhibit chalcopyrite flotation even in the presence of a molybdenite collector such as N-dodecyl mercaptan (NDM). Homocysteine, metal salts or derivatives thereof, compounds having a structure of Formula (I) below, reaction products thereof with CS2, or combinations thereof can be removed from aqueous media by induced formation of a disulfide (e.g., using an oxidizer - for the depressant homocysteine, that disulfide would likely comprise orbe homocystine, or 4,4’-dithiobis(2-aminobutanoic acid)) that is water-insoluble and forms a precipitate that can be separated / removed. If desired, the water-insoluble oxidized depressant separated from the recycled aqueous medium may be reversibly reduced to its mercaptan form for recycled use in the process (or in other processes).

[0017] Thus, a method for separation of minerals in an ore is provided, where the method comprises: introducing into a separation apparatus a slurry comprising: the ore to be separated, a medium (typically comprising water - an aqueous medium), and an effective amount of a depressant comprising: homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof:Formula (I) where C* is a chiral carbon and where: R1and R7are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety (such as having 1 to 12 carbon atoms) and optionally comprising one or more heteroatoms, or R1and R7together form an optionally substituted heterocyclic ring structure (such as having from 3 to 18 carbon atoms) and optionally comprising one or more heteroatoms in addition to the nitrogen to which R1and R7are connected; X is: >C(=O), -CH2- or -CN; R2is (i) absent when X represents -CN, or is: (ii) a hydrogen atom, (iii) -OR3, where: R3is a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety (such as having 1 to 12 carbon atoms) and optionally comprising one or more heteroatoms, or (iv) -NR4R3, where: R4and R3are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety (such as having 1 to 12 carbon atoms) and optionally comprising one or more heteroatoms, or R4and R3together form an optionally substituted heterocyclic ring structure (such as having from 3 to 18 carbon atoms) and optionally comprising one or more heteroatoms in addition to the nitrogen to which R4and R5are connected; and n is an integer from 1 to 4, for example from 1 to 3, from 2 to 4, or from 2 to 3,provided that, when X is >C(=O), when R2is -OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2; and separating a portion or all of the ore into a plurality of minerals.BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 shows a comparative recovery curve for recovery of chalcopyrite by flotation without L-homocysteine, and with and without NDM as a collector.

[0019] Figure 2 shows a recovery curve for inhibition of chalcopyrite flotation with and without L-homocysteine, and with and without NDM as a collector.

[0020] Figure 3 shows a recovery curve for inhibition of chalcopyrite flotation by the disodium salt of L-homocysteine, D, L-homocysteine, and D,L-cysteine in the presence of NDM as a collector.DETAILED DESCRIPTION

[0021] As used herein, “effective amount” means an amount of depressant that is effective to depress the flotation of a mineral, in particular by at least 33%, more particularly by at least 50%.

[0022] As used herein, a “depressant” is a compound that selectively reacts and / or complexes (physically and / or chemically associates) with certain minerals or ore components (usually particulate in a slurry medium), causing them to phase separate from other (usually particulate) minerals or ore components (e.g., to sink in slurry / emulsion and / or gravity-based separations, whether or not assisted by other separation means that can include but are not necessarily limited to centrifugation), usually by increasing hydrophilicity of the certain minerals or ore components, relative to the other surrounding minerals or ore components.

[0023] As used herein, a “collector” is a compound that selectively reacts and / or complexes (physically and / or chemically associates) with certain minerals or ore components (usually particulate in a slurry medium), causing them to phase separate from other (usually particulate) minerals or ore components (e.g., to be more likely to be entrained on the surface of or within a gas bubble or other non-aqueous component in a froth flotation separation, such as within a flotation cell), usually by increasing the hydrophobicity of the certain minerals or ore components, relative to the other surrounding minerals or ore components.

[0024] As used herein, a component that is “water insoluble” means that, when the component is combined with water, the resulting mixture has suspended or settled particulates that are visible (and / or 0.2-micron filterable) as a result of the water insoluble component.

[0025] As used herein, a component that is “water compatible” indicates that the component is either water soluble or water miscible, such that, when the component is combined with water, the resulting composition has no suspended or settled particulates that are visible (or 0.2-micron filterable) as a result of the water compatible component.

[0026] As used herein, the phrase “reaction produces] thereof with CS2” is specifically designed to optionally but preferably include a reaction product with cysteine, even though the “thereof’ is used herein to refer to homocysteine, salts or derivatives thereof, and / or compounds of Formula (I), which formula is written herein to textually exclude cysteine but notably to formulaically include some cysteine derivatives (z.e., when n = 1). As noted herein, while cysteine may indeed perform poorly as a depressant in copper-molybdenum separation systems (and optionally systems containing other ores / minerals such as disclosed herein), the “hydrogen trithiocarbonate” version of cysteine, for example, may not perform similarly and can thus be included. In alternative embodiments, nevertheless, the phrase “reaction productfs] thereof with CS2” may be interpreted as not including a reaction product with cysteine.

[0027] The term “comprising” as used herein may also encompass the phrases “consisting of’ and “consisting essentially of.”

[0028] If “consisting essentially of’ is used in a claim, the basic and novel characteristics of the claimed composition or method may specifically include separation of at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 99% of a weight of a desired mineral from an ore, based on the weight of the desired mineral in the ore.Methods

[0029] A method for separation of minerals in an ore is provided. The method comprises:• introducing into a separation apparatus a slurry comprising: the ore to be separated, a medium (typically comprising water - an aqueous medium), and an effective amount of a depressant comprising: homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof:Formula (I) where C* is a chiral carbon and where:R1and R7are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety optionally comprising one or more heteroatoms, or R1and R7together form an optionally substituted heterocyclic ring structure (such as having from 3 to 18 carbon atoms) and optionally comprising one or more heteroatoms in addition to the nitrogen to which R1and R7are connected;X is: >C(=O), -CH2- or -CN;R2is (i) absent when X represents -CN, or is:(ii) a hydrogen atom,(iii) -OR3, where: R3is a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety optionally comprising one or more heteroatoms, or(iv) -NR4R where: R4and R5are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety optionally comprising one or more heteroatoms, or R4and R5together form an optionally substituted heterocyclic ring structure (such as having from 3 to 18 carbon atoms) and optionally comprising one or more heteroatoms in addition to the nitrogen to which R4and R5are connected; and n is an integer from 1 to 4, for example from 2 to 4 or from 2 to 3, provided that, when X is >C(=O), when R2is -OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2; and• separating some or all of the ore into a plurality of minerals.

[0030] For instance, when R1and / or R7comprise a nonaromatic hydrocarbon moiety (optionally comprising one or more heteroatoms), the moiety can contain from 1 to 20 (e.g, from 2 to 18, from 3 to 16, from 4 to 15, from 5 to 10, from 1 to 16, from 1 to 12, from 1 to 10, from 1 to 8, from1 to 6, from 1 to 4, or from 1 to 2) carbon atoms. In particular, R1and / or R7may independently be H or may comprise from 1 to 8, from 1 to 4, or from 1 to 2 carbon atoms.

[0031] For instance, when R3is present and comprises a nonaromatic hydrocarbon moiety (optionally comprising one or more heteroatoms), the moiety can contain from 1 to 20 (e.g, from2 to 18, from 3 to 16, from 4 to 15, from 5 to 10, from 1 to 16, from 1 to 12, from 1 to 10, from 1 to 8, from 1 to 6, from 1 to 4, or from 1 to 2) carbon atoms. In particular, when R3is present, R3may be H or may comprise from 1 to 8, from 1 to 4, or from 1 to 2 carbon atoms.

[0032] For instance, when R4and R3are present and when R4and / or R5comprise a nonaromatic hydrocarbon moiety (optionally comprising one or more heteroatoms), the moiety can contain from 1 to 20 (e.g, from 2 to 18, from 3 to 16, from 4 to 15, from 5 to 10, from 1 to 16, from 1 to 12, from 1 to 10, from 1 to 8, from 1 to 6, from 1 to 4, or from 1 to 2) carbon atoms. In particular, when R4and R5are present, R4and / or R3may independently be H or may comprise from 1 to 8, from 1 to 4, or from 1 to 2 carbon atoms.

[0033] If necessary for the particular minerals desired to be separated and based on other factors such as the electrochemistry of the process, a reducing agent may be introduced prior to the separating step (e.g, before, in tandem with, or after the introduction of the depressant), for example to balance out one or more physico- (and / or electro-) chemical effects of the depressant(s). Non-limiting examples of reducing agents can include hydrazine, urea, sodium sulfide (NazS), hydroxylamine, or a combination thereof.

[0034] In order to form the bubbles necessary for flotation separation, the process may typically involve sparging the slurry with a gas. The gas may comprise or be nitrogen or air; in particular, the gas may comprise or be nitrogen. If necessary to stabilize the bubbles and / or to make them more hydrophobic, one or more frothers or surfactants may be added. A non-limiting example of a frother includes methyl isobutyl carbinol (MIBC).

[0035] According to an embodiment, the separation step may be a flotation separation. Froth flotation, or flotation, is a process of extracting a metal from low-content ores by a stage of concentration. This stage typically precedes a subsequent treatment comprising the heat treatment(also known as smelting) or the leaching and the refining. This is in particular the case with ores of oxides and / or sulfides of lead, zinc, copper, silver, gold, molybdenum, nickel, cobalt, iron, and metals belonging to the platinum group: platinum, palladium, rhodium, ruthenium, iridium and osmium.

[0036] Flotation is a method that typically concentrates and separates the valuable components of an ore from either the undesirable components, “gangue,” or a different valuable mineral to produce one or two mineral concentrates that may be fed to pyrometallurgical or hydro- metallurgical operations. The process of froth flotation can start by crushing ore into fine particles to provide separate particles of one or more desirable minerals and the undesirable gangue components, and then frothing or “pulping” the ore particles with a medium such as water (if the medium comprises other components in addition to water, it is aqueous, but the water can stand in for all components of an aqueous medium in the description herein, even if those other non- water components are not specifically mentioned). Before the frothing process, the aqueous ore particles may be combined with a flotation composition, also referred to as a flotation agent, collector or collector agent, which may also include and / or other appropriate additives. These flotation agents may selectively render the surfaces of the different types of particles hydrophobic, while the depressants may selectively render the surfaces of other types of particles hydrophilic, based on their individual compositions. The frothing is done by passing a stream of air or inert gas bubbles through the aqueous composition of ore and flotation agent, sometimes called “pulp,” in a flotation cell, such that the gas bubbles associate with, attach to, and / or envelop and thus levitate the nowhydrophobic particles as they rise in the hydrophilic aqueous medium. These levitated particles, associated with, attached to, and / or enveloped by the air bubbles, can then collect in a froth layer that flows over the weir of the flotation cell. The undesirable gangue or desirable other mineral(s) may be either unaffected by the flotation agent, or rendered relatively hydrophilic by a depressant such as disclosed herein, compared to the minerals that are floated out and thus settle to the bottom of the flotation cell.

[0037] As discussed above, froth flotation works by separating certain minerals from gangue and / or from other desirable minerals by exploiting differences in their hydrophobicity and hydrophilicity. Hydrophobicity and / or hydrophilicity differences between valuable minerals and waste gangue can be increased through the use of compounds such as depressants, collectors, frothers / surfactants, and / or wetting agents that affect the various compounds in the crushed oredifferently. The adhesion of the bubbles to the mineral s / gangue can be promoted by the action of the flotation agent(s) used. The entrained particles of the metal compounds can then rise to the surface and can be recovered in the form of a foam, also known as flotation concentrate. The gangue particles can be recovered in the lower part of the flotation cell.

[0038] The flotation concentrate which flows over the weir at the top of the flotation cell has a content of desired metal which is therefore considerably higher than that in the starting ore. This content depends on the initial content in the ore and on the selectivity of the composition of the flotation agent. If a depressant such as that disclosed herein is used, the mineral particles that sink or otherwise phase separate from the ore may be removed and further refined.

[0039] After a stage of filtration and drying, the flotation concentrates and / or the depressed mineral can then be introduced into the heat treatment (or smelting) stage. This stage can typically involve a furnace at temperatures which may exceed 1500°C. During this stage, the desired metal can be separated in the molten state from the other substances, in particular from the impurities originating from the gangue of the ore, which may be removed in the form of a slag.

[0040] Depressants can facilitate the separation of sulfide ores either by depressing gangue minerals and floating, or otherwise phase separating the desired mineral, or by holding down (depressing) the desired mineral while floating or otherwise phase separating the undesirable gangue, or by holding down a desired mineral and allowing another desirable mineral to float, or otherwise phase separating from each other.

[0041] In order to facilitate recycle of the (aqueous) medium (such as to the step of slurrying the ore minerals / particles), the method may comprise a step of removing at least a portion (preferably a substantial amount) of depressant from the slurry after the flotation separating step. If more than one depressant is added or present, such as one or more depressants described herein plus an additional depressant, the removed depressant may typically comprise the mixture of depressants including the homocysteine, metal salt or derivative thereof, compound having structure of Formula (I) below, reaction product thereof with CS2, or combination thereof, as well as the additional depressant. Alternatively, if more than one depressant is added or present, such as one or more depressants described herein plus an additional depressant, the removed depressant may comprise the homocysteine, metal salt or derivative thereof, compound having structure of Formula (I) below, reaction product thereof with CS2, or combination thereof, and not the additional depressant(s). Further alternatively, if more than one depressant is added or present,such as one or more depressants described herein plus an additional depressant, the removed depressant may comprise the additional depressant(s) and not the homocysteine, metal salt or derivative thereof, compound having structure of Formula (I) below, reaction product thereof with CS2, or combination thereof. These two alternative embodiments would typically be less preferable for methods where significant recycle of the (aqueous) medium is desired, because of the build-up of depressant in the recycled medium.

[0042] When significant recycle of the (aqueous) medium is effectuated, it can be desirable for at least 50 wt% (e.g, at least 55 wt%, at least 60 wt%, at least 65 wt%, at least 70 wt%, at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, at least 99 wt%, or at least 99.9 wt%; and typically up to about 100 wt%) of the depressant(s) to be removed from the slurry, based on a total weight of depressant(s) in the slurry, after the flotation separating step.

[0043] As noted herein, the removing can comprise converting at least a portion of the depressant into a water-insoluble composition, and removing the water-insoluble composition. In certain circumstances, the converting of the depressant into a water-insoluble composition may comprise adjusting the pH of the slurry to a range from about 4 to about 9 (e.g., if acidic pH, from about 4 to less than 7, from about 5 to less than 7, from about 5 to about 6 or from about 6 to less than 7; if basic pH, from more than 7 to about 9, from more than 7 to about 8, or from about 8 to about 9; if mild pH and not encompassing the entire range from about 4 to about 9, then from about 5 to about 9, from about 4 to about 8, from about 6 to about 9, from about 5 to about 8, or from about 6 to about 8). Additionally or alternatively, the pH may be adjusted to or may be from 4.0 to 9.0, from 4.3 to 9.0, from 4.5 to 9.0, from 4.7 to 9.0, from 5.0 to 9.0, from 5.3 to 9.0, from 5.5 to 9.0, from 5.7 to 9.0, from 6.0 to 9.0, from 6.3 to 9.0, from 6.5 to 9.0, from 6.7 to 9.0, from 7.0 to 9.0, from 7.3 to 9.0, from 7.5 to 9.0, from 7.7 to 9.0, from 8.0 to 9.0, from 8.5 to 9.0, from 4.0 to 8.7, from 4.3 to 8.7, from 4.5 to 8.7, from 4.7 to 8.7, from 5.0 to 8.7, from 5.3 to 8.7, from 5.5 to 8.7, from 5.7 to 8.7, from 6.0 to 8.7, from 6.3 to 8.7, from 6.5 to 8.7, from 6.7 to 8.7, from 7.0 to 8.7, from 7.3 to 8.7, from 7.5 to 8.7, from 7.7 to 8.7, from 8.0 to 8.7, from 8.3 to 8.7, from 4.0 to 8.5, from 4.3 to 8.5, from 4.5 to 8.5, from 4.7 to 8.5, from 5.0 to 8.5, from 5.3 to 8.7, from 5.5 to 8.5, from 5.7 to 8.5, from 6.0 to 8.5, from 6.3 to 8.5, from 6.5 to 8.5, from 6.7 to 8.7, from 7.0 to 8.5, from 7.3 to 8.5, from 7.5 to 8.5, from 7.7 to 8.5, from 8.0 to 8.5, from 4.0 to 8.3, from 4.3 to 8.3, from 4.5 to 8.3, from 4.7 to 8.3, from 5.0 to 8.3, from 5.3 to 8.7, from 5.5 to 8.3, from 5.7 to 8.3,from 6.0 to 8.3, from 6.3 to 8.3, from 6.5 to 8.3, from 6.7 to 8.7, from 7.0 to 8.3, from 7.3 to 8.3, from 7.5 to 8.3, from 7.7 to 8.3, from 4.0 to 8.0, from 4.3 to 8.0, from 4.5 to 8.0, from 4.7 to 8.0, from 5.0 to 8.0, from 5.3 to 8.0, from 5.5 to 8.0, from 5.7 to 8.0, from 6.0 to 8.0, from 6.3 to 8.0, from 6.5 to 8.0, from 6.7 to 8.0, from 7.0 to 8.0, from 7.3 to 8.0, from 7.5 to 8.0, from 4.0 to 7.7, from 4.3 to 7.7, from 4.5 to 7.7, from 4.7 to 7.7, from 5.0 to 7.7, from 5.3 to 7.7, from 5.5 to 7.7, from 5.7 to 7.7, from 6.0 to 7.7, from 6.3 to 7.7, from 6.5 to 7.7, from 6.7 to 7.7, from 7.0 to 7.7, from 7.3 to 7.7, from 4.0 to 7.5, from 4.3 to 7.5, from 4.5 to 7.5, from 4.7 to 7.5, from 5.0 to 7.5, from 5.3 to 7.5, from 5.5 to 7.5, from 5.7 to 7.5, from 6.0 to 7.5, from 6.3 to 7.5, from 6.5 to 7.5, from 6.7 to 7.5, from 7.0 to 7.5, from 4.0 to 7.3, from 4.3 to 7.3, from 4.5 to 7.3, from 4.7 to 7.3, from 5.0 to 7.3, from 5.3 to 7.3, from 5.5 to 7.3, from 5.7 to 7.3, from 6.0 to 7.3, from 6.3 to 7.3, from 6.5 to 7.3, from 6.7 to 7.3, from 4.0 to 7.0, from 4.3 to 7.0, from 4.5 to 7.0, from 4.7 to 7.0, from 5.0 to 7.0, from 5.3 to 7.0, from 5.5 to 7.0, from 5.7 to 7.0, from 6.0 to 7.0, from 6.3 to 7.0, from 6.5 to 7.0, from 4.0 to 6.7, from 4.3 to 6.7, from 4.5 to 6.7, from 4.7 to 6.7, from 5.0 to 6.7, from 5.3 to 6.7, from 5.5 to 6.7, from 5.7 to 6.7, from 6.0 to 6.7, from 6.3 to 6.7, from 4.0 to 6.5, from 4.3 to 6.5, from 4.5 to 6.5, from 4.7 to 6.5, from 5.0 to 6.5, from 5.3 to 6.5, from 5.5 to 6.5, from 5.7 to 6.5, from 6.0 to 6.5, from 4.0 to 6.3, from 4.3 to 6.3, from 4.5 to 6.3, from 4.7 to 6.3, from 5.0 to 6.3, from 5.3 to 6.3, from 5.5 to 6.3, from 5.7 to 6.3, from 4.0 to 6.0, from 4.3 to 6.0, from 4.5 to 6.0, from 4.7 to 6.0, from 5.0 to 6.0, from 5.3 to 6.0, from 5.5 to 6.0, from 4.0 to 5.7, from 4.3 to 5.7, from 4.5 to 5.7, from 4.7 to 5.7, from 5.0 to 5.7, from 5.3 to 5.7, from 4.0 to 5.5, from 4.3 to 5.5, from 4.5 to 5.5, from 4.7 to 5.5, from 5.0 to 5.5, from 4.0 to 5.3, from 4.3 to 5.3, from 4.5 to 5.3, from 4.7 to 5.3, from 4.0 to 5.0, from 4.3 to 5.0, from 4.5 to 5.0, from 4.0 to 4.7, from 4.3 to 4.7, or from 4.0 to 4.5; in particular, from 4.0 to 6.7, from 5.0 to 6.7, from 7.3 to 9.0, from 5.0 to 9.0, or from 5.0 to 8.0.

[0044] If there is more than one depressant present (e.g., a first depressant may comprise homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), and / or a reaction product thereof with CS2, and a second depressant may comprise a depressant different from the first depressant, which is called an “additional depressant” herein), the converting step may comprise converting a portion or all of each or any depressant.

[0045] If necessary or desired, particularly to improve medium recyclability, the converting of the depressant into a water-insoluble composition may comprise introducing an oxidant into the slurry. According to an embodiment, the oxidant may comprise at least one of an organic peroxide,oxygen, ozone, H2O2, fluorine (F2), chlorine (CI2), bromine (Bn), iodine (I2), nitric acid (HNO3), a nitrate, a nitrite, sulfuric acid (H2SO4), peroxydisulfuric acid (H2S2O8), peroxymonosulfuric acid, (H2SO5), a sulfate, a sulfite, hydrochloric acid (HC1), a hypochlorite, a chlorite, a chlorate, a perchlorate, a permanganate, boric acid (H3BO3), a perborate, nitric oxide (NO), nitrous oxide (N2O), and combinations and reaction products thereof, in particular comprising H2O2.

[0046] According to an embodiment, removing at least a portion of the water-insoluble composition comprises at least one of filtration, centrifugation, and solid / liquid extraction. According to some embodiments, at least 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 100% by weight of the water-insoluble composition may be removed.

[0047] Advantageously, after removing at least a portion of the water-insoluble composition, the (aqueous) medium, typically including or being water, can be recirculated, such as to the ore(s) / mineral(s) slurrying step or the separation step (which may include provision to a separation apparatus).

[0048] The method may be continuous or semi continuous, or batch or semibatch.Depressant:

[0049] The depressant may be water compatible (in particular, water soluble or water miscible) and / or may comprise homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof:where C* is a chiral carbon and where: R1and R7are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R1and R7together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R1and R7are connected; X is: >C(=O), -CH2- or -CN; R2is (i) absent when X represents -CN, or is: (ii) a hydrogen atom, (iii) -OR3, where: R3is a hydrogen atom; an aromatic ring optionally comprising one or moreheteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or (iv) - NR4R , where: R4and R3are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R4and R5together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R4and R3are connected; and n is an integer from 1 to 4, for example from 2 to 4 or from 2 to 3, provided that, when X is >C(=O), when R2is -OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2.

[0050] Because cysteine is typically not an effective depressant and because homocysteine is separately itemized, the above text following Formula (I) is written to include a proviso excluding cysteine and homocysteine from Formula (I).

[0051] According to certain embodiments, the depressant can advantageously include homocysteine (2-amino-4-sulfanylbutanoic acid) or derivatives thereof, in particular L- homocysteine, D-homocysteine, or racemic mixtures of homocysteine. Typically, at least L- homocysteine can be present. Additionally or alternatively, the depressant can include a reaction product of homocysteine and CS2, or a metal salt thereof, in particular 2-amino-4- sulfanylsulfanylidenethiobutanoic acid, in which the mercaptan of homocysteine is converted into a hydrogen trithiocarbonate, or an alkali (e.g, lithium, sodium, potassium) or alkaline earth (e.g., calcium, magnesium) metal salt thereof.

[0052] Cysteine, homocysteine, the mercaptans of Formula (I), and the reaction products thereof with CS2 are referred to as functionalized mercaptans, because, in addition to the pendant -SH moiety, they also comprise at least one pendant amine moiety, such as -NR'R7.

[0053] Additionally or alternatively, in embodiments of Formula (I), one, some, or all of the following may be satisfied, in particular:• n can be from 1 to 3, from 2 to 4, from 2 to 3; advantageously n can include or be 2;• X can be >C=O;• R2can be -OR3, and R3can be a hydrogen atom or a saturated hydrocarbon moiety having from 1 to 8 carbon atoms, or from 1 to 4 carbon atoms, optionally comprising a heteroatom; advantageously, n can be a hydrogen atom; and• Rland R7can individually be a hydrogen atom or a saturated hydrocarbon moiety having from 1 to 8 carbon atoms, or from 1 to 4 carbon atoms, optionally comprising a heteroatom, advantageously, R1and R7can both be a hydrogen atom;• with the proviso that Formula (I) does not include cysteine (or homocysteine, as itemized separately).

[0054] If a metal salt, the metal may comprise an alkali metal or alkaline earth metal; in particular an alkali metal. Non-limiting examples of such metals include Na, Li, K, Rb, Cs, Be, Ba, Mg, Sr, and Ca. The metal may advantageously comprise Na, K, Li, Ca, Mg, or mixtures thereof; in particular comprising Na and / or K.

[0055] According to an embodiment, the depressant may comprise homocysteine or a metal (an alkaline metal or alkaline earth metal) salt thereof, which specifically includes L-homocysteine and a sodium or disodium salt thereof.

[0056] In some situations, the depressant may include one or more additional depressants, aside from the homocysteine, metal salt or derivative thereof, compound having structure of Formula (I), reaction product thereof with CS2, or combination thereof, including those characterized herein specifically as “additional depressants.”Ore to be Separated

[0057] Although the compositions and methods disclosed herein may be generically used to separate any of a variety of desired ores and / or minerals out from others, a specific ore to be separated may comprise a Cu-bearing mineral, with the depressant selectively targeted to assist the Cu-bearing mineral(s) to phase separate in the separation step. In froth flotation, the phase separation may be to sink, under the action of gravity, or enable phase-based separation by other means, such as by centrifugation.

[0058] In particular, the ore to be separated may comprise both a Cu-bearing mineral and a Mobearing mineral, with the depressant selectively causing the Cu-bearing mineral(s) to phase separate in the separation medium, relative to the Mo-bearing mineral(s). The Cu-bearing mineral may comprise at least one of chalcopyrite (CuFeSi), bornite (Cu5FeS4), covellite (CuS), chalcocite (CU2S), and a combination thereof; in particular comprising chalcopyrite. The Mo-bearing mineral may comprise molybdenite (M0S2).

[0059] Although ores from various places may contain different ratios of metal-bearing minerals, a weight ratio of Cu-bearing mineral(s) to Mo-bearing mineral(s) in the disclosed method(s) canbe from about 5:1 to about 100000:1 w / w (e. , from about 5:1 to about 50000:1, from about 5:1 to about 30000:1, from about 5:1 to about 20000:1, from about 5:1 to about 10000:1, from about 5:1 to about 7500:1, from about 5:1 to about 5000:1, from about 5:1 to about 2500:1, from about 5:1 to about 1000:1, from about 5:1 to about 500:1, from about 5:1 to about 250:1, from about 5:1 to about 100:1, from about 10:1 to about 100000:1, from about 10:1 to about 50000:1, from about 10:1 to about 30000:1, from about 10:1 to about 20000:1, from about 10:1 to about 10000:1, from about 10:1 to about 7500:1, from about 10:1 to about 5000:1, from about 10:1 to about 2500:1, from about 10:1 to about 1000:1, from about 10:1 to about 500:1, from about 10:1 to about 250:1, from about 10:1 to about 100:1, from about 50:1 to about 100000:1, from about 50:1 to about 50000:1, from about 50:1 to about 30000:1, from about 50:1 to about 20000:1, from about 50:1 to about 10000:1, from about 50:1 to about 7500:1, from about 50:1 to about 5000:1, from about 50:1 to about 2500:1, from about 50:1 to about 1000:1, from about 50:1 to about 500:1, from about 50:1 to about 250:1, from about 100:1 to about 100000:1, from about 100:1 to about 50000:1, from about 100:1 to about 30000:1, from about 100:1 to about 20000:1, from about 100:1 to about 10000:1, from about 100:1 to about 7500:1, from about 100:1 to about 5000:1, from about 100:1 to about 2500:1, from about 100:1 to about 1000:1, from about 100:1 to about 500:1, from about 500:1 to about 100000:1, from about 500:1 to about 50000:1, from about 500:1 to about 30000:1, from about 500:1 to about 20000:1, from about 500:1 to about 10000:1, from about 500:1 to about 7500:1, from about 500:1 to about 5000:1, from about 500:1 to about 2500:1, from about 1000:1 to about 50000:1, from about 1000:1 to about 30000:1, from about 1000:1 to about 20000:1, from about 1000:1 to about 10000:1, from about 1000:1 to about 7500:1, or from about 1000:1 to about 5000:1).

[0060] Non-limiting examples of ores and / or minerals that may be separated using the depressant disclosed herein are those that may include both Cu and Mo. Additionally or alternatively, the ore(s) and / or mineral(s) may comprise Fe. It should be understood that these minerals may include mixtures of minerals, e.g., the Cu may be in one mineral and the Mo may be in another mineral and the present method may be used to separate a mixture of these minerals into a Cu-rich component and an Mo-rich component. Thus, the present method may recover as much Cu and Mo as possible while selectively separating Fe (and other non-metallic minerals such as carbonates, silicates, etc.) and / or Mo in general from all other minerals. In addition, Au alone or Cu-Au and Ag-Au minerals may be recovered while selectively separating Fe and other less valuable minerals.The main targets can be Mo and Au when they are present with Cu or Ag, such that valuable streams of Mo, Au, Ag and / or Cu may be recovered. The flotation compositions disclosed herein may be used to separate Cu-Mo and / or Cu-Au and / or Au-Mo and / or Ag-Au ores. Non limiting examples of ores that may be separated by use of the present method are sulfide mineral including, among others, chalcopyrite (CuFeSz), bornite (CusFeS^, covellite (CuS), chalcocite (CuzS) and molybdenite (M0S2). The most common co-existing minerals are chalcopyrite and molybdenite. The relative ratios of these ores may be from 60:40 to 99.999:0.001 by weight (e.g., from 70:30 to 99.999:0.001 by weight, from 80:20 to 99.999:0.001 by weight, from 90:10 to 99.999:0.001 by weight, from 95:5 to 99.999:0.001 by weight, from 99:1 to 99.999:0.001 by weight, from 99.9:0.1 to 99.999:0.001 by weight, from 60:40 to 99.99:0.01 by weight, from 70:30 to 99.99:0.01 by weight, from 80:20 to 99.99:0.01 by weight, from 90:10 to 99.99:0.01 by weight, from 95:5 to 99.99:0.01 by weight, or from 99:1 to 99.99:0.01 by weight).Effective Amount of Depressant

[0061] As disclosed herein, the disclosed depressant(s) comprising homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof may preferentially react and / or complex with copper contaminant sulfide minerals, thus causing them to sink under this fluence of gravity, or to phase-separate due to the action of a centrifuge for example. Effective amount may be determined based on the degree of separation to be attained and / or by the nature of the selective and comparative metal(s) in the mineral(s) to be separated. For instance, the effective amount may be enough depressant to effect a recovery of at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 99% of a weight of a desired mineral from an ore, based on the weight of the desired mineral in the ore.

[0062] The amount of the depressant may be selected according to a weight of the relevant mineral(s) in the ore and / or based on other considerations relevant to separation (and / or to medium recycle). For example, the depressant may comprise from 10 g / ton to 100 kg / ton (e.g., from 10 g / ton to 50 kg / ton, from 10 g / ton to 25 kg / ton, from 10 g / ton to 10 kg / ton, from 10 g / ton to 5 kg / ton, from 10 g / ton to 3 kg / ton, from 10 g / ton to 1 kg / ton, from 10 g / ton to 500 g / ton, from 100 g / ton to 100 kg / ton, from 100 g / ton to 50 kg / ton, from 100 g / ton to 25 kg / ton, from 100 g / ton to 10 kg / ton, from 100 g / ton to 5 kg / ton, from 100 g / ton to 3 kg / ton, from 100 g / ton to 1 kg / ton, from 100 g / ton to 500 g / ton, from 300 g / ton to 100 kg / ton, from 300 g / ton to 50 kg / ton, from 300 g / ton to 25kg / ton, from 300 g / ton to 10 kg / ton, from 300 g / ton to 5 kg / ton, from 300 g / ton to 3 kg / ton, from 300 g / ton to 1 kg / ton, from 500 g / ton to 100 kg / ton, from 500 g / ton to 50 kg / ton, from 500 g / ton to 25 kg / ton, from 500 g / ton to 10 kg / ton, from 500 g / ton to 5 kg / ton, from 500 g / ton to 3 kg / ton, from 500 g / ton to 1 kg / ton, from 1 kg / ton to 100 kg / ton, from 1 kg / ton to 50 kg / ton, from 1 kg / ton to 25 kg / ton, from 1 kg / ton to 10 kg / ton, from 1 kg / ton to 5 kg / ton, or from 1 kg / ton to 3 kg / ton; in particular from 10 g / ton to 100 kg / ton, from 100 g / ton to 30 kg / ton, from 500 g / ton to 10 kg / ton, or from 100 g / ton to 5 kg / ton) of the total amount of relevant (e.g., Cu-containing) mineral(s) in the ore to be separated.Additional Depressants:

[0063] Although the disclosed depressant(s) of homocysteine, a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof are believed to be effective alone, in some embodiments one or more additional depressants may be added under the methods described herein. Non-limiting examples of such other depressants can include, but are not necessarily limited to, sodium hydrosulfide (NaSH), Nokes reagent (a reaction product of NaOH and phosphorous pentasulfide), sodium thioglycolate, carboxymethyl cellulose, and disodium carboxymethyl trithiocarbonate (such as commercially available under the tradename Orfom® D8 from Chevron Phillips Chemical), lime (calcium oxide and / or calcium hydroxide), sodium cyanide, zinc sulfate, and combinations thereof.Collectors

[0064] If necessary for the particular minerals desired to be separated and based on other factors such as the electrochemistry of the process, the method may further comprise introducing a collector to the separation apparatus. The collector may be used to selectively enhance flotation characteristics, for example of Mo-containing minerals, relative to Cu-containing minerals. The nature and effective amount of such collectors can be chosen based on a number of factors, including the metal(s) to be selectively collected and / or the metal(s) from which they are to be separated.

[0065] Non-limiting examples of collectors can include one or more of xanthates, xanthate esters, xanthogen formates, dithiophosphates, monothiophosphates, dithiophosphinates, dithiocarbamates, mercaptobenzothiazoles, polysulfides, thionocarbamates, or combinations thereof. Non-limiting examples of specific compounds can include, but are not necessarily limited to, ethyl xanthate, butyl xanthate, sodium isobutyl xanthate, sodium di-ethyldithiophosphate,potassium di-isobutyl dithiophosphate, potassium di-sec-butyl dithiophosphate, diisobutyl monothiophosphate, sodium diisobutyl dithiophosphinate, potassium n-decyl dithiocarbamate, O- isopropyl thionocarbamates, and the like, and combinations thereof.

[0066] Additionally or alternatively, when a collector is present, the collector may comprise linear primary mercaptans such as n-dodecyl mercaptan (NDM) branched tertiary mercaptans such as tert-dodecyl mercaptan (TDM), or the like, or combinations thereof.

[0067] Further additionally or alternatively, when a collector is present, the collector may further comprise, consist of, or consist essentially of at least one C6-C12 branched or straight chained alkane(s) and / or at least one branched or straight chained C6-C14 alkene, particularly dodecane, dodecene, and / or tetradecene.

[0068] Still further additionally or alternatively, when a collector is present, the collector may comprise, consist of, or consist essentially of one or more of the collectors described in U.S. Serial No. 63 / 434,110, the disclosure of which is incorporated by reference herein in its entirety for all purposes, but in particular for its disclosure relevant to the following collectors:1) a combination of at least one mercaptan (a) having a structure i) and / or ii):N i) R9; ii)H2 where R8and R9are independently selected from branched or straight chain C1-C23 alkyl groups, or from Cl -Cl 8, more preferably from Cl -Cl 5, or from Cl -CIO alkyl groups; and where Ri0is a C6-C24, or C6-C20, more preferably C6-C16, particularly C6-C14 branched alkyl group; wherein an average number of carbon groups in the a) mercaptan is from 6 to 24, or from 6-19, more preferably from 6-16, or from 6-14, where preferably a) is 2-butyl-l -octanethiol, 2- dodecanethiol and / or 2-ethyl-l -decanethiol; and one or more aromatic, aliphatic or polyalkylene oxide compounds (b) comprising from 4 to 100 carbon atoms, and having one or two -OH groups, particularly polypropylene glycol, pine oil, cresylic acid, and / or methyl isobutyl carbinol;2) at least one sulfide (c) having a structure Ru-S-R12, where R11and R12are independently selected from C1-C16, or C1-C14, or C1-C12, particularly C1-C10 straight chainand branched alkyl groups, wherein an average number of carbons in the (c) sulfide is from 10-24, or from 12-22, or from 12-20, particularly from 14-18; and / or3) a combination of at least one trithiocarbonate (d) having a structure:, salt thereof; or combination thereof, where R13and R14are independently selected from branched or straight chain C1-C23 alkyl groups, preferably from C1-C18, more preferably from C1-C15, most preferably from Cl -CIO alkyl groups, wherein an average number of carbon groups in the mercaptan is from 6 to 24, preferably from 6-19, more preferably from 6-16, most preferably from 6-14; and where R15is a C6-C24 branched alkyl group, preferably C6-C20, more preferably C6-C16, most preferably C6-C14, branched alkyl group; and one or more aromatic, aliphatic or polyalkylene oxide compounds (e) comprising, consisting of, or consisting essentially of from 4 to 100 carbon atoms, and having one or two - OH groups.

[0069] Mixtures and / or reaction products of any of these aforementioned collectors are also contemplated.

[0070] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

[0071] In some embodiments, the invention herein can be construed as excluding any element or process step that does not materially affect the basic and novel characteristics of the compositions, methods for making the compositions, methods for using the compositions, and articles prepared from the compositions. Additionally, in some embodiments, the invention can be construed as excluding any element or process step not specified herein.

[0072] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not necessarily intended to be limited to the details shown. Rather,various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

[0073] Additionally or alternatively, the invention may include, but is not necessarily limited to, the following non-limiting embodiments.

[0074] Embodiment 1. A method for separation of minerals in an ore, comprising: introducing into a separation apparatus a slurry comprising: the ore to be separated, water, and an effective amount of a depressant comprising: homocysteine or a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof:Formula (I) where C* is a chiral carbon and where: R1and R7are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R1and R7together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R1and R7are connected; X is: >C(=O), -CH2- or -CN; R2is (i) absent when X represents -CN, or is: (ii) a hydrogen atom, (iii) -OR3, where: R3is a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or (iv) - NR4R5, where: R4and R’ are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R4and R5together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R4and R5are connected; and n is an integer from 1 to 4, for example from 2 to 4 or from 2 to 3, provided that, when X is >C(=O), when R2is-OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2; and separating a portion or all of the ore into a plurality of minerals.

[0075] Embodiment 2. The method of embodiment 1, wherein the separating step is flotation separation.

[0076] Embodiment 3. The method of embodiment 1 or embodiment 2, wherein the separating step comprises sparging the slurry with a gas.

[0077] Embodiment 4. The method of any of embodiments 1-3, wherein the metal comprises an alkaline metal or alkaline earth metal.

[0078] Embodiment 5. The method of embodiments 1-4, further comprising introducing a reducing agent prior to the separating step.

[0079] Embodiment 6. The method of embodiment 5, wherein the reducing agent comprises hydrazine, urea, NazS, hydroxylamine, or a combination thereof.

[0080] Embodiment 7. The method of any of embodiments 1-6, further comprising removing at least a portion of the depressant or the metal salt or derivative thereof from the slurry after the separating step.

[0081] Embodiment 8. The method of embodiment 7, wherein the removing comprises converting at least a portion of the depressant or the water compatible metal salt or derivative thereof into a water-insoluble composition, and separating out at least a portion of the waterinsoluble composition.

[0082] Embodiment 9. The method of embodiment 7 or embodiment 8, wherein after the removing, at least a portion of the water is recirculated to the separation apparatus.

[0083] Embodiment 10. The method of embodiment 8 or embodiment 9, wherein the converting of the depressant or the water compatible metal salt or derivative thereof into a waterinsoluble composition comprises adjusting a pH of the slurry to from about 4 to about 9.

[0084] Embodiment 11. The method of any of embodiments 8-10, wherein the converting of the depressant or the water compatible metal salt or derivative thereof into a water-insoluble composition comprises introducing an oxidant into the slurry.

[0085] Embodiment 12. The method of embodiment 11, wherein the oxidant comprises at least one of an organic peroxide, oxygen, ozone, H2O2, fluorine (F2), chlorine (CI2), bromine (Br2), iodine (I2), nitric acid (HNO3), a nitrate, a nitrite, sulfuric acid (H2SO4), peroxy disulfuric acid (H S2O8), peroxymono sulfuric acid, (H2SO5), a sulfate, a sulfite, hydrochloric acid (HC1), ahypochlorite, a chlorite, a chlorate, a perchlorate, a permanganate, boric acid (H3BO3), a perborate, nitric oxide (NO), nitrous oxide (N2O), and combinations and reaction products thereof, in particular comprising H2O2.

[0086] Embodiment 13. The method of any of embodiments 7-12, wherein removing the water-insoluble composition comprises at least one of filtration, centrifugation, and solid / liquid extraction.

[0087] Embodiment 14. The method of any of embodiments 1-13, wherein the depressant comprises homocysteine, an alkali metal or alkaline earth metal salt thereof, a reaction product thereof with CS2, or a combination thereof.

[0088] Embodiment 15. The method of any of embodiments 1-14, further comprising collecting one or more of the plurality of minerals from the separation step.

[0089] Embodiment 16. The method of any of embodiments 1-15, wherein the ore to be separated comprises a Cu-bearing mineral, and the depressant selectively causes the Cu-bearing mineral to phase separate in the separation apparatus.

[0090] Embodiment 17. The method of any of embodiments 1-16, wherein the ore to be separated comprises a Cu-bearing mineral and a Mo-bearing mineral, and the depressant selectively causes the Cu-bearing mineral to phase separate in the separation apparatus relative to the Mo-bearing mineral.

[0091] Embodiment 18. The method of embodiment 16 or embodiment 17, wherein, the Cubearing mineral comprises at least one of chalcopyrite (CuFeS2), bornite (CusFeS^, covellite (CuS), chalcocite (C112S), and a combination thereof; in particular comprises chalcopyrite.

[0092] Embodiment 19. The method of embodiment 17 or embodiment 18, wherein the Mobearing mineral comprises molybdenite (M0S2).

[0093] Embodiment 20. The method of any of embodiments 1-19, wherein the method is continuous or semi-continuous or batch or semibatch.EXAMPLES

[0094] As used herein, “NDM” represents a commercial n-dodecyl mercaptan product. Although the “dodecyl” descriptor seems to indicate only C12 linear primary thiols, it should be understood that the commercial product typically comprises a range of carbon numbers with 12 as the predominant or target number of carbons and that the commercial product may contain some level of branched primary thiols and perhaps even secondary thiols.Example 1

[0095] Inhibition of chalcopyrite (CuFeSz) flotation by L-homocysteine in the presence of NDM was demonstrated by microflotation experiments in a Hallimond tube. In these experiments, Mineral 1 was used to evaluate depressant performance. The composition of Mineral 1 was determined by X-ray diffraction using a Rigaku SmartLab™ diffraction platform (Cu Ka ~1.5418 A, ~40 kV, ~40 mA). Phase identification was done in MDI Jade™ program with ICDD PDF 4+™ database (2021 release). Rietveld quantification also performed with whole pattern fitting in Jade 7.1. Mineral 1 composition is shown in Table 1 as being -84.9 wt% chalcopyrite.Table 1: Composition of Mineral 1 as determined by X-ray diffraction.

[0096] A Mineral 1 sample containing particle sizes between -75-150 microns was added to water to make a slurry containing approximately 1% solids by weight. The slurry pH was modified by NaOH or HC1 addition before adding L-homocysteine (-100 microliters of -8.2 wt% aqueous solution) and NDM (-4 microliters neat). Methyl isobutyl carbinol (MIBC) was added as a frother (-2 microliters neat) before bubbling N2 gas or air through the slurry at -40 mL / minute. The gas caused the hydrophobic particles to float to the surface to be collected as a concentrate, while the hydrophilic particles remained in the bottom of the Hallimond tube. The total flotation time was -5 minutes. For comparison, experiments without L-homocysteine (L-HCY) and / or NDM were performed. In all experiments, the frother MIBC was required to provide the gas bubbles sufficient mechanical strength to carry mineral particles effectively. The results are shown in Figure 1 and Figure 2, which demonstrate that homocysteine is an effective inhibitor of the flotation of the minerals that compose Mineral 1.

[0097] It is interesting to note that NDM can act as a collector for Mineral 1 , leading to recoveries of -70-80% at pH values between about 4 and about 12. Figure 1 shows that the experiments without NDM as collector resulted in minimal chalcopyrite recovery.Example 2

[0098] Further microflotation experiments were performed with the disodium salt of L- homocysteine (2Na- HCY), D, L-homocysteine, the racemic mixture of D- and L- homocysteine(DL-HCY), D,L-cysteine, a racemic mixture of D- and L- cysteine (DL-CYS), and the disodium salt of the dithiol 3,6-bis(2-mercaptoethyl)-2,5-piperazinedione (2Na-MEPZD) at pH values between -9 and -11. NDM (-3 microliters) and MIBC (-2 microliters) were used as collector and frother, respectively. Flotation time was 1 minute. The dosages of L-HCY, DL-HCY and DL- CYS were -40 micromol per 2 grams of Mineral 1. The dosages for 2Na-HCY and 2Na-MEPZD were ~60 micromol per 2 grams of Mineral 1. It is worth noting that MEPZD alone was not sufficiently soluble in water and was converted to a salt in order to allow enough solubility for the experiments. The results are shown in Figure 3.Example 3

[0099] The efficacy of L-homocysteine (L-HCY) to inhibit recovery of Cu- and Fe-containing minerals was demonstrated at lab-scale using a Fe-containing Cu-Mo concentrate from an active South American mine. The experiments were carried out using a -2.4-L Denver-type flotation machine and a solids density of -45%. The concentrate was generated from a rougher flotation test that resulted in mineral particles with a D80 of -62 micrometers and a head grade of -30.2 wt% Cu, -20.4 wt% Fe and -0.077 wt% Mo. An initial test was run with a -43 wt% aqueous sodium hydrosulfide (NaSH) solution at an active ingredient dosage of -7.53 kg / ton. L-HCY was used as a fresh -10 wt% aqueous solution and tested at different dosages of active ingredient as shown in Table 2. The initial pulp pH was -6.6, conditioning time after depressant addition was -2 minutes, and flotation time was -10 minutes. Tap water was used for flotation and nitrogen to generate the froth. No additional frother or collector were added in addition to the remnants from the rougher flotation.

[0100] As seen in Table 2, L-HCY resulted in lower Cu recovery than NaSH at the same dosage. It also demonstrated effective Cu depressant activity at the lower -4.0 kg / ton dosage. Fe recovery was also suppressed using L-HCY.Table 2: Cu, Mo and Fe recovery using NaSH and L-HCY as depressants.Examples 4a-4h

[0101] Pure L-homocysteine (L-HCY) was soluble in water up to ~10 wt%. However, solids can precipitate in a few hours. On the other hand, depressant formulation stability for mining can be improved by converting L-HCY into its alkaline salts. For example, the disodium salt of L- HCY (2Na-HCY) was soluble in water up to ~35 wt%. A similar ~23 wt% 2Na-HCY sample (Example 4e) exhibited consistent shelf-life for at least ~2 years. Similarly, the dipotassium salt of L-HCY (2K-HCY) was soluble in water at ~60 wt%, also showing a robust shelf-life. A similar practice can be used to generate stable aqueous formulations of L-cysteine (L-CYS), which has a water solubility of approximately 10 wt% at room temperature, which can be improved to -50 wt% or greater when reacted with a sodium base. Another amino acid proposed in prior art as depressant is methionine, which is only soluble in water up to ~5 wt%. This concentration represents too low of an active ingredient content to make its use as a commercial depressant practical. For improved stability of these formulations, it can be important to avoid oxygen exposure leading to product decomposition. Such decomposition can result in the potential release of toxic species, in the case of pure amino acid formulations.

[0102] To prove that the active ingredients providing depressing effect to the formulations (thiols in the case of L-HCY and L-CYS, and thiolates for the alkaline salts) remain in solution, NMR experiments were performed on the samples indicated in Table 3. The compounds in solutions were identified using *H, ’H COSY, *H-13C HSQC, and!H-13C HMBC liquid-state NMR techniques performed on a Bruker NEO 400™ spectrometer. The presence of monosulfide in L- HCY solution was confirmed by *H-13C HSQC / HMBC NMR, but was not quantified due to peak overlap in the *H spectrum and too low a concentration to be detected by13C NMR.

[0103] A solid species was allowed to precipitate from the ~10 wt% L-HCY solution overnight without additional stimuli. The solid was determined to be composed of disulfide and thiol functional groups as indicated in Table 3. Characterization of the solid species was performed after dissolution in a large quantity of deuterium oxide by *H liquid-state NMR performed on a Bruker NEO 400™ spectrometer. The composition of the solid was also confirmed by 'H-^C CP- MAS solid-state NMR performed on a Bruker A VIII™ 300 WB spectrometer. The solid was ground into a powder and pack into a ~2.5 mm MAS rotor. The MAS spinning rate was ~10 KHz.

[0104] Without being bound by theory, any discrepancy between nominal compositions and characterization was believed to be due to counterion (Na and K) mass not being accounted for in NMR spectra used for quantification.Table 3: Sulfurized species in aqueous depressant formulations, and solid precipitate from ~10 wt% L-HCY formulation.

Claims

CLAIMSWhat is claimed is:

1. A method for separation of minerals in an ore, comprising: introducing into a separation apparatus a sluny comprising: the ore to be separated, water, and an effective amount of a depressant comprising: homocysteine or a metal salt or derivative thereof, a compound having structure of Formula (I), a reaction product thereof with CS2, or a combination thereof:Formula (I) where C* is a chiral carbon and where:R1and R7are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R1and R7together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R1and R7are connected;X is: >C(=O), -CH2- or -CN;R2is (i) absent when X represents -CN, or is:(ii) a hydrogen atom,(iii) -OR3, where: R3is a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturated or unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or(iv) -NR4R3, where: R4and R3are identical or different and are individually: a hydrogen atom; an aromatic ring optionally comprising one or more heteroatoms; or a nonaromatic, linear, branched or cyclic, saturatedor unsaturated, hydrocarbon moiety having 1 to 12 carbon atoms and optionally comprising one or more heteroatoms, or R4and R3together form an optionally substituted heterocyclic ring structure having from 3 to 18 carbon atoms and optionally comprising one or more heteroatoms in addition to the nitrogen to which R4and R5are connected; and n is an integer from 1 to 4, for example from 2 to 4 or from 2 to 3, provided that, when X is >C(=O), when R2is -OH, and when R1and R7are each hydrogen, n is not equal to 1 or 2; and separating a portion or all of the ore into a plurality of minerals.

2. The method of claim 1, wherein the separating step is flotation separation.

3. The method of claim 1 or claim 2, wherein the separating step comprises sparging the slurry with a gas.

4. The method of any of claims 1-3, wherein the metal comprises an alkaline metal or alkaline earth metal.

5. The method of claims 1-4, further comprising introducing a reducing agent prior to the separating step.

6. The method of claim 5, wherein the reducing agent comprises hydrazine, urea, Na2S, hydroxylamine, or a combination thereof.

7. The method of any of claims 1-6, further comprising removing at least a portion of the depressant or the metal salt or derivative thereof from the slurry after the separating step.

8. The method of claim 7, wherein the removing comprises converting at least a portion of the depressant or the water compatible metal salt or derivative thereof into a water-insoluble composition, and separating out at least a portion of the water-insoluble composition.

9. The method of claim 7 or claim 8, wherein after the removing, at least a portion of the water is recirculated to the separation apparatus.

10. The method of claim 8 or claim 9, wherein the converting of the depressant or the water compatible metal salt or derivative thereof into a water-insoluble composition comprises adjusting a pH of the slurry to from about 4 to about 9.

11. The method of any of claims 8-10, wherein the converting of the depressant or the water compatible metal salt or derivative thereof into a water-insoluble composition comprises introducing an oxidant into the slurry.

12. The method of claim 11, wherein the oxidant comprises at least one of an organic peroxide, oxygen, ozone, H2O2, fluorine (F2), chlorine (CI2), bromine (B ), iodine (I2), nitric acid (HNO3), a nitrate, a nitrite, sulfuric acid (H2SO4), peroxydisulfuric acid (H2S2O8), peroxymonosulfuric acid, (H2SO5), a sulfate, a sulfite, hydrochloric acid (HC1), a hypochlorite, a chlorite, a chlorate, a perchlorate, a permanganate, boric acid (H3BO3), a perborate, nitric oxide (NO), nitrous oxide (N2O), and combinations and reaction products thereof, in particular comprising H2O2.

13. The method of any of claims 7-12, wherein removing the water-insoluble composition comprises at least one of filtration, centrifugation, and solid / liquid extraction.

14. The method of any of claims 1-13, wherein the depressant comprises homocysteine, an alkali metal or alkaline earth metal salt thereof, a reaction product thereof with CS2, or a combination thereof.

15. The method of any of claims 1-14, wherein the ore to be separated comprises a Cubearing mineral, and the depressant selectively causes the Cu-bearing mineral to phase separate in the separation apparatus.

16. The method of any of claims 1-15, wherein the ore to be separated comprises a Cubearing mineral and a Mo-bearing mineral, and the depressant selectively causes the Cu-bearing mineral to phase separate in the separation apparatus relative to the Mo-bearing mineral.

17. The method of claim 15 or claim 16, wherein, the Cu-bearing mineral comprises at least one of chalcopyrite (CuFeS2), bornite (CusFeS^, covellite (CuS), chalcocite (C112S), and a combination thereof; in particular comprises chalcopyrite.

18. The method of claim 16 or claim 17, wherein the Mo-bearing mineral comprises molybdenite (M0S2).

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