Thiol salt microemulsion collector for mineral flotation

Abstract

Methods and compositions for improving froth flotation processes for removing mineral values from aqueous solutions are provided. According to the method, a thiolate microemulsion is used for improving the separation effect of the collecting agent. A method of enhancing collector performance in froth flotation separation of an ore in a medium, the method comprising the steps of forming a slurry by blending a collector microemulsion, the ore in the medium, and optionally other additives, and removing concentrate from the ore by spraying the slurry; wherein the collector microemulsion comprises a continuous phase and a dispersed phase, the continuous phase being an aqueous carrier fluid, the dispersed phase comprising a thiol salt.

Description

Technical Field

[0001] The present invention relates to a novel mercaptide microemulsion collector for concentrating valuable minerals from an ore body. Background Art

[0002] The present invention generally relates to mineral recovery by froth flotation operations. In one aspect, the present invention relates to ore flotation processes, for example, those involving the recovery of metals (e.g., Cu, Mo, Pb, Co, Zn, Ni, Au, Ag, Pt, Pd) using novel mercaptide microemulsions.

[0003] Froth flotation separations can be used to separate solids from solids (e.g., components of an ore), or liquids from other liquids or solids (e.g., separating bitumen from oil sands). When used with solids, froth flotation typically also involves pulverizing the solids (grinding by dry or wet grinding, etc.). When solids are pulverized, they are more easily dispersed in an aqueous slurry, and small solid hydrophobic particles are able to adhere more easily to the jet bubbles.

[0004] The flotation process is used to recover and concentrate valuable minerals from ores. In the froth flotation process, the ore is crushed and wet-milled to obtain a pulp. The pulp is then aerated to produce froth on the surface. Minerals adhering to the bubbles or froth are skimmed or otherwise removed, and the froth containing the minerals is collected and further processed to recover the desired minerals. Other valuable minerals can be recovered from the tailings product separated from the mineral-containing froth during the flotation process.

[0005] A variety of additives can be added to improve the efficiency of froth flotation separation. Collectors are additives that adhere to the surface of the concentrate particles and enhance their overall hydrophobicity. Subsequently, the bubbles preferentially adhere to the hydrophobized concentrate, and then they are more easily removed from the slurry than other components that are less hydrophobic or hydrophilic. Therefore, the collector effectively separates the specific components from the slurry, while the remaining tailings that have not been modified by the collector are retained in the slurry. Typical mineral flotation collectors include xanthates, amines, alkyl sulfates, hydrocarbons, sulfonates, dithiocarbamates, dithiophosphates and mercaptans. Other additives may include activators, frothers and / or depressants, which enhance the selectivity of the flotation step and facilitate the removal of the concentrate from the slurry.

[0006] The performance of the collector can be improved by the use of an activator. Activators are a variety of chemicals that enhance the effectiveness of the collector in one or more ways. One way an activator works is by increasing the dispersibility of the collector in the slurry. Another way is by increasing the adhesion between the concentrate and the gas bubbles. A third way is by increasing the selectivity of the material that adheres to the gas bubbles.

[0007] Frothing agents or frothers are chemicals added to the process that change the surface tension of the liquid and thus the characteristics of the jet bubbles. Frothing agents act to stabilize the bubbles, keeping them well dispersed in the slurry, and form a stable foam layer that can be removed before the bubbles burst. Ideally, the frother should not enhance the flotation of unwanted materials and the foam should have a tendency to break when removed from the flotation unit.

[0008] Collectors are usually added before frothers, and they need not chemically interfere with each other. Commonly used frothers include pine oil, fatty alcohols such as MIBC (methyl isobutyl carbinol), polyethylene glycol, polyethylene glycol ethers, polypropylene glycol ethers, polyoxyalkanes, cresol acids (xylenols), commercially available alcohol blends (such as those produced from 2-ethylhexanol) and any combination thereof.

[0009] Collectors adhere to the surface of concentrate particles. Their effectiveness depends on the nature of the interaction that occurs between the collector and the concentrate particles. Unfortunately, conflicting chemical principles are at work in froth flotation separations, which make such interactions difficult. Since froth flotation separations rely on the separation of more hydrophobic particles from more hydrophilic particles, the slurry medium typically contains water. However, since many commonly used collectors are inherently hydrophobic, they do not disperse well in water, which makes their interaction with concentrate particles difficult or suboptimal.

[0010] Although ore flotation technology has reached a considerable level of sophistication, a continuing goal of the ore recovery industry is to increase the productivity of ore flotation processes and, most importantly, to provide specific processes that are selective for one ore or one metal, respectively, over other ores or other metals present in the material being processed in the process. Therefore, alternative collector compositions are being developed to increase ore recovery by flotation.

[0011] Heavy thiolates have unique chemical properties that make them particularly suitable for applications such as mineral recovery, metal protection, surface modification, polymer functionalization, etc. However, heavy thiolates also exhibit a strong odor and are immiscible with water, which limits their use in many applications. Summary of the invention

[0012] According to the present invention, it has been found that the recovery of minerals containing metals (Cu, Mo, Pb, Co, Zn, Ni, Au, Ag, Pt, Pd and / or Rh) can be improved by using mercaptide microemulsions as collectors in froth flotation processes. One object of the present invention is to reduce the perceived odor of heavy mercaptans (liquids) by using mercaptides in which the thiol groups have been converted into ionic mercaptides. Heavy mercaptides (solids) also have improved compatibility with water, allowing the preparation of water-based formulations with unique microstructures (microemulsions). Water-based mercaptide microemulsions exhibit a lower perceived odor than mercaptans and their activity is enhanced due to the increased interfacial area typical of the microstructure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Graph showing mineral recovery as a function of pH for the flotation of pyrite and chalcopyrite using a sodium mercaptide microemulsion (Sample 5) in a Hallimond tube.

[0014] Figure 2 and 3 Recovery / grade plot of copper and molybdenum from Cu-Mo ores using sodium mercaptide microemulsion compared with N-dodecyl mercaptan and sodium xylyl dithiophosphate, respectively.

[0015] Figure 4 is a graph of the recovery from gold ore using sodium mercaptide together with potassium amyl xanthate as collectors compared to sodium xylyl dithiophosphate.

[0016] Specific embodiments of the present invention

[0017] The following definitions are provided to determine how terms used in this application, and in particular how the claims, are to be interpreted. The definitions are organized for convenience only and are not intended to limit any definition to any particular category.

[0018] "Collector" refers to a molecule or composition of matter containing molecules that selectively adheres to specific components of the ore and promotes the adhesion of the specific components to the microbubbles generated from the slurry injection.

[0019] "Pulverize" means to pulverize, crush, grind or otherwise make into fine solid particles.

[0020] "Concentrate" means the portion of the ore separated from the slurry by flotation and collected in the froth layer.

[0021] "Ore" refers to a composition of matter containing a mixture of more desirable materials (beneficiaries) and less desirable materials (gangue).

[0022] "Frothing agent" or "foaming agent" refers to a composition of matter that enhances the formation of microbubbles and / or preserves the formed microbubbles that contain a hydrophobic moiety generated by slurry spraying.

[0023] "Microemulsion" refers to a dispersion comprising a continuous phase material having substantially uniformly dispersed droplets of dispersed phase material, the droplets ranging in size from about 1 to 100 nm, typically from 10 to 50 nm.

[0024] "Slurry" means a mixture comprising a liquid medium in which the ore particles (finely divided solids) are dispersed or suspended, and when the slurry is sprayed, the tailings are retained in the slurry and at least some of the concentrate adheres to the spraying bubbles and rises from the slurry into a froth layer above the slurry. The liquid medium can be entirely water or partially an aqueous system.

[0025] In at least one embodiment, a froth flotation separation process is enhanced by adding a composition of the present invention to a slurry. The composition comprises a mercaptide collector, a solvent (e.g., water and / or another solvent), optionally one or more surfactants (optionally with one or more co-surfactants), and optionally a dispersant, the composition being in the form of a microemulsion.

[0026] The composition not only enhances the recovery of concentrate but also improves the selectivity of concentrate, increases the proportion of valuable materials in the concentrate, and reduces the proportion of gangue in the concentrate. Although effective in many forms of enrichment, the present invention is particularly effective for the flotation of sulfide minerals containing metals (e.g., Cu, Mo, Pb, Co, Zn, Ni, Au, Ag, Pt, Pd and / or Rh). The slurry treated with the mercaptide microemulsion of the present invention may include ores containing one or more articles selected from the group consisting of copper, gold, silver, iron, lead, nickel, cobalt, platinum, zinc, coal, barite, calamine, dolomite, feldspar, fluorite, heavy metal oxides, talc, potash, phosphate, iron, graphite, kaolin, bauxite, pyrite, mica, quartz, sulfide ores, composite sulfide ores, non-sulfide ores, silicon dioxide and any combination thereof.

[0027] Microemulsions are dispersions comprising a continuous phase material in which droplets of dispersed phase material are dispersed. The size of the droplets ranges from about 1 to about 100 nm, preferably from about 10 to about 50 nm. Due to the extremely small droplet size, microemulsions are optically transparent, isotropic, and thermodynamically stable. In at least one embodiment, the continuous phase material comprises water. In at least one embodiment, the dispersed phase material and / or the continuous phase material comprises one or more hydrophobic materials. In at least one embodiment, the dispersed phase material and / or the continuous phase material comprises amphiphilic and / or ionic materials.

[0028] Mercaptan [also known as thioalcohol (thiol)] can be in liquid form at standard ambient temperature and pressure, and it comprises a hydrocarbon chain consisting of eight to twelve carbon atoms. Such liquid mercaptans are immiscible with water. In addition, the volatility of these liquids is sufficient to cause concerns associated with toxic odors, which limits the use of these substances in many applications, particularly those applications carried out in open containers. In the present invention, liquid mercaptans are used, and the liquid mercaptans have been treated with (one or more) organic or inorganic strong bases to produce mercaptides (ionic salts of mercaptans). In one embodiment, mercaptides are produced as pure products, solid powders, and their compatibility with water is improved and there is no odor problem associated with the volatility of mercaptans used to form mercaptides microemulsions. Mercaptides microemulsions may include components such as water, alcohol, hydrocarbons, surfactants and / or dispersants.

[0029] The alcohol may be selected from the group consisting of ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, terpene alcohols, cresol acid, and any combination thereof, including isomers thereof.

[0030] The hydrocarbon may be selected from the group consisting of pentane, hexane, heptane, octane, decane, dodecane, propylene tetramer, kerosene, diesel, biodiesel (methylated fatty acids) and any combination thereof.

[0031] The surfactant may be selected from the group consisting of ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, poloxamers (e.g. Pluronic TM ), polysorbate and any combination thereof.

[0032] The dispersant may be selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol ethers and / or other polyols.

[0033] The thiolate is used in the form of a thiolate microemulsion. The thiolate derived from the thiol can also be provided as a solid after only reacting with a base. The solid thiolate can be used to prepare the thiolate microemulsion used in the present invention by mixing it with the components before use.

[0034] The study found that solids precipitated from the thiolate microemulsion liquid during a large number of operations. By performing different post-reaction treatments on repeated samples, it was found that the thiolate in the microemulsion can be oxidized to disulfide in the presence of oxygen. Therefore, for stability, it is necessary to minimize or avoid the oxidation of thiolate ions to disulfide.

[0035] Heavy mercaptans are mercaptans (-SH) having hydrocarbon chains of 4 to 18 carbon atoms, usually about 8 to 15 carbon atoms. The hydrocarbon chain may be linear, branched or cyclic. Mercaptans (which may include mercaptans, dithiolates or polythiolates) may be derived from mercaptans (molecules containing only one mercaptan group) or from dithiols or polythiols (each molecule containing two or more mercaptan groups). Primary, secondary or tertiary mercaptans having 8-15 carbon atoms may also be used. Exemplary dithiols and polythiols include 1,8-dithiol-3,6-dioxaoctane and pentaerythritol tetrakis (3-mercaptopropionate), respectively. When the pH of these molecules is greater than or equal to about 11, a conjugate base mercaptanate form is formed, converting the -SH group into an ion S-M+, where M+ is an organic or inorganic cation from a strong base. For example, alkali metal or alkaline earth metal hydroxide bases (e.g., sodium hydroxide, potassium hydroxide, rubidium hydroxide, magnesium hydroxide, calcium hydroxide, lithium hydroxide, barium hydroxide, and magnesium hydroxide), or organic bases such as ammonium hydroxide, tetramethylguanidine (forming a guanidine cation), guanidine, or tetramethylammonium hydroxide, when contacted with thiols, will form conjugated thiolates.

[0036] Heavy mercaptides are free-flowing solids, usually in pure form or with only minor amounts of mercaptides and / or reaction product impurities.

[0037] The microemulsion formulation may comprise a thiolate, water and optionally an alcohol, hydrocarbon, glycol, polyethylene glycol, surfactant and / or excess thiol from the thiolate conversion and a base.

[0038] Certain thiolate powders have a moderate affinity for water by themselves and do not require additional components to produce a homogeneous liquid product. For example, the thiolate salt of N-dodecyl mercaptan can form a homogeneous mixture in water at concentrations up to about 2% by weight (from 0.00001 to about 2% by weight). With the addition of the liquid component, the resulting microemulsion may contain up to 60% by weight of the thiolate salt. The preferred range is from about 0.01 to about 40% by weight of the thiolate salt. For multi-component microemulsions, the water content may range from about 20 to about 98.0% by weight (as a diluent for the pure thiolate powder), preferably from about 40 to about 98% by weight. About 2 to about 30% by weight of alcohol can be added. The preferred range of alcohol is about 5 to about 20% by weight. 0 to about 10% by weight of a surfactant can be added. 0 to about 20% by weight, more preferably 5 to 15% by weight of a dispersant can be added. The formation of the thiolate salt can be achieved by reacting the thiol with an equimolar amount of a base, but an excess of up to about 1 to about 5% by weight of the base can also be used.

[0039] In froth flotation applications, mercaptide compositions (including powdered forms or microemulsions) can be used together with frothers and other collectors that contribute to the ability and selectivity of mercaptide collectors. Examples of useful frothers in the present invention include any of those known in the art, including but not limited to C5-C8 alcohols, pine oil, cresols, C1-C4 alkyl ethers of polypropylene glycol, dihydroxy compounds of polypropylene glycol, glycols, fatty acids, soaps, alkylaryl sulfonates and combinations thereof. Other collectors that can be used in combination with the mercaptide microemulsion of the present invention can include, for example, those collectors based on xanthates, dithiophosphates, monothiophosphates, mercaptobenzothiazoles, dithiocarbamates, trithiocarbonates, thiocarbamates, thioureas, guanidines or combinations thereof.

[0040] Other Implementations

[0041] Additionally or alternatively, the present invention may include one, some or all of the following embodiments.

[0042] Embodiment 1. A method for enhancing the performance of a collector in froth flotation separation of ore in a medium, the method comprising the following steps: forming a slurry by blending a collector microemulsion, ore in a medium, and optionally other additives, and removing concentrate from the ore by spraying the slurry; wherein the collector microemulsion comprises a continuous phase and a dispersed phase, the continuous phase is an aqueous carrier fluid, and the dispersed phase comprises a thiolate.

[0043] Embodiment 2. The method of embodiment 1, wherein the continuous phase is water.

[0044] Embodiment 3. The method of embodiment 1 or embodiment 2, wherein the thiol is selected from the group consisting of monothiol, dithiol, polythiol, and any combination thereof.

[0045] Embodiment 4. A method as described in any of the preceding embodiments, wherein the thiolate is selected from the group consisting of linear, branched or cyclic C8 to C15 primary thiolates, linear, branched or cyclic C8 to C15 secondary thiolates, linear, branched or cyclic C8 to C15 tertiary thiolates and any combination thereof.

[0046] Embodiment 5. The method according to any one of the preceding embodiments, wherein the microemulsion further comprises at least one item selected from the group consisting of a surfactant, an alcohol, a hydrocarbon, a dispersant, and any combination thereof.

[0047] Embodiment 6. A method as described in any of the preceding embodiments, wherein the slurry contains an ore containing one or more items selected from the following group: copper, gold, silver, iron, lead, nickel, cobalt, platinum, zinc, coal, barite, calamine, dolomite, feldspar, fluorite, heavy metal oxides, talc, potash, phosphate, iron, graphite, kaolin, bauxite, pyrite, mica, quartz, sulfide ores, complex sulfide ores, non-sulfide ores, silica, and any combination thereof.

[0048] Embodiment 7. The method of any one of the preceding embodiments, wherein the microemulsion further comprises a surfactant and at least one co-surfactant.

[0049] Embodiment 8. The method as described in any one of embodiments 5-7, wherein the surfactant and / or co-surfactant is selected from the following group: ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, poloxamers, polysorbates and any combination thereof.

[0050] Embodiment 9. The method as described in any one of embodiments 5-8, wherein the alcohol is selected from the group consisting of ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, terpene alcohol, cresol acid, and any isomers and combinations thereof.

[0051] Embodiment 10. The method as described in any one of embodiments 5-8, wherein the hydrocarbon is selected from the following group: pentane, hexane, heptane, octane, decane, dodecane, propylene tetramer, kerosene, diesel, biodiesel (methylated fatty acids) and any combination thereof.

[0052] Embodiment 11. The method of any one of embodiments 5-8, wherein the dispersant is selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol ethers, polyols, and any combination thereof.

[0053] Embodiment 12. A method as described in any of the preceding embodiments, wherein forming the slurry further comprises blending a foaming agent selected from the group consisting of C5-C8 alcohols, pine oil, cresol, C1-C4 alkyl ethers of polypropylene glycol, dihydroxylated polypropylene glycol, glycols, fatty acids, soaps, alkyl aryl sulfonates, and combinations thereof.

[0054] Embodiment 13. A method as described in any of the preceding embodiments, wherein forming the slurry further comprises blending a collector selected from the group consisting of xanthates, dithiophosphates, monothiophosphates, mercaptobenzothiazoles, dithiocarbamates, trithiocarbonates, thiocarbamates, thioureas, guanidines, and combinations thereof.

[0055] Example 1

[0056] The use of mercaptide microemulsions as collectors for froth flotation was evaluated by flotation of 2 g of pure mineral in approximately 200 ml Hallimond tubes. A dose of approximately 5 microliters of mercaptide microemulsion was added over a pH range of approximately 4 to 12. Flotation was performed for approximately 5 minutes at each pH using a nitrogen flow rate of approximately 40 ml / min. Both chalcopyrite (CuFeS2) and pyrite (FeS2) were successfully floated, although chalcopyrite was more selective than the less valuable pyrite at pH values ​​above 10. The results are summarized in Figure 1 .

[0057] Example 2

[0058] Another example of the application of mercaptide microemulsions as collectors was evaluated in the crude flotation of a Cu-Mo ore. The results are summarized in Figure 2 and 3 . In this test, about 500 grams of ore was added to about 2.5L Denver flotation cell, and collector, frother were added and maintained for about 2 minutes at pH of about 10. The collection time using air as the frother medium was about 5 minutes. In this test, a mercaptan microemulsion (ME) with a dosage of about 120g / ton (active ingredient sodium dodecyl mercaptan about 24g / ton) was compared with N-dodecyl mercaptan (NDM) and sodium ditolyl dithiophosphate (DTP) with a dosage of about 54g / ton. Although the Cu recovery achieved by ME was relatively low, it was unexpectedly high at about 85% considering that the active ingredient was less than half of the other collectors. In addition, the Cu grade in the concentrate was about 14%, similar to NDM but slightly higher than DTP's about 12%. Compared with NDM and DTP, the recovery and grade of Mo were improved. In this case, ME achieved a Mo recovery of about 48% and a grade of about 0.43%.

[0059] Example 3

[0060] Similar to Example 2, a mercaptide microemulsion (ME) was compared to sodium ditoluene dithiophosphate (DTP) as collectors for Au ore. The flotation parameters were identical except that the collection time was approximately 10 minutes. The dosage of potassium amyl xanthate (PAX) was approximately 24 g / ton in both cases, except for the ME and DTP dosages of approximately 48 g / ton. It is noteworthy that the total amount of active ingredients in the ME (sodium dodecyl mercaptide) was approximately 10 g / ton. The overall Au recovery using both collectors was approximately 98%, again demonstrating the effectiveness of the present invention in precious and base metal processing. A graphical comparison of Example 3 is shown in FIG. Figure 4 .

Claims

1. A method for enhancing the performance of a collector in froth flotation separation of an ore in a medium, the method comprising the following steps: A slurry is formed by blending the collector microemulsion, the ore in the medium, and optionally other additives, and removing concentrate from the ore by spraying said slurry; The collector microemulsion comprises a continuous phase and a dispersed phase, wherein the continuous phase is an aqueous carrier fluid, and the dispersed phase comprises mercaptan salt.

2. The method of claim 1, wherein the continuous phase is water.

3. The method of claim 1, wherein the thiol is selected from the group consisting of monothiol, dithiol, polythiol, and any combination thereof.

4. The method of claim 1, wherein the thiolate is selected from the group consisting of a linear, branched or cyclic C8 to C15 primary thiolate, a linear, branched or cyclic C8 to C15 secondary thiolate, a linear, branched or cyclic C8 to C15 tertiary thiolate, and any combination thereof.

5. The method of claim 1, wherein the microemulsion further comprises at least one item selected from the group consisting of a surfactant, an alcohol, a hydrocarbon, a dispersant, and any combination thereof.

6. The method of claim 1, wherein the slurry comprises an ore containing one or more items selected from the group consisting of copper, gold, silver, iron, lead, nickel, cobalt, platinum, zinc, coal, barite, calamine, dolomite, feldspar, fluorite, heavy metal oxides, talc, potash, phosphate, iron, graphite, kaolin, bauxite, pyrite, mica, quartz, sulfide ores, complex sulfide ores, non-sulfide ores, silica, and any combination thereof.

7. The method of claim 1, wherein the microemulsion further comprises a surfactant and at least one co-emulsifier.

8. The method of claim 5, wherein the surfactant is selected from the group consisting of ethoxylated mercaptans, alkylphenol ethoxylates, alkylbenzene sulfonates, poloxamers, polysorbates, and any combination thereof.

9. The method of claim 5, wherein the alcohol is selected from the group consisting of ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, terpene alcohols, cresol acid, and any isomers and combinations thereof.

10. The method of claim 5, wherein the hydrocarbon is selected from the group consisting of pentane, hexane, heptane, octane, decane, dodecane, propylene tetramer, kerosene, diesel, biodiesel (methylated fatty acids), and any combination thereof.

11. The method of claim 5, wherein the dispersant is selected from the group consisting of polyethylene glycol, polypropylene glycol, polyethylene glycol ether, polyol, and any combination thereof.

12. The method of claim 1, wherein forming the slurry further comprises blending a foaming agent selected from the group consisting of C5-C8 alcohols, pine oil, cresol, C1-C4 alkyl ethers of polypropylene glycol, dihydroxylated polypropylene glycol, glycols, fatty acids, soaps, alkylaryl sulfonates, and combinations thereof.

13. The method of claim 1, wherein forming the slurry further comprises blending a collector selected from the group consisting of xanthates, dithiophosphates, monothiophosphates, mercaptobenzothiazoles, dithiocarbamates, trithiocarbonates, thiocarbamates, thioureas, guanidines, and combinations thereof.

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