Solid-liquid extractant for platinum group metals

Abstract

The present invention addresses the problem of providing a solid-liquid extraction agent for efficiently extracting PGMs directly from a solid article or a solid composition containing PGMs, such as an automotive catalyst, without using a high-concentration inorganic acid, and an extraction method using the extraction agent. The present invention relates to: a solid-liquid extraction agent for a platinum group metal containing (a) a hydrophobic deep eutectic solvent; and a solid-liquid extraction method for a platinum group metal using the extraction agent.

Description

Technical Field

[0001] The present invention relates to a solid-liquid extractant for platinum group metals and a solid-liquid extraction method for platinum group metals. Background Art

[0002] Platinum Group Metals (PGMs) are limited in resources and unevenly distributed in production areas. Therefore, there is an increasing need to recover PGMs from secondary resources such as autocatalysts. Autocatalysts are devices that purify automobile exhaust and contain PGMs such as platinum (Pt), palladium (Pd), and rhodium (Rh) (Non-Patent Document 1). Furthermore, since natural ores contain only 0.005g of PGMs per kg, autocatalysts can be enriched with up to 5g of PGMs per kg. Therefore, autocatalysts can be considered a highly valuable resource with a quality 1,000 times higher than that of ores.

[0003] As a means of recovery of PGMs, a wet smelting method was used in the past. In the wet smelting method, the metal contained in the automobile catalyst is dissolved in the aqueous phase from the solid phase by a high concentration of inorganic acid, and then the target metal is separated and recovered one by one by means of processes such as organic solvent extraction. Although this method can obtain highly purified PGMs, a large amount of acid waste water containing heavy metals and / or the highly volatile organic solvent used during solvent extraction will bring significant environmental load (non-patent literature 2). In addition, the recycling difficulty of the extraction agent is also relatively large. Considering such background, there is an urgent need for a recovery method of the novel PGMs that does not discharge a large amount of acid waste liquid and does not use a volatile organic solvent.

[0004] Methods using ionic liquids have been reported as leaching methods for PGMs that do not require the use of high-concentration inorganic acids (Non-Patent Documents 3 and 4). Furthermore, in recent years, there have been reports of recovering PGMs from spent automotive catalysts using a deep eutectic solvent containing choline chloride and an inorganic oxidant such as nitric acid or hydrogen peroxide (Non-Patent Document 5), and extracting PGMs from a hydrochloric acid solution containing PGMs using a deep eutectic solvent composed of a quaternary ammonium salt and a carboxylic acid (Non-Patent Document 6).

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-patent literature 1: Sun S, et al., Journal of Environmental Management (2022), 305;

[0008] Non-patent literature 2: Karim S, et al., Resources, Conservation and Recycling, (2021), 170;

[0009] Non-patent literature 3: Binnemans et al., Green Chem., 2018, 20, 3327-3338;

[0010] Non-patent literature 4: Binnemans et al., RSC Adv., 2021, 11, 10110-10120;

[0011] Non-patent literature 5: Bica-Schroder., Green Chemistry Letters and Reviews, Vol. 15, 2022(2), 405-415;

[0012] Non-patent literature 6: O. Mokhodoeva et al, Separation and Purification Technology 305 (2023) 122427. SUMMARY

[0013] PROBLEMS TO BE SOLVED BY THE INVENTION

[0014] However, the above-mentioned PGMs leaching method using ionic liquids has limitations, and it is necessary to pass chlorine, bromine, iodine, and the like into various ionic liquids to dissolve them to prepare a leaching solvent. Although Pd can be dissolved, Pt and the like are difficult to dissolve, resulting in insufficient leaching of PGMs. In addition, the technology in Non-patent literature 5, which combines a deep eutectic solvent containing choline chloride with an inorganic oxidizing agent, not only has a low extraction efficiency of PGMs, but also has a significant deficiency in the extraction efficiency of Rh, and co-extraction of metals other than PGMs. In addition, the technology of Non-patent literature 6 can only extract a deep eutectic solvent from PGMs that are previously dissolved in an aqueous hydrochloric acid solution, and is not a technology for directly extracting from a solid containing PGMs.

[0015] Therefore, the object of the present application is to provide a solid-liquid extraction agent and an extraction method using the same, which can directly and efficiently extract PGMs from a solid article or a solid composition containing PGMs such as an automobile catalyst, without using a high concentration of inorganic acid.

[0016] MEANS FOR SOLVING THE PROBLEMS

[0017] Thus, the present application is directed to the selective extraction effect of various deep eutectic solvents on platinum group metals (PGMs), and it is found that if a hydrophilic hydrogen bond acceptor such as choline chloride is not used, but a hydrophobic hydrogen bond acceptor and a hydrophobic hydrogen bond donor composed of a hydrophobic group represented by a long-chain alkyl group are used, PGMs can be directly and selectively extracted from solid articles or solid compositions containing PGMs such as automobile catalysts with high efficiency, and if an organic acid having 1 to 4 carbon atoms and / or a halogenating agent is added to the hydrophobic deep eutectic solvent, the extraction efficiency and selectivity of the PGMs can be significantly improved, thereby completing the present application.

[0018] That is, the present application provides the following inventions [1] to

[13] .

[0019] [1] A solid-liquid extraction agent for platinum group metals containing (a) a hydrophobic deep eutectic solvent.

[0020] [2] The solid-liquid extraction agent for platinum group metals according to [1], wherein (a) the hydrophobic deep eutectic solvent is a mixture of a hydrogen bond acceptor having a hydrophobic group and a hydrogen bond donor having a hydrophobic group.

[0021] [3] The solid-liquid extraction agent for platinum group metals according to [1] or [2], wherein the hydrogen bond acceptor having a hydrophobic group is a compound selected from the group consisting of a phosphonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an ammonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a sulfonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an imidazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyrazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyridinium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, and a pyrrolidinium compound having at least one hydrocarbon group having 6 to 30 carbon atoms.

[0022] [4] The solid-liquid extraction agent for platinum group metals according to [3], wherein the hydrogen bond donor having a hydrophobic group is a compound selected from the group consisting of an organic acid having a hydrocarbon group having 6 to 30 carbon atoms and an alcohol having a hydrocarbon group having 6 to 30 carbon atoms.

[0023] [5] The solid-liquid extraction agent for platinum group metals according to any one of [1] to [4], further containing one or more selected from the group consisting of (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent.

[0024] [6] The solid-liquid extraction agent for platinum group metals according to [5], containing (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent.

[0025] [7] The solid-liquid extractant for platinum group metals according to [5] or [6], wherein (b) the organic acid having 1 to 4 carbon atoms is one or more selected from formic acid, fatty acids having 2 to 4 carbon atoms, and alkanesulfonic acids having 1 to 4 carbon atoms.

[0026] [8] The solid-liquid extractant for platinum group metals according to any one of [5] to [7], wherein the halogenating agent (c) is one or more selected from trihalogenated cyanuric acid, N-halogenated dicarboxylic acid imide compound, N,N-dihalogenated sulfonamide compound, thionyl halide, sulfuryl halide, phosphorus halide, acyl halide, dihalogenated cyanuric acid, monohalogenated cyanuric acid, trihalogenated isocyanuric acid, dihalogenated isocyanuric acid, monohalogenated isocyanuric acid and halosilane compound.

[0027] [9] The solid-liquid extractant for platinum group metals according to any one of [5] to [8], wherein the amount of (b) the organic acid having 1 to 4 carbon atoms added is 5.0% by mass or more relative to the solid-liquid extractant for platinum group metals.

[0028]

[10] The solid-liquid extractant for platinum group metals according to any one of [5] to [9], wherein the amount of the halogenating agent (c) added is 1.0 mass % or more relative to the solid-liquid extractant for platinum group metals.

[0029]

[11] The solid-liquid extractant for platinum group metals according to [1], further comprising (d) a non-polar organic solvent.

[0030]

[12] A method for solid-liquid extraction of platinum group metals, characterized in that a solid-liquid extractant for platinum group metals as described in any one of [1] to

[11] is added to a pulverized solid object or solid composition containing a platinum group metal compound and other metal compounds, so that the platinum group metals are leached in the extractant.

[0031]

[13] A method for recovering platinum group metals, comprising the following steps: adding a solid-liquid extractant for platinum group metals as described in any one of [1] to

[11] to a pulverized solid object or solid composition containing a platinum group metal compound and other metal compounds, thereby leaching the platinum group metals in the extractant; and extracting each platinum group metal from the leachate obtained.

[0032] Effects of the Invention

[0033] The solid-liquid extractant for PGMs of the present invention enables direct and efficient extraction of PGMs from solid articles or solid compositions containing PGMs, such as automotive catalysts, without the use of high-concentration inorganic acids. In particular, the use of a solid-liquid extractant for PGMs comprising (a) a hydrophobic deep eutectic solvent, (b) an organic acid having 1 to 4 carbon atoms, and (c) a halogenating agent enables direct, selective, and efficient extraction of PGMs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 : It is a schematic diagram showing the crushing state of automobile catalyst.

[0035] Figure 2 : is a schematic diagram showing the results of extraction from Pt powder using a solid-liquid extractant (0.5 g / L) of TCCA (5.3 mass %) and / or MSA (13.8 mass %) added to hydrophobic DES (P6Cl / decA=1 / 2) (80°C, 400 rpm, 24 h).

[0036] Figure 3 : Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from crushed automobile catalyst using a solid-liquid extractant (50 g / L) prepared by adding TCCA (5.3 mass % or 0 mass %) and / or MSA (13.8 mass % or 0 mass %) to hydrophobic DES (P6Cl / decA = 1 / 2).

[0037] Figure 4 : is a schematic diagram showing the comparison of the results of extracting PGMs from automobile catalysts by the conventional method [5M HCl+5% H2O2] and the method of the present invention [a solid-liquid extractant (50 g / L) containing TCCA (5.3 mass %) and / or MSA (13.8 mass %) added to hydrophobic DES (P6Cl / decA=1 / 2)].

[0038] Figure 5 : Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from crushed automobile catalyst using a solid-liquid extractant (50 g / L) comprising TCCA (0% to 10.1% by mass) and MSA (2.9% to 26.7% by mass) added to hydrophobic DES (P6Cl / decA = 1 / 2).

[0039] Figure 6: Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from crushed automobile catalyst using a solid-liquid extractant (50 g / L) containing various chlorinating agents (1.4 mass % of TCCA, N-chlorophthalimide (NCl), or dichloramine B (GB)) and MSA (7.1 mass %) added to hydrophobic DES (P6Cl / decA = 1 / 2).

[0040] Figure 7 : Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from crushed automobile catalyst using a solid-liquid extractant (50 g / L) prepared by adding TCCA (1.4 mass %) and 7.1 mass % of various fatty acids (MSA or formic acid) to hydrophobic DES (P6Cl / decA=1 / 2).

[0041] Figure 8 : Schematic diagram showing the extraction results (80°C, 400 rpm, 24 h) from automobile catalyst crushed material using hydrophobic DES with varying P6Cl / decA ratios and the addition of a solid-liquid extractant (50 g / L) containing TCCA (1.4 mass %) and MSA (7.1 mass %).

[0042] Figure 9 : Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from automobile catalyst crushed material using a DES with a modified hydrogen bond donor of the hydrophobic DES using a solid-liquid extractant (50 g / L) containing TCCA (1.4 mass %) and MSA (7.1 mass %) added to the DES (octanoic acid (C8), capric acid (C10), lauric acid (C12), and decanol (C10(OH)) with a modified hydrogen bond donor of the hydrophobic DES).

[0043] Figure 10 : Schematic diagram showing the results of extraction (80°C, 400 rpm, 24 h) from crushed automobile catalyst using a solid-liquid extractant (50 g / L) prepared by adding TCCA (1.4 mass %) and MSA (7.1 mass %) to hydrophobic DES (P6Cl / decA = 1 / 2) and adding 2 mass parts of an organic solvent (toluene or dodecane) to 1 mass part of DES.

[0044] Figure 11 : Schematic diagram of the process for recovering platinum group metals (PGMs) from the automotive catalyst leachate obtained by the method of the present invention.

[0045] Figure 12 : It is a schematic diagram showing the recovery rate of Al and La in the aqueous phase from the automobile catalyst leachate.

[0046] Figure 13 : is a graph showing the recovery rate of Rh in 5M NH4Cl aqueous solution phase from the leach liquor after removal of Al and La from the leach liquor of the automobile catalyst.

[0047] Figure 14 : is a graph showing the recovery rate of Pd in 0.005M thiourea aqueous solution phase from the leach liquor after removal of Al, La and Rh from the leach liquor of the automobile catalyst.

[0048] Figure 15 : is a graph showing the recovery rate of Pd in 10M NH4NO3 aqueous solution phase from the leach liquor after removal of Al, La, Rh and Pd from the leach liquor of the automobile catalyst. DETAILED DESCRIPTION

[0049] One form of the present application is a solid-liquid extraction agent for PGMs containing (a) a hydrophobic deep eutectic solvent.

[0050] Here, the so-called deep eutectic solvent refers to a solvent having a lower melting point and being liquid at 25°C by mixing two or more compounds. Specifically, it is a mixture of a hydrogen bond acceptor and a hydrogen bond donor, and a solvent that becomes liquid at 25°C.

[0051] The deep eutectic solvent used in the present application is preferably a hydrophobic deep eutectic solvent as described above. The hydrophobic deep eutectic solvent can be any deep eutectic solvent that does not mix with water, but it is preferably a deep eutectic solvent having a solubility of 1 g / 100 mL or less in water at 25°C, more preferably a deep eutectic solvent having a solubility of 0.1 g / 100 mL or less, and particularly preferably a deep eutectic solvent having a solubility of 0.01 g / 100 mL or less.

[0052] The hydrophobic deep eutectic solvent is preferably a mixture of a hydrogen bond acceptor having a hydrophobic group and a hydrogen bond donor having a hydrophobic group.

[0053] The hydrogen bond acceptor may be a phosphonium compound (quaternary phosphonium salt), an ammonium compound (quaternary ammonium salt), a sulfonium compound (tertiary sulfonium salt), an imidazolium compound, a pyrazolium compound, a pyridinium compound, a pyrrolium compound, or the like. Furthermore, the hydrophobic group is preferably a hydrocarbon group having 6 to 30 carbon atoms. That is, the hydrogen bond acceptor having a hydrophobic group is preferably a compound selected from the group consisting of a phosphonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an ammonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a sulfonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an imidazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyrazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyridinium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, and a pyrrolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms. Here, the number of the hydrocarbon groups having 6 to 30 carbon atoms is preferably 1 to 4.

[0054] The hydrocarbon group having 6 to 30 carbon atoms may be an aliphatic hydrocarbon group having 6 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 30 carbon atoms. The aliphatic hydrocarbon group having 6 to 30 carbon atoms may be a chain hydrocarbon group having 6 to 30 carbon atoms or an alicyclic hydrocarbon group having 6 to 30 carbon atoms. Specifically, it may be a linear or branched alkyl group having 6 to 30 carbon atoms, a linear or branched alkenyl group having 6 to 30 carbon atoms, a linear or branched alkynyl group having 6 to 30 carbon atoms, a cycloalkyl group having 6 to 30 carbon atoms, or a cycloalkenyl group having 6 to 30 carbon atoms. These hydrocarbon groups preferably have 6 to 30 carbon atoms, more preferably 6 to 24 carbon atoms, and even more preferably 6 to 22 carbon atoms from the perspective of availability.

[0055] More preferably, the hydrogen bond acceptor of the hydrophobic group can be a phosphonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an ammonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a sulfonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, or an imidazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms.

[0056] The hydrogen bond acceptor having a hydrophobic group can be tributyl (tetradecyl) phosphonium salt, triethyl (octyl) phosphonium salt, tetraethylpentyl phosphonium salt, trihexyl (tetradecyl) phosphonium salt, tetraphenyl phosphonium salt, hexadecyltrimethylammonium salt, tetraoctylammonium salt, 1-octyl-3-methylimidazolium salt, etc.

[0057] Furthermore, the anions constituting the counter ions of these cationic moieties may be halogen ions or the like.

[0058] The hydrogen bond donor may be a compound selected from an organic acid having a hydrocarbon group with 6 to 30 carbon atoms and an alcohol having a hydrocarbon group with 6 to 30 carbon atoms. Here, the organic acid may be a carboxylic acid, a sulfonic acid, or a phenol.

[0059] The hydrocarbon group having 6 to 30 carbon atoms may be an aliphatic hydrocarbon group having 6 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 30 carbon atoms. The aliphatic hydrocarbon group having 6 to 30 carbon atoms may be a chain hydrocarbon group having 6 to 30 carbon atoms or an alicyclic hydrocarbon group having 6 to 30 carbon atoms. Specifically, it may be a linear or branched alkyl group having 6 to 30 carbon atoms, a linear or branched alkenyl group having 6 to 30 carbon atoms, a linear or branched alkynyl group having 6 to 30 carbon atoms, a cycloalkyl group having 6 to 30 carbon atoms, or a cycloalkenyl group having 6 to 30 carbon atoms. These hydrocarbon groups preferably have 6 to 30 carbon atoms, more preferably 6 to 24 carbon atoms, and even more preferably 6 to 22 carbon atoms from the perspective of availability.

[0060] The hydrogen bond donor having a hydrophobic group may be a fatty acid having 6 to 30 carbon atoms, an aromatic carboxylic acid having 6 to 30 carbon atoms, an aliphatic sulfonic acid having 6 to 30 carbon atoms, an aromatic sulfonic acid having 6 to 30 carbon atoms, a phenol having 6 to 30 carbon atoms, or an alcohol having 6 to 30 carbon atoms. More preferably, the hydrogen bond donor may be a fatty acid having 6 to 24 carbon atoms, an aromatic carboxylic acid having 6 to 24 carbon atoms, an aliphatic sulfonic acid having 6 to 24 carbon atoms, an aromatic sulfonic acid having 6 to 24 carbon atoms, or a phenol having 6 to 24 carbon atoms.

[0061] The mixing ratio of the hydrogen bond acceptor (A) and the hydrogen bond donor (B) in the hydrophobic deep eutectic solvent is not particularly limited as long as it becomes a liquid at 25°C. However, from the perspective of the solid-liquid extraction efficiency of PGMs, the molar ratio ((A) / (B)) is preferably 0.2 to 1, more preferably 0.2 to 0.75, and even more preferably 0.25 to 0.5.

[0062] From the perspective of the solid-liquid extraction efficiency and selectivity of PGMs, the solid-liquid extractant of PGMs of the present invention preferably contains, in addition to the hydrophobic deep eutectic solvent, one or more selected from (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent, and further preferably contains (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent.

[0063] The (b) organic acid having 1 to 4 carbon atoms may be one or more selected from the group consisting of formic acid, fatty acids having 2 to 4 carbon atoms, and alkanesulfonic acids having 1 to 4 carbon atoms. Specifically, it may be formic acid, oxalic acid, acetic acid, propionic acid, butyric acid, methanesulfonic acid, ethanesulfonic acid, and the like.

[0064] From the perspective of solid-liquid extraction efficiency and selectivity of PGMs, the amount of (b) the organic acid having 1 to 4 carbon atoms added is preferably 5.0% by mass or greater, more preferably 6.0% by mass or greater, relative to the solid-liquid extractant. The upper limit of the amount added is preferably 30% by mass or less.

[0065] The (c) halogenating agent may be one or more selected from trihalogenated cyanuric acid, N-halogenated dicarboxylic acid imide compounds, N,N-dihalogenated sulfonamide compounds, thionyl halides, sulfuryl halides, phosphorus halides, acyl halides, dihalogenated cyanuric acid, monohalogenated cyanuric acid, trihalogenated isocyanuric acid, dihalogenated isocyanuric acid, monohalogenated isocyanuric acid and halogenated silane compounds.

[0066] Here, the halogen atom may be a chlorine atom, an iodine atom, or the like.

[0067] Specifically, it may be trihalogenated cyanuric acid, N-halogenated phthalimide, N-halogenated succinimide, N,N-dihalogenated benzenesulfonamide, N,N-dihalogenated p-toluenesulfonamide, etc. More specifically, it may be trichlorocyanuric acid, N-chlorophthalimide, N-chlorosuccinimide, N,N-dichlorobenzenesulfonamide (dichloroamine B), N,N-dichloro-p-toluenesulfonamide, etc.

[0068] From the perspective of solid-liquid extraction efficiency and selectivity of PGMs, the amount of the halogenating agent (c) added is preferably 1.0% by mass or more, more preferably 1.2% by mass or more, relative to the solid-liquid extraction agent. The upper limit of the content is preferably 10% by mass or less.

[0069] The solid-liquid extractant of PGMs of the present invention may contain, in addition to the above components, a non-polar organic solvent that does not react with the above components.

[0070] The non-polar organic solvent may be an aromatic hydrocarbon solvent or an aliphatic hydrocarbon solvent. Aromatic hydrocarbon solvents may be benzene, toluene, xylene, etc. Aliphatic hydrocarbon solvents may be hexane, octane, decane, dodecane, cyclopentane, cyclohexane, etc.

[0071] These non-polar organic solvents are not particularly limited, and may be contained in an amount of 0.2 to 10 parts by mass relative to 1 part by mass of the hydrophobic deep eutectic solvent.

[0072] The solid-liquid extractant of the present invention is intended to extract PGMs. Specifically, the solid-liquid extractant of the present invention can selectively and efficiently extract PGMs directly from solid objects or solid compositions containing platinum group metal compounds and other metal compounds.

[0073] The PGMs can be Pt, Pd, Rh, Ru, Ir, or Os. The solid-liquid extractant of the present invention is preferably used for the solid-liquid extraction of Pt, Pd, Rh, Ru, and Ir, and more preferably for the solid-liquid extraction of Pt, Pd, Rh, and Ir.

[0074] Solid-liquid extraction refers to the extraction of a target component from a solid. Meanwhile, PGMs, the target of extraction, are contained in solids such as the aforementioned automotive catalysts. Autocatalysts, in addition to the target PGMs, also contain a large amount of metals such as Al, Mg, La, and Fe. Therefore, efficient solid-liquid extraction of PGMs directly from these solids is highly desirable. The solid-liquid extractant of the present invention enables the selective and efficient extraction of PGMs directly from pulverized solid articles or solid compositions containing platinum group metal compounds and other metal compounds.

[0075] That is, another embodiment of the present invention is a method for solid-liquid extraction of PGMs, characterized in that a solid-liquid extractant for PGMs is added to a pulverized solid object or solid composition containing a platinum group metal compound and other metal compounds, thereby leaching the PGMs into the extractant.

[0076] PGMs are widely used as catalysts for hydrogenation reactions, as catalysts for purifying automobile exhaust (autocatalysts), in petroleum refining, as catalysts for producing nitric acid by ammonia oxidation, in electrical / electronic components (capacitor materials), and as heat-resistant / wear-resistant materials. Furthermore, these materials and / or components contain large amounts of other metals. For example, autocatalysts contain large amounts of metals such as Al, Mg, La, and Fe. Therefore, the solid article or solid composition containing a platinum group metal compound and other metal compounds used in the solid-liquid extraction method of the present invention can be the catalyst, electrical / electronic component, heat-resistant / wear-resistant material, etc. containing PGMs.

[0077] In consideration of extraction efficiency, the solid object or solid composition is pulverized for solid-liquid extraction. The particle size of the pulverized product varies depending on the form of the material, but is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less.

[0078] The amount of the solid-liquid extractant added to the pulverized product of the solid object or solid composition varies depending on the particle size of the pulverized product, the form of the material, etc., and is preferably 100 parts by mass or less per 1 part by mass of the pulverized product, more preferably 21 to 99 parts by mass, and even more preferably 5 to 20 parts by mass.

[0079] The leaching step is preferably performed at 40°C or higher for 3 hours or more, more preferably at 50°C or higher for 6 hours or more, and further preferably at 60°C or higher for 12 hours or more, from the viewpoint of leaching efficiency. In addition, the upper limit of the temperature is preferably 100°C or lower, and the time is preferably 48 hours or less. In addition, stirring is preferably performed in the leaching step.

[0080] The PGMs are extracted from the solid article or solid composition into the solid-liquid extractant with high efficiency and selectivity by the leaching step.

[0081] The PGMs are contained in the solid-liquid extractant by the leaching step. Therefore, if each of the PGMs is extracted from the obtained leachate, respectively, each of the PGMs can be recovered.

[0082] That is, another form of the present application is a recovery method of PGMs, the method including the following steps: a step of adding a solid-liquid extractant of the PGMs to a pulverized product of a solid article or solid composition containing a platinum group metal compound and other metal compounds other than the platinum group metal compound, and leaching the PGMs in the extractant, and a step of extracting each of the PGMs from the obtained leachate, respectively.

[0083] Here, the leaching step can be performed as described above.

[0084] The method of extracting each of the PGMs from the obtained leachate is a liquid-liquid extraction step of PGMs from an organic solvent phase to an aqueous phase, and a known method can be used. For example, the method described in Firmansyah, M. L., Kubota, F., & Goto, M. (2018). Extraction of Pt(IV), Pd(II), and Rh(III) using ionic liquid trioctyl(dodecyl)phosphonium chloride solvent. Journal of Chemical Technology and Biotechnology, 93(6), 1714-1721. https: / / doi.org / 10.1002 / jctb.5544, and Firmansyah, M. L., Kubota, F., Yoshida, W., & Goto, M. (2019). Application of a novel phosphonium-based ionic liquid to separation of platinum group metals in automobile catalyst leachate. Industrial & Engineering Chemistry Research, 58(9), 3845-3852. https: / / doi.org / 10.1021 / acs.iecr.8b05848 can be used.

[0085] For example, the recovery of Rh can be performed by bringing an aqueous ammonium chloride solution or the like into contact with the organic solvent phase. In addition, the recovery of Pd can be performed by bringing an aqueous thiourea solution or the like into contact with the organic solvent phase. In addition, the recovery of Pt can be performed by bringing an aqueous ammonium nitrate solution or the like into contact with the organic solvent phase.

[0086] Furthermore, when the leachate contains metals other than PGMs, these metals can also be removed by known methods. For example, La, Al, etc. can be easily removed simply by bringing the leachate into contact with water.

[0087] Example

[0088] Next, the present invention will be described in further detail with reference to Examples, but the present invention is not limited to these Examples.

[0089] Example 1 (Leaching of Metal Powder or Automobile Catalyst)

[0090] Non-Patent Document 1 reports that Au powder can be leached in an acetone solution containing a quaternary ammonium salt containing trichloroisocyanuric acid (TCCA). Furthermore, methanesulfonic acid (MSA) is reported to be an environmentally friendly acid due to its low volatility and biodegradability. To dissolve PGMs, which are very stable and difficult to dissolve, TCCA and MSA were added to a hydrophobic deep eutectic solvent (hydrophobic DES) to verify their leaching performance. At this time, the leaching targets were single metal powder and powder from used automotive catalysts.

[0091] (1) Experimental operation

[0092] (DES Production)

[0093] Trihexyl(tetradecyl)phosphonium chloride (P66614C:P6Cl), a hydrogen bond acceptor, and decanoic acid, a hydrogen bond donor, were weighed in a 1:2 molar ratio. The mixture was heated and stirred at 80°C and 400 rpm for 1 or 2 hours to dehydrate the mixture and prepare a hydrophobic DES.

[0094] (Analysis of Automotive Catalysts)

[0095] Crushed automobile catalysts ( Figure 1 ), after reduction treatment with formic acid, the crushed catalyst and aqua regia were added to a two-necked flask and heated and stirred at 80°C for 24 hours at 500 rpm to completely dissolve the PGMs. After the reaction, the mixture was filtered with filter paper to produce a small amount of residue. The recovered solution was diluted 40-fold and the metal concentration was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES, Optima 8300, Parkin-Elmer).

[0096] (Leaching of automotive catalysts or metal powders)

[0097] The metal powder or the crushed catalyst was mixed with the solvent, and after the solution was stirred by vortex for 1 minute, heating and stirring were performed at 80°C for 24 hours under 400 rpm in a closed system. After the heating and stirring, the separation of the residue and the DES phase was performed by centrifugation (20,000 G, 10 min, 35°C). After the recovered solution was diluted 20 times, the concentration of the metal was measured by an inductively coupled plasma emission spectrometry measuring device (ICP-OES, Optima 8300, Parkin-Elmer). The measurement of the leaching rate was performed in the same operation.

[0098]

[0099] wherein M 浸出 : the concentration [ppm] of any metal dissolved when the method of the present application was performed for leaching, M 王水 Leaching: the concentration [ppm] of any metal dissolved when leaching was performed with aqua regia.

[0100] (2) Experimental results

[0101] (Leaching of metal powder)

[0102] The results under respective conditions are shown in Figure 2 From the results, it was found that by adding both the additives, Pt can be leached with high efficiency. By mixing TCCA with MSA in the hydrophobic DES, chlorine was generated, and thus it was investigated whether chlorine plays a role in acidifying the metal.

[0103] (Composition of automobile catalyst)

[0104] The analysis results of the catalyst obtained by leaching with aqua regia are shown in Table 1. From the results, it was found that in the catalyst used this time, Pt, Pd, Rh were contained respectively, and in addition, a large amount of impurity metals such as Al and / or Mg were contained.

[0105] Table 1

[0106]

[0107] Table 1. Metal content [g / kg] of automobile catalyst

[0108] (Leaching of automobile catalyst)

[0109] 1) Effect of additives on leaching selectivity

[0110] The results of investigating the effect of additives on leaching selectivity are shown in Figure 3 From the results, it was found that in the system in which both the chlorinating agent TCCA and the organic acid MSA were added in addition to the hydrophobic DES, the leaching rate of PGM was improved.

[0111] 2) Comparison between the conventional leaching method (hydrochloric acid-hydrogen peroxide extraction) and the leaching method using hydrophobic DES

[0112] The comparison of the leaching rate between the conventional method and the method of the present invention is shown in Figure 4 .

[0113] Compared with the conventional method, the method of the present invention can efficiently leach the three metals of PGM and significantly suppress the leaching of unwanted metals. This selectivity is due to the fact that only PGM can stably exist in the hydrophobic DES. In the solvent composed of two additives and DES, there are many chloride ions, and the platinum group metals exist in the form of anionic complexes with chloride ions as ligands. The anionic complexes interact with the cations of the P6Cl ionic liquid to form stable ion pairs. Therefore, in the system of the present invention, the anionic complexes of PGM can stably exist in the form of DES with the P6Cl ionic liquid as a component. On the other hand, due to the ability to suppress the leaching of Mg 2+ 、Al 3+ and / or La 3+ Impurity metals exist in the form of cations and cannot be stabilized in DES, so they are difficult to dissolve and leach.

[0114] 3) Research on the amount of additives

[0115] The effect of the addition amount of TCCA and MSA on the leaching rate is shown in Figure 5 .

[0116] When the MSA addition level was fixed at 14% by mass and the TCCA addition level was varied, the leaching rates of platinum (Pt), palladium (Pd), and rhodium (Rh) all reached their maximum values ​​at a TCCA addition level of 1.4% by mass. Furthermore, when the TCCA addition level was fixed at 1.4% by mass and the MSA addition level was varied, the results showed that the leaching rate of PGMs did not change with the MSA addition level. On the other hand, it was found that an MSA addition level of less than 1.4% by mass promotes the leaching of impurity metals such as Al and / or La. Therefore, it was determined that an addition level of 1.4% by mass of TCCA and 7.1% by mass of MSA is the most preferred.

[0117] 4) Research on the types of additives (chlorinating agents)

[0118] The results of the study on the effect of chlorination agents on leaching rate are shown in Figure 6 MSA and three chlorinating agents (TCCA, N-chlorophthalimide (NCl), and dichloramine B (GB)) were added. The results showed that TCCA had the highest leaching efficiency for PGM. Adding chlorinating agents to MSA could leach PGM.

[0119] 5) Research on the types of additives (organic acids)

[0120] The results of the study on the effects of chlorinating agents and organic acids on the leaching rate are shown in Figure 7 TCCA and two acids (MSA and formic acid) were added. The results showed that MSA had the highest leaching efficiency for PGM. Adding acid to TCCA could leach PGM.

[0121] 6) Research on the types of DES mixing ratios (P6Cl:decA)

[0122] The results of a study on the effect of the DES mixing ratio on the leaching rate are shown in Figure 8 It can be seen that the leaching rate of PGM is the highest when P6Cl:decA = 1:2, 1:3, and 1:4. In addition, when only decanoic acid is used as the solvent, PGM is almost not leached, which shows that P6Cl is an important component of the solvent.

[0123] 7) Investigation of DES composition (influence of hydrogen bond donors)

[0124] The results of the study on the effect of the types of HBD (caprylic acid (C8), capric acid (C10), lauric acid (C12), and decanol (C10(OH))) as the components of DES on the leaching rate are shown in FIG. Figure 9 Experiments with varying the chain length of the aliphatic portion of the hydrogen bond donor fatty acid revealed that PGMs could be efficiently leached at any length. Furthermore, it was found that PGMs could be leached even when the fatty acid was replaced with a long-chain alcohol.

[0125] 8) Research on organic solvent dilution of solid-liquid extractants

[0126] The results of the study on the effect of solvent on leaching rate are shown in Figure 10 .

[0127] The solvent was adjusted to a molecular molar ratio of P6Cl to organic solvent (toluene, dodecane) of 1:2. The results showed that PGM leaching can also be achieved in a system where P6Cl is dissolved in a non-polar organic solvent.

[0128] Example 2

[0129] (Separation of metals from leachate)

[0130] (1) Experimental operation

[0131] Stripping operation

[0132] An automotive catalyst leachate was prepared using the method described in Example 1. TCCA and MSA were added at optimal levels of 1.4% by mass and 7% by mass, respectively. This leachate contained Pt, Pd, and Rh, the PGMs to be recovered, and Al and La, the PGMs to be removed.

[0133] The results of the preliminary experiment showed the possibility of recovering Al and La by water, recovering Rh by 5M NH4Cl, recovering Pd by 0.005M thiourea, and recovering Pt by 10M NH4NO3. Therefore, water, 5M NH4Cl, 0.005M thiourea, and 10M NH4NO3 were contacted with the leachate in this order. Figure 11 The flow chart of the stripping operation is shown, showing the experimental conditions.

[0134] Determination of stripping rate

[0135] After stripping, 100 μL of the hydrophobic DES phase was diluted 20-fold with 20% of a 1 ppm Y calibration curve solution and 80% EtOH. The metal concentration was then measured using an inductively coupled plasma optical emission spectrometer (ICP-OES, Optima 8300, Parkin-Elmer). The stripping rate was calculated using the following formula.

[0136]

[0137] Among them, M 各水溶液 : The metal concentration recovered in each aqueous solution [ppm], M 萃取前 : Metal concentration before stripping [ppm].

[0138] (2) Experimental results

[0139] Stripping 1: Separation of Al and La

[0140] The aqueous phase (A) and the organic phase (O) consisting of the leachate and water were contacted at a ratio of aqueous phase: organic phase = 1:10 at 25°C and stirred for 1 hour. The amount of metal recovered in the aqueous phase was as follows: Figure 12 The results show that 96% of the impurity metal lanthanum (La) and 97% of aluminum (Al) were recovered. However, approximately 10% of rhodium (Rh) escaped into the aqueous phase. It is speculated that La and Al are efficiently concentrated in the aqueous phase due to hydration, while the small amount of Rh escaping is due to some Rh binding to water molecules as ligands, rendering it hydrophilic and thus entering the aqueous phase.

[0141] Stripping 2: Separation of Rh

[0142] After the leaching solution from which Al and La were removed was contacted with 5M NH4Cl at A:O=2:1 and 25°C for 24h, the amount of metals that could be recovered from the aqueous phase was as follows: Figure 13 shown.

[0143] The results showed that platinum (Pt) and palladium (Pd) remained in the deep eutectic solvent (DES) phase, while only rhodium (Rh) was successfully recovered from the aqueous phase at 73%. This is presumably because the coordination structure of rhodium changes upon contact with aqueous solution, and the resulting hydrophilic rhodium complex migrates into the aqueous phase.

[0144] Stripping 3: Separation of Pd

[0145] After the leachate from which Al, La and Pt were removed was contacted with 0.005 M thiourea at A:O=2:1 and 25°C for 15 min, the amount of metals that could be recovered from the aqueous phase was as follows: Figure 14 shown.

[0146] The results showed that platinum (Pt) remained in the DES phase, while only palladium (Pd) achieved 95% recovery from the aqueous phase. This is presumably because thiourea easily coordinates with palladium (Pd), promoting its migration into the aqueous phase.

[0147] Stripping 4: Separation of Pt

[0148] After the leachate from which Al, La, Pt and Pd were removed was contacted with 10M NH4NO3 at A:O=2:1 and 25°C for 24h, the amount of metals that could be recovered from the aqueous phase was as follows: Figure 15 When ultraviolet-visible (UV) spectroscopy was performed on the hydrophobic deep eutectic solvent (DES) phase, a significant enhancement of the characteristic peak of nitrate ions was observed. Based on this, it was speculated that an anion exchange reaction occurred between the platinum anion complex and the nitrate ion, promoting the migration of platinum into the aqueous phase.

Claims

1. A solid-liquid extractant for platinum group metals comprising (a) a hydrophobic deep eutectic solvent.

2. The solid-liquid extractant of platinum group metals according to claim 1, wherein (a) The hydrophobic deep eutectic solvent is a mixture of a hydrogen bond acceptor having a hydrophobic group and a hydrogen bond donor having a hydrophobic group.

3. The solid-liquid extractant of platinum group metals according to claim 2, wherein: The hydrogen bond acceptor having a hydrophobic group is a compound selected from a phosphonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an ammonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a sulfonium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, an imidazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyrazolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, a pyridinium compound having at least one hydrocarbon group having 6 to 30 carbon atoms, and a pyrrolium compound having at least one hydrocarbon group having 6 to 30 carbon atoms.

4. The solid-liquid extractant of platinum group metals according to claim 2, wherein: The hydrogen bond donor having a hydrophobic group is a compound selected from an organic acid having a hydrocarbon group having 6 to 30 carbon atoms and an alcohol having a hydrocarbon group having 6 to 30 carbon atoms.

5. The solid-liquid extractant of platinum group metals according to claim 1, wherein It further contains one or more selected from (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent.

6. The solid-liquid extractant of platinum group metals according to claim 5, wherein Contains (b) an organic acid having 1 to 4 carbon atoms and (c) a halogenating agent.

7. The solid-liquid extractant of platinum group metals according to claim 5, wherein (b) The organic acid having 1 to 4 carbon atoms is at least one selected from the group consisting of formic acid, fatty acids having 2 to 4 carbon atoms, and alkanesulfonic acids having 1 to 4 carbon atoms.

8. The solid-liquid extractant of platinum group metals according to claim 5, wherein (c) The halogenating agent is one or more selected from trihalogenated cyanuric acid, N-halogenated dicarboxylic acid imide compound, N,N-dihalogenated sulfonamide compound, thionyl halide, sulfuryl halide, phosphorus halide, acyl halide, dihalogenated cyanuric acid, monohalogenated cyanuric acid, trihalogenated isocyanuric acid, dihalogenated isocyanuric acid, monohalogenated isocyanuric acid and halosilane compound.

9. The solid-liquid extractant of platinum group metals according to claim 5, wherein (b) The amount of the organic acid having 1 to 4 carbon atoms added is 5.0% by mass or more relative to the solid-liquid extractant for the platinum group metal.

10. The solid-liquid extractant of platinum group metals according to claim 5, wherein (c) The amount of the halogenating agent added is 1.0 mass % or more relative to the solid-liquid extractant of the platinum group metal.

11. The solid-liquid extractant of platinum group metals according to claim 1, wherein: It further contains (d) a non-polar organic solvent.

12. A solid-liquid extraction method for platinum group metals, characterized in that: A solid-liquid extractant for platinum group metals according to any one of claims 1 to 11 is added to a pulverized product of a solid article or solid composition containing a platinum group metal compound and other metal compounds, and the platinum group metals are leached in the extractant.

13. A method for recovering platinum group metals, comprising: adding a solid-liquid extractant for platinum group metals according to any one of claims 1 to 11 to a pulverized product of a solid object or solid composition containing a platinum group metal compound and other metal compounds, thereby leaching the platinum group metals in the extractant; and extracting each platinum group metal from the leachate obtained.

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