JP2022123879A - Method for recovering platinum group metal - Google Patents

Abstract

To provide a method for recovering platinum group metal other than platinum which is reduced in an environmental load and energy consumption.SOLUTION: A method for recovering platinum group metal includes the steps of: (1a) bringing a substance containing at least platinum group metal selected from palladium, ruthenium, osmium, iridium and rhodium into contact with a molten salt containing an iron halide, and obtaining a treated object in which a halide of the platinum group metal is dissolved in the molten salt; (2a) cooling the treated object, and obtaining a solid; (3a) treating the solid using water or an aqueous solution in which the halide of the platinum group metal is soluble, and obtaining a water dispersion, or treating the solid using an organic solvent in which the halide of the platinum group metal is hardly soluble, and obtaining a dispersion; and (4a) separating a liquid containing a component containing the platinum group metal from the water dispersion, or separating the solid containing the halide of the platinum group metal from the dispersion.SELECTED DRAWING: None

Description

There is an application for exception to loss of novelty

The present disclosure relates to methods for recovery of platinum group metals.

The platinum group metals, represented by platinum (Pt), palladium (Pd) and rhodium (Rh), are important metals for industrial applications as well as for jewelry and property applications. Platinum group metals are often used as catalysts for automobiles because they have high catalytic activity and are chemically stable.

Since platinum group metals are scarce in terms of resources and have a large environmental impact during smelting, they are being actively recycled from used products such as used automobile catalysts. Recycling methods for platinum group metals are roughly divided into two types: wet methods in which substances containing platinum group metals are dissolved in chemicals, and dry methods in which the substances are treated at high temperatures. Wet methods often use aqua regia or a hydrochloric acid-chlorine system to dissolve the platinum group metals. In the dry method, the above substances are put into the smelting process of base metals, melts such as copper (Cu) and lead (Pb) are used as collector metals, and the platinum group metals are concentrated in the collector metals and recovered. Commonly used. Platinum group metals concentrated by collector metals are mainly processed by wet processes.

However, the aqua regia or the hydrochloric acid-chlorine system used in the wet method imposes a large environmental load during waste liquid treatment. Moreover, rhodium and iridium are sparingly soluble in aqua regia, and are difficult to treat by common processes. On the other hand, the process using a collector metal in the dry process consumes a large amount of energy, and since the treatment and purification are ultimately performed by the wet process, the problem of waste liquid generation has not been solved.

Therefore, various methods have been proposed for the development of environmentally friendly processes, and in recent years, a method using molten salt has also been proposed. For example, Patent Literature 1 discloses a method in which an ore is put into a composite molten salt of ammonium nitrate (NH ₄ NO ₃ ) and ammonium chloride (NH ₄ Cl), and platinum contained in the ore is directly chlorinated and recovered. is disclosed. Non-Patent Document 1 discloses a platinum recovery method using a composite molten salt of iron chloride (III) (FeCl ₃ ) and potassium chloride (KCl).

U.S. Pat. No. 3,988,415

Journal of the Japan Institute of Metals Vol.83 No.1 (2019) 23-29

The conventional method using a molten salt has the problem of high dissolution treatment temperature and high energy consumption. Moreover, the method disclosed in Patent Document 1 has a problem that it is difficult to handle ammonium nitrate. On the other hand, the method disclosed in Non-Patent Document 1 has the advantage that the dissolution treatment temperature is low and the energy consumption is small. However, Non-Patent Document 1 does not disclose an example in which the method is applied to platinum group metals other than platinum. In addition, for example, spent automobile catalysts contain multiple types of platinum group metals, so it is important to separate and recover the multiple types of platinum group metals.

One object of the present disclosure is to provide a method for recovering platinum group metals other than platinum that has a low environmental load and low energy consumption.

One object of the present disclosure is to provide a platinum group metal recovery method that can separate and recover multiple types of platinum group metals with low environmental load and low energy consumption.

A first recovery method for platinum group metals of the present disclosure comprises:
(1a) contacting a substance containing at least one platinum group metal selected from palladium, ruthenium, osmium, iridium and rhodium with a molten salt containing iron halide, and obtaining a processed product in which the compounds are dissolved;
(2a) a step of cooling the treated product to obtain a solid;
(3a) treating the solid with water or an aqueous solution in which the platinum group metal halide is soluble to obtain an aqueous dispersion; or and (4a) separating a liquid containing a component containing the platinum group metal from the aqueous dispersion, or from the dispersion, The step of separating the solid containing the halide of the platinum group metal is included.

A second recovery method for platinum group metals of the present disclosure comprises:
(1b) bringing a substance containing a first platinum group metal and a second platinum group metal into contact with a molten salt containing an iron halide; obtaining a processed product in which the halide of the platinum group metal is dissolved;
(2b) a step of cooling the treated product to obtain a solid;
(3b) The solid is treated with water or an aqueous solution in which the first platinum group metal halide is soluble and the second platinum group metal halide is sparingly soluble to obtain an aqueous dispersion. and (4b) separating the aqueous dispersion into a liquid comprising a component containing the first platinum group metal and a solid residue comprising the halide of the second platinum group metal.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a method for recovering platinum group metals other than platinum with low environmental load and low energy consumption. Advantageous Effects of Invention According to the present disclosure, it is possible to provide a method for recovering platinum group metals that is capable of separating and recovering a plurality of types of platinum group metals with low environmental load and low energy consumption.

FIG. 1 is an Ellingham diagram for chlorides of iron and palladium. FIG. 2 is an example of the flow of the first recovery method for platinum group metals of the present disclosure. FIG. 3 is an example flow of the second recovery method for platinum group metals of the present disclosure. 4 is a graph showing changes in the amount of dissolved sample in Example 1. FIG. FIG. 5 is a graph showing changes in the amount of sample dissolved in Example 2. FIG. 6 is a graph showing changes in the amount of dissolved sample in Example 3. FIG. FIG. 7 is a graph showing changes in the amount of dissolution of the sample in Example 3. FIG. FIG. 8 is an example of the flow of the first recovery method for platinum group metals of the present disclosure.

In this specification, "A to B" indicating a numerical range includes numerical values A and B described before and after "to" as lower and upper limits, or upper and lower limits. For example, "1 to 10" means a numerical range from 1 to 10.

[First recovery method of platinum group metal]
A first recovery method for platinum group metals of the present disclosure comprises:
(1a) contacting a substance containing at least one platinum group metal selected from palladium, ruthenium, osmium, iridium and rhodium with a molten salt containing iron halide, and obtaining a processed product in which the compounds are dissolved;
(2a) a step of cooling the treated product to obtain a solid;
(3a) treating the solid with water or an aqueous solution in which the platinum group metal halide is soluble to obtain an aqueous dispersion; or and (4a) separating a liquid containing a platinum group metal-containing component from the aqueous dispersion; Separating solids containing halides of platinum group metals.

The molten salt is preferably a molten salt of a mixture containing an iron halide and an alkali metal or alkaline earth metal halide. Hereinafter, the molten salt of this mixture is also referred to as "composite molten salt".

In one embodiment, the first recovery method for platinum group metals of the present disclosure comprises:
(5a) a step of adding a precipitating agent for a platinum group metal to the liquid, precipitating a component containing a platinum group metal, collecting the precipitated component (precipitate), and calcining it;
(5a') Further includes steps including steps (5a'-1) to (5a'-2) described below.

<Step (1a)>
In step (1a), for example, the substance containing the platinum group metal is brought into contact with the iron halide or the mixture containing the iron halide, and heated. This melts the iron halide or mixture thereof to form a molten salt, and the platinum group metal is converted to a halide, preferably a chloride, and dissolved in the molten salt.

In step (1a), the substance containing the platinum group metal may also be introduced into the molten salt. As a result, the platinum group metal is converted to a halide and dissolved in the molten salt.

The contact is preferably carried out under dry conditions, ie in the absence of water or organic solvents.
Hereinafter, the series of operations in step (1a) for the platinum group metal is also referred to as "dissolution treatment".

Examples of substances containing platinum group metals include catalysts such as vehicle exhaust gas purification catalysts and petrochemical catalysts, electronic materials such as electronic substrates and lead frames, platinum group metal-containing blast powder, permanent magnets, crucibles, and these. Also included are ores containing platinum group metals and jewelry containing platinum group metals.

A catalyst, such as a catalyst for purifying vehicle exhaust gas, in one embodiment, includes a carrier and a platinum group metal, which is a catalytic component carried on the carrier. Examples of the carrier include ceramic-based carriers made of alumina, silica, etc., and SUS-based carriers. Examples of the shape of the carrier include honeycomb shape and pellet shape. The platinum group metals include, for example, a combination of platinum and palladium, a combination of platinum and rhodium, a combination of palladium and rhodium, a combination of platinum, palladium and rhodium. Specifically, platinum-palladium-rhodium ternary Catalyst components are included. For example, the carrier can be separated from the catalyst by using conventionally known methods such as pulverization treatment and elution treatment using acid, or by appropriately combining these methods. Examples of crucibles include crucibles for semiconductor manufacturing, specifically crucibles made of iridium.

In the first recovery method of the platinum group metal of the present disclosure, the platinum group metal is at least one selected from palladium, ruthenium, osmium, iridium and rhodium, and at least one selected from palladium, iridium and rhodium is preferred, and at least one selected from palladium and rhodium is more preferred. In the first recovery method, the substance may contain platinum.
The substance contains one or more platinum group metals.

The present disclosure uses at least iron halides. One type or two or more types of iron halides may be used. Iron halides are used to halogenate platinum group metals and dissolve them in molten salts. That is, the iron halide is a halogenating agent, particularly a chlorinating agent, for platinum group metals, and thus chlorine gas or the like is not required in the present disclosure. In addition, the iron halide can be melted at a low temperature, contributing to a reduction in energy consumption during the melting process.

Iron halides include, for example, iron (III) chloride (FeCl ₃ ), iron (III) bromide (FeBr ₃ ) and iron (III) iodide (FeI ₃ ), which are excellent at chlorinating platinum group metals. Iron (III) chloride is preferable from the viewpoint that it can be used.

The amount of the iron halide to be used is preferably 1 to 200 mol, more preferably 5 to 150 mol, still more preferably 10 to 100 mol, per 1 mol of the platinum group metal contained in the substance. By using the iron halide in such a range, the platinum group metal can be satisfactorily halogenated, so that the platinum group metal can be dissolved in the molten salt.

In the present disclosure, it is preferred to use a molten salt of a mixture comprising an iron halide and an alkali metal or alkaline earth metal halide. Alkali metal halides may be used alone or in combination of two or more. Alkaline earth metal halides may be used alone or in combination of two or more. An alkali metal halide and an alkaline earth metal halide may be used in combination.

Among iron halides, there are compounds, such as iron (III) chloride, whose melting and boiling points are close to each other, and such compounds may have high vapor pressures near their melting points. Alkali metal or alkaline earth metal halides can be used to lower the melting temperature of the halogenating agent (iron halide) for the platinum group metals. As a result, it is possible to improve the handleability of the molten salt and further reduce the energy consumption during the dissolution treatment.

Alkali metal halides include, for example, lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, cesium fluoride, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, lithium bromide, odorant sodium iodide, potassium bromide, rubidium bromide, cesium bromide, lithium iodide, sodium iodide, potassium iodide, rubidium iodide and cesium iodide.

Alkaline earth metal halides include, for example, magnesium fluoride, calcium fluoride, barium fluoride, strontium fluoride, magnesium chloride, calcium chloride, barium chloride, strontium chloride, magnesium bromide, calcium bromide, bromide Barium, strontium bromide, magnesium iodide, calcium iodide, barium iodide and strontium iodide.

Among these, alkali metal chlorides are preferable, sodium chloride and potassium chloride are more preferable, and potassium chloride is particularly preferable, from the viewpoint that the melting temperature of the mixture can be satisfactorily lowered.

The amount of alkali metal or alkaline earth metal halide used is preferably 0.1 to 10 mol, more preferably 0.2 to 5 mol, and still more preferably 0.5 to 1 mol, per 1 mol of iron halide. 2 mol, particularly preferably 0.8 to 1.2 mol. By using the alkali metal or alkaline earth metal halide in such a range, the melting temperature of the above mixture can be satisfactorily lowered.

The heating temperature for melting the iron halide or the mixture is preferably the melting temperature of the iron halide or the mixture or higher and 450° C. or lower, more preferably 250 to 420° C., still more preferably 255 to 400° C., particularly preferably 280 to 380°C. Heating at such a temperature causes the platinum group metal to dissolve in the molten salt. The method of the present disclosure has less energy consumption and environmental load than the conventional method using molten salt, which requires dissolution treatment at 500° C. or higher.

The treatment time of dissolution treatment is preferably 0.1 to 20 hours, more preferably 0.3 to 15 hours, still more preferably 0.5 to 10 hours, still more preferably 1 to 10 hours, 2 to 10 hours, or 4 to 10 hours. In the dissolution treatment, the molten salt may be stirred from the viewpoint of improving the dissolution rate of the platinum group metal.
The atmosphere during the dissolution treatment is, for example, an inert gas atmosphere such as argon and nitrogen.

Hereinafter, a substance containing palladium as a platinum group metal, a composite molten salt containing iron (III) chloride as an iron halide, and potassium chloride as an alkali metal halide (complex melting of a mixture of iron (III) chloride and potassium chloride) An embodiment using a salt) will be described.

The standard Gibbs energies of formation of iron(III) chloride, iron(II) chloride (FeCl ₂ ) and palladium(II) chloride (PdCl ₂ ), respectively, and the standard in the chlorination reaction of iron(II) chloride to iron(III) chloride. Reaction Gibbs energy and FactSage database (CW Bale, E. Belisle, P. Chartrand, SA Decterov, G. Eriksson, K. Hack, I.-H. Jung, Y.-B. Kang, J. Melancon, AD Pelton, C. Robelin and S. Petersen: Calphad., 33 (2009), 295-31.). FIG. 1 shows an Ellingham diagram for chlorides of iron and palladium.

Comparing the standard Gibbs energy change associated with the chlorination of palladium with the standard Gibbs energy change associated with the chlorination reaction from iron(II) chloride to iron(III) chloride reveals that the former is larger than the latter.

Assuming that palladium (II) chloride is produced by the reaction shown in formula (1), the Gibbs energy change calculated for 1 mol of palladium is −90.3 kJ at 327° C. (600 K). Thus, it is considered that the chlorination of palladium proceeds spontaneously within the temperature range shown in FIG.
Pd+2FeCl3→ _{PdCl2 + 2FeCl2} (1)

Therefore, it is thought that when palladium is introduced into the molten salt of iron (III) chloride, iron (III) chloride acts as a chlorinating agent for palladium to produce palladium chloride, and palladium dissolves in the molten salt. In the present embodiment, potassium chloride is mixed with iron(III) chloride, so it is considered that potassium chloride palladium(II) (K ₂ [PdCl ₄ ]) is produced by the reaction shown in formula (2). When the above substance contains platinum in addition to palladium, it is considered that potassium chloroplatinate (IV) (K ₂ [PtCl ₆ ]) is also produced by the reaction shown in formula (3). In the case of rhodium, it is considered that potassium rhodate (III) chloride (K ₃ [RhCl ₆ ]) is produced by the reaction shown in formula (4). In the case of iridium, it is considered that potassium iridate (III) chloride (K ₃ [IrCl ₆ ]) is produced by the reaction shown in formula (5).

Pd+2FeCl ₃ +2KCl→K ₂ [PdCl ₄ ]+2FeCl ₂ (2)
Pt+4FeCl ₃ +2KCl→K ₂ [PtCl ₆ ]+4FeCl ₂ (3)
Rh+3FeCl ₃ +3KCl→K ₃ [RhCl ₆ ]+3FeCl ₂ (4)
Ir+3FeCl ₃ +3KCl→K ₃ [IrCl ₆ ]+3FeCl ₂ (5)

In the above embodiment, an example was described in which a substance containing palladium as a platinum group metal and a composite molten salt of a mixture containing iron (III) chloride as an iron halide and potassium chloride as an alkali metal halide were used. By calculating the standard reaction Gibbs energy of the halogenation reaction of platinum group metals and the standard Gibbs energy of formation of iron halide using thermodynamic calculation software, even in cases other than the above examples, halides of platinum group metals A dissolved molten salt can be obtained appropriately.

<Step (2a)>
In step (2a), the treated product obtained in step (1a) is cooled and solidified to solidify. The solid comprises a halide of said platinum group metal, preferably a chloride of said platinum group metal (for example potassium palladium(II) chloride, rhodate(III) chloride or potassium iridate(III) chloride).

The temperature at the time of cooling is not particularly limited as long as it is lower than the melting temperature of the iron halide or the above mixture, but is preferably 95° C. or less, more preferably 5 to 80° C., still more preferably 10 to 60° C. The form is room temperature. As the cooling method, a conventionally known cooling method can be used, and the object to be treated may be left still in a room temperature environment.

<Step (3a)>
In step (3a), in one embodiment, the solid obtained in step (2a) is treated with water or an aqueous solution in which the platinum group metal halide is soluble to obtain an aqueous dispersion. For example, the solid is immersed in water or an aqueous solution. Thus, the operation of dissolving a specific component contained in a solid in water or an aqueous solution is generally called "leaching treatment", and the dissolution medium, such as water or aqueous solution, is called a "leaching liquid". Sometimes. As a result, the platinum group metal halide (e.g., potassium palladium chloride (II), potassium rhodate chloride (III), or potassium chloride iridate (III)) contained in the solid dissolves in water or an aqueous solution. . Potassium chloride palladium(II), potassium chloride rhodate(III) and potassium chloride iridate(III) are readily soluble or soluble in water.

In step (3a), in one embodiment, water or an aqueous solution in which the halide of the platinum group metal is soluble is used as the leaching liquid. Since water or an aqueous solution is used as the leaching liquid, waste liquid treatment is easy, and the recovery method of the present disclosure has a small environmental load. The aqueous solution includes, for example, an aqueous solution of an alkali metal salt such as an aqueous potassium chloride solution, an aqueous sodium chloride solution, and an aqueous sodium nitrite solution. When the aqueous solution is used as the leaching liquid, the platinum group metal halide may be dissolved in the aqueous liquid in the form of another salt.

The concentration of the alkali metal salt in the aqueous solution is preferably 0.1-30 g/100 mL, more preferably 0.5-20 g/100 mL, and even more preferably 1-15 g/100 mL.

The aqueous dispersion comprises, for example, an aqueous liquid containing a platinum group metal-containing component (for example, a platinum group metal halide) and a solid dispersed in the aqueous liquid.

On the other hand, impurities that can be generated during the dissolution treatment in step (1a) include, for example, iron oxide generated from iron chloride (III) by oxygen gas mixed in the system. Iron oxide is sparingly soluble in water. Therefore, such impurities can be removed by subjecting the aqueous dispersion to solid-liquid separation treatment in the subsequent step (4a).

In step (3a), in one embodiment, the solid obtained in step (2a) is treated with an organic solvent (leaching liquid) in which the halide of the platinum group metal is poorly soluble to obtain a dispersion. obtained (first leaching process). For example, the solid is immersed in an organic solvent. Alcohol such as ethanol is used as the organic solvent. As a result, the iron halide such as iron(III) chloride contained in the solid is dissolved in the organic solvent. On the other hand, for example, halides of platinum group metals (eg, potassium rhodate(III) chloride and potassium iridate(III) chloride) are poorly soluble in ethanol and therefore remain in the solid.

Iron halides, such as iron(III) chloride, used in the dissolution treatment of step (1a) can become impurities in the final product. Such impurities can be removed by dissolving the iron halide in the organic solvent and subjecting the dispersion to solid-liquid separation in the subsequent step (4a).

Therefore, the leaching liquid is not limited to ethanol. For example, an organic solvent in which iron halides such as iron (III) chloride are soluble and halides such as chlorides of platinum group metals are insoluble can be used. Examples of the organic solvent include, in addition to the alcohol solvents described above, ester solvents, ether solvents, ketone solvents, and nitrogen-containing solvents.

The temperature of the leaching liquid is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The leaching treatment time is preferably 1 hour or more, more preferably 5 to 100 hours, and even more preferably 10 to 60 hours.

<Step (4a)>
In step (4a), in one embodiment, a component containing a platinum group metal (e.g., The liquid containing platinum group metal halides) is separated. A platinum group metal can be easily recovered from this liquid by a conventionally known method such as a crystallization method. In one embodiment of the present disclosure, a highly pure platinum group metal can be recovered by performing step (5a) described below.

In step (4a), in one embodiment, a solid containing a platinum group metal halide is separated from the dispersion obtained in step (3a) by solid-liquid separation treatment such as filtration and centrifugation. do. The platinum group metal can be easily recovered from this solid by a conventionally known method such as leaching treatment. In one embodiment of the present disclosure, a highly pure platinum group metal can be recovered by performing step (5a') described below.

<Step (5a)>
In step (5a), a precipitating agent for platinum group metal is added to the liquid (for example, filtrate) containing the platinum group metal-containing component separated in step (4a). As a result, the component containing the platinum group metal can be converted, for example, into the form of a sparingly soluble salt and precipitated. Thus, the component containing the platinum group metal in the liquid and the component containing the platinum group metal after deposition are usually different.

Precipitating agents include, for example, chlorides of monovalent cations such as ammonium chloride. The precipitating agent may be used alone or in combination of two or more. When ammonium chloride is used, the precipitated platinum group metal-containing component comprises the ammonium component. For example, when the liquid contains K ₃ [Rh(NO ₂ ) ₆ ], (NH ₄ ) ₃ [Rh(NO ₂ ) ₆ ] precipitates. Therefore, by firing a component containing a platinum group metal, a platinum group metal of high purity can be obtained.

From the viewpoint of promoting the precipitation well, it is preferable to use an acid together with the precipitating agent. Acids include, for example, hydrogen chloride and nitric acid. 1 type or 2 types or more may be sufficient as an acid. It is preferred to use hydrogen chloride and nitric acid in combination. In one embodiment, aqueous ammonium chloride, hydrochloric acid and nitric acid are added to the liquid. As a result, for example, when the liquid contains potassium chloropalladium(II) (K ₂ [PdCl ₄ ]) as a platinum group metal halide, the palladium ions become tetravalent and ammonium chloropalladium(IV) ((NH ₄ ) ₂ [PdCl ₆ ]) precipitates.

The amount of nitric acid to be added is preferably 1 to 500 mol, more preferably 50 to 300 mol, still more preferably 90 to 250 mol, per 1 mol of the platinum group metal-containing component contained in the liquid. As a result, the oxidation of palladium ions, for example, tends to proceed satisfactorily, and the deposition by the precipitating agent tends to proceed satisfactorily.

The amount of hydrogen chloride to be added is preferably 1 to 300 mol, more preferably 30 to 250 mol, still more preferably 80 to 150 mol, per 1 mol of the platinum group metal-containing component contained in the liquid. As a result, the oxidation of palladium ions, for example, tends to proceed satisfactorily, and the deposition by the precipitating agent tends to proceed satisfactorily.

The amount of the precipitating agent to be added is preferably 0.1 to 20 mol, more preferably 0.5 to 10 mol, still more preferably 1 to 5 mol, per 1 mol of the platinum group metal-containing component contained in the liquid. Mole.

In the step (5a), from the viewpoint of promoting the precipitation, the temperature of the liquid during the precipitation treatment is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The treatment time for the precipitation treatment is preferably 1 hour or longer, more preferably 5 to 100 hours, and still more preferably 10 to 60 hours.

In step (5a), subsequently, the component containing the precipitated platinum group metal is recovered by solid-liquid separation treatment such as filtration treatment and centrifugation treatment. On the other hand, iron (III) chloride and potassium chloride, which are highly soluble in water, can be removed by this solid-liquid separation treatment.

Subsequently, the component containing the platinum group metal is fired. By such operation, the platinum group metal can be recovered. The temperature during firing is not particularly limited as long as it is a temperature at which components other than platinum group metals can be volatilized or decomposed. is. The firing time is preferably 0.1 to 20 hours, more preferably 0.3 to 10 hours, still more preferably 0.5 to 5 hours. Examples of the firing atmosphere include an inert gas atmosphere such as argon and nitrogen, and a hydrogen gas atmosphere. When the precipitate is, for example, ammonium chloropalladium(IV)ate ((NH ₄ ) ₂ [PdCl ₆ ]), this calcination yields highly pure palladium.

<Step (5a')>
In step (5a′), (5a′-1) the solid containing platinum group metal halide separated in step (4a) is treated with water or an aqueous solution to obtain a component containing platinum group metal. A step of obtaining an aqueous dispersion dissolved in water, and (5a′-2) separating a liquid containing a component containing a platinum group metal from the aqueous dispersion, further comprising (5a′-3) the liquid may include a step of adding a precipitating agent for a platinum group metal to precipitating a component containing a platinum group metal, recovering the precipitated component, and subjecting it to a reduction treatment if necessary.

In step (5a′-1), the solid obtained in step (4a) is treated with water or an aqueous solution in which the halide of the platinum group metal is soluble to obtain an aqueous dispersion (second leaching process). For example, the solid is immersed in water or an aqueous solution. As a result, the platinum group metal halide contained in the solid is dissolved in water or an aqueous solution as a platinum group metal-containing component (for example, a platinum group metal sulfate such as rhodium sulfate and iridium sulfate). Rhodium sulfate and iridium sulfate are readily soluble in water.

In one embodiment, in step (5a′-1), water or an aqueous solution in which the halide of the platinum group metal is soluble is used as the leaching liquid. Since water or an aqueous solution is used as the leaching liquid, waste liquid treatment is easy, and the recovery method of the present disclosure has a small environmental load. Examples of aqueous solutions include aqueous solutions of alkali metal salts such as aqueous potassium sulfate solutions and aqueous sodium sulfate solutions, particularly aqueous solutions of alkali metal sulfates. In addition, aqueous sulfuric acid solutions can also be used. When the aqueous solution is used as the leaching liquid, the platinum group metal halide may be dissolved in the aqueous liquid in the form of another salt.

The concentration of the alkali metal salt in the aqueous solution is preferably 0.1-30 g/100 mL, more preferably 0.5-20 g/100 mL, and even more preferably 1-15 g/100 mL.

The aqueous dispersion comprises, for example, an aqueous liquid containing a platinum group metal-containing component and a solid dispersed in the aqueous liquid.

Impurities that can be generated during the dissolution treatment of step (1a) include, for example, iron oxide produced from iron chloride (III) by oxygen gas mixed in the system. Iron oxide is sparingly soluble in water. Therefore, such impurities can be removed by subjecting the aqueous dispersion to solid-liquid separation treatment in the subsequent step (5a'-2).

The temperature of the leaching liquid is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The leaching treatment time is preferably 1 hour or more, more preferably 5 to 100 hours, and even more preferably 10 to 60 hours.

In step (5a′-2), in one embodiment, the aqueous dispersion obtained in step (5a′-1) is subjected to solid-liquid separation treatment such as filtration and centrifugation to remove the platinum group metal. Separate the liquid containing the contained components. A platinum group metal can be easily recovered from this liquid by a conventionally known method such as a crystallization method. In one embodiment of the present disclosure, a highly pure platinum group metal can be recovered by performing step (5a'-3) described below.

In step (5a'-3), a precipitating agent for platinum group metal is added to the liquid (for example, filtrate) containing the platinum group metal-containing component separated in step (5a'-2). This allows the component containing the platinum group metal to be deposited, for example, as a hydroxide of the platinum group metal or an oxide of the platinum group metal. Thus, the component containing the platinum group metal in the liquid and the component containing the platinum group metal after deposition are usually different.

Precipitating agents include, for example, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide. The precipitating agent may be used alone or in combination of two or more. For example, if the liquid contains rhodium sulfate, Rh ₍ OH) ₃ or _Rh2O3 may precipitate.

Therefore, by subjecting a component containing a platinum group metal (for example, a hydroxide of a platinum group metal or an oxide of a platinum group metal) to a reduction treatment, a platinum group metal of high purity can be obtained. Hydroxides of platinum group metals or oxides of platinum group metals may also be used as source materials for the preparation of other compounds. Thus, the method of the present disclosure can be used not only as a method for recycling platinum group metals, but also as a method for producing raw materials from secondary resources.

The amount of the precipitating agent to be added is preferably 0.1 to 20 mol, more preferably 0.5 to 10 mol, and still more preferably 2 to 5 mol, per 1 mol of the platinum group metal-containing component contained in the liquid. Mole.

In the step (5a′-3), from the viewpoint of promoting the precipitation, the temperature of the liquid during the precipitation treatment is preferably 95° C. or less, more preferably 5 to 80° C., further preferably 10 to 60° C. be. The treatment time for the precipitation treatment is preferably 1 hour or longer, more preferably 5 to 100 hours, and still more preferably 10 to 60 hours.

In step (5a'-3), subsequently, the precipitated platinum group metal-containing component is recovered by solid-liquid separation treatment such as filtration treatment and centrifugation treatment. On the other hand, potassium chloride, which is highly soluble in water, can be removed by this solid-liquid separation treatment.

Subsequently, if necessary, the component containing the platinum group metal is subjected to a reduction treatment. By such operation, the platinum group metal can be recovered with high purity. The reduction treatment can be performed by a conventionally known method, and examples thereof include a method of reducing the above components with hydrogen gas. If the precipitate is, for example, Rh(OH) ₃ or Rh ₂ O ₃ , this reduction treatment yields rhodium of high purity.

In order to recover a high proportion of the platinum group metal, it is preferable to separate the platinum group metal from impurities such as iron components and then perform the precipitation treatment. In the case of platinum and palladium to be recovered, for example, the halides are dissolved in water or an aqueous solution by dissolution treatment and leaching treatment, iron oxide is separated by solid-liquid separation treatment, ammonium chloride is added to the filtrate, and it is difficult to dissolve in water. A high proportion of platinum and palladium can be recovered by precipitating the soluble salts. On the other hand, when ammonium chloride is similarly added to a liquid containing a rhodium or iridium halide, the resulting salt is readily soluble in water, so rhodium or iridium should be recovered as a slightly water-soluble salt. can be difficult. Therefore, the recovered rhodium or iridium may be contaminated with impurities. On the other hand, according to the steps (4a) and (5a') described above, since impurities such as iron components can be separated and removed, rhodium and iridium can be recovered at a high rate.

The method of the present disclosure can be performed at a lower temperature than the conventional dry method, can be performed with chemicals that are less regulated than the conventional wet method, and generates less waste liquid. have an advantage. In addition, according to the method of the present disclosure, not only platinum and palladium, but also poorly soluble platinum group metals such as rhodium and iridium can be recovered in a manner with low environmental load and low energy consumption. Therefore, the recycling rate of rhodium and iridium can be efficiently improved by using the method of the present disclosure.

[Second recovery method of platinum group metal]
A second recovery method for platinum group metals of the present disclosure comprises:
(1b) bringing a substance containing a first platinum group metal and a second platinum group metal into contact with a molten salt containing an iron halide; obtaining a processed product in which the halide of the platinum group metal is dissolved;
(2b) a step of cooling the treated product to obtain a solid;
(3b) The solid is treated with water or an aqueous solution in which the first platinum group metal halide is soluble and the second platinum group metal halide is sparingly soluble to obtain an aqueous dispersion. and (4b) separating the aqueous dispersion into a liquid comprising a component containing the first platinum group metal and a solid residue comprising the halide of the second platinum group metal.

Mutual separation of platinum group metals from materials containing more than one platinum group metal generally requires multi-step and complex techniques such as solvent extraction. By using the method of the present disclosure, multiple platinum group metals can be easily separated and recovered as compared to conventional methods.

In one embodiment, the second recovery method for platinum group metals of the present disclosure comprises:
(5b) A liquid containing a component containing the first platinum group metal is added with a precipitating agent for the first platinum group metal to precipitate the component containing the first platinum group metal, and the precipitated component ( Precipitate) is collected and sintered.

In one embodiment, the second recovery method for platinum group metals of the present disclosure comprises:
(6b) treating the solid residue containing the halide of the second platinum group metal with an aqueous solution in which the halide of the second platinum group metal is soluble to obtain an aqueous dispersion;
(7b) separating the liquid containing the component containing the second platinum group metal from the aqueous dispersion; and (8b) adding the second platinum to the liquid containing the component containing the second platinum group metal. It further includes a step of adding a precipitating agent for a group metal, precipitating a component containing a second platinum group metal, collecting the precipitated component (precipitate), and calcining.

<Step (1b) and Step (2b)>
Steps (1b) and (2b) in the second recovery method are the same as steps (1a) and (2a) in the first recovery method, respectively, and the above substances, iron halide and alkali metal or alkali The same applies to specific examples, preferred examples, usage amounts of the earth metal halides, and conditions for dissolution treatment and cooling, and descriptions thereof are omitted in this column. However, in step (1b), a substance containing a first platinum group metal and a second platinum group metal is used.

The first platinum group metal is at least one selected from platinum, palladium, ruthenium, osmium, iridium and rhodium, preferably palladium. The second platinum group metal is at least one selected from platinum, palladium, ruthenium, osmium, iridium and rhodium, and is a metal different from the first platinum group metal, preferably platinum.

In one embodiment, the material comprises palladium as the first platinum group metal and platinum as the second platinum group metal. In one embodiment, the treated material obtained by dissolution treatment includes a palladium halide (eg, potassium chloropalladium(II)) and a platinum halide (eg, potassium chloroplatinate(IV)).

The material may contain additional platinum group metals, such as a third platinum group metal. The materials, in one embodiment, include platinum, palladium and rhodium. Even when the substance contains a third platinum group metal, the first to third platinum group metals are separated and recovered by appropriately selecting the leaching liquid and repeating the steps of the second recovery method. be able to.

The material may comprise an alloy containing a first platinum group metal and a second platinum group metal, such as a platinum-palladium alloy, wherein the first platinum group metal such as palladium and the second platinum group metal such as platinum of platinum group metals may be included as single elements.

<Step (3b)>
Since both the first platinum group metal and the second platinum group metal are dissolved in the molten salt by the dissolution treatment in step (1b), the component containing the first platinum group metal and the second platinum group metal It is necessary to separate the components containing the metal. In step (3b), the solid obtained in step (2b) is added to water or an aqueous solution in which the halide of the first platinum group metal is soluble and the halide of the second platinum group metal is sparingly soluble. (leaching treatment) to obtain an aqueous dispersion. For example, the solid is immersed in water or an aqueous solution. As a result, the first platinum group metal halide (for example, potassium chloropalladium(II)) contained in the solid is dissolved in water or an aqueous solution. On the other hand, the second platinum group metal halide (eg, potassium chloroplatinate(IV)) contained in the solid remains in the solid.

In conventional recovery methods, multiple types of platinum group metals are separated by complicated methods. On the other hand, in the second recovery method of the present disclosure, multiple types of platinum group metals are separated by a simple method utilizing differences in solubility in water or an aqueous solution. Therefore, it is possible to suppress the discharge of the waste liquid, which has a large environmental load.

For example, palladium halides such as potassium chloropalladium(II) are readily soluble in water and aqueous potassium chloride solutions. For example, platinum halides such as potassium chloroplatinate (IV) are poorly soluble in water and aqueous potassium chloride solutions, and the solubility of potassium chloroplatinate (IV) in aqueous potassium chloride solutions is higher than that in water. low. Therefore, as the leaching liquid, it is preferable to use water or an aqueous potassium chloride solution, more preferably an aqueous potassium chloride solution. Thereby, the platinum component and the palladium component can be separated.

The concentration of potassium chloride in the potassium chloride aqueous solution is preferably 0.1-30 g/100 mL, more preferably 0.5-20 g/100 mL, still more preferably 1-15 g/100 mL. The temperature of the leaching liquid is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The leaching treatment time is preferably 1 hour or more, more preferably 5 to 100 hours, and even more preferably 10 to 60 hours.

<Step (4b)>
In step (4b), the aqueous dispersion obtained in step (3b) is subjected to solid-liquid separation treatment such as filtration treatment and centrifugation treatment to remove a component containing a first platinum group metal (e.g., first (platinum group metal halide) and a solid residue comprising a second platinum group metal halide.

<Step (5b)>
In step (5b), a precipitating agent for the first platinum group metal is added to the liquid (eg, filtrate) separated in step (4b) and containing the component containing the first platinum group metal. Thereby, the component containing the first platinum group metal can be deposited.

Precipitating agents include, for example, chlorides of monovalent cations such as ammonium chloride. The precipitating agent may be used alone or in combination of two or more. When ammonium chloride is used, the precipitated first platinum group metal containing component comprises an ammonium component. Therefore, the first platinum group metal of high purity can be obtained by firing the component containing the first platinum group metal.

From the viewpoint of promoting the precipitation well, it is preferable to use an acid together with the precipitating agent. Acids include, for example, hydrogen chloride and nitric acid. 1 type or 2 types or more may be sufficient as an acid. It is preferred to use hydrogen chloride and nitric acid in combination. In one embodiment, aqueous ammonium chloride, hydrochloric acid and nitric acid are added to the liquid. As a result, for example, when the liquid contains potassium chloropalladium(II) (K ₂ [PdCl ₄ ]) as the first platinum group metal halide, the palladium ions become tetravalent and ammonium chloropalladium(IV) ((NH ₄ ) ₂ [PdCl ₆ ]) precipitates.

The amount of nitric acid to be added is preferably 1 to 500 mol, more preferably 50 to 300 mol, and still more preferably 90 to 250 mol, per 1 mol of the component containing the first platinum group metal contained in the liquid. be. As a result, the oxidation of palladium ions, for example, tends to proceed satisfactorily, and the deposition by the precipitating agent tends to proceed satisfactorily.

The amount of hydrogen chloride added is preferably 1 to 300 mol, more preferably 30 to 250 mol, and still more preferably 80 to 150 mol, per 1 mol of the component containing the first platinum group metal contained in the liquid. is. As a result, the oxidation of palladium ions, for example, tends to proceed satisfactorily, and the deposition by the precipitating agent tends to proceed satisfactorily.

The amount of the precipitating agent added is preferably 0.1 to 20 mol, more preferably 0.5 to 10 mol, and still more preferably 1 mol of the component containing the first platinum group metal contained in the liquid. 1 to 5 mol.

In the step (5b), from the viewpoint of promoting the precipitation, the temperature of the liquid during the precipitation treatment is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The treatment time for the precipitation treatment is preferably 1 hour or longer, more preferably 5 to 100 hours, and still more preferably 10 to 60 hours.

The ammonium salt of chloroplatinic acid and the ammonium salt of chloropalladium are sparingly soluble in water. On the other hand, the ammonium salt of rhodic acid chloride and the ammonium salt of iridic acid chloride are readily soluble in water. Therefore, in the above precipitation process with ammonium chloride, the rhodium and iridium components are contained in the liquid (filtrate). Therefore, even when platinum or palladium coexists with rhodium or iridium, each element can be separated and recovered by using the method of the present disclosure.

In step (5b), subsequently, the precipitated component containing the first platinum group metal is recovered by solid-liquid separation treatment such as filtration treatment and centrifugation treatment. On the other hand, iron (III) chloride and potassium chloride, which are highly soluble in water, can be removed by this solid-liquid separation treatment.

Subsequently, the component containing the first platinum group metal is fired. By such operation, the first platinum group metal can be recovered. The temperature at the time of firing is not particularly limited as long as it is a temperature at which components other than the first platinum group metal can be volatilized or decomposed. ~400°C. The firing time is preferably 0.1 to 20 hours, more preferably 0.3 to 10 hours, still more preferably 0.5 to 5 hours. Examples of the firing atmosphere include an inert gas atmosphere such as argon and nitrogen, and a hydrogen gas atmosphere. When the precipitate is, for example, ammonium chloropalladium(IV)ate ((NH ₄ ) ₂ [PdCl ₆ ]), this calcination yields highly pure palladium.

<Steps (6b) to (8b)>
In step (6b), the solid residue comprising the halide of the second platinum group metal separated in step (4b) is treated with an aqueous solution in which the halide of the second platinum group metal is soluble ( leaching treatment) to obtain an aqueous dispersion. For example, the solid residue is immersed in an aqueous solution.

In step (6b), an aqueous solution in which the halide of the second platinum group metal is soluble is used as the leaching liquid. The aqueous solution includes, for example, an aqueous sodium chloride solution. For example, platinum halides such as potassium chloroplatinate are, in one embodiment, readily soluble in aqueous sodium chloride. Potassium chloroplatinate, which is sparingly soluble in water, is thought to become sodium chloroplatinate, which is readily soluble in water, through ion exchange. Therefore, by putting the solid residue into an aqueous sodium chloride solution, a liquid in which the component containing the second platinum group metal is dissolved can be obtained.

The concentration of sodium chloride in the aqueous sodium chloride solution is preferably 0.1-30 g/100 mL, more preferably 0.5-20 g/100 mL, still more preferably 1-15 g/100 mL. The temperature of the leaching liquid is preferably 95°C or less, more preferably 5 to 80°C, still more preferably 10 to 60°C. The leaching treatment time is preferably 1 hour or more, more preferably 5 to 100 hours, and even more preferably 10 to 60 hours.

On the other hand, impurities that can be generated during the dissolution treatment in step (1b) include, for example, iron oxide produced from iron chloride (III) by oxygen gas mixed in the system. Iron oxide is sparingly soluble in water. Therefore, such impurities can be removed by subjecting the aqueous dispersion to solid-liquid separation treatment in the subsequent step (8b).

In step (7b), a liquid containing a component containing a second platinum group metal is separated from the aqueous dispersion obtained in step (6b) by solid-liquid separation such as filtration and centrifugation. do. The second platinum group metal can be easily recovered from this liquid by a conventionally known method such as a crystallization method. In one embodiment of the present disclosure, a second platinum group metal with high purity can be recovered by performing step (8b) described below.

In step (8b), a precipitant for the second platinum group metal is added to the liquid (eg, filtrate) separated in step (7b) and containing the component containing the second platinum group metal. Thereby, a component containing the second platinum group metal can be deposited.

Precipitating agents include, for example, chlorides of monovalent cations such as ammonium chloride. The precipitating agent may be used alone or in combination of two or more. When ammonium chloride is used, the precipitated second platinum group metal containing component comprises the ammonium component. Therefore, the second platinum group metal of high purity can be obtained by firing the component containing the second platinum group metal.

In one embodiment, when the liquid contains sodium chloroplatinate(IV) as the halide of the second platinum group metal, ammonium chloroplatinate( _IV ) ((NH4) ₂ [ _PtCl6 ]) precipitates. .

The amount of the precipitating agent added is preferably 0.1 to 20 mol, more preferably 0.5 to 10 mol, and still more preferably 1 mol of the second platinum group metal-containing component contained in the liquid. 1 to 5 mol.

In the step (8b), from the viewpoint of promoting the precipitation, the temperature of the liquid during the precipitation treatment is preferably 95°C or less, more preferably 5 to 80°C, and even more preferably 10 to 60°C. The treatment time for the precipitation treatment is preferably 1 hour or longer, more preferably 5 to 100 hours, and still more preferably 10 to 60 hours.

In step (8b), subsequently, the precipitated component containing the second platinum group metal is recovered by solid-liquid separation treatment such as filtration treatment and centrifugation treatment.

Subsequently, the component containing the second platinum group metal is fired. By such operation, the second platinum group metal can be recovered. The temperature at the time of firing is not particularly limited as long as it is a temperature at which components other than the second platinum group metal can be volatilized or decomposed, preferably 300° C. or higher, more preferably 300 to 450° C., still more preferably 300° C. ~400°C. The firing time is preferably 0.1 to 20 hours, more preferably 0.3 to 10 hours, still more preferably 0.5 to 5 hours. Examples of the firing atmosphere include an inert gas atmosphere such as argon and nitrogen, and a hydrogen gas atmosphere. If the precipitate is, for example, ammonium chloroplatinate(IV) ((NH ₄ ) ₂ [PtCl ₆ ]), this calcination yields platinum of high purity.

In one embodiment of the second recovery method, the material may further comprise a third platinum group metal. In this case, the step (1b) is a processed product in which a first platinum group metal halide, a second platinum group metal halide, and a third platinum group metal halide are dissolved in the molten salt. is the process of obtaining For example, the first platinum group metal is palladium, the second platinum group metal is platinum, and the third platinum group metal is rhodium.

Step (3b), in one embodiment, comprises dissolving the solid in which the first platinum group metal halide and the third platinum group metal halide are soluble and the second platinum group metal halide is A process of obtaining an aqueous dispersion by treating with water or an aqueous solution which is hardly soluble may be employed. In one embodiment, step (4b) comprises combining the aqueous dispersion with a liquid comprising a component containing a first platinum group metal and a component containing a third platinum group metal; A step of separating into a solid residue containing a halide may also be used. In step (5b), a precipitating agent for the first platinum group metal is added to the liquid containing the component containing the first platinum group metal and the component containing the third platinum group metal to form the first A precipitate containing a platinum group metal and a liquid containing a component containing a third platinum group metal may be separated.

The present disclosure relates to, for example, the following [1] to [18].
[1] (1a) A substance containing at least one platinum group metal selected from palladium, ruthenium, osmium, iridium and rhodium is brought into contact with a molten salt containing iron halide, and the platinum is dissolved in the molten salt. (2a) cooling the treated material to obtain a solid; (3a) dissolving the solid in water or water in which the platinum group metal halide is soluble; A step of treating with an aqueous solution to obtain an aqueous dispersion, or a step of treating the solid with an organic solvent in which the halide of the platinum group metal is poorly soluble to obtain a dispersion, and (4a) A step of separating a liquid containing a component containing the platinum group metal from the aqueous dispersion, or a step of separating a solid containing a halide of the platinum group metal from the dispersion. collection method.
[2] (5a) The above [ 1].
[3] (5a′-1) A step of treating the solid containing the halide of the platinum group metal with water or an aqueous solution to obtain an aqueous dispersion in which the component containing the platinum group metal is dissolved in water; (5a′-2) separating a liquid containing a component containing the platinum group metal from the aqueous dispersion; and (5a′-3) adding a precipitating agent for the platinum group metal to the liquid. , The method for recovering a platinum group metal according to the above [1], further comprising a step of precipitating a component containing the platinum group metal, and recovering the precipitated component.
[4] The method for recovering a platinum group metal according to any one of [1] to [3] above, wherein the substance contains at least one selected from palladium and rhodium.
[5] The platinum group metal according to any one of [1] to [4], wherein the molten salt is a molten salt of a mixture containing the iron halide and an alkali metal or alkaline earth metal halide. Metal recovery method.
[6] The method for recovering a platinum group metal according to [5] above, wherein the iron halide is iron (III) chloride, and the halide of the alkali metal or alkaline earth metal is potassium chloride.
[7] The method for recovering a platinum group metal according to [2] above, wherein the precipitating agent for the platinum group metal is ammonium chloride.
[8] The method for recovering a platinum group metal according to [3] above, wherein the precipitating agent for the platinum group metal is an alkali metal hydroxide.
[9] (1b) contacting a substance containing a first platinum group metal and a second platinum group metal with a molten salt containing an iron halide, and a halide of the first platinum group metal in the molten salt; (2b) cooling the treated material to obtain a solid; (3b) removing the solid from the first platinum group metal halide (4b) treating the aqueous dispersion with water or an aqueous solution in which the compound is soluble and the halide of the second platinum group metal is sparingly soluble, and (4b) treating the aqueous dispersion with the first 1. A process for recovering platinum group metals, comprising separating into a liquid containing components containing platinum group metals and a solid residue containing halides of a second platinum group metal.
[10] (5b) A precipitating agent for the first platinum group metal is added to the liquid containing the component containing the first platinum group metal to precipitate the component containing the first platinum group metal, and The method for recovering a platinum group metal according to [9] above, further comprising the step of recovering and calcining the components obtained.
[11] (6b) treating the solid residue containing the halide of the second platinum group metal with an aqueous solution in which the halide of the second platinum group metal is soluble to obtain an aqueous dispersion; 7b) separating a liquid containing a component containing a second platinum group metal from the aqueous dispersion; and (8b) adding the second platinum group metal to the liquid containing a component containing a second platinum group metal The platinum group according to [9] or [10] above, further comprising a step of adding a precipitating agent for a metal, precipitating a component containing a second platinum group metal, collecting the precipitated component, and calcining it. Metal recovery method.
[12] The first platinum group metal is at least one selected from platinum, palladium, ruthenium, osmium, iridium and rhodium, and the second platinum group metal is platinum, palladium, ruthenium, osmium, iridium and The method for recovering a platinum group metal according to any one of [9] to [11] above, wherein the metal is at least one selected from rhodium and is different from the first platinum group metal.
[13] The above [9], wherein the substance comprises an alloy containing a first platinum group metal and a second platinum group metal, or an element of the first platinum group metal and an element of the second platinum group metal The method for recovering a platinum group metal according to any one of to [12].
[14] The method for recovering a platinum group metal according to any one of [9] to [13] above, wherein the first platinum group metal is palladium and the second platinum group metal is platinum.
[15] The method for recovering a platinum group metal according to any one of [9] to [14] above, wherein the aqueous solution used in step (3b) is an aqueous potassium chloride solution.
[16] The platinum group metal according to any one of [9] to [15] above, wherein the molten salt is a molten salt of a mixture containing the iron halide and an alkali metal or alkaline earth metal halide. Metal recovery method.
[17] The method for recovering platinum group metals according to [16] above, wherein the iron halide is iron chloride (III), and the halide of the alkali metal or alkaline earth metal is potassium chloride.
[18] The substance further comprises a third platinum group metal, and step (1b) comprises adding a first platinum group metal halide, a second platinum group metal halide and a third platinum group metal halide to the molten salt. The step (3b) is a step of obtaining a treated product in which the platinum group metal halide and the platinum group metal halide are dissolved. soluble and treated with water or an aqueous solution in which the halide of the second platinum group metal is sparingly soluble to obtain an aqueous dispersion, and step (4b) is the step of treating the aqueous dispersion with the first separating into a liquid containing a component containing a platinum group metal and a component containing a third platinum group metal, and a solid residue containing a halide of the second platinum group metal, wherein in step (5b) adding a precipitating agent for the first platinum group metal to a liquid containing a component containing a first platinum group metal and a component containing a third platinum group metal to contain the first platinum group metal The method for recovering a platinum group metal according to the above [10], wherein the precipitate is separated into the precipitate and the liquid containing the component containing the third platinum group metal.

Hereinafter, the method for recovering platinum group metals of the present disclosure will be described in more detail based on examples.
FIG. 2 shows an outline of the flow of the first embodiment.
FIG. 3 shows an outline of the flow of the second embodiment.
FIG. 8 shows an outline of the flow of Examples 4 and 5. FIG.

[Example 1] Treatment of palladium wire Equimolar amounts of iron (III) chloride and potassium chloride were mixed to obtain 3.0 g of a mixture (hereinafter also referred to as "mixture (A)"). A palladium wire having a diameter of 0.2 mm, a length of about 100 mm, and a weight of about 40 mg was used as a sample.

The mixture (A) and the sample are placed in a porcelain crucible (SiO ₂ : 58% or more, Al ₂ O ₃ : 33% or more), the porcelain crucible is set in a glass reaction tube, and the inside of the reaction tube is filled with argon (Ar ), the reaction tube was heated using a mantle heater (Oka Denki Co., Ltd., GBR-5) as a heating device. The reaction was started when the thermocouple set near the porcelain crucible reached 250° C. (523 K). Dissolution treatment was carried out at a treatment temperature of 287° C. (560 K) to 327° C. (600 K) and a treatment time of 1, 2 or 3 hours.

After completion of the melting treatment, the reaction tube was removed from the mantle heater, and the contents in the porcelain crucible were solidified by air cooling. The collected contents were put into a leaching liquid (20 mL of pure water) and subjected to leaching treatment. When the mixture (A) was dissolved in the leaching liquid, the sample residue (palladium wire residue) was recovered, and the weight change of the sample was measured to determine the amount of dissolved sample. Since there was a range in the weight of the charged sample, the amount of dissolved palladium wire was converted using the following formula (i), and the obtained results were compared.

w = w _dissolution × (40/w _sample ) (i)
w _dissolution indicates the actual dissolution amount of the sample, and w _sample indicates the weight of the actually charged sample.

Thereafter, iron oxide was separated and removed by filtration, 12M hydrochloric acid (HCl aqueous solution) was added to the filtrate, and after standing at 40°C for 24 hours, ammonium chloride and 13.5M nitric acid aqueous solution were added. , and allowed to stand at 40° C. for 24 hours. See Table 2 for the amount of hydrochloric acid, aqueous nitric acid solution and ammonium chloride added. This gave a dark red precipitate. The resulting precipitate was placed in a porcelain crucible, the porcelain crucible was set in a glass reaction tube (argon (Ar) atmosphere), and heated at 377°C (650K) using the same heating apparatus as described above. Heated for 1 hour. This gave a black powder (final collection).

FIG. 4 shows changes in the amount of sample (palladium) dissolved when the treatment time and treatment temperature in the dissolution treatment were changed. It was confirmed that the dissolution amount of the sample tends to increase as the treatment time is extended and the treatment temperature is raised.

In the dissolution treatment with a treatment time of 1 hour, the initial dissolution rate was evaluated from the surface area of the sample at the time of introduction. The initial dissolution rate of palladium was 1.72 mol·m ⁻² ·h ⁻¹ at 297° C. (570 K). From Non-Patent Document 1 (Journal of the Japan Institute of Metals, Vol. 83, No. 1 (2019) 23-29), the initial dissolution rate of platinum using the molten salt of the mixture (A) is 0.45 mol at 382 ° C. (655 K). ·m ⁻² ·h ⁻¹ , indicating that palladium dissolves faster and at a lower temperature in the molten salt of mixture (A) compared to platinum.

Composition analysis by SEM-EDS (JEOL Ltd., JSM-6010-LA) targeting chlorine (Cl), potassium (K), iron (Fe) and palladium (Pd) for precipitates and final recovered materials did Dissolution treatment: Table 1 shows the analysis results of the example at 327°C for 3 hours.

SEM-EDS analysis of the precipitate showed almost no iron detected and the molar ratio of palladium to chlorine (Cl:Pd) was close to 6:1. It is believed that ((NH ₄ ) ₂ PdCl ₆ ) precipitated. From the results of SEM-EDS analysis of the final recovered product, it is considered that contamination with iron and the like was suppressed, and palladium with a purity of 90% or higher was recovered. The recovered palladium exhibited a porous morphology.

The amount of palladium in the final recovered product was estimated from the weight and composition of the final recovered product, and the recovery rate was evaluated by comparing with the dissolved amount. In addition, the recovery rate was evaluated without applying the conversion shown in the above formula (i). Table 2 (dissolution treatment: 327° C., 3 hours example) shows the recovery of palladium obtained when the deposition conditions were varied.

[Example 2] Platinum-palladium alloy wire In Example 2, the sample was a platinum-palladium alloy with a diameter of 0.2 mm, a length of about 100 mm, a weight of about 60 mg, and a weight ratio of 80% platinum to 20% palladium. The dissolution treatment was carried out in the same manner as in Example 1 except that a wire was used, the treatment temperature was 377° C. (650 K), and the treatment time was 1, 2, 3, 6 or 8 hours. Since the weight of the charged sample varied, the dissolution amount of the platinum-palladium alloy wire was converted according to the following formula (ii), and the obtained results were compared.

w = w _dissolution × (60/w _sample ) (ii)
w _dissolution indicates the actual dissolution amount of the sample, and w _sample indicates the weight of the actually charged sample.

FIG. 5 shows changes in the amount of dissolution of the sample (platinum-palladium alloy) when the treatment time in the dissolution treatment was changed. It was confirmed that when the treatment time was up to 3 hours, the dissolution amount of the sample increased as the treatment time was extended, and thereafter the increase in the dissolution amount of the sample slowed down. The sample dissolution amount when the treatment time was 3 hours was 17.8 mg.

The contents collected in the same manner as in Example 1 were leached with an aqueous potassium chloride solution obtained by adding 2.0 g of potassium chloride to 20 mL of pure water, and allowed to stand at 40° C. for 24 hours. Filtration then yielded a solid residue (1) and a filtrate (2).

Solid residue (1) thought to contain a platinum component was leached with an aqueous sodium chloride solution obtained by adding 4.0 g of sodium chloride to 40 mL of pure water, and allowed to stand at 40° C. for 24 hours. A solid residue at that time was separated and removed by filtration, 8.0 mg of ammonium chloride was added to the filtrate, and the mixture was allowed to stand at 40° C. for 24 hours to obtain a bright yellow precipitate. The resulting precipitate was placed in a porcelain crucible, the porcelain crucible was set in a glass reaction tube (argon (Ar) atmosphere), and heated at 377°C (650K) using the same heating apparatus as described above. Heated for 1 hour. This gave a dark gray powder (final collection).

Regarding the precipitate and the final collected material, composition analysis was performed by the above SEM-EDS targeting sodium (Na), chlorine (Cl), potassium (K), iron (Fe), palladium (Pd) and platinum (Pt). rice field. Dissolution treatment: Table 3 shows the analysis results of the example at 377°C for 8 hours.

The precipitate is considered to be platinum chloride from the color of the precipitate and the analysis results by SEM-EDS. From the results of analysis by SEM-EDS, the final recovered product is considered to be highly pure platinum. Due to the large molar ratio of platinum to palladium in the composition of the precipitate, it was found that the recovery method of the present disclosure can be applied to a process for separating and recovering platinum and palladium from a platinum-palladium alloy.

3.0 mL of 12 M hydrochloric acid (HCl aqueous solution) was added to the filtrate (2), which was considered to contain a palladium component, and after standing at 40° C. for 24 hours, 6.0 mg of ammonium chloride and 13.5 M 3.0 mL of an aqueous nitric acid solution was added, and the mixture was allowed to stand at 40° C. for 24 hours. This gave a dark gray precipitate. The resulting precipitate was placed in a porcelain crucible, the porcelain crucible was set in a glass reaction tube (argon (Ar) atmosphere), and heated at 377°C (650K) using the same heating apparatus as described above. Heated for 1 hour. This gave a black powder (final collection).

Regarding the precipitate and the final collected material, composition analysis was performed by the above SEM-EDS targeting sodium (Na), chlorine (Cl), potassium (K), iron (Fe), palladium (Pd) and platinum (Pt). rice field. Dissolution treatment: Table 4 shows the analysis results of the example at 377°C for 8 hours.

The precipitate is considered to be palladium chloride from the color of the precipitate and the results of analysis by SEM-EDS. From the results of analysis by SEM-EDS, the final recovered product contained potassium compounds and chlorides in addition to simple palladium. However, since contamination of palladium into the platinum side and contamination of platinum into the palladium side was suppressed, it was confirmed that platinum and palladium could be separated in both the precipitate and the final recovered material. Iron contamination is also suppressed. Therefore, it became clear that the recovery method of the present disclosure is applicable to a process of separating and recovering platinum and palladium from a platinum-palladium alloy.
Table 5 shows the final platinum and palladium recovery amounts.

[Example 3] Platinum wire and palladium wire In Example 3, a platinum wire of φ = 0.2 mm, length: about 50 mm, weight: about 35 mg, φ = 0.2 mm, length: about 90 mm was used as a sample. , weight: about 35 mg of palladium wire, the treatment temperature was 327° C. (600 K) or 377° C. (650 K), and the treatment time was 1, 2, 3, 6, or 8 hours. The dissolution treatment was performed in the same manner as above. Since there was a range in the weight of the charged sample, the amounts of dissolved platinum wire and palladium wire were converted according to the following formula (iii), and the obtained results were compared.

w = w _dissolution × (35/w _sample ) (iii)
w _dissolution indicates the actual dissolution amount of the sample, and w _sample indicates the weight of the actually charged sample.

Subsequent operations were performed in the same manner as in Example 2.
The treatment temperature in the dissolution treatment was set to 327° C. (600 K) and 377° C. (650 K), and the change in the amount of dissolution of the sample (platinum and palladium) when the treatment time was changed is shown in FIG. 6 (327° C.) and FIG. (377°C). It was confirmed that the dissolution amount of the sample tends to increase as the treatment time is extended and the treatment temperature is raised.

Regarding the precipitates and final recovery on the solid residue (1) side, the above SEM was used for sodium (Na), chlorine (Cl), potassium (K), iron (Fe), palladium (Pd) and platinum (Pt). - Compositional analysis by EDS was performed. Dissolution treatment: Table 6 shows the analysis results of the example at 377°C for 8 hours.

The precipitate is considered to be platinum chloride from the color of the precipitate and the analysis results by SEM-EDS. From the results of analysis by SEM-EDS, the final recovered product is considered to be highly pure platinum. Since the molar ratio of platinum to palladium in the composition of the deposit is large, it was clarified that the recovery method of the present disclosure can be applied to the process of separating and recovering platinum and palladium in the simultaneous dissolution treatment of the platinum wire and the palladium wire. .

Regarding the precipitates and the final collected material on the side of the filtrate (2), the above SEM- A composition analysis was performed by EDS. Dissolution treatment: Table 7 shows the analysis results of the example at 377°C for 8 hours.

The precipitate is considered to be palladium chloride from the color of the precipitate and the results of analysis by SEM-EDS. From the results of analysis by SEM-EDS, the final recovered product contained potassium compounds and chlorides in addition to simple palladium. However, since contamination of palladium into the platinum side and contamination of platinum into the palladium side was suppressed, it was confirmed that platinum and palladium could be separated in both the precipitate and the final recovered material. Iron contamination is also suppressed. Therefore, it has been clarified that the recovery method of the present disclosure can be applied to the process of separating and recovering platinum and palladium in simultaneous dissolution treatment of platinum wire and palladium wire.

Table 8 shows the final platinum and palladium recovery amounts and recovery rates.

In the simultaneous treatment experiment, the amount of platinum and palladium in the recovered material was estimated from the recovered weight and the result of composition analysis by SEM-EDS, and the recovery rate was evaluated by comparing with the dissolved amount. The recovery amount and recovery rate were evaluated without applying the conversion shown in the above formula (iii).

[Example 4] Rhodium wire In Example 4, a rhodium wire of φ = 0.25 mm, length: about 50 mm, weight: about 30 mg was used as a sample, and the treatment temperature was 317 ° C. (590 K), 337 ° C. (610 K). ), 377° C. (650 K) or 397° C. (670 K), and the dissolution treatment was performed in the same manner as in Example 1 except that the treatment time was 2, 3, 6 or 8 hours. It was confirmed that the sample (rhodium) could be dissolved by the dissolution treatment.

In the dissolution treatment with a treatment time of 2 hours, the initial dissolution rate was evaluated from the surface area of the sample at the time of introduction. The initial dissolution rate of rhodium was 1.67 mol·m ⁻² ·h ⁻¹ at 377° C. (650 K).

(1) The contents collected in the same manner as in Example 1 were leached with an aqueous sodium nitrite solution obtained by adding 2.0 g of sodium nitrite (NaNO ₂ ) to 40 mL of pure water. After that, the sample residue and iron oxide were separated and removed by filtration, and 2.0 mg of ammonium chloride was added to the filtrate, which was allowed to stand at 40° C. for 24 hours. This gave a yellow precipitate.

(2) The contents collected in the same manner as in Example 1 were put into a leaching solution (20 mL of ethanol) for leaching treatment, and allowed to stand at 40° C. for 24 hours. After that, a solid residue (1) (approximately 2 g) and a filtrate (2) were obtained by filtration.

The solid residue (1) was leached with an aqueous potassium sulfate solution obtained by adding 0.5 g of potassium sulfate to 20 mL of pure water, and allowed to stand at 40° C. for 24 hours. The solid residue at that time was separated and removed by filtration, and 1 g of sodium hydroxide was added to the filtrate (red solution peculiar to rhodium salt; considered to be an aqueous solution of rhodium sulfate), and allowed to stand at 40 ° C. for 24 hours. , a black precipitate was obtained. When the precipitate was subjected to composition analysis by the above SEM-EDS, Rh and O were mainly detected (see Table 9). Dissolution treatment: According to the analysis results of the example at 397° C. for 8 hours, the Rh recovery rate was about 36% (sample dissolution amount: 23.6 mg, recovery amount: 8.48 mg).

SEM-EDS analysis of the precipitate did not detect a large amount of iron, suggesting that Rh(OH) ₃ or Rh ₂ O ₃ was precipitated by the precipitation treatment. From the results of SEM-EDS analysis, it is considered that the contamination of iron and the like was greatly suppressed.

[Example 5] Iridium wire In Example 5, an iridium wire having a diameter of 0.25 mm, a length of about 50 mm, and a weight of about 50 mg was used as a sample, and 6.0 g of the mixture (A) was used. The dissolution treatment was performed in the same manner as in Example 1, except that the temperature was 377° C. (650 K) or 397° C. (670 K) and the treatment time was 4 or 8 hours. It was confirmed that the sample (iridium) could be dissolved by the dissolution treatment.

In the dissolution treatment with a treatment time of 4 hours, the initial dissolution rate was evaluated from the surface area of the sample at the time of introduction. The initial dissolution rate of iridium was 0.27 mol·m ⁻² ·h ⁻¹ at 397° C. (670 K).

The contents collected in the same manner as in Example 1 were put into a leaching solution (20 mL of ethanol), subjected to leaching treatment, and allowed to stand at 40° C. for 24 hours. After that, a solid residue (1) (approximately 2 g) and a filtrate (2) were obtained by filtration.

Claims (18)

(1a) contacting a substance containing at least one platinum group metal selected from palladium, ruthenium, osmium, iridium and rhodium with a molten salt containing iron halide, and obtaining a processed product in which the halide is dissolved;
(2a) cooling the treated material to obtain a solid;
(3a) treating the solid with water or an aqueous solution in which the platinum group metal halide is soluble to obtain an aqueous dispersion; and (4a) separating a liquid containing a component containing the platinum group metal from the aqueous dispersion, or from the dispersion, A method for recovering a platinum group metal, comprising separating a solid containing a halide of the platinum group metal. (5a) The step of adding a precipitating agent for the platinum group metal to the liquid to precipitate a component containing the platinum group metal, recovering the precipitated component, and calcining the precipitated component. of platinum group metals. (5a'-1) a step of treating the solid containing the halide of the platinum group metal with water or an aqueous solution to obtain an aqueous dispersion in which the component containing the platinum group metal is dissolved in water;
(5a'-2) from the aqueous dispersion,
(5a′-3) adding a precipitating agent for the platinum group metal to the liquid to precipitate the component containing the platinum group metal; 2. A method for recovering platinum group metals according to claim 1, further comprising the step of recovering the precipitated components. The method for recovering platinum group metals according to any one of claims 1 to 3, wherein the substance contains at least one selected from palladium and rhodium. The method for recovering platinum group metals according to any one of claims 1 to 4, wherein the molten salt is a molten salt of a mixture containing the iron halide and an alkali metal or alkaline earth metal halide. . The iron halide is iron chloride (III),
wherein the alkali metal or alkaline earth metal halide is potassium chloride;
The method for recovering platinum group metals according to claim 5. 3. The method for recovering platinum group metals according to claim 2, wherein the precipitating agent for platinum group metals is ammonium chloride. 4. The method for recovering platinum group metals according to claim 3, wherein the precipitating agent for platinum group metals is an alkali metal hydroxide. (1b) bringing a substance containing a first platinum group metal and a second platinum group metal into contact with a molten salt containing an iron halide; obtaining a processed product in which the halide of the second platinum group metal is dissolved;
(2b) cooling the treated material to obtain a solid;
(3b) treating the solid with water or an aqueous solution in which the first platinum group metal halide is soluble and the second platinum group metal halide is sparingly soluble, and forming an aqueous dispersion; and (4b) separating the aqueous dispersion into a liquid comprising a component containing the first platinum group metal and a solid residue comprising a halide of the second platinum group metal. A method for recovering platinum group metals, comprising: (5b) adding a precipitating agent for the first platinum group metal to the liquid containing the component containing the first platinum group metal to precipitate the component containing the first platinum group metal; 10. The method of recovering platinum group metals of claim 9, further comprising recovering and calcining the components. (6b) treating the solid residue containing the halide of the second platinum group metal with an aqueous solution in which the halide of the second platinum group metal is soluble to obtain an aqueous dispersion;
(7b) from the aqueous dispersion,
(8b) separating the liquid containing the component containing the second platinum group metal; and (8b) adding a deposition agent for the second platinum group metal to the liquid containing the component containing the second platinum group metal. 11. The method for recovering a platinum group metal according to claim 9 or 10, further comprising the steps of: adding a component containing the second platinum group metal, precipitating the component containing the second platinum group metal, collecting the precipitated component, and calcining it. The first platinum group metal is at least one selected from platinum, palladium, ruthenium, osmium, iridium and rhodium, and the second platinum group metal is platinum, palladium, ruthenium, osmium, iridium and rhodium. The method for recovering a platinum group metal according to any one of claims 9 to 11, wherein the metal is at least one selected from and is different from the first platinum group metal. the substance is
An alloy containing a first platinum group metal and a second platinum group metal, or an elemental first platinum group metal and an elemental second platinum group metal, according to any one of claims 9 to 12 A method for recovering the platinum group metals described. the first platinum group metal is palladium,
wherein the second platinum group metal is platinum;
The method for recovering platinum group metals according to any one of claims 9 to 13. The method for recovering platinum group metals according to any one of claims 9 to 14, wherein the aqueous solution used in step (3b) is an aqueous potassium chloride solution. The method for recovering platinum group metals according to any one of claims 9 to 15, wherein the molten salt is a molten salt of a mixture containing the iron halide and an alkali metal or alkaline earth metal halide. . The iron halide is iron chloride (III),
wherein the alkali metal or alkaline earth metal halide is potassium chloride;
17. The method for recovering platinum group metals according to claim 16. said material further comprising a third platinum group metal;
The processed material in which the step (1b) is performed by dissolving the first platinum group metal halide, the second platinum group metal halide, and the third platinum group metal halide in the molten salt. is a step of obtaining
The step (3b) is performed by converting the solid into a solid in which the first platinum group metal halide and the third platinum group metal halide are soluble and the second platinum group metal halide is difficult to dissolve. A step of treating with water or an aqueous solution to obtain an aqueous dispersion,
The step (4b) comprises combining the aqueous dispersion with a liquid containing a component containing the first platinum group metal and a component containing the third platinum group metal, and a halogen of the second platinum group metal. A step of separating into a solid residue containing a compound,
In the step (5b), a precipitating agent for the first platinum group metal is added to the liquid containing the component containing the first platinum group metal and the component containing the third platinum group metal. separating into a precipitate containing said first platinum group metal and a liquid containing a component containing said third platinum group metal;
11. The method for recovering platinum group metals according to claim 10.

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