WO2019188708A1 - Method for recovering platinum group element - Google Patents

Abstract

Provided is a method for recovering a platinum group element from a water-soluble polymer on which a platinum group element is adsorbed, wherein the method is provided with a preparation step for preparing a hydrochloric acid aqueous solution containing 0.25-31.50 wt% of hydrochloric acid, and a mixing step for mixing the hydrochloric acid aqueous solution prepared in the preparation step and a water-soluble polymer on which the platinum group element is adsorbed for 1.5 hours or longer in the presence of thiourea, mixing being performed with the content ratio of the thiourea in the mixture in the mixing step being 0.5-20.0 wt% and the content ratio of the water-soluble polymer on which the metal group element is adsorbed being 16-72 wt%.

Description

Method for recovering platinum group elements

The present invention relates to a method for recovering a platinum group element from a water-soluble polymer adsorbed with the platinum group element.

Nitrile rubber (acrylonitrile-butadiene copolymer rubber) has been used as a material for automotive rubber parts such as hoses and tubes, taking advantage of its oil resistance, mechanical properties, chemical resistance, etc. Hydrogenated nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) in which carbon-carbon double bonds in the polymer main chain of rubber are hydrogenated is further excellent in heat resistance, so it is used for rubber parts such as belts, hoses, and diaphragms. Has been.

Such hydrogenated nitrile rubber is manufactured, for example, by the following manufacturing process. That is, an α, β-ethylenically unsaturated nitrile monomer or a monomer mixture containing a conjugated diene monomer is emulsion-polymerized, and a nitrile rubber latex obtained by emulsion polymerization is coagulated and dried, and then coagulated. -By dissolving the nitrile rubber obtained by drying in a water-soluble organic solvent, a water-soluble organic solvent solution of nitrile rubber is obtained, and a platinum group element-containing catalyst as a hydrogenation catalyst is added to this to hydrogenate It is manufactured by.

On the other hand, the hydrogenated nitrile rubber produced by such a production method uses a platinum group element-containing catalyst as a hydrogenation catalyst, and the platinum group element contained in such a platinum group element-containing catalyst is Since it is expensive, its collection and reuse are desired.

As a technique for recovering such a platinum group element, for example, in Patent Document 1 and Patent Document 2, cellulose formed by binding an acetylated chitosan derivative, iminodiacetic acid or dialkylamine is used as an adsorbent. A method of recovering a platinum group element by detaching the platinum group element from the agent has been proposed.

JP 2009-247981 A JP 2010-179208 A

However, in the techniques of Patent Documents 1 and 2, as is clear from the disclosure of the examples, the technique (adsorbent) is based on the premise that the platinum group element contained in the hydrochloric acid aqueous solution is adsorbed by the adsorbent. In the techniques of Patent Documents 1 and 2, the platinum group element is desorbed from the adsorbent, and then the adsorbent is used. In the case of Patent Document 1, the adsorption efficiency of the platinum group element is reduced (for example, in Patent Document 1, the adsorption efficiency after reuse is about 70%, and in Patent Document 2, the adsorption efficiency after reuse is about 95%. ). Furthermore, in the techniques of the above Patent Documents 1 and 2, there is no description about the recovery efficiency of the adsorbent itself from which the platinum group element has been desorbed. No knowledge has been shown about improving the recovery efficiency.

The present invention has been made in view of such a situation, and from a water-soluble polymer adsorbed with a platinum group element, the platinum group element can be recovered at a high recovery rate, and after the platinum group element is recovered It is an object of the present invention to provide a method for recovering a platinum group element that can be suitably reused for the purpose of adsorbing the platinum group element.

When recovering the platinum group element from the water-soluble polymer adsorbed with the platinum group element, the present inventors prepared an aqueous hydrochloric acid solution having a predetermined concentration in advance, and the aqueous hydrochloric acid solution and the platinum group element were adsorbed. Mixing the water-soluble polymer with the thiourea for a predetermined time, and further determining the content ratio of the thiourea and the content ratio of the water-soluble polymer adsorbed with the platinum group element in the mixed solution. The inventors have found that the above object can be achieved by setting the specific range, and have completed the present invention.

That is, according to the present invention, there is provided a method for recovering a platinum group element from a water-soluble polymer adsorbed with a platinum group element, comprising preparing an aqueous hydrochloric acid solution containing 0.25 to 31.50 wt% hydrochloric acid. A mixing step of mixing the aqueous hydrochloric acid solution prepared in the preparation step and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea for 1.5 hours or more, the mixing step The platinum group element in which mixing is performed with the content ratio of the thiourea being 0.5 to 20.0 wt% and the content ratio of the water-soluble polymer adsorbed with the platinum group element being 16 to 72 wt% A recovery method is provided.

In the platinum group element recovery method of the present invention, the content ratio of the hydrochloric acid in the mixed solution in the mixing step is preferably 1.0 to 16.0% by weight.
In the platinum group element recovery method of the present invention, the water-soluble polymer is preferably an amino group-containing (meth) acrylate polymer.
In the platinum group element recovery method of the present invention, the amino group-containing (meth) acrylate polymer is a homopolymer of N, N-dimethylaminoethyl methacrylate (DMAEMA) or N, N-dimethylaminoethyl methacrylate. It is preferably a copolymer of two or more monomers including (DMAEMA).
In the platinum group element recovery method of the present invention, the platinum group element is preferably palladium.
In the platinum group element recovery method of the present invention, the platinum group element is preferably a platinum group element derived from the platinum group element-containing catalyst used in the hydrogenation reaction of the nitrile rubber.
In the platinum group element recovery method of the present invention, after the mixing step obtains a hydrochloric acid aqueous solution containing thiourea by previously mixing the hydrochloric acid aqueous solution prepared in the preparation step and the thiourea. It is preferable to add and mix the water-soluble polymer adsorbed with the platinum group element into the aqueous hydrochloric acid solution containing the thiourea.
In the platinum group element recovery method of the present invention, the content of the thiourea in the aqueous hydrochloric acid solution containing the thiourea is preferably 1.0 to 35.0% by weight.
In the platinum group element recovery method of the present invention, in the mixing step, when the water-soluble polymer adsorbed with the platinum group element is added to the hydrochloric acid aqueous solution prepared in the preparation step, the platinum group element is It is preferable to add the adsorbed water-soluble polymer in a solid state.

According to the present invention, a platinum group element can be recovered at a high recovery rate from a water-soluble polymer on which the platinum group element is adsorbed, and the platinum group element is adsorbed on the water-soluble polymer after the platinum group element is recovered. It is possible to provide a method for recovering a platinum group element that can be suitably reused for the intended use.

The platinum group element recovery method of the present invention includes:
A method of recovering a platinum group element from a water-soluble polymer adsorbed with a platinum group element,
A preparation step of preparing an aqueous hydrochloric acid solution containing 0.25 to 31.50 wt% hydrochloric acid;
A mixing step of mixing the hydrochloric acid aqueous solution prepared in the preparation step and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea for 1.5 hours or more,
Mixing is performed with the content ratio of the thiourea in the mixed solution in the mixing step being 0.5 to 20.0 wt% and the content ratio of the water-soluble polymer adsorbed with the platinum group element being 16 to 72 wt%. Is.

<Platinum group element>
First, the platinum group element which is the object of recovery in the recovery method of the present invention will be described.
In the recovery method of the present invention, the platinum group element to be recovered is not particularly limited, but hydrogenation is performed by hydrogenating a carbon-carbon double bond contained in a conjugated diene rubber such as nitrile rubber. Examples thereof include platinum group elements derived from platinum group element-containing catalysts, which are used in obtaining hydrogenated conjugated diene rubbers such as nitrile rubber. As an example of the hydrogenation reaction of such a conjugated diene rubber, the hydrogenation reaction of a nitrile rubber will be exemplified and described below.

Examples of the nitrile rubber include a copolymer obtained by copolymerizing a monomer mixture containing at least an α, β-ethylenically unsaturated nitrile monomer and a conjugated diene monomer. The α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile, etc. Α-halogenoacrylonitrile, α-alkylacrylonitrile such as methacrylonitrile, and the like. Conjugated diene monomers include conjugated diene monomers having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, chloroprene and the like. Is mentioned.

The content of the α, β-ethylenically unsaturated nitrile monomer unit in the nitrile rubber is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, more preferably based on the total monomer units. Preferably, it is 15 to 50% by weight. In addition, the content of the conjugated diene monomer unit (including a portion hydrogenated by a hydrogenation reaction) in the nitrile rubber is preferably 40 to 95% by weight based on the total monomer units, More preferred is 50 to 90% by weight, still more preferred is 50 to 85% by weight.

In addition to the α, β-ethylenically unsaturated nitrile monomer and the conjugated diene monomer, the nitrile rubber may be a copolymer of other monomers copolymerizable therewith, Examples of other copolymerizable monomers include α, β-ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; α, β-ethylenically unsaturated polyvalent carboxylic acid monomers Α, β-ethylenically unsaturated monocarboxylic acid ester monomers such as methyl acrylate, ethyl acrylate and n-butyl acrylate; α such as mono n-butyl maleate and mono n-butyl fumarate , Β-ethylenically unsaturated dicarboxylic acid monoester monomer; ethylene; α-olefin monomer, aromatic vinyl monomer; fluorine-containing vinyl monomer; copolymerizable anti-aging agent;

The hydrogenation reaction of nitrile rubber is usually performed using a platinum group element-containing catalyst. The hydrogenation reaction of nitrile rubber can be performed in the latex state with respect to the nitrile rubber latex obtained by emulsion polymerization, or the nitrile rubber latex obtained by emulsion polymerization is solidified by solidification and drying. This nitrile rubber can be obtained, and the obtained nitrile rubber can be dissolved in a water-soluble organic solvent and carried out in the state of a polymer solution. Among these, it is preferable to carry out in the state of a polymer solution by dissolving the obtained nitrile rubber in a water-soluble organic solvent from the viewpoint of catalytic activity and the like.

Coagulation / drying of the nitrile rubber latex may be carried out by a known method, but by providing a treatment step for bringing the crumb obtained by coagulation into contact with a basic aqueous solution, the resulting nitrile rubber is added to tetrahydrofuran (THF). It is preferable to modify so that the pH of the polymer solution measured by dissolution exceeds 7. The pH of the polymer solution measured by dissolving in THF is preferably in the range of 7.2 to 12, more preferably 7.5 to 11.5, and most preferably 8 to 11. By this contact treatment between the crumb and the basic aqueous solution, the solution-based hydrogenation can be rapidly advanced.

The concentration of the nitrile rubber in the polymer solution during the hydrogenation reaction is preferably 1 to 70% by weight, more preferably 1 to 40% by weight, and particularly preferably 2 to 20% by weight. Examples of the water-soluble organic solvent include ketones such as acetone, methyl ethyl ketone, diethyl ketone, and methyl isopropyl ketone; ethers such as tetrahydrofuran and dioxane; esters such as ethyl acetate; Among these organic solvents, ketones are preferably used, and acetone is particularly preferably used.

When performing the hydrogenation reaction, a platinum group element-containing catalyst is used as the hydrogenation catalyst. The platinum group element-containing catalyst is not particularly limited as long as it is a catalyst containing a platinum group element, that is, ruthenium, rhodium, palladium, osmium, iridium, or platinum, but from the viewpoint of catalytic activity and availability, a palladium compound. A rhodium compound is preferable, and a palladium compound is more preferable. Two or more platinum group element compounds may be used in combination, but in this case as well, it is preferable to use a palladium compound as the main catalyst component.

As the palladium compound, a II-valent or IV-valent palladium compound is usually used, and the form thereof is a salt or a complex salt.

Examples of the palladium compound include palladium acetate, palladium cyanide, palladium fluoride, palladium chloride, palladium bromide, palladium iodide, palladium nitrate, palladium sulfate, palladium oxide, palladium hydroxide, dichloro (cyclooctadiene) palladium, Examples include dichloro (norbornadiene) palladium, dichlorobis (triphenylphosphine) palladium, sodium tetrachloropalladate, ammonium hexachloropalladate, and potassium tetracyanopalladate.

Among these palladium compounds, palladium acetate, palladium nitrate, palladium sulfate, palladium chloride, sodium tetrachloropalladate, and ammonium hexachloropalladate are preferable, and palladium acetate, palladium nitrate, and palladium chloride are more preferable.

Examples of rhodium compounds include rhodium chloride, rhodium bromide, rhodium iodide, rhodium nitrate, rhodium sulfate, rhodium acetate, rhodium formate, rhodium propionate, rhodium butyrate, rhodium valerate, rhodium naphthenate, rhodium acetylacetonate, oxide Examples thereof include rhodium and rhodium trihydroxide.

As the platinum group element-containing catalyst, the above-described palladium compound or rhodium compound may be used as it is, or a catalyst component such as the above-described palladium compound or rhodium compound is supported on a carrier and used as a supported catalyst. May be.

The carrier for forming the supported catalyst may be any carrier that is generally used as a carrier for metal catalysts. Specifically, inorganic compounds containing carbon, silicon, aluminum, magnesium, etc. may be used. Among them, from the viewpoint of increasing the adsorption efficiency of catalyst components such as palladium compounds and rhodium compounds, the characteristics of the carrier are those having an average particle diameter of 1 μm to 200 μm and a specific surface area of 200 to 2000 m ² / g. It is preferred to use.

Such a carrier is appropriately selected from known catalyst carriers such as activated carbon, activated clay, talc, clay, alumina gel, silica, diatomaceous earth, and synthetic zeolite. Examples of the method for supporting the catalyst component on the carrier include an impregnation method, a coating method, a spray method, and a precipitation method. The supported amount of the catalyst component is usually 0.5 to 80% by weight, preferably 1 to 50% by weight, more preferably 2 to 30% by weight as a ratio of the catalyst component to the total amount of the catalyst and the carrier. The carrier carrying the catalyst component can be formed into, for example, a spherical shape, a cylindrical shape, a polygonal column shape, a honeycomb shape, or the like according to the type of reactor or the reaction mode.

In addition, when a platinum group element salt such as a palladium compound or a rhodium compound is not supported on a carrier and is used as it is as a platinum group element-containing catalyst, a stabilizer for stabilizing these compounds should be used in combination. Is preferred. By allowing the stabilizer to exist in a medium in which a platinum group element-containing catalyst such as a palladium compound or rhodium compound is dissolved or dispersed, the nitrile rubber can be hydrogenated at a high hydrogenation rate.

Examples of such stabilizers include polymers of vinyl compounds having a polar group in the side chain such as polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl acetal, and polyalkyl vinyl ether; sodium polyacrylate, potassium polyacrylate, and the like. Polyacrylic acid metal salts; polyethers such as polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide copolymer; cellulose derivatives such as carboxymethyl cellulose and hydroxypropyl cellulose; natural polymers such as gelatin and albumin; . Among these, a polymer of a vinyl compound having a polar group in the side chain, or a polyether is preferable. Among the polymers of vinyl compounds having a polar group in the side chain, polyvinyl pyrrolidone and polyalkyl vinyl ether are preferable, and polymethyl vinyl ether is more preferable.

In the hydrogenation reaction, a reducing agent may be used in combination. Examples of the reducing agent include hydrazines such as hydrazine, hydrazine hydrate, hydrazine acetate, hydrazine sulfate, and hydrazine hydrochloride, or compounds that liberate hydrazine. Etc.

The temperature of the hydrogenation reaction is usually 0 to 200 ° C., preferably 5 to 150 ° C., more preferably 10 to 100 ° C. By setting the temperature of the hydrogenation reaction within the above range, the reaction rate can be sufficient while suppressing side reactions.

The hydrogen pressure during the hydrogenation reaction is usually 0.1 to 20 MPa, preferably 0.1 to 15 MPa, more preferably 0.1 to 10 MPa. The reaction time is not particularly limited, but is usually 30 minutes to 50 hours. The hydrogen gas is preferably pressurized after first substituting the reaction system with an inert gas such as nitrogen and further substituting with hydrogen.

When a supported catalyst is used as the platinum group element-containing catalyst, a water-soluble organic solvent solution of hydrogenated nitrile rubber can be obtained by separating the supported catalyst by filtration, centrifugation, or the like.

<Water-soluble polymer with platinum group elements adsorbed>
Subsequently, the water-soluble polymer which the platinum group element adsorb | sucked used in the collection | recovery method of this invention is demonstrated.
The water-soluble polymer adsorbed with the platinum group element used in the recovery method of the present invention is not particularly limited. For example, when the nitrile rubber is hydrogenated using the above platinum group element-containing catalyst. A platinum group element derived from a platinum group element-containing catalyst is adsorbed on a water-soluble polymer for recovery and reuse from a water-soluble organic solvent solution of hydrogenated nitrile rubber obtained in Can be mentioned.

As a specific method for adsorbing a platinum group element derived from a platinum group element-containing catalyst from a hydrogenated nitrile rubber to a water-soluble polymer for its recovery and reuse, for example, as described above An aqueous solution of a water-soluble polymer is added to a water-soluble organic solvent solution of hydrogenated nitrile rubber obtained when hydrogenating nitrile rubber using a platinum group element-containing catalyst, and then this is stirred. The method of doing is mentioned. According to such a method, an aqueous solution of a water-soluble polymer is added to a water-soluble organic solvent solution of hydrogenated nitrile rubber, and this is stirred, so that the water-soluble organic solvent solution of hydrogenated nitrile rubber is added. The water-soluble polymer is coordinated to the platinum group element contained, and the platinum group element is incorporated into the water-soluble polymer. On the other hand, the water-soluble polymer is dehydrated by the influence of the water-soluble organic solvent. The water-soluble polymer can be precipitated in a state in which the platinum group element is adsorbed, whereby the platinum group element derived from the platinum group element-containing catalyst can be appropriately separated from the hydrogenated nitrile rubber. . In this case, a water-soluble polymer having a platinum group element adsorbed is obtained as a precipitate.

The water-soluble polymer used in the present invention is not particularly limited as long as it is water-soluble and soluble in water. Examples of such water-soluble polymers include amino group-containing (meth) acrylate polymers (meaning “amino group-containing methacrylate polymer and / or amino group-containing acrylate polymer”, the same shall apply hereinafter), carboxy. Modified group-containing (meth) acrylate polymers such as kill group-containing (meth) acrylate polymers, sulfonic acid group-containing (meth) acrylate polymers, and phosphate group-containing (meth) acrylate polymers; alkyl cellulose, Cellulose derivatives such as hydroxyalkyl cellulose and alkylhydroxyalkyl cellulose; and the like. Among these, the viewpoint of high affinity with platinum group elements and higher effect of separating platinum group elements from hydrogenated nitrile rubber. More preferred are modified group-containing (meth) acrylate polymers, amino groups Available (meth) acrylate-based polymer is more preferable. From the viewpoint of appropriately depositing the water-soluble polymer after incorporating the platinum group element derived from the platinum group element-containing catalyst into the water-soluble polymer, the water-soluble polymer is electrically neutral. It is preferably a water-soluble polymer (that is, a water-soluble polymer that has not been cationized or anionized), and particularly an electrically neutral amino group-containing (meth) acrylate polymer (that is, cationized). And amino group-containing (meth) acrylate polymers that are not anionized) are particularly preferred.

The amino group-containing (meth) acrylate polymer is not particularly limited as long as it is a polymer having a (meth) acrylic acid ester unit as a main component and containing at least a part of an amino group. . The amino group-containing (meth) acrylate polymer is, for example, a homopolymer of an amino group-containing (meth) acrylate monomer, or a co-polymer of two or more amino group-containing (meth) acrylate monomers. And a copolymer of one or more amino group-containing (meth) acrylic acid ester monomers and one or more monomers copolymerizable therewith.

Specific examples of amino group-containing (meth) acrylic acid ester monomers include N, N-dimethylaminoethyl acrylate (DMAEA), N, N-dimethylaminoethyl methacrylate (DMAEMA), and N, N-dimethylaminopropyl acrylate. N, N-dimethylaminopropyl methacrylate, N, Nt-butylaminoethyl acrylate, N, Nt-butylaminoethyl methacrylate, N, N-monomethylaminoethyl acrylate, N, N-monomethylaminoethyl methacrylate, etc. Aminoalkyl (meth) acrylates; N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N, N-dimethylaminopropylacrylamide, , N- dimethylaminopropyl methacrylamide, N, N- dimethylaminoethyl acrylamide, N, N- dimethylaminoethyl methacrylamide, N- aminoalkyl (meth) acrylamides such as N- isopropylacrylamide; and the like. The amino group-containing (meth) acrylic acid ester monomer may be used alone or in combination of two or more. Among these, aminoalkyl (meth) acrylate is preferable, and N, N-dimethylaminoethyl methacrylate (DMAEMA) is particularly preferable.

Specific examples of the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, itaconic anhydride, and fumaric anhydride; 2- Hydroxyl-containing vinyl such as hydroxyethyl acrylate, hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate; styrene, 2-methylstyrene, t-butylstyrene, chlorostyrene, Aromatic vinyl such as vinyl anisole, vinyl naphthalene, divinylbenzene; acrylamide, methacrylamide, N-methylol methacrylamide, N-methylol acrylamide, diacetone acrylamide, maleic acid Amides such as vinyl acetate; Vinyl esters such as vinyl acetate and vinyl propionate; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; Vinyl chloride, divinyl ether, methyl vinyl ketone, N-vinylacetamide, chloroprene, ethylene, propylene, isoprene , Butadiene, vinyl pyrrolidone, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, acrylonitrile, methacrylonitrile, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene Glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl Recall dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene Glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate, allyl methacrylate, allyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate , Isopropenyl-α, α-dimethylben Le isocyanate, allyl mercaptan, and the like. The copolymerizable monomers may be used singly or in combination.

In the amino group-containing (meth) acrylate polymer, the content ratio of the amino group-containing (meth) acrylate monomer unit is from the viewpoint of further enhancing the separation effect of the platinum group element from the hydrogenated nitrile rubber. It is preferably 30 to 100% by weight, more preferably 50 to 100% by weight, and particularly preferably 70 to 100% by weight.

The weight average molecular weight (Mw) of the water-soluble polymer used in the present invention is preferably 1,000 to 1,500,000, more preferably from the viewpoint of further enhancing the separation effect of the platinum group element from the hydrogenated nitrile rubber. Is from 5,000 to 1,200,000, more preferably from 10,000 to 1,000,000, even more preferably from 20,000 to 1,000,000, still more preferably from 100,000 to 1,000,000. 000, particularly preferably 300,000 to 1,000,000, most preferably 600,000 to 1,000,000. The weight average molecular weight (Mw) of the water-soluble polymer can be determined in terms of standard polystyrene or standard polyethylene glycol using a gel permeation chromatography method.

When adding a water-soluble polymer in the form of an aqueous solution to a water-soluble organic solvent solution of the hydrogenated nitrile rubber, the concentration of the water-soluble polymer in the aqueous solution is such that the platinum group element is separated from the hydrogenated nitrile rubber. From the viewpoint of carrying out efficiently, it is preferably 1 to 40% by weight, more preferably 2 to 30% by weight, and further preferably 5 to 20% by weight.

In addition, when the water-soluble polymer is added to the water-soluble organic solvent solution of the hydrogenated nitrile rubber in the form of an aqueous solution, the amount of the aqueous solution of the water-soluble polymer is determined so that the platinum group element is separated from the hydrogenated nitrile rubber. From the viewpoint of more efficiently performing the step, the amount of the water-soluble polymer added is preferably 0.1 to 50 parts by weight, and preferably 0.5 to 40 parts by weight with respect to 100 parts by weight of the hydrogenated nitrile rubber. Is more preferably 1 to 30 parts by weight, and particularly preferably 1 to 5 parts by weight.

The stirring method for adding a water-soluble polymer in the state of an aqueous solution to a water-soluble organic solvent solution of hydrogenated nitrile rubber and performing stirring is not particularly limited. For example, a method using a stirrer or a vibration method is used. Examples include a method using a tool. In addition, the stirring conditions during the stirring are not particularly limited, and the stirring temperature is preferably 5 to 50 ° C., more preferably 10 to 40 ° C., and the stirring speed is preferably 1 to 500 rpm. More preferably, it is 5 to 100 rpm. The mixing time is 1.5 hours or more, preferably 2 hours or more, more preferably 3 hours or more, and the upper limit is not particularly limited, but it is 24 hours or less, and the mixing time is in such a range. Separation of the platinum group element from the hydrogenated nitrile rubber can be performed with high efficiency.

<Recovery of platinum group element from water-soluble polymer adsorbed with platinum group element>
The platinum group element recovery method of the present invention is a method of recovering a platinum group element from the above-described water-soluble polymer adsorbed with the platinum group element. Specifically, in the platinum group element recovery method of the present invention, a water-soluble polymer on which the platinum group element is adsorbed and an aqueous hydrochloric acid solution are mixed in the presence of thiourea. The platinum group element is recovered from the water-soluble polymer adsorbed with the platinum group element.

Here, in the present invention, in such a platinum group element recovery method using hydrochloric acid and thiourea, a hydrochloric acid aqueous solution having a hydrochloric acid concentration adjusted to 0.25 to 31.50% by weight in advance is prepared. A water-soluble polymer adsorbed with a platinum group element is added to an aqueous hydrochloric acid solution adjusted to such a concentration. In particular, as a result of studies by the present inventors, a water-soluble polymer adsorbed with a platinum group element and a hydrochloric acid aqueous solution are mixed together (that is, a water-soluble polymer adsorbed with a platinum group element and a hydrochloric acid aqueous solution). If the concentration of hydrochloric acid in the aqueous hydrochloric acid solution is too high, the water-soluble polymer after recovery of the platinum group element will deteriorate, and this will be reused for the purpose of adsorbing the platinum group element. It has been found that there is a problem that the adsorption rate of the platinum group element is reduced.

According to the present invention, in such a situation, when the water-soluble polymer adsorbed with the platinum group element and the hydrochloric acid aqueous solution are mixed with each other (that is, the water-soluble polymer adsorbed with the platinum group element and hydrochloric acid It has been found that such a problem can be effectively solved by controlling the concentration of the aqueous hydrochloric acid solution at the time of contact with the aqueous solution to 0.25 to 31.50% by weight. In particular, according to the knowledge of the present inventors, when the hydrogenated nitrile rubber after the hydrogenation reaction was obtained as a water-soluble organic solvent solution, the platinum group element derived from the platinum group element-containing catalyst used for the hydrogenation Separation is carried out in a water-soluble organic solvent, so there is no acidic atmosphere, so water-soluble polymers used in such applications tend to be susceptible to hydrochloric acid. In contrast, according to the present invention, the water-soluble polymer adsorbed with the platinum group element and the hydrochloric acid aqueous solution are mixed with each other (that is, the water-soluble polymer adsorbed with the platinum group element). It has been found that such a problem can be effectively solved by controlling the concentration of the hydrochloric acid aqueous solution in the above range at the time of contact with the hydrochloric acid aqueous solution. Therefore, according to the present invention, when the water-soluble polymer suitably used for the adsorption of the platinum group element derived from the platinum group element-containing catalyst used for hydrogenation of the hydrogenated nitrile rubber is used as the adsorbent, When an amino group-containing (meth) acrylate polymer is used as the adsorbent, the aqueous hydrochloric acid solution is mixed with each other (that is, the water-soluble polymer on which the platinum group element is adsorbed, the aqueous hydrochloric acid solution, The concentration of the aqueous hydrochloric acid solution at the time of contact) tends to increase. Therefore, when a water-soluble polymer is used as the adsorbent, an amino group-containing (meth) acrylate polymer, in particular, is used. When this is used, the effect of the present invention becomes remarkable.

In the platinum group element recovery method of the present invention, the hydrochloric acid concentration in the hydrochloric acid aqueous solution prepared in advance is 0.25 to 31.50% by weight, preferably 10.0 to 20.0% by weight, more preferably 14%. 0.0-17.5% by weight. If the concentration of hydrochloric acid in the aqueous hydrochloric acid solution is too high, the recovery efficiency when the water-soluble polymer after recovering the platinum group element is reused for the purpose of adsorbing the platinum group element is lowered. On the other hand, if the hydrochloric acid concentration in the aqueous hydrochloric acid solution is too low, the recovery efficiency of the platinum group element from the water-soluble polymer adsorbed with the platinum group element is lowered.

In addition, when adding the water-soluble polymer in which the platinum group element is adsorbed to the hydrochloric acid aqueous solution, the water-soluble polymer in which the platinum group element is adsorbed may be added in a solid state, or an aqueous solution. However, it is easy to control the hydrochloric acid concentration in the mixed solution when mixing the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea. From the viewpoint, the water-soluble polymer on which the platinum group element is adsorbed is preferably added in a solid state. In this case, the water-soluble polymer is not limited as long as it can be said to be substantially in a solid state, and may contain a slight amount of water (for example, about 1% by weight or less). .

In the platinum group element recovery method of the present invention, a hydrochloric acid aqueous solution and a water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea, and these are mixed. In this case, the content ratio of thiourea in the mixed solution is 0.5 to 20.0% by weight, preferably 3.0 to 18.0% by weight, more preferably 5.0 to 17%. 0% by weight. When the content ratio of thiourea in the mixed solution is too small, the recovery efficiency of the platinum group element from the water-soluble polymer adsorbed with the platinum group element is lowered. On the other hand, if the content ratio of thiourea is too large, sulfur is taken into the water-soluble polymer, and when the water-soluble polymer is reused as an adsorbent, such as hydrogenated nitrile rubber that is the object of adsorption. Sulfur is mixed into the conjugated diene rubber, which may cause cross-linking due to heat in the drying process, etc., or the hydrogenated conjugated diene rubber such as hydrogenated nitrile rubber that is finally obtained contains unintended sulfur. As a result, it may be difficult to control crosslinking.

In the platinum group element recovery method of the present invention, it is sufficient if the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea. Although it is not particularly limited, (1) thiourea is added in advance to an aqueous hydrochloric acid solution, and a water-soluble polymer adsorbed with a platinum group element is added to and mixed with an aqueous hydrochloric acid solution containing thiourea. Method, (2) when adding a water-soluble polymer adsorbed with a platinum group element to an aqueous hydrochloric acid solution, adding thiourea as it is or in the state of an aqueous solution and mixing, (3) For example, there is a method in which mixing is started by adding a water-soluble polymer adsorbed with a platinum group element and then adding thiourea as it is or in the state of an aqueous solution to continue mixing. Among these, the method (1) is preferable from the viewpoint of operability. In this case, the content ratio of thiourea in the aqueous hydrochloric acid solution containing thiourea is not particularly limited, but is preferably 1.0 to 35.0% by weight, more preferably 2.0 to 25.0% by weight. More preferably, it is 5.0 to 10.0% by weight.

Further, in the platinum group element recovery method of the present invention, the platinum group element in the mixed solution when the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea. The content ratio of the water-soluble polymer adsorbed by is 16 to 72% by weight, preferably 20 to 65% by weight, more preferably 20 to 55% by weight, still more preferably 30 to 50% by weight. . If the content of the water-soluble polymer adsorbed with the platinum group element in the mixed solution is too small, the recovery rate of the water-soluble polymer after the platinum group element is recovered (that is, the water-soluble polymer that can be reused) The ratio of the polymer) is reduced. On the other hand, if the content ratio of the water-soluble polymer to which the platinum group element is adsorbed is too large in the mixed solution, the recovery efficiency of the platinum group element from the water-soluble polymer to which the platinum group element has been adsorbed decreases.

It should be noted that when the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea, the hydrochloric acid concentration in the mixed solution (that is, the water-soluble polymer adsorbed with the platinum group element and The concentration of hydrochloric acid in the mixed solution after addition of thiourea is not particularly limited, but is preferably 1.0 to 16.0% by weight, more preferably 5.0 to 14.0% by weight, and still more preferably Is 6.0 to 9.0% by weight. By making the hydrochloric acid concentration in the mixed solution in the above range, the recovery efficiency of the platinum group element from the water-soluble polymer adsorbed with the platinum group element can be more appropriately increased.

In the platinum group element recovery method of the present invention, the mixing time for mixing the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea is 1.5 hours or more. It is preferably 2 hours or more, more preferably 2 to 4 hours. If the mixing time is too short, the recovery efficiency of the platinum group element from the water-soluble polymer adsorbed with the platinum group element is lowered. On the other hand, if the mixing time is too long, the cycle time of the entire process becomes longer and the productivity is lowered.

The mixing temperature in mixing the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea is not particularly limited, but is preferably 5 to 90 ° C., more preferably 10 to 30. ° C. Examples of the mixing method when mixing the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea include a method using a stirrer and a method using a shaker.

Then, after mixing an aqueous hydrochloric acid solution and a water-soluble polymer adsorbed with a platinum group element in the presence of thiourea, the resulting mixture is an organic material that is not soluble in the water-soluble polymer. By adding a solvent, the water-soluble polymer is precipitated, and the water-soluble polymer is separated from the mixed solution by a method such as filtration. The platinum group element detached from the water-soluble polymer can be recovered from the mixed solution by incineration or the like. On the other hand, the deposited water-soluble polymer contains platinum group elements derived from a platinum group element-containing catalyst used for hydrogenating carbon-carbon double bonds contained in conjugated diene rubbers such as nitrile rubber. It can be reused as an adsorbent to be adsorbed. The organic solvent that is not soluble in the water-soluble polymer is not particularly limited and may be selected according to the type of the water-soluble polymer to be used. For example, acetone, methyl ethyl ketone, diethyl ketone, methyl isopropyl Ketones such as ketones; ethers such as tetrahydrofuran and dioxane; esters such as ethyl acetate; and the like. Among these organic solvents, ketones are preferably used, and acetone is particularly preferably used.

In particular, in the recovery method of the present invention, the aqueous hydrochloric acid solution having the predetermined concentration described above is prepared in advance, and the aqueous hydrochloric acid solution prepared in advance and the water-soluble polymer adsorbed with the platinum group element are mixed at a specific concentration. Because it is mixed in the presence of thiourea, the platinum group element can be recovered while suppressing the deterioration of the water-soluble polymer adsorbed with the platinum group element. The water-soluble polymer after recovering the platinum group element can be recovered in a state of maintaining a high adsorption rate while realizing the recovery of the platinum group element at the same time. It can be suitably reused for applications. In addition, in the recovery method of the present invention, the aqueous hydrochloric acid solution adsorbed with the platinum group element is mixed with the aqueous hydrochloric acid solution and the water soluble polymer adsorbed with the platinum group element in the presence of thiourea. Since the mixing is carried out at a content ratio of 16 to 72% by weight, this makes it possible to recover the water-soluble polymer after removing the platinum group element at a high recovery rate. Also, it can be suitably reused for applications in which platinum group elements are adsorbed.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples. In the following, “part” is based on weight unless otherwise specified.

<Production Example 1>
(Production of hydrogenated acrylonitrile-butadiene copolymer)
A reactor was charged with 2 parts of potassium oleate, 180 parts of ion exchanged water, 37 parts of acrylonitrile, and 0.5 part of t-dodecyl mercaptan in this order. Next, after replacing the inside of the reactor with nitrogen, 63 parts of butadiene was added, the reactor was cooled to 10 ° C., and 0.01 parts of cumene hydroperoxide and 0.01 parts of ferrous sulfate were added. . The contents were then stirred for 16 hours while maintaining the reactor at 10 ° C. Thereafter, a 10% by weight hydroquinone aqueous solution was added to the reactor to stop the polymerization reaction, and then the unreacted monomer was removed from the polymerization reaction solution to obtain an acrylonitrile-butadiene copolymer latex. It was. The polymerization conversion was 90%.

Next, 300 parts of coagulated water in which 3 parts of calcium chloride (coagulant) is dissolved is placed in a reactor different from the above, and the latex obtained above is dropped into the coagulated water while stirring at 50 ° C. did. And after adding potassium hydroxide aqueous solution and keeping pH at 11.5 here, polymer crumb was precipitated, the polymer crumb was fractionated from coagulation water, washed with water, and dried under reduced pressure at 50 degreeC. Subsequently, the obtained polymer crumb was dissolved in acetone to prepare an acetone solution having a polymer content of 15% by weight.

Then, a silica-supported palladium (Pd) catalyst (Pd amount is 1000 ppm by weight in the ratio of “Pd metal / acrylonitrile-butadiene copolymer”) is added to the acetone solution of the obtained acrylonitrile-butadiene copolymer. Was put into an autoclave equipped with a stirrer, and dissolved oxygen was removed by flowing nitrogen gas for 10 minutes. Next, after the system was replaced twice with hydrogen gas, 5 MPa of hydrogen was pressurized, and the contents were heated to 50 ° C. and stirred for 6 hours to carry out a hydrogenation reaction.

After completion of the hydrogenation reaction, the reaction system was cooled to room temperature, and the hydrogen in the system was replaced with nitrogen. The hydrogenated acrylonitrile-butadiene copolymer solution obtained by the hydrogenation reaction is filtered to recover the silica-supported palladium catalyst, and the filtered hydrogenated acrylonitrile-butadiene copolymer solution is recovered. Obtained.

A part of the filtered hydrogenated acrylonitrile-butadiene copolymer solution obtained above was collected and poured into 10 times the amount of water to precipitate the copolymer. The copolymer was dried with a vacuum dryer for 24 hours to obtain a solid hydrogenated acrylonitrile-butadiene copolymer. With respect to the obtained solid hydrogenated acrylonitrile-butadiene copolymer, the amount of palladium in the copolymer was measured by atomic absorption measurement. As a result, the amount of palladium was 151 ppm by weight. Further, when the iodine value was measured according to JIS K6235, the iodine value was 7.6.

<Production Example 2>
(Production of water-soluble polymers)
A reactor was charged with 10 parts of N, N-dimethylaminoethyl methacrylate (DMAEMA) and 37 parts of ion-exchanged water, and after the inside of the reactor was replaced with nitrogen, the reactor was heated to 75 ° C. 0.35 part of ammonium disulfate was added. The contents were then stirred for 1 hour while maintaining the reactor at 75 ° C. The obtained aqueous polymer solution was dropped into acetone to precipitate a polymer, and then the polymer was separated from the acetone, washed with acetone, and then dried under reduced pressure at 50 ° C. to obtain a solid aqueous solution. Polymer (poly (N, N-dimethylaminoethyl methacrylate)) was obtained. About the obtained water-soluble polymer, when the weight average molecular weight (Mw) of polystyrene conversion was measured by GPC measurement, the weight average molecular weight (Mw) was 650,000. Then, 1 part of the obtained water-soluble polymer was dissolved in 10 parts of ion-exchanged water to obtain an aqueous solution of water-soluble polymer (water-soluble polymer concentration: 9.1% by weight).

<Reference Example 1>
(Separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution using water-soluble polymer)
Part of the filtered hydrogenated acrylonitrile-butadiene copolymer solution obtained in Production Example 1 is collected and transferred to a vial so that the concentration of the hydrogenated acrylonitrile-butadiene copolymer is 8% by weight. After adjusting the concentration by adding acetone, 25 parts of the aqueous solution of the water-soluble polymer obtained in Production Example 2 was added to 100 parts of the hydrogenated acrylonitrile-butadiene copolymer. Subsequently, the mixture was stirred for 24 hours at 25 ° C. and 100 rpm using a shaker (trade name “RECIPRO SHAKER SR-1”, manufactured by Taitec Co., Ltd.). Then, the water-soluble polymer was precipitated as a solid by stirring for 24 hours. Subsequently, the water-soluble polymer which adsorb | sucked palladium was obtained by performing filtration. And about the obtained solid water-soluble polymer, when the amount of palladium in water-soluble polymer was measured by atomic absorption measurement, the amount of palladium was 543 weight ppm.

<Example 1>
(Recovery of palladium from water-soluble polymer adsorbed with palladium)
Using a commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, special reagent grade), thiourea (manufactured by Wako Pure Chemical Industries, special reagent grade), and ion-exchanged water, a hydrochloric acid concentration of 16.6% by weight, A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 6.9% by weight was obtained. To 100 parts of the resulting aqueous thiourea-containing hydrochloric acid solution, 100 parts of the solid water-soluble polymer obtained by adsorbing palladium obtained in Reference Example 1 was added, and then a shaker (trade name “RECIPRO SHAKER SR- 1 ”(manufactured by Taitec Co., Ltd.) was stirred for 4 hours at 25 ° C. and 120 rpm. Thereafter, the mixed liquid after stirring is put into an equal amount or more of acetone, stirred using a shaker (trade name “RECIPRO SHAKER SR-1”, manufactured by Taitec Co., Ltd.), and filtered to obtain a water-soluble solution. A precipitate of a functional polymer was obtained. When the amount of palladium in the water-soluble polymer was measured by atomic absorption measurement of the obtained solid water-soluble polymer, the amount of palladium was reduced to 16.4 ppm by weight. The amount of the water-soluble polymer precipitate recovered by filtration was 99.2 parts, and the water-soluble polymer recovery rate (water-soluble polymer recovery rate (% by weight)) = (recovered The amount of the water-soluble polymer precipitate / the amount of the water-soluble polymer charged into the thiourea-containing hydrochloric acid aqueous solution × 100) was 99.2% by weight.

(Separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution)
Then, 1 part of the recovered precipitate of the water-soluble polymer is dissolved again in 10 parts of ion-exchanged water to form an aqueous solution of the water-soluble polymer (water-soluble polymer concentration: 9.1% by weight). In the same manner as in Reference Example 1, the palladium was separated from the hydrogenated acrylonitrile-butadiene copolymer solution. As a result, when the amount of palladium in the water-soluble polymer was measured by atomic absorption measurement on the obtained solid water-soluble polymer, the amount of palladium was 528.1 ppm by weight, and the recovery operation was performed as described above. The water-soluble polymer that had passed through was able to be suitably reused for the separation of palladium from the hydrogenated acrylonitrile-butadiene copolymer solution.

The operations of “recovering palladium from water-soluble polymer adsorbed with palladium” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated twice in the same manner. (3 times in total). Table 1 shows the results of the first, second and third times. In Table 1, the “recovery rate of water-soluble polymer” indicates that the higher the value, the “recovery rate of water-soluble polymer after performing palladium recovery from water-soluble polymer adsorbed palladium”. This is preferable because the amount recovered is large. In Example 1, the “recovery rate of the water-soluble polymer” was high: 1st: 99.2% by weight, 2nd: 99.5% by weight, 3rd: 99.1% by weight. there were. In addition, it can be determined that the lower the value of the “residual palladium amount in the water-soluble polymer”, the higher the recovery efficiency when “recovering palladium from the water-soluble polymer adsorbed with palladium” is performed. Therefore, it is preferable. In Example 1, the “residual amount of palladium in the water-soluble polymer” is as low as 1st: 16.4 ppm by weight, 2nd: 17.3 ppm by weight, 3rd: 16.9 ppm by weight. It was suppressed. Further, in Table 1, the “adsorption amount of palladium in the water-soluble polymer after reuse” indicates that the higher the value, the more the water-soluble polymer is expressed as “palladium adsorption from the hydrogenated acrylonitrile-butadiene copolymer solution”. This is preferable because it can be judged that the adsorption efficiency is high when it is reused for the “separation” operation. In Example 1, the “adsorption amount of palladium in the water-soluble polymer after reuse” is as follows: First time: 528.1 wt ppm, Second time: 525.3 wt ppm, Third time: 526.4 wt ppm , Both were high and excellent in adsorption efficiency.

<Example 2>
The amount of the solid water-soluble polymer adsorbed with palladium was changed to 50 parts with respect to 100 parts of a thiourea-containing aqueous hydrochloric acid solution having a hydrochloric acid concentration of 16.6% by weight and a thiourea concentration of 6.9% by weight, and In the same manner as in Example 1 except that the stirring time using a shaker was changed to 2 hours, “Recovery of palladium from water-soluble polymer adsorbed with palladium” and “hydrogenated acrylonitrile-butadiene” Each operation of “separation of palladium from the copolymer solution” was repeated three times in total. Table 1 shows the results of the first, second and third times.

<Example 3>
A commercially available aqueous hydrochloric acid solution (concentration of 12 mol / L, manufactured by Wako Pure Chemical Industries, special grade of reagent) and thiourea (produced by Wako Pure Chemical Industries, special grade of reagent) are diluted with ion-exchanged water, and a hydrochloric acid concentration of 30.9% by weight A thiourea-containing hydrochloric acid aqueous solution having a thiourea concentration of 6.9% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of the thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 30.9% by weight and a thiourea concentration of 6.9% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Example 4>
A commercially available aqueous hydrochloric acid solution with a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, special grade of reagent), thiourea (manufactured by Wako Pure Chemical Industries, special grade of reagent), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 7.4% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of the thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 0.4% by weight and a thiourea concentration of 7.4% by weight prepared as described above was used. The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Example 5>
A commercially available aqueous hydrochloric acid solution with a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, special grade of reagent), thiourea (manufactured by Wako Pure Chemical Industries, special grade of reagent), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 32.0% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 15.4% by weight and a thiourea concentration of 32.0% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Example 6>
Except for changing the amount of the solid water-soluble polymer adsorbed with palladium to 25 parts to 100 parts of a thiourea-containing aqueous hydrochloric acid solution having a hydrochloric acid concentration of 16.6% by weight and a thiourea concentration of 6.9% by weight, In the same manner as in Example 1, the operations of “recovery of palladium from water-soluble polymer adsorbed with palladium” and “separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. went. Table 1 shows the results of the first, second and third times.

<Example 7>
Except for changing the amount of the solid water-soluble polymer adsorbed with palladium to 185 parts to 100 parts of a thiourea-containing aqueous hydrochloric acid solution having a hydrochloric acid concentration of 16.6% by weight and a thiourea concentration of 6.9% by weight, In the same manner as in Example 1, the operations of “recovery of palladium from water-soluble polymer adsorbed with palladium” and “separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. went. Table 1 shows the results of the first, second and third times.

<Comparative Example 1>
100 parts of the water-soluble polymer adsorbed with palladium obtained in Reference Example 1 was dissolved in 77.65 parts of ion-exchanged water to obtain an aqueous solution of the water-soluble polymer. To 177.65 parts of the aqueous solution of the obtained water-soluble polymer, 18.9 parts of a commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, reagent special grade) and thiourea (manufactured by Wako Pure Chemical Industries, reagent (Special grade) Except for adding 3.45 parts, by performing operations such as mixing with a shaker in the same manner as in Example 1, "recovering palladium from water-soluble polymer adsorbed palladium" went. In the same manner as in Example 1, the operations of “recovery of palladium from water-soluble polymer adsorbed with palladium” and “separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution” are performed. Was repeated a total of 3 times. Table 1 shows the results of the first, second and third times.

<Comparative example 2>
Except that the stirring time using a shaker was changed to 1 hour, in the same manner as in Example 1, “Recovery of palladium from water-soluble polymer adsorbed with palladium” and “hydrogenated acrylonitrile-butadiene copolymer” Each operation of “separation of palladium from polymer solution” was repeated a total of three times. Table 1 shows the results of the first, second and third times.

<Comparative Example 3>
A commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, reagent special grade), thiourea (manufactured by Wako Pure Chemical Industries, reagent special grade), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 6.4% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 32.3% by weight and a thiourea concentration of 6.4% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Comparative example 4>
A commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, special grade of reagent), thiourea (manufactured by Wako Pure Chemical Industries, special grade of reagent), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 6.4% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of the thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 33.6% by weight and a thiourea concentration of 6.4% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Comparative Example 5>
A commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, reagent special grade), thiourea (manufactured by Wako Pure Chemical Industries, reagent special grade), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 7.4% by weight was obtained. In the same manner as in Example 1 except that 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 0.2% by weight and a thiourea concentration of 7.4% by weight prepared above was used. The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Comparative Example 6>
A commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, reagent special grade), thiourea (manufactured by Wako Pure Chemical Industries, special reagent grade), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 0.7% by weight was obtained. Then, in the same manner as in Example 1 except that 100 parts of the thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 16.9% by weight and a thiourea concentration of 0.7% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Comparative Example 7>
A commercially available aqueous hydrochloric acid solution having a concentration of 12 mol / L (manufactured by Wako Pure Chemical Industries, reagent special grade), thiourea (manufactured by Wako Pure Chemical Industries, special reagent grade), and ion-exchanged water were used. A thiourea-containing hydrochloric acid aqueous solution having a urea concentration of 0.4% by weight was obtained. In the same manner as in Example 1 except that 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 16.9% by weight and a thiourea concentration of 0.4% by weight was used, The operations of “recovering palladium from water-soluble polymer” and “separating palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were repeated three times in total. Table 1 shows the results of the first, second and third times.

<Comparative Example 8>
Except for changing the input amount of the solid water-soluble polymer adsorbed with palladium to 17 parts with respect to 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 16.9% by weight and a thiourea concentration of 6.9% by weight, In the same manner as in Example 1, the operations of “recovery of palladium from water-soluble polymer on which palladium was adsorbed” and “separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were performed in total 3 Repeated times. Table 1 shows the results of the first, second and third times.

<Comparative Example 9>
Except for changing the amount of solid water-soluble polymer adsorbed with palladium to 300 parts to 100 parts of a thiourea-containing hydrochloric acid aqueous solution having a hydrochloric acid concentration of 16.9% by weight and a thiourea concentration of 6.9% by weight, In the same manner as in Example 1, the operations of “recovery of palladium from water-soluble polymer on which palladium was adsorbed” and “separation of palladium from hydrogenated acrylonitrile-butadiene copolymer solution” were performed in total 3 Repeated times. Table 1 shows the results of the first, second and third times.

As shown in Table 1, a hydrochloric acid aqueous solution containing 0.25 to 31.50% by weight hydrochloric acid was prepared in advance, and the prepared hydrochloric acid aqueous solution and a water-soluble polymer adsorbed with a platinum group element were mixed. Mix for 1.5 hours or more so that the content of the water-soluble polymer adsorbed with the platinum group element is 16 to 72% by weight and the content of thiourea is 0.5 to 20.0% by weight. As a result, the recovery rate of the water-soluble polymer is increased, the residual amount of palladium in the water-soluble polymer is kept low, and the amount of palladium adsorbed in the water-soluble polymer after reuse is increased. The results were good (Examples 1 to 7).

On the other hand, when a water-soluble polymer adsorbed with a platinum group element is in the form of an aqueous solution, a hydrochloric acid solution having a concentration of 12 mol / L (concentration 37% by weight) is added thereto, or the hydrochloric acid concentration in a hydrochloric acid aqueous solution prepared in advance Is too high, the water-soluble polymer deteriorated, resulting in a decrease in the amount of palladium adsorbed in the water-soluble polymer after reuse (Comparative Examples 1, 3, and 4).
Also, when mixing hydrochloric acid aqueous solution and water-soluble polymer adsorbed platinum group element in the presence of thiourea, mixing time is too short, or hydrochloric acid concentration in hydrochloric acid aqueous solution prepared in advance is too low Furthermore, when the concentration of thiourea was too low, the amount of palladium remaining in the water-soluble polymer was high, resulting in poor palladium recovery efficiency from the water-soluble polymer (Comparative Examples 2 and 5). , 6, 7).
Furthermore, when the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea and the content ratio of the water-soluble polymer adsorbed with the platinum group element is too low, As a result, the recovery rate of the water-soluble polymer was lowered (Comparative Example 8).
In addition, when the aqueous hydrochloric acid solution and the water-soluble polymer adsorbed with the platinum group element are mixed in the presence of thiourea, when the content ratio of the water-soluble polymer adsorbed with the platinum group element is too high, The residual amount of palladium in the water-soluble polymer was increased, resulting in poor efficiency of recovering palladium from the water-soluble polymer (Comparative Example 9).

Claims (9)

A method of recovering a platinum group element from a water-soluble polymer adsorbed with a platinum group element,
A preparation step of preparing an aqueous hydrochloric acid solution containing 0.25 to 31.50 wt% hydrochloric acid;
A mixing step of mixing the hydrochloric acid aqueous solution prepared in the preparation step and the water-soluble polymer adsorbed with the platinum group element in the presence of thiourea for 1.5 hours or more,
Mixing is performed with the content ratio of the thiourea in the mixed solution in the mixing step being 0.5 to 20.0 wt% and the content ratio of the water-soluble polymer adsorbed with the platinum group element being 16 to 72 wt%. A method for recovering platinum group elements. The method for recovering a platinum group element according to claim 1, wherein the content ratio of the hydrochloric acid in the mixed solution in the mixing step is 1.0 to 16.0% by weight. The method for recovering a platinum group element according to claim 1 or 2, wherein the water-soluble polymer is an amino group-containing (meth) acrylate polymer. The amino group-containing (meth) acrylate polymer is a homopolymer of N, N-dimethylaminoethyl methacrylate (DMAEMA) or two or more monomers including N, N-dimethylaminoethyl methacrylate (DMAEMA) The method for recovering a platinum group element according to claim 3, which is a copolymer of The method for recovering a platinum group element according to any one of claims 1 to 4, wherein the platinum group element is palladium. The method for recovering a platinum group element according to any one of claims 1 to 5, wherein the platinum group element is a platinum group element derived from a platinum group element-containing catalyst used in a hydrogenation reaction of nitrile rubber. In the mixing step, the hydrochloric acid aqueous solution prepared in the preparation step and the thiourea are mixed in advance to obtain a hydrochloric acid aqueous solution containing thiourea. The method for recovering a platinum group element according to any one of claims 1 to 6, which is a step of adding and mixing a water-soluble polymer adsorbed with a platinum group element. The method for recovering a platinum group element according to claim 7, wherein the content ratio of the thiourea in the hydrochloric acid aqueous solution containing the thiourea is 1.0 to 35.0 wt%. In the mixing step, when the water-soluble polymer adsorbed with the platinum group element is added to the hydrochloric acid aqueous solution prepared in the preparation step, the water-soluble polymer adsorbed with the platinum group element is added in a solid state. The method for recovering a platinum group element according to any one of claims 1 to 8.