JP6123284B2 - Noble metal ion desorbing agent and noble metal recovery method - Google Patents

Description

  The present invention relates to a noble metal ion desorbing agent for desorbing noble metal ions adsorbed on a noble metal ion adsorbing agent, and use thereof. More specifically, the present invention relates to a noble metal ion desorbing agent containing a specific sulfide compound, a method for desorbing noble metal ions using the desorbing agent, and a method for recovering a noble metal from a desorption solution by reduction treatment.

  Industrial catalysts or automobile exhaust gas purification catalysts and many electrical appliances use noble metals such as palladium, platinum and rhodium. Since noble metals are expensive and useful as resources, they are conventionally collected and recycled after use. In recent years, the demand for resource conservation has increased, and the importance of recovery and recycling of precious metals has increased.

  In order to separate and recover precious metals, precipitation separation methods, ion exchange methods, electrolytic deposition methods, solvent extraction methods, and the like have been developed. Of these, solvent extraction methods are widely used from the viewpoint of economy and operability. It has been adopted.

  As a solvent extraction method, palladium ions are back-extracted using an organic phase using a dialkyl sulfide compound as an extractant and an aqueous phase containing ammonia as a back extractant (see, for example, Patent Document 1). However, palladium ion extraction with dialkyl sulfide has a problem that the extraction speed is low. In order to improve the extraction speed, an extraction agent in which an amide group is introduced in the vicinity of sulfur of a dialkyl sulfide has been proposed, and a method for extracting palladium ions using an acidic thiourea aqueous solution as a back extraction agent has been proposed. (For example, refer to Patent Document 2).

  As a palladium ion separation method other than the extraction method, an adsorption method has been proposed (see, for example, Patent Document 3). According to this method, an insoluble palladium ion adsorbent is prepared by immobilizing a specific sulfide compound on a styrene derivative polymer (for example, polychloromethylstyrene) carrier as a ligand (acceptor) of palladium ion. Adsorption of palladium ions is performed by directly adding an agent to an aqueous solution in which palladium ions are dissolved. However, since the ligand of the adsorbent is a sulfide compound, there is a problem in the adsorption rate as in Patent Document 1.

  The present applicants have already applied for a patent for a palladium ion adsorbent (see, for example, Patent Documents 4 and 5).

  When using an extractant in which an amide group is introduced in the vicinity of sulfur of a dialkyl sulfide, or an adsorbent having the compound as a ligand, the reverse extraction or desorption of palladium ions using hydrochloric acid or ammonia is low in efficiency. A thiourea aqueous solution is preferably used (see, for example, Patent Document 5).

  However, in order to produce high-purity metallic palladium from palladium ions separated and recovered using an aqueous thiourea solution, it is necessary to carry out a complicated high-purity process, which has been industrially problematic.

Japanese Patent Laid-Open No. 9-279264 International Publication No. 2005/083131 Pamphlet JP-A-5-105973 JP 2011-41916 A JP 2011-41918 A

  The present invention has been made in view of the above-described background art, and the object thereof is to efficiently desorb palladium ions from a palladium ion adsorbent, and from a palladium ion desorbing liquid obtained by the operation, it is inexpensive. Another object of the present invention is to provide a palladium ion desorbing agent that can easily separate and recover metallic palladium.

  As a result of intensive studies to solve the above problems, the present inventors have found that the noble metal ion desorbing agent containing the sulfide compound represented by the general formula (1) is superior to conventionally known hydrochloric acid and ammonia. It was found that palladium ion desorbability was exhibited. Furthermore, by reducing the palladium ion desorption solution obtained using the noble metal ion desorption agent containing the sulfide compound represented by the general formula (1), the concentration can be easily increased as compared with the case of using thiourea. The inventors have found that pure noble metals can be recovered, and have completed the present invention.

  That is, the present invention relates to the general formula (1)

（式中、Ｒはメチル基、エチル基、ビニル基、炭素数３〜８の直鎖、分岐若しくは環状の炭化水素基、炭素数６〜１４の芳香族炭化水素基、カルボキシルメチル基、カルバモイルメチル基、４−カルボキシル−３−チアブチル基、又は４−カルバモイル−３−チアブチル基を表し、Ｘは水酸基若しくは１級アミノ基を表す。）
で表されるスルフィド化合物を含む貴金属イオン脱着剤及び貴金属の回収方法に関する。
［１］ 下記一般式（１）で表されるスルフィド化合物を含む貴金属イオン脱着剤。

(In the formula, R represents a methyl group, an ethyl group, a vinyl group, a linear, branched or cyclic hydrocarbon group having 3 to 8 carbon atoms, an aromatic hydrocarbon group having 6 to 14 carbon atoms, a carboxyl methyl group, and a carbamoylmethyl group. Group, 4-carboxyl-3-thiabutyl group, or 4-carbamoyl-3-thiabutyl group, and X represents a hydroxyl group or a primary amino group.)
The noble metal ion desorption agent containing the sulfide compound represented by these, and the collection | recovery method of a noble metal.
[1] A noble metal ion desorbing agent containing a sulfide compound represented by the following general formula (1).

（式中、Ｒはメチル基、エチル基、ビニル基、炭素数３〜８の直鎖、分岐若しくは環状の炭化水素基、炭素数６〜１４の芳香族炭化水素基、カルボキシルメチル基、カルバモイルメチル基、４−カルボキシル−３−チアブチル基、又は４−カルバモイル−３−チアブチル基を表し、Ｘは水酸基若しくは１級アミノ基を表す。）
［２］ 前記スルフィド化合物がチオジグリコール酸であることを特徴とする［１］に記載の貴金属イオン脱着剤。
［３］ ［１］又は［２］に記載の貴金属イオン脱着剤を、貴金属イオンを吸着した吸着剤と接触させて、貴金属イオンを脱着させることを特徴とする貴金属イオンの脱着方法。
［４］ ［３］に記載の貴金属イオンの脱着方法により得られた貴金属イオンを含む溶液を還元処理して、貴金属を回収することを特徴とする貴金属の回収方法。
［５］ 貴金属イオンがパラジウムイオンであり、且つ、貴金属がパラジウムであることを特徴とする［４］に記載の貴金属の回収方法。

(In the formula, R represents a methyl group, an ethyl group, a vinyl group, a linear, branched or cyclic hydrocarbon group having 3 to 8 carbon atoms, an aromatic hydrocarbon group having 6 to 14 carbon atoms, a carboxyl methyl group, and a carbamoylmethyl group. Group, 4-carboxyl-3-thiabutyl group, or 4-carbamoyl-3-thiabutyl group, and X represents a hydroxyl group or a primary amino group.)
[2] The noble metal ion desorbing agent according to [1], wherein the sulfide compound is thiodiglycolic acid.
[3] A method for desorbing a noble metal ion, wherein the noble metal ion desorbing agent according to [1] or [2] is brought into contact with an adsorbent adsorbing the noble metal ion to desorb the noble metal ion.
[4] A method for recovering a noble metal, comprising reducing the solution containing the noble metal ion obtained by the method for desorbing a noble metal ion according to [3] to recover the noble metal.
[5] The method for recovering a noble metal according to [4], wherein the noble metal ion is palladium ion and the noble metal is palladium.

  Hereinafter, the present invention will be described in detail.

  In the sulfide compound represented by the general formula (1), R represents a methyl group, an ethyl group, a vinyl group, a linear, branched or cyclic hydrocarbon group having 3 to 8 carbon atoms, and an aromatic carbon atom having 6 to 14 carbon atoms. A hydrogen group, a carboxylmethyl group, a carbamoylmethyl group, a 4-carboxyl-3-thiabutyl group, or a 4-carbamoyl-3-thiabutyl group is represented, and X represents a hydroxyl group or a primary amino group.

  Examples of the linear, branched or cyclic hydrocarbon group having 3 to 8 carbon atoms include propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, 2-ethylhexyl group, allyl group, 1-propenyl group, isopropenyl group, 1-butenyl group, 2-butenyl group, 2-methylallyl group, 1- Heptynyl, 1-hexenyl, 1-heptenyl, 1-octenyl, 2-methyl-1-propenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclohexenyl Group, cyclohexadienyl group, cyclohexatrienyl group, cyclooctane Group, cyclooctadienyl group and the like.

  Examples of the aromatic hydrocarbon group having 6 to 14 carbon atoms include phenyl group, naphthyl group, anthryl group, tolyl group, xylyl group, cumenyl group, benzyl group, phenethyl group, styryl group, cinnamyl group, biphenyl group, phenanthryl. Groups and the like.

  Among these, R is preferably a carboxymethyl group and X is particularly preferably a hydroxyl group from the viewpoint of desorbability of precious metal ions and availability. That is, thiodiglycolic acid is particularly preferable.

  When the sulfide compound represented by the general formula (1) has a carboxyl group, it can also be used as a lithium, sodium or potassium salt.

  The noble metal ion desorbing agent containing the sulfide compound represented by the general formula (1) is preferably a solution of the sulfide compound represented by the general formula (1), and the sulfide compound is not particularly limited. It is preferably used in a concentration range of 1 to 20% by weight.

  The noble metal ion desorbing agent containing the sulfide compound represented by the general formula (1) can be used in any of basic, neutral and acidic liquids depending on the purpose.

  Although it does not specifically limit as an additive for adjusting liquidity, Inorganic acids, such as hydrochloric acid, a sulfuric acid, nitric acid, or inorganic bases, such as sodium hydroxide and potassium hydroxide, are used.

  A method for desorbing a noble metal ion comprising using a noble metal ion desorbing agent containing a sulfide compound represented by the general formula (1), a noble metal ion desorbing agent comprising a sulfide compound represented by the general formula (1), The noble metal ions are desorbed by contacting with an adsorbent adsorbing the noble metal ions. Here, the noble metal ion desorbent containing the sulfide compound represented by the general formula (1) in the present invention can be applied to an extractant dissolved in an organic solvent (so-called solvent extraction method). It is preferable to apply to an adsorbent that does not use.

  In the noble metal ion desorption method using the noble metal ion desorption agent containing the sulfide compound represented by the general formula (1), the noble metal ion to be desorbed is not particularly limited. And noble metal ions having high affinity for sulfur atoms, such as platinum ions and gold ions, and are particularly effective for palladium ions.

  In the noble metal ion desorption method using the noble metal ion desorption agent containing the sulfide compound represented by the general formula (1), as the adsorbent to be treated, an amberlite made by Organo or Mitsubishi Chemical Examples include various commercially available products such as diamond ions, and those in which a ligand that adsorbs noble metal ions is supported on an appropriate insoluble carrier. The ligand that adsorbs the noble metal ion is not particularly limited, but a compound having a sulfide group or an amino group is preferably used.

  In the adsorbent, any insoluble carrier for immobilizing a ligand that adsorbs noble metal ions can be used without particular limitation as long as it is insoluble in water. For example, styrene polymers such as polystyrene or crosslinked polystyrene, polyolefins such as polyethylene or polypropylene, poly (halogenated olefins) such as polyvinyl chloride or polytetrafluoroethylene, nitrile polymers such as polyacrylonitrile, polymethyl methacrylate, poly Synthetic polymer carriers such as (meth) acrylic acid polymers such as ethyl methacrylate, natural polymer carriers such as cellulose, agarose and dextran, or activated carbon, silica gel, diatomaceous earth, hydroxyapatite, alumina, titanium oxide, magnesia, polysiloxane An inorganic carrier such as

  Cross-linked polystyrene means monovinyl aromatic compounds such as styrene, divinylbenzene, vinylxylene, vinylnaphthalene and polyvinylaromatic compounds such as divinylbenzene, divinyltoluene, divinylxylene, divinylnaphthalene, trivinylbenzene, bisvinyldiphenyl, bisbiphenylethane, etc. It is mainly composed of a cross-linked copolymer with a compound, and these copolymers may be copolymerized with methacrylic acid esters such as glycerol methacrylate and ethylene glycol dimethacrylate.

  Of these insoluble carriers, silica gel and alumina are preferable from the viewpoint of price and availability.

  The shape of the insoluble carrier is generally used as a separation substrate such as spherical (eg, spherical particles), granular, fibrous, granular, monolithic column, hollow fiber, membrane (eg, flat membrane), etc. The shape can be used and is not particularly limited. Of these, spherical, membranous, granular and fibrous ones are preferred. Granular particles are particularly preferred because the volume of use can be set arbitrarily when used in the column method or batch method.

  As the particle size of the insoluble carrier, those having an outer diameter of 1-1000 μm can be usually used, but those of 10-300 μm are preferable from the viewpoint of precious metal ion adsorption performance and ease of handling.

  The insoluble carrier can be used without any problem even if it is porous or nonporous. However, the porous carrier is preferred because it has a wide effective area for adsorbing noble metal ions.

  The method for immobilizing the ligand that adsorbs the noble metal ion on the insoluble carrier is not particularly limited, and examples thereof include a method of physically adsorbing and supporting the ligand and a method of immobilization by chemical bonding.

  A commercially available noble metal ion adsorbent and a noble metal ion adsorbent having an arbitrary ligand immobilized on a carrier are not limited, but can be used in a column method or a batch method. Can be used on the floor.

  The noble metal ion adsorbent adsorbs noble metal ions by solid-liquid contact with a solution in which the noble metal ions are dissolved. Next, the noble metal ions are desorbed from the adsorbent by bringing the adsorbent separated from the solution in which the noble metal ions are dissolved into solid-liquid contact with the noble metal ion desorbing agent containing the sulfide compound represented by the general formula (1). Elute into the liquid phase.

  Use of a noble metal ion desorbing agent containing a sulfide compound represented by the general formula (1) in a method for desorbing a noble metal ion comprising using a noble metal ion desorbing agent containing the sulfide compound represented by the general formula (1) The amount is not particularly limited, but it is preferable to adjust the amount so as to be at least twice as much as the amount of noble metal ions adsorbed on the adsorbent.

  In the method for desorbing noble metal ions characterized by using a noble metal ion desorbing agent containing a sulfide compound represented by the general formula (1), the operation for desorbing the noble metal ions is usually carried out under normal pressure or in the atmosphere. However, it can also be carried out under pressurized or reduced pressure conditions or in the presence of an inert gas. The desorption operation of the noble metal ions is usually performed in a temperature range of 4 to 150 ° C, but a temperature range of 10 to 50 ° C is more preferable.

  The method for recovering the noble metal from the desorption solution obtained using the noble metal ion desorption agent containing the sulfide compound represented by the general formula (1) is not particularly limited, but the desorption obtained by the desorption method for the noble metal ions There is a method of precipitating a noble metal by reducing the solution as it is or after neutralization, and collecting the precipitated noble metal by filtration.

  As the reduction method of the noble metal ion desorption solution, various methods can be used depending on the purpose and equipment, and examples thereof include an electrolytic reduction method by electrolysis and a chemical reduction method in which a reducing agent such as hydrazine is added. .

  The reduction treatment operation of the noble metal ion desorption solution is usually carried out under normal pressure or air, but can also be carried out under pressurized or reduced pressure conditions or under an inert gas atmosphere. This reduction treatment operation is usually performed in a temperature range of 4 to 100 ° C, but a temperature range of 10 to 80 ° C is more preferable.

  Examples of the filtration method for the noble metal precipitate generated by the reduction treatment of the noble metal ion desorption solution include a method using a membrane filter, filter paper, filter cloth, glass filter, etc., but filtration with a membrane filter or filter paper is easy because of operation. Is preferred.

  According to the present invention, by using the noble metal ion desorbent containing the sulfide compound represented by the general formula (1), the noble metal ions adsorbed on the adsorbent can be reduced while minimizing chemical damage to the adsorbent. It can be efficiently desorbed, and a highly pure noble metal can be recovered very simply from the obtained desorption liquid. Therefore, by utilizing the present invention, the options for the precious metal recycling process can be expanded and the recycling process can be shortened.

  The present invention will be described in detail below, but the present invention is not limited to these examples.

  The palladium ion concentration and metal palladium purity in the aqueous solution were measured with an ICP emission spectroscopic analyzer (OPTIMA 3300 DV, manufactured by Perkin Elmaer).

  The sulfur content was measured by ion chromatography. Ion chromatography measurements were performed with the following pretreatment, equipment and conditions.

Pretreatment: A sample was introduced into an automatic sample combustion apparatus (AQF-100, Mitsubishi Chemical Analytic), and SO ₄ ²⁻ produced by combustion was collected in an adsorbent (internal standard material PO ₄ ⁻ ).

Measuring device: IC-2001 made by Tosoh
Separation column: TSKgel Super IC-AP (4.6 mmΦ × 150 mm)
Detector: Electrical conductivity detector Eluent: 2.7 mmol / L NaHCO ₃ + 1.8 mmol / L Na ₂ CO ₃
Synthesis Example 1 Synthesis of Palladium Adsorbent A palladium adsorbent represented by the general formula (2) schematically including a bond of a functional group to a support was synthesized according to the following method.

ディーン・スターク装置付き５００ｍＬナス型フラスコに、シリカゲル（富士シリシア化学製、商品名：ＰＳＱ６０Ｂ） １００ｇ、水 ５ｇ、オルト−キシレン ２００ｇを量り取り、６０℃で激しく攪拌しながら、予め調製しておいた３−アミノプロピルトリメトキシシラン ３５．９ｇとオルト−キシレン ３５．９ｇの混合溶液を１０分間かけて滴下した後、９０℃まで昇温し、１時間攪拌した。次に、１１０℃まで昇温し、１．５時間攪拌した。ディーン・スターク装置に溜まったメタノール、オルト−キシレン、水の混合溶液は系外に廃棄した。

In a 500 mL eggplant type flask equipped with a Dean-Stark apparatus, 100 g of silica gel (manufactured by Fuji Silysia Chemical, trade name: PSQ60B), 100 g of water, 5 g of water, and 200 g of ortho-xylene were weighed and prepared in advance with vigorous stirring at 60 ° C. After dropping a mixed solution of 35.9 g of 3-aminopropyltrimethoxysilane and 35.9 g of ortho-xylene over 10 minutes, the temperature was raised to 90 ° C. and stirred for 1 hour. Next, it heated up to 110 degreeC and stirred for 1.5 hours. The mixed solution of methanol, ortho-xylene and water collected in the Dean-Stark apparatus was discarded outside the system.

  Next, 0.005 g of 3,5-bis (trifluoromethyl) phenylboronic acid and 48.1 g of (ethylthio) acetic acid were weighed and heated to reflux for 24 hours with vigorous stirring. After cooling to room temperature, the reaction mixture was filtered, and the collected solid was washed with methanol to obtain a palladium adsorbent. The obtained palladium adsorbent had a sulfur content of 4.5% by weight.

Example 1
1 g of the palladium adsorbent obtained in Synthesis Example 1 was added to 80 mL of a 1 mol / L hydrochloric acid solution containing 1000 mg / L of palladium ions, and the mixture was stirred at room temperature for 2 hours. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, and the adsorption amount of palladium ion was computed with 69.2 mg per 1 g of adsorption agent from the palladium ion concentration of the filtrate. Next, the adsorbent collected by filtration was washed with water and dried. 20 mg of the dried adsorbent was added to 10 mL of a desorbent prepared as an aqueous solution (pH 2) having a thiodiglycolic acid concentration of 5% by weight, and stirred at room temperature for 1 hour. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, As a result of calculating | requiring the desorption amount of palladium ion from the palladium ion density | concentration of a filtrate, the desorption rate of palladium ion was 59%.

Example 2
In Example 1, instead of 10 mL of the desorbent prepared as an aqueous solution (pH 2) having a thiodiglycolic acid concentration of 5% by weight, sodium hydroxide was added to adjust the pH to 7 so that the thiodiglycolic acid concentration was 5% by weight. The same procedure as in Example 1 was performed except that 10 mL of the desorbent prepared as an aqueous solution was used. The desorption rate of palladium ions was 86%.

Example 3
1 g of Amberlite IRA96SB made by Organo was added to 60 mL of 1 mol / L hydrochloric acid solution containing 1000 mg / L of palladium ions, and stirred at room temperature for 2 hours. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, and the adsorption amount of palladium ion was computed with 60.0 mg per 1 g of adsorption agent from the palladium ion density | concentration of a filtrate. Next, the adsorbent collected by filtration was washed with water and dried. 20 mg of the dried adsorbent was added to 10 mL of a desorbent prepared as an aqueous solution (pH 2) having a thiodiglycolic acid concentration of 5% by weight, and stirred at room temperature for 1 hour. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, As a result of calculating | requiring the desorption amount of palladium ion from the palladium ion density | concentration of a filtrate, the desorption rate of palladium ion was 75%.

Example 4
1 g of Diaion SA10A manufactured by Mitsubishi Chemical was added to 60 mL of a 1 mol / L hydrochloric acid solution containing 1000 mg / L of palladium ions, and stirred at room temperature for 2 hours. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, and the adsorption amount of palladium ion was computed with 60.0 mg per 1 g of adsorption agent from the palladium ion density | concentration of a filtrate. Next, the adsorbent collected by filtration was washed with water and dried. 20 mg of the dried adsorbent was added to 10 mL of a desorbent prepared as an aqueous solution (pH 2) having a thiodiglycolic acid concentration of 5% by weight, and stirred at room temperature for 1 hour. Then, it filtered using the membrane filter with the hole diameter of 0.45 micrometer, As a result of calculating | requiring the desorption amount of palladium ion from the palladium ion density | concentration of a filtrate, the desorption rate of palladium ion was 53%.

Example 5
After 0.1 g of the palladium separating agent synthesized in Synthesis Example 1 was dispersed in water, it was packed in a glass column (inner diameter 5 mm, length 100 mm). Adsorption of metal ions was performed by passing 2 mL of a 1 mol / L hydrochloric acid solution containing 10,000 mg / L of palladium ions from the top of the column at a flow rate of 36 mL / Hr. From the palladium ion concentration in the column effluent, the amount of palladium ion adsorbed was calculated to be 77.0 mg / g adsorbent. Next, the column was washed by passing 20 mL of water (flow rate: 36 mL / Hr), and then the desorbent prepared as an aqueous solution having a thiodiglycolic acid concentration of 5% by weight was passed through the column from the top at a flow rate of 36 mL / Hr. Then, desorption of metal ions was performed. From the palladium ion concentration of the column effluent, the desorption amount of palladium ion was calculated as 72.9 mg per 1 g of the adsorbent. From the above results, the desorption rate of palladium ions was 95%.

Example 6
In Example 5, in place of 10 mL of the desorbent prepared as an aqueous solution having a thiodiglycolic acid concentration of 5% by weight, Example 1 except that 10 mL of the desorbent prepared as an aqueous solution having a concentration of 5% by weight of (ethylthio) acetic acid was used The same was done. The desorption rate of palladium ions was 58%.

Example 7
In Example 5, except that 10 mL of the desorbent prepared as an aqueous solution having a concentration of 5% by weight of (ethylenedithio) diacetic acid was used instead of 10 mL of the desorbent prepared as an aqueous solution having a thiodiglycolic acid concentration of 5% by weight. 1 was performed. The desorption rate of palladium ions was 89%.

Example 8
Sodium hydroxide was added to an aqueous solution containing 1000 mg / L concentration of palladium ions and 5 wt% concentration of thiodiglycolic acid to adjust the pH to 7. Next, 0.45 g of hydrazine monohydrate was added, and the mixture was stirred at 50 ° C. for 2 hours. After cooling to room temperature, the precipitated palladium black was filtered, and the metal palladium collected by filtration was washed with 1 mol / L hydrochloric acid. As a result of obtaining the palladium deposition rate from the palladium concentration of the filtrate, the palladium deposition rate was 99.9%. The resulting palladium black had a sulfur content of 1.8% by weight.

Example 9
An aqueous solution containing 1000 mg / L palladium ion and 3% by weight thiodiglycolic acid was used as the catholyte of an acrylic electrolytic cell partitioned by a cation exchange membrane (Nafion 117), and 0.02 mol / L hydrochloric acid aqueous solution was used as the anolyte. Then, electrolytic treatment was carried out using the cathode current density and the electrolysis time as variables using true casting for the cathode and carbon for the anode.

Deposition of palladium black was observed in the cathode chamber. The cathode current density was 1 A / dm ² for 2 hours, 3.5 A / dm ² and 5 A / dm ² for 1 hour, and the palladium deposition rate was 99.5% or more. It was.

Example 10
Electrolysis was carried out under the same conditions as in Example 9, except that a solution having the same composition as the catholyte of Example 9 was supplied to a so-called one-chamber electrolytic cell without an ion exchange membrane and the cathode current density was 3.5 A / dm ^2. Was done. As a result, the palladium deposition rate was about 100% after 1 hour.

Comparative Example 1
In Example 8, except that 5% by weight of thiourea was used instead of 5% by weight of thiodiglycolic acid, the result was the same as that of Example 8. As a result, the palladium deposition rate was as high as 99.7%. However, the sulfur content of the obtained palladium black was 24.9% by weight, which was a result that a large amount of sulfur was mixed in the palladium black as compared with Example 8.

Comparative Example 2
In Example 10, the same procedure was performed as in Example 10 except that 3% by weight of thiourea was used instead of 3% by weight of thiodiglycolic acid. As a result, a large amount of insoluble matter was precipitated in the solution. Palladium black could not be obtained with high purity.

  The noble metal ion desorbing agent containing the sulfide compound of the present invention can efficiently desorb noble metal ions from various adsorbents, and further, by reducing the obtained noble metal ion desorbing solution, the noble metal ions can be removed very easily. It can be recovered. For this reason, utilization in the resource recycling field | area which collect | recovers and reuses the expensive noble metal currently used for the discarded industrial catalyst, the automobile exhaust gas purification catalyst, or an electric appliance etc. is anticipated.

Claims (5)

A noble metal ion desorption agent comprising a sulfide compound represented by the following general formula (1).

(In the formula, R represents a methyl group, an ethyl group, a vinyl group, a linear, branched or cyclic hydrocarbon group having 3 to 8 carbon atoms, an aromatic hydrocarbon group having 6 to 14 carbon atoms, a carboxyl methyl group, and a carbamoylmethyl group. Group, 4-carboxyl-3-thiabutyl group, or 4-carbamoyl-3-thiabutyl group, and X represents a hydroxyl group or a primary amino group.) The noble metal ion desorbing agent according to claim 1, wherein the sulfide compound is thiodiglycolic acid. A method for desorbing a noble metal ion, comprising contacting the noble metal ion desorbing agent according to claim 1 or 2 with an adsorbent that has adsorbed the noble metal ion to desorb the noble metal ion. A method for recovering a noble metal, comprising reducing the solution containing the noble metal ion obtained by the method for desorbing a noble metal ion according to claim 3 to recover the noble metal. The method for recovering a noble metal according to claim 4, wherein the noble metal ion is palladium ion, and the noble metal is palladium.