Recovery kit, recovery method and recovery apparatus for noble metal particles

Abstract

Provided is a noble metal particle recovery kit which can be used repeatedly and which can recover, through a simple method, noble metal particles from a solution in which noble metals have been dissolved.　The noble metal particle recovery kit according to the present disclosure contains the following adsorbent and the following reducing agent. The adsorbent has a function of adsorbing noble metal ions in a solution in which the noble metals are dissolved, when the adsorbent is brought into contact with the solution. The reducing agent has a function of reducing the noble metal ions to be desorbed from the adsorbent, and forming particles, when the adsorbent is brought into contact with the noble metal ions adsorbed onto the adsorbent. The adsorbent is preferably an ester having a sugar skeleton, and in particular, is preferably a polysaccharide acylate.

Description

Precious metal particle recovery kit, recovery method, and recovery device

[0001] This disclosure relates to a precious metal particle recovery kit, a recovery method, and a recovery device. This disclosure claims priority to Japanese Patent Application No. 2021-109237, filed in Japan on June 30, 2021, the contents of which are incorporated herein by reference.

[0002] Precious metals such as gold, platinum, and palladium are extremely important materials in cutting-edge fields such as electronic components, semiconductors, catalysts essential for purifying automobile exhaust gases, liquid crystal glass, and LEDs, but they are very expensive. Furthermore, waste electrical and electronic equipment (e-waste) contains large amounts of precious metals, sometimes more than 10 times the amount contained in their ores. Therefore, there is a need for inexpensive and simple methods to separate, recover, and reuse precious metals from waste electrical and electronic equipment.

[0003] Patent Document 1 describes a method for recovering precious metals from ash by using cellulose that has been dehydrated, condensed, and cross-linked using concentrated sulfuric acid as an adsorbent, adsorbing precious metal ions dissolved in a solution onto the adsorbent, and then incinerating the adsorbent. However, this method has problems in that the adsorbent cannot be reused and a large amount of thermal energy is required for incineration.

[0004] Patent Document 2 describes a method of recovering precious metal ions by adsorbing them onto an adsorbent, then stripping the adsorbed precious metal ions and reducing them to precipitate precious metal particles. However, this method requires a large number of steps, which results in a problem of high costs.

[0005] JP 2012-170950 A JP 2014-084495 A

[0006] Therefore, an object of the present disclosure is to provide a reusable precious metal particle recovery kit that can easily recover precious metal particles from a solution that the precious metal has been dissolved in. Another object of the present disclosure is to provide a precious metal particle recovery method that easily recovers precious metal particles from a solution that the precious metal has been dissolved in. Another object of the present disclosure is to provide a precious metal particle recovery device that easily recovers precious metal particles from a solution that the precious metal has been dissolved in.

[0007] As a result of intensive research to solve the above problems, the present inventors have found that by using an adsorbent that adsorbs precious metal ions in a solution when brought into contact with the solution, and a reducing agent that reduces the precious metal ions adsorbed on the adsorbent to desorb them from the adsorbent and turn them into particles when brought into contact with the precious metal ions, it is possible to recover precious metal particles with a small number of processes, and the adsorbent after desorbing the adsorbed precious metal ions can be reused to adsorb precious metal ions, i.e., it can be used repeatedly. The present disclosure has been completed based on these findings.

[0008] That is, the present disclosure provides a precious metal particle recovery kit including the following adsorbent and the following reducing agent: Adsorbent: When contacted with a solution in which a precious metal is dissolved, it has the function of adsorbing the precious metal ions in the solution. Reducing agent: When contacted with the precious metal ions adsorbed to the adsorbent, it has the function of reducing the precious metal ions, desorbing them from the adsorbent, and forming them into particles.

[0009] The present disclosure also provides the precious metal particle recovery kit, wherein the adsorbent is an ester having a sugar skeleton.

[0010] The present disclosure also provides the precious metal particle recovery kit, wherein the adsorbent is a polysaccharide acylate.

[0011] The present disclosure also provides the precious metal particle recovery kit, wherein the adsorbent is a separation membrane or a column packing material.

[0012] The present disclosure also provides a method for recovering precious metal particles, comprising the following steps: Step 1: bringing an adsorbent into contact with a solution in which a precious metal has been dissolved, thereby allowing the adsorbent to adsorb the precious metal ions in the solution; and Step 2: bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, thereby reducing the precious metal ions and causing them to be desorbed from the adsorbent and form particles.

[0013] The present disclosure also provides a precious metal particle recovery device comprising the following adsorption means and reduction means: Adsorption means: means for bringing an adsorbent into contact with a solution in which a precious metal is dissolved, thereby causing the adsorbent to adsorb the precious metal ions in the solution; Reduction means: means for bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, thereby reducing the precious metal ions and causing them to be desorbed from the adsorbent and form particles.

[0014] By using the precious metal particle recovery kit of the present disclosure, it is possible to recover precious metals dissolved in a solution by forming them into particles (or metallizing them) with fewer processes than in the past. Furthermore, by using the kit of the present disclosure, it is possible to directly convert precious metal ions adsorbed on an adsorbent into precious metal particles, and since the precious metal ions are adsorbed on an adsorbent and reduced in a dense state, rather than by reducing the precious metal ions present in a solution to form particles, they aggregate and form particles, resulting in particles with a large particle size.

[0015] Furthermore, the precious metal particle recovery kit of the present disclosure can be reused. Furthermore, by using the precious metal particle recovery kit, precious metal particles can be recovered without using methods that require a large amount of thermal energy, such as incineration. Therefore, the precious metal particle recovery kit has the effect of promoting the reuse of valuable resources while reducing the burden on the environment.

[0016] 1A and 1B are diagrams showing SEM measurement results of gold particles obtained in Examples, Au-mapping measurement results by EDS of gold particles obtained in Examples, and C-mapping measurement results by EDS of gold particles obtained in Examples.

[0017] [Precious Metal Particle Recovery Kit] The precious metal particle recovery kit of the present disclosure includes the following adsorbent and the following reducing agent: Adsorbent: When contacted with a solution in which a precious metal is dissolved, it has the function of adsorbing the precious metal ions in the solution. Reducing agent: When contacted with the precious metal ions adsorbed to the adsorbent, it has the function of reducing the precious metal ions, desorbing them from the adsorbent, and turning them into particles.

[0018] The noble metal particles in the present disclosure include zero-valent noble metal atoms or aggregates of the zero-valent noble metal atoms. The zero-valent noble metal atoms may be dispersed in a solution to form a colloid.

[0019] The precious metal particle recovery kit is a set of materials for reducing precious metal ions in a solution to zero-valent precious metal atoms and forming particles. The kit can be used to easily recover precious metals dissolved in a solution. The kit includes at least the adsorbent and reducing agent as components. The kit may also include other components as needed, in addition to the adsorbent and reducing agent.

[0020] The use of the noble metal particle recovery kit makes it possible to recover gold dissolved in a solution simply and efficiently, and therefore the noble metal particle recovery kit is preferably a gold particle recovery kit.

[0021] (Adsorbent) The adsorbent has a function of adsorbing precious metal ions in a solution to the adsorbent when the adsorbent is brought into contact with the solution in which the precious metal is dissolved.

[0022] The adsorbent is a compound that has the function of adsorbing precious metal ions in a solution, and examples thereof include esters having a sugar skeleton (compounds having a sugar skeleton, in which at least one of the hydroxyl groups of the compound is esterified; hereinafter, these may be referred to as "sugar esters").

[0023] The sugar ester is preferably a polysaccharide ester.

[0024] The polysaccharide is a compound formed by polymerizing one or more monosaccharides via glycosidic bonds, and examples of the monosaccharides include glucose, mannose, xylose, galactose, N-acetylglucosamine, N-acetylgalactosamine, and fucose.

[0025] Examples of the polysaccharides include cellulose, amylose, amylopectin, dextran, hemicellulose, chitin, glycogen, agarose, and pectin.

[0026] Of the polysaccharides, those that have low solubility in an acidic aqueous solution are preferred, since they can be easily separated by filtration or the like after adsorbing the precious metal ions.

[0027] The polysaccharides include, among others, (homo)polymers of glucose such as cellulose, amylose, and dextran, more specifically, compounds formed by polymerizing only glucose (particularly α-glucose or β-glucose) via glycosidic bonds, and have the molecular formula [(C ６ H １０ O ５ ) ｎ (where n represents the number of repeating glucose units and is an integer of 2 or more) is preferred.

[0028] The polysaccharide ester includes a compound formed by a condensation reaction of one or more hydroxyl groups of the polysaccharide with at least one oxoacid selected from carboxylic acid, sulfuric acid, hydroxy acid, phosphoric acid, and the like.

[0029] Of the polysaccharide esters, polysaccharide acylates, which are condensation reaction products of polysaccharides and carboxylic acids, are preferred because they have an appropriate adsorptivity for precious metal ions, and the adsorbed precious metal ions are easily reduced and released by contact with a reducing agent, and they have low solubility in acidic aqueous solutions, which inhibits swelling in the aqueous solution, resulting in excellent handleability.

[0030] The polysaccharide acylate has the molecular formula [(C ６ H １０ O ５ ) ｎ In the present invention, at least a part of the hydroxyl groups of the compound represented by the formula (1) is esterified with an acyl group (RC(═O) group).

[0031] R in the RC(=O) group is a hydrocarbon group. The hydrocarbon group includes an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and groups formed by combining these groups.

[0032] The hydrocarbon group is preferably an aliphatic hydrocarbon group (particularly an alkyl group) having 1 to 10 carbon atoms (preferably 1 to 5 carbon atoms), such as a methyl, ethyl, propyl, butyl, pentyl, or hexyl group; or an aromatic hydrocarbon group, such as a phenyl group.

[0033] The polysaccharide acylate is particularly preferably a cellulose acylate having a repeating unit represented by the following formula (1) or an amylose acylate having a repeating unit represented by the following formula (2): In the following formulas (1) and (2), X may be the same or different and represent an acyl group (RC(=O) group, where R is the same as above) or a hydrogen atom, except that all Xs are hydrogen atoms.

[0034]

[0035] Examples of the cellulose acylate include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

[0036] Examples of the amylose acylate include amylose acetate, amylose propionate, and amylose butyrate.

[0037] The total degree of ester group substitution of the sugar ester (or the total degree of acyl group substitution of the polysaccharide acylate) is, for example, 1.0 to 3.0, preferably 2.0 to 3.0, and particularly preferably 2.2 to 2.7. A sugar ester (or a polysaccharide acylate) having the above-mentioned degree of substitution has an appropriate adsorptivity for precious metals, and therefore can efficiently adsorb precious metal ions when brought into contact with a solution in which the precious metal is dissolved. After adsorption, when brought into contact with a reducing agent, the adsorbed precious metal ions can be efficiently particulated and released.

[0038] The total degree of acetyl substitution of cellulose acetate among the sugar esters can be measured by NMR measurement according to the following method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)): 1. Unsubstituted hydroxyl groups of a cellulose acetate sample are propionylated with propionic anhydride in pyridine. 2. The obtained sample is dissolved in deuterated chloroform, １３3. Measure the C-NMR spectrum. The carbon signals of the acetyl group appear in the region from 169 ppm to 171 ppm in the order of 2-, 3-, and 6-positions from the high magnetic field, and the carbonyl carbon signals of the propionyl group appear in the same order in the region from 172 ppm to 174 ppm. The degree of acetyl substitution at the 2-, 3-, and 6-positions of the glucose ring in the original cellulose acetate can be determined from the abundance ratio of acetyl groups and propionyl groups at the corresponding positions.

[0039] The weight average molecular weight (Mw) of the sugar ester (or polysaccharide acylate) is, for example, 100,000 to 1,000,000, preferably 100,000 to 500,000, and particularly preferably 100,000 to 300,000.

[0040] The polydispersity (molecular weight distribution obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn): Mw / Mn) of the sugar ester (or polysaccharide acylate) is, for example, 2 to 10, preferably 2 to 8, and particularly preferably 2 to 5.

[0041] The number average molecular weight (Mn), weight average molecular weight (Mw), and dispersity (Mw / Mn) of the sugar ester (or polysaccharide acylate) can be determined by a known method using gel permeation chromatography.

[0042] The shape of the sugar ester (or polysaccharide acylate) is not particularly limited, but among them, powder or spherical shapes (average particle size, for example, about 0.5 to 1 μm), or fibrous shapes [particularly, fibrous shapes obtained by dry spinning such as electrospinning and having a single fineness of, for example, 0.05 to 10 denier (preferably 0.5 to 5.0 denier, particularly preferably 0.5 to 1.0 denier) and a total fineness of, for example, 600 to 60,000 denier (particularly preferably 3,000 to 30,000 denier)] are preferred in terms of their excellent adsorption of precious metals.

[0043] The mode of use of the adsorbent is not particularly limited, but examples thereof include use as a separation membrane (or filtration membrane) and use as a column packing material.

[0044] Examples of methods for using the adsorbent as a separation membrane include a method in which a fibrous adsorbent is used to form a woven or nonwoven fabric and use this as a separation membrane, and a method in which the adsorbent is attached to the surface of a separation membrane formed from a component other than the adsorbent.

[0045] Examples of a method for using the adsorbent as a column packing include using a powder, spherical, or pellet-shaped adsorbent (obtained by shredding a fibrous material), or a particle, powder, or fiber formed from a component other than the adsorbent, to which the adsorbent is attached, as a column packing. The column packing is used by filling a tube to form a column.

[0046] Therefore, the precious metal particle recovery kit may include at least one selected from a separation membrane made of an adsorbent that has the function of adsorbing precious metal ions in a solution to the adsorbent when the adsorbent is brought into contact with the solution in which the precious metal is dissolved, a separation membrane containing the adsorbent, a column filler made of the adsorbent, a column filler containing the adsorbent, and a column filled with the adsorbent, and a reducing agent.

[0047] The precious metal ions adsorbed to the adsorbent are easily reduced to zero-valent precious metal atoms by using a reducing agent described below, and are then granulated and released. The adsorbent from which the precious metal ions have been released can be reused as an adsorbent in the precious metal particle recovery kit.

[0048] (Reducing Agent) The reducing agent has a function of reducing and desorbing the precious metal ions adsorbed on the adsorbent when the reducing agent is brought into contact with the adsorbent having precious metal ions adsorbed thereon, thereby precipitating precious metal particles. The reducing agent can be used alone or in combination of two or more.

[0049] Examples of the reducing agent include compounds having at least one group selected from a hydroxyl group, a thiol group, a carboxyl group, and a group containing a nitrogen atom.

[0050] Examples of the compound having a hydroxyl group include alcohols such as 1,4-butanediol, glycerol, and polyethylene glycol; phenols such as hydroquinone; monosaccharides such as glucose; and polysaccharides such as cellulose, carboxymethylcellulose, cyclodextrin, chitin, and chitosan.

[0051] Examples of the compound having a thiol group include benzenethiol, methanethiol, ethanethiol, propanethiol, cysteine, 2-mercaptoethanol, and thioglycerol.

[0052] Examples of the compound having a carboxyl group include monocarboxylic acids such as formic acid, acetic acid, propionic acid, and butyric acid; polycarboxylic acids such as oxalic acid, malonic acid, and succinic acid; hydroxymonocarboxylic acids such as lactic acid and glycolic acid; hydroxypolycarboxylic acids such as citric acid and tartaric acid; aminocarboxylic acids such as N,N-dimethylaminoacetic acid and N,N-dimethylaminopropionic acid; and lactones such as ascorbic acid.

[0053] Examples of the compound having a group containing a nitrogen atom include amines such as methylamine, ethylamine, propylamine, monoethanolamine, dimethylamine, diethylamine, N-methylethanolamine, diethanolamine, dimethylethylamine, N-methyldiethanolamine, and N,N-dimethylethanolamine; and amides such as acetamide, propionic acid amide, N-methylformamide, N-methylacetamide, N-methylpropionic acid amide, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0054] The reducing agent also includes aldehydes such as formaldehyde and acetaldehyde.

[0055] As the reducing agent, a compound having two or more groups selected from hydroxyl groups, thiol groups, carboxyl groups, and groups containing a nitrogen atom in one molecule is preferred, and a compound having three or more groups in one molecule is particularly preferred, in that the reducing agent has coordination properties with precious metal ions, coordinates with precious metal ions adsorbed on the adsorbent to form a complex, reduces the precious metal ions, and can form precious metal particles with excellent stability.

[0056] As the reducing agent, a compound that brings the pH of the reaction system in contact with the adsorbent to 10 or less (preferably pH 10 to 2, more preferably pH 9 to 3) is preferred, as it can convert the precious metal ions adsorbed on the adsorbent into particles while suppressing decomposition of the adsorbent, and a compound having a hydroxyl group and / or a carboxyl group is preferred.

[0057] As the reducing agent, hydroxycarboxylic acids are particularly preferred, and hydroxypolycarboxylic acids are particularly preferred.

[0058] [Method for recovering precious metal particles] The method for recovering precious metal particles includes the following steps: Step 1: Bringing an adsorbent into contact with a solution in which a precious metal has been dissolved, thereby allowing the adsorbent to adsorb the precious metal ions in the solution; Step 2: Bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, thereby reducing the precious metal ions and causing them to be desorbed from the adsorbent and form particles.

[0059] (Step 1) Step 1 is a step of bringing an adsorbent into contact with a solution in which a noble metal is dissolved (hereinafter, sometimes referred to as a "metal solution"), and allowing the adsorbent to adsorb noble metal ions in the solution.

[0060] The metal solution is, for example, an aqueous solution in which a noble metal is dissolved. The noble metal dissolved in the solution is, for example, at least one selected from gold, silver, platinum, copper, cobalt, iridium, and palladium. The noble metal is dissolved in the solution (e.g., aqueous solution) in the form of ions.

[0061] As the adsorbent, the adsorbent in the noble metal particle recovery kit can be suitably used.

[0062] The amount of the adsorbent used is, for example, 0.1 to 5.0 g, preferably 0.5 to 2.0 g, per liter of metal solution having a metal element concentration of 100 ppm by weight.

[0063] The method for contacting the adsorbent with the metal solution is not particularly limited, and the adsorbent may be immersed in the metal solution, or the metal solution may be passed through a module equipped with the adsorbent. For example, when the adsorbent is a separation membrane, a method can be used in which the metal solution is passed through a module equipped with the separation membrane. Furthermore, when the adsorbent is a column packing material, a method can be used in which the adsorbent is packed into a tube to form a column, and the metal solution is passed through the formed column.

[0064] The metal solution when brought into contact with the adsorbent has a pH of, for example, greater than 0. The upper limit of the pH is, for example, 10. In particular, adjusting the pH of the metal solution to greater than 0 and equal to or less than 3 (preferably 1 or more and 3 or less, particularly preferably 1 or more and 2 or less) is preferred in terms of improving the adsorption rate of precious metal ions to the adsorbent.

[0065] The time for contacting the adsorbent with the metal solution is, for example, 10 minutes or more, preferably 30 to 300 minutes, and the solution temperature when contacting the adsorbent with the metal solution is, for example, 5 to 60°C, preferably 5 to 30°C.

[0066] The reaction in step 1 can be carried out by any method such as a batch method, a semi-batch method, or a continuous method.

[0067] (Step 2) Step 2 is a step of bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, reducing the precious metal ions, causing them to be desorbed from the adsorbent, and forming particles.

[0068] As the reducing agent, the reducing agent in the noble metal particle recovery kit can be suitably used.

[0069] The amount of the reducing agent used is, for example, 0.1 to 0.5 parts by weight, preferably 0.1 to 0.3 parts by weight, per part by weight of the adsorbent.

[0070] Examples of a method for contacting a reducing agent with precious metal ions adsorbed on an adsorbent include immersing the adsorbent with precious metal ions in a solution containing a reducing agent. When the adsorbent is a separation membrane, a method of immersing the separation membrane with precious metal ions adsorbed in a solution containing a reducing agent, or a method of placing the separation membrane with precious metal ions adsorbed in a module and passing a solution containing a reducing agent through the module, can be used. When the adsorbent is a column packing material, a method of passing a solution containing a reducing agent through a column packed with column packing material containing precious metal ions adsorbed, can be used.

[0071] The temperature when the reducing agent is brought into contact with the precious metal ions adsorbed on the adsorbent is, for example, 80 to 120° C. The contact time is, for example, about 10 to 30 minutes.

[0072] The reaction in step 2 can be carried out by any method such as a batch method, a semi-batch method, a continuous method, etc. The reaction in step 2 may be carried out in a system different from that in step 1, or may be carried out in the same system.

[0073] Through step 2, a solution containing noble metal particles (preferably a colloid in which noble metal particles are dispersed in a solution) is obtained.

[0074] The solution containing the precious metal particles thus obtained may be subjected to methods such as centrifugation, ultrafiltration, evaporation, concentration, or a method of binding the particles to a fixing material and recovering the particles, to separate the precious metal particles.

[0075] The particle diameter of the noble metal particles is, for example, 50 nm or more, preferably 70 nm or more, particularly preferably 100 nm or more, and most preferably 120 nm or more.

[0076] According to the precious metal particle recovery method, the precious metal adsorbed to the adsorbent in step 1 can be easily granulated and released by treating it with a reducing agent in step 2. Therefore, the adsorbent from which the precious metal has been released can be reused as an adsorbent in step 1. Conventionally, the precious metal adsorbed to the adsorbent has been recovered by incinerating the adsorbent, but in the precious metal particle recovery method, the adsorbent is not incinerated and can be reused, thereby reducing material costs. In addition, the energy costs for incineration can also be reduced.

[0077] According to the method for recovering precious metal particles, it is possible to recover precious metals (particularly gold) dissolved in a solution simply and efficiently. Therefore, the method for recovering precious metal particles is particularly preferably a method for recovering gold particles.

[0078] [Precious Metal Particle Recovery Apparatus] The precious metal particle recovery apparatus is an apparatus for recovering precious metal particles by the precious metal particle recovery method.

[0079] The precious metal particle recovery device includes the following adsorption means and reduction means: Adsorption means: A means for bringing an adsorbent into contact with a solution in which a precious metal is dissolved, thereby causing the adsorbent to adsorb the precious metal ions in the solution; Reduction means: A means for bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, thereby reducing the precious metal ions and causing them to be desorbed from the adsorbent and become particles.

[0080] The precious metal particle recovery device may include, for example, an adsorption unit and a reduction unit as described below. Adsorption unit: A unit having a function of bringing an adsorbent into contact with a solution in which a precious metal is dissolved, and causing the adsorbent to adsorb the precious metal ions in the solution. Reduction unit: A unit having a function of bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, reducing the precious metal ions, and desorbing them from the adsorbent to form particles.

[0081] The adsorption unit and the reduction unit may be separate units, or may be a single unit having both the function of adsorbing the precious metal ions and the function of reducing the adsorbed precious metal ions.

[0082] The adsorption means or adsorption unit may include, for example, a separation membrane made of an adsorbent that has the function of causing the adsorbent to adsorb precious metal ions in a solution when the adsorbent is brought into contact with the solution, or a separation membrane containing the adsorbent, a column packing made of the adsorbent, or a column packing containing the adsorbent, or a column packed with the packing. The adsorption means or adsorption unit may further include a stirring device.

[0083] The reduction means or reduction unit may include, for example, a reducing agent dropping device, a stirring device, a reflux device, and the like.

[0084] The precious metal particle recovery device may have other configurations (means or units) as necessary, and may, for example, be equipped with a separation means or separation unit for separating the adsorbent that has adsorbed precious metal ions from the solution.

[0085] The precious metal particle recovery device can be used to easily and efficiently recover precious metal particles (particularly gold particles) dissolved in a solution, and therefore is particularly preferably a gold particle recovery device.

[0086] The above-described configurations and combinations thereof of the present disclosure are merely examples, and additions, omissions, substitutions, and modifications of the configurations can be made as appropriate without departing from the spirit of the present disclosure.

[0087] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to these examples and is limited only by the claims.

[0088] Example 1 At room temperature, 40.6 mg of powdered cellulose acetate (total degree of acetyl group substitution: 2.4, Mw: 190,000, Mw / Mn: 2.2) serving as an adsorbent was added to 20 mL of an acidic hydrochloric acid solution (hydrochloric acid concentration: 0.1 M, pH: 1) containing 100 ppm of gold ions (equivalent to Au element), and the mixture was stirred for 3 hours.

[0089] The cellulose acetate was then filtered off, and 20 mL of water and 8.4 mg of trisodium citrate (anhydrous, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a reducing agent were added, followed by refluxing at 100°C for 10 minutes in a refluxing apparatus (personal organic synthesis apparatus ChemStation, model number PPS-2511, manufactured by Tokyo Rikakikai).

[0090] The supernatant of the resulting solution was then removed with a dropper, allowed to air dry, and subjected to SEM measurement and EDS mapping measurement. The results are shown in Figures 1 to 3. Figures 1 to 3 confirm that gold particles with particle diameters of 100 nm to 500 nm were produced.

[0091] <SEM and EDS measurement conditions> SEM device name: SU-5000 (manufactured by Hitachi High-Tech Corporation) EDS detector: X-Max50 (manufactured by Oxford Instruments) Acceleration voltage: 15 kV Spot intensity: 50 Pretreatment: Pt vapor deposition

[0092] Comparative Example 1 The same procedure as in Example 1 was carried out, except that 40 mg of activated carbon (manufactured by Osaka Gas Chemicals Co., Ltd.) was used as the adsorbent. As in Example 1, the supernatant was removed with a dropper, and the resulting solution was air-dried and subjected to SEM measurement and EDS mapping measurement. However, the generation of gold particles could not be confirmed.

[0093] In summary, the configuration of the present disclosure and its variations are described below. [1] A precious metal particle recovery kit including the following adsorbent and the following reducing agent. Adsorbent: When contacted with a solution in which a precious metal is dissolved, it has the function of adsorbing the precious metal ions in the solution. Reducing agent: When contacted with the precious metal ions adsorbed to the adsorbent, it has the function of reducing the precious metal ions, desorbing them from the adsorbent, and forming them into particles. [2] The precious metal particle recovery kit according to [1], wherein the adsorbent is an ester having a sugar skeleton. [3] The precious metal particle recovery kit according to [1], wherein the adsorbent is a sugar ester having a total degree of ester group substitution of 1.0 to 3.0 (preferably 2.0 to 3.0, particularly preferably 2.2 to 2.7). [4] The precious metal particle recovery kit according to [2] or [3], wherein the sugar ester has a weight-average molecular weight of 100,000 to 1,000,000 (preferably 100,000 to 500,000, and particularly preferably 100,000 to 300,000). [5] The precious metal particle recovery kit according to [1], wherein the adsorbent is a polysaccharide acylate. [6] The precious metal particle recovery kit according to [1], wherein the adsorbent is a polysaccharide acylate having a total acyl group substitution degree of 1.0 to 3.0 (preferably 2.0 to 3.0, and particularly preferably 2.2 to 2.7). [7] The precious metal particle recovery kit according to [5] or [6], wherein the polysaccharide acylate has a weight-average molecular weight of 100,000 to 1,000,000 (preferably 100,000 to 500,000, and particularly preferably 100,000 to 300,000). [8] The precious metal particle recovery kit according to [1], wherein the adsorbent is cellulose acylate having a repeating unit represented by formula (1). [9] The precious metal particle recovery kit according to [1], wherein the adsorbent is at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

[10] The precious metal particle recovery kit according to [1], wherein the adsorbent is amylose acylate having a repeating unit represented by formula (2).

[11] The precious metal particle recovery kit according to [1], wherein the adsorbent is at least one selected from amylose acetate, amylose propionate, and amylose butyrate.

[12] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a compound having at least one group selected from a hydroxyl group, a thiol group, a carboxyl group, and a group containing a nitrogen atom.

[13] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a compound having two or more (preferably three or more) groups selected from a hydroxyl group, a thiol group, a carboxyl group, and a group containing a nitrogen atom in one molecule.

[14] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a compound having a hydroxyl group and / or a carboxyl group.

[15] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a compound having a hydroxyl group and / or a carboxyl group, and wherein the total number of hydroxyl groups and carboxyl groups in one molecule is two or more (preferably three or more).

[16] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a hydroxycarboxylic acid.

[17] The precious metal particle recovery kit according to any one of [1] to

[11] , wherein the reducing agent is a hydroxypolycarboxylic acid.

[18] The precious metal particle recovery kit according to any one of [1] to

[17] , wherein the adsorbent is a separation membrane or a column packing material.

[19] A precious metal particle recovery method comprising the following steps: Step 1: bringing an adsorbent into contact with a solution in which a precious metal has been dissolved, thereby adsorbing the precious metal ions in the solution onto the adsorbent; Step 2: bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, thereby reducing the precious metal ions and desorbing them from the adsorbent to form particles.

[20] The precious metal particle recovery method according to

[19] , wherein the amount of the reducing agent used in Step 2 is 0.1 to 0.5 parts by weight (preferably 0.1 to 0.3 parts by weight) per part by weight of the adsorbent.

[21] The method for recovering precious metal particles according to

[19] , wherein step 2 is the following step 2': Step 2': bringing a reducing agent into contact with the precious metal ions adsorbed on the adsorbent, reducing the precious metal ions and causing them to be desorbed from the adsorbent, thereby generating precious metal particles having a particle diameter of 50 nm or more.

[22] The method for recovering precious metal particles according to

[19] , wherein step 2 is the following step 2":Step 2": mixing the adsorbent with 0.1 to 0.5 parts by weight (preferably 0.1 to 0.3 parts by weight) of a reducing agent relative to 1 part by weight of the adsorbent, bringing the reducing agent into contact with the precious metal ions adsorbed on the adsorbent, reducing the precious metal ions and causing them to be desorbed from the adsorbent, thereby generating precious metal particles having a particle diameter of 50 nm or more.

[23] A precious metal particle recovery device comprising the following adsorption means and reduction means. Adsorption means: means for bringing an adsorbent into contact with a solution in which a precious metal is dissolved, thereby causing the precious metal ions in the solution to be adsorbed onto the adsorbent. Reduction means: means for bringing the precious metal ions adsorbed on the adsorbent into contact with a reducing agent, thereby reducing the precious metal ions and causing them to be desorbed from the adsorbent, thereby forming particles.

[0094] By using the precious metal particle recovery kit of the present disclosure, precious metals dissolved in a solution can be granulated and recovered with fewer processes than conventional methods. Furthermore, by using the kit of the present disclosure, precious metal ions adsorbed on an adsorbent can be directly converted into precious metal particles. Rather than reducing the precious metal ions present in a solution to form particles, the precious metal ions are densely packed by being adsorbed on an adsorbent, and they aggregate and granulate, resulting in particles with a large particle size. Furthermore, the precious metal particle recovery kit of the present disclosure can be reused. Therefore, the precious metal particle recovery kit has the effect of reducing the burden on the environment while promoting the reuse of valuable resources.

Claims

1. A noble metal particle recovery kit comprising the following adsorbent and the following reducing agent. Adsorbent: A polysaccharide ester which is a condensation product of at least one polysaccharide selected from cellulose, amylose, and dextran and an oxo acid Reducing agent: When contacted with noble metal ions adsorbed on the adsorbent, it has the function of reducing the noble metal ions, desorbing them from the adsorbent, and forming particles.

2. The noble metal particle recovery kit according to claim 1, wherein the reducing agent is a compound having three or more groups selected from a hydroxyl group, a thiol group, a carboxyl group, and a group containing a nitrogen atom in one molecule.

3. The noble metal particle recovery kit according to claim 1 or 2, wherein the polysaccharide ester is in a powder form, a spherical form, a pellet form, or a fibrous form.

4. The noble metal particle recovery kit according to claim 1 or 2, wherein the adsorbent is a polysaccharide acrylate which is a condensation product of at least one polysaccharide selected from cellulose, amylose, and dextran and a carboxylic acid.

5. The noble metal particle recovery kit according to claim 1 or 2, wherein the adsorbent is a separation membrane containing the polysaccharide ester or a column packing material containing the polysaccharide ester.

6. The noble metal particle recovery kit according to claim 1 or 2, which is used to obtain a colloid in which noble metal particles are dispersed in a solution from a solution in which a noble metal is dissolved.

7. A noble metal particle recovery method comprising the following steps. Step 1: Contacting the following adsorbent with a solution in which a noble metal is dissolved to adsorb noble metal ions in the solution onto the adsorbent Step 2: Contacting a reducing agent with the noble metal ions adsorbed on the adsorbent to reduce the noble metal ions, desorb them from the adsorbent, and form particles. Adsorbent: A polysaccharide ester which is a condensation product of at least one polysaccharide selected from cellulose, amylose, and dextran and an oxo acid

8. The method for recovering noble metal particles according to claim 7, wherein the polysaccharide ester is in a powdery, spherical, pellet-shaped, or fibrous form.

9. The method for recovering noble metal particles according to claim 7 or 8, wherein the pH of the solution in which the noble metal is dissolved in Step 1 is set to be more than 0 and 3 or less.

10. The method for recovering noble metal particles according to claim 7 or 8, wherein Step 2 is a step of bringing a reducing agent into contact with the noble metal ions adsorbed on the adsorbent to reduce the noble metal ions, desorb them from the adsorbent, and granulate them to obtain a colloid in which noble metal particles are dispersed in a solution.

11. A noble metal particle recovery device comprising the following adsorption means and reduction means. Adsorption means: means for bringing the following adsorbent into contact with a solution in which a noble metal is dissolved to adsorb noble metal ions in the solution onto the adsorbent Reduction means: means for bringing a reducing agent into contact with the noble metal ions adsorbed on the adsorbent to reduce the noble metal ions, desorb them from the adsorbent, and granulate them Adsorbent: A polysaccharide ester which is a condensation reaction product of at least one polysaccharide selected from cellulose, amylose, and dextran and an oxo acid

12. The noble metal particle recovery device according to claim 11, wherein the polysaccharide ester is in a powdery, spherical, pellet-shaped, or fibrous form.