Metal adsorbent and method for selectively separating and recovering metal

Abstract

To provide a gold adsorbent capable of easily, efficiently and selectively recovering gold from a gold-containing liquid.SOLUTION: The gold adsorbent contains a polymer containing a structural unit represented by formula (1). (In the formula (1), X represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. However, a part or all of hydrogen atoms of the alkyl group, the phenyl group and the benzyl group may be substituted with any one of a halogen atom, a carboxy group, a hydroxy group, an amino group and a nitro group. ) SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a gold adsorbent, a gold adsorption method, and a method for selectively separating and recovering gold. [Background technology]

[0002] In recent years, with the remarkable development of industrial technology in fields such as electronics and electricity, and organic synthesis, metals such as gold, silver, palladium, platinum, and rhodium are widely used not only in decorative items, but also in electronic industrial materials such as semiconductors, circuit boards, and cathode ray tubes, as well as catalysts for organic chemical reactions. However, it is well known that the production of these metals is smaller than that of other metals, and efficient recovery and reuse of these metals has become a major challenge.

[0003] Several methods are known for recovering gold from wastewater containing gold. These methods include thermal concentration, activated carbon, solvent extraction (see, for example, Patent Document 1), and electrolysis. However, while these methods are applicable when the gold concentration in the wastewater is high, they have the problem that when the gold concentration in the wastewater is low, a large amount of gold remains in the solution without being recovered, resulting in a low recovery rate. Furthermore, it has been difficult to selectively recover gold from wastewater containing multiple metals.

[0004] The method of concentrating and recovering gold using ion exchange resins is known to have a relatively high recovery rate, but when recovering gold from resins that have adsorbed gold, it is not possible to desorb the gold from the resin, and the expensive resin must be incinerated before the gold can be recovered. Even if desorption is possible, the desorption rate is low, which reduces the gold recovery rate and makes it impossible to reuse the resin.

[0005] Furthermore, the gold-containing solution intended for recovery often contains large amounts of other metals, such as palladium, platinum, iron, nickel, copper, lead, zinc, tin, and cobalt, in addition to gold. These metals can contaminate the gold during recovery, preventing the gold from being of high quality and requiring many steps in the subsequent refining of the gold.

[0006] As an adsorbent for easily, efficiently and selectively recovering gold from a gold-containing liquid, a gold adsorbent containing, as an active ingredient, a polyaniline-based resin having a specific structure with a number-average molecular weight in the range of 500 to 1,000,000 has been proposed (see Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-113070 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-49315 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a gold adsorbent that can easily and efficiently recover gold selectively from a gold-containing liquid, as well as a method for adsorbing gold and a method for selectively separating and recovering gold using the same. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that the above problems can be solved, and have completed the present invention having the following gist.

[0010] That is, the present invention includes the following. [1] A gold adsorbent containing a polymer containing a structural unit represented by the following formula (1): [ka] (In formula (1), X represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. However, in the alkyl group, the phenyl group, and the benzyl group, some or all of the hydrogen atoms may be substituted with any of a halogen atom, a carboxy group, a hydroxy group, an amino group, and a nitro group.) [2] A method for adsorbing gold, comprising contacting a liquid containing gold with the gold adsorbent described in [1]. [3] contacting a liquid containing gold with the gold adsorbent according to [1] to allow the gold to be adsorbed by the gold adsorbent; and desorbing the gold from the gold adsorbent using a desorbent. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a gold adsorbent that can easily and efficiently recover gold selectively from a gold-containing liquid, as well as a gold adsorption method and a method for selectively separating and recovering gold using the same. [Brief explanation of the drawings]

[0012] [Figure 1A] FIG. 1A is a graph showing the measurement results of Au(III) in Example 1. [Figure 1B] FIG. 1B is a graph showing the measurement results of Pd(II) in Example 1. [Figure 1C] FIG. 1C is a graph showing the measurement results of Pt(II) in Example 1. [Figure 1D] FIG. 1D is a graph showing the measurement results of Pt(IV) in Example 1. [Figure 2] FIG. 2 is a graph showing the measurement results in Example 2. [Figure 3A] FIG. 3A is a graph showing the measurement results of Au(III) in Example 3. [Figure 3B] FIG. 3B is a graph showing the measurement results of 21 elements in Example 3. [Figure 4] FIG. 4 is a graph showing the measurement results in Example 4. [Figure 5A] FIG. 5A is a graph showing the measurement results of Au(III) in Example 5 (part 1). [Figure 5B] FIG. 5B is a graph showing the measurement results of Au(III) in Example 5 (part 2). [Figure 6A] FIG. 6A is a graph showing the measurement results of Pd(II) in Example 5 (part 1). [Figure 6B] FIG. 6B is a graph showing the measurement results of Pd(II) in Example 5 (part 2). [Figure 7A] FIG. 7A is a graph showing the measurement results of Pt(II) in Example 5 (part 1). [Figure 7B] FIG. 7B is a graph showing the measurement results of Pt(II) in Example 5 (part 2). [Figure 8A] FIG. 8A is a graph showing the measurement results of Pt(IV) in Example 5 (part 1). [Figure 8B] FIG. 8B is a graph showing the measurement results of Pt(IV) in Example 5 (part 2). DETAILED DESCRIPTION OF THE INVENTION

[0013] (gold adsorbent) The gold adsorbent of the present invention (hereinafter sometimes simply referred to as "adsorbent") contains a polymer containing a structural unit represented by the following formula (1). The adsorbent may be a polymer (hereinafter sometimes simply referred to as "polymer") containing a structural unit represented by formula (1) itself. [ka] (In formula (1), X represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. However, in the alkyl group, the phenyl group, and the benzyl group, some or all of the hydrogen atoms may be substituted with any of a halogen atom, a carboxy group, a hydroxy group, an amino group, and a nitro group.)

[0014] In the course of searching for an adsorbent capable of selectively adsorbing gold, the present inventors focused on the structure represented by formula (1) and conducted extensive research. As a result, they found that an adsorbent containing a polymer containing a structural unit represented by formula (1) selectively adsorbs gold, leading to the present invention. Although it is not clear why the structure represented by formula (1) contributes to the selective adsorption of gold, it is believed that the three-dimensional structure of the ring in the structure represented by formula (1) and the polarity of the ring contribute to this.

[0015] The alkyl group having 1 to 6 carbon atoms may be linear, branched, or cyclic. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, a t-butyl group, an n-pentyl group, a cyclopentyl group, an n-hexyl group, and a cyclohexyl group.

[0016] Examples of the structural unit represented by formula (1) include the following structural units. [ka]

[0017] The polymer containing the structural unit represented by formula (1) may or may not contain other structural units. Examples of other structural units include a structural unit represented by the following formula (2) and a structural unit represented by the following formula (3). The structural unit represented by formula (2) is introduced into a polymer, for example, for the purpose of adjusting the hydrophilicity and hydrophobicity of the polymer. The structural unit represented by formula (3) is introduced into a polymer, for example, for the purpose of adjusting the solubility of the polymer. [ka] (In formula (2), R 1 represents a hydrogen atom or a methyl group. X 1represents a single bond, an ester group, or an amide group. R 11 represents a hydrogen atom or a monovalent organic group. In formula (3), R 2 each independently represents a hydrogen atom or a methyl group. X 2 each independently represents an ester group or an amide group. R 12 represents a divalent organic group.

[0018] The monovalent organic group may have 1 to 10 carbon atoms, for example. The monovalent organic group may be, for example, a hydrocarbon group or an organic group having a hetero atom. In order to impart hydrophilicity to the polymer, the monovalent organic group preferably has a hydroxy group, and the monovalent organic group is more preferably a hydroxyalkyl group having 1 to 6 carbon atoms.

[0019] X 1 When is a single bond, R 11 is, for example, a monovalent organic group. In this case, the monovalent organic group may be an aromatic hydrocarbon group which may have a substituent. Examples of the aromatic hydrocarbon group include a monovalent group obtained by removing a hydrogen atom from a benzene ring or a naphthalene ring. Examples of the substituent include a hydroxy group, an alkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms. There is no particular limitation on the number of substituents.

[0020] The divalent organic group may have 2 to 10 carbon atoms, for example. The divalent organic group may be, for example, a hydrocarbon group or an organic group having a hetero atom. The divalent organic group may be, for example, an alkylene group having 2 to 6 carbon atoms.

[0021] The structural unit represented by formula (2) is preferably a structural unit represented by the following formula (2-1). The structural unit represented by formula (3) is preferably a structural unit represented by the following formula (3-1). [ka] (In formula (2-1), R 1 , and R 11 are R in Equation (2), respectively. 1 , and R 11 is synonymous with. In formula (3-1), R 2 , and R 12 are R in Equation (3), respectively. 2 , and R 12 is synonymous with.

[0022] Examples of the structural unit represented by formula (2) include the following structural units. [ka]

[0023] Examples of the structural unit represented by formula (3) include the following structural units. [ka]

[0024] The molar ratio of the structural unit represented by formula (1) in all structural units of the polymer is not particularly limited, but is preferably 30 mol % to 100 mol %, more preferably 35 mol % to 100 mol %, and particularly preferably 40 mol % to 100 mol %.

[0025] When the polymer has a structural unit represented by formula (2), the molar ratio of the structural unit represented by formula (2) to all structural units of the polymer is not particularly limited, but is preferably 5 mol % to 60 mol %, more preferably 10 mol % to 55 mol %, and particularly preferably 20 mol % to 50 mol %.

[0026] When the polymer has a structural unit represented by formula (3), the molar ratio of the structural unit represented by formula (3) to all structural units of the polymer is not particularly limited, but is preferably 0.5 mol % to 20 mol %, more preferably 1 mol % to 15 mol %, and particularly preferably 2 mol % to 10 mol %.

[0027] When the polymer is a copolymer, the polymer may be a random copolymer or a block copolymer.

[0028] The molecular weight of the polymer is not particularly limited, but the weight average molecular weight determined by gel permeation chromatography (hereinafter sometimes abbreviated as GPC) is preferably 1,500 to 100,000, and more preferably 2,000 to 50,000.

[0029] <Polymer manufacturing method> As a polymerization method for producing the polymer, known polymerization methods such as radical polymerization, anionic polymerization, cationic polymerization, etc., as well as various known techniques such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization, can be used.

[0030] A polymer containing a structural unit represented by formula (1) can be synthesized by radical polymerization of a carbon-carbon double bond, and therefore can be produced more cheaply and simply than the polyaniline-based resin described in Patent Document 2.

[0031] The polymer can be obtained, for example, by polymerizing a monomer containing a compound represented by the following formula (1A). When the polymer has a structural unit represented by formula (2) and a structural unit represented by formula (3), the polymer can be obtained, for example, by polymerizing monomers including a compound represented by the following formula (1A), a compound represented by the following formula (2A), and a compound represented by the following formula (3A). [ka] (In formula (1A), X has the same meaning as X in formula (1). In formula (2A), R1 , R 11 , and X 1 are R in Equation (2), respectively. 1 , R 11 , and X 1 is synonymous with. In formula (3A), R 2 , R 12 , and X 2 are R in Equation (3), respectively. 2 , R 12 , and X 2 is synonymous with.

[0032] The polymerization initiator used in the polymerization is not particularly limited, but examples thereof include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2 ,2'-Azobis(isobutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl)azo]formamide, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], and 2,2'-azobis(2-methylpropionamidine) dihydrochloride, etc. are used.

[0033] The solvent used during polymerization is not particularly limited, and examples thereof include dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, and butyl lactate. These may be used alone or in combination.

[0034] The reaction temperature is not particularly limited, but may be, for example, 20°C to 150°C. The reaction time is not particularly limited, but may be, for example, 1 hour to 72 hours.

[0035] The adsorbent may be a polymer itself or a support in which a polymer is supported on particles.

[0036] (Gold adsorption method) The method for adsorbing gold of the present invention comprises contacting a gold-containing liquid with the gold adsorbent of the present invention.

[0037] The gold-containing liquid is not particularly limited as long as it contains gold. The liquid containing gold may be any solution such as an aqueous solution or an organic solution. Examples of liquids containing gold include gold extracted from gold-containing scrap, waste liquid containing gold discharged from processes that utilize gold, and waste liquid containing trace amounts of gold discharged from processes that recover or refine gold.

[0038] In order to efficiently adsorb gold onto the adsorbent, it is preferable to acidify the gold-containing liquid. Methods for acidifying a liquid containing gold include adding a mineral acid such as hydrochloric acid, nitric acid, or sulfuric acid to the liquid containing gold. The hydrogen ion concentration of the gold-containing liquid is preferably pH=1 to 5.5, and more preferably pH=1 to 4.0.

[0039] The method for bringing the adsorbent into contact with the gold-containing liquid is not particularly limited, and examples thereof include a method in which the adsorbent is added to the gold-containing liquid.

[0040] When the adsorbent is brought into contact with the gold-containing liquid, the amount of the adsorbent relative to the gold-containing liquid is not particularly limited.

[0041] The contact temperature between the gold-containing liquid and the adsorbent is, for example, 0 to 100°C, preferably 10 to 60°C. If the temperature is lower than 0°C, the viscosity of the liquid may increase and solids may precipitate. Also, if the temperature is higher than 100°C, the cost of heating increases, which is undesirable. When the adsorbent is added to a liquid containing gold, the contact temperature is, for example, the liquid temperature of the liquid containing gold. The contact time between the gold-containing liquid and the adsorbent is not particularly limited, but is usually several seconds or more, preferably 1 minute to 48 hours.

[0042] (Selective separation and recovery method for gold) The method for selectively separating and recovering gold of the present invention includes a gold adsorption step and a gold desorption step. The method for selectively separating and recovering gold may also include other steps.

[0043] <Gold adsorption process> The gold adsorption step is a step in which the gold adsorbent of the present invention is brought into contact with a liquid containing gold, and gold is adsorbed onto the gold adsorbent. The gold adsorption step can be carried out, for example, by the gold adsorption method of the present invention.

[0044] <Gold desorption process> The gold desorbing step is a step of desorbing gold from the gold adsorbent using a desorbent.

[0045] The desorbing agent is not particularly limited, and for example, a conventionally known desorbing agent (desorbing agent) can be used. The releasing agent may be, for example, an acidic solution containing a thiourea derivative. Examples of thiourea derivatives include thiourea, N-methylthiourea, N,N'-dimethylthiourea, N-ethylthiourea, and N,N'-diethylthiourea. The acidic solution may be, for example, an acidic aqueous solution.

[0046] Examples of the gold desorption step include a method of immersing the adsorbent on which gold has been adsorbed in a liquid desorbent, and a method of passing a liquid desorbent through a column packed with the adsorbent on which gold has been adsorbed. The liquid temperature of the liquid desorbing agent is, for example, 0 to 100°C, preferably 10 to 60°C. If the temperature is lower than 0°C, the desorption ability of gold may decrease. On the other hand, if the temperature is higher than 100°C, the cost required for heating increases, which is not preferable. The contact time between the adsorbent that has adsorbed gold and the desorbent is not particularly limited, but is usually several seconds or more, preferably 1 minute to 48 hours.

[0047] When the releasing agent is an acidic solution containing a thiourea derivative, the concentration of the thiourea derivative is preferably 0.001 mol / L to 10 mol / L.The pH of the acidic solution is preferably 4 or less.

[0048] The gold recovered by the above method can be recovered as high-quality gold metal or gold compounds by known methods such as concentration, refining, electrolysis, etc., and used for industrial and decorative purposes.

[0049] After gold is desorbed from the adsorbent, it can be reused after undergoing steps such as washing with water and regeneration. [Example]

[0050] The present invention will be described in more detail below, but the present invention is not limited to the following examples.

[0051] The weight-average molecular weights of the polymers shown in Synthesis Examples 1 to 3 below in this specification are the results of measurement by gel permeation chromatography (hereinafter abbreviated as GPC). For the measurement, a GPC device manufactured by Tosoh Corporation was used, and the measurement conditions etc. are as follows. GPC column: TSKgel Super-MultiporeHZ-N (2 columns) Column temperature: 40℃ Solvent: tetrahydrofuran (THF) Flow rate: 0.35ml / min Standard sample: Polystyrene (manufactured by Tosoh Corporation)

[0052] (Synthesis Example 1) <Polymerization of maleimide> 30.0 g (309 mmol) of maleimide and 1.8 g of 2,2'-azobis(isobutyronitrile) were dissolved in 127.2 g of propylene glycol monomethyl ether and polymerized under heating at 80°C in nitrogen for 48 hours to obtain a polymer solution. The polymer (Compound 1) was then reprecipitated in pure water, and the molecular weight of the resulting polymer (Compound 1) was measured by GPC (standard polystyrene equivalent) to find a weight average molecular weight (Mw) of 4,400. This reaction product has a repeating unit represented by the following formula:

[0053] [ka]

[0054] (Synthesis Example 2) <Copolymerization of Maleimide / 2-Hydroxyethyl Methacrylate / Ethylene Glycol Dimethacrylate-1> 15.0 g (155 mmol) of maleimide, 14.3 g (112.4 mmol) of 2-hydroxyethyl methacrylate, 2.8 g (14.1 mmol) of ethylene glycol dimethacrylate, and 0.5 g of 2,2'-azobis(isobutyronitrile) were dissolved in 97.6 g of propylene glycol monomethyl ether and polymerized at 75°C under nitrogen for 48 hours to obtain a polymer solution. The polymer (Compound 2), which was then reprecipitated in pure water, was measured for molecular weight by GPC (standard polystyrene equivalent) and found to have a weight-average molecular weight (Mw) of 33,000. The copolymer composition was calculated by NMR and found to have a molar ratio of maleimide / 2-hydroxyethyl methacrylate / ethylene glycol dimethacrylate = 49 / 45 / 6. This reaction product has the repeating unit represented by the following formula:

[0055] [ka]

[0056] (Synthesis Example 3) <Copolymerization of Maleimide / 2-Hydroxyethyl Methacrylate / Ethylene Glycol Dimethacrylate-2> 25.0 g (258 mmol) of maleimide, 12.0 g (92.0 mmol) of 2-hydroxyethyl methacrylate, 3.7 g (18.4 mmol) of ethylene glycol dimethacrylate, and 0.6 g of 2,2'-azobis(isobutyronitrile) were dissolved in 123.7 g of propylene glycol monomethyl ether and polymerized at 75°C under nitrogen for 48 hours to obtain a polymer solution. The polymer (compound 3) was then reprecipitated in pure water. The molecular weight of the resulting polymer (compound 3) was measured by GPC (standard polystyrene equivalent) and found to have a weight-average molecular weight (Mw) of 413,000. The copolymer composition was calculated by NMR and found to have a molar ratio of maleimide / 2-hydroxyethyl methacrylate / ethylene glycol dimethacrylate = 64 / 30 / 6. This reaction product has the repeating unit represented by the following formula:

[0057] [ka]

[0058] Example 1 Aqueous solutions of gold(III), palladium(II), platinum(II), and platinum(IV) (each element concentration 5 mg / L) were prepared using 0.01 mol / L, 0.1 mol / L, or 0.2 mol / L hydrochloric acid. Sodium chloride was added to each solution to adjust the chloride ion concentration to 0.2 mol / L. 50 mg of Compound 1 (polymaleimide) obtained in Synthesis Example 1 was added to 20 mL of each solution and the mixture was shaken at 200 rpm. Appropriate aliquots of the solution were centrifuged and diluted, and the concentrations of each element in the solution were measured by microwave plasma atomic emission spectroscopy or ICP atomic emission spectroscopy. The ratio of the initial emission intensity (C) of each element after a certain time period to the initial emission intensity (C) was calculated (emission intensity ratio (C / C)). The results are shown in Figures 1A–1D. As shown in Figure 1A, the gold(III) concentration decreased over time in all aqueous solutions with different acid concentrations. Palladium(II) concentration decreased more significantly with decreasing acid concentration within the range examined (Fig. 1B). Platinum(II, IV) was hardly adsorbed to compound 1 (Fig. 1C and 1D).

[0059] Example 2 Aqueous solutions of gold(III), palladium(II), platinum(II), and platinum(IV) (each element concentration 1 mg / L) were prepared. To 20 mL of each of these solutions, 10 mg of Compound 1 (polymaleimide) obtained in Synthesis Example 1 was added and the mixture was shaken at 120 rpm for 48 hours. Appropriate aliquots of the aqueous solution were collected, centrifuged, and diluted, and the concentration of each element in the aqueous solution was measured. The results are shown in Figure 2. The vertical axis represents the amount of adsorption per 1 g of compound (mg / g). Therefore, a larger value indicates a larger amount of adsorption. Gold(III) was adsorbed over a wide pH range. Palladium(II) was adsorbed over a pH range of 2 to 4.5, but the amount adsorbed was smaller than that of gold(III). Platinum(II, IV) was hardly adsorbed at any pH.

[0060] Example 3 A mixed standard solution (ICP Multielement Standard XVI, Merck) of 21 elements (arsenic, beryllium, calcium, cadmium, cobalt, chromium, copper, iron, lithium, magnesium, manganese, molybdenum, nickel, lead, antimony, selenium, strontium, titanium, thallium, vanadium, and zinc) was added to a 5 mmol / L aqueous solution of ammonium acetate to a concentration of 1 mg / L of each element. Similarly, a 5 mmol / L aqueous solution of ammonium acetate containing 1 mg / L of gold(III) was also prepared. The pH values ​​of these solutions were 2.4 and 2.9, respectively. 50 mg of Compound 1 (polymaleimide) obtained in Synthesis Example 1 was added to 5 mL of each solution and shaken at 200 rpm for 6 hours. Portions of these solutions were taken, centrifuged, and diluted. Each element in the solution was measured by ICP atomic emission spectroscopy. The ratio of the luminescence intensity (C) of each element after 6 hours to the initial luminescence intensity (C) was determined (the luminescence intensity ratio (C / C)). The emission intensity ratio for gold is shown in Figure 3A. The emission intensity ratio for gold(III) was approximately 0.2, indicating that gold(III) was adsorbed to compound 1. On the other hand, the emission intensity ratio for 21 elements is shown in Figure 3B. The emission intensity ratio for the 21 elements was nearly 1, except for calcium and copper, which were not adsorbed to compound 1 under these conditions. Note that the emission intensity ratios for calcium and copper exceeded 1, but this is not shown in the figure as it is suspected to be due to contamination during the experiment.

[0061] Example 4 Aqueous solutions of gold(III), palladium(II), platinum(II), platinum(IV), copper(II), iron(III), zinc(II), nickel(II), and cobalt(II) (each element concentration 1 mg / L) containing 0.1 mol / L hydrochloric acid were prepared. Aqueous solutions of gold (III), palladium (II), platinum (II), and platinum (IV) (each element concentration 1 mg / L) containing 1 mol / L hydrochloric acid were prepared. To each of 20 mL of these aqueous solutions, 10 mg of Compound 1 (polymaleimide) obtained in Synthesis Example 1 was added, and the mixture was shaken at 120 rpm for 48 hours. An appropriate aliquot of the aqueous solution was taken, centrifuged, and diluted, and the concentration of each element in the aqueous solution was measured. This experiment was repeated three times. The ratio of the concentration (C) after 48 hours to the initial concentration (C) of each element (concentration (C / C): %) was calculated. The results are shown in Figure 4. The error bars in the figure represent the standard deviation of the measured values. Gold (III) was adsorbed, and the adsorption rate was greater under the 0.1 mol / L hydrochloric acid condition than under the 1 mol / L hydrochloric acid condition. The other elements were hardly adsorbed under these conditions.

[0062] Example 5 Compound 2 (10 mg) obtained in Synthesis Example 2 or compound 3 (10 mg) obtained in Synthesis Example 3 was added to 20 mL of an aqueous solution (containing 0.01 mol / L hydrochloric acid) containing 1 mmol / L of any of gold (III), palladium (II), platinum (II), and platinum (IV), and the mixture was shaken at 120 rpm. An appropriate amount of the aqueous solution was taken, centrifuged, and diluted, and the concentration of each element in the aqueous solution was measured. The results obtained are shown in FIGS. 5A to 5B, 6A to 6B, 7A to 7B, and 8A to 8B. For comparison, the results for Compound 1 (polymaleimide, weight-average molecular weight 4,400; denoted as "Compound 1 (low molecular weight)" in each graph) obtained in Synthesis Example 1 and a polymaleimide (weight-average molecular weight approximately 9,500; denoted as "Compound 1 (high molecular weight)" in each graph) synthesized in the same manner as in Synthesis Example 1 are also shown. In these figures, the vertical axis represents the adsorption amount (mmol / mmol) per nitrogen atom (nitrogen atom contained in the maleimide skeleton) in the compound. Compound 2 obtained in Synthesis Example 2 and Compound 3 obtained in Synthesis Example 3, which contain 2-hydroxymethacrylate and ethylene glycol dimethacrylate, adsorbed elements more rapidly than Compound 1 (Figures 5A and 5B). Furthermore, platinum (II, IV), which was hardly adsorbed by Compound 1, was slightly adsorbed by Compounds 2 and 3 (Figures 7B and 8B).

[0063] From the above, it was found that the polymer having the structural unit represented by formula (1) can selectively adsorb gold (III) and, depending on the conditions, can also adsorb palladium (II), but hardly adsorbs platinum (II, IV). This compound may be useful for the selective recovery of gold (III) contained in wastewater, etc.

Claims

1. A gold adsorbent containing a polymer containing a structural unit represented by the following formula (1): 【Chemistry 1】 (In formula (1), X represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. However, in the alkyl group, the phenyl group, and the benzyl group, some or all of the hydrogen atoms may be substituted with any of a halogen atom, a carboxy group, a hydroxy group, an amino group, and a nitro group.)

2. A method for adsorbing gold, comprising contacting a gold-containing liquid with the gold adsorbent of claim 1.

3. a step of contacting a gold-containing liquid with the gold adsorbent according to claim 1 to adsorb the gold onto the gold adsorbent; and desorbing the gold from the gold adsorbent using a desorbent.

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