Metal dissolving solution and method for recovering gold

Abstract

To provide a reusable metal dissolving solution and a method for recovering gold using the metal dissolving solution.SOLUTION: A metal dissolving solution contains a hydrophilic organic solvent, a chlorine compound, and an oxidizing agent. The chlorine compound has the property of generating chlorine ions (Cl-) by dissolving in the hydrophilic organic solvent. A method for recovering gold comprises: (1) obtaining a composition containing a metal dissolving solution and dissolved gold by dissolving gold in the metal dissolving solution; (2) obtaining a gold-containing adsorbent by bringing the composition into contact with an adsorbent and adsorbing the dissolved gold onto the adsorbent; and (3) recovering gold in the gold-containing adsorbent by separating the gold-containing adsorbent and the composition. The method for recovering gold may further comprise: (4) reusing the metal dissolving solution in the composition by further dissolving gold in the composition after separating the gold-containing adsorbent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a metal dissolving solution and a method for recovering gold using the metal dissolving solution. [Background technology]

[0002] In recent years, many electrical and electronic devices, such as mobile phones, are being used and discarded. These devices contain various metals, including precious and rare metals. Therefore, discarded electrical and electronic devices have been attracting attention as "urban mines" for extracting precious metals. Gold (Au), in particular, is a material used in bonding wires that connect IC chip electrodes to lead frames, and is used in large quantities. Therefore, there is a need for technology to efficiently recover gold from urban mines.

[0003] To recover precious metals from used equipment, such as urban mines, it is first necessary to use a metal dissolving solution to dissolve the precious metals in the used equipment. Recently, "organic aqua regia," which contains an organic solvent and copper halide, has become known as a solvent (metal dissolving solution) for dissolving gold. In organic aqua regia, the copper halide, an oxidizing agent, contributes to the dissolution of gold. A method has been proposed in which the gold contained in used electrical and electronic equipment is dissolved in this organic aqua regia, and then the gold in the solution is recovered. Furthermore, an "etching solution" composed of an organic solvent and an elemental halogen is known for etching semiconductors containing precious metals. In this etching solution, the oxidizing agent iodine contributes to the dissolution of gold.

[0004] For example, Japanese Patent No. 6196662 (Patent Document 1) proposes a gold recovery method including a step of dissolving gold in a solvent system containing copper halide and an aprotic polar solvent, and a step of adding a reducing agent to the solvent system in which the gold has been dissolved to precipitate the precious metal. Japanese Patent Laid-Open Publication No. 2-310326 (Patent Document 2) discloses a technique in which a porous granular resin is impregnated with dibutyl carbitol or methyl isobutyl ketone as an organic solvent, and then a hydrochloric acid solution containing gold is passed through the porous granular resin layer to selectively extract the gold into the dibutyl carbitol or methyl isobutyl ketone. Japanese Patent Laid-Open Publication No. 2002-194450 (Patent Document 3) proposes a method for selectively adsorbing platinum group precious metals from an organic solvent solution using an adsorbent containing nicotinamide as the active ingredient. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6196662 [Patent Document 2] Japanese Patent Application Publication No. 2-310326 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-194450 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 does not disclose the use of adsorbents in the recovery of dissolved gold. Furthermore, Patent Document 1 adds a reducing agent, such as water or ascorbic acid, to precipitate gold dissolved in organic aqua regia. The addition of a reducing agent completely removes the oxidizing agent that contributes to the dissolution of gold. Therefore, reusing the organic aqua regia after gold recovery as a gold dissolving solution is extremely costly. The technology disclosed in Patent Document 2 requires a re-extraction process using dilute acid to recover gold extracted by the metal extractant, which requires time and effort. Patent Document 2 does not disclose the use of a solvent system containing an organic solvent to dissolve precious metals. Nicotinamide, the active ingredient in Patent Document 3, dissolves in organic solvents and therefore must be supported on an insoluble material such as activated carbon. Furthermore, although nicotinamide has excellent selectivity for platinum group precious metals, it is not applicable to gold recovery.

[0007] No metal dissolving solution containing an organic solvent as a constituent has yet been proposed that is highly soluble in precious metals and that can adsorb the dissolved precious metals at a high adsorption rate when the dissolved precious metals are recovered with an adsorbent. Furthermore, no method has yet been proposed for recovering gold by repeatedly using this metal dissolving solution.

[0008] An object of the present disclosure is to provide a metal dissolving solution capable of dissolving precious metals, and capable of efficiently adsorbing the dissolved precious metals onto an adsorbent. Another object of the present disclosure is to provide a method for selectively and efficiently recovering gold using this metal dissolving solution. A further object of the present disclosure is to provide a method for recovering gold by repeatedly using this metal solution. [Means for solving the problem]

[0009] The metal dissolving solution according to the present disclosure contains a hydrophilic organic solvent, a chlorine compound, and an oxidizing agent. The chlorine compound dissolves in the hydrophilic organic solvent to produce chloride ions (Cl - ) has the property of generating

[0010] The gold recovery method according to the present disclosure comprises: (1) dissolving gold in the metal dissolving solution to obtain a composition containing the metal dissolving solution and dissolved gold; (2) contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; and (3) recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; This gold recovery method is (4) Reusing the metal solution in the composition by further dissolving gold in the composition after separating the gold-containing adsorbent; may further comprise: [Effects of the Invention]

[0011] The metal dissolving solution according to the present disclosure has excellent solubility for precious metals. The precious metals dissolved in this metal dissolving solution are easily adsorbed by the adsorbent upon contact with the adsorbent. According to the gold recovery method according to the present disclosure, which uses this metal dissolving solution, the dissolved gold can be efficiently recovered using the adsorbent. Furthermore, according to the gold recovery method according to the present disclosure, even a used metal dissolving solution has excellent gold solubility. This gold recovery method allows the metal dissolving solution to be reused. DETAILED DESCRIPTION OF THE INVENTION

[0012] An example of a preferred embodiment will be described in detail below. Each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. The present disclosure is not limited by the embodiments, but only by the scope of the claims. Furthermore, each aspect disclosed in this specification can be combined with any other feature disclosed in this specification.

[0013] The numerical range of each requirement disclosed herein can be arbitrarily combined with the numerical range of other requirements. For example, the numerical range limit for the content of chlorine compounds in the metal-dissolving solution can be combined with the numerical range limit for the amount of oxidizing agent. Furthermore, the numerical range of each requirement disclosed herein can be any range obtained by arbitrarily combining the upper and lower limits.

[0014] In this specification, the term "X to Y" indicating a range means "X or more and Y or less," "ppm" means "ppm by mass," and "%" means "% by mass (wt.%)." Furthermore, "% by mass" refers to weight percent, and does not mean mass concentration. Furthermore, "X' and / or Y'" means "at least one selected from the group consisting of X' and Y'," and includes all of [1] to [3] of "[1] X' only, [2] Y' only, and [3] both X' and Y'." Unless otherwise noted, all test temperatures in this specification are room temperature (20°C ± 5°C).

[0015] (metal solution) The metal dissolving solution of the present disclosure contains a hydrophilic organic solvent and a chlorine compound. The chlorine compound dissolves in water to produce chlorine ions (Cl - Specifically, the metal-dissolving solution of the present disclosure is a solution containing a chlorine compound as a solute and a hydrophilic organic solvent as a solvent.

[0016] The metal dissolving liquid of the present disclosure is capable of dissolving precious metals. Specifically, the metal dissolving liquid of the present disclosure is a liquid containing a hydrophilic organic solvent and is capable of dissolving precious metals. Here, "precious metal" refers to gold (Au), silver (Ag), platinum (Pt), palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), and osmium (Os). However, the metal dissolving liquid of the present disclosure is not limited to these elemental precious metals. That is, the metal dissolving liquid of the present disclosure can dissolve elemental precious metals selected from the group consisting of gold, silver, platinum, palladium, iridium, rhodium, ruthenium, and osmium, as well as alloys of precious metals containing at least one selected from the group consisting of gold, silver, platinum, palladium, iridium, rhodium, ruthenium, and osmium. In particular, the metal dissolving liquid of the present disclosure is suitable for dissolving gold.

[0017] Dissolving a precious metal with the metal dissolving solution of the present disclosure results in a composition containing the dissolved precious metal and the metal dissolving solution. Adding an adsorbent to this composition causes the dissolved precious metal to be adsorbed onto the adsorbent, thereby recovering the precious metal. That is, the metal dissolving solution of the present disclosure can be used to recover precious metals using an adsorbent. The metal dissolving solution of the present disclosure is particularly suitable for dissolving gold and recovering it using an adsorbent. Furthermore, this metal dissolving solution can be used to further dissolve precious metals after recovering them using an adsorbent. The metal dissolving solution of the present disclosure can be repeatedly used in a precious metal recovery cycle that includes dissolving precious metals and adsorbing (recovering) the dissolved precious metals using an adsorbent, without requiring any additional purification or regeneration processes. The metal dissolving solution of the present disclosure allows for simple and efficient recovery of precious metals.

[0018] (hydrophilic organic solvent) A hydrophilic organic solvent is one of the main components of the metal-dissolving liquid of the present disclosure. In this specification, "organic solvent" refers to an organic compound that is liquid at room temperature, and may also be referred to as "organic solvent." Here, "liquid" refers to a state in which the organic solvent is fluid at room temperature (15 to 35°C). More specifically, the organic solvent refers to an organic compound that is fluid at room temperature and normal pressure (e.g., 15 to 35°C, 1 atmosphere). A "hydrophilic organic solvent" refers to an organic solvent that is miscible with water or soluble in water.

[0019] The hydrophilic organic solvent that is a component of the metal-dissolving solution is preferably a polar solvent, and may be either an aprotic polar solvent or a protic polar solvent.

[0020] From another perspective, the hydrophilic organic solvent may be an organic solvent having a heteroatom selected from the group consisting of a nitrogen atom (N), a sulfur atom (S), and an oxygen atom (O).

[0021] Specific examples of hydrophilic organic solvents include N-methylpyrrolidone, acetonitrile, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), acetone, tetrahydrofuran, propylene carbonate, methanol, ethanol, 2-propanol, n-butanol, tert-butyl alcohol, and benzyl alcohol. The type of hydrophilic organic solvent can be selected depending on the type of noble metal to be dissolved. From the viewpoint of easily achieving the effects of the present disclosure, a preferred hydrophilic organic solvent is at least one selected from the group consisting of N-methylpyrrolidone, acetonitrile, and methanol.

[0022] The content of the hydrophilic organic solvent in the metal-dissolving liquid may be 5% by mass to 98% by mass, 5% by mass to 97% by mass, 5% by mass to 95% by mass, 5% by mass to 90% by mass, 5% by mass to 80% by mass, 10% by mass to 98% by mass, 10% by mass to 97% by mass, 10% by mass to 95% by mass, 10% by mass to 90% by mass, 10% by mass to 80% by mass, 20% by mass to 98% by mass, or 20% by mass to 97% by mass, based on the total amount of the metal-dissolving liquid. The metal-dissolving solution may be 20% by mass to 95% by mass, 20% by mass to 90% by mass, 20% by mass to 80% by mass, 25% by mass to 98% by mass, 25% by mass to 97% by mass, 25% by mass to 95% by mass, 25% by mass to 90% by mass, 25% by mass to 80% by mass, 30% by mass to 98% by mass, 30% by mass to 97% by mass, 30% by mass to 95% by mass, 30% by mass to 90% by mass, or 30% by mass to 80% by mass. A metal-dissolving solution containing a hydrophilic organic solvent in this range has excellent solubility for precious metals.

[0023] (chlorine compounds) The chlorine compound is one of the main components of the metal-dissolving solution of the present disclosure. As mentioned above, in this specification, the term "chlorine compound" refers to a compound dissolved in the hydrophilic organic solvent and containing chlorine ions (Cl - ) is defined as a compound that generates

[0024] The preferred chloride compound is at least one selected from the group consisting of alkali metal chlorides, alkaline earth metal chlorides, transition metal chlorides, and amine hydrochlorides. Examples of alkali metal chlorides include lithium chloride (LiCl), potassium chloride (KCl), and sodium chloride (NaCl). Examples of alkaline earth metal chlorides include calcium chloride (CaCl), magnesium chloride (MgCl), barium chloride (BaCl), and strontium chloride (SrCl). Examples of first transition metal chlorides include copper chloride (CuCl), iron chloride (FeCl), and manganese chloride (MnCl). Examples of amine hydrochlorides include trimethylamine hydrochloride, triethylamine hydrochloride, and triethanolamine hydrochloride. Alkali metal chlorides or amine hydrochlorides are more preferred, and at least one selected from the group consisting of sodium chloride and trimethylamine hydrochloride is even more preferred.

[0025] The content of the chlorine compound in the metal-dissolving liquid may be 0.001% by mass to 20% by mass, 0.001% by mass to 15% by mass, 0.001% by mass to 10% by mass, 0.001% by mass to 5% by mass, 0.005% by mass to 20% by mass, 0.005% by mass to 15% by mass, 0.005% by mass to 10% by mass, 0.005% by mass to 5% by mass, or 0.01% by mass to 20% by mass, relative to the entire metal-dissolving liquid. The concentration may be, for example, 0.01% by mass to 15% by mass, 0.01% by mass to 10% by mass, 0.01% by mass to 5% by mass, 0.05% by mass to 20% by mass, 0.05% by mass to 15% by mass, 0.05% by mass to 10% by mass, 0.05% by mass to 5% by mass, 0.5% by mass to 20% by mass, 0.5% by mass to 15% by mass, 0.5% by mass to 10% by mass, or 0.5% by mass to 5% by mass. A precious metal dissolved in a metal-dissolving solution containing a chlorine compound within this range is efficiently adsorbed onto the adsorbent. This metal-dissolving solution allows the adsorbent to be used to recover the dissolved precious metal. Furthermore, when the metal-dissolving solution of the present disclosure is used for etching a semiconductor substrate or the like, the chlorine compound contained within this range does not excessively affect materials other than the target to be etched.

[0026] (oxidizing agent) The oxidizing agent is one of the main components of the metal-dissolving solution of the present disclosure. The inclusion of an oxidizing agent in the metal-dissolving solution improves the solubility of the precious metal. Preferably, the metal-dissolving solution of the present disclosure includes an oxidizing agent other than copper halide.

[0027] Examples of oxidizing agents contained in the metal-dissolving solution include halogen molecules (X, where X=I, Br, Cl, etc.) such as iodine molecules (I), bromine molecules (Br), and chlorine molecules (Cl). Iodine molecules (I) and / or chlorine molecules (Cl) are more preferred, and iodine molecules (I) are even more preferred.

[0028] The content of the oxidizing agent in the metal-dissolving liquid may be 0.01% by mass to 20% by mass, 0.01% by mass to 18% by mass, 0.01% by mass to 15% by mass, 0.01% by mass to 10% by mass, 0.1% by mass to 20% by mass, 0.1% by mass to 18% by mass, 0.1% by mass to 15% by mass, 0.1% by mass to 10% by mass, 1.0% by mass to 20% by mass, 1.0% by mass to 18% by mass, 1.0% by mass to 15% by mass, or 1.0% by mass to 10% by mass, based on the total amount of the metal-dissolving liquid. A metal-dissolving liquid containing an oxidizing agent in this range is easy to use for dissolving precious metals and has excellent solubility.

[0029] (Other additives) When the metal dissolving solution contains halogen molecules (X2, X=I, Br, Cl, etc.) as an oxidizing agent, the metal dissolving solution may further contain a halide. In a metal dissolving solution containing a halide, the halogen consumed as an oxidizing agent when dissolving the precious metal is replenished. This maintains the solubility of the precious metal. A halide containing the same halogen as the halogen molecules serving as the oxidizing agent is preferred.

[0030] For example, when the metal dissolving solution contains iodine molecules (I2) as an oxidizing agent, the metal dissolving solution preferably further contains an iodine compound. The iodine compound is preferably at least one selected from the group consisting of alkali metal iodides, alkaline earth metal iodides, and ammonium iodides. Examples of alkali metal iodides include lithium iodide (LiI), potassium iodide (KI), and sodium iodide (NaI). Examples of alkaline earth metal iodides include calcium iodide (CaI2), magnesium iodide (MgI2), barium iodide (BaI2), and strontium iodide (SrI2). In this specification, "ammonium" refers to ammonium (NH4 + ) and organic ammonium (quaternary ammonium, NR4 + , R=hydrocarbon group). Examples of ammonium iodides include ammonium iodide and tetrabutylammonium iodide.

[0031] When the metal-dissolving liquid contains a halide, the content of the halide may be 0.01% by mass to 20% by mass, 0.01% by mass to 18% by mass, 0.01% by mass to 15% by mass, 0.01% by mass to 10% by mass, 0.1% by mass to 20% by mass, 0.1% by mass to 18% by mass, 0.1% by mass to 15% by mass, 0.1% by mass to 10% by mass, 1.0% by mass to 20% by mass, 1.0% by mass to 18% by mass, 1.0% by mass to 15% by mass, 1.0% by mass to 10% by mass, 5.0% by mass to 20% by mass, 5.0% by mass to 18% by mass, 5.0% by mass to 15% by mass, or 5.0% by mass to 10% by mass, relative to the entire metal-dissolving liquid. A metal dissolving solution containing a halide in this range maintains excellent noble metal solubility for a long period of time.

[0032] As long as the effects of the present disclosure are achieved, the metal-dissolving liquid may or may not contain water. When the metal-dissolving liquid contains water, the amount of water may be greater than 0% by mass and less than 70% by mass, greater than 0% by mass and less than 65% by mass, greater than 0% by mass and less than 60% by mass, greater than 0% by mass and less than 55% by mass, 1% by mass or more and less than 70% by mass, 1% to 65% by mass, 1% to less than 60% by mass, 1% to 55% by mass, 5% by mass or more and less than 70% by mass, 5% to 65% by mass, 5% to less than 60% by mass, 5% to 55% by mass, 10% by mass or more and less than 70% by mass, 10% to 65% by mass, 10% to less than 60% by mass, or 10% to 55% by mass. A metal-dissolving liquid containing water within this range has excellent solubility for precious metals.

[0033] (Application) The metal-dissolving liquid of the present disclosure can be used in applications for dissolving precious metals, replacing conventional aqua regia. In particular, the metal-dissolving liquid of the present disclosure can be used for dissolving gold. For example, it is used for recovering precious metals from used electrical and electronic devices, extracting precious metals from ores, etc. The metal-dissolving liquid of the present disclosure can also be used as an etching liquid for semiconductor manufacturing. For example, the metal-dissolving liquid of the present disclosure can be used to form a fine pattern by etching the surface of a workpiece made of a material containing precious metals in the manufacturing process of semiconductor devices.

[0034] (Method of collecting gold) As described above, the metal-dissolving liquid of the present disclosure has excellent solubility for gold, and is suitable for use in a method for recovering gold. In other words, in a first embodiment, the gold recovery method of the present disclosure comprises: (1) dissolving gold in the aforementioned metal-dissolving solution to obtain a composition containing the metal-dissolving solution and dissolved gold, (2) contacting the obtained composition with an adsorbent to adsorb the dissolved gold onto the adsorbent to obtain a gold-containing adsorbent, and (3) separating the obtained gold-containing adsorbent from the composition to recover the gold in the gold-containing adsorbent. This gold recovery method may further comprise (4) dissolving more gold in the composition from which the gold-containing adsorbent has been separated, thereby reusing the metal-dissolving solution in the composition.

[0035] According to the gold recovery method of the present disclosure, gold can be easily dissolved in a metal-dissolving solution, and the gold dissolved in the metal-dissolving solution can be recovered by the simple method of adding an adsorbent. The gold recovery method of the present disclosure allows gold to be recovered simply and efficiently. Furthermore, in this embodiment, gold can be further dissolved using the metal-dissolving solution after separation of the gold-containing adsorbent. According to this recovery method, the metal-dissolving system can be repeatedly used in a gold recovery cycle that includes gold dissolution and gold adsorption (recovery) by the adsorbent, without the need for additional purification or regeneration treatment of the metal-dissolving solution.

[0036] A first preferred embodiment of the present disclosure will be described below in order.

[0037] In the process of dissolving gold in a metal dissolving solution, a hydrophilic organic solvent and chloride ions (Cl) dissolved in the hydrophilic organic solvent are used. - A material containing gold is introduced into a metal-dissolving solution containing a chlorine compound having the property of generating HCl and an oxidizing agent, and the gold in the material is dissolved in the metal-dissolving solution. The hydrophilic organic solvent, chlorine compound, and oxidizing agent described above for the metal-dissolving solution are preferably used. When the metal-dissolving solution contains halogen molecules as the oxidizing agent, it may further contain a halide. The metal-dissolving solution may or may not further contain water.

[0038] Examples of materials containing gold include used electronic devices and their components, scraps from decorative items, waste catalysts, etc. Also, semiconductors that use gold as the material for bonding wires to connect electrodes of IC chips to lead frames can be used as materials containing gold.

[0039] Dissolving gold in a metal-dissolving solution yields a composition containing the metal-dissolving solution and dissolved gold. This composition is typically liquid and contains a hydrophilic organic solvent, a chlorine compound, an oxidizing agent, and dissolved gold. The gold concentration in the composition is not particularly limited, but may be, for example, 1 ppm to 2000 ppm, 1 ppm to 1000 ppm, 1 ppm to 500 ppm, 1 ppm to 200 ppm, 10 ppm to 2000 ppm, 10 ppm to 1000 ppm, 10 ppm to 500 ppm, 10 ppm to 200 ppm, 20 ppm to 2000 ppm, 20 ppm to 1000 ppm, 20 ppm to 500 ppm, or 20 ppm to 200 ppm, based on the total composition. The composition may further contain a reaction product derived from the oxidizing agent. The composition may further contain water, or may not contain water. When the composition contains water, the amount of water in the composition may be 0% by mass to less than 70% by mass, 0% by mass to 50% by mass, or 0% by mass to 20% by mass, based on the total mass of the composition. A composition containing water in this range exhibits a high gold adsorption rate by the adsorbent and excellent solubility of the precious metal after separation from the gold-containing adsorbent.

[0040] In the gold recovery method of the present disclosure, the resulting composition is brought into contact with an adsorbent, thereby allowing dissolved gold in the composition to be adsorbed onto the adsorbent. Contact between the composition and the adsorbent can be achieved, for example, by adding the adsorbent to the composition and mixing, or by passing the composition through a column packed with the adsorbent. All of the dissolved gold in the composition may be adsorbed onto the adsorbent, or only a portion of the gold in the composition may be adsorbed onto the adsorbent, or gold not adsorbed onto the adsorbent may remain in the composition.

[0041] The type of adsorbent is not particularly limited, but an adsorbent that can selectively adsorb gold in a composition containing an organic solvent is preferred. The adsorbent is usually solid, and preferably porous. Adsorbents in various shapes, such as powder, granules, and fibers, can be used.

[0042] From the viewpoint of high gold adsorption efficiency, the adsorbent material is preferably at least one selected from the group consisting of cellulose derivatives, ion exchange resins, and activated carbon, with cellulose derivatives being more preferred as the adsorbent material.

[0043] In this specification, "cellulose derivative" is defined as a general term for compounds in which various substituents have been introduced into at least some of the hydroxyl groups in cellulose. Preferred cellulose derivatives are cellulose esters in which at least some of the hydroxyl groups in cellulose have been esterified. Cellulose esters with a total degree of substitution of 0.8 to 2.9 are more preferred. From the viewpoint of being able to selectively adsorb gold, the total degree of substitution of the cellulose ester may be 0.8 to 2.9, may be 1.0 to 2.9, may be 1.2 to 2.9, may be 1.5 to 2.9, may be 1.8 to 2.9, may be 2.0 to 2.9, may be 2.3 to 2.9, may be 0.8 to 2.8, may be 1.0 to 2.8, may be 1.2 to 2.8, may be 1.5 to 2.8, may be 1.8 to 2.8, may be 2.0 to 2.8, may be 2.3 to 2.8, may be 0.8 to 2.7, may be 1.0 to 2.7, may be 1.2 to 2.7, may be 1.5 to 2.7, may be 1.8 to 2.7, may be 2.0 to 2.7, or may be 2.3 to 2.7. The total degree of substitution of a cellulose ester is the sum of the degrees of substitution at the 2-, 3-, and 6-positions of the glucose ring of the cellulose ester, and can be measured, for example, by NMR according to the method of Tezuka (Tezuka, Carbonydr. Res. 273, 83 (1995)).

[0044] Preferably, the cellulose derivative is cellulose acylate in which at least a portion of the hydroxyl groups in cellulose are substituted with acyl groups having a carbon number of 2 to 40. The number of carbon atoms in the acyl groups of the cellulose ester may be 2 to 30, 2 to 20, 2 to 10, 2 to 5, or 2 to 3. From the viewpoint of being able to selectively adsorb gold, the degree of substitution with acyl groups of cellulose acylate may be 0.8 to 2.9, may be 1.0 to 2.9, may be 1.2 to 2.9, may be 1.5 to 2.9, may be 1.8 to 2.9, may be 2.0 to 2.9, may be 2.3 to 2.9, may be 0.8 to 2.8, may be 1.0 to 2.8, may be 1.2 to 2.8, may be 1.5 to 2.8, may be 1.8 to 2.8, may be 2.0 to 2.8, may be 2.3 to 2.8, may be 0.8 to 2.7, may be 1.0 to 2.7, may be 1.2 to 2.7, may be 1.5 to 2.7, may be 1.8 to 2.7, may be 2.0 to 2.7, or may be 2.3 to 2.7. The degree of substitution by acyl groups in cellulose acylate is the sum of the degrees of acyl substitution at the 2-, 3- and 6-positions of the glucose ring of the cellulose ester, and can be determined in the same manner as in the measurement of the total degree of substitution of the cellulose derivative described above.

[0045] Preferably, the cellulose derivative is cellulose acetate in which at least a portion of the hydroxyl groups in cellulose are substituted with acetyl groups, and more preferably, cellulose acetate having an acetyl substitution degree of 0.8 or more and 2.9 or less. From the viewpoint of being able to selectively adsorb gold, the degree of acetyl substitution of cellulose acetate may be 0.8 to 2.9, may be 1.0 to 2.9, may be 1.2 to 2.9, may be 1.5 to 2.9, may be 1.8 to 2.9, may be 2.0 to 2.9, may be 2.3 to 2.9, may be 0.8 to 2.8, may be 1.0 to 2.8, may be 1.2 to 2.8, may be 1.5 to 2.8, may be 1.8 to 2.8, may be 2.0 to 2.8, may be 2.3 to 2.8, may be 0.8 to 2.7, may be 1.0 to 2.7, may be 1.2 to 2.7, may be 1.5 to 2.7, may be 1.8 to 2.7, may be 2.0 to 2.7, or may be 2.3 to 2.7. The degree of acetyl substitution of a cellulose ester is the sum of the degrees of acetyl substitution at the 2-, 3- and 6-positions of the glucose ring of the cellulose ester, and can be determined in the same manner as in the measurement method described above for the total degree of substitution of a cellulose derivative.

[0046] When the material of the adsorbent is cellulose acetate, the cellulose acetate may contain other substituents besides acetyl groups, as long as the effects of the present disclosure are obtained. Examples of such other substituents include acyl groups such as propionyl, butyryl, pentanoyl (valeryl), hexanoyl, heptanoyl, octanoyl, nonanoyl, undecanoyl, dodecanoyl, tridecanoyl, tetradecanoyl (myristoyl), pentadecanoyl, hexadecanoyl, heptadecanoyl, and octadecanoyl (stearoyl).

[0047] In this specification, the term "ion exchange resin" refers to a resin made of a crosslinked polymer having ion exchange groups and containing counterions exchangeable with the target ions. The type of ion exchange resin may be selected appropriately depending on the type of target ions, as long as it is capable of ion exchange in the presence of an organic solvent. Examples of ion exchange resins include polyolefins, (meth)acrylic resins, styrene resins, polyacetals, polyesters, polycarbonates, polyamides, polyamideimides, polyimides, polyethers, polyetherimides, polyetherketones, polyetheretherketones, polysulfones, polyethersulfones, polyphenylene sulfides, and fluororesins, each of which has an ion exchange group. Examples of ion exchange groups include sulfonic acid groups, carboxyl groups, phosphate groups, primary amino groups, secondary amino groups, tertiary amino groups, and quaternary ammonium groups. Anion exchange resins capable of exchanging negative ions are particularly preferred.

[0048] In this specification, "activated carbon" is defined as a material that is substantially composed of carbon and has a plurality of pores on its surface. The type of activated carbon is not particularly limited, and commercially available known activated carbon can be appropriately selected and used regardless of origin, activation method, shape, etc. For example, activated carbon of mineral origin, activated carbon of plant origin, activated carbon of resin origin, steam-activated activated carbon, or chemically activated activated carbon can be appropriately selected. The shape of the activated carbon can be appropriately selected from powder, granular, crushed, fibrous, honeycomb, etc.

[0049] When activated carbon is selected as the adsorbent material, the specific surface area of the activated carbon should be 200 to 3500 m 2 / g is preferred, and 400 to 2000m 2 / g is more preferable, and 800 to 2000m 2 The total pore volume of the activated carbon is preferably 0.1 to 2 ml / g, more preferably 0.2 to 1.6 ml / g, and even more preferably 0.2 to 0.8 ml / g.

[0050] The amount of adsorbent added can be appropriately selected depending on the type of adsorbent. From the viewpoint of efficiently adsorbing gold, the amount of adsorbent added may be 1 g / L to 1000 g / L, 1 g / L to 500 g / L, 1 g / L to 300 g / L, 1 g / L to 200 g / L, 1 g / L to 100 g / L, 2 g / L to 1000 g / L, 2 g / L to 500 g / L, 2 g / L to 300 g / L, 2 g / L to 200 g / L, 2 g / L to 100 g / L, 5 g / L to 1000 g / L, or 5 g / L to 500 g / L. The concentration may be 5 g / L to 300 g / L, 5 g / L to 200 g / L, 5 g / L to 100 g / L, 10 g / L to 1000 g / L, 10 g / L to 500 g / L, 10 g / L to 300 g / L, 10 g / L to 200 g / L, 10 g / L to 100 g / L, 15 g / L to 1000 g / L, 15 g / L to 500 g / L, 15 g / L to 300 g / L, 15 g / L to 200 g / L, or 15 g / L to 100 g / L.

[0051] In the gold recovery method disclosed herein, contacting an adsorbent with a composition generally results in preferential adsorption of dissolved gold in the composition to the adsorbent. However, in rare cases, substances other than gold derived from oxidizing agents or chlorine compounds (e.g., halogen ions such as chloride ions, halogen molecules, etc.) may be adsorbed. In this case, adsorption of substances other than gold in the composition can be suppressed by adsorbing the target substance (oxidizing agent- or chlorine compound-derived substance) to the adsorbent before contacting the adsorbent with the composition. Furthermore, in the step described below, the corresponding substance (oxidizing agent- or chlorine compound-derived substance) may be replenished after separating the gold-containing adsorbent from the composition. In other words, the gold recovery method disclosed herein may further include a step of adsorbing oxidizing agent-derived substances and / or chlorine compound-derived substances to the adsorbent before contacting the composition with the adsorbent, or a step of adding oxidizing agent-derived substances and / or chlorine compound-derived substances to the adsorbent before dissolving gold in the composition after separation of the gold-containing adsorbent.

[0052] By contacting the composition with an adsorbent, a gold-containing adsorbent is obtained, to which the gold in the composition has been adsorbed. By separating this gold-containing adsorbent from the composition, the gold adsorbed by the gold-containing adsorbent can be recovered.

[0053] The method for separating the gold-containing adsorbent is not particularly limited, and a general solid-liquid separation method can be used. Examples of solid-liquid separation methods include filtration, centrifugation, and sedimentation. From the viewpoint of improving the gold recovery rate and the reuse rate of the metal-dissolving solution described below, a method that minimizes the amount of the liquid component adhering to the gold-containing adsorbent separated as a solid is preferred.

[0054] As a method for recovering gold from a gold-containing adsorbent, for example, gold may be liberated from the gold-containing adsorbent using an eluent and the gold eluted into the eluent may be recovered, or the gold-containing adsorbent may be incinerated and the gold recovered as an incineration residue. Examples of methods using an eluent include passing the eluent through a gold-containing adsorbent packed in a column, and introducing the gold-containing adsorbent into the eluent and stirring it.

[0055] The type of desorption liquid can be selected depending on the type of adsorbent. For example, in the case of an adsorbent made of a cellulose derivative, preferred desorption liquids are water, an aqueous sodium chloride solution, etc.

[0056] The composition after separation of the gold-containing adsorbent (hereinafter sometimes referred to as the "post-separation composition") contains a hydrophilic organic solvent and chloride ions (Cl) dissolved in the hydrophilic organic solvent. - The adsorbent contains a chlorine compound having the property of generating a chlorine-containing compound (a chlorine compound), and an oxidizing agent. In other words, the composition after separation of the gold-containing adsorbent contains a metal-dissolved solution. The separated composition may contain gold that was not adsorbed by the adsorbent. In other words, the separated composition may contain both a metal-dissolved solution and dissolved gold.

[0057] The post-separation composition containing the metal-dissolving solution can dissolve gold. According to the present disclosure, the metal-dissolving solution in the composition can be reused to dissolve gold without purification or regeneration of the post-separation composition, or with simple processing such as adding a small amount of additive (oxidizer or chlorine compound). That is, the gold recovery method of the present disclosure involves reusing the metal-dissolving solution in the composition by further dissolving gold in the composition from which the gold-containing adsorbent has been separated. According to the gold recovery method of the present disclosure, the metal-dissolving solution can be reused and gold can be efficiently recovered by repeatedly dissolving gold in the post-separation composition to obtain a composition containing dissolved gold, contacting this composition with an adsorbent to obtain a gold-containing adsorbent, separating the gold-containing adsorbent to obtain a post-separation composition, and further dissolving gold in the post-separation composition.

[0058] Preferably, the content of the hydrophilic organic solvent in the composition after separation of the gold-containing adsorbent (hereinafter referred to as the "post-separation composition") may be 5% by mass or more and less than 100% by mass, 5% by mass to 90% by mass, 5% by mass to 80% by mass, 5% by mass to 70% by mass, 10% by mass or more and less than 100% by mass, 10% by mass to 90% by mass, 10% by mass to 80% by mass, 10% by mass to 70% by mass, or 20% by mass or more, based on the total post-separation composition. The content may be at most but less than 100% by mass, 20% to 90% by mass, 20% to 80% by mass, 20% to 70% by mass, 25% to 100% by mass, 25% to 90% by mass, 25% to 80% by mass, 25% to 70% by mass, 30% to 100% by mass, 30% to 90% by mass, 30% to 80% by mass, or 30% to 70% by mass. A post-separation composition containing a hydrophilic organic solvent in this range has excellent gold solubility.

[0059] The content of chlorine compounds in the composition (post-separation composition) after separation of the gold-containing adsorbent may be 0.001% to 10% by mass, 0.001% to 5% by mass, 0.001% to 1% by mass, 0.005% to 10% by mass, 0.005% to 5% by mass, 0.005% to 1% by mass, 0.01% to 10% by mass, 0.01% to 5% by mass, 0.01% to 1% by mass, 0.05% to 10% by mass, 0.05% to 5% by mass, or 0.05% to 1% by mass, based on the total post-separation composition. Precious metals dissolved in the post-separation composition containing chlorine compounds within this range are efficiently adsorbed by the adsorbent. This post-separation composition allows the adsorbent to be used to recover dissolved precious metals.

[0060] The content of the oxidizing agent in the composition after separation of the gold-containing adsorbent (post-separation composition) may be 0.001% to 20% by mass, 0.001% to 15% by mass, 0.001% to 10% by mass, 0.01% to 20% by mass, 0.01% to 15% by mass, 0.01% to 10% by mass, 0.1% to 20% by mass, 0.1% to 15% by mass, 0.1% to 10% by mass, 0.5% to 20% by mass, 0.5% to 15% by mass, or 0.5% to 10% by mass, based on the total post-separation composition. The post-separation composition containing an oxidizing agent in this range is easy to use for dissolving precious metals and has excellent solubility.

[0061] When the composition after separation of the gold-containing adsorbent (post-separation composition) contains a halogen molecule (X2, X=I, Br, Cl, etc.) as an oxidizing agent, the post-separation composition may further contain a halide. When the post-separation composition contains a halide, the content of the halide may be 0.001% to 20% by mass, 0.001% to 15% by mass, 0.001% to 10% by mass, 0.01% to 20% by mass, 0.01% to 15% by mass, 0.01% to 10% by mass, 0.1% to 20% by mass, 0.1% to 15% by mass, 0.1% to 10% by mass, 0.5% to 20% by mass, 0.5% to 15% by mass, or 0.5% to 10% by mass, based on the total post-separation composition. In post-separation compositions containing halides in this range, gold solubility is maintained for extended periods of time.

[0062] As long as the effects of the present disclosure are obtained, the composition after separation of the gold-containing adsorbent (post-separation composition) may or may not contain water. When the post-separation composition contains water, the amount of water may be greater than 0% by mass but less than 70% by mass, greater than 0% by mass but less than 50% by mass, greater than 0% by mass but less than 30% by mass, greater than 0% by mass but less than 20% by mass, 1% by mass or more but less than 70% by mass, 1% by mass or more but less than 50% by mass, 1% by mass or more but less than 30% by mass, 1% by mass or more but less than 20% by mass, 5% by mass or more but less than 70% by mass, 5% by mass or more but less than 50% by mass, 1% by mass or more but less than 30% by mass, or 1% by mass or more but less than 20% by mass. Post-separation compositions containing water within these ranges have excellent gold solubility.

[0063] In a second embodiment of the gold recovery method of the present disclosure, gold may be dissolved in a solution containing a hydrophilic organic solvent and an oxidizing agent, and then a chlorine compound may be added before contacting the solution with an adsorbent. This produces a composition containing dissolved gold and a hydrophilic organic solvent, an oxidizing agent, and a chlorine compound (i.e., the metal solution of the present disclosure). Contacting this composition with an adsorbent allows for efficient gold recovery, and furthermore, the effects of the present disclosure, such as the ability to reuse the metal solution, are achieved.

[0064] That is, the gold recovery method according to the second embodiment comprises the following steps: (1) preparing a solution containing a hydrophilic organic solvent and an oxidizing agent; (2) dissolving gold in the solution to obtain a first composition containing the solution and dissolved gold; (3) Adding chloride ions (Cl) dissolved in a hydrophilic organic solvent to the first composition - to obtain the metal solution and a second composition containing dissolved gold; (4) contacting the second composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; and (5) recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the second composition; The gold recovery method of this aspect comprises: (6) Reusing the metal solution in the second composition by further dissolving gold in the second composition after separating the gold-containing adsorbent. may further comprise: For the types and amounts of the hydrophilic organic solvent, oxidizing agent, and chlorine compound in this embodiment, reference can be made to the contents described above for the first embodiment in this specification. [Example]

[0065] The present disclosure will be specifically described below using examples, but the technical scope of the present disclosure is not limited to these examples. Unless otherwise specified, the test temperature was room temperature.

[0066] [Example 1] (Preparation of metal solution) Metal-dissolved solution (1) was prepared by mixing N-methylpyrrolidone (Kanto Chemical Co., Ltd., 36% by weight), iodine (I2, Kanto Chemical Co., Ltd., 3% by weight), ammonium iodide (Fujifilm Wako Pure Chemical Industries, Ltd., 7% by weight), water (50% by weight), and sodium chloride (Tokyo Chemical Industry Co., Ltd., 4% by weight). The composition of this metal-dissolved solution (1) is shown in Table 1 below.

[0067] (Dissolution test) A gold wire (φ=0.20 mm, purity 99.95%, manufactured by Nilaco Corporation) was added to the obtained metal-dissolved solution (1) to obtain a composition (1) containing dissolved gold at a concentration of 1600 ppm. The amount of water and the concentration of dissolved gold in this composition (1) are shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively.

[0068] (Adsorption test) Adsorbent A (cellulose acetate, acetyl substitution degree 2.5) was added to the resulting composition (1) to adsorb the gold dissolved in composition (1). The amount of adsorbent A added was 20 g (g / L) relative to composition (1). After stirring at room temperature for 3 hours, the gold-adsorbed adsorbent A (gold-containing adsorbent) was subjected to solid-liquid separation, and the gold concentration in the liquid phase was measured. To measure the gold concentration, an inductively coupled plasma (ICP) emission spectrum was measured using an inductively coupled plasma optical emission spectrometer (trade name "Agilent 5110" manufactured by Agilent Technologies). The gold concentration before adsorption was defined as M1 (ppm) and the gold concentration after adsorption as M2 (ppm), and the gold adsorption rate X (%) by the adsorbent was calculated using the following formula. The results are shown in Table 1 below as "Gold Adsorption Rate (%)." X(wt%)=(M1(ppm)-M2(ppm)) / M1(ppm)×100

[0069] (Redissolution test) After the adsorption test, the gold-containing adsorbent was separated, yielding composition (1') containing a metal solution. Approximately 10 mg of gold wire (Φ=0.20 mm, purity 99.95%, manufactured by Nilaco Corporation) was added to composition (1') and immersed overnight. The state of gold dissolution in composition (1') was then visually observed. In Table 1 below, a circle in the "Redissolution of gold wire" column indicates that most of the gold wire dissolved.

[0070] [Example 2-3] A dissolution test, adsorption test, and redissolution test were carried out in the same manner as in Example 1, except that the composition of the metal-dissolving solution was changed to that shown in Table 1 below. The composition of the metal-dissolving solution and the results of the adsorption test and redissolution test are shown in Table 1 below. The water content and dissolved gold concentration of Composition (2) and Composition (3) obtained after the dissolution test are also shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively.

[0071] [Example 4] Dissolution tests, adsorption tests, and redissolution tests were carried out in the same manner as in Example 1, except that adsorbent B (an anion exchange resin manufactured by Organo Corporation) was used instead of adsorbent A. The composition of the metal-dissolving solution and the results of the adsorption test and redissolution test are shown in Table 1 below. The water content and dissolved gold concentration of composition (4) obtained after the dissolution test are also shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively.

[0072] [Comparative Example 1] A metal dissolving solution (C1) was prepared by mixing N-methylpyrrolidone (Kanto Chemical Co., Ltd., 38% by weight), iodine (I2, Kanto Chemical Co., Ltd., 3% by weight), ammonium iodide (Fujifilm Wako Pure Chemical Industries, Ltd., 7% by weight), and water (52% by weight). The composition of this metal dissolving solution is shown in Table 1 below. Using this metal-dissolving solution (C1), a dissolution test was carried out in the same manner as in Example 1. The water content and dissolved gold concentration of the resulting composition (C1) are shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively. Except for using the obtained composition (C1), an adsorption test and a redissolution test were carried out in the same manner as in Example 1. The results are shown in Table 1 below. In the adsorption test of Comparative Example 1, gold could not be recovered by the adsorbent, but in the redissolution test, it was confirmed that the gold wire dissolved after overnight immersion.

[0073] [Comparative Example 2-3] Composition (C1) was obtained in the same manner as in Comparative Example 1. By adding water to this composition (C1) in the amounts shown in Table 1, composition (C2) with a water content of 84 wt.% and a gold concentration of 533 ppm, and composition (C3) with a water content of 70 wt.% and a gold concentration of 1000 ppm were obtained. Adsorption tests and redissolution tests were carried out in the same manner as in Comparative Example 1, except that compositions (C2) and (C3) were used instead of composition (C1). The compositions of the metal-dissolving solutions and the results of the adsorption and redissolution tests are shown in Table 1 below. The water content and dissolved gold concentration of compositions (C2) and (C3) obtained after the dissolution tests are also shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively. In all of Comparative Examples 2 to 3, gold could not be recovered using the adsorbent, and in the redissolution test, there was no change in the appearance of the gold wire even after overnight immersion.

[0074] [Example 5] A dissolution test, adsorption test, and redissolution test were carried out in the same manner as in Example 1, except that a metal-dissolved solution (5) of the composition shown in Table 1 below was prepared without adding water. The composition of the metal-dissolved solution and the results of the adsorption test and redissolution test are shown in Table 1 below. The water content and dissolved gold concentration of composition (5) obtained after the dissolution test are also shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively.

[0075] [Examples 6-7] Dissolution tests, adsorption tests, and redissolution tests were carried out in the same manner as in Example 1, except that metal-dissolved solutions (6) and (7) were prepared using acetonitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), respectively, instead of N-methylpyrrolidone. The compositions of the metal-dissolved solutions and the results of the adsorption and redissolution tests are shown in Table 1 below. The water content and dissolved gold concentration of compositions (6) and (7) obtained after the dissolution tests are also shown in Table 1 below as "Water (in compositions)" and "Initial gold concentration (M1)," respectively.

[0076] [Example 8] Acetonitrile (Fujifilm Wako Pure Chemical Industries, Ltd., 36% by weight), chlorine gas (Cl2, 4% by weight), trimethylamine hydrochloride (Tokyo Chemical Industry Co., Ltd., 10% by weight), and water (50% by weight) were mixed to prepare a metal dissolving solution (8). The composition of this metal dissolving solution is shown in Table 1 below. A dissolution test, adsorption test, and redissolution test were carried out in the same manner as in Example 1, except that this metal-dissolving solution (8) was used. The results are shown in Table 1 below. The water content and dissolved gold concentration of composition (8) obtained after the dissolution test are also shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M1)," respectively. In Table 1, "TMA hydrochloride" refers to trimethylamine hydrochloride.

[0077] [Example 9] In Example 9, a liquid flow test was carried out instead of an adsorption test. The details are as follows. (Preparation of metal solution) A metal-dissolved solution (9) was prepared by mixing N-methylpyrrolidone (Kanto Chemical Co., Inc., 36% by weight), iodine (I2, Kanto Chemical Co., Inc., 3% by weight), ammonium iodide (Fujifilm Wako Pure Chemical Industries, Ltd., 7% by weight), water (50% by weight), and sodium chloride (Tokyo Chemical Industry Co., Ltd., 4% by weight). The composition of this metal-dissolved solution (9) was the same as the composition of the metal-dissolved solution (1) prepared in Example 1.

[0078] (Dissolution test) A gold wire (φ=0.20 mm, purity 99.95%, manufactured by Nilaco Corporation) was added to the obtained metal-dissolved solution (9) to obtain a composition (9) containing dissolved gold at a concentration of 1600 ppm. The amount of water in this composition (9) was 50% by mass.

[0079] (fluid flow test) A glass column (volume 3.9 ml) was placed vertically and packed with approximately 1.7 g of adsorbent A (cellulose acetate, degree of acetyl substitution 2.5) from the bottom to the top of the column to prepare a packed column. A separately prepared liquid with the same composition as the metal dissolving solution (9) was passed through the packed column using a metering pump at a flow rate of 3.9 ml / h for 2 hours, whereby the oxidizing agent and chlorine compound-derived substances in the liquid were adsorbed onto adsorbent A in the packed column. After that, the liquid flow was stopped and the liquid in the packed column was discharged. Then, composition (9) was passed through the packed column at a flow rate of 3.9 ml / h using a metering pump, and the liquid that flowed out of the packed column was collected as composition (9') containing a metal solution. 2.0 g of composition (9') was sampled, and the gold concentration in the liquid was measured in the same manner as in the adsorption test, and the gold adsorption rate by the adsorbent was calculated. The calculated gold adsorption rate was 45%.

[0080] (Redissolution test) Approximately 10 mg of gold wire (Φ=0.20 mm, purity 99.95%, manufactured by Nilaco Corporation) was placed in the composition (9') collected in the liquid flow test and immersed overnight, after which the state of dissolution of gold in the composition (9') was visually observed. As a result, it was confirmed that most of the gold wire had dissolved in the composition (9').

[0081] [Table 1]

[0082] As shown in Table 1, the metal dissolving solution of the example enabled the dissolved precious metal to be efficiently recovered by the adsorbent. Furthermore, as described above for Example 9, the liquid flow test also confirmed that the dissolved precious metal could be recovered by the adsorbent. Furthermore, it was confirmed that the precious metal could be dissolved even after the adsorption test and the liquid flow test.

[0083] On the other hand, in Comparative Example 1-3, which did not contain any chlorine compound, the dissolved precious metal could not be recovered by the adsorbent.

[0084] As described above, the metal-dissolving liquids of the Examples were evaluated higher than the metal-dissolving liquids of the Comparative Examples. These evaluation results clearly demonstrate the superiority of the present disclosure.

[0085] [Disclosure items] Each of the following sections discloses a preferred embodiment.

[0086] [Item 1] containing a hydrophilic organic solvent, a chlorine compound and an oxidizing agent, The chlorine compound is dissolved in the hydrophilic organic solvent to form chlorine ions (Cl - ) is a metal dissolving liquid that has the property of generating [Item 2] 2. The metal-dissolving solution according to item 1, wherein the hydrophilic organic solvent is an organic solvent having a heteroatom. [Item 3] 3. The metal-dissolving solution according to item 1 or 2, wherein the hydrophilic organic solvent is a polar solvent. [Item 4] 4. The metal-dissolving solution according to any one of items 1 to 3, wherein the hydrophilic organic solvent is at least one selected from the group consisting of N-methylpyrrolidone, acetonitrile, and methanol. [Item 5] 5. The metal-dissolving solution according to any one of items 1 to 4, wherein the chlorine compound is at least one selected from the group consisting of alkali metal chlorides, alkaline earth metal chlorides, and amine hydrochlorides. [Item 6] 6. The metal-dissolving solution according to any one of items 1 to 5, wherein the content of the chlorine compound is 0.001% by mass to 20% by mass with respect to the entire metal-dissolving solution. [Item 7] 7. The metal-dissolved solution according to any one of items 1 to 6, further comprising water, the amount of which is less than 70 mass % based on the total mass of the metal-dissolved solution. [Item 8] 8. The metal-dissolving solution according to any one of items 1 to 7, wherein the oxidizing agent is iodine molecules (I2) and / or chlorine molecules (Cl2). [Item 9] 9. The metal-dissolving solution according to any one of items 1 to 8, wherein the oxidizing agent is molecular iodine (I2) and further contains an iodine compound. [Item 10] Item 10. The metal-dissolving solution according to Item 9, wherein the iodine compound is at least one selected from the group consisting of alkali metal iodides, alkaline earth metal iodides, and ammonium iodides. [Item 11] 11. The metal dissolving solution according to any one of items 1 to 10, which is used in semiconductor manufacturing. [Item 12] 11. A method for producing a composition containing a metal-dissolving solution and dissolved gold by dissolving gold in the metal-dissolving solution according to any one of items 1 to 10. contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; and recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; A method of recovering gold. [Item 13] 11. A method for producing a composition containing a metal-dissolving solution and dissolved gold by dissolving gold in the metal-dissolving solution according to any one of items 1 to 10. contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; and further dissolving gold in the composition from which the gold-containing adsorbent has been separated, thereby reusing the metal-dissolved solution in the composition; A method of recovering gold. [Item 14] Item 14. The method for recovering gold according to Item 12 or 13, wherein the material of the adsorbent is at least one selected from the group consisting of cellulose derivatives, ion exchange resins, and activated carbon. [Item 15] Item 15. The method for recovering gold according to item 14, wherein the cellulose derivative is a cellulose ester having a total degree of substitution of 0.8 or more and 2.9 or less. [Item 16] Item 16. The method for recovering gold according to Item 14 or 15, wherein the cellulose derivative is cellulose acetate in which at least a portion of the hydroxyl groups in cellulose have been substituted with acetyl groups. [Industrial Applicability]

[0087] The metal-dissolving solution described above can be used to recover precious metals other than gold from used equipment, and can also be used as an etching solution for various precious metals.

Claims

1. a hydrophilic organic solvent, a chlorine compound, and an oxidizing agent; The chlorine compound is dissolved in the hydrophilic organic solvent to form chlorine ions (Cl － ) is a metal dissolving liquid that has the property of generating

2. The metal-dissolving solution according to claim 1 , wherein the hydrophilic organic solvent is an organic solvent having a heteroatom.

3. The metal-dissolving solution according to claim 1 , wherein the hydrophilic organic solvent is a polar solvent.

4. 2. The metal-dissolving solution according to claim 1, wherein the hydrophilic organic solvent is at least one selected from the group consisting of N-methylpyrrolidone, acetonitrile, and methanol.

5. 2. The metal-dissolving solution according to claim 1, wherein the chlorine compound is at least one selected from the group consisting of alkali metal chlorides, alkaline earth metal chlorides, and amine hydrochlorides.

6. 2. The metal-dissolving solution according to claim 1, wherein the content of the chlorine compound is 0.001% by mass to 20% by mass with respect to the entire metal-dissolving solution.

7. The metal-dissolving solution according to claim 1 , further comprising water, the amount of which is less than 70 mass % of the total amount of the metal-dissolving solution.

8. The oxidizing agent is iodine molecule (I ２ ) and / or chlorine molecules (Cl ２ 2. The metal-dissolving solution according to claim 1, wherein

9. The oxidizing agent is iodine molecule (I ２ 2. The metal-dissolving solution according to claim 1, further comprising an iodine compound.

10. 10. The metal-dissolving solution according to claim 9, wherein the iodine compound is at least one selected from the group consisting of alkali metal iodides, alkaline earth metal iodides, and ammonium iodides.

11. The metal dissolving solution according to claim 1, which is used in semiconductor manufacturing.

12. 10. A method for producing a composition comprising a metal-dissolving solution and dissolved gold by dissolving gold in the metal-dissolving solution according to claim 1. contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; and recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; A method of recovering gold.

13. 10. A method for producing a composition comprising a metal-dissolving solution and dissolved gold by dissolving gold in the metal-dissolving solution according to claim 1. contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; recovering gold from the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; and further dissolving gold in the composition from which the gold-containing adsorbent has been separated, thereby reusing the metal-dissolved solution in the composition; A method of recovering gold.

14. 14. The method for recovering gold according to claim 12 or 13, wherein the material of the adsorbent is at least one selected from the group consisting of cellulose derivatives, ion exchange resins, and activated carbon.

15. 15. The method for recovering gold according to claim 14, wherein the cellulose derivative is a cellulose ester having a total degree of substitution of 0.8 or more and 2.9 or less.

16. 15. The method for recovering gold according to claim 14, wherein the cellulose derivative is cellulose acetate in which at least a portion of the hydroxyl groups in the cellulose have been substituted with acetyl groups.

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