Metal dissolving solution and method for recovering gold

Abstract

This 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. This method for recovering gold includes: (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 to 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 include (4) reusing the metal dissolving solution in the composition by further dissolving gold in the composition after separating the gold-containing adsorbent.

Description

Metal dissolving solution and gold recovery method

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

[0002] In recent years, many electrical and electronic devices, such as mobile phones, have been used and discarded. These electrical and electronic devices contain various metals, including precious metals and rare metals. Therefore, discarded electrical and electronic devices have been called "urban mines" for extracting precious metals and have attracted attention. Gold (Au), in particular, is a material used in bonding wires for connecting IC chip electrodes to lead frames, and is used in large quantities. Therefore, there is a demand 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 dissolve the precious metals in the used equipment using a metal dissolving solution. 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 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. 6,196,662 (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. 2-310,326 (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. 2002-194,450 (Patent Document 3) proposes a method for selectively adsorbing platinum group precious metals from an organic solvent solution using an adsorbent containing nicotinamide as an active ingredient.

[0005] Patent No. 6196662 JP 2-310326 JP 2002-194450

[0006] Patent Document 1 does not disclose the use of an adsorbent in recovering dissolved gold. Furthermore, Patent Document 1 adds a reducing agent, such as water or ascorbic acid, to precipitate the gold dissolved in the organic aqua regia. The addition of the 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 the 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 by itself, so it 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.

[0009] The metal dissolving solution according to the present disclosure includes 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 characteristic of generating

[0010] The gold recovery method according to 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 composition with an adsorbent to adsorb the dissolved gold onto the adsorbent to obtain a gold-containing adsorbent; and (3) separating the gold-containing adsorbent from the composition to recover the gold in the gold-containing adsorbent. This gold recovery method may further comprise: (4) reusing the metal-dissolving solution in the composition after separation of the gold-containing adsorbent by further dissolving gold in the composition.

[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.

[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-Dissolving Liquid) The metal-dissolving liquid 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] By dissolving a precious metal with the metal dissolving solution of the present disclosure, a composition containing the dissolved precious metal and the metal dissolving solution is obtained. When an adsorbent is added to this composition, the dissolved precious metal is adsorbed by the adsorbent. This allows the precious metal to be recovered. That is, the metal dissolving solution of the present disclosure can be used to recover precious metals using an adsorbent. In particular, the metal dissolving solution of the present disclosure is suitable for dissolving gold and recovering it using an adsorbent. Furthermore, this metal dissolving solution allows for further dissolution of 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 adsorption (recovery) of the dissolved precious metals using an adsorbent, without requiring additional purification or regeneration treatment. 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 that has fluidity at room temperature (15 to 35°C). In detail, an organic solvent refers to an organic compound that has fluidity at room temperature and normal pressure (e.g., 15 to 35°C, 1 atmosphere). A "hydrophilic organic solvent" refers to an organic solvent that has the property of being miscible with water or the property of being 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 precious 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. The metal-dissolving solution containing a hydrophilic organic solvent in this range has excellent solubility for precious metals.

[0023] (Chlorine Compound) The chlorine compound is one of the main components of the metal-dissolving solution of the present disclosure. As described 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). ２ ), magnesium chloride (MgCl ２ ), barium chloride (BaCl ２ ), strontium chloride (SrCl ２ ) and the like. Examples of chlorides of first transition metals include copper chloride (CuCl ２ ), iron chloride (FeCl３ ), manganese chloride (MnCl ２ Examples of the amine hydrochloride include trimethylamine hydrochloride, triethylamine hydrochloride, and triethanolamine hydrochloride. An alkali metal chloride or an amine hydrochloride is 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, based on the total mass of the 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. Precious metals dissolved in a metal-dissolving solution containing chlorine compounds within this range are 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 semiconductor substrates or the like, the chlorine compounds contained within this range do 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. When the metal-dissolving solution contains an oxidizing agent, the solubility of the precious metal is improved. Preferably, the metal-dissolving solution of the present disclosure contains an oxidizing agent other than copper halide.

[0027] The oxidizing agent contained in the metal dissolving solution is iodine molecules (I ２ ), bromine molecules (Br ２), chlorine molecules (Cl ２ Halogen molecules (X ２ , X=I, Br, Cl, etc.). ２ ) and / or chlorine molecules (Cl ２ ) is more preferred, and molecular iodine (I ２ ) is 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, relative to the entire 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) The metal dissolving solution uses halogen molecules (X ２ , X=I, Br, Cl, etc.), 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 molecule serving as the oxidizing agent is preferred.

[0030] For example, the metal dissolving solution contains iodine molecules (I ２ When the metal dissolving solution contains an iodine compound, 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 (CaI). ２ ), magnesium iodide (MgI ２), barium iodide (BaI ２ ), strontium iodide (SrI ２ In this specification, "ammonium" refers to ammonium (NH ４ ＋ ) and organic ammonium (quaternary ammonium, NR ４ ＋ , 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. 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 obtained, 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% by mass to 65% by mass, 1% by mass to less than 60% by mass, 1% by mass to 55% by mass, 5% by mass to less than 70% by mass, 5% by mass to 65% by mass, 5% by mass to less than 60% by mass, 5% by mass to 55% by mass, 10% by mass to less than 70% by mass, 10% by mass to 65% by mass, 10% by mass to less than 60% by mass, or 10% by mass to 55% by mass. A metal-dissolving liquid containing water within this range has excellent solubility for precious metals.

[0033] (Applications) 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] (Gold Recovery Method) As described above, the metal-dissolving liquid of the present disclosure has particularly excellent gold solubility. The metal-dissolving liquid of the present disclosure is suitable for use in a gold recovery method. That is, in a first embodiment, the gold recovery method of the present disclosure includes: (1) dissolving gold in the metal-dissolving liquid described above to obtain a composition containing the metal-dissolving liquid and dissolved gold; (2) contacting the obtained composition with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining 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 include (4) further dissolving gold in the composition from which the gold-containing adsorbent has been separated, thereby reusing the metal-dissolving liquid in the composition.

[0035] According to the gold recovery method of the present disclosure, gold can be easily dissolved using 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 a chloride ion (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 an 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 a bonding wire material for connecting electrodes of IC chips to lead frames can be used as materials containing gold.

[0039] Dissolving gold in a metal dissolving solution results in 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, and 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, relative to the entire 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 amount of the composition. Compositions containing water in this range have 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, and cellulose derivatives are more preferred as the adsorbent material.

[0043] In this specification, the term "cellulose derivative" is defined as a general term for compounds in which various substituents have been introduced into at least a portion of the hydroxyl groups in cellulose. A preferred cellulose derivative is a cellulose ester in which at least a portion of the hydroxyl groups in cellulose have been esterified. A cellulose ester having a total degree of substitution of 0.8 to 2.9 is 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 the NMR method 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 2 to 40 carbon atoms. 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 the acyl group of the 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 has been 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 a substituent other than an acetyl group, as long as the effects of the present disclosure are obtained. Examples of such a substituent 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, "ion exchange resin" is defined as a resin composed of a crosslinked polymer having ion exchange groups and containing counterions exchangeable with the target ions. The type of ion exchange resin may be any that is capable of ion exchange in the presence of an organic solvent and can be appropriately selected depending on the type of target ion. 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, by contacting the adsorbent with the composition, dissolved gold in the composition is primarily adsorbed onto the adsorbent. However, in rare cases, substances other than gold derived from the oxidizing agent or chlorine compound (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) onto 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 the oxidizing agent-derived substance and / or chlorine compound-derived substance onto the adsorbent before contacting the composition with the adsorbent, or a step of adding the oxidizing agent-derived substance and / or chlorine compound-derived substance 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, may be 20% to 90% by mass, may be 20% to 80% by mass, may be 20% to 70% by mass, may be 25% to less than 100% by mass, may be 25% to 90% by mass, may be 25% to 80% by mass, may be 25% to 70% by mass, may be 30% to less than 100% by mass, may be 30% to 90% by mass, may be 30% to 80% by mass, or may be 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% by mass to 10% by mass, 0.001% by mass to 5% by mass, 0.001% by mass to 1% by mass, 0.005% by mass to 10% by mass, 0.005% by mass to 5% by mass, 0.005% by mass to 1% by mass, 0.01% by mass to 10% by mass, 0.01% by mass to 5% by mass, 0.01% by mass to 1% by mass, 0.05% by mass to 10% by mass, 0.05% by mass to 5% by mass, or 0.05% by mass to 1% by mass. 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 the 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% by mass to 20% by mass, 0.001% by mass to 15% by mass, 0.001% by mass to 10% by mass, 0.01% by mass to 20% 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 15% by mass, 0.1% by mass to 10% by mass, 0.5% by mass to 20% by mass, 0.5% by mass to 15% by mass, or 0.5% by mass to 10% by mass, based on the total post-separation composition. A post-separation composition containing an oxidizing agent in this range is easy to use for dissolving precious metals and has excellent solubility.

[0061] The composition after separation of the gold-containing adsorbent (post-separation composition) is treated with halogen molecules (X ２, X=I, Br, Cl, etc.), 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% by mass to 20% by mass, 0.001% by mass to 15% by mass, 0.001% by mass to 10% by mass, 0.01% by mass to 20% 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 15% by mass, 0.1% by mass to 10% by mass, 0.5% by mass to 20% by mass, 0.5% by mass to 15% by mass, or 0.5% by mass to 10% by mass, based on the total post-separation composition. In a post-separation composition containing a halide in this range, the solubility of gold is maintained for a long period 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 this range 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 further provides the effects of the present disclosure, namely, the ability to reuse the metal solution.

[0064] That is, the gold recovery method according to the second embodiment comprises the steps of: (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; and (3) adding chloride ions (Cl) dissolved in a hydrophilic organic solvent to the first composition. － (3) adding a chlorine compound that generates a chlorine compound to the second composition to obtain a second composition containing the metal solution and 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) separating the gold-containing adsorbent from the second composition to recover the gold in the gold-containing adsorbent. This gold recovery method may further include: (6) reusing the metal solution in the second composition by further dissolving gold in the second composition from which the gold-containing adsorbent has been separated. The types and amounts of the hydrophilic organic solvent, oxidant, and chlorine compound in this embodiment can be determined by reference to the contents of the first embodiment described herein.

[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 Dissolving Solution) A metal dissolving solution containing N-methylpyrrolidone (Kanto Chemical Co., Inc., 36% by weight), iodine (I ２ A metal-dissolved solution (1) was prepared by mixing ammonium iodide (manufactured by Kanto Chemical Co., Ltd., 3% by weight), ammonium iodide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 7% by weight), water (50% by weight), and sodium chloride (manufactured by 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 (M １ ) is shown.

[0068] (Adsorption test) Adsorbent A (cellulose acetate, degree of acetyl substitution: 2.5) was added to the obtained composition (1) to adsorb the gold dissolved in the composition (1). The amount of adsorbent A added was 20 g (g / L) relative to the composition (1). After stirring for 3 hours at room temperature, adsorbent A (gold-containing adsorbent) with adsorbed gold was subjected to solid-liquid separation, and the gold concentration in the liquid phase was measured. To measure the gold concentration, an 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 measured using M １ (ppm), and the gold concentration after adsorption is M ２ The gold adsorption rate X (%) of the adsorbent was calculated using the following formula. The results are shown in Table 1 below as "gold adsorption rate (%)." X (wt%) = (M １ (ppm)-M ２ (ppm)) / M １ (ppm) x 100

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

[0070] [Examples 2-3] A dissolution test, an adsorption test, and a 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 the redissolution test are shown in Table 1 below. In addition, the water content and the dissolved gold concentration of Composition (2) and Composition (3) obtained after the dissolution test are shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M １ ) is shown.

[0071] Example 4 A dissolution test, an adsorption test, and a redissolution test 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 the redissolution test are shown in Table 1 below. The water content and the 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 (M １ ) is shown.

[0072] Comparative Example 1 N-methylpyrrolidone (Kanto Chemical Co., Ltd., 38% by weight), iodine (I ２ A metal-dissolved solution (C1) was prepared by mixing ammonium iodide (manufactured by Kanto Chemical Co., Ltd., 3% by weight), ammonium iodide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 7% by weight), and water (52% by weight). The composition of this metal-dissolved solution is shown in Table 1 below. Using this metal-dissolved 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 obtained composition (C1) are shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M 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 Examples 2-3 Composition (C1) was obtained in the same manner as in Comparative Example 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 by adding water to composition (C1) in the amounts shown in Table 1. 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 shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M １In both Comparative Examples 2 and 3, gold could not be recovered by 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, an adsorption test, and a redissolution test were carried out in the same manner as in Example 1, except that a metal-dissolved solution (5) having 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 the redissolution test are shown in Table 1 below. The water content and the dissolved gold concentration of composition (5) obtained after the dissolution test are shown in Table 1 below as "Water (in composition)" and "Initial gold concentration (M １ ) is shown.

[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 composition)" and "Initial gold concentration (M １ ) is shown.

[0076] [Example 8] Acetonitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 36% by weight), chlorine gas (Cl ２ A metal-dissolved solution (8) was prepared by mixing trimethylamine hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd., 4% by weight), trimethylamine hydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd., 10% by weight), and water (50% by weight). The composition of this metal-dissolved 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-dissolved solution (8) was used. The results obtained 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 (M １ In Table 1, "TMA hydrochloride" represents trimethylamine hydrochloride.

[0077] [Example 9] In Example 9, a liquid passing test was carried out instead of an adsorption test. The details are as follows. (Preparation of metal dissolving solution) N-methylpyrrolidone (manufactured by Kanto Chemical Co., Inc., 36% by weight), iodine (I ２ A metal-dissolved solution (9) was prepared by mixing ammonium iodide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., 3% by weight), water (50% by weight), and sodium chloride (manufactured by 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] (Liquid Flow Test) A glass column (volume 3.9 ml) was installed so that its axis was vertical, and approximately 1.7 g of adsorbent A (cellulose acetate, degree of acetyl substitution 2.5) was packed from the bottom of the column to the top to create a packed column. A liquid having the same composition as a separately prepared metal solution (9) was passed through the packed column using a metering pump at a flow rate of 3.9 ml / h for 2 hours, thereby adsorbing the oxidizing agent and chlorine compound-derived substances in the liquid onto the adsorbent A in the packed column. Thereafter, the liquid flow was stopped and the liquid in the packed column was discharged. Then, using a metering pump, composition (9) was passed through the packed column at a flow rate of 3.9 ml / h, and the liquid that flowed out of the packed column was collected as composition (9') containing the metal solution. 2.0 g of this composition (9') was collected, 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] (Re-dissolution test) Approximately 10 mg of gold wire (Φ=0.20 mm, purity 99.95%, manufactured by Nilaco Corporation) was added to the composition (9') collected in the liquid passage test and immersed overnight, and then the state of dissolution of gold in the composition (9') was visually observed. As a result, it was confirmed that most of the added gold wire was dissolved in the composition (9').

[0081]

[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 compounds, the dissolved precious metals 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] Disclosed Items Each of the following items discloses a preferred embodiment.

[0086] [Item 1] A method for producing a hydrophilic organic solvent, a chlorine compound, and an oxidizing agent, wherein the chlorine compound is dissolved in the hydrophilic organic solvent to produce chlorine ions (Cl － ). [Item 2] The metal dissolving liquid according to item 1, wherein the hydrophilic organic solvent is an organic solvent having a heteroatom. [Item 3] The metal dissolving liquid according to item 1 or 2, wherein the hydrophilic organic solvent is a polar solvent. [Item 4] The metal dissolving liquid 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] The metal dissolving liquid 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] The metal dissolving liquid 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 liquid. [Item 7] The metal dissolving liquid according to any one of items 1 to 6, further comprising water, the amount of which is less than 70% by mass with respect to the entire metal dissolving liquid. [Item 8] The metal dissolving liquid according to any one of items 1 to 6, wherein the oxidizing agent is iodine molecules (I２ ) and / or chlorine molecules (Cl ２ Item 9: The metal dissolving solution according to any one of items 1 to 7, wherein the oxidizing agent is molecular iodine (I ２ ) and further containing an iodine compound. [Item 10] The metal dissolving solution according to any one of Items 1 to 8, 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] The metal dissolving solution according to any one of Items 1 to 10, which is used in semiconductor manufacturing. [Item 12] A method for recovering gold, comprising: dissolving gold in the metal dissolving solution according to any one of Items 1 to 10 to obtain a composition containing the metal dissolving solution and dissolved gold; contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent to obtain a gold-containing adsorbent; and recovering gold in the gold-containing adsorbent by separating the gold-containing adsorbent from the composition. [Item 13] A method for recovering gold, comprising: dissolving gold in the metal-dissolving solution according to any one of Items 1 to 10 to obtain a composition containing the metal-dissolving solution and dissolved gold; contacting the composition with an adsorbent to adsorb the dissolved gold onto the adsorbent to obtain a gold-containing adsorbent; recovering the gold in the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; and reusing the metal-dissolving solution in the composition by dissolving more gold in the composition from which the gold-containing adsorbent has been separated. [Item 14] The method for recovering gold according to Item 12 or 13, wherein the adsorbent is made of at least one material selected from the group consisting of cellulose derivatives, ion exchange resins, and activated carbon. [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 to 2.9. [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 the cellulose are substituted with acetyl groups.

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

Claims

1. A method for producing a solution containing a hydrophilic organic solvent, a chlorine compound, and an oxidizing agent, wherein the chlorine compound dissolves in the hydrophilic organic solvent to produce 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. 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. 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. The metal-dissolving liquid according to claim 1, wherein the content of the chlorine compound is 0.001% by mass to 20% by mass based on the total amount of the metal-dissolving liquid.

7. The metal-dissolving solution according to claim 1, further comprising water, the amount of which is less than 70 mass % of the total 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. 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. A method for recovering gold, comprising: dissolving gold in the metal dissolving liquid according to claim 1 to obtain a composition containing the metal dissolving liquid and dissolved gold; bringing the composition into contact with an adsorbent to adsorb the dissolved gold onto the adsorbent, thereby obtaining a gold-containing adsorbent; and separating the gold-containing adsorbent from the composition to recover the gold in the gold-containing adsorbent.

13. A method for recovering gold, comprising: obtaining a composition containing the metal dissolving liquid and dissolved gold by dissolving gold in the metal dissolving liquid according to claim 1; obtaining a gold-containing adsorbent by bringing the composition into contact with an adsorbent and allowing the dissolved gold to be adsorbed onto the adsorbent; recovering the gold in the gold-containing adsorbent by separating the gold-containing adsorbent from the composition; and reusing the metal dissolving liquid in the composition by dissolving more gold in the composition from which the gold-containing adsorbent has been separated.

14. A method for recovering gold as described in 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. 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. 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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