Method for recovering gold or platinum

Abstract

To provide a method for recovering gold or platinum that enables recovery of gold or platinum at high yield and efficiency, and to provide an agent for recovering gold or platinum.SOLUTION: A method for recovering gold or platinum comprises a step of mixing an aqueous solution in which at least one of gold or platinum is dissolved with a cationic surfactant and an aromatic compound, and a step of separating and recovering a precipitate containing at least one of gold or platinum thus produced.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for recovering gold or platinum. [Background technology]

[0002] Precious metals such as gold and platinum are used for a variety of purposes, including crafts, jewelry, semiconductor components in electrical appliances, and catalyst raw materials. However, due to their scarcity, it is desirable to recover and reuse (recycle) them.

[0003] Techniques for recovering precious metal elements such as gold or platinum from water have been known for some time. For example, Patent Document 1 and Non-Patent Document 1 propose a method for recovering a precipitate containing precious metal ions by dissolving a compound containing a precious metal anion complex in water and then mixing it with a cationic surfactant. However, this method produces a low yield of precipitate containing precious metal ions, making it insufficient for practical use in terms of cost-effectiveness. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 61-243091

[0005] [Non-Patent Document 1] Yamaguchi University Instrumental Analysis Center Report 7 15-21, 1999 "Separation of Platinum Group Elements Using Surfactant Extraction" Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a method for recovering gold or platinum, which is capable of recovering gold or platinum in high yield and with high efficiency, and to provide a collector for recovering gold or platinum. [Means for solving the problem]

[0007] The present inventors have investigated methods for recovering gold and platinum in high yields and have found that gold and platinum can be recovered in high yield and with high efficiency by mixing an aqueous solution containing an anionic complex of a noble metal such as gold or platinum with a cationic surfactant and an aromatic compound, thereby completing the present invention.

[0008] That is, the present invention (1) is a method for recovering gold or platinum, which comprises a mixing step of mixing an aqueous solution in which at least one of gold or platinum has been dissolved with a cationic surfactant and an aromatic compound, and a separation and recovery step of separating and recovering the resulting precipitate containing at least one of gold or platinum.

[0009] The present invention (2) is a method for recovering gold or platinum according to the present invention (1), wherein the cationic surfactant and aromatic compound to be mixed in the mixing step are a mixture of both.

[0010] The present invention (3) is the method for recovering gold or platinum according to the present invention (1) or (2), wherein the cationic surfactant is dodecyltrimethylammonium bromide.

[0011] The present invention (4) is a method for recovering gold or platinum according to any one of the present inventions (1) to (3), wherein the cationic surfactant is added at a concentration of 10 to 100 mmol / L.

[0012] The present invention (5) is a method for recovering gold or platinum according to any one of the present inventions (1) to (4), wherein the aromatic compound is anthracene.

[0013] The present invention (6) is a method for recovering gold or platinum according to any one of the present inventions (1) to (5), wherein the concentration of the aromatic compound added is 25 to 150 μmol / L.

[0014] The present invention (7) is a collector for recovering gold or platinum, which contains a mixture of a cationic surfactant and an aromatic compound. [Effects of the Invention]

[0015] According to the present invention, gold or platinum can be recovered from an aqueous solution containing dissolved gold or platinum in high yield and high efficiency without consuming a large amount of energy to distill off water. DETAILED DESCRIPTION OF THE INVENTION

[0016] The recovery method of the present invention is characterized by comprising a mixing step of mixing an aqueous solution containing at least one of gold and platinum dissolved therein with a cationic surfactant and an aromatic compound, and a separation and recovery step of separating and recovering the resulting precipitate containing at least one of gold and platinum. In the recovery method of the present invention, it is presumed that the aromatic compound further enhances the anionization of the anionic complex of gold or platinum in the aqueous solution, which in turn leads to a stronger electrical attraction between the cationic surfactant and the anionic complex of gold or platinum in the aqueous solution, facilitating the formation of a gold or platinum precipitate and enabling the recovery of gold or platinum in a high yield.

[0017] <Mixing step of cationic surfactant and aromatic compound> The gold or platinum used in the recovery method of the present invention is not particularly limited as long as it is a gold compound or platinum compound that dissolves in water, but examples thereof include AuCl3 (gold chloride (III)), PtCl4 (platinum chloride (IV)), H[AuCl4] - Examples include gold(III) tetrachloride ion, H2[PtCl6] (chloroplatinic(IV) acid), etc. These water-soluble compounds change into anionic complexes of gold or platinum when dissolved in water. The aqueous solution may contain only gold or platinum, or both gold and platinum.

[0018] The cationic surfactant used in the recovery method of the present invention is not particularly limited, and examples thereof include tertiary amines and quaternary ammonium salts. Examples of quaternary ammonium salts include monoalkyl, monoalkyl ether, dialkyl, dialkyl ester, and benzalkonium types. Examples include hexadecyltrimethylammonium chloride (HTAC) and dodecyltrimethylammonium bromide (DTAB). However, dodecyltrimethylammonium bromide (DTAB) is preferred because it allows for the recovery of a larger amount of anionic complexes of gold and platinum in water.

[0019] The concentration of the cationic surfactant added is preferably 10 to 100 mmol / L, more preferably 10 to 75 mmol / L, and even more preferably 10 to 40 mmol / L. If the concentration is less than 10 mmol / L, a precipitate cannot be obtained efficiently, while if the concentration is more than 100 mmol / L, the entire solution becomes suspended and foaming increases, which tends to make recovery time longer. In this specification, the "concentration of the cationic surfactant added" refers to the concentration of the cationic surfactant in the aqueous solution after mixing in the mixing step in which an aqueous solution in which at least one of gold and platinum is dissolved is mixed with the cationic surfactant and the aromatic compound.

[0020] The aromatic compound used in the recovery method of the present invention is not particularly limited as long as it has an aromatic ring. Examples include benzene, naphthalene, anthracene, phenanthrene, and naphthacene, but anthracene, which has many π bonds (electron pairs) in the molecule, is preferred.

[0021] The concentration of the aromatic compound added is preferably 25 to 150 μmol / L, more preferably 25 to 100 μmol / L, and even more preferably 25 to 75 μmol / L. If the concentration is less than 25 μmol / L, a precipitate cannot be obtained efficiently, and if the concentration is more than 150 μmol / L, dissolution in methanol tends to become difficult. In this specification, the "concentration of the aromatic compound added" refers to the concentration of the aromatic compound in the aqueous solution after mixing in the step of mixing an aqueous solution in which at least one of gold and platinum is dissolved with a cationic surfactant and an aromatic compound.

[0022] The molar ratio of the cationic surfactant to the aromatic compound is not particularly limited, but is preferably 1:2.5×10 -3 ~7.5×10 -3 is preferred, and 1:2.5×10 -3 ~5.0×10 -3 is more preferred.

[0023] In the mixing step of mixing an aqueous solution of at least one of gold and platinum with a cationic surfactant and an aromatic compound, the aqueous solution of at least one of gold and platinum, the cationic surfactant, and the aromatic compound may be added and mixed separately, or a mixture of a cationic surfactant and an aromatic compound prepared in advance may be mixed. -3 It is preferable to use a mixture of a cationic surfactant and an aromatic compound prepared in advance, in order to uniformly disperse the aromatic compound, which is an additive with a small order, and to recover gold or platinum efficiently without waste.

[0024] When adding a cationic surfactant and an aromatic compound separately to an aqueous solution containing at least one of gold and platinum, the aromatic compound is insoluble in water, so the aromatic compound is mixed using a solution prepared by dissolving it in a water-soluble organic solvent beforehand. Also, the cationic surfactant (e.g., DTAB) has low solubility in water, so the aromatic compound is mixed using a solution prepared by dissolving it in a water-soluble organic solvent beforehand.

[0025] When a mixture of a cationic surfactant and an aromatic compound is added to an aqueous solution containing at least one of gold and platinum, the mixture is first dissolved in a good solvent for both metals, such as an organic solvent such as methanol, ethanol, or acetone, and mixed uniformly. If necessary, the solvent is then removed by distillation to obtain a mixture of the two metals. Because the cationic surfactant and the aromatic compound interact with each other, they can be uniformly dispersed or dissolved in an aqueous solution containing at least one of gold and platinum, even in the absence of an organic solvent.

[0026] <Separation and recovery process> The method for separating and recovering the resulting gold- or platinum-containing precipitate is not particularly limited, and examples include a method in which a suspension of the gold- or platinum-containing precipitate is subjected to decantation, filtration, or centrifugation to recover the precipitate.

[0027] From the recovered precipitate containing gold or platinum, only gold or platinum can be separated and purified by a conventionally known method such as ion exchange or electrolytic deposition.

[0028] The recovery method of the present invention allows gold and platinum to be recovered in high yields without distilling off solvents such as water, and is therefore more cost-effective than conventional recovery techniques, and is expected to be put to practical use in industry. Specifically, in the semiconductor industry, it is expected that the recovered gold and platinum will be reused in semiconductor components in electrical products.

[0029] The collector for recovering gold or platinum of the present invention is characterized by containing a mixture of a cationic surfactant and an aromatic compound. By adding the collector to an aqueous solution in which at least one of gold or platinum has been dissolved, gold or platinum can be recovered in high yield. Specific examples of the cationic surfactant and aromatic compound and their contents are as described above. [Example]

[0030] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0031] Example 1 Solution (A) was prepared by adding dodecyltrimethylammonium bromide (DTAB) (Wako Pure Chemical Industries, Ltd.) to 50 mL of ultra-dehydrated methanol (Wako Pure Chemical Industries, Ltd.) to a concentration of 10 mM, and solution (B) was prepared by adding anthracene (Wako Pure Chemical Industries, Ltd.) to methanol to a concentration of 50 μM. Next, 4 mL of the prepared solution (A) and 4 mL of solution (B) were mixed uniformly in a glass centrifuge tube with a lid and a working volume of 15 mL. After that, industrial nitrogen gas was blown into the centrifuge tube in a fume hood to evaporate the methanol inside the tube, producing a mixture of DTAB and anthracene uniformly coated on the inner wall of the tube.

[0032] Next, to prepare an aqueous solution containing gold and platinum, AuCl3 (gold(III) chloride) and PtCl4 (platinum(IV) chloride) (both manufactured by Wako Pure Chemical Industries, Ltd.) were dissolved in distilled water to a concentration of 3 mM each to prepare solution (C). Next, 10 mL of solution (C) was added to the centrifuge tube with the collector on the inner wall described above, and the tube was stirred at 1600 rpm for 1 minute using a vortex mixer (VORTEX-GENIE 2 Mixer, manufactured by Scientific Industries, Inc.). The tube was then centrifuged at 3000 rpm for 5 minutes using a centrifuge (D91721-A000, manufactured by Kubota Manufacturing Co., Ltd.) to separate the precipitate from the supernatant. A portion of the resulting supernatant was collected as a sample for quantifying the gold and platinum in water.

[0033] The collected sample water was subjected to a high-frequency inductively coupled plasma (ICP) optical emission spectrometer (Optima 5300, PerkinElmer Japan Co., Ltd.) to quantify the concentrations of gold and platinum remaining in the supernatant. The gold and platinum contents in the precipitate were calculated by subtracting the total amounts of gold and platinum contained in the supernatant, calculated using the concentrations of gold and platinum remaining in the supernatant, from the total amounts of gold and platinum contained in solution (C) in the centrifuge tube.

[0034] Examples 2 and 3 An experiment was carried out in the same manner as in Example 1, except that the concentration of DTAB added to the solution (A) prepared in Example 1 was changed to the amount shown in Table 1.

[0035] Example 4 The experiment was carried out in the same manner as in Example 1, except that the concentration of anthracene added to the solution (A) prepared in Example 1 was changed to the amount shown in Table 1.

[0036] Comparative Example 1 The experiment was carried out in the same manner as in Example 1, except that DTAB (0 mM) was not added to the solution (A) prepared in Example 1.

[0037] Comparative Example 2 The same experiment as in Example 1 was carried out, except that no anthracene (0 μM) was added to the solution (B) prepared in Example 1.

[0038] [Table 1]

[0039] [Table 2]

[0040] As shown in Comparative Example 1, when anthracene alone was used, neither gold nor platinum could be recovered. As shown in Comparative Example 2, when DTAB alone was used, both gold and platinum could be recovered, but the amounts recovered were small. On the other hand, when anthracene and DTAB were used in combination, as shown in Examples 1 to 4, both gold and platinum could be recovered more efficiently than in Comparative Example 2, in which DTAB was used alone. [Industrial Applicability]

[0041] The recovery method of the present invention allows gold and platinum to be recovered in high yields, which is more cost-effective than conventional recovery techniques and is expected to be put to practical use in industry. Specifically, in the semiconductor industry, it is expected that the recovered gold and platinum will be reused in semiconductor components in electrical products.

Claims

1. a mixing step of mixing an aqueous solution in which at least one of gold and platinum is dissolved with a cationic surfactant and an aromatic compound; A separation and recovery step of separating and recovering the precipitate containing at least one of gold and platinum produced. A method for recovering gold or platinum, comprising:

2. 2. The method for recovering gold or platinum according to claim 1, wherein the cationic surfactant and aromatic compound to be mixed in the mixing step are a mixture of both.

3. 3. The method for recovering gold or platinum according to claim 1, wherein the cationic surfactant is dodecyltrimethylammonium bromide.

4. 3. The method for recovering gold or platinum according to claim 1, wherein the concentration of the cationic surfactant added is 10 to 100 mmol / L.

5. 3. The method for recovering gold and platinum according to claim 1, wherein the aromatic compound is anthracene.

6. 3. The method for recovering gold and platinum according to claim 1, wherein the concentration of the aromatic compound added is 25 to 150 μmol / L.

7. A collector for recovering gold or platinum, comprising a mixture of a cationic surfactant and an aromatic compound.

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