Method for producing sodium gold sulfite or potassium gold sulfite and solution of sodium gold sulfite or potassium gold sulfite

Abstract

The objective is to provide a highly safe method for producing gold sulfite salts by generating fulminate as an intermediate substance. [Solution] The problem is solved by a manufacturing method that includes the steps of: dissolving a gold raw material in acid to prepare a gold acid solution; adding ammonia water to the gold acid solution to precipitate gold fulminate; washing the gold fulminate with pure water and an alkaline aqueous solution; and adding a metallic sulfite to the washed gold fulminate to prepare a gold sulfite solution.

Description

Technical Field

[0001] The present invention relates to a method for producing aurothiosulfate and an aurothiosulfate solution.

Background Art

[0002] Aurothiosulfate is used as a raw material for a gold plating solution and as a raw material for producing gold compounds, and several manufacturing methods thereof have been proposed.

[0003] Patent Document 1 discloses that, as a conventional technique, an aqueous ammonia solution is added to a chloroauric acid solution to precipitate and generate gold fulminate, and then sodium sulfite is added to the filtered and washed gold fulminate to produce an aurothiosulfate solution. However, it is also disclosed that gold fulminate is not only an extremely unstable substance but also has a high risk of explosion and is not preferable as an industrial manufacturing method.

[0004] Therefore, Patent Document 1 proposes a method that does not generate gold fulminate as an intermediate substance in order to safely synthesize aurothiosulfate.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method for producing aurothiosulfate proposed in Patent Document 1, which does not generate gold fulminate as an intermediate substance, although the safety is considered to be high, the process becomes complicated and the manufacturing cost also increases. Therefore, although the method of adding an aqueous ammonia solution to generate gold fulminate as an intermediate substance is simple, it is currently impossible to safely handle gold fulminate and adopt a simple manufacturing method. The present invention aims to solve the above problems and to provide a method for producing gold sulfite salt by generating fulminate as an intermediate substance, with a high degree of safety. [Means for solving the problem]

[0007] The inventors of this invention conducted extensive research to solve the above problems and focused on the modification treatment of fulminate, which is formed as a precipitate. Normally, fulminate is washed with pure water before being added to the next process, but they found that by washing it with an alkaline aqueous solution in addition to washing it with pure water, the fulminate is modified, and the risk of explosion is greatly reduced. They then diligently investigated the conditions for modifying the generated fulminate and completed the present invention.

[0008] The present invention is a method for producing gold sulfite, comprising the steps of: dissolving a gold raw material in acid to prepare a gold acid solution; adding ammonia water to the gold acid solution to precipitate gold fulminate; washing the gold fulminate with pure water and an alkaline aqueous solution; and adding a metallic sulfite to the washed gold fulminate to prepare a gold sulfite solution.

[0009] The aforementioned gold raw material may be recycled gold or virgin gold, or a mixture thereof. Another embodiment of the present invention is a gold sulfite solution in which the chloride ion concentration in the solution is less than 1 g / L, and the amount of particles with an average particle size of 1 μm or more present in 1 mL of the solution is 800 or less. [Effects of the Invention]

[0010] In this invention, the safety of the gold fulminate produced as an intermediate substance can be enhanced, thus providing a safe and simple method for producing gold sulfite. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below, but the description of the constituent elements described below is just one example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents, and can be implemented in various ways within the scope of its gist.

[0012] One embodiment of the present invention is a method for producing a gold sulfite, comprising the steps of: dissolving a gold raw material in acid to prepare a gold acid solution; adding ammonia water to the gold acid solution to precipitate gold fulminate; washing the gold fulminate with pure water and an alkaline aqueous solution; and adding a metallic sulfite to the washed gold fulminate to prepare a gold sulfite solution. This embodiment includes the steps described above, but may also include steps other than those described above.

[0013] In the step of preparing the arugula solution, the gold raw material is dissolved in acid. The gold raw material is not particularly limited and may be virgin gold or recycled gold. Alternatively, virgin gold and recycled gold may be mixed in any ratio. The mixing ratio of recycled gold to virgin gold can be set arbitrarily between 0 and 100%. For example, the ratio of virgin gold to recycled gold may be 1:99 to 50:50, or within the range of 1:99 to 40:60, or within the range of 1:99 to 20:80. Furthermore, aqua regia is generally used as the acid to dissolve the gold raw material, and a gold acid solution is prepared by dissolving the gold raw material in aqua regia.

[0014] This embodiment is a manufacturing method for obtaining a gold sulfite salt solution by generating fulminate as an intermediate substance, and in order to enhance safety, the fulminate, which is an intermediate substance, is modified by washing it. The inventors of this invention investigated and found that when washing raimold with an alkaline aqueous solution such as sodium hydroxide solution or potassium hydroxide solution in addition to pure water, the raimold is modified, allowing for safer handling in subsequent operations.

[0015] The pH of the prepared auric acid solution is usually 5 or less, but may be 3 or less, or even 1 or less. Since it is an aqueous solution of a strong acid, a lower limit is usually not set, but the pH may be adjusted to 2 or more and 3 or less using a sodium hydroxide solution or the like.

[0016] In the step of precipitating the gold fulminate, aqueous ammonia is added to the prepared gold acid solution. The amount of aqueous ammonia added is not particularly limited; it should be sufficient to allow the recycled gold, virgin gold, or mixture thereof dissolved in aqua regia to precipitate as gold fulminate. The pH of the solution at this stage is preferably 8 or higher, may be 9 or higher, or 11 or lower.

[0017] The precipitated fulminate is usually removed by filtration and washed. Washing is usually done with pure water. During this process, it is important to remember that fulminate is an explosive substance and must always be kept moist. In this embodiment, in addition to washing with pure water, the fulminate is modified by washing with alkaline aqueous solutions such as sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, or potassium carbonate solution, thereby obtaining fulminate with reduced explosiveness.

[0018] The concentration of the alkaline aqueous solution used to modify the thunder metal can be determined arbitrarily. The number of washes can also be determined arbitrarily as needed. One wash with deionized water, followed by a wash with the alkaline aqueous solution. A single wash is sufficient to obtain a sufficiently stable raikin, but to ensure a more reliable modification effect, it is preferable to wash twice each with deionized water and an alkaline aqueous solution. Washing three or more times is also possible, but since a higher number of washes increases the working time and the amount of waste liquid generated, it is preferable to limit the total number of washes with deionized water and alkaline aqueous solution to six or less. The washing order of the raikin can be set arbitrarily. Since components derived from aqua regia may remain in the raikin, it is preferable to wash these components first with pure water before washing with an alkaline aqueous solution. Even if alkaline aqueous solution remains in the raikin, it will not affect the next process. The quality of the deionized water used for washing is not particularly limited, but it is preferable to use deionized water with an electric conductivity of 2 μS / cm or less, and more preferably deionized water with an electric conductivity of 1 μS / cm.

[0019] In the present embodiment, the alkaline aqueous solution used for washing the fulminating gold is not particularly limited, but it is preferable to use one or more selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium carbonate solution, and an aqueous potassium carbonate solution. It is preferable to select an alkaline aqueous solution that matches the type of salt of the target gold sulfite. For example, when it is desired to obtain sodium gold sulfite as the gold sulfite, it is preferable to select an aqueous sodium hydroxide solution or an aqueous sodium carbonate solution as the alkaline aqueous solution for washing. Thereby, it is possible to prevent the mixing of unnecessary alkali metal ions into the target substance. The alkali concentration of the alkaline aqueous solution is not particularly limited either, but it is usually in the range of 0.1 g / L to 500 g / L, and preferably in the range of 1 g / L to 100 g / L.

[0020] The fulminating gold washed with the alkaline aqueous solution has a reduced risk of explosion. The detailed mechanism of this has not been clarified, but it can be speculated as follows. Generally, the chemical composition of fulminating gold is indefinite, but it is a compound containing chlorine, nitrogen, and oxygen in addition to gold. Due to containing unstable chemical bonds, fulminating gold itself is also unstable and is likely to explode upon impact during drying. When washed with an alkaline aqueous solution, it is considered that the alkaline aqueous solution in contact with the fulminating gold removes chlorine, which is a factor that destabilizes the fulminating gold. Thus, stabilized fulminating gold can be obtained. Usually, when the fulminating gold is washed with deionized water, the atomic ratio of chlorine to gold (Cl / Au) in the fulminating gold becomes 0.05 to 0.5. On the other hand, when washed with an alkaline aqueous solution, it becomes less than 0.05. In order to obtain more stable and safe fulminating gold, it is preferable that Cl / Au is 0.02 or less. Incidentally, the components of the fulminating gold can be analyzed with an energy dispersive X-ray analyzer or the like. Also, the stability and safety of the fulminating gold can be confirmed by the method described in the examples.

[0021] In the step of preparing a gold sulfite solution, a metal salt of sulfite such as sodium sulfite or potassium sulfite is added to the taken-out gold fulminate to prepare a gold sulfite solution. The gold sulfite in the gold sulfite solution is typically sodium gold sulfite or potassium gold sulfite, but is not limited thereto. The gold fulminate may be added to pure water, and then a metal salt of sulfite such as sodium sulfite may be added, or the gold fulminate may be added to a sulfite solution.

[0022] Generally, the gold sulfite solution contains a chloride ion concentration derived from aqua regia as an impurity. As described above, the gold fulminate is modified by washing in the washing step, and the Cl / Au ratio in the gold fulminate is reduced. In the gold sulfite solution prepared from the modified gold fulminate, the chloride ion concentration is reduced to less than 3 g / L, preferably less than 1 g / L. If the gold fulminate is not washed in the washing step, the chloride ion concentration of the gold sulfite solution will be 3 g / L or more. In addition, the gold sulfite solution has a reduced content of particles having an average particle diameter of 1 μm or more, preferably 800 or less per 1 mL, and more preferably 600 or less. The measurement of the amount of particles in the gold sulfite solution can be performed by a particle counter measuring instrument.

Example

[0023] Hereinafter, the present invention will be described in more detail using examples, but it is needless to say that the scope of the present invention is not limited by the description of the examples.

[0024] <Example 1> 10 g of recycled gold (4N manufactured by Matsuda Sangyo Co., Ltd.) was dissolved in 40 mL of aqua regia to obtain a chloroauric acid solution with a pH of less than 1. This chloroauric acid solution was cooled to room temperature (25 °C), 35 mL of aqueous ammonia was added, and the mixture was stirred for 45 minutes and then allowed to stand at room temperature for 1 hour to precipitate gold fulminate particles. Next, the precipitated gold particles were vacuum filtered by suction over a funnel to obtain gold particles containing water. While still under suction, approximately 100 ml of deionized water was passed through to wash the gold particles. This process was repeated twice. Subsequently, 50 ml of a 50 g / L sodium hydroxide solution was passed through to wash the gold particles again. This process was repeated twice. The obtained gold particles were analyzed using an energy-dispersive X-ray analyzer to measure the atomic ratio of chlorine to gold (Cl / Au) in the gold particles.

[0025] The obtained gold thunder was mixed with approximately 150 ml of deionized water, heated to over 65°C, and 25 g of sodium sulfite was added while stirring. After holding for approximately 3 hours, it was allowed to stand for 1 hour to cool and obtain a sodium gold sulfite solution. The stability and safety of the raikin were simply evaluated during heating. Specifically, when ion-exchanged water mixed with raikin was heated, a dry area formed at the top of the container. The raikin adhering to this dry area was crushed with a spatula. If a popping sound was heard, the raikin was judged to be unstable. On the other hand, if no popping sound was heard, the raikin was judged to be stable and safe. In this embodiment, this popping sound check was repeated five times, and if no popping sound was heard in any of the tests, it was judged to pass (○). If a popping sound was heard even once, it was judged to fail (×). Next, the amount of particles (1 μm or larger) in 1 mL of sodium gold sulfite solution was measured using a particle counter. The chloride ion concentration of the sodium gold sulfite solution was also measured. These results are shown in Table 1.

[0026] <Example 2> A sodium gold sulfite solution was obtained in the same manner as in Example 1, except that the gold raw material was changed to virgin gold and the concentration of the sodium hydroxide aqueous solution used for washing was changed to 10 g / L.

[0027] <Example 3> A sodium gold sulfite solution was obtained in the same manner as in Example 1, except that the gold raw material was changed to a mixture of recycled gold and virgin gold in a 1:1 weight ratio.

[0028] <Comparative Example 1> The experiment was conducted in the same manner as in Example 1, except that in the washing process of the thunder metal, sodium hydroxide aqueous solution (alkaline aqueous solution) was not used, and the metal was washed four times using only deionized water.

[0029] [Table 1]

[0030] The invention described herein can contribute to SGD 12: Responsible Consumption and Production.

Claims

1. A step of preparing a gold acid solution by dissolving a gold raw material in acid, The step of adding ammonia water to the auric acid solution to precipitate the fulminate, A step of washing the thunder metal with pure water and an alkaline aqueous solution, and A method for producing a gold sulfite, comprising the step of adding a metallic sulfite to the washed gold thresher to prepare a gold sulfite solution.

2. The manufacturing method according to claim 1, wherein the gold raw material used in the step of preparing the arugula solution is recycled gold.

3. The manufacturing method according to claim 1, wherein the gold raw material used in the step of preparing the arugula solution is a mixture of recycled gold and virgin gold.

4. The manufacturing method according to claim 1, wherein the gold raw material used in the step of preparing the auguric acid solution is virgin gold.

5. A gold sulfite solution having a chloride ion concentration of less than 1 g / L and containing 800 or fewer particles of 1 μm or larger per 1 mL of solution.

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