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

Abstract

A method for producing a gold sulfite by generating fulminating gold as an intermediate substance, and an object thereof is to provide a highly safe method. 【Solution means】A production method including the steps of acid-dissolving a gold raw material to prepare a chloroauric acid solution, adding aqueous ammonia to the chloroauric acid solution to precipitate fulminating gold, washing the fulminating gold with pure water and an alkaline aqueous solution, and adding a metal sulfite to the washed fulminating gold to prepare a gold sulfite solution solves the problem.

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 a raw material for producing a gold compound, and several manufacturing methods thereof have been proposed.

[0003] Patent Document 1 discloses that, as a conventional technique, ammonia water is added to a chloroauric acid solution to precipitate and generate gold fulminate, and then sodium thiosulfate 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 ammonia water 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 provides a method for producing gold sulfite by generating gold fulminate as an intermediate substance, with the objective of providing a highly safe method.

Means for Solving the Problems

[0007] The inventors of the present invention conducted repeated studies to solve the above problems and focused on the modification treatment of gold fulminate generated as a precipitate. Usually, gold fulminate is washed with pure water and then introduced into the next process. However, it has been found that by washing gold fulminate with an alkaline aqueous solution in addition to washing with pure water, the gold fulminate is modified and the risk of explosion becomes extremely small. Then, the inventors intensively studied the modification treatment conditions of the generated gold fulminate and completed the present invention.

[0008] The present invention provides a method for producing gold sulfite, which includes steps of acid-dissolving a gold raw material to prepare a gold acid solution, adding aqueous ammonia to the gold acid solution to precipitate gold fulminate, washing the gold fulminate with pure water and an alkaline aqueous solution, and adding a metal sulfite to the washed gold fulminate to prepare a gold sulfite solution.

[0009] The gold raw material may be either recycled gold or virgin gold, or a mixture thereof. Another form 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 content of particles with an average particle diameter of 1 μm or more present in 1 mL of the solution is 800 or less.

Effects of the Invention

[0010] In the present invention, since the safety of gold fulminate generated as an intermediate substance can be enhanced, a highly safe and simple method for producing gold sulfite can be provided.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents, and can be variously modified and implemented within the scope of the gist.

[0012] One embodiment of the present invention is a method for producing chloroauric acid salt, which includes the steps of acid-dissolving a gold raw material to prepare a chloroauric acid solution, adding aqueous ammonia to the chloroauric acid solution to precipitate aurum fulminans, washing the aurum fulminans with pure water and an alkaline aqueous solution, and adding a metal sulfite to the washed aurum fulminans to prepare a chloroauric acid salt solution. This embodiment includes the above steps, and may also include steps other than the above steps.

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

[0014] This embodiment is a manufacturing method for obtaining a chloroauric acid salt solution by generating aurum fulminans as an intermediate substance, and in order to enhance its safety, the aurum fulminans as the intermediate substance is washed to modify the aurum fulminans. As a result of the study by the present inventors, it was found that when washing aurum fulminans, in addition to pure water, washing with an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution modifies the aurum fulminans, and safe operation can be carried out in subsequent operations.

[0015] The pH of the prepared chloroauric acid solution is usually 5 or less, may be 3 or less, and may be 1 or less. Since it is an aqueous solution of a strong acid, the lower limit is usually not defined, 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 auric ammonium chloride, aqueous ammonia is added to the prepared chloroauric acid solution. The amount of aqueous ammonia added is not particularly limited, and an amount sufficient for the recycled gold, virgin gold or a mixture thereof dissolved in aqua regia to precipitate as auric ammonium chloride may be added. The pH of the solution at this time is preferably 8 or more, may be 9 or more, and may be 11 or less.

[0017] The precipitated auric ammonium chloride is usually taken out by filtration and washed. Washing is usually performed with pure water. At this time, auric ammonium chloride is a substance dangerous for explosion and must always be kept in a wet state. In this embodiment, in addition to washing with pure water, by washing with an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium carbonate solution, or an aqueous potassium carbonate solution, the auric ammonium chloride is modified, and auric ammonium chloride with low explosiveness can be obtained.

[0018] The concentration of the alkaline aqueous solution used for the modification of auric ammonium chloride can be arbitrarily determined. Also, the number of washing times can be arbitrarily determined as needed. By washing once with ion-exchanged water and once with an alkaline aqueous solution sufficiently stable auric ammonium chloride can be obtained. However, in order to make the modification effect more reliable, it is preferable to wash twice each with ion-exchanged water and an alkaline aqueous solution. Washing 3 times or more is also possible, but as the number of times increases, the working time becomes longer and the amount of waste liquid generated also increases. Therefore, the total number of washing times with ion-exchanged water and an alkaline aqueous solution is preferably 6 or less. Also, the washing order of auric ammonium chloride may be arbitrarily set. Since components derived from aqua regia may remain in auric ammonium chloride, it is preferable to first wash the components with pure water and then with an alkaline aqueous solution. Even if the alkaline aqueous solution remains in the auric ammonium chloride, it does not affect the next step. The quality of the deionized water used for washing is not particularly limited, but it is preferable to use deionized water with an electrical conductivity of 2 μS / cm or less, more preferably deionized water with an electrical conductivity of 1 μS / cm.

[0019] In this 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, the mixing of unnecessary alkali metal ions into the target substance can be prevented. 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, 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 is not clear, 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 the 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. Thereby, 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. In addition, 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 the gold sulfite solution, a metal salt of sulfite such as sodium sulfite or potassium sulfite is added to the taken-out colloidal gold 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 colloidal gold may be added to pure water, and then a metal salt of sulfite such as sodium sulfite may be added, or the colloidal gold 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 colloidal gold is modified by washing in the washing step, and the Cl / Au ratio in the colloidal gold is reduced. In the gold sulfite solution prepared from the modified colloidal gold, the chloride ion concentration is reduced to less than 3 g / L, preferably less than 1 g / L. If the colloidal gold 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 goes without saying 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 left standing at room temperature for 1 hour to precipitate colloidal gold particles. Next, the precipitated auric chloride particles were subjected to vacuum filtration by suction on a funnel to obtain auric chloride particles containing moisture. While suctioning, approximately 100 mL of ion-exchanged water was passed through to wash the auric chloride. This operation was repeated twice. Subsequently, 50 mL of a 50 g / L sodium hydroxide aqueous solution was passed through to wash the auric chloride. This operation was repeated twice. The obtained auric chloride was analyzed with an energy-dispersive X-ray analyzer to measure the atomic number ratio of chlorine to gold (Cl / Au) in the auric chloride.

[0025] The obtained auric chloride was mixed with approximately 150 mL of ion-exchanged water, heated to 65 °C or higher, 25 g of sodium sulfite was added while stirring, and after holding for about 3 hours, it was cooled by standing for 1 hour to obtain a sodium gold sulfite solution. The stability and safety of auric chloride during heating were simply evaluated. Specifically, when heating the ion-exchanged water mixed with auric chloride, a dried portion was generated at the upper part of the container, and the auric chloride adhering to this dried portion was crushed with a medicine spoon. At this time, if a cracking sound was confirmed, it was judged that the auric chloride was unstable. On the other hand, if no cracking sound was confirmed, it was judged that the auric chloride was stable and safe. In this example, the confirmation of this cracking sound was repeated 5 times, and if no cracking sound was confirmed in all cases, it was considered qualified (〇). If the cracking sound was confirmed even once, it was considered unqualified (×). Next, the amount of particles (1 μm or more) in 1 mL of the sodium gold sulfite solution was measured with a particle counter measuring instrument. Also, the chloride ion concentration of the sodium gold sulfite solution was 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 at a weight ratio of 1:1.

[0028] <Comparative Example 1> In the cleaning process of the lightning arrester, the experiment was conducted in the same manner as in Example 1, except that the solution was passed through four times for cleaning only with ion-exchanged water without using an aqueous sodium hydroxide solution (alkaline aqueous solution).

[0029]

Table 1

[0030] The invention according to the present disclosure can contribute to SGDs 12: Responsible Consumption and Production.

Claims

1. A step of dissolving a gold raw material in an acid to prepare a gold acid solution; adding ammonia water to the gold acid solution to precipitate gold; washing the irradiated metal with pure water and one or more alkaline aqueous solutions 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; and adding a metal sulfite to the washed gold sulphite to prepare a sodium gold sulfite solution or potassium gold sulfite solution.

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

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

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

5. A sodium gold sulfite solution or potassium gold sulfite solution having a chloride ion concentration of less than 1 g / L and having 800 or less particles of 1 μm or more present per mL of the solution.

Images