Production method for gold sulfite and gold sulfite solution

Abstract

The present invention addresses the problem of providing a highly safe method for producing a gold sulfite via the production of fulminating gold as an intermediate. According to the present invention, a production method includes a step for dissolving a gold starting material in acid to obtain a gold acid solution, a step for adding ammonia water to the gold acid solution to precipitate fulminating gold, a step for washing the fulminating gold with pure water and an alkaline aqueous solution, and a step for adding a metal sulfite to the washed fulminating gold to obtain a gold sulfite solution.

Description

Method for producing gold sulfite and gold sulfite solution

[0001] The present invention relates to a method for producing gold sulfite and a gold sulfite solution.

[0002] Gold sulfite is used as a raw material for gold plating solutions and as a raw material for producing gold compounds, and several production methods have been proposed.

[0003] Patent Document 1 discloses, as a conventional technique, adding aqueous ammonia to a chloroauric acid solution to precipitate and generate gold fulminate, and then adding sodium sulfite to the filtered and washed gold fulminate to produce a gold sulfite 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 production method.

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

[0005] JP-A-3-146419

[0006] In the method for producing gold sulfite 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 production cost also increases. Therefore, the method of adding aqueous ammonia to generate gold fulminate as an intermediate substance is simple, but the current situation is that gold fulminate cannot be safely handled and a simple production method cannot be adopted. The present invention aims to solve the above problems, and it is an object to provide a method for producing gold sulfite by generating gold fulminate as an intermediate substance, which is a highly safe method.

[0007] The inventors of the present invention repeatedly studied 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, but it has been found that by washing with an alkaline aqueous solution in addition to washing with pure water, 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 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 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 particle content of 800 or fewer particles with an average particle diameter of 1 μm or more present in 1 mL of the solution.

[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.

[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 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 fulminate; washing the fulminate with pure water and an alkaline aqueous solution; and adding a metallic sulfite to the washed fulminate to prepare a gold sulfite solution. This embodiment includes the above steps, 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 the arugula 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 thraic acid as an intermediate substance, and in order to enhance safety, the thraic acid, which is an intermediate substance, is modified by washing it. The inventors investigated and found that when washing the thraic acid, in addition to pure water, an alkaline aqueous solution such as sodium hydroxide aqueous solution or potassium hydroxide aqueous solution is used to modify the thraic acid, allowing for safer work 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 leijin can be arbitrarily determined. The number of washes can also be arbitrarily determined as needed. Sufficiently stable leijin can be obtained by washing once with deionized water and once with the alkaline aqueous solution, but to ensure a more reliable modification effect, it is preferable to wash twice each with deionized water and the 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 the alkaline aqueous solution to six or less. The washing order of the leijin can also be arbitrarily set. Since components derived from aqua regia may remain in the leijin, it is preferable to wash these components first with pure water before washing with the alkaline aqueous solution. Even if alkaline aqueous solution remains in the leijin, 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 electrical conductivity of 2 μS / cm or less, and more preferably deionized water with an electrical conductivity of 1 μS / cm.

[0019] In this embodiment, the alkaline aqueous solution used for washing the gold sulfite is not particularly limited, but it is preferable to use one or more selected from the group consisting of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, and potassium carbonate aqueous solution. It is preferable to select an alkaline aqueous solution that matches the type of gold sulfite salt to be obtained. For example, if you want to obtain gold sulfite sodium (sodium), it is preferable to select a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution as the alkaline aqueous solution for washing. This prevents unwanted alkali metal ions from being mixed into the target product. The alkali concentration of the alkaline aqueous solution is not particularly limited, but 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] Washing fulminate with an alkaline aqueous solution reduces the risk of explosion. Although the detailed mechanism is not clear, it can be inferred as follows: Generally, the chemical composition of fulminate is indeterminate, but it is a compound containing chlorine, nitrogen, and oxygen in addition to gold. Because it contains unstable chemical bonds, fulminate itself is unstable and prone to explosion when subjected to shock during drying. When washed with an alkaline aqueous solution, it is thought that the alkaline aqueous solution that comes into contact with the fulminate removes the chlorine, which is a factor that destabilizes the fulminate. This allows for the acquisition of stabilized fulminate. Normally, when fulminate is washed with deionized water, the atomic ratio of chlorine to gold in the fulminate (Cl / Au) is 0.05 to 0.5. On the other hand, when washed with an alkaline aqueous solution, it is less than 0.05. To obtain more stable and safer fulminate, it is preferable that the Cl / Au ratio be 0.02 or less. The components of fulminate can be analyzed using an energy-dispersive X-ray analyzer, etc. Furthermore, the stability and safety of fulminate can be confirmed by the method described in the examples.

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

[0022] Typically, gold sulfite solutions contain chloride ions derived from aqua regia as an impurity. As mentioned above, the gold fulminate is modified by washing it during the washing process, reducing the Cl / Au ratio in the fulminate. In the gold sulfite solution prepared from the modified fulminate, the chloride ion concentration is reduced to less than 3 g / L, preferably less than 1 g / L. If the fulminate is not washed during the washing process, the chloride ion concentration in the gold sulfite solution will be 3 g / L or higher. Furthermore, the gold sulfite solution has a reduced particle content of particles with an average particle size of 1 μm or more, preferably 800 particles or less per 1 mL, and more preferably 600 particles or less. The amount of particles in the gold sulfite solution can be measured using a particle counter.

[0023] The present invention will be described in more detail below 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 ammonia water was added and stirred for 45 minutes, and then allowed to stand at room temperature for 1 hour to precipitate the gold particles. Next, the precipitated gold particles were vacuum filtered by suction over a funnel to obtain gold particles containing water. Approximately 100 mL of deionized water was passed through while the suction was still maintained to wash the gold. This process was repeated twice. Subsequently, 50 mL of a 50 g / L sodium hydroxide aqueous solution was passed through to wash the gold. This process was repeated twice. The obtained gold was analyzed using an energy-dispersive X-ray analyzer to measure the atomic ratio of chlorine to gold (Cl / Au) in the gold.

[0025] The obtained gold pulverized 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 gold pulverized was simply evaluated during heating. Specifically, when heating the deionized water mixed with the gold pulverized, a dry portion formed at the top of the container. The gold pulverized adhering to this dry portion was crushed with a spatula. If a popping sound was heard, it was judged to be unstable. On the other hand, if no popping sound was heard, it was judged to be stable and safe. In this example, this popping sound check was repeated five times, and if no popping sound was heard in any of the tests, it was considered a pass (○). If a popping sound was heard even once, it was considered a fail (×). Next, the amount of particles (1 μm or larger) in 1 mL of the 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> 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, a sodium gold sulfite solution was obtained in the same manner as in Example 1.

[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 gold, sodium hydroxide aqueous solution (alkaline aqueous solution) was not used, and the gold was washed four times using only deionized water.

[0029]

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

Claims

1. 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.

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

5. A gold sulfite solution in which the chloride ion concentration in the solution is less than 1 g / L, and the number of particles larger than 1 μm present in 1 mL of the solution is 800 or less.

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