Methods for manufacturing sodium gold sulfite or potassium gold sulfite, and solutions of sodium gold sulfite or potassium gold sulfite.

Abstract

The present invention aims to provide a method for producing gold sulfite salts by generating gold fulminate as an intermediate substance, and this method is highly safe. The problem is solved by a manufacturing method comprising the following steps: dissolving a gold raw material in acid to prepare an auric acid solution; adding ammonia to the auric acid solution to precipitate the 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 salt solution.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a gold sulfite salt and a gold sulfite salt solution. Prior Technology

[0002] Gold sulfite salts are used as raw materials for gold plating solutions or for manufacturing gold compounds, and several manufacturing methods have been proposed.

[0003] Patent Document 1 discloses a prior art method that involves "adding ammonia to an auric acid chloride solution to precipitate gold fulminate, then adding sodium sulfite to the filtered and washed gold fulminate to produce a gold sulfite salt solution." However, it also reveals that gold fulminate is not only an extremely unstable substance but also poses a high risk of explosion, making it unsuitable for industrial production.

[0004] Therefore, in Patent Document 1, a method is proposed to safely synthesize gold sulfite without generating gold fulminate as an intermediate. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-146419 Summary of the Invention

[0006] [The problem that the invention aims to solve] The method for manufacturing gold sulfite salt of gold fulminate without generating the intermediate substance gold fulminate proposed in Patent Document 1 is considered to be highly safe, but the steps are complex and the manufacturing cost is also increased. Therefore, the current situation is that although the method of adding ammonia to generate gold fulminate as an intermediate substance is simpler, it cannot safely process gold fulminate, and the simple manufacturing method cannot be adopted. The present invention addresses the above-mentioned problems by providing a method for producing gold sulfite salts by generating gold fulminate as an intermediate substance, which is a highly safe method. [Technical means to solve the problem]

[0007] To address the aforementioned problems, the inventors conducted continuous research, focusing on the modification treatment of gold fulminate formed in the form of a precipitate. They discovered that gold fulminate is typically washed with pure water before being added to the next step; however, by washing with an alkaline aqueous solution in addition to pure water, the gold fulminate can be modified, minimizing the risk of explosion. Therefore, through dedicated research into the modification treatment conditions of the generated gold fulminate, this invention was completed.

[0008] This invention relates to a method for manufacturing gold sulfite, comprising the following steps: dissolving gold raw material in acid to prepare a gold acid solution; adding 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 materials mentioned above can be either recycled gold or primary gold, or a mixture thereof. Furthermore, another aspect of the present invention is a gold sulfite solution, wherein the chloride ion concentration in the solution is less than 1 g / L, and the content of particles with an average particle size of 1 μm or larger present in 1 mL of the solution is less than 800. [Effects of the Invention]

[0010] In this invention, since the safety of gold fulminate generated in the form of an intermediate substance can be improved, a simple method for manufacturing gold sulfite with high safety can be provided. Implementation

[0011] The present invention will now be described in detail. However, the description of the constituent elements described below is only one example (representative example) of the implementation of the present invention. The present invention is not limited to these contents and can be implemented in various ways within the scope of its essence.

[0012] One embodiment of the present invention is a method for manufacturing gold sulfite, comprising the following steps: dissolving gold raw material in acid to prepare a gold acid solution; adding 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. This embodiment may include the steps described above, or it may include steps other than those described above.

[0013] In the step of preparing the gold acid solution, the gold raw material is dissolved in acid. There are no particular limitations on the gold raw material; it can be virgin gold or recycled gold. Furthermore, virgin gold and recycled gold can be mixed in any ratio for use. 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 can be 1:99 to 50:50, 1:99 to 40:60, or 1:99 to 20:80. Furthermore, regarding the acid used to dissolve gold raw materials, aqua regia is generally used. A gold acid solution can be prepared by dissolving the gold raw materials in aqua regia.

[0014] This embodiment is a method for producing a gold sulfite solution by generating gold fulminate as an intermediate substance. In order to improve its safety, the gold fulminate is modified by washing the gold fulminate as an intermediate substance. After research, the inventors discovered that in the cleaning of gold fulminate, in addition to cleaning with pure water, alkaline aqueous solutions such as sodium hydroxide solution and potassium hydroxide solution are also used for cleaning. This can modify the gold fulminate and make it safe to operate in subsequent operations.

[0015] The pH of the prepared auric acid solution is usually below 5, but can also be below 3 or below 1. Since it is an aqueous solution of a strong acid, there is usually no lower limit, but sodium hydroxide solution or the like can be used to adjust the pH to above 2 and below 3.

[0016] In the step of precipitating gold fulminate, ammonia is added to the prepared gold acid solution. The amount of ammonia added is not particularly limited; sufficient to precipitate the recycled gold, primary gold, or a mixture thereof dissolved in aqua regia as gold fulminate. The pH of the solution is preferably above 8, but can also be above 9, or below 11.

[0017] Precipitated gold fulminate is usually removed by filtration and then washed. Washing is typically done with pure water. At this stage, gold fulminate is an explosive substance and must be kept constantly moist. In this formulation, in addition to washing with pure water, it is also washed with alkaline aqueous solutions such as sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate to modify the gold fulminate and obtain gold fulminate with lower explosiveness.

[0018] The concentration of the alkaline aqueous solution used for the modification of gold fulminate can be arbitrarily determined. Furthermore, the number of washes can also be determined as needed. Sufficiently stable gold fulminate can be obtained by washing once with ion-exchanged water and once with an alkaline aqueous solution. To ensure a more effective modification, it is preferable to wash twice with ion-exchanged water and twice with an alkaline aqueous solution. Washing more than three times is also possible, but this increases the processing time and the amount of waste liquid generated. Therefore, the total number of washes with ion-exchanged water and alkaline aqueous solution is preferably set to six or less. Moreover, the washing order of gold fulminate can be arbitrarily set. Since components from aqua regia may sometimes remain in the gold fulminate, it is preferable to first wash these components with pure water, followed by washing with an alkaline aqueous solution. Even if alkaline aqueous solution remains in the gold fulminate, it will not affect the next step. In addition, there are no particular restrictions on the quality of ion-exchange water used for cleaning, but it is preferable to use ion-exchange water with a conductivity of less than 2 μS / cm, and even more preferably 1 μS / cm.

[0019] In this embodiment, the alkaline aqueous solution used for cleaning gold fulminate is not particularly limited, but it is preferably selected from one or more of the group consisting of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, and potassium carbonate aqueous solution. It is more suitable to select an alkaline aqueous solution that matches the type of gold sulfite salt of the target. For example, when gold sulfite sodium sulfite is desired as the gold sulfite salt, it is more suitable to select sodium hydroxide aqueous solution or sodium carbonate aqueous solution as the alkaline aqueous solution for cleaning. This prevents unwanted alkali metal ions from contaminating the target substance. There is no particular limitation on the alkali concentration of the alkaline aqueous solution, which 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 risk of explosion is reduced when gold fulminate is washed with an alkaline aqueous solution. While the detailed mechanism is not fully understood, it can be hypothesized as follows: Generally, the chemical composition of gold fulminate is not fixed, but it contains compounds of chlorine, nitrogen, and oxygen in addition to gold. Due to the presence of unstable chemical bonds, gold fulminate itself is also unstable and prone to explosion due to impact during drying. It is believed that washing with an alkaline aqueous solution removes chlorine, the main cause of instability in gold fulminate. This results in stabilized gold fulminate. Typically, when gold fulminate is washed with deionized water, the atomic ratio of chlorine to gold (Cl / Au) is 0.05 to 0.5. On the other hand, when washed with an alkaline aqueous solution, the ratio is less than 0.05. For more stable and safer gold fulminate, a Cl / Au ratio below 0.02 is preferred. Furthermore, the composition of gold fulminate can be analyzed using an energy-dispersive X-ray diffraction (EDD) analyzer. Also, the stability and safety of gold fulminate can be confirmed using the methods 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 extracted gold fulminate to prepare the gold sulfite solution. The gold sulfite in the solution is typically sodium gold sulfite or potassium gold sulfite, but is not limited to these. Gold fulminate can be added to pure water, followed by the addition of a metal salt of sulfite such as sodium sulfite, or gold fulminate can be added directly to the sulfite solution.

[0022] Typically, gold sulfite solutions contain chloride ions from aqua regia as impurities. As mentioned earlier, gold fulminate is cleaned in the cleaning step, thereby being modified and reducing the Cl / Au ratio in the gold fulminate. 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. When the gold fulminate is not cleaned in the cleaning step, the chloride ion concentration in the gold sulfite solution is 3 g / L or higher. Furthermore, the content of particles with an average particle size of 1 μm or larger in the gold sulfite solution is reduced, preferably to less than 800 particles per 1 mL, and more preferably to less than 600 particles per 1 mL. The particle count in the gold sulfite solution can be determined using a particle counter. [Example]

[0023] The present invention will be described in more detail below using examples, but of course the scope of the present invention is not limited to the examples described.

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

[0025] The obtained gold fulminate was mixed with about 150 ml of deionized water, heated to above 65°C, stirred and 25 g of sodium sulfite was added at the same time, kept for about 3 hours, and then left to stand for 1 hour to cool, so as to obtain a sodium gold sulfite solution. The stability and safety of gold fulminate were simply evaluated during heating. Specifically, when the ion-exchanged water mixed with gold fulminate was heated, a dry portion was formed at the top of the container. The gold fulminate adhering to this dry portion was crushed with a spatula. If a cracking sound was detected, the gold fulminate was determined to be unstable. On the other hand, if no cracking sound was detected, the gold fulminate was determined to be stable and safe. In this embodiment, the cracking sound check was repeated 5 times. If no cracking sound was detected in all five instances, it was considered acceptable (〇). If a cracking sound was detected, even once, it was considered unacceptable (×). Next, the particle count (greater than 1 μm) in 1 mL of sodium gold sulfite solution was determined using a particle counter. The chloride ion concentration in the sodium gold sulfite solution was also measured. These results are shown in Table 1.

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

[0027] <Example 3> Except for changing the gold raw material to a mixture of recycled gold and original gold in a 1:1 weight ratio, the gold sodium sulfite solution was obtained in the same manner as in Example 1.

[0028] <Comparative Example 1> Except for the cleaning step of gold fulminate, in which sodium hydroxide aqueous solution (alkaline aqueous solution) was not used and only ion-exchanged water was used for 4 flushing steps, the experiments were carried out in the same manner as in Example 1.

[0029] [Table 1] Example 1 Example 2 Example 3 Comparative Example 1 Types of gold raw materials Recycle original mix (1:1) Recycle Gold fulminate cleaning Pure water rinsing (number of flushing cycles) 2 2 2 4 sodium hydroxide aqueous solution concentration 50g / L 10g / L 50g / L none Number of times sodium hydroxide aqueous solution is passed through 2 2 2 none Composition of gold fulminate after cleaning and modification Cl / Au = 0.005 Cl / Au=0.02 Cl / Au=0.004 Cl / Au = 0.08 Stability of gold fulminate ○ ○ ○ × Chloride ion concentration in sodium gold sulfite solution <1g / L <1g / L <1g / L 3g / L Number of particles in sodium gold sulfite solution (1 ml) 310 520 450 900

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

Claims

1. A method for manufacturing sodium gold sulfite or potassium gold sulfite, comprising the following steps: dissolving a gold raw material in acid to prepare a gold acid solution; adding ammonia to the gold acid solution to precipitate gold fulminate; washing the gold fulminate with pure water and one or more alkaline aqueous solutions selected from the group consisting of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, and potassium carbonate aqueous solution; and adding a metal sulfite to the washed gold fulminate to prepare a sodium gold sulfite solution or a potassium gold sulfite solution.

2. The method for manufacturing sodium gold sulfite or potassium gold sulfite as described in claim 1, wherein, The gold raw material used in the above steps for preparing the gold acid solution is recycled gold.

3. A method for manufacturing sodium gold sulfite or potassium gold sulfite as described in claim 1, wherein, The gold raw material used in the above steps for preparing the gold acid solution is a mixture of recycled gold and primary gold.

4. A method for manufacturing sodium gold sulfite or potassium gold sulfite as described in claim 1, wherein, The gold raw material used in the above steps for preparing the gold acid solution is raw gold.

5. A sodium gold sulfite solution or a potassium gold sulfite solution, wherein 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 less than 800.