Method for producing high purity gold

Abstract

The application discloses a preparation method of high-purity gold and relates to the field of high-purity noble metal preparation. The method comprises the following steps: (S1) adding an acid solution to alloy gold to dissolve, and collecting a filtrate through centrifugal separation and / or filtration; (S2) adding an alkaline solution to the filtrate to adjust the pH value of the solution, adding a reducing agent, heating and stirring, centrifugal separation and / or filtration, and obtaining a first leaching solution; (S3) adding a reducing agent to the first leaching solution, heating and stirring, and filtering to obtain second reduced gold; (S4) washing the second reduced gold, immersing the second reduced gold in an ammonium hydrogen fluoride solution, and centrifugal separation and / or filtration, washing, and collecting first washed gold; and (S5) immersing the first washed gold in ammonia water, centrifugal separation and / or filtration, washing, drying, and ingot casting to obtain high-purity gold ingots. The method can directly use alloy gold with low gold content as raw material to produce high-purity gold, the process is simple, and the content of iron, silver and other metal impurities is less than 0.0001%.

Description

Technical Field

[0001] This application relates to a method for preparing high-purity gold, belonging to the field of high-purity precious metal preparation. Background Technology

[0002] High-purity gold has excellent electrical conductivity, thermal conductivity, oxidation resistance, and corrosion resistance, and is widely used in high-tech fields such as electronics, communications, aerospace, sputtering targets, and optoelectronics. For example, gold and its alloys are mainly used as bonding wires, internal lead materials, thin film materials, soldering materials, and ohmic contact materials in transistors and various integrated circuits for electronic packaging.

[0003] Currently, high-purity gold production processes include electrolysis, solvent extraction, and chemical reduction. Electrolysis has drawbacks such as stringent requirements for raw materials, poor raw material adaptability, and long production cycles. Solvent extraction uses extractants like diethyl ether and dibutylcarbidol to prepare high-purity gold, but the resulting high-purity gold is easily coated with organic solvents, affecting gold purity. Furthermore, the extractants are highly volatile, creating a poor production environment and posing safety hazards during operation. Chemical reduction is simple, easy to operate, produces less gold backlog throughout the process, has a high direct product recovery rate, and offers good controllability and flexibility in production capacity, allowing for large-scale production regardless of the amount of raw materials. It is particularly adaptable to raw materials, allowing for flexible selection of appropriate process conditions based on the properties of the raw materials. However, the silver content in gold powder processed by chemical reduction remains consistently around 0.0003%, and the iron content around 0.0002%. These impurities enter the gold ingot during the subsequent melting and casting process, leading to excessive impurities and rendering the gold unusable as a high-purity gold raw material.

[0004] Patent CN114453589A discloses a method for preparing high-purity gold, which involves: (1) dissolving gold raw materials in aqua regia to obtain a chloroauric acid solution; (2) adding potassium hydroxide solution to the chloroauric acid solution to obtain a potassium aurate solution; (3) adding dilute sulfuric acid solution to the potassium aurate solution to obtain a gold oxide precipitate; and (4) heating and decomposing the gold oxide precipitate to obtain high-purity gold. This method cannot process raw materials with low gold content, and the iron and silver impurity content in the final high-purity gold remains stable at around 0.0002%, making it impossible to further reduce the iron and silver content in the high-purity gold. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-purity gold. This method uses conventional raw materials with low gold content to prepare high-purity gold, which significantly reduces the content of silver and iron elements in the high-purity gold, improves the purity of the high-purity gold, and minimizes the loss of gold.

[0006] To achieve the above objectives, this application provides the following technical solution: a method for preparing high-purity gold, comprising the following steps:

[0007] (S1) Add an acidic solution to the alloyed gold to dissolve it, and then separate the solid and liquid by centrifugation and / or filtration, and collect the filtrate;

[0008] (S2) Add an alkaline solution to the filtrate to adjust the pH value of the solution to 0-0.5, then add a reducing agent and stir at 75-90℃ for 1.5-2.5 hours. Separate the solid and liquid by centrifugation and / or filtration to obtain the first leachate and the first reduced gold.

[0009] (S3) Add a reducing agent to the first leachate and stir at 75-90°C for 1.5-2.5 hours. Separate the solid and liquid by centrifugation and / or filtration to obtain the second leachate and the second reduced gold.

[0010] (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution. Solid-liquid separation and washing are performed by centrifugation and / or filtration, and the first washed gold is collected.

[0011] (S5) The first washed gold is soaked in ammonia water and then separated into solid and liquid by centrifugation and / or filtration to obtain the second washed gold. The second washed gold is dried and cast into ingots to obtain high-purity gold ingots. Preferably, it is washed with ultrapure water more than 3 times until neutral.

[0012] Specifically, it also includes a step of pulverizing the alloy gold in a molten state before step (S1).

[0013] Specifically, the silver content in alloy gold is less than 6%.

[0014] Specifically, the gold content in alloyed gold is 94%-99.99%.

[0015] Specifically, in step (S1), the acidic solution is one or more of aqua regia, chlorine-hydrochloric acid solution, and chlorate-hydrochloric acid solution.

[0016] Specifically, the alkaline solution in step (S2) is a sodium hydroxide solution, a sodium carbonate solution, or a potassium hydroxide solution.

[0017] Specifically, in steps (S2) and (S3), the reducing agent is hydrazine hydrate, sodium sulfite, sodium metabisulfite, sulfur dioxide, or oxalic acid.

[0018] Specifically, in step (S2), the amount of reducing agent added is 0.01-0.1 times the gold content in the alloy gold; in step (S3), the amount of reducing agent added is 0.8-0.9 times the gold content in the alloy gold.

[0019] Specifically, in steps (S4) and (S5), the soaking time is 1-4 hours, and stirring is maintained during the soaking process. Preferably, the stirring speed is 300 r / min.

[0020] Specifically, the gold content percentage in the second reduced gold is 99.99% and the gold content percentage in the second washed gold is 99.999% or higher.

[0021] Specifically, high-purity gold ingots have a gold content greater than 99.999%.

[0022] The beneficial effects of this application include, but are not limited to:

[0023] 1. According to the method for preparing high-purity gold provided in this application, high-purity gold can be directly produced from alloyed gold with low gold content as raw material, and the content of silver and iron elements in high-purity gold is significantly reduced, thereby improving the purity of high-purity gold. Furthermore, the gold loss is small and the impurity removal effect is stable, providing good guidance for the production of high-purity gold and making it suitable for large-scale promotion and application.

[0024] 2. According to the method for preparing high-purity gold provided in this application, before dissolving the composite gold in an acidic solution, the composite gold is first pulverized to increase the specific surface area of ​​the gold and accelerate the dissolution rate of the gold.

[0025] 3. According to the method for preparing high-purity gold provided in this application, when the components of the alloy gold are unknown, a small amount of reducing agent is first added to remove suspended matter in the solution that is insoluble in acid and cannot be removed by filtration. Then, a small amount of reducing agent is added to reduce most of the gold in the solution, thereby reducing the possibility that the reduced gold contains suspended matter that is insoluble in acid.

[0026] 4. According to the high-purity gold preparation method provided in this application, gold powder is soaked successively in ammonium bifluoride solution and ammonia solution, with stirring maintained during the soaking process. Iron ions are removed by the reaction of ammonium bifluoride solution, and silver chloride is removed by the reaction of ammonia solution, ensuring that impurities of iron and silver cannot be re-adsorbed. Finally, ultrapure water is used for multiple washings to remove the iron and silver compounds generated in the reaction. This significantly reduces the iron and silver content in the high-purity gold, making the content of iron, silver, and other metal impurities in the final high-purity gold stably below 0.0001%, improving the purity of the high-purity gold, and ensuring stable quality control, making it suitable for long-term application. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. It should be noted that the following embodiments should not be construed as limiting the scope of protection of the present invention. Simple substitutions or adjustments made by those skilled in the art based on the content of the present invention are all within the scope of protection of the present invention. Unless otherwise specified, the raw materials and catalysts in the embodiments of this application were all purchased commercially.

[0028] Example 1

[0029] (S1) Powder the alloyed gold with a gold content of 94%, add aqua regia to dissolve and filter, and collect the filtrate;

[0030] (S2) Add potassium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.1, then add sodium sulfite at 0.01 times the gold content in the alloyed gold, stir at 75°C for 1.5 hours, centrifuge to obtain the first leachate and the first reduced gold;

[0031] (S3) Add sodium sulfite at 0.8 times the gold content in the alloyed gold to the first leaching solution, stir at 75°C for 1.5 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0032] (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution for 1 hour, stirred continuously at 300 r / min, filtered, and the first washed gold is collected.

[0033] (S5) Soak the first washed gold in ammonia water for 1 hour, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0034] Example 2

[0035] (S1) Powder the alloy gold with a gold content of 99%, add chlorine-hydrochloric acid solution and chlorate-hydrochloric acid solution with a weight ratio of 1:1 to dissolve and filter, and collect the filtrate;

[0036] (S2) Add sodium carbonate solution to the filtrate, adjust the pH of the solution to 0.5, then add oxalic acid at 0.1 times the gold content in the alloyed gold, stir at 90°C for 2.5 hours, filter, and obtain the first leachate and the first reduced gold;

[0037] (S3) Add oxalic acid at 0.9 times the gold content in the alloyed gold to the first leachate, stir at 90°C for 2.5 hours, filter, and obtain the second leachate and the second reduced gold;

[0038] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 4 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0039] (S5) Soak the first washed gold in ammonia water for 4 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0040] Example 3

[0041] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0042] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0043] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leaching solution, stir at 80°C for 2 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0044] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 3 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0045] (S5) Soak the first washed gold in ammonia water for 3 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0046] Example 4

[0047] (S1) Powder the alloyed gold with a gold content of 96%, add chlorate-hydrochloric acid solution to dissolve and filter, and collect the filtrate;

[0048] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.4, then add sulfur dioxide at 0.02 times the gold content in the alloyed gold, stir at 90°C for 1.7 hours, filter, and obtain the first leaching solution and the first reduced gold;

[0049] (S3) Add sulfur dioxide at 0.85 times the gold content in the alloyed gold to the first leaching solution, stir at 85°C for 1.5 hours, and centrifuge to obtain the second leaching solution and the second reduced gold.

[0050] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 2 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0051] (S5) Soak the first washed gold in ammonia water for 2 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0052] Example 5

[0053] (S1) Powder the alloyed gold with a gold content of 97%, add chlorate-hydrochloric acid solution to dissolve and filter, and collect the filtrate;

[0054] (S2) Add sodium hydroxide solution to the filtrate, adjust the pH of the solution to 0.5, then add sodium metabisulfite at 0.02 times the gold content in the alloyed gold, stir at 90°C for 1.7 hours, filter, and obtain the first leachate and the first reduced gold;

[0055] (S3) Add sodium metabisulfite at 0.85 times the gold content in the alloyed gold to the first leaching solution, stir at 80°C for 1.5 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0056] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 2 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0057] (S5) Soak the first washed gold in ammonia water for 2 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0058] Comparative Example 1

[0059] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0060] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0061] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leaching solution, stir at 80°C for 2 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0062] (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution for 3 hours. It is stirred continuously at 300 r / min, filtered, washed three times with ultrapure water until neutral, the first washed gold is collected, dried, and cast into ingots to obtain high-purity gold ingots.

[0063] Comparative Example 2

[0064] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0065] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0066] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leaching solution, stir at 80°C for 2 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0067] (S4) The second reduced gold is washed and soaked in ammonia water for 3 hours. It is continuously stirred at 300 r / min, centrifuged and washed three times with ultrapure water until neutral to obtain the first washed gold. The first washed gold is dried and cast into an ingot to obtain a high-purity gold ingot.

[0068] Comparative Example 3

[0069] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0070] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0071] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leaching solution, stir at 80°C for 2 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0072] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 0.3 h, stirred continuously at 300 r / min, and centrifuged to collect the first washed gold.

[0073] (S5) Soak the first washed gold in ammonia water for 0.3 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0074] Comparative Example 4

[0075] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0076] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.1 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0077] (S3) Add hydrazine hydrate at 0.98 times the gold content in the composite gold to the first leachate, stir at 80°C for 2 hours, filter, and obtain the second leachate and the second reduced gold;

[0078] (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution for 3 hours, then centrifuged and washed to collect the first washed gold;

[0079] (S5) Soak the first washed gold in ammonia water for 3 hours, filter it, and wash it three times with ultrapure water until it is neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0080] Comparative Example 5

[0081] (S1) Add aqua regia to the alloyed gold with a gold content of 98% to dissolve and filter, and collect the filtrate;

[0082] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0083] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leaching solution, stir at 80°C for 2 hours, filter, and obtain the second leaching solution and the second reduced gold.

[0084] (S4) The second reduced gold was washed and soaked in ammonium bifluoride solution for 3 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0085] (S5) Soak the first washed gold in ammonia water for 3 hours, stir continuously at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0086] Comparative Example 6

[0087] (S1) Powder the alloyed gold with a gold content of 98%, add aqua regia to dissolve and filter, and collect the filtrate;

[0088] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.3, then add hydrazine hydrate at 0.9 times the gold content in the alloyed gold, stir at 80°C for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0089] (S4) The first reduced gold was washed and soaked in ammonium bifluoride solution for 3 hours. The mixture was stirred continuously at 300 r / min and centrifuged to collect the first washed gold.

[0090] (S5) Soak the first washed gold in ammonia water for 3 hours with continuous stirring at 300 r / min, filter, and wash three times with ultrapure water until neutral to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0091] Comparative Example 7

[0092] (S1) Powder the gold alloy with a gold content of 90%, add aqua regia to dissolve it, filter it, and collect the filtrate;

[0093] (S2) Add sodium hydroxide solution to the filtrate to adjust the pH value of the solution to 0.5, then add hydrazine hydrate at 0.03 times the gold content in the alloyed gold, stir for 2 hours, filter, and obtain the first leachate and the first reduced gold;

[0094] (S3) Add hydrazine hydrate at 0.85 times the gold content in the composite gold to the first leachate, stir for 2 hours, filter, and obtain the second leachate and the second reduced gold.

[0095] (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution for 0.5 h, then centrifuged and washed to collect the first washed gold;

[0096] (S5) Soak the first washed gold in ammonia water for 0.5 hours, filter it, and wash it once with ultrapure water to obtain the second washed gold. Dry the second washed gold and cast it into an ingot to obtain a high-purity gold ingot.

[0097] Examples 1-5 and Comparative Examples 1-7 were analyzed according to GB / T25934.1-2010, and the specific data are shown in Table 1.

[0098]

[0099]

[0100] Table 1

[0101] The results show that the silver and iron impurity content in the high-purity gold obtained using the method defined in this application is consistently around 0.0001%, and the impurity removal effect is optimal under the parameters used in Example 3. In contrast, the high-purity gold prepared in Comparative Examples 1-8 has silver and iron impurity contents of approximately 0.0002%.

[0102] The difference between Comparative Example 1 and Example 3 is that the step (S5) of immersing the first washed gold in ammonia water is omitted. The rest is the same as in Example 3. The ammonia water cannot complex silver chloride, resulting in the silver impurities not being effectively reduced.

[0103] The difference between Comparative Example 2 and Example 3 is that the step (S4) of immersing the second reduced gold in the ammonium bifluoride solution is omitted. The rest is the same as Example 3. The reaction of ammonium bifluoride complexing iron cannot occur, resulting in the inability to effectively reduce iron impurities.

[0104] The difference between Comparative Example 3 and Example 3 is that in steps (S4) and (S5), the soaking time is shortened to 0.3 h, while the rest is the same as in Example 3. The shortened soaking time affects the impurity removal effect.

[0105] The difference between Comparative Example 4 and Example 3 is that in step (S3), an excess of reducing agent is added. The rest is the same as in Example 3. The excess reduction will first reduce platinum, silver, palladium and copper. Silver will be reduced to elemental form, resulting in a significant increase in silver content, which cannot be removed by washing with ammonia.

[0106] The difference between Comparative Example 5 and Example 3 is that in step (S1), the gold was not pulverized before being dissolved in the acidic solution. The rest is the same as in Example 3. Without pulverization, the gold dissolution rate is reduced, resulting in incomplete dissolution. Although solid-liquid separation is performed subsequently to reduce the dissolved solution and obtain high-purity gold ingots, the dissolution time is prolonged and the amount of gold lost is large.

[0107] The difference between Comparative Example 6 and Example 3 is that in step (S2), the reducing agent is added only once, while the rest is the same as in Example 3. This application removes suspended matter in the solution that is insoluble in acid and cannot be removed by filtration by adding a small amount of reducing agent, and then reduces most of the gold in the solution by adding insufficient reducing agent. When the impurity composition in the alloy gold is unknown, it is impossible to remove the suspended matter that is insoluble in acid by adding reducing agent once, resulting in an increase in impurity content. When the composition of the alloy gold is known, the gold can be reduced by adding insufficient reducing agent once, but the impurity removal effect is inferior to this method.

[0108] The difference between Comparative Example 7 and Example 3 is that, in step (S1), the gold alloy with a gold content of 90% is treated; in step (S2), the pH of the solution is adjusted to 0.5; in steps (S3) and (S4), the temperature is not increased during stirring; and in step (S5), the first washing gold is washed once, which results in impurities not being significantly removed and the impurity removal effect being unstable.

[0109] The above data show that the method of this application can significantly reduce the content of silver ions and iron ions in high-purity gold, controlling their respective contents to 0.0001%, and the quality control is stable, making it suitable for long-term application.

[0110] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing high-purity gold, characterized in that, Includes the following steps: (S1) Add an acidic solution to the alloyed gold to dissolve it, and perform solid-liquid separation by centrifugation and / or filtration, and collect the filtrate; (S2) Add an alkaline solution to the filtrate to adjust the pH value of the solution to 0-0.5, then add a reducing agent and stir at 75-90℃ for 1.5-2.5 hours. Separate the solid and liquid by centrifugation and / or filtration to obtain the first leachate and the first reduced gold. The amount of the reducing agent added is 0.01-0.1 times the gold content in the alloyed gold. (S3) Add a reducing agent to the first leachate and stir at 75-90°C for 1.5-2.5 hours. Separate the solid and liquid by centrifugation and / or filtration to obtain a second leachate and a second reduced gold. The amount of the reducing agent added is 0.8-0.9 times the gold content in the alloyed gold. (S4) The second reduced gold is washed and soaked in ammonium bifluoride solution. Solid-liquid separation and washing are performed by centrifugation and / or filtration, and the first washed gold is collected. (S5) The first washed gold is soaked in ammonia water, and solid-liquid separation and washing are carried out by centrifugation and / or filtration to obtain the second washed gold. The second washed gold is dried and cast into ingots to obtain high-purity gold ingots.

2. The method for preparing high-purity gold as described in claim 1, characterized in that, It also includes a step of pulverizing the alloy gold in a molten state before step (S1).

3. The method for preparing high-purity gold as described in claim 1, characterized in that, The silver content in alloy gold is less than 6%.

4. The method for preparing high-purity gold as described in claim 1, characterized in that, In step (S1), the acidic solution is one or more of aqua regia, chlorine-hydrochloric acid solution, and chlorate-hydrochloric acid solution.

5. The method for preparing high-purity gold as described in claim 1, characterized in that, In step (S2), the alkaline solution is a sodium hydroxide solution, a sodium carbonate solution, or a potassium hydroxide solution.

6. The method for preparing high-purity gold as described in claim 1, characterized in that, In steps (S2) and (S3), the reducing agent is hydrazine hydrate, sodium sulfite, sodium metabisulfite, sulfur dioxide, or oxalic acid.

7. The method for preparing high-purity gold as described in claim 1, characterized in that, In steps (S4) and (S5), the soaking time is 1-4 hours, and stirring is maintained during the soaking process.

8. The method for preparing high-purity gold as described in claim 1, characterized in that, The gold content in the second reduced gold is 99.99%, and the gold content in the second washed gold is 99.999% or higher.

9. The method for preparing high-purity gold as described in claim 1, characterized in that, High-purity gold ingots have a gold content greater than 99.999%.

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