Method for synthesizing potassium gold cyanide from gold-plated waste

Abstract

The present application relates to the field of electroplating technology and discloses a method for synthesizing potassium gold cyanide from gold-plated waste. The present application rationally utilizes gold-plated waste in the electroplating industry. By using a combined reducing agent to recover and purify the gold-containing solution obtained from the gold-plated waste, the gold mud reduction time can be shortened and the gold mud reduction efficiency can be improved. The purified gold mud is reacted with potassium cyanide and hydrogen peroxide in a one-step reaction to synthesize potassium gold cyanide. This method not only has a high yield and purity, but is also simpler and safer than conventional processes. It is conducive to the large-scale synthesis and recycling of gold salts from gold-plated waste and the mass production of gold-containing ore mining, providing an environmentally friendly, low-cost, and high-yield process route for the future production of potassium gold cyanide.

Description

Technical Field

[0001] The present application relates to the field of electroplating technology, and in particular to a method for synthesizing potassium gold cyanide from gold plating waste. Background Art

[0002] Potassium gold cyanide, an essential salt that provides a source of gold ions in the gold plating process, plays a crucial role in gold plating production. With the rapid development of the potassium gold cyanide market and the increase in industry production capacity, potassium gold cyanide production has gradually upgraded to high-tech, high-value-added products. However, potassium gold cyanide is a highly toxic substance. Due to the varying scale and low technical level of enterprises, its production and transportation pose significant safety risks and environmental pollution, which to some extent restricts the standardized development of the potassium gold cyanide market.

[0003] Currently, the main processes for producing potassium gold cyanide are chemical and electrolytic methods. The chemical method involves reacting a gold fulminate precipitate along with filter paper with a potassium cyanide solution, slowly heating and dissolving it to obtain a colorless, transparent solution. Drying and crystallizing the solution yields a powdered solid of potassium gold cyanide. However, dry gold fulminate can explode with the slightest vibration, making it relatively dangerous. The electrolytic method involves rolling gold into thin sheets to serve as electrodes. These sheets are then used in a diaphragm electrolytic cell, with a stainless steel sheet as the cathode and a potassium cyanide solution as the electrolyte. The thin gold sheet at the anode gradually dissolves into Au(CN). 2- When the thin gold flakes are completely dissolved, the potassium gold cyanide generated by electrolysis is purified by low-temperature cooling crystallization, the residual potassium cyanide is separated, and the purification, condensation, and drying are repeated. The potassium gold cyanide crystals are vacuum-baked to obtain the finished product. The electrolytic method has a good impurity removal effect, but its yield is low and the consumption is high. Summary of the Invention

[0004] In view of this, the purpose of the present application is to provide a method for synthesizing potassium gold cyanide from gold-plated waste, so that the method uses gold-plated waste from the electroplating industry as raw material to purify gold mud, and then synthesizes high-purity and high-yield potassium gold cyanide in a one-step reaction. In addition, the gold reduction reaction time can be shortened and the gold reduction rate can be increased during the purification of the gold mud, while having a gold purity of more than 99.9%.

[0005] In order to solve the above technical problems / achieve the above objectives or at least partially solve the above technical problems / achieve the above objectives, the present application provides a method for synthesizing potassium gold cyanide from gold plating waste, comprising:

[0006] Gold-plated waste is added to the gold stripping solution for reaction, the gold-containing solution is filtered out, and then solid gold is obtained through a replacement reaction;

[0007] The solid gold is dissolved in a mixed acid solution of hydrochloric acid and nitric acid, and then a combined reducing agent is added to carry out a reduction reaction until no solid precipitate is produced, and the solid precipitate is separated to form gold mud; the combined reducing agent includes urea and sodium bisulfite;

[0008] The gold mud is reacted with potassium cyanide and hydrogen peroxide, and after the reaction is complete, potassium cyanide is obtained by evaporation and crystallization.

[0009] Optionally, the deposit refund solution includes deposit refund powder, hydrogen peroxide and water; further optionally, the deposit refund solution includes 50-150g of deposit refund powder, 20-50mL of hydrogen peroxide and 100-200mL of water.

[0010] Optionally, the solid gold is obtained by the replacement reaction by using a metal element with higher activity than gold to carry out a replacement reaction to obtain the solid gold; further optionally, the metal element with higher activity than gold includes zinc.

[0011] Optionally, the mass ratio of urea to sodium bisulfite in the combined reducing agent is (20-150):(6-45).

[0012] Optionally, the concentration of the potassium cyanide is 4-6%, and the concentration of the hydrogen peroxide is 3%.

[0013] Optionally, before the gold mud reacts with potassium cyanide and hydrogen peroxide, the following steps are further included:

[0014] Wash the gold mud with hot pure water, then boil it with ammonia water, filter and dry it.

[0015] Optionally, when the gold mud reacts with potassium cyanide and hydrogen peroxide, the method further comprises: introducing oxygen into the reaction system.

[0016] The present application rationally utilizes gold-plated waste in the electroplating industry. By using a combined reducing agent to recover and purify the gold-containing solution obtained from the gold-plated waste, the gold mud reduction time can be shortened and the gold mud reduction efficiency can be improved. The purified gold mud is reacted with potassium cyanide and hydrogen peroxide in a one-step reaction to synthesize potassium gold cyanide, which not only has a high yield and purity, but is also simpler and safer than conventional processes, is conducive to the large-scale synthesis and recycling of gold salts from gold-plated waste and the mass production of gold-containing ore mining, and provides a set of environmentally friendly, low-consumption, and high-yield process routes for the future production of potassium gold cyanide. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application.

[0018] Figure 1 Shown is a physical picture of the gold mud obtained in this application;

[0019] Figure 2 Shown is a physical picture of potassium gold cyanide synthesized in this application. DETAILED DESCRIPTION

[0020] The present application discloses a method for synthesizing potassium gold cyanide from gold-plated waste. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the method. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all deemed to be included in this application. The method described in this application has been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method described herein without departing from the content, spirit and scope of this application to implement and apply the technology of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0021] It should be noted that, in this document, if relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" appear, they are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device comprising the elements. At the same time, the embodiments in this application and the features in the embodiments can be combined with each other in the absence of conflict.

[0022] This application studies the production of gold salts from currently common international scrap gold recycling machines, and develops a process for the continuous synthesis of gold cyanide salts from gold-plated waste. This application avoids the dangers and low product quality of the regin method and the high cost of the electrolysis method. By utilizing the key technology of a one-step synthesis of potassium gold cyanide from gold-plated waste, this process route comprehensively improves synthesis costs, increases synthesis efficiency, and reduces risks.

[0023] In the present application, a method for synthesizing potassium gold cyanide from gold plating waste is specifically provided, comprising:

[0024] Gold-plated waste is added to the gold stripping solution for reaction, the gold-containing solution is filtered out, and then solid gold is obtained through a replacement reaction;

[0025] The solid gold is dissolved in a mixed acid solution of hydrochloric acid and nitric acid, and then a combined reducing agent is added to carry out a reduction reaction until no solid precipitate is produced. The solid precipitate is separated to form gold mud. The combined reducing agent includes urea and sodium bisulfite. The sodium bisulfite has a reducing effect, and the urea has a promoting effect on the reducing effect of the sodium bisulfite, thereby improving the reduction efficiency. At the same time, the urea removes excess nitric acid and hydrochloric acid, thereby reducing the consumption of side reactions of the sodium bisulfite with the nitric acid and hydrochloric acid.

[0026] Among them, the reaction formula of nitric acid, hydrochloric acid and gold is: Au+HNO3+4HCl→H[AuCl4]+NO↑+2H2O;

[0027] The reaction formula of sodium bisulfite and gold is: 3NaHSO3+2AuCl3+3H2O→3NaHSO4+6HCl+2Au;

[0028] The gold mud is reacted with potassium cyanide and hydrogen peroxide, and after the reaction is complete, potassium gold cyanide is evaporated and crystallized; the reaction formula is: Au+H2O2+KCN+O2→KAu(CN)4+H2O+O2.

[0029] In certain embodiments of the present application, the gold content of the gold-plated scrap is 0.1-3 g / 1000 g. To more fully recover the gold from the gold-plated scrap, in certain embodiments of the present application, gold removal powder and hydrogen peroxide are mixed in a certain proportion, added to hot water at 60-80°C, and stirred for at least 30 minutes to obtain a gold removal solution, thereby better recovering the gold. In other embodiments of the present application, the mass-to-volume ratio of the gold removal powder, hydrogen peroxide, and water is 50-150 g:20-50 mL:100-200 mL, for example, 50 g:20 mL:100 mL, 50 g:30 mL:200 mL, 100 g:40 mL:100 mL, 100 g:35 mL:200 mL, 50 g:30 mL:100 mL, 150 g:50 mL:100 mL, and so on.

[0030] In certain embodiments of the present application, the solid gold is obtained by the replacement reaction using a metal element with a higher activity than gold to obtain solid gold; further optionally, the metal element with a higher activity than gold includes zinc. Taking zinc powder as an example, the replacement reaction is: Zn + Au 2+ →Zn 2+ +Au, in order to replace all gold as much as possible, the amount of zinc powder used is generally excessive. For gold-plated scrap with a gold content of 0.1-3g / 1000g, the amount of zinc powder used in the specific embodiments of this application is generally 15-50g of zinc powder. In other embodiments of this application, the gold-plated scrap is added to the gold stripping solution, stirred at 50-70°C for 1-2 hours, and the gold-containing solution is filtered out after standing.

[0031] In certain embodiments of the present application, solid gold after the replacement reaction is completed is added to a mixed acid solution of concentrated nitric acid and concentrated hydrochloric acid to dissolve the impure solid gold and then filter out the impurities to purify the gold; in other embodiments of the present application, the mass ratio of concentrated nitric acid to concentrated hydrochloric acid in the mixed acid solution is 3:1.

[0032] In certain embodiments of the present application, the mass ratio of urea to sodium bisulfite in the combined reducing agent is (20-150):(6-45), for example, 50:15, 20:6, 150:45, and the like.

[0033] In certain embodiments of the present application, when the gold mud is reacted with potassium cyanide and hydrogen peroxide, in order to complete the reaction, both potassium cyanide and hydrogen peroxide are in excess, but the reaction method can affect the reaction efficiency; in certain embodiments of the present application, some potassium cyanide and hydrogen peroxide are first added until the liquid level covers the gold mud, and then potassium cyanide and hydrogen peroxide are added dropwise and stirred to react until the gold mud is completely dissolved. The dropwise addition rate is 90-120 drops / minute. Compared with the full mixing and stirring reaction method, the continuous dropwise addition method has higher reaction efficiency. In other embodiments of the present application, in order to further improve the reaction efficiency, oxygen can also be introduced into the reaction system to accelerate the oxidation reaction, and the oxygen introduction rate is about 1L / min.

[0034] In certain embodiments of the present application, the mass percentage concentration of the potassium cyanide is about 4-6%, and the mass percentage concentration of the hydrogen peroxide is about 3%. Within this concentration range, the yield of the potassium gold cyanide obtained is better, and too high or too low concentrations are not conducive to obtaining a higher yield; in other embodiments of the present application, when the reaction is carried out in a dropwise manner, the volume ratio of the 5% potassium cyanide and 3% hydrogen peroxide initially added is (2-3): (1-2), for example, 2:1, 3:2, 3:1, and the like.

[0035] In certain embodiments of the present application, before reacting the gold mud with potassium cyanide and hydrogen peroxide, the process further includes: washing the gold mud with hot pure water, then boiling it with ammonia, and filtering and drying it. More specifically, the gold mud is washed 3-5 times with hot pure water, and finally boiling it with 20% ammonia, and filtering and drying it.

[0036] In the comparative experiments provided in this application, unless otherwise specified, all experimental conditions and materials, except for the differences noted in each group, were kept consistent to ensure comparability. Furthermore, all materials used in this application were commercially available, including zinc powder from Tianjin Chemical Reagent Plant No. 2, gold removal powder and sodium bisulfite from Beijing Yili Fine Chemicals Co., Ltd., nitric acid, hydrochloric acid, hydrogen peroxide, and ammonia produced by Tianjin Sanda Trading Co., Ltd., and potassium cyanide produced by Tianjin Jinruida.

[0037] The following further describes a method for synthesizing potassium gold cyanide from gold-plated waste provided in this application.

[0038] Example 1:

[0039] (1) Preparation of gold removal solution

[0040] Add 50g of gold removal powder and 20ml of hydrogen peroxide into 100ml of deionized water and mix them. Heat the mixed solution to 60℃ and stir for 30 minutes.

[0041] (2) Preparation of 99.9% gold mud

[0042] Add 2000g of gold-plated waste (gold content 5g detected by instrument) to the gold removal solution and stir for 1 hour. Keep the temperature at 50℃, let it stand and filter out the gold-containing solution. Add 20g of zinc powder and stir continuously at 50℃ for 2 hours. Filter out the solid gold and add it to a solution of 30g of concentrated nitric acid and 10g of concentrated hydrochloric acid in a mass ratio of 3:1. Dissolve it fully and then add 50g of 30% sodium bisulfite solution and 50g of urea to the solution. Continue until the solution no longer produces solid precipitation. The reaction time is about 8 minutes to obtain gold mud. See the actual picture of gold mud. Figure 1 The gold mud was then washed three times with hot pure water and then boiled and evaporated with 20% ammonia water. The gold mud weighed 4.85 grams and the gold content was measured to be more than 99.9%, with a gold reduction rate of 96.8%.

[0043] (3) Preparation of potassium gold cyanide

[0044] Place the gold mud in a 500ml glass container reactor, add 20ml of 5% potassium cyanide aqueous solution and 10ml of 3% hydrogen peroxide aqueous solution until the liquid level covers the gold mud, stir the solution at 50°C, and then titrate 90 drops of 5% potassium cyanide and 3% hydrogen peroxide continuously per minute, while injecting 1L of oxygen into the reaction system per minute. After the gold mud is completely dissolved, the reaction time is about 2 hours, and rotary evaporation crystallization is performed to produce high-purity potassium cyanide gold solid powder weighing 7g with a content of 99.9%. See the actual picture. Figure 2 .

[0045] (4) Yield and purity

[0046] According to the gold content of 5g of gold-plated waste, in principle, 7.3g of potassium gold cyanide can be obtained, and 7g of potassium gold cyanide is actually obtained. The yield rate of gold conversion into potassium gold cyanide is 7 / 7.35=95.2%, and the purity of potassium gold cyanide powder is 99.9%.

[0047] Example 2:

[0048] (1) Preparation of gold removal solution

[0049] Add 50g of gold removal powder and 30ml of hydrogen peroxide into 200ml of deionized water, and heat the mixed solution to 80℃ and stir for 30 minutes.

[0050] (2) Preparation of 99.9% gold mud

[0051] Add 2000g of gold-plated waste (5g of gold content detected by instrument) to the gold stripping solution and stir for 2 hours. Maintain the temperature at 70°C, let it stand and filter out the gold-containing solution. Add 15g of zinc powder, stir continuously at 60°C for 1 hour, filter out the solid, add 30g of nitric acid and 10g of hydrochloric acid in a mass ratio of 3:1, dissolve it fully, and then add 50g of 30% sodium bisulfite solution and 50g of urea to the solution until the solution stops producing solid precipitation, about 8 minutes, to obtain gold mud. Then wash the gold mud with hot pure water 3 times, and then boil and evaporate it with 20% ammonia water. The gold mud weighs 4.76g, the gold content is more than 99.9%, and the gold reduction rate is 95.2%.

[0052] (3) Preparation of potassium gold cyanide

[0053] The gold mud was placed in a 500ml glass container reactor, and 30ml of a 4% potassium cyanide aqueous solution and 20ml of a 3% hydrogen peroxide aqueous solution were added so that the liquid level covered the gold mud. The solution was stirred at 50°C and continuously titrated with 90 drops of 4% potassium cyanide and 3% hydrogen peroxide per minute. At the same time, 1L of oxygen was introduced into the reaction system per minute. After the gold mud was completely dissolved, the reaction time was calculated to be about 2 hours. Rotary evaporation and crystallization were performed to produce 6.97 grams of high-purity potassium cyanide gold solid powder with a measured content of 99.9%.

[0054] (4) Yield and purity

[0055] The yield rate of gold converted into potassium gold cyanide is 6.97 / 7.35=94.8%, and the purity of potassium gold cyanide powder is 99.9%.

[0056] Example 3:

[0057] (1) Preparation of gold removal solution

[0058] Add 100g of gold removal powder and 35ml of hydrogen peroxide to 200ml of deionized water, and heat the mixed solution to 70°C and stir for 60 minutes.

[0059] (2) Preparation of 99.9% gold mud

[0060] Add 2000g of gold-plated waste (5g of gold content detected by instrument) to the gold stripping solution and stir for 1 hour. Maintain the temperature at 65°C, let it stand and filter out the gold-containing solution. Add 15g of zinc powder, stir continuously at 65°C for 1 hour, filter out the solid, add 30g of nitric acid and 10g of hydrochloric acid in a mass ratio of 3:1, dissolve it fully, and then add 50g of 30% sodium bisulfite solution and 50g of urea to the solution until the solution stops producing solid precipitation, about 7 minutes, to obtain gold mud. Then wash the gold mud with hot pure water 3 times, and then boil and evaporate it with 20% ammonia water. The gold mud weighs 4.83 grams, the gold content is more than 99.9%, and the gold reduction rate is 96.6%.

[0061] (3) Preparation of potassium gold cyanide

[0062] The gold mud was placed in a 500ml glass container reactor, and 30ml of a 6% potassium cyanide aqueous solution and 10ml of a 3% hydrogen peroxide aqueous solution were added so that the liquid level covered the gold mud. The solution was stirred at 50°C and continuously titrated with 6% potassium cyanide and 3% hydrogen peroxide at 100 drops per minute. At the same time, 1L of oxygen was introduced into the reaction system per minute. After the gold mud was completely dissolved, the reaction time was calculated to be about 2 hours. Rotary evaporation and crystallization were performed to produce 7.08 grams of high-purity potassium gold cyanide solid powder with a measured content of 99.9%.

[0063] (4) Yield and purity

[0064] The yield rate of gold converted into potassium gold cyanide is 7.08 / 7.35=96.3%, and the purity of potassium gold cyanide powder is 99.9%.

[0065] Comparative Example:

[0066] Based on the method of Example 1, some process parameters, ratios and other factors were adjusted as a comparative example, and the gold reduction rate and reduction time, the potassium gold cyanide yield and reaction time were statistically analyzed, as shown in Table 1 below;

[0067] Comparative Example 1: Based on Example 1, urea was removed and its dosage was supplemented with 30% sodium bisulfite;

[0068] Comparative Example 2: The concentration of potassium cyanide aqueous solution is 2%, and the concentration of hydrogen peroxide is 1%;

[0069] Comparative Example 3: The concentration of potassium cyanide aqueous solution is 10%, and the concentration of hydrogen peroxide is 5%;

[0070] Comparative Example 4: The potassium cyanide reaction method is to directly add an excess of 5% potassium cyanide aqueous solution and 3% hydrogen peroxide residual gold mud to stir and react without oxygen, with a volume ratio of 3:1;

[0071] Table 1

[0072]

[0073] According to the results in Table 1 above, it can be seen that in Comparative Example 1, urea was not added, which prolonged the reduction time of the gold mud and had a slight impact on the reduction rate. In Comparative Example 2, after reducing the concentrations of potassium cyanide and hydrogen peroxide, not only the reaction time of potassium gold cyanide was prolonged, but also the product yield was significantly affected. In Comparative Example 3, after increasing the concentrations of potassium cyanide and hydrogen peroxide, the chemical reaction rate was significantly increased, but the main reaction of converting to potassium gold cyanide was significantly reduced, resulting in a very significant decrease in the yield of potassium gold cyanide. In Comparative Example 4, by adding excess potassium cyanide and hydrogen peroxide, the chemical reaction was basically unable to proceed under the condition of no oxygen.

[0074] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for synthesizing potassium gold cyanide from gold-plated waste, characterized in that: include: Gold-plated waste is added to the gold stripping solution for reaction, the gold-containing solution is filtered out, and then solid gold is obtained through a replacement reaction; The solid gold is dissolved in a mixed acid solution of hydrochloric acid and nitric acid, and then a combined reducing agent is added to carry out a reduction reaction until no solid precipitate is produced, and the solid precipitate is separated to form gold mud; the combined reducing agent includes urea and sodium bisulfite; The gold mud is reacted with potassium cyanide and hydrogen peroxide. First, part of the potassium cyanide and hydrogen peroxide is added until the liquid level covers the gold mud. Then, potassium cyanide and hydrogen peroxide are added dropwise respectively and stirred to react until the gold mud is completely dissolved. The dropping speed is 90-120 drops / minute. At the same time, oxygen is introduced into the reaction system. After the reaction is complete, potassium cyanide is evaporated and crystallized to obtain potassium cyanide.

2. The method according to claim 1, characterized in that The gold withdrawal solution comprises gold withdrawal powder, hydrogen peroxide and water.

3. The method according to claim 2, characterized in that The gold withdrawal solution includes 50-150g of gold withdrawal powder, 20-50mL of hydrogen peroxide and 100-200mL of water.

4. The method according to claim 1, wherein The method of obtaining solid gold by substitution reaction is to use a metal element with higher activity than gold to perform substitution reaction to obtain solid gold.

5. The method according to claim 4, characterized in that The metal element having a higher activity than gold includes zinc.

6. The method according to claim 1, wherein The mass ratio of urea to sodium bisulfite in the combined reducing agent is (20-150):(6-45).

7. The method according to claim 1, characterized in that The concentration of the potassium cyanide is 2-5%, and the concentration of the hydrogen peroxide is 3%.

8. The method according to claim 1, characterized in that Before the gold mud reacts with potassium cyanide and hydrogen peroxide, the following steps are also included: Wash the gold mud with hot pure water, then boil it with ammonia water, filter and dry it.

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