A method for recovering gold sulfite salt directly from cyanide-free gold plating waste liquid

Abstract

The application discloses a method for recovering gold sulfite from cyanide-free gold plating waste liquid, and the stable gold sulfite solution is prepared through the steps of concentrating, filtering, anti-solvent precipitation and gold sulfite dissolving of the cyanide-free gold plating waste liquid. The cyanide-free gold plating waste liquid can be efficiently recovered by the method, and the gold sulfite for cyanide-free gold plating is directly obtained, a gold closed loop is formed, the gold turnover rate is accelerated, and the production cost is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of recycling and treating electro-gold plating waste liquid, and in particular to a method for directly recycling gold sulfite from cyanide-free gold plating waste liquid. Background Art

[0002] Common gold plating processes include cyanide-based gold plating and cyanide-free gold plating. Cyanide-based gold plating uses cyanide as a complexing agent, which has a large complexing constant and good plating solution stability. However, due to its high toxicity, cyanide poses numerous challenges, including operational safety, waste liquid disposal, and environmental protection. Furthermore, in microelectronics manufacturing, free cyanide in cyanide-based gold plating solutions can corrode photoresists, limiting their application. Cyanide-free gold plating systems effectively address these issues. Currently, the mainstream cyanide-free gold plating system is gold sulfite-based cyanide-free gold plating.

[0003] Compared to cyanide gold plating processes, cyanide-free gold plating solutions suffer from poor stability and a shorter service life. This is because as electroplating continues, sulfate and sulfite ions in the plating solution system accumulate, ultimately causing the plating solution to become ineffective. Efficiently treating cyanide-free gold plating wastewater has become one of the key issues that urgently need to be addressed in order to improve the cyanide-free gold plating system. Chinese patent application CN108374090A employs the addition of a complexing agent to break the complex and then uses hydrogen peroxide to recover the gold. Although this method can recover gold, it cannot produce a gold salt that can be directly used for electroplating. Chinese patent application CN113584539A first electrolyzes sulfite-free cyanide gold plating wastewater to obtain gold, then uses a complexing acidic cell electrolysis method to prepare gold chloride from the recovered gold. Finally, the gold chloride is converted into gold fulminate, which is then returned to the gold salt aqueous solution in the gold plating solution to form a cysteine ​​gold salt complex, thereby achieving a cyclic recycling of the wastewater. This method is cumbersome and inefficient; at the same time, it introduces explosive gold fulminate, which poses a significant safety hazard during the production process.

[0004] Currently, the electroplating of Au-Cu, Au-Sn, and Au-Ag alloys using gold sulfite systems is becoming a hot topic in the field of electronic electroplating. Traditional reduction methods for recycling these alloy electroplating wastewaters can result in the inclusion of metallic impurities such as Cu, Sn, and Ag in the resulting crude gold, increasing the difficulty of gold purification. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for directly recovering gold sulfite from cyanide-free gold plating waste liquid.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for directly recovering gold sulfite from cyanide-free gold plating waste liquid comprises the following steps:

[0008] (1) heating and concentrating the cyanide-free gold plating waste liquid; cooling the concentrated liquid to room temperature, filtering out the precipitated salt if any, and adjusting the pH of the filtered filtrate;

[0009] (2) adding an organic solvent to the filtrate obtained in step (1), precipitating a solid with an anti-solvent, and obtaining a gold sulfite solid after solid-liquid separation;

[0010] (3) dissolving gold sulfite solid in deionized water and adjusting the pH;

[0011] (4) adding an organic solvent to the solution obtained in step (3), precipitating a solid with an anti-solvent, and obtaining a gold sulfite solid after solid-liquid separation; and fully removing metal and non-metallic ion impurities carried by the gold sulfite;

[0012] (5) After performing steps (3)-(4) several times, the gold sulfite solid obtained in the last step is fully dried, and the dried gold sulfite is dissolved in deionized water to prepare a gold sulfite solution. A stabilizer is then added and the pH is adjusted to finally obtain a gold sulfite solution with stable performance.

[0013] Furthermore, in step (1), the heating and concentration temperature is 70° C.-95° C., and the gold concentration of the concentrated solution is 10 g / L-25 g / L.

[0014] Furthermore, in step (1), an acid or a base is used to adjust the pH of the filtrate to between 8 and 10; the base is one of sodium hydroxide, potassium hydroxide or ammonia water, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

[0015] Furthermore, in step (2) and step (4), the organic solvent is one of methanol, ethanol or isopropanol; and the volume ratio of the organic solvent to the filtrate or solution is 2:1-5:1.

[0016] Furthermore, in step (3), the amount of deionized water used is calculated based on a volume ratio of deionized water to the filtrate obtained in step (2) or the solution obtained in step (4) of 1:1-1:2; the pH of the solution is adjusted to between 8 and 10 with an acid or a base; the base is one of sodium hydroxide, potassium hydroxide or ammonia water, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

[0017] Furthermore, in step (5), steps (3) to (4) are performed 1 to 3 times.

[0018] Furthermore, in step (5), the drying method is natural air drying, freeze drying or vacuum oven low-temperature drying.

[0019] Furthermore, in step (5), the stabilizer is one of potassium pyrophosphate, sodium sulfite, sodium hexametaphosphate or ethanol; and the stabilizer is added according to a molar ratio of Au:stabilizer of 1:1-3:1.

[0020] Furthermore, in step (5), the pH of the gold sulfite solution is adjusted to 8.0-11.0 using an acid or a base, wherein the base is one of sodium hydroxide, potassium hydroxide or ammonia water, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

[0021] The beneficial effects of the present invention are:

[0022] (1) The method of the present invention uses concentrated waste liquid and precipitates it with an organic solvent such as ethanol, which can effectively remove the influence of potential metal impurities such as Cu, Sn, Ag, Fe, Ni, Cr, etc. in the waste liquid, and can also effectively remove Cl - , to obtain high-purity gold sulfite solid and solution.

[0023] (2) The method of the present invention directly and efficiently recovers gold sulfite, has few steps and high recovery efficiency, and avoids the tedious process of reducing crude gold through waste liquid, purifying crude gold, and then preparing gold sulfite in the traditional method.

[0024] (3) The method of the present invention has a short process, low energy consumption, and uses fewer reagents, especially avoiding the need to use strong reducing agents, hydrochloric acid, nitric acid and other reagents in the traditional route.

[0025] (4) The method of the present invention forms a gold closed loop for the entire gold plating system, so that the electroplating waste liquid can be directly used to collect gold salts, thereby accelerating the gold turnover rate and effectively reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Flowchart of the methods of various embodiments of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0028] Example 1

[0029] This embodiment provides a method for directly recovering gold sulfite from cyanide-free gold plating waste liquid, such as Figure 1 As shown, the following steps are included:

[0030] (1) Heat the gold electroplating wastewater from the gold-sodium cyanide-free system at 95°C and concentrate it to a gold concentration of approximately 15 g / L. Allow the concentrate to cool to room temperature. If salt precipitates, filter it out. Adjust the pH of the filtrate to 8.0 with sodium hydroxide solution.

[0031] (2) adding ethanol to the filtrate obtained in step (1) at a volume ratio of 5:1, using an anti-solvent to precipitate a solid, and obtaining sodium gold sulfite solid after solid-liquid separation.

[0032] (3) Dissolve the sodium gold sulfite solid obtained in step (2) in deionized water at a volume ratio of 1:1 between deionized water and filtrate, and adjust the pH of the solution to 8.0 with sodium hydroxide solution.

[0033] (4) adding an organic solvent to the solution obtained in step (3) again, precipitating a solid with an anti-solvent, and obtaining a solid of gold sulfite after solid-liquid separation. The metal and non-metallic ion impurities carried by the anti-solvent precipitated gold sodium sulfite are fully removed.

[0034] (5) The sodium gold sulfite solid obtained in step (4) was vacuum dried at 50° C. for 2 h. The dried sodium gold sulfite solid was dissolved in deionized water to prepare a sodium gold sulfite solution of a specified concentration. Sodium sulfite was added at a gold:sodium sulfite molar ratio of 2:1 and the pH of the solution was controlled to 9.0 by sodium hydroxide, thereby finally preparing a sodium gold sulfite solution with stable performance.

[0035] Example 2

[0036] This embodiment provides a method for directly recovering gold sulfite from cyanide-free gold plating waste liquid, such as Figure 1 As shown, the following steps are included:

[0037] (1) Heat the gold electroplating wastewater from the cyanide-free potassium sulfite gold system at 85°C and concentrate it to a gold concentration of about 10 g / L. After the concentrate cools to room temperature, if salt precipitates, filter it out and then adjust the pH of the filtrate to 9.0 with potassium hydroxide solution.

[0038] (2) adding methanol to the filtrate obtained in step (1) at a volume ratio of 2:1, using an anti-solvent to precipitate a solid, and obtaining potassium gold sulfite solid after solid-liquid separation.

[0039] (3) Dissolve the gold potassium sulfite solid in deionized water at a volume ratio of 1:1 deionized water to filtrate, and adjust the pH of the solution to 9.0 with potassium hydroxide solution.

[0040] (4) adding methanol to the solution obtained in step (3) at a volume ratio of 2:1, using an anti-solvent to precipitate a solid, and obtaining potassium gold sulfite solid after solid-liquid separation.

[0041] (5) After repeating steps (3)-(4) twice, the potassium gold sulfite solid obtained in the last step is naturally dried in the shade at room temperature for 24 hours. The dried potassium gold sulfite solid is dissolved in deionized water to prepare a potassium gold sulfite solution of a specified concentration. Potassium pyrophosphate is added at a gold:potassium pyrophosphate molar ratio of 3:1, and the pH of the solution is controlled to 11.0 by potassium hydroxide, thereby finally preparing a potassium gold sulfite solution with stable performance.

[0042] Example 3

[0043] This embodiment provides a method for directly recovering gold sulfite from cyanide-free gold plating waste liquid, such as Figure 1 As shown, the following steps are included:

[0044] (1) Heat the gold-plating wastewater from the gold-ammonium cyanide-free electroplating system at 70°C and concentrate it to a gold concentration of approximately 25 g / L. Allow the concentrate to cool to room temperature. If salt precipitates, filter it out. Adjust the pH of the filtrate to 10.0 with aqueous ammonia.

[0045] (2) adding isopropanol to the filtrate obtained in step (1) at a volume ratio of 3:1, using an anti-solvent to precipitate a solid, and obtaining a solid of ammonium gold sulfite after solid-liquid separation.

[0046] (3) Dissolve the ammonium gold sulfite obtained in step (2) in deionized water at a volume ratio of 1:2. Adjust the pH of the filtrate to 10.0 with aqueous ammonia.

[0047] (4) adding isopropanol to the solution obtained in step (3) in a volume ratio of isopropanol to solution of 3:1, precipitating a solid with an anti-solvent, and obtaining a gold ammonium sulfite solid after solid-liquid separation.

[0048] (5) After repeating steps (3)-(4) three times, the gold ammonium sulfite solid obtained in the last step was freeze-dried at -5°C for 24 hours. The dried gold ammonium sulfite solid was dissolved in deionized water to prepare a gold ammonium sulfite solution of a specified concentration. Sodium hexametaphosphate was added at a gold:sodium hexametaphosphate molar ratio of 1:1 and the pH of the solution was controlled to 8.0 by using aqueous ammonia to finally prepare a gold ammonium sulfite solution with stable performance.

[0049] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for directly recovering gold sulfite from cyanide-free gold plating waste liquid, characterized in that: The steps include: (1) Heat and concentrate the cyanide-free gold plating waste liquid; wait for the concentrated liquid to cool to room temperature, if salt is precipitated, filter out the precipitated salt, and adjust the pH of the filtrate obtained by filtration to between 8 and 10 with acid or alkali; (2) adding an organic solvent to the filtrate obtained in step (1), precipitating a solid with an anti-solvent, and obtaining a gold sulfite solid after solid-liquid separation; the organic solvent is one of methanol, ethanol or isopropanol; (3) dissolving the gold sulfite solid in deionized water and adjusting the pH of the solution to between 8 and 10 with an acid or base; (4) adding an organic solvent to the solution obtained in step (3), precipitating a solid with an anti-solvent, and obtaining a gold sulfite solid after solid-liquid separation; fully removing metal and non-metallic ion impurities carried by the gold sulfite; the organic solvent is one of methanol, ethanol or isopropanol; (5) After performing steps (3)-(4) several times, the gold sulfite solid obtained in the last step is fully dried, and the dried gold sulfite is dissolved in deionized water to prepare a gold sulfite solution, and then a stabilizer is added and the pH of the gold sulfite solution is adjusted to 8.0-11.0 with an acid or a base, thereby finally obtaining a gold sulfite solution with stable performance; The stabilizer is one of potassium pyrophosphate, sodium sulfite, sodium hexametaphosphate or ethanol.

2. The method according to claim 1, characterized in that In step (1), the heating and concentrating temperature is 70°C-95°C, and the gold concentration of the concentrated solution is 10g / L-25g / L.

3. The method according to claim 1, characterized in that In step (1), the base is one of sodium hydroxide, potassium hydroxide or ammonia, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

4. The method according to claim 1, wherein In step (2) and step (4), the volume ratio of the organic solvent to the filtrate or solution is 2:1-5:

1.

5. The method according to claim 1, wherein In step (3), the amount of deionized water used is calculated based on a volume ratio of deionized water to the filtrate obtained in step (2) or the solution obtained in step (4) of 1:1-1:2; the base is one of sodium hydroxide, potassium hydroxide or ammonia water, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

6. The method according to claim 1, characterized in that In step (5), follow steps (3) to (4) for 1 to 3 times.

7. The method according to claim 1, characterized in that In step (5), the drying method is natural air drying, freeze drying or vacuum oven low-temperature drying.

8. The method according to claim 1, characterized in that In step (5), the stabilizer is added according to a molar ratio of Au:stabilizer of 1:1-3:

1.

9. The method according to claim 1, characterized in that In step (5), the base is one of sodium hydroxide, potassium hydroxide or ammonia, and the acid is one of dilute sulfuric acid, dilute nitric acid or tartaric acid.

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