Preparation method of sodium gold sulfite solution and sodium gold sulfite solution

Abstract

The invention provides a preparation method of a sodium gold sulfite solution and the sodium gold sulfite solution, and relates to the technical field of precious metal compound preparation. The preparation method of the sodium gold sulfite solution comprises the following steps: reacting a HAuCl4 solution with sulfide under an acidic condition, precipitating to obtain Au2S3, adding the Au2S3 into hydrogen peroxide, reacting under the acidic condition to obtain a yellow transparent liquid, and reacting the yellow transparent liquid with a sodium sulfite solution to obtain the sodium gold sulfite solution. The sodium gold sulfite solution obtained by the preparation method disclosed by the invention is low in chloride ion content and high in yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of precious metal compounds, and relates to a preparation method of a sodium gold sulfite solution and a sodium gold sulfite solution. Background Art

[0002] The gold plating layer has excellent properties such as strong discoloration resistance, corrosion resistance, wear resistance, low contact resistance, and good solderability, and is widely used. Preparing the gold plating layer by a cyanide-free gold plating process can avoid the use of highly toxic cyanides and other problems. At present, sodium gold sulfite is relatively maturely applied in the cyanide-free gold plating process, and the preparation process and product quality of sodium gold sulfite have an important impact on the quality of the cyanide-free gold plating solution and the coating.

[0003] The prior art one adopts the direct reduction method of chloroauric acid, and prepares sodium gold sulfite by dissolving gold in aqua regia - adjusting pH - complexing with sodium sulfite. This method has a low yield, and at the same time contains a large amount of chloride ions, and the chloride ions are likely to cause corrosion of metal parts such as the tank body, hanging tools, and workpieces in subsequent electroplating.

[0004] The prior art two adopts the method of gold rolling - cleaning gold blocks - dissolving gold - removing nitrate - alkalizing - cleaning - complexation reaction - concentration and crystallization. By controlling the pH, the intermediate product Au(OH)3 precipitate is prepared, and the chloride ions in the product are removed by washing with deionized water. Although this process method has solid-liquid separation and can remove chloride ions, since gold hydroxide is an amphoteric substance, there is a problem of low yield, and the pH needs to be precisely controlled multiple times in the intermediate process, which brings a high difficulty to the process.

[0005] The prior art three adopts the method of dissolving gold in aqua regia - adjusting the alkali with ammonia water - precipitating auric acid - washing chloride ions - complexing with sodium sulfite to prepare sodium gold sulfite. Although this process can remove chloride ions, auric acid, as an explosive trivalent gold salt, has a great potential safety hazard in the production and manufacturing process.

[0006] The prior art one: Chinese Patent CN113046800A.

[0007] The prior art two: Chinese Patent CN105568269A.

[0008] The prior art three: Chinese Patent CN114164465A. Summary of the Invention

[0009] In order to solve the above technical problems and develop a safer, more efficient and lower chloride ion concentration sodium gold sulfite preparation method, the present invention provides a preparation method of a sodium gold sulfite solution and a sodium gold sulfite solution.

[0010] The technical solution of the present invention is as follows:

[0011] A method for preparing a sodium gold sulfite solution, comprising the following steps:

[0012] S1. Adjust the pH of the HAuCl4 solution to 4 - 6, add a sulfide, and the obtained precipitate is filtered and washed to obtain Au2S3;

[0013] S2. Add the Au2S3 obtained in step S1 to hydrogen peroxide, and at the same time control the pH of the reaction system to be 4 - 6 to obtain a yellow transparent liquid;

[0014] S3. Add the yellow transparent liquid obtained in step S2 to a sodium sulfite solution, adjust the pH of the reaction solution to 8 - 10 to obtain a colorless transparent liquid, which is the sodium gold sulfite solution.

[0015] Preferably, the concentration of the HAuCl4 solution in step S1 is 50 - 200 g / L.

[0016] Preferably, the sulfide in step S1 is selected from inorganic sulfides, preferably sodium sulfide, potassium sulfide or ammonium sulfide.

[0017] Preferably, the molar ratio of HAuCl4 to the sulfide in the HAuCl4 solution in step S1 is 1:1.5 - 3.

[0018] Preferably, the washing in step S1 is carried out with deionized water at 50 - 90 °C until the washing filtrate is detected without chloride ions by a 0.1 mol / L silver nitrate solution.

[0019] Preferably, the concentration of the hydrogen peroxide in step S2 is 10 - 30 wt%, and the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide is 1:12 - 18.

[0020] Preferably, controlling the pH of the reaction system to be 4 - 6 in step S2 is to add one of sulfuric acid, phosphoric acid, acetic acid and nitric acid.

[0021] Preferably, the molar ratio of Au in the yellow transparent liquid to sodium sulfite in the sodium sulfite solution in step S3 is 1:3 - 7.

[0022] Preferably, adjusting the pH of the reaction solution to 8 - 10 in step S3 is to use one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate and ammonia water.

[0023] A sodium gold sulfite solution is obtained by the preparation method of the sodium gold sulfite solution described in any one of the above technical solutions.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention uses sulfide for gold precipitation followed by washing, which can effectively remove a large amount of chloride ions introduced during the gold dissolution process, so that the chloride ion content in the final product of sodium gold sulfite solution does not exceed 100 ppm.

[0026] (2) The present invention uses sulfide to precipitate gold from HAuCl4 to obtain gold sulfide precipitate. The solubility of gold sulfide in water is extremely low, and it is insoluble in hydrochloric acid, sulfuric acid, and / or dilute nitric acid. Therefore, the yield of gold sulfide is close to 100%, ensuring a high yield (>95%) of the final product of sodium gold sulfite.

[0027] (3) The present invention dissolves gold sulfide with hydrogen peroxide to avoid introducing other impurities. Through the complexation of Au 3+ solution and sodium sulfite solution, since it is a liquid-liquid reaction, the complexation reaction is fast, thus achieving the preparation of sodium gold sulfite with a short process and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart for preparing sodium gold sulfite solution in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0029] The technical solutions of the present invention are further described and illustrated through the following specific embodiments. On the one hand, the present invention provides a method for preparing sodium gold sulfite solution, including the following steps:

[0030] S1. Adjust the pH of the HAuCl4 solution to 4 - 6, add sulfide, and the obtained precipitate is filtered and washed to obtain Au2S3;

[0031] S2. Add the Au2S3 obtained in step S1 to hydrogen peroxide, and at the same time control the pH of the reaction system to 4 - 6 to obtain a yellow transparent liquid;

[0032] S3. Add the yellow transparent liquid obtained in step S2 to sodium sulfite solution, and adjust the pH of the reaction solution to 8 - 10 to obtain a colorless transparent liquid, which is the sodium gold sulfite solution.

[0033] In order to reduce the chloride ion content in the sodium gold sulfite solution, the present invention uses sulfide to react with the HAuCl4 solution to form Au2S3 precipitate. Au2S3 has a very low solubility product constant (about 1.6×10 at 25℃) -73) After being washed with water multiple times to remove chloride ions and other impurities, a high-yield Au2S3 precipitate can be obtained. Then, under acidic conditions (such as weakly acidic), the Au2S3 precipitate reacts with hydrogen peroxide to redissolve Au in the solution, and after reacting with sodium sulfite, a sodium gold sulfite solution is obtained. In the present invention, since chloride ions are removed by washing with water multiple times in the step of obtaining the Au2S3 precipitate, the chloride ion content in the obtained sodium gold sulfite solution can be as low as 100 ppm or less, and the direct yield of sodium gold sulfite is high, reaching more than 95%.

[0034] In some embodiments, the concentration of the HAuCl4 solution in step S1 is 50 - 200 g / L. In the present invention, there is no particular limitation on the method for obtaining the HAuCl4 solution. It can be directly purchased from the market or prepared by existing technical methods, such as dissolving Au in aqua regia at 60 - 90 °C. For the concentration of the HAuCl4 solution, specifically, it can be any value among 50 g / L, 60 g / L, 80 g / L, 100 g / L, 120 g / L, 140 g / L, 150 g / L, 160 g / L, 180 g / L, 200 g / L, etc. Since the pH of the HAuCl4 solution is very low, in step S1, the pH is adjusted to 4 - 6 by using an alkali to adjust the HAuCl4 solution. For example, the alkali can be sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, etc. It can be directly in the form of a solid alkali or an aqueous solution of the alkali, such as an aqueous solution of sodium carbonate or an aqueous solution of sodium hydroxide. Preferably, an aqueous solution of the alkali is used to avoid violent heat release causing partial conversion of HAuCl4 to gold oxide. Of course, when using a solid alkali, it can be added in small amounts in multiple batches.

[0035] In some embodiments, the sulfide in step S1 is selected from inorganic sulfides, preferably sodium sulfide, potassium sulfide, or ammonium sulfide, and more preferably sodium sulfide. In the present invention, an inorganic sulfide (sulfide salt) is used to react with the HAuCl4 solution to form an Au2S3 precipitate with a very low solubility product parameter, which is not only beneficial for the complete precipitation of Au and the improvement of the Au recovery rate, and ultimately realizes a high yield (>95%) of the gold sulfite solution, but also beneficial for multiple washing of the Au2S3 precipitate with deionized water to remove chlorine and reduce the loss of Au. In the present invention, the sulfide can be directly added in solid form or in the form of an aqueous solution (such as a 5 - 20 wt% aqueous solution of sodium sulfide), without any particular limitation.

[0036] In some embodiments, the molar ratio of HAuCl4 to the sulfide in the HAuCl4 solution in step S1 is 1:1.5 - 3. For the reaction of HAuCl4 and the sulfide (taking sodium sulfide as an example), as shown in the following formula (1),

[0037] 2HAuCl4 + 3Na2S → 2Au2S3↓ + 6NaCl + 2HCl (1)

[0038] Therefore, for obtaining the Au2S3 precipitate and completely converting HAuCl4 into the Au2S3 precipitate, theoretically 1 mol of Au requires 1.5 mol of S. Thus, in order to convert Au in the HAuCl4 solution into the Au2S3 precipitate as much as possible, the molar ratio of HAuCl4 to the sulfide is not less than 1:1.5. For example, the molar ratio can be any value among 1:1.5, 1:1.7, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.6, 1:2.8, 1:3, etc.

[0039] In some embodiments, the cleaning in step S1 is performed using deionized water at 50 - 90°C until no chloride ions can be detected in the washing filtrate by a 0.1 mol / L silver nitrate solution. Cleaning the Au2S3 precipitate with deionized water at a temperature of 50 - 90°C can more effectively remove impurities in the Au2S3 precipitate, including chloride ions, and reduce the number of cleaning times. Moreover, due to the very low solubility product parameter of the Au2S3 precipitate, very little Au is eluted, reducing or avoiding the loss of Au. The washing filtrate is detected with a silver nitrate solution. When no silver chloride precipitate is produced, it can be determined that the chloride ions contained in the Au2S3 precipitate are very few, and the washing operation can end. In the present invention, the washed Au2S3 precipitate can be directly transferred to step S2, or can be transferred to step S2 after drying.

[0040] In some embodiments, the concentration of hydrogen peroxide in step S2 is 10 - 30 wt%, and the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide is 1:12 - 18. The present invention utilizes the strong oxidizing property of hydrogen peroxide, which can directly react with the Au2S3 precipitate that has been washed to remove chlorine under acidic conditions to dissolve the Au in the Au2S3 precipitate into the aqueous solution again, and using hydrogen peroxide does not introduce other impurities. The reaction process is shown in the following formula (2),

[0041] Au2S3 + 12H2O2 → 2Au 3+ + 3SO4 2- + 12H2O (2)

[0042] For example, the concentration of hydrogen peroxide refers to the content of H2O2 in hydrogen peroxide, which can be any value among 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 27wt%, 30wt%, etc. The excess of H2O2 in hydrogen peroxide relative to Au2S3 helps the precipitation of Au2S3 to react completely and dissolve in water. For example, the molar ratio of Au2S3 to H2O2 in hydrogen peroxide can be any value among 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, etc.

[0043] In some embodiments, in step S2, controlling the pH of the reaction system to be 4 - 6 is to add one of sulfuric acid, phosphoric acid, acetic acid, and nitric acid, such as dilute sulfuric acid, dilute phosphoric acid, and dilute nitric acid. Further, in step S2, sulfuric acid is used to control the pH of the reaction system to be 4 - 6, and the concentration of sulfuric acid can be 0.1 - 2 mol / L.

[0044] In some embodiments, in step S3, the molar ratio of Au in the yellow transparent liquid to sodium sulfite in the sodium sulfite solution is 1:3 - 7. For example, the molar ratio of Au in the yellow transparent liquid to sodium sulfite in the sodium sulfite solution can be any value among 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, etc.

[0045] In some embodiments, in step S3, adjusting the pH of the reaction solution to be 8 - 10 is to use one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, and ammonia water. When using sodium hydroxide, sodium carbonate, potassium hydroxide, or potassium carbonate, aqueous solutions of these alkalis can be used, such as aqueous sodium hydroxide solution, aqueous sodium carbonate solution, etc., such as an aqueous sodium carbonate solution or an aqueous sodium hydroxide solution with a concentration of 5 - 20wt%.

[0046] On the other hand, the present invention also provides a sodium gold sulfite solution, which is prepared by the preparation method of the sodium gold sulfite solution described in any one of the above technical solutions. The concentration of the sodium gold sulfite solution obtained by the present invention is not particularly limited. For example, it can be 50 ± 10 g / L. The content of chloride ions in the sodium gold sulfite solution is very low, which can be as low as 100 ppm and below, and the safety problem of easy explosion caused by using gold fulminate is avoided. When the sodium gold sulfite solution is used for gold plating, it can significantly reduce or avoid the corrosion of the hanging tool, plating tank, etc. by chloride ions.

[0047] The technical solutions of the present invention will be further described and illustrated according to the following embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0048] Example 1

[0049] Refer to the appendix Figure 1Preparation process of sodium aurothiosulfate solution. Under the condition of 80 °C, high-purity gold is dissolved with aqua regia to prepare an HAuCl4 solution with an HAuCl4 concentration of 50 g / L. A 20 wt% NaOH solution is added to the HAuCl4 solution to adjust the pH to 4.5 - 5.0, and then sodium sulfide is continuously added (the molar ratio of Au to sodium sulfide is 1:1.5) to obtain Au2S3 precipitate. The Au2S3 precipitate is filtered and collected by suction filtration, and washed 5 times with deionized water at a temperature of 60 °C. No white precipitate appears when the filtrate of the 5th wash is dropped into 0.1 mol / L AgNO3.

[0050] The above Au2S3 precipitate is slowly added to 10 wt% hydrogen peroxide solution under stirring, and the molar ratio of Au2S3 to H2O2 in hydrogen peroxide is 1:12. During the addition of the Au2S3 precipitate, the pH of the solution is controlled at 4.5 - 5.0 with 1 mol / L dilute sulfuric acid, and stirred until the solution turns into a yellow transparent solution.

[0051] The above yellow transparent solution is slowly added to the stirring sodium sulfite solution, and the molar ratio of Au to sodium sulfite is 1:3. The pH of the reaction solution is controlled at 8.0 - 8.5 with 20 wt% NaOH solution. When the reaction solution changes from light yellow to colorless and transparent, a sodium aurothiosulfate solution is obtained, and the concentration of the sodium sulfite solution is 50 g / L. After testing, the yield of sodium aurothiosulfate in the sodium aurothiosulfate solution is 95.8%, and the chloride ion content in the sodium aurothiosulfate solution is 62 ppm.

[0052] Example 2

[0053] The difference between this example and Example 1 is that in Example 1, the molar ratio of Au to sodium sulfide is adjusted from 1:1.5 to 1:3. The remaining steps remain unchanged. After testing, the yield of sodium aurothiosulfate in the obtained sodium aurothiosulfate solution is 96.4%, and the chloride ion content in the sodium aurothiosulfate solution is 75 ppm.

[0054] Example 3

[0055] Under the condition of 60 °C, high-purity gold is dissolved with aqua regia to prepare an HAuCl4 solution with an HAuCl4 concentration of 90 g / L. A 10 wt% NaOH solution is added to the HAuCl4 solution to adjust the pH to 5.0 - 5.5, and then sodium sulfide is continuously added (the molar ratio of Au to sodium sulfide is 1:2) to obtain Au2S3 precipitate. The Au2S3 precipitate is filtered and collected, and washed 4 times with deionized water at a temperature of 60 °C. No white precipitate appears when the filtrate of the 4th wash is dropped into 0.1 mol / L AgNO3.

[0056] The above Au2S3 precipitate was slowly added to the stirred hydrogen peroxide solution with a concentration of 20 wt%, and the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide solution was 1:12. During the addition of the Au2S3 precipitate, the pH of the solution was controlled at 4.5 - 5.0 with 1 mol / L dilute sulfuric acid, and the solution was stirred until it turned into a yellow transparent solution.

[0057] The above yellow transparent solution was slowly added to the stirred sodium sulfite solution, and the molar ratio of Au to sodium sulfite was 1:5. The pH of the reaction solution was controlled at 8.0 - 8.5 with 10 wt% NaOH solution. When the reaction solution changed from light yellow to colorless and transparent, a sodium gold sulfite solution was obtained, and the concentration of the sodium sulfite solution was 45 g / L. After testing, the yield of sodium gold sulfite in the sodium gold sulfite solution was 97.1%, and the chloride ion content in the sodium gold sulfite solution was 81 ppm.

[0058] Example 4

[0059] The difference between this example and Example 3 is that in Example 3, the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide solution was adjusted from 1:12 to 1:18. The remaining steps remained unchanged. After testing, the yield of sodium gold sulfite in the obtained sodium gold sulfite solution was 97.4%, and the chloride ion content in the sodium gold sulfite solution was 66 ppm.

[0060] Example 5

[0061] Under the condition of 80 °C, high-purity gold was dissolved with aqua regia to prepare a HAuCl4 solution with a HAuCl4 concentration of 150 g / L. 10 wt% NaOH solution was added to the HAuCl4 solution to adjust the pH to 4.5 - 5.0, and sodium sulfide (the molar ratio of Au to sodium sulfide was 1:2.5) was continuously added to obtain an Au2S3 precipitate. The Au2S3 precipitate was filtered and collected, and washed 5 times with deionized water at a temperature of 50 °C. No white precipitate appeared when the filtrate of the 5th wash was dropped into 0.1 mol / L AgNO3.

[0062] The above Au2S3 precipitate was slowly added to the stirred hydrogen peroxide solution with a concentration of 30 wt%, and the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide solution was 1:10. During the addition of the Au2S3 precipitate, the pH of the solution was controlled at 4.5 - 5.0 with 1 mol / L dilute sulfuric acid, and the solution was stirred until it turned into a yellow transparent solution.

[0063] The above-mentioned yellow transparent solution was slowly added to the stirred sodium sulfite solution, with the molar ratio of Au to sodium sulfite being 1:7. The pH of the reaction solution was controlled at 9.0 - 9.5 with a 10 wt% NaOH solution. When the reaction solution changed from light yellow to colorless and transparent, a sodium gold sulfite solution was obtained, and the concentration of the sodium sulfite solution was 55 g / L. After testing, the yield of sodium gold sulfite in the sodium gold sulfite solution was 98.6%, and the chloride ion content in the sodium gold sulfite solution was 45 ppm.

[0064] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, which are only preferred embodiments of the present invention. The scope of implementation of the present invention cannot be defined thereby. That is, equivalent changes and modifications made according to the scope of the present invention patent and the content of the specification should still fall within the scope covered by the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sodium gold sulfite solution, characterized in that, It includes the following steps: S1. Adjust the pH of the HAuCl4 solution to 4 - 6, add a sulfide, and the obtained precipitate is filtered and washed to obtain Au2S3; S2. Add the Au2S3 obtained in step S1 to hydrogen peroxide, and at the same time control the pH of the reaction system to be 4 - 6 to obtain a yellow transparent liquid; S3. Add the yellow transparent liquid obtained in step S2 to a sodium sulfite solution, adjust the pH of the reaction solution to 8 - 10 to obtain a colorless transparent liquid, which is the sodium gold sulfite solution.

2. The preparation method of the sodium aurothiosulfate solution according to claim 1, characterized in that, In step S1, the concentration of the HAuCl4 solution is 50 - 200 g / L.

3. The preparation method of the sodium aurothiosulfate solution according to claim 1, characterized in that, In step S1, the sulfide is selected from inorganic sulfides, preferably sodium sulfide, potassium sulfide or ammonium sulfide.

4. The preparation method of the sodium gold sulfite solution according to claim 1, wherein In step S1, the molar ratio of HAuCl4 to the sulfide in the HAuCl4 solution is 1:1.5 - 3.

5. The preparation method of the sodium aurothiosulfate solution according to claim 1, wherein In step S1, the washing is carried out with deionized water at 50 - 90 °C until the washing filtrate is detected to have no chloride ions by a 0.1 mol / L silver nitrate solution.

6. The preparation method of the sodium aurothiosulfate solution according to claim 1, wherein, In step S2, the concentration of the hydrogen peroxide is 10 - 30 wt%, and the molar ratio of Au2S3 to H2O2 in the hydrogen peroxide is 1:12 - 18.

7. The preparation method of the sodium aurothiosulfate solution according to claim 1, wherein In step S2, controlling the pH of the reaction system to be 4 - 6 is achieved by adding one of sulfuric acid, phosphoric acid, acetic acid and nitric acid.

8. The preparation method of the sodium aurothiosulfate solution according to claim 1, characterized in that, In step S3, the molar ratio of Au in the yellow transparent liquid to sodium sulfite in the sodium sulfite solution is 1:3 - 7.

9. The preparation method of the sodium aurothiosulfate solution according to claim 1, wherein, In step S3, adjusting the pH of the reaction solution to 8 - 10 is achieved by using one of sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate and ammonia water.

10. A sodium gold sulfite solution, characterized in that, It is obtained by the preparation method of the sodium gold sulfite solution according to any one of claims 1 - 9.

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