CN113046800A - Gold sodium sulfite electroplating solution and preparation method thereof - Google Patents
Gold sodium sulfite electroplating solution and preparation method thereof Download PDFInfo
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Abstract
The application discloses a gold sodium sulfite electroplating solution and a preparation method thereof, which comprises the following steps: adding gold into aqua regia, and dissolving at 90-100 deg.C for 1-3 hr; continuing to keep the temperature at 90-100 ℃ for 3-5h, concentrating the chloroauric acid into syrup, and adding concentrated hydrochloric acid to the concentrated chloroauric acid for multiple times to remove nitrate; putting the solution with constant volume in an ice-water bath, dripping saturated sodium hydroxide into the chloroauric acid solution while stirring under the condition of the ice-water bath, and adjusting the pH value to 6-7; adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution while stirring, and continuously stirring for 1-1.5 h; and filtering the solution after the solution is faded from yellow to colorless and transparent to obtain the gold sodium sulfite electroplating solution. According to the method, ammonia water neutralization and chloride ion washing are not required, so that the equipment investment is reduced, the production environment is improved, the explosion hazard is avoided, and the working strength is greatly reduced; and the gold sodium sulfite has high conversion rate, high purity and good electroplating effect.
Description
Technical Field
The application relates to the field of cyanide-free electroplating solution, in particular to gold sodium sulfite electroplating solution and a preparation method thereof.
Background
Compared with the traditional casting technology, the gold electroforming technology has the greatest characteristics that less gold material can be used, lighter, thinner and more precise products can be designed and manufactured, and the ornaments are attractive in appearance, large in volume and light in weight, and are more easily accepted by common consumer groups in price.
At present, the gold plating process commonly used at home and abroad comprises two main types of cyanide gold plating process and cyanide-free gold plating process. In the cyanide gold plating process, cyanide is used as a complexing agent, so that the quality of a plating layer and the stability of a plating solution can be guaranteed, but the cyanide has high toxicity, so that a plurality of problems are brought to the operation safety, the waste liquid treatment, the environmental protection and the like, and the application is greatly limited. The existing cyanide-free gold plating process mainly comprises sulfite gold plating, halide gold plating, thiosulfate gold plating, thiomalic acid gold plating and the like, and the mature cyanide-free gold plating process is sulfite gold plating.
The main process for producing the traditional gold sodium sulfite electroplating solution comprises the following steps: dissolving/removing nitrate from gold; ammonia water neutralization; thirdly, washing chloride ions; and fourthly, neutralizing by sodium sulfite. The above preparation process has the following problems: the ammonia water has strong volatility and high requirements on the sealing property and the air draft system of equipment; gold trichloride formed after gold dissolution can react with ammonia water to generate gold fulminate, the gold fulminate needs to be washed by hot water for more than 8 times to remove chloride ions in the gold fulminate, and then the gold fulminate is dried by adopting a suction filtration mode, the suction filtration speed in the suction filtration process is slower and slower, the production efficiency of sodium gold sulfite is seriously influenced, the gold fulminate cannot be thoroughly drained, and otherwise, the gold fulminate is easy to explode.
Disclosure of Invention
The application provides a sodium gold sulfite electroplating solution and a preparation method thereof, aiming at the problems that the existing sodium gold sulfite electroplating solution production process is dangerous and the production efficiency is low.
In a first aspect, the present application provides a method for preparing a gold sodium sulfite electroplating solution, which is implemented by the following technical scheme.
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding gold into aqua regia, and dissolving at 90-100 deg.C for 1-3 hr to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 90-100 ℃ for 3-5h, concentrating the chloroauric acid into syrup, and adding concentrated hydrochloric acid into the concentrated chloroauric acid for multiple times to remove nitric oxide yellow smoke generated by nitric acid;
s3, constant volume: fixing the volume of the solution obtained in the step S2 by using hydrochloric acid;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 0-15 ℃;
s5, adjusting pH: under the condition of ice water bath, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, and adjusting the pH to 6-7;
s6, sodium sulfite neutralization: adding the chloroauric acid solution after the pH is adjusted into a 120g/L sodium sulfite solution of 115-one while stirring, and continuing stirring for 1-1.5h after the dropwise addition is finished; the mass ratio of the sodium sulfite to the gold is (3-4) to 1;
s7, filtering: and (5) when the solution in the step (S6) fades from yellow to colorless and transparent, filtering, and adding pure water to a constant volume to obtain the gold sodium sulfite electroplating solution.
By adopting the technical scheme, gold is dissolved in aqua regia to obtain chloroauric acid, then nitrate is removed, pH is adjusted to 6-7 at a lower temperature, sodium sulfite is adopted for complexing, high-purity sodium gold sulfite can be obtained after filtering, the whole sodium gold sulfite preparation process is simple, the safety coefficient is high, explosion danger cannot exist, and the conversion rate of the sodium gold sulfite is high.
Specifically, 99.99% of sponge gold is used as a raw material of the electroplating solution, the sponge gold can reach the standard of national standard gold I, and is a common gold raw material, and the structure of the sponge gold is fluffy and can be better dissolved in aqua regia to form chloroauric acid; adding concentrated hydrochloric acid into the chloroauric acid with gold dissolved for nitrate removal treatment to remove nitrate radicals in the system, so as to ensure smooth proceeding of subsequent reaction; the innovation point of the application lies in that the solution after the constant volume is cooled by adopting an ice water bath, and then the pH value is adjusted at a low temperature, and the aim of the operation is to reduce the incidence rate of gold hydrolysis and sedimentation, thereby improving the utilization rate of gold. In addition, the acid-base neutralization reaction belongs to exothermic reaction, and is violent exothermic reaction, and the stability of gold in the reaction system can be influenced by the rapid temperature rise, so that the sedimentation of gold is accelerated. The method adopts NaOH to adjust the pH value of the solution to 6-7, and gold hydroxide cannot be formed in the system because the gold hydroxide is unstable and easy to dehydrate and convert into gold oxide, and then is decomposed into simple substance gold, so that the gold utilization rate is low. Moreover, the conversion rate of the gold sodium sulfite complexed by the gold hydroxide and the sodium sulfite is not high, and the utilization rate of gold is low. Therefore, the pH value of the reaction system is controlled to be 6-7 before the complexing with the sodium sulfite, so that the conversion rate of gold can be better improved. This application will adjust solution after pH and sodium sulfite and carry out the complex to the quantity of strict control sodium sulfite, thereby with gold furthest's among the reaction system conversion gold sodium sulfite, adopt filterable mode to detach the impurity in the system at last, improve the purity of gold sodium sulfite.
In summary, the application improves the conventional preparation method of sodium sulfite gold sodium, improves the conversion rate of the sodium sulfite gold sodium, improves the utilization rate of gold, and can stably store the prepared gold sodium sulfite electroplating solution for more than two weeks without precipitation, wherein the gold content of the prepared gold sodium sulfite electroplating solution can reach 99.995%. In addition, the whole preparation method does not use ammonia water, does not generate unpleasant volatile gas, improves the working environment, does not form fulminate gold, avoids the danger of explosion, does not need to wash chloride ions for many times, greatly reduces the working strength and improves the production efficiency.
Optionally, in step S1, the mass-to-volume ratio of gold to aqua regia is 1 (3-5).
Through adopting above-mentioned technical scheme, the quality volume ratio of this application strict control gold and aqua regia is favorable to making the gold dissolve in the aqua regia completely, establishes the basis for follow-up operation step, improves the conversion rate of gold.
Optionally, in step S2, the concentrated hydrochloric acid is 36% concentrated hydrochloric acid, and the number of times of addition is 4-5 times.
By adopting the technical scheme, 36% concentrated hydrochloric acid is added into the reaction system for 4-5 times, so that nitrate can be converted into nitrogen oxide to the maximum extent and removed from the reaction system, and adverse effects of the nitrate on subsequent reactions are avoided.
Optionally, in step S3, the solution obtained in step S2 is made to a constant volume with 12% hydrochloric acid.
By adopting the technical scheme, 12% of hydrochloric acid is supplemented into the system to perform constant volume on the reaction system, and the concentration of gold in the system can be controlled, so that the completeness and the conversion rate of subsequent complex reaction are improved.
Optionally, in step S4, the temperature of the chloroauric acid solution is controlled at 10-15 ℃.
By adopting the technical scheme, although the chloroauric acid can be operated in the pH adjusting range of 0-15 ℃, the temperature of the chloroauric acid is further controlled to be 10-15 ℃, on one hand, the occurrence rate of gold hydrolytic precipitation can be reduced at the temperature, on the other hand, the operation time of the whole method can be shortened, and the production efficiency is improved.
Optionally, in step S5, the stirring speed is 30-50 rpm/min; the dropping speed of the saturated sodium hydroxide is as follows: 3-5 mL/min.
By adopting the technical scheme, the application further limits the dropping speed and the stirring rotating speed of the saturated sodium hydroxide, and the dropped NaOH can be uniformly dispersed in the system, so that the formation of local gold hydroxide is avoided, and the conversion rate of gold is improved.
Optionally, in step S6, the preparation method of the sodium sulfite solution is as follows: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare a sodium sulfite solution of 120g/L of 115-sodium sulfate, adding a saturated sodium hydroxide solution, adjusting the pH to 8, and dissolving for 10-20min at 50-60 ℃ under the condition of 20-40 rpm/min.
Through adopting above-mentioned technical scheme, this application is dissolved sodium sulfite in pure water and is adjusted pH to 8, and the configuration method is very simple, can make sodium sulfite quick more and even dissolve in pure water after the heating, shortens whole preparation time, improves production efficiency.
Optionally, in step S6, the stirring speed is 30-50 rpm/min; the dropping speed of the chloroauric acid solution is 10-15 mL/min.
Through adopting above-mentioned technical scheme, the dropwise add speed and the stirring rotational speed of chloroauric acid dropwise add in sodium sulfite are further injectd to this application, can make more complete of chloroauric acid and sodium sulfite reaction, improve the conversion rate of gold sodium sulfite.
Optionally, in step S7, filtering is performed with tetrafluoro filter paper with pore size of 0.22 um.
Through adopting above-mentioned technical scheme, this application adopts 0.22um aperture tetrafluoro filter paper to filter the gold sodium sulfite that the preparation obtained, can effectually get rid of the impurity in the solution, improves the purity of gold sodium sulfite plating solution.
In a second aspect, the present application provides a gold sodium sulfite electroplating solution, which is realized by the following technical scheme.
The gold sodium sulfite electroplating solution prepared by the preparation method of the gold sodium sulfite electroplating solution.
By adopting the technical scheme, the gold content in the gold sodium sulfite electroplating solution prepared by the method can reach 99.995%, and the gold sodium sulfite electroplating solution can be stably stored for more than two weeks, does not precipitate, has a good electroplating effect and can bear a wide range of current.
In summary, the present application has the following beneficial effects:
1. according to the preparation method of the gold sodium sulfite electroplating solution, two steps of ammonia water neutralization and chloride ion washing are not needed, so that the equipment investment is effectively reduced, the production environment is improved, the explosion hazard is avoided, the working strength is greatly reduced, and the production period is shortened;
2. the method improves the conventional preparation method of the gold sodium sulfite electroplating solution, improves the conversion rate of the gold sodium sulfite, and improves the utilization rate of gold;
3. the gold content in the gold sodium sulfite electroplating solution can reach 99.995 percent, and the gold sodium sulfite electroplating solution can be stably stored for more than two weeks without precipitation.
Detailed Description
The present application will be described in further detail with reference to examples.
Example 1
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding 50g of 99.99% sponge gold into 150mL of aqua regia, and dissolving for 1h at 100 ℃ to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 100 ℃ for 3h, concentrating the chloroauric acid into syrup, and adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 5 times to remove nitrogen oxide yellow smoke generated by nitric acid;
s3, constant volume: adding 12% hydrochloric acid into the system in the step S2, and fixing the volume of the chloroauric acid to 500mL to ensure that the gold content is 100 g/L;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 0 ℃;
s5, adjusting pH: under the conditions of ice water bath and stirring speed of 30rpm/min, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, wherein the dropwise adding speed of the saturated sodium hydroxide is as follows: 3mL/min, and adjusting the pH value to 7;
s6, sodium sulfite neutralization: dropwise adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution at a speed of 15mL/min while stirring under the condition that the stirring speed is 30rpm/min, and continuously stirring for 1.5h after dropwise adding is finished;
the preparation method of the sodium sulfite solution comprises the following steps: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare a 115g/L sodium sulfite solution 1739mL, adding a saturated sodium hydroxide solution, adjusting the pH to 8, and dissolving for 10min at 50 ℃ under the condition of 40 rpm/min;
s7, filtering: and when the solution fades from yellow to colorless and transparent, filtering by using tetrafluoro filter paper with the aperture of 0.22um, and fixing the volume to 2500mL by using pure water to obtain 20g/L of gold sodium sulfite electroplating solution.
Example 2
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding 50g of 99.99% sponge gold into 250mL of aqua regia, and dissolving for 3h at 90 ℃ to obtain chloroauric acid;
s2, nitrate removal: keeping the temperature at 90 ℃ for 5 hours, concentrating the chloroauric acid into syrup, adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 4 times, and removing nitrogen oxide yellow smoke generated by nitric acid;
s3, constant volume: adding 12% hydrochloric acid into the system in the step S2, and fixing the volume of the chloroauric acid to 500mL to ensure that the gold content is 100 g/L;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 15 ℃;
s5, adjusting pH: under the conditions of ice water bath and stirring speed of 50rpm/min, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, wherein the dropwise adding speed of the saturated sodium hydroxide is as follows: 5mL/min, and adjusting the pH value to 6;
s6, sodium sulfite neutralization: dropwise adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution at the speed of 10mL/min while stirring under the condition that the stirring speed is 50rpm/min, and continuously stirring for 1h after dropwise adding is finished;
the preparation method of the sodium sulfite solution comprises the following steps: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare 1250mL of 120g/L sodium sulfite solution, adding saturated sodium hydroxide solution, adjusting the pH to 8, and dissolving for 20min at the temperature of 60 ℃ and the speed of 20 rpm/min;
s7, filtering: and when the solution fades from yellow to colorless and transparent, filtering by using tetrafluoro filter paper with the aperture of 0.22um, and fixing the volume to 2500mL by using pure water to obtain 20g/L of gold sodium sulfite electroplating solution.
Example 3
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding 50g of 99.99% sponge gold into 200mL of aqua regia, and dissolving at 95 ℃ for 2h to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 95 ℃ for 4h, concentrating the chloroauric acid into syrup, and adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 4 times to remove nitrogen oxide yellow smoke generated by nitric acid;
s3, constant volume: adding 12% hydrochloric acid into the system in the step S2, and fixing the volume of the chloroauric acid to 500mL to ensure that the gold content is 100 g/L;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 10 ℃;
s5, adjusting pH: under the conditions of ice water bath and stirring speed of 40rpm/min, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, wherein the dropwise adding speed of the saturated sodium hydroxide is as follows: 4mL/min, and adjusting the pH value to 6.5;
s6, sodium sulfite neutralization: dropwise adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution at the speed of 12mL/min while stirring under the condition that the stirring speed is 40rpm/min, and continuously stirring for 1.2h after dropwise adding is finished;
the preparation method of the sodium sulfite solution comprises the following steps: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare 1500mL of 120g/L sodium sulfite solution, adding saturated sodium hydroxide solution, adjusting the pH to 8, and dissolving for 15min at 55 ℃ and 30 rpm/min;
s7, filtering: and when the solution fades from yellow to colorless and transparent, filtering by using tetrafluoro filter paper with the aperture of 0.22um, and fixing the volume to 2500mL by using pure water to obtain 20g/L of gold sodium sulfite electroplating solution.
Example 4
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding 50g of 99.99% sponge gold into 180mL of aqua regia, and dissolving at 92 ℃ for 1.8h to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 92 ℃ for 4.5h, concentrating the chloroauric acid into syrup, and adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 5 times to remove nitrogen oxide yellow smoke generated by nitric acid;
s3, constant volume: adding 12% hydrochloric acid into the system in the step S2, and fixing the volume of the chloroauric acid to 500mL to ensure that the gold content is 100 g/L;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 8 ℃;
s5, adjusting pH: under the conditions of ice water bath and stirring speed of 40rpm/min, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, wherein the dropwise adding speed of the saturated sodium hydroxide is as follows: 4mL/min, and adjusting the pH value to 6.2;
s6, sodium sulfite neutralization: dropwise adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution at a speed of 14mL/min while stirring under the condition that the stirring speed is 40rpm/min, and continuously stirring for 1.4h after dropwise adding is finished;
the preparation method of the sodium sulfite solution comprises the following steps: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare 1500mL of 120g/L sodium sulfite solution, adding saturated sodium hydroxide solution, adjusting the pH to 8, and dissolving for 18min at 58 ℃ and 28 rpm/min;
s7, filtering: and when the solution fades from yellow to colorless and transparent, filtering by using tetrafluoro filter paper with the aperture of 0.22um, and fixing the volume to 2500mL by using pure water to obtain 20g/L of gold sodium sulfite electroplating solution.
Example 5
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1, dissolving: adding 50g of 99.99% sponge gold into 220mL of aqua regia, and dissolving at 98 ℃ for 1.4h to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 98 ℃ for 3.2h, concentrating the chloroauric acid into syrup, and adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 4 times to remove nitrogen oxide yellow smoke generated by nitric acid;
s3, constant volume: adding 12% hydrochloric acid into the system in the step S2, and fixing the volume of the chloroauric acid to 500mL to ensure that the gold content is 100 g/L;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 12 ℃;
s5, adjusting pH: under the conditions of ice water bath and stirring speed of 42rpm/min, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, wherein the dropwise adding speed of the saturated sodium hydroxide is as follows: 4.5mL/min, and adjusting the pH value to 6.2;
s6, sodium sulfite neutralization: dropwise adding the chloroauric acid solution after pH adjustment into the sodium sulfite solution at a speed of 13mL/min while stirring under the condition that the stirring speed is 42rpm/min, and continuously stirring for 1.3h after dropwise adding is finished;
the preparation method of the sodium sulfite solution comprises the following steps: weighing sodium sulfite, dissolving in pure water to prepare 1483mL of 118g/L sodium sulfite solution, adding saturated sodium hydroxide solution, adjusting pH to 8, and dissolving at 54 ℃ and 25rpm/min for 17 min;
s7, filtering: and when the solution fades from yellow to colorless and transparent, filtering by using tetrafluoro filter paper with the aperture of 0.22um, and fixing the volume to 2500mL by using pure water to obtain 20g/L of gold sodium sulfite electroplating solution.
Comparative example 1
A method for preparing a gold sodium sulfite electroplating solution, which is different from the method of example 3 in that: the operation of step S4 is not performed.
Comparative example 2
A method for preparing a gold sodium sulfite electroplating solution, which is different from the method of example 3 in that: in step S5, the pH is adjusted to 9.
Comparative example 3
A preparation method of a gold sodium sulfite electroplating solution comprises the following steps:
s1: adding 50g of 99.99% sponge gold into 200mL of aqua regia, and dissolving at 95 ℃ for 2h to obtain chloroauric acid;
s2: continuing to keep the temperature at 95 ℃ for 4h, concentrating the chloroauric acid into syrup, and adding 50mL of 36% concentrated hydrochloric acid into the concentrated chloroauric acid for 4 times to remove nitrogen oxide yellow smoke generated by nitric acid;
s3: adding 250mL of pure water into the system in the step S2 to dilute the chloroauric acid, dropwise adding ammonia water into the diluted chloroauric acid solution at the speed of 5mL/min, and stirring at the stirring speed of 40rpm/min until the precipitate of the aurauric acid is completely generated;
s4: washing the precipitate of the bronsted acid obtained in the step S3 for 8 times by adopting pure water with the temperature of 70 ℃ and the volume of 200mL, and removing water by adopting a suction filtration mode;
s5, adding 200mL of 120g/L sodium sulfite solution into the washed precipitate of the bronsted acid, and heating at 70 ℃ until the bronsted acid is completely dissolved to obtain the composition.
Performance detection
1. The purity of the gold sodium sulfite solution prepared by the methods of examples 1-5 and comparative examples 1-3 is tested according to the GB/T25933-2010 standard;
2. determining the gold content of the sodium gold sulfite solution prepared in the examples 1-5 and the comparative examples 1-3 by adopting a sodium decasulfite dihydrochloride gold reduction gravimetric method, and calculating the conversion rate of gold;
for gold reduction with sodium decasulfite dihydrochloride gravimetric method see: the measurement of gold content of sodium gold sulfite for cyanide-free gold plating was reported by sanmen's institute of occupational and technology. Vol 9, No. 3, 2010;
3. carrying out an electroplating experiment on the gold sodium sulfite solution prepared by the methods of examples 1-5 and comparative examples 1-3, and observing the color, brightness, uniformity and bonding force of a plating layer of a plated part;
the specific method of the plating experiment is as follows: the method comprises the following steps of (1) carrying out electroless gold plating on Gaoqiao Zhaoman, Shanbenhong, Zhongdao Chengzi and the like: china, 1460131A [ P ]. 2003-12-03.
The results are shown in Table 1.
TABLE 1
| Purity of | Conversion rate | Color of plating layer | Lightness of light | Uniformity of | Binding force | |
| Example 1 | 99.995％ | 100％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Example 2 | 99.995％ | 100％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Example 3 | 99.995％ | 100％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Example 4 | 99.995％ | 100％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Example 5 | 99.995％ | 100％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Comparative example 1 | 99.99％ | 93.6％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Comparative example 2 | 99.99％ | 88.1％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
| Comparative example 3 | 99.99％ | 97.4％ | Golden yellow colour | Light brightness | Uniformity | Without gold falling |
As can be seen from Table 1, the gold in the sodium gold sulfite solution prepared by the method of examples 1-5 of the present application has a purity as high as 99.995%, 50g of 99.99% sponge gold can be 100% converted into sodium gold sulfite, and the sodium gold sulfite can be electroplated on a workpiece, so that the plating layer is golden yellow, bright and good in uniformity, and no gold is dropped.
Comparative example 1 differs from example 3 in that the temperature reduction treatment is not carried out, and the experimental result shows that 50g of 99.99% sponge gold added is only 93.6% converted into gold sodium sulfite. The experimental result shows that the gold can be hydrolyzed and settled without cooling treatment in the preparation process of the sodium gold sulfite, thereby reducing the conversion rate of the sodium gold sulfite.
Comparative example 2 differs from example 3 in that the pH of the solution was adjusted to 9 with NaOH, and the results of the experiment showed that 50g of 99.99% sponge gold added was only 88.1% converted to gold sodium sulfite. The experimental result shows that when the pH value of the solution is 9, a large amount of gold hydroxide can be formed, on one hand, gold hydroxide can finally form gold simple substance to be separated out, on the other hand, the conversion rate of the gold hydroxide and sodium sulfite complexed into the sodium gold sulfite is not high, and the two aspects influence the utilization rate of gold.
Comparative example 3 is the most commonly used method for preparing gold sodium sulfite at present, and it can be seen from table 1 that 50g of 99.99% sponge gold added is 97.4% converted to gold sodium sulfite. Experimental results show that although the conversion rate of gold is high, gold fulminate is formed in the preparation process, 8 times of washing is needed to remove chloride ions, the process is complicated and dangerous, and the applicability of large-scale industrialization is poor.
The embodiments of the present invention are preferred embodiments of the present application, and the scope of protection of the present application is not limited by the embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (10)
1. A preparation method of a gold sodium sulfite electroplating solution is characterized by comprising the following steps: the method comprises the following steps:
s1, dissolving: adding gold into aqua regia, and dissolving at 90-100 deg.C for 1-3 hr to obtain chloroauric acid;
s2, nitrate removal: continuing to keep the temperature at 90-100 ℃ for 3-5h, concentrating the chloroauric acid into syrup, and adding concentrated hydrochloric acid into the concentrated chloroauric acid for multiple times to remove nitric oxide yellow smoke generated by nitric acid;
s3, constant volume: fixing the volume of the solution obtained in the step S2 by using hydrochloric acid;
s4, refrigerating: putting the solution with constant volume in an ice water bath, and controlling the temperature of the chloroauric acid solution at 0-15 ℃;
s5, adjusting pH: under the condition of ice water bath, dropwise adding a saturated sodium hydroxide solution into the chloroauric acid solution while stirring, and adjusting the pH to 6-7;
s6, sodium sulfite neutralization: adding the chloroauric acid solution after the pH is adjusted into a 120g/L sodium sulfite solution of 115-one while stirring, and continuing stirring for 1-1.5h after the dropwise addition is finished; the mass ratio of the sodium sulfite to the gold is (3-4) to 1;
s7, filtering: and (5) when the solution in the step (S6) fades from yellow to colorless and transparent, filtering, and adding pure water to a constant volume to obtain the gold sodium sulfite electroplating solution.
2. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S1, the mass-volume ratio of gold to aqua regia is 1 (3-5).
3. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S2, the concentrated hydrochloric acid is 36% concentrated hydrochloric acid, and the addition times are 4-5 times.
4. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S3, the solution obtained in step S2 is made to a constant volume with 12% hydrochloric acid.
5. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S4, the temperature of the chloroauric acid solution is controlled at 10-15 ℃.
6. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S5, the stirring speed is 30-50 rpm/min; the dropping speed of the saturated sodium hydroxide is as follows: 3-5 mL/min.
7. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S6, the preparation method of the sodium sulfite solution is: weighing sodium sulfite, dissolving the sodium sulfite in pure water to prepare a sodium sulfite solution of 120g/L of 115-one, adding a saturated sodium hydroxide solution, adjusting the pH to be =8, and dissolving for 10-20min at the temperature of 50-60 ℃ and under the condition of 20-40 rpm/min.
8. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S6, the stirring speed is 30-50 rpm/min; the dropping speed of the chloroauric acid solution is 10-15 mL/min.
9. The method for preparing a gold sodium sulfite electroplating bath as set forth in claim 1, wherein: in step S7, filtration was performed using tetrafluoro filter paper with a pore size of 0.22 um.
10. A gold sodium sulfite electroplating bath prepared by the method for preparing a gold sodium sulfite electroplating bath as claimed in any one of claims 1 to 9.
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