CN115074783B - Preparation method of 5N high-purity silver - Google Patents
Preparation method of 5N high-purity silver Download PDFInfo
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Abstract
The invention discloses a preparation method of 5N high-purity silver, which comprises the following steps: providing a first silver nitrate electrolyte, adding sodium hydroxide into the first silver nitrate electrolyte, and reacting to obtain a purifying agent; providing silver nitrate electrolyte to be purified, adding the purifying agent into the silver nitrate electrolyte to be purified, and reacting to obtain purified liquid; and (3) adjusting the acidity of the purified liquid, and carrying out electrolysis by taking the purified liquid with the adjusted acidity as electrolyte, silver plates as anodes and titanium plates as cathodes to obtain the 5N high-purity silver. The preparation method of the 5N high-purity silver provided by the invention is simple, can be closely combined with production practice, saves cost and simplifies the process by utilizing the existing silver nitrate electrolyte, can prepare a large amount of silver powder which is uniform in crystallization and meets the 99.999% requirement, and is suitable for large-scale industrial production of the 5N high-purity silver.
Description
Technical Field
The invention relates to the technical field of noble metal refining, in particular to a preparation method of 5N high-purity silver.
Background
Silver is used as a noble metal, has good electric conductivity and heat conductivity and high ductility, is an important industrial raw material, can be used as a chemical material, a photosensitive material, an electronic and electric appliance material and the like, and has very wide application. The rapid development of the microelectronics industry makes it urgent to find a preparation method of 5N high-purity silver.
The electrodeposition method is a method for recovering silver from a silver-containing solution using an inert material as an anode and a titanium plate as a cathode. Because the electrodeposition process is an anodic acid production process, the fluctuation of silver/acid ratio in an electrodeposition system is large, the method is not suitable for electrodepositing refined silver from high-concentration silver nitrate liquid, and the defects of unstable electrodeposition liquid system, low current efficiency, low treatment capacity and the like exist, and the purity of the silver powder is difficult to reach 5N level.
Accordingly, the prior art is still in need of improvement and development.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide a preparation method of 5N high-purity silver, and aims to solve the problem that the purity of silver powder prepared by adopting the existing electrodeposition method is less than 5N level.
The technical scheme of the invention is as follows:
In a first aspect of the present invention, there is provided a method for preparing 5N high purity silver, comprising the steps of:
Providing a first silver nitrate electrolyte, adding sodium hydroxide into the first silver nitrate electrolyte, and reacting to obtain a purifying agent;
providing silver nitrate electrolyte to be purified, adding the purifying agent into the silver nitrate electrolyte to be purified, and reacting to obtain purified liquid;
and (3) adjusting the acidity of the purified liquid, and carrying out electrolysis by taking the purified liquid with the adjusted acidity as electrolyte, silver plates as anodes and titanium plates as cathodes to obtain the 5N high-purity silver.
Optionally, the first silver nitrate electrolyte contains metal impurities, sodium hydroxide is added into the first silver nitrate electrolyte containing the metal impurities, the pH value of the system is controlled to be 9-13, and a purifying agent is obtained after the reaction;
the main components of the purifying agent comprise: silver oxide, iron, copper.
Optionally, the mass content of metal impurities in the silver nitrate electrolyte to be purified is more than 8%, and the metal impurities mainly comprise copper, iron, lead and bismuth.
Optionally, adding the purifying agent into the silver nitrate electrolyte to be purified, and controlling the pH value to be 4+/-1.
Optionally, the ratio of the purifying agent to the silver nitrate electrolyte to be purified is (50-100) g:600mL.
Optionally, the purifying agent is added into the silver nitrate electrolyte to be purified, and after the reaction, the purified liquid is obtained, wherein the reaction temperature is 60-90 ℃, and the reaction time is 60-120 min.
Optionally, the acidity of the purified liquid is adjusted by adding nitric acid and water, and the acidity of the purified liquid after the adjustment of the acidity is 4-10 g/L.
Optionally, the current density of the electrolysis is 400-600A/m 2, and the time is 12-36 h.
Optionally, the current density of the electrolysis is 500A/m 2 for 24 hours.
Optionally, the silver plate is formed by casting silver powder, and a polyester cloth bag is sleeved outside the silver plate.
The beneficial effects are that: according to the invention, the existing silver nitrate electrolyte of the production line can be used for preparing the purifying agent, so that the cost is saved; in addition, the purifying agent is added into the silver nitrate electrolyte to be purified, so that the content of impurity ions in the purified liquid can be below 0.01g/L, and the purifying degree is high. The electrolytic liquid system is stable in the electrolytic refining process, and a large amount of silver powder which is uniform in crystallization and meets the requirement of 99.999% can be prepared by the electrolytic refining method under the condition of higher current density. The preparation method of the 5N high-purity silver provided by the invention is simple, can be closely combined with production practice, saves cost and simplifies the process by utilizing the existing silver nitrate electrolyte, and is suitable for large-scale industrial production of the 5N high-purity silver.
Drawings
FIG. 1 is a flow chart of a process for treating a silver-containing waste liquid in an embodiment of the invention.
Detailed Description
The invention provides a preparation method of 5N high-purity silver, which is used for making the purposes, technical schemes and effects of the invention clearer and more definite, and is further described in detail below. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The embodiment of the invention provides a preparation method of 5N high-purity silver, which comprises the following steps:
S1, providing a first silver nitrate electrolyte, adding sodium hydroxide into the first silver nitrate electrolyte, and reacting to obtain a purifying agent;
s2, providing silver nitrate electrolyte to be purified, adding the purifying agent into the silver nitrate electrolyte to be purified, and reacting to obtain purified liquid;
S3, adjusting the acidity of the purified liquid, and carrying out electrolysis by taking the purified liquid with the adjusted acidity as electrolyte, silver plates as anodes and titanium plates as cathodes to obtain the 5N high-purity silver.
The first silver nitrate electrolyte may be a silver nitrate electrolyte existing in an electrolytic silver refining production line, or may be a silver nitrate electrolyte produced after silver is electrolytically refined; the silver nitrate electrolyte to be purified can be the existing silver nitrate electrolyte of an electrolytic refining silver production line, can also be the silver nitrate electrolyte produced after silver is electrolytically refined, and can also be silver-containing waste liquid in the silver electrolytic refining process; and the composition of the first silver nitrate electrolyte may be the same as or different from the composition of the silver nitrate electrolyte to be purified. When the silver nitrate electrolyte to be purified is silver-containing waste liquid in the silver electrorefining process, the schematic diagram of the process flow is shown in figure 1, silver powder is produced in the silver electrorefining process, the waste electrolyte and the purifying agent are added into the silver-containing waste liquid produced after the silver powder is washed for purification, and the qualified silver nitrate electrolyte is obtained and continuously enters a silver electrorefining system for use.
In the embodiment, the purifying agent can be prepared by utilizing the existing silver nitrate electrolyte of the electrolytic refining silver production line, which is beneficial to saving the cost; in addition, the purifying agent is added into the silver nitrate electrolyte to be purified, so that the content of impurity ions in the purified liquid can be below 0.01g/L, and the purifying degree is high. The electrolytic liquid system is stable in the electrolytic refining process, and a large amount of silver powder which is uniform in crystallization and meets the requirement of 99.999% can be prepared by the electrolytic refining method under the condition of higher current density. The preparation method of the 5N high-purity silver provided by the invention is simple, can be used for tightly combining production practice, has large yield, saves cost by utilizing the existing silver nitrate electrolyte, simplifies the process, and is suitable for large-scale industrial production of the 5N high-purity silver.
In step S1, in one embodiment, the first silver nitrate electrolyte contains metal impurities, sodium hydroxide is added into the first silver nitrate electrolyte containing the metal impurities, the pH of the system is controlled to be 9-13, and a purifying agent is obtained after the reaction;
the main components of the purifying agent comprise: silver oxide, iron, copper.
In the specific implementation, sodium hydroxide can be added into silver nitrate electrolyte produced after silver is electrolytically refined, the pH of the system is controlled to be 9-13, and after the reaction (the reaction comprises the reaction of silver nitrate and sodium hydroxide to generate silver oxide), the purifying agent is obtained by filtering. The main components of the purifying agent comprise the following components in percentage by mass:
83.03% silver oxide, 0.35% iron, 8.12% copper, 0.15% lead, 0.099% palladium, 0.005% platinum, <0.01% antimony, <0.01% bismuth, <0.01% selenium, and <0.01% tellurium.
In a further embodiment, sodium hydroxide is added to the silver nitrate electrolyte produced after electrolytic refining of silver, and the pH of the system is controlled to 9 to 11.
In the step S2, the silver nitrate electrolyte to be purified is purified by adopting a chemical precipitation method, specifically, the purifying agent is added into the silver nitrate electrolyte to be purified, and after the reaction, the metal impurity content of the obtained purified liquid can be below 0.01g/L, and the purifying rate can be up to above 95%. The purifying agent contains silver oxide which is brown cubic crystal system crystal or brown black powder, is alkaline oxide, has low solubility in aqueous solution, and is easy to dissolve in acid and ammonia water. By utilizing the characteristic of silver oxide, when silver oxide reacts with nitric acid in silver nitrate electrolyte to be purified, not only can silver nitrate aqueous solution be produced, but also the acidity of the whole electrolyte system can be reduced, heavy metal ions (metal impurities) in the silver nitrate electrolyte to be purified can be hydrolyzed under different pH conditions to generate precipitate for separation, and the heavy metal precipitate and the silver nitrate aqueous solution are filtered to remove the metal impurities from the silver nitrate electrolyte to be purified, so that purified liquid is obtained. The purified liquid is fed back to the silver electrorefining system for use after the acidity is adjusted by adding nitric acid solution according to actual needs.
Specifically, the main chemical reactions involved are:
Ag2O+2HNO3＝2AgNO3+H2O
Cu2++2OH-＝Cu(OH)2↓
Bi(NO3)3+3NaOH＝Bi(OH)3↓+3NaNO3
Pb(NO3)2+NaOH＝Pb(OH)2↓+NaNO3
Fe2++2NaOH＝Fe(OH)2↓+2Na+
The embodiment adopts a chemical precipitation method to purify the silver nitrate electrolyte, is easy to control, and can efficiently and deeply remove the main impurities in the silver nitrate electrolyte (the metal impurity removal rate can reach more than 95 percent), and the purified electrolyte can be returned to an electrolysis system for use after the acidity of the purified electrolyte is regulated by nitric acid.
In one embodiment, the silver nitrate electrolyte to be purified contains more than 8% by mass of metal impurities, mainly copper, iron, lead, bismuth, and small amounts of platinum, palladium, etc. When the mass content of metal impurities in the silver nitrate electrolyte to be purified is up to more than 8%, the preparation of 5N high-purity silver can be still realized. The silver nitrate electrolyte to be purified can be the existing silver nitrate electrolyte of an electrolytic refining silver production line, or can be the silver nitrate electrolyte produced after silver is electrolytic refined.
In a specific embodiment, the silver oxide is calculated as Ag per liter of electrolyte, and the chemical components of the silver nitrate electrolyte to be purified comprise:
Ag 139.5～197.5g、HNO3 2.77～7.86g、Fe 0.71～1.1g、Cu 17.56～22.32g、Pb0.33～0.96g、Bi 0.028～0.26g、Pt 0.0029～0.075、Pd 0.042～0.522g.
In one embodiment, the purifying agent is added to the silver nitrate electrolyte to be purified, and the pH is controlled to be 4+/-1. The silver nitrate electrolyte to be purified is derived from a silver electrorefining production line, has a dark blue-green color, and concretely comprises, but is not limited to, judging that the pH value is 4+/-1 by changing the color of the silver nitrate electrolyte to be purified from the dark blue-green color to the colorless color.
In one embodiment, the ratio of the purifying agent to the silver nitrate electrolyte to be purified is (50-100) g:600mL.
In one embodiment, the purifying agent is added into the silver nitrate electrolyte to be purified, and after the reaction, the temperature of the reaction is 60-90 ℃ and the reaction time is 60-120 min in the step of obtaining the purified liquid.
In step S3, in one embodiment, the acidity of the purified liquid is adjusted by adding nitric acid and water, and the adjusted acidity of the purified liquid is 4-10 g/L. The acidity of the purified liquid with the acidity of 4-10 g/L is obviously reduced in the electrolytic cycle process, and nitric acid and ionized water are required to be timely added according to actual needs to adjust the acidity of the purified liquid so as to keep the acidity at 4-10 g/L.
In one embodiment, the electrolysis has a current density of 400 to 600A/m 2 for a period of 12 to 36 hours.
In one embodiment, the electrolysis has a current density of 500A/m 2 for a period of 24 hours. The preparation of 5N high-purity silver at a high current density of 500A/m 2 cannot be realized in the prior art, and the invention can prepare high-yield 5N high-purity silver when the current density is up to 500A/m 2, thereby improving the production efficiency and simultaneously ensuring the purity of the high-purity silver.
In one embodiment, the silver plate is cast from silver powder, and the silver plate is sleeved with a polyester cloth bag. The terylene cloth bag is used for recycling a small amount of anode mud generated in the electrolysis process. The silver powder can be obtained from silver powder prepared on a silver electrorefining production line, so that local material is obtained, and the process flow is simplified.
The following is a detailed description of specific examples.
Example 1
(1) Preparation of purifying agent
Sodium hydroxide is added into silver nitrate electrolyte for a silver electrorefining industrial production line, the pH value of the system is controlled to be 10+/-1, and the mixture is reacted at 80 ℃ to obtain the purifying agent, wherein the components of the silver nitrate electrolyte are shown in the following table 1, and the components of the purifying agent are shown in the following table 2.
TABLE 1 Components of silver nitrate electrolyte for silver electrorefining Industrial production line
| Sample name | Ag | HN03 | Fe | Cu | Pb | Bi | Pt | Pd |
| Silver nitrate electrolyte (g/L) | 158.9 | 6.05 | 0.71 | 22.95 | 0.67 | 0.036 | 0.018 | 0.417 |
TABLE 2 essential components of the purifying agent
| Sample name | Ag | Fe | Cu | Sb | Pb | Bi | Se | Te | Pt | Pd |
| Purifying agent (%) | 67.34 | 0.35 | 8.12 | ＜0.01 | 0.15 | ＜0.01 | ＜0.01 | ＜0.01 | 0.005 | 0.099 |
(2) Purifying silver nitrate electrolyte to be purified
Wherein the silver nitrate electrolyte to be purified is silver nitrate electrolyte for silver electrorefining industrial production line, and the components are shown in the following table 3.
TABLE 3 Components of silver nitrate electrolyte for silver electrorefining Industrial production line
| Sample name | Ag | HN03 | Fe | Cu | Pb | Bi | Pt | Pd |
| Silver nitrate electrolyte (g/L) | 158.9 | 6.05 | 0.71 | 22.95 | 0.67 | 0.036 | 0.018 | 0.417 |
A. 600mL of the silver nitrate electrolyte to be purified was taken, 100g of a purifying agent (wet weight) was added thereto, the reaction time was 90 minutes, the reaction temperatures were each 60℃and 80℃and 90℃were used for purification, and the purified solutions were obtained by filtration, and the components of the purified solutions were shown in Table 4 below.
TABLE 4 Components of purified solutions obtained under different reaction temperature conditions
Note that: the unit is g/L.
The result shows that the content of impurity ions in the purified liquid gradually decreases along with the rise of the purification temperature, when the purification temperature exceeds 80 ℃, the dissolution phenomenon of partial impurities occurs along with the rise of the purification temperature, and simultaneously the electrolyte evaporates faster. The purification temperature is preferably 80 ℃ in the comprehensive production actual process, heating energy consumption and the like.
B. 600mL of the silver nitrate electrolyte to be purified is taken, 100g of purifying agent (wet weight) is added, the reaction temperature is 80 ℃, the reaction time is respectively 60min, 90min and 120min, the purifying liquid is obtained after filtration, and the components of the purifying liquid are shown in the following table 5.
TABLE 5 Components of purified solutions obtained under different reaction time conditions
Note that: the unit is g/L.
The result shows that the impurity ion content in the purified liquid gradually decreases along with the extension of the purification time, when the purification time reaches 120min, the effect reaches the best, the actual process of comprehensive production is realized, and the purification time is preferably 90 min.
C. 600mL of the silver nitrate electrolyte to be purified is taken, the reaction temperature is 80 ℃, the reaction time is 90min, 50g, 80g and 100g of purifying agents (wet weight) are respectively added for purification, and the purified liquid is obtained after filtration, and the components of the purified liquid are shown in the following table 6.
TABLE 6 composition of purified liquid obtained under different amounts of purifying agent
Note that: the unit is g/L.
The result shows that the content of impurity ions in the purified liquid gradually decreases along with the increase of the purifying dosage, and the adding amount of the purifying agent is preferably 100g of the purifying agent added into every 600mL of silver nitrate electrolyte to be purified in the actual production process.
Example 2
The electrolysis conditions of example 1 were verified.
(1) The preparation of the scavenger is the same as in example 1.
(2) Purifying the silver nitrate electrolyte to be purified.
Wherein the composition of the silver nitrate electrolyte to be purified is the same as in example 1.
Taking 600mL silver nitrate electrolyte to be purified, wherein the reaction temperature is 80 ℃, the reaction time is 90min, the adding amount of the purifying agent is 100g, purifying, filtering to obtain purified liquid, the components of the purified liquid are shown in the following table 7,
TABLE 7 composition of purified liquid
Note that: the unit is g/L.
The result shows that the purification efficiency of impurity ions in the silver nitrate electrolyte is over 95 percent, and the requirements of the electrolyte required by the preparation of 5N high-purity silver can be met.
The purified slag components obtained by purifying the silver nitrate electrolyte solutions to be purified in examples 1 and 2 are shown in table 8.
TABLE 8 purification slag composition
| Sample name | Ag | Fe | Cu | Sb | Pb | Bi | Se | Pt | Pd | Weight/g |
| Purification slag 1% (v) | 22.39 | 1.16 | 30.99 | ＜0.01 | 0.38 | ＜0.01 | ＜0.01 | 0.021 | 0.45 | 53.7 |
| Purification slag 2 (%) | 48.39 | 0.5 | 13.45 | ＜0.01 | 0.3 | ＜0.01 | ＜0.01 | 0.01 | 0.2 | 110 |
| Purification slag 3 (%) | 39.69 | 0.8 | 21.16 | ＜0.01 | 0.32 | ＜0.01 | ＜0.01 | 0.018 | 0.35 | 80 |
| Purification slag 4 (%) | 43.13 | 0.68 | 18.61 | ＜0.01 | 0.32 | ＜0.01 | ＜0.01 | 0.013 | 0.27 | 100 |
Wherein the purified slag 1 is an average value of purified slag correspondingly produced after 600mL of silver nitrate electrolyte to be purified in the embodiment 1 is obtained after the purified liquids A1-A3; the purification slag 2 is the average value of purification slag corresponding to the output after 600mL of silver nitrate electrolyte to be purified is used for obtaining purified solutions B1-B3 in example 1, the purification slag 3 is the average value of purification slag corresponding to the output after 600mL of silver nitrate electrolyte to be purified is used for obtaining purified solutions C1-C3 in example 1, and the purification slag 4 is the average value of purification slag corresponding to the output after 600mL of silver nitrate electrolyte to be purified is used for obtaining purified solutions D1-D3 in example 2.
Example 3
(1) The preparation of the scavenger is the same as in example 1.
(2) Purifying silver nitrate electrolyte to be purified (under the same condition, two groups of parallel experiments are carried out)
Wherein, the components of the silver nitrate electrolyte to be purified are shown in the following table 9, 600mL of the silver nitrate electrolyte to be purified is taken, 100g of purifying agent (wet weight) is added, the reaction temperature is 80 ℃ and the reaction time is 90min, the purification is carried out, the purified liquid is obtained after filtration, and the components of the purified liquid are shown in the following table 9.
TABLE 9 Components of silver nitrate electrolyte to be purified and purified solution
As is clear from the above table, the content of each impurity was 0.3g/L or less.
Implementation example 4
10 Pieces of silver powder are cast into an electrolytic tank (the total weight of the cast anode is 35.22 kg), silver electrolysis anode mud is recovered by using a polyester cloth bag as an outer sleeve, a titanium plate is used as a cathode, nitric acid is added into the purified solution 2 in the embodiment 3 as an electrolyte to prepare acid (the components of the purified solution 2 after acid preparation are shown in the following table 11, the purified solution 2 after acid preparation is denoted as electrolyte 1), direct current is introduced into the electrolytic tank to electrolyze, the current density is 500A/m 2, the electrolysis time is 24h, and 34.94kg of silver powder is produced, and the components are shown in the table 12.
The components of the purified liquid 2 and the silver anode plate are shown in table 10 below.
TABLE 10 composition of purified solution 2 and silver anode plate
TABLE 11 composition of purified solution 2 after acid formulation
| Sample name | Ag | HN03 | Fe | Cu | Pb | Bi | Pt | Pd |
| Electrolyte 1 (g/L) | 153.4 | 6.51 | ＜0.005 | 0.011 | 0.074 | ＜0.005 | ＜0.001 | ＜0.0011 |
TABLE 12 chemical composition of silver powder
| Sample name | Ag | Te | Cu | Pb | Bi | Pt | Pd | Se | Sb |
| Silver powder 1 (%) | 99.999363 | 0.00002 | 0.00012 | 0.00006 | 0.00002 | 0.00003 | 0.00027 | 0.00002 | 0.000097 |
The result shows that under the condition of the current density of 500A/m 2, when the electrolysis period of the silver anode plate is 24 hours, 34.94kg of silver powder is produced, the chemical quality meets the requirement of 99.999 percent of silver, and the recovery rate of silver is 99.20 percent.
And (3) calculating the recovery rate: input/output×100% = 34.94/35.22 ×100% = 99.20%
Example 5
The same electrolytic bath as in example 4 was used for the expansion test, and the electrolytic was carried out by continuously charging a silver anode plate, 87.34kg of the silver anode plate was charged in total, the current density was 500A/m 2, and the electrolytic process was controlled to 24 hours, wherein the chemical composition of the silver anode plate was as shown in table 13 below, the chemical composition of the purified solution after acid preparation was as shown in table 14 below (the purified solutions after acid preparation were respectively designated as electrolyte 2, electrolyte 3, electrolyte 4 and electrolyte 5), and the chemical composition of the silver powder obtained by electrolysis was as shown in table 15 below.
TABLE 13 chemical composition of silver ingot anode plate
| Sample name | Ag | Fe | Cu | Pb | Bi | Pd |
| Silver anode plate (%) | 99.995 | ＜0.01 | ＜0.01 | ＜0.01 | ＜0.01 | 0.88g/t |
TABLE 14 chemical composition of purified solution after acid formulation
| Sample name | Ag | HN03 | Fe | Cu | Pb | Bi | Pt | Pd |
| Electrolyte 2 | 153.4 | 6.51 | ＜0.005 | 0.015 | 0.074 | ＜0.005 | ＜0.005 | 0.0025 |
| Electrolyte 3 | 161.3 | 4.65 | ＜0.005 | 0.016 | 0.076 | ＜0.005 | ＜0.005 | 0.0024 |
| Electrolyte 4 | 179.2 | 6.51 | ＜0.005 | 0.016 | 0.048 | ＜0.005 | ＜0.0005 | 0.0023 |
| Electrolyte 5 | 182.3 | 5.23 | ＜0.01 | 0.017 | 0.13 | ＜0.01 | ＜0.001 | 0.0053 |
Wherein the unit is g/L.
TABLE 15 chemical composition of silver powder
| Sample name | Ag | Te | Cu | Pb | Bi | Pt | Pd | Se | Sb |
| Silver powder 2 (%) | 99.99943 | 0.00002 | 0.00006 | 0.00015 | 0.00002 | 0.00002 | 0.00018 | 0.00004 | 0.00008 |
| Silver powder 3 (%) | 99.99959 | 0.00002 | 0.00005 | 0.00006 | 0.00002 | 0.00002 | 0.00013 | 0.00002 | 0.00009 |
| Silver powder 4 (%) | 99.99957 | 0.00002 | 0.00006 | 0.00007 | 0.00002 | 0.00002 | 0.00013 | 0.00002 | 0.00009 |
| Silver powder 5 (%) | 99.99979 | 0.00001 | 0.00004 | 0.00005 | 0.00001 | 0.00001 | 0.00006 | 0.00002 | 0.00001 |
From the table, under the condition of the current density of 500A/m 2, when the electrolysis period of the silver anode plate is 24 hours, the chemical quality of the produced silver powder reaches the requirement of 99.999 percent of silver, and 86.56kg of qualified silver powder is produced in an expansion test.
(1) The pilot and expansion experiments (examples 4 and 5) produced a total of 99.999% of acceptable silver powder 34.94+ 86.56=121.5 Kg,
Silver recovery rate in the expanding test process is as follows: 86.56/87.34 ×100% =99.10%.
(2) The monitoring point temperature change is shown in table 16 below.
Table 16 temperature change at each monitoring point
| Electrolyte solution | Anode contact point | Cathode contact | Busbar contact | Electrolytic tank body | |
| 7h(℃) | 18 | 16 | 15 | 14 | 15 |
| 17h(℃) | 30 | 23 | 18 | 15 | 18 |
| 24h(℃) | 40 | 28 | 23 | 18 | 18 |
From the above table, it can be seen that under the condition of the current density of 500A/m 2, the temperature of each monitoring point is in an ascending trend along with the progress of the electrolysis process, wherein the temperature ascending trend of the electrolyte is most obviously up to 40 ℃, and the anode copper hook contact point cleans the copper hook and the conductive rod to strengthen the conductivity after each test is completed.
In summary, the invention provides a preparation method of 5N high-purity silver, which comprises the steps of purifying silver nitrate electrolyte containing metal impurities by adopting a chemical precipitation method, so that the removal of main impurities in the silver nitrate electrolyte can be efficiently and rapidly realized, and the purified electrolyte can be returned to a silver electrorefining system for use after the acidity of the purified electrolyte is regulated by nitric acid. The purification method of silver nitrate has advanced technology, easy control and high metal impurity removal rate which can reach more than 95 percent, and provides basic conditions for preparing 5N high-purity silver. Meanwhile, the inventor summarizes the optimal process conditions for purifying the silver nitrate electrolyte through a large number of experiments: the reaction temperature is 80 ℃, the reaction time is 90min, and the addition amount (wet weight) of the purifying agent is 100g/600mL of electrolyte. The purified silver nitrate electrolyte can meet the control requirement of the electrolysis process with the current density of more than 500A/m 2 (the current preparation of 5N high-purity silver cannot be realized at the current density of 500A/m 2) by adjusting the acidity to 4-10g/L, and silver powder meeting the requirement of 99.999% is produced.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (3)
1. The preparation method of the 5N high-purity silver is characterized by comprising the following steps:
Providing a first silver nitrate electrolyte, adding sodium hydroxide into the first silver nitrate electrolyte, and reacting to obtain a purifying agent;
providing silver nitrate electrolyte to be purified, adding the purifying agent into the silver nitrate electrolyte to be purified, and reacting to obtain purified liquid;
Adjusting the acidity of the purified liquid, and carrying out electrolysis by taking the purified liquid with the adjusted acidity as electrolyte, silver plates as anodes and titanium plates as cathodes to obtain the 5N high-purity silver;
The first silver nitrate electrolyte contains metal impurities, sodium hydroxide is added into the first silver nitrate electrolyte containing the metal impurities, the pH value of the system is controlled to be 9-13, and a purifying agent is obtained after the reaction; the main components of the purifying agent comprise: silver oxide, iron, copper;
the mass content of metal impurities in the silver nitrate electrolyte to be purified is more than 8%, and the metal impurities mainly comprise copper, iron, lead, bismuth and palladium;
adding the purifying agent into the silver nitrate electrolyte to be purified, and controlling the pH value to be 4+/-1;
The ratio of the purifying agent to the silver nitrate electrolyte to be purified is (50-100) g:600mL;
the purifying agent is added into the silver nitrate electrolyte to be purified, and after the reaction, the purified liquid is obtained, wherein the reaction temperature is 60-90 ℃, and the reaction time is 60-120 min;
Adjusting the acidity of the purified liquid by adding nitric acid and water, wherein the acidity of the purified liquid after adjusting the acidity is 4-10 g/L;
The current density of the electrolysis is 400-600A/m 2, and the time is 12-36 h.
2. The method for preparing 5N high purity silver according to claim 1, wherein the electrolytic current density is 500A/m 2 for 24 hours.
3. The method for preparing 5N high purity silver according to claim 1, wherein the silver plate is cast from silver powder, and the silver plate is covered with a polyester cloth bag.
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| CN112410828A (en) * | 2020-11-24 | 2021-02-26 | 深圳市贵金装备科技有限公司 | Process for preparing high-purity silver by high-concentration silver nitrate electrodeposition method |
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