| section Home
Production, Amateur Radio amateur Model aircraft, rocket- Useful, entertaining |
Stealth master
Electronics Physics Technologies invention |
space Mystery
Earth Mysteries Secrets of the Ocean Stealth section Map |
  |
| Use of material is permitted for reference (for websites - hyperlinks) | |||
Navigation: => |
Home / Products Patents / In the section of the catalog / back / |
|
INVENTION
Russian Federation Patent RU2176290
The electrolytic regeneration of silver from silver-coated
On metal base
Name of the inventor: Gromov OG .; AP Kuzmin .; Kunshina G.B .; ESTHER POLLARD Lokshin .; Kalinnikov VT
The name of the patentee: Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials. IV Kola Science Centre of RAS
Address for correspondence: 184200, Murmansk, Apatity, Str.. Fersman, 14, KSC, ICTREMRM, Patent Department
Starting date of the patent: 2000.12.08
The invention relates to metallurgy noble metals, preferably silver, and can be used in the electrolytic extraction of silver from a silver scrap electrical and electronic products. The process uses an electrolyte for the anodic dissolution of silver, which contains sulfuric acid at a concentration 80,0-84,5 wt.% And silver sulfate in an amount of 15-40 g / l acid. Electrolysis was carried out at a voltage of not more than 1.8 with the release of metallic silver on the cathode. The electrolysis is preferably conducted at 35-50 o C c regeneration of silver-based coatings containing copper, iron or aluminum. The achieved result is the implementation of the cathodic reduction of silver from scrap electrical and electronic products without the destruction of their material base. When the purity of silver metal released at the cathode is not less than 99.9% when removing 99,6-99,8%. The composition of the electrolyte include the widely used non-toxic substances.
DESCRIPTION OF THE INVENTION
The invention relates to metallurgy noble metals, preferably silver, and can be used in the electrolytic extraction of silver from a silver scrap electrical and electronic products.
In silver recovery of silver-based coatings containing copper, iron or aluminum, a problem arises selective silver recovery without destroying the base and dissolving the solder while obtaining high-purity metallic silver. In this important limitation of the technology used harmful effects of its components or the environment.
Known process for regenerating silver from the silver coating on a copper-based (see. RF Patent N 2109824, IPC 6 C 22 B 7/00, 11/00, 1998), which includes the processing of scrap mixture of concentrated sulfuric and nitric acids with a solution of silver transfer , formed of silver sulfate precipitation, sintering it with potassium hydroxide at 450-500 o C and leached with water to obtain a cake of metallic silver.
The disadvantage of this method is its multi-stage and high power consumption. In practicing the method requires strict control of the concentration of free nitric acid and the temperature of the acid treatment of the scrap as possible contamination and corrosion of the basis of the expected product.
There is a method of electrolytic silver recovery from silver coating on a copper basis (see. Gaidarenko OV, Drobot DV, Chernyshov VI Concentration precious and platinum group metals by selective electrochemical separation of non-ferrous metals from secondary raw sources. Math. High schools :. Flowers metallurgy, N 4, 1997, p 18-22) comprising two stages of the electrolytic treatment.. In a first step, dissolving in the solder with the release of sulfamic electrolyte at the cathode potentials at respective powders of lead, tin and zinc. In the second step was dissolved in sulfuric acid base copper-containing electrolyte on the cathode with the release of copper powder, and the silver is concentrated in the anode slime.
A disadvantage of this process is complete the electrochemical dissolution bases and electronic products with silver solder to transfer cuttings that does not allow obtaining high-purity silver, and increases power consumption of the process.
Known method and electrolytic recovery of silver from a silver-based coating on the metal (see. U.S. Patent N 3,788,958, N. Cl. 204-146, 1974), which includes silver anodic dissolution in an electrolyte containing 86 vol.% Concentrated sulfuric acid, 12 vol.% ethanol and 2 vol.% mononitrobenzola, at 40 o C, a voltage of 8 B and a current density of 12 A / dm 2.
The disadvantage of this method is that it does not permit recovery of silver from a cathode of the presence of the electrolyte in the form of a strong oxidant nitrobenzene, which is also highly toxic substances.
The technical result is selective electrochemical recovery of silver from scrap containing silver coating on a metal base in the presence of solder on the cathode to obtain high-purity metallic silver, and the exclusion from the composition and electrolyte toxic substances.
Technical result is achieved by a method for the electrolytic recovery of silver from a silver-based metal coating comprising silver anodic dissolution by heating in an electrolyte containing sulfuric acid and an additive according to the invention the electrolyte comprises sulfuric acid with a concentration of 80.0-84.5 wt.%, And as an additive - silver sulfate in an amount of 15-40 g / l acid, the electrolysis is conducted at a voltage of not more than 1.8 with the release of silver on the cathode. and in that the electrolysis is carried out at 35-50 o C, and in that the regeneration of the silver lead-based coating containing copper, iron or aluminum.
Using the electrolysis of sulfuric acid concentration of 80.0-84.5 wt. % Provides selective anodic dissolution of the silver coating and the selection of the cathode powder high-purity metallic silver. Sulfuric acid at a concentration higher than 84.5 wt.% Silver cathode silver sulfide contaminants, and at a concentration of less than 80.0 wt.% Starting significant anodic dissolution of the metal base and solder.
The use of silver sulfate in the electrolyte increases its electrical conductivity and contributes to the formation of the cathode crystalline precipitate of metallic silver. When silver sulfate concentration less than 15 g / l acid is formed on the cathode amorphous precipitate of silver and silver sulfate precipitation occurs to precipitate at a concentration of more than 40 g / l acid.
Implementation of the electrolysis at a voltage of less than 1.8 provides a selective anodic dissolution of silver. When a voltage of more than 1.8 in the formation of silver sulfide on the cathode, and a partial dissolution of the metal substrate and the solder.
Carrying out electrolysis at 35-50 o C helps to maintain a high speed of the process. At temperatures below 35 o C the process rate decreases sharply, and at a temperature above 50 o C begins notable anodic dissolution of the solder.
Implementation of electrolysis under the above conditions enables selectively removing silver from a silver metal based coatings containing copper, iron or aluminum.
The above features and advantages of the invention may be more clearly explained by the following examples.
example 1
Carry out regeneration of silver from a silver coating on the copper bolt M16h30 with silver content 0.65 wt.%.
Bolts with a tin-lead solder in an amount of 10 pieces weighing 597 g was charged in a glass Teflon perforated copper current lead that serves as an anode basket. Anode basket was placed in the electrolytic cell body, made in the form of a stainless steel cylinder which was then poured into 1 liter of a sulfuric acid concentration of 84.5 wt.%, Containing 30 g of silver sulphate. The electrolyzer body is connected to the negative pole of the current source, and performs the function of cathode. Electrolyte temperature was maintained at 45 o C.
Electrolysis is carried out at a voltage of 1.8V.
When voltage is applied through the electrolyte starts to leak current of 5 A, which decreases as the removal of coatings. The process is stopped when the current value of 0.1 A, while the duration of electrolysis is about 45 minutes.
During electrolysis, the electrolyte transparency and color are unchanged. At the cathode, silver stands out as a fine powder peelable light-gray color. The resulting silver is separated from the electrolyte by centrifugation followed by washing and drying at 150 o C.
The dried product weighing 3.87 g is a metallic silver with a purity of 99.9% Content of impurities,%: Cu 0.03, Pb 0.01 , Sn 0.003, Fe 0.003. Recovery of silver from the coating is 99.7%.
The surface of the bolts after washing did not contain traces of corrosion.
example 2
Carry out regeneration of silver from a silver coating on the brass nuts M16 at the silver content of 1.18 wt.%.
Nut pieces in an amount of 45 weighing 685 g was charged into the anode basket which is then placed in the electrolytic cell housing. The electrolyzer poured 1 liter sulfuric acid concentration of 80.0 wt.
%, Containing 15 g of silver sulphate. Electrolyte temperature is maintained in the range 50 o C.
Electrolysis was carried out at a voltage of 1.5V.
When voltage is applied through the electrolyte starts to leak current of 8 A, which decreases as the removal of coatings. The process is stopped when the current value of 0.1 A, while the duration of electrolysis is about 60 minutes.
During electrolysis, the electrolyte transparency and color are unchanged. At the cathode, silver stands out as a fine powder peelable light-gray color. The resulting silver is separated from the electrolyte by centrifugation followed by washing and drying at 150 o C.
The dried product weighing 8.07 g is a metallic silver with a purity of 99.9% Content of impurities,%: Cu 0.04, Sn 0.01 , Fe 0.006. Recovery of silver from the coating is 99.8%.
The surface of the nuts after washing did not contain traces of corrosion.
example 3
Carry out regeneration of silver from a silver coating on duralumin plates measuring 10 x 5 x 0.15 cm silver content 1.4 wt.
%.
Plates of 10 pieces weighing 239 g was charged into the anode basket which is then placed in the body of the cell. The electrolyzer poured 1 liter sulfuric acid concentration of 82 wt.%, Containing 20 g of silver sulphate. Electrolyte temperature is maintained in the range 35 o C.
Electrolysis was carried out at a voltage of 1.6 V. When a voltage is applied across the electrolyte starts to leak current of 4 A, which decreases as the removal of coatings. The process is stopped when the current value of 0.1 A, while the duration of electrolysis is about 40 minutes.
During electrolysis, the electrolyte transparency and color are unchanged. At the cathode, silver stands out as a fine powder peelable light-gray color. The resulting silver is separated from the electrolyte by centrifugation followed by washing and drying at 150 o C.
The dried product weighing 3.34 g is a metallic silver with a purity of 99.9% Content of impurities,%: Cu 0.01, Fe 0.003 , Al 0.02. Recovery of silver from the coating is 99.8%.
The surface of the plates after washing contained no traces of corrosion.
example 4
Regeneration is carried silver from the silver coating on the casings of electric articles of stainless steel having a different shape and size, with an average silver content of 0.72 wt.%.
Shells weighing 274 g was charged into the anode basket that is placed in the body of the cell. The electrolyzer poured 1 liter sulfuric acid concentration of 84.5 wt.%, Containing 30 g of silver sulphate. Electrolyte temperature was maintained at 45 o C.
Electrolysis is carried out at a voltage of 1.2.
When voltage is applied through the electrolyte starts to flow a current of 3 A, which decreases as the removal of the coating. The process is stopped when the current value of 0.15 A, while the duration of electrolysis is about 70 minutes.
During electrolysis, the electrolyte transparency and color are unchanged. At the cathode, silver stands out as a fine powder peelable light-gray color. The resulting silver is separated from the electrolyte by centrifugation followed by washing and drying at 150 o C. The dried product weighing 1.965 g is a metallic silver with a purity of 99.9% Content of impurities,%: Cu 0.01, Fe 0.04 , Ni 0.03. Recovery of silver from the coating is 99.6%.
The surface of the hull after washing did not contain traces of corrosion.
Examples 5 and 6 illustrate the present invention by using values prohibitive regime parameters, which reduces the purity of silver released at the cathode and substrate articles corrode.
example 5
With Carry out silver recovery according to the conditions of Example 1.
The difference lies in the fact that the sulfuric acid concentration of 90 wt.
% And the electrolysis is conducted at a voltage of 2 B and electrolyte temperature in the range 60 o C. When a voltage is applied across the electrolyte starts to leak current of 6.5 A.
The process is stopped when the current value of 0.1 A.
The duration of electrolysis is about 30 minutes.
During electrolysis, the electrolyte darkens and becomes opaque. At the cathode, the silver powder is isolated as a dark gray color which is hardly separated from the cathode. The purity of silver was 96.6% when the content of impurities,%: Ag 2 S 2.5, Cu 0.3, Pb 0.3, 0.2 Sn, Fe 0,003.
After washing on the surface of the bolts and the outer layer of solder visual traces of corrosion.
example 6
Silver recovery is performed according to the conditions of Example 1.
The difference lies in the fact that the sulfuric acid concentration of 75 wt.
%, Containing 50 g of silver sulphate, and the electrolyte temperature is maintained in the range 30 o C.
The electrolyte is turbid due to precipitation of silver sulfate. When voltage is applied through the electrolyte starts to flow a current of 1 A.
The process is stopped when the current value of 0.1 A, while the duration of electrolysis is about 1 to 50 minutes.
During electrolysis, the electrolyte becomes pale blue. At the cathode, the silver is released in the form of granular powder silver. The purity of silver was 97.4% when the content of impurities,%: CuSO 4 0.2, Cu 1.1, Pb 0.6, Sn 0.5, Fe 0.1. After washing on the surface of the bolts and the outer layer of solder visually seen intensive corrosion.
From the above examples show that the inventive method allows the cathode silver recovery from scrap electrical and electronic products without the destruction of their material base. When the purity of silver metal released at the cathode is not less than 99.9% when removing 99.6-99.8%. The composition of the electrolyte include widely-used non-toxic substances.
CLAIM
Electrolytic silver recovery method of silver coating on the metal substrate, comprising silver anodic dissolution by heating in an electrolyte containing sulfuric acid and an additive, characterized in that sulfuric acid with a concentration of 80,0-84,5 wt.%, And as additives - silver sulfate in an amount of 15-40 g / l acid, the electrolysis is conducted at a voltage of not more than 1.8 with the release of silver on the cathode.
A method according to claim 1, characterized in that the electrolysis is carried out at 35-50 o C.
A method according to claim 1 or 2, characterized in that the regeneration of lead silver from a silver-based coating containing copper, iron or aluminum.
print version
Publication date 05.12.2006gg
Comments
Commenting, keep in mind that the content and the tone of your messages can hurt the feelings of real people, show respect and tolerance to his interlocutors, even if you do not share their opinion, your behavior in terms of freedom of speech and anonymity offered by the Internet, is changing not only virtual, but real world. All comments are hidden from the index, spam control.