Silver electrolytic refining
2020-08-17 10:17Introduction：Silver electrolytic refining Electrolytic refining is the most widely used and perfect refining method, usually including silver electrorefining and gold electrorefining. Silver electrorefining is to make anode from raw materials to be pur
Silver electrolytic refining
Electrolytic refining is the most widely used and perfect refining method, usually including silver electrorefining and gold electrorefining. Silver electrorefining is to make anode from raw materials to be purified. During electrolysis, silver is deposited on the cathode and gold enters the anode slime. Gold electrorefining is the melting and casting of anode slime produced by silver electrolysis into anode. During electrolysis, 99.99% of the gold was deposited on the cathode.
The production of silver electrorefining anode plate requires gold and silver to be no less than 98 percent, copper content to be less than 5 percent, and gold content to account for 1/3 of the total. Electrolytic cathode can be made of silver plate, aluminum plate, titanium plate or stainless steel plate. The electrolyte is usually made up of nitric acid of 3 ~ 5 g / l, silver of 120 g / L ~160 g / l, copper of no more than 80 g / l. At room temperature. Silver nitrate electrolyte is prepared with 99.5% silver powder and industrial nitric acid.
The electrolysis conditions are as follows: the cell voltage is 1.5 ~ 2.5V, the cathode current density is 250 ~ 450A / m2, the center distance of the same stage is 100 ~ 160mm, and the electrolyte circulation velocity is 0.5 ~ 1.0l / min.
In the electrolysis process, the anode dissolved continuously, silver, copper, lead, bismuth and so on entered the solution, gold and platinum group metals, selenium, tellurium, sulfur and so on were insoluble, and precipitated in the form of powdered anode slime. Silver entering the solution is deposited on the cathode in the form of loose large particles, which is easy to fall off the cathode. In order to avoid mixing pure silver sediment with anode mud, anode is often packed in dense polyester cloth bag to collect gold-bearing anode mud. At the end of electrolysis, the anode mud is removed from the anodic cloth bag and the silver deposit is removed from the bottom of the electrolyzer. Pure silver deposits containing 99.5% silver and 99.9% high purity silver were obtained. When the gold content of the anode mud is higher than 80%, the anode is melted into an anode for gold electrolysis. When the anode is lower than 80%, the silver and other impurities in the anode can be dissolved by nitric acid, or the pure silver can be remixed into the anode according to the ratio column, and the anode containing 35% of gold can be cast for secondary silver electrolysis. To obtain the anode mud containing more than 80% gold.
When the copper content in the electrolyte reaches 4%, the new electrolyte should be replaced, and the waste electrolyte should be treated to recover valuable metals such as silver and copper.
