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(1) Silver electrolytic refining:
Anode: The total amount of gold and silver is not less than 98%, and the crude gold having a gold content of not more than 30% is cast into an anode plate. When the content of silver is less than 68%, silver should be added when preparing the anode plate.
Cathode: silver plates, aluminum plates or stainless steel plates.
Electrolytic cell: made of plastic or ceramic.
Electrolyte: 3~5g/L of nitric acid, 120~160g/L of silver nitrate, no more than 80g/L of copper nitrate, temperature 25°C. It enters from one end of the cell and flows out from the other end for recycling.
Electrolytic conditions: DC, tank voltage 1.5~2.5V, cathode current density 250~450A/ m2 , same pole center distance 100~160mm, electrolyte circulation speed 0.5~1.0L/A.
During electrolysis, the crude jinyang electrode plates of silver, copper, lead, bismuth into solution, the silver cathode with loose granular crystals deposited on the cathode, gold and platinum group elements, selenium, tellurium, sulfur and other insoluble The powdered anode mud is precipitated in the tank. Since the silver deposited on the cathode is easily detached and mixed with the powdered anode mud, the anode is packed in a dense polyester bag to collect the gold anode mud.
(2) Gold Electrolytic Refining:
Anode: The anode plate of the anode mud obtained by silver electrolysis is cast into an anode plate, and the content of silver is not more than 20%.
Cathode: pure gold.
Electrolytic cell: Made of heat-resistant glass or ceramic.
Electrolyte: containing AuCl 3 250 ~ 500 g / liter, HCl 150 ~ 200 g / liter, temperature 50 ~ 70 ° C.
Electrolytic conditions: asymmetric pulsating current, AC/DC current intensity ratio (1.5~2): 1, tank voltage 0.4~0.8 volts, cathode current density 400~700A/ m2 , and the same pole center distance 80~120mm.
Electrolytic refining gold is currently the most widely used and most complete method. When crude gold silver content is less than 20%, it can be directly electrolytic refining gold; silver-containing thick gold points shall mainly gold and silver electrolytic refining electrolytic refining in two steps.