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What happens to gold and silver during copper electrorefining?
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copper processing
Molten copper being made into plates.
During the electrorefining of copper, gold and silver do not dissolve into the electrolytic solution with the copper. Instead, because they are noble metals, they remain insoluble and settle at the bottom of the refining tank as a byproduct known as anode slimes.1
These slimes contain significantly higher concentrations of precious metals than the original copper concentrate. To recover the gold and silver, the slimes are typically smelted to produce a metallic mixture called doré. This bullion is then subjected to further parting processes—often using electrolysis—to separate and refine the gold and silver into their pure forms.23