Extraction of Metals

Extraction of Copper - Purification by Electrolysis.

In the purification of copper the rate at which the copper ions
enter the electrolyte from the anode
is the same as the rate at which the copper ions
leave the electrolyte at the cathode. The concentration of
the copper(II) sulfate solution therefore remains unchanged.

As copper is transferred from the anode to the cathode
any soluble impurities in the copper anode
dissolve in the copper(II) sulfate and are removed later.

Insoluble impurities fall to the bottom of the cell and form a sludge.
The sludge often contains precious metals (silver and platinum)
which are extracted and refined.

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