Electrowinning, also called electrorefining or electroextraction, is the electrodeposition of metals from their ores that have been introduced into the solution or liquefied. Electrowinning is an important technology that allows purification of non-ferrous metals in a single, straightforward, cost effective step.
Electrowinning involves the application of an electrical current between two electrodes that are immersed in a metal bearing solution (known as electrolyte). Under certain conditions, dissolved metal will be plated onto the negative electrode (cathode) whilst the anodic reaction produces the dissociation of water into its base components; hydrogen ions and oxygen.
Anodes used in electrowinning should have electrochemical stability in sulfate electrolytes, resistance to the chemical effects of oxygen liberated on the anode surface, low oxygen overvoltage, mechanical stability and structural integrity under operating conditions for optimal performance. However must also maintain product quality and environmental safety.
An example of the reaction taking place is detailed below:
Anodes：2H2O→O2↑ + (4H+) + 4e–
Cathode：Mn+ + ne–→nM