Electrolytic Refining in Aqueous Solution

Electrorefining in aqueous solution is used for purifying metals and for electroplating, for example, for corrosion protection by zinc coating of steel. Electrorefining of metals is only possible for those metals with a positive standard potential (Ag, Au, Cu, Table 6.19.1) or if H2 formation at the cathode (which competes with deposition of the metal) is hindered by a high overpotential (Zn, Ni). For electrochemically very non-noble metals such as aluminum with a very negative standard potential, fused salt electrolysis is needed (Section 6.19.4.2). 

As an example, we inspect electrolytic copper refining, which utilizes the electrochemical dissolution of an impure copper anode in an electrolytic cell containing a 

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