électrorefining

Electrorefining is a process used to purify metals. It employs electrolysis to separate a less pure metal from an alloy or an impure sample. The impure metal is used as the anode in an electrolytic cell, while a thin sheet of pure metal serves as the cathode. The electrolyte is a solution containing ions of the metal being refined.

During electrorefining, an electric current is passed through the cell. At the anode, the impure metal dissolves, with its metal ions entering the solution. These metal ions then migrate to the cathode. At the cathode, the metal ions gain electrons and deposit as a pure metal layer. Impurities that are less reactive than the metal being refined will not dissolve and will fall to the bottom of the cell as anode sludge. More reactive impurities will dissolve but will not deposit at the cathode because their ions have a lower reduction potential.

This method is widely used for purifying copper, nickel, lead, and gold, among other metals. Copper electrorefining, for instance, is crucial for producing high-purity copper used in electrical wiring and electronics. The process allows for the recovery of valuable byproducts from the anode sludge, such as precious metals, which adds to the economic viability of electrorefining. The purity of the final product can be very high, often exceeding 99.9%.