How is electrolysis used in metal refining?

Electrolysis is used in metal refining to separate pure metal from impurities by passing an electric current through a solution.

In the process of electrolysis for metal refining, an electric current is passed through a solution, or electrolyte, which contains the metal ions. This is typically done in an electrolytic cell, which consists of two electrodes: the anode (positive electrode) and the cathode (negative electrode). The metal ions are attracted to the cathode, where they gain electrons and are reduced to form pure metal atoms.

The impurities, which are not attracted to either electrode, settle at the bottom of the electrolytic cell as an 'anode sludge'. This sludge can be further processed to extract any valuable metals. The electrolyte is usually a solution of the metal salt or a molten metal salt. For example, in the electrolytic refining of copper, the electrolyte is a copper sulphate solution.

The process of electrolysis is highly effective in refining metals as it allows for a high degree of purity. The metal produced at the cathode is often 99.9% pure. This is because the impurities do not receive electrons and are not deposited at the cathode.

In addition to refining, electrolysis is also used in the extraction of some metals from their ores. For instance, aluminium is extracted from its ore, bauxite, using electrolysis. The process of electrolysis is a key part of the industrial production of many metals, and understanding it is fundamental to the study of IGCSE Chemistry.