How is aluminum produced by reducing alumina through electrolysis?
Aluminum is produced from alumina (aluminum oxide, Al2O3) through an electrolytic process known as the Hall-Heroult process. This method, independently discovered by Charles Martin Hall and Paul-Louis-Toussaint Heroult in 1886, remains the basis for modern aluminum production.1234
The process involves dissolving purified alumina in a molten electrolyte, primarily cryolite (Na3AlF6), within carbon-lined steel reduction pots. A direct current is passed through this electrolyte. The oxygen from the alumina is released at the carbon anode as carbon dioxide, while molten aluminum, being denser than the electrolyte, is deposited at the carbon cathode lining at the bottom of the cell.124
Approximately 2 kg of alumina are consumed for every kilogram of aluminum produced, with about 450 grams of carbon also being consumed. The process is continuous, with alumina being periodically added to maintain the molten bath, which is kept at around 950 °C (1,750 °F) by the electric current. Molten aluminum is then siphoned off from the cells.1