Patent attributes
A cell for electrowinning a metal, in particular aluminium, from a compound thereof dissolved in an electrolyte (30) comprises an anode (40) and a cathode (10,11) that contact the electrolyte (30), the cathode (10,11) being during use at a cathodic potential for reducing thereon species of the metal to be produced from the dissolved compound. The electrolyte (30) further contains species of at least one element that is liable to contaminate the product metal (20) and that has a cathodic reduction potential which is less negative than the cathodic potential of the metal to be produced. The cell further comprises a collector (50) for removing species of such element (s) from the electrolyte (30). During use the collector (50) is at a potential that is: less negative than the cathodic potential of the produced metal (20) to inhibit reduction thereon of species of the metal to be produced; and at or more negative than the reduction potential of the species of said element(s) to allow reduction thereof on the collector (50). The cell is so arranged that species of said element(s) are reduced on the collector (50) rather than on the cathode (10,11) so as to inhibit contamination of the product metal (20) by said element(s).
