Patent ID: 7846309

Claim:
A cell for electrowinning a metal from a compound thereof dissolved in a molten salt electrolyte, the cell containing said molten salt electrolyte in which a compound of said metal is dissolved, in particular for electrowinning aluminium from alumina dissolved in the molten electrolyte, said cell comprising an anode and a cathode that contact the molten electrolyte, the cathode being during use at a cathodic potential for reducing thereon species of the metal to be produced from the dissolved compound, the electrolyte further containing species of at least one element that is liable to contaminate the product metal and that has a cathodic reduction potential which is less negative than the cathodic potential of the metal to be produced, wherein the cell further comprises a collector for removing species of said element(s) from the electrolyte, said collector having an electrically conductive surface in contact with the molten electrolyte, the conductive collector surface being during use at a potential that is: less negative than the cathodic potential of the produced metal 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 conductive collector surface, the cell being so arranged that species of said element(s) are reduced on the conductive collector surface rather than on the cathode so as to inhibit contamination of the product metal by said element(s).