Electrolytic formation of iron from haematite in molten sodium hydroxide

Abstract

Haematite pellets were electrolytically reduced to iron in molten sodium hydroxide at 530°C and recovered to produce iron sponge containing no carbon or sulphur with between 3 and 7 wt-% oxygen which is suitable for re-melt. Most of the residual oxygen will form a slag that can be tapped off. The cell was operated at 1·7 V with a background current density of 65 mA cm^&minus2 and no net consumption of electrolyte. An inert nickel anode was used with the result that the only byproduct in the process was oxygen. The reduction time was 1 h and the cathode current density ∼500 mA cm^&minus2 with a current efficiency of 90%. The purity of the iron was ∼90% wt-% and electrolytic energy consumption was 2·8 kWh kg⁻¹.