Effect of applied voltage on electroreduction with controlled oxygen flow of molten slag containing FeO at 1 723 K

Abstract

This paper reports on electroreduction with controlled oxygen flow (COF) for extraction of iron along with oxygen by-product from molten slag containing FeO at 1 723 K. An electrolytic cell with COF was constructed by a cathode and a porous platinum anode sintered on a one-end-closed magnesia partially stabilized zirconia based solid electrolyte tube. The process for electroreduction with COF was analyzed. Effect of applied voltage on electroreduction behavior of FeO in SiO2-CaO-Al2O3-MgO molten slag with iron rod serving as cathode was investigated by means of the linear sweep and the potentiostatic electrolysis. The possibility of zirconia membrane as conductive noncorrosive anode material was also discussed. The results show that decreased oxygen partial pressure in anode atmosphere can contribute to lower decomposition voltage of FeO in molten slag. Higher applied voltage results in better effect of FeO electroreduction. Electrolytic product can be pure iron with dendrite or ferrosilicon alloy based on applied voltage. Besides, the phase transformation of zirconia grain and the slag penetration can lead to an increase of electronic conductivity of the zirconia membrane. The corrosion of the molten slag to the zirconia membrane during electrolysis is evidently aggravated by large the applied voltage. In order to obtain pure iron and minimize the corrosion of the molten slag to the zirconia membrane under this condition of experimentation, the applied voltage of 1.5 V is preferred.