Production of electrolytic iron from red mud in alkaline media

Abstract

In this study, the feasibility of producing electrolytic iron from red muds in a strongly alkaline medium at 110 °C was studied. The red mud samples from a French industry were characterized by various techniques (ICP-AES, SEM, XRD) to determine their chemical and mineralogical compositions. The main phase in the red mud investigated was hematite (α-Fe2O3). Iron electrodeposition tests from red mud suspended in a 12.5 mol/L NaOH electrolyte were conducted at constant current in a stirred electrochemical cell. The solid:liquid ratio and amounts of impurities contained in red mud were varied to optimize the faradaic yield and the production rate of electrolytic iron. Whereas hematite can be reduced to iron with a current efficiency over 80% for a current density (cd) up to 1000 A/m2, the current efficiency with red muds was highest for a cd below 50 A/m2 and then decreased regularly to 20% at 1000 A/m2. In all cases, the deposit produced contained more than 97% metal iron. The moderate performance of the process investigated with red mud was attributed to a troublesome adsorption of red mud particles on the cathode, making the reduction far less efficient than that with hematite.