Electrowinning of Iron in Aqueous Alkaline Solution Using Rotating Disk Electrode

Abstract

In order to develop a new, efficient industrial process for producing high quality iron and steel with significantly reduced carbon dioxide emissions, we investigated the electrowinning of iron from an iron oxide ore in aqueous alkaline solutions. Hematite (Fe2O3) solid particles suspended in the concentrated aqueous sodium hydroxide (NaOH) solutions were transferred to the cathode (e.g., a rotating disk graphite electrode) and reduced to iron metal by applying a constant current; oxygen was evolved on the anode (e.g., a nickel screen mesh). Current efficiencies of above 90% with respect to iron deposition were consistently obtained under the specific conditions in a laboratory cell, and the corresponding energy consumptions were calculated to be around 3 kWh·kg-1 iron. The deposited iron crystals were the oriented clusters of stacked six-fold twins in a tetrahedron-shape grew growing in a direction perpendicular to the cathode surface. Influences of rotation rates of the cathode, cathodic current densities, contents of the Fe2O3 particles in electrolytes, and concentrations of NaOH solutions on current efficiency and morphology of deposits were studied.