Investigation of Low-Temperature Molten Oxide Electrolysis of a Mixture of Hematite and Zinc Oxide

To develop a CO2-free process for recovering Fe and Zn metals from electric arc furnace (EAF) dust, this study investigated the molten oxide electrolysis of Fe2O3 – ZnO mixtures in a B2O3 – Na2O electrolyte. Electrolysis was conducted using an Fe cathode and a Pt anode at 1173 K with different ratios of Fe2O3 to ZnO by applying cell voltages determined based on thermodynamic calculations and cyclic voltammetry measurements. When electrolysis was conducted at a cell voltage of 1.1 V, selective reduction of Fe oxide to Fe metal was observed without the reduction of ZnO. However, when 1.6 V was applied, the co-reduction of Fe oxide and ZnO to the Fe – Zn alloy was observed. In the vacuum distillation of the Fe – Zn alloy at 1000 – 1200 K, Zn metal with a purity exceeding 99.996 % was obtained with a recovery efficiency above 99.9 %, under certain conditions. These results demonstrate the feasibility of recovering Fe and Zn from EAF dust using low-temperature molten oxide electrolysis and subsequent vacuum distillation.