Iron Recovery from Turkish and Romanian Bauxite Residues Through Magnetic Separation: Effect of Hydrothermal Processing and Separation Conditions

This study investigates the potential of two low-iron-grade bauxite residue (BR) samples, containing up to 27.4 wt.% Fe and originating from alumina plants in Romania and Turkey, for the recovery of iron concentrate via wet magnetic separation. The methodology involved the hydrothermal reduction of the residues, aiming to transform the hematite/goethite (Fe3+) phases into magnetite (Fe2+/Fe3+) and enhance their magnetic susceptibility. The effect of hydrothermal treatment, magnetic induction value (up to 1600 Gs), and slurry dispersion on iron recovery and iron grade were investigated. An optimum magnetic fraction was obtained, containing 44.4 wt.% elemental iron (Feelem) and achieving 98% iron recovery. These results demonstrate a significant improvement compared to the magnetic fraction derived from the respective non-reduced sample, which showed a maximum of 29.7 wt.% Fe grade and 59.7% recovery. Furthermore, silicon and sodium are primarily distributed in the non-ferrous fraction. The application of sonication to enhance slurry dispersion during magnetic separation did not have a positive impact on the process. In addition to iron recovery, an aspect of considerable potential is the reutilization of the Al-rich liquor generated during hydrothermal treatment of the BR. Its reintroduction into the Bayer process circuit could contribute to improved material utilization and enhanced overall process efficiency.