Composition and Properties of Iron Oxides in the Products of Hydrothermal Treatment of Red Mud and Bauxites

Bauxites and red mud (RM) from alumina production facilities are distinguished by high contents of iron compounds and can be regarded a promising feedstock for magnetite production. The hydrothermal treatment of bauxites from the Severouralsk Bauxite Mine (SBM), red mud (RM), and hematite in an alkaline medium in the presence of FeSO4 or metal (Al, Fe, Ca, Mg, or 0.25Mg–0.25Al–0.5Fe) powders promotes the formation of magnetite in the products. The hydrothermal treatment parameters were dictated by bauxite leaching parameters at the production facility to provide high aluminum recovery. X-ray diffraction analysis, scanning electron microscopy, and magnetic measurements showed that the treatment of red mud in the presence of FeSO4 or metallic Al yielded highly disperse materials containing 32.4% or 23.7% Fe3O4, respectively. The presence of Fe or 0.25Mg–0.25Al–0.5Fe mixed powders in bauxite leaching provided for 40.8 or 67.9% Fe3O4, respectively, in the form of crystalline particles of sizes up to 5 μm. The higher magnetization values of the products owing to the formation of magnetic phases will ensure their efficient magnetic separation.