Processing Red Mud Produced at the Eti Alüminyum A.Ş. Seydişehir Alumina Refinery to Recover Gallium and Vanadium and Obtain Iron Oxide Pigments

Abstract

It is demonstrated that Bayer–hydrogarnet technology can be developed and applied to process red mud for separating important components such as Na₂O, Al₂O₃, Ga₂О₃, and V₂O₅ and for obtaining iron oxide pigments from hydrogarnet mud, a product of autoclave leaching of red mud. The process consists of the autoclave leaching of red mud in the presence of lime to produce hydrogarnet mud (3CaO⋅Fe₂O₃ (Al₂O₃)⋅2SiO₂⋅2H₂O) as a low-alkaline (0.35% Na₂O) precipitate and recover important components into the solution: 98.5% Na₂O, 65.3% Al₂O₃, 55.5% Ga₂О₃, and 65.8% V₂O₅. As a result of the treatment, almost all of the alkali and most of the aluminum that were contained in the red mud return to alumina production. Further treatment of the leach solution by step precipitation and carbonation also shows that the solution can be used to recover Ga₂О₃ and V₂O₅ into a collective concentrate containing 1.58 wt % Ga₂O₃ and 27.3 wt % V₂O₅. A fine (0.17-μm) red-brown fraction (54% of the mud) is separated from the hydrogarnet mud and it can be used as an iron oxide pigment. Mössbauer spectroscopy determined the nature of the color of the fraction, which simultaneously contains iron in several oxidation states.