Enhanced removal of iron minerals from high-iron bauxite with advanced roasting technology for enrichment of aluminum

Abstract

High-iron bauxite, which is a typically unmanageable form of bauxite due to its high contents of iron and diaspore, has not been used by alumina producers. An advanced roasting technique for removing iron from high-iron bauxite, based on static pre-roasting in air and suspension roasting by hydrogen under fluidized conditions followed by magnetic separation was developed in this study. The influences of pre-roasting temperature, suspension roasting temperature, roasting time, and H2 concentration were investigated. The phase transformations of the samples were investigated using X-ray diffraction, vibrating sample magnetometry, field emission scanning electron microscopy, and Brunauer-Emmett-Teller method. After pre-roasting at a temperature of 750 °C for 30 min, diaspore (AlOOH) and goethite (FeOOH) in the raw high-iron bauxite ore were transformed into Al2O3 and Fe2O3, respectively. The optimal suspension roasting conditions were determined to be a roasting temperature of 600 °C with a H2 concentration of 25% for 4 min. The reduction sample was subjected to magnetic separation and a non-magnetic product (aluminum concentrate), with alumina recovery of 80.64% and iron removal of 85.32%, was obtained. Such a non-magnetic product could be used as a raw material for the Bayer process in the alumina production industry, while the magnetic product could be used as a supplementary material for iron ore resources.