Characterization - bauxite residue

Manuscritp published in Mining, Metallurgy & Exploration journalA new step in the Bayer process has been used to recover NaOH and to reduce its content in red mud. After digestion, the residue is separated from the Bayer liquor and goes through press filters, which enables the recovery ofNaOH and decreases the moisture content. It is well known that red mud is one ofthe most important sources ofscandium. For this reason, the goal ofthis workwas to characterize a Brazilian red mud (BRM) for scandium recovery. The sample was collected after the press filter system process. Analysis ofenergy-dispersive X-ray fluorescence (EDXRF), scanning electron microscopy/energy-dispersive X-ray spectrosco- py (SEM/EDS), and X-ray diffraction (XRD) was performed. Microwave digestion using an acid mixture was carried out to determine the concentration ofthe main elements. Fe2O3 represented 40% ofthe BRM, and the Sc concentration was 43 mg/kg. The SiO2 content was 24%,which is the highest value found in the literature, whereas the sodiumconcentration was the lowest. A literature review was carried out to compare results with BRM, as well as the current studies for recovery of scandium by the leaching/ion-exchange process. Scandium recovery using a leaching/ion exchange process may be possible with efficiency higher than 90%. The greatest challenge is the occurrence of silica gel formation during leaching.