Disc Magnetic Separator Applied to the Extraction of Magnetite in Bauxite Residue

摘要

The valorization of bauxite residue generated by the Bayer process is a major challenge for the alumina industry, for both economical and environmental reasons. Iron oxides, mainly goethite and hematite, are major constituents of bauxite residue that also have a potential economic value. Many attempts have been reported in the literature, of reducing these species to magnetic iron oxides, such as magnetite, followed by its recovery using magnetic separation. No commercial success has however been reported to date. The initial steps of our detailed study, undertaken on the magnetic separation process to extract the iron compounds from calcined bauxite residue, have shown that a basic magnetic separator cannot recover the magnetite content. A homemade lab-scale disc magnetic separator has been fabricated and the influence of key parameters, such as solids concentration, feed flow rate, rotational speed, etc., was quantified. However, regardless of the equipment performance, the results are highly dependent on the material submitted to magnetic separation. In order to properly evaluate the various parameters' influence, and the efficiency of the separation process, an ideal mixture of magnetic material (magnetite) and non-magnetic material ("as is" bauxite residue) was prepared and submitted to the disc magnetic separator. The collected material is enriched to more than 90 wt% magnetic content, from an initial 30 wt%.