Selective separation of iron and scandium from Bayer Sc-bearing red mud

Abstract

In this study, we investigated the separation of iron and scandium from Sc-bearing red mud. The red mud object of our study contained 31.11 wt% total iron (TFe), 0.0045 wt% Sc, hematite (Fe2O3) and ferrosilite (FeO·SiO2) as the main Fe-bearing minerals. The Sc-bearing red mud was treated by a novel deep reduction roasting and magnetic separation process that includes the addition of coke and CaO to extract Fe and enriching Sc from the Sc-bearing red mud. The addition of coke and CaO enhances the transformation of hematite (Fe2O3) to metallic iron (Fe0) and magnetite (Fe3O4) as well as the transformation of ferrosilite into metallic iron (Fe0). The test results show that utilizing the new process a Fe concentrate with a TFe content of 81.22 wt% and Fe recovery of 92.96% was obtained. Furthermore, magnetic separation tailings with Sc content of 0.0062 wt% and Sc recovery of 98.65% were also obtained. The test results were achieved under the following process conditions: roasting temperature of 1373 K, roasting time of 45 min, calcium oxide dosage of 20 wt%, coke dosage of 25 wt%, grinding fineness of 90% < 0.04 mm, and magnetic field intensity of 0.24 T. The major minerals in the Fe concentrate are metallic iron (Fe0) and magnetite (Fe3O4). The main minerals in the magnetic separation tailings with a low TFe content of 2.62% are CaO·SiO2, Na2O·SiO2, FeO·SiO2, Ca3Fe2Si3O12, CaAl2SiO6 and CaFe(SiO3)2.