Controlled reduction of red mud by H2 followed by magnetic separation

The current study presents a novel processing approach for the separation of the iron oxide from Red Mud (RM), based on the gentle reduction by hydrogen in static conditions followed by wet magnetic separation. The conversion degree of hematite, initially contained in RM, to magnetite was investigated in relation to reduction time, temperature, and the H2 supply. The maximum achieved conversion reached 87% at 480 °C. The phase transformations during the thermal reduction were investigated via X-ray diffractometry, Mössbauer spectroscopy, electron microscopy, and magnetic measurements. After reduction at the optimal conditions, the reduced RM sample was subjected to magnetic separation and a magnetic fraction with over 54 wt% magnetite concentration was obtained. Such magnetic fractions could be used as a feed in the pig iron industry, while the non-magnetic fraction could be further treated in order to recover the rare earths or to be used as a raw material for building materials.