Novel method for iron recovery from hazardous iron ore tailing with induced carbothermic reduction-magnetic flocculation separation

Abstract

In this paper, a novel method to recover iron from iron ore tailing (IOT) was studied. The method was induced with carbothermic reduction, followed by magnetic flocculation separation (MFS) and conventional magnetic separation (CMS). The effects of reduction temperature, as well as the amount of coal and sodium carbonate on iron recovery efficiency, were chiefly introduced according to the experimental mechanism. Results of carbothermic reduction showed that iron minerals in the IOT were transformed to metallic iron at the reduction temperature of 1100 °C for 120 min, with a C/Ore mass ratio of 25% and a mass ratio of Na2CO3 to ore of 8%. The reduction activity of FeO increased and a deep reduction from FeO to metallic iron was observed with the addition of Na2CO3. The metallization mean of induced reduction ores reached 32.53%. Results of magnetic separation showed that the MFS concentrate grade was 74.02% Fe, with the recovery rate at 79.51% when the reduced samples were ground to 87.4% below 38 μm. This iron recovery increased by 4.19% compared with that of CMS, whereas the iron concentrate grade slightly changed. In addition, the microstructure and phase transformation of the carbothermic reduction process were studied by X-ray powder diffraction, scanning electron microscope, and energy-disperse spectroscopy, thereby complying with the main force analysis of magnetic flocculation in the MFS to help understand the mechanism of the novel method.