Recovery of iron and alumina from iron–aluminum symbiotic ore via low–calcium carbothermal reduction

Abstract

The iron-aluminum symbiotic ore, as an important strategic resource, has not been utilized due to the complex relationship between iron-aluminum minerals. In this work, a low-calcium carbothermal reduction method was proposed to treat the iron-aluminum symbiotic ore, and its performance and reaction mechanism were studied based on the Fe2O3-Al2O3-SiO2-CaO-Na2O system using XRF (X-ray fluorescence), XRD (X-ray diffractometer), SEM-EDS (scanning electron microscopy and energy dispersive spectrometer), VSM (vibrating sample magnetometer) and XPS (X-ray photoelectron spectroscopy), while the practical application on the iron–aluminum symbiotic ore was verified. The silicon is in the form of sodium calcium silicate compound during the low–calcium carbothermal reduction process, and the formation sequence of this compounds is Na2Ca3Si2O8 → Na2Ca2Si2O7 → Na2CaSiO4 with the increase of Na2CO3 amount. The iron- and aluminum-bearing phases in the reduction product are Fe, NaAlO2 and a small amount of ferrous and ferric compounds, NaAl11O17 and NaAlSiO4. Fe can be aggregated in the iron concentrate via magnetic separation and NaAlO2 can be recovered by leaching process. The main minerals in the reduction product from the iron-aluminum symbiotic ore obtained by the low-calcium reduction process are Fe, NaAlO2, Na2CaSiO4 and NaAlSiO4, and the iron metallization efficiency, the leaching efficiency of Al2O3 and the content of iron in the concentrate are 84.24%, 86.07% and 75.70% respectively under the optimal reduction conditions.