Recovery of iron from high-iron red mud using suspension magnetization roasting and magnetic separation

Abstract

• Suspension magnetization roasting and magnetic separation process treat red mud effectively. • Alumogoethite [Al x Fe (1- x ) ]OOH transformed into Fe-Al spinel phase Fe(Al,Fe) 2 O 4 . • Al-containing magnetite combined part of Fe(Al, Fe) 2 O 4 enter into the iron concentrate. • The saturation magnetization and specific magnetic susceptibility are enhanced via magnetization roasting. An innovative suspension magnetization roasting followed by magnetic separation process was developed to recover iron from high-iron red mud (HIRM), and the effects of roasting temperature, roasting time, CO concentration and grinding fineness on the recovery of iron were investigated. Under the optimized conditions, determined to be a roasting temperature of 560 ℃, reaction time of 15 min, CO concentration of 30% and total gas-flow rate of 500 mL/min, an iron concentrate assaying 55.44 wt% Fe with an iron recovery of 89.34% was prepared by magnetic separation. X-ray diffraction, chemical phase analysis, vibrating sample magnetometer, and scanning electron microscope were employed to assess the characteristics of red mud, roasted sample and magnetic separation products. The hematite in the red mud was transformed into magnetite during the suspension magnetization roasting, thus the magnetism was significantly enhanced. While, the alumogoethite was transformed into Fe-Al spinel phase Fe(Al,Fe) 2 O 4 , and entered the magnetic concentrate along with the magnetite. In addition, some fine-grained alumina particles were also easy to be wrapped by magnetic agglomerates and entered the magnetic concentrate, resulting in high aluminum content in the iron concentrate.