Increasing Iron Recovery from High-Iron Red Mud by Surface Magnetization

Economical recovery of iron from high-iron red mud will benefit the comprehensive utilization of the mud, but current practice is restricted by poor magnetism and mutual embeddedness of ultrafine iron-bearing minerals. This work determined the effect of surface magnetization on iron recovery from ultrafine goethite and red mud by magnetic separation. Surface magnetization was carried out on ultrafine goethite with poor magnetism. Increasing the temperature and NaOH concentration remarkably improved the iron recovery, whereas prolonging magnetization time reduced the iron recovery. For high-iron red mud, the total iron (TFe) content in concentrates and iron recovery initially increased and then decreased with increasing NaOH concentration and FeSO4 concentration. Coarse red mud was beneficial to increasing the TFe content and iron recovery after surface magnetization. A 28.52% iron recovery efficiency with 40.90% TFe was achieved in the concentrate without surface magnetization, whereas a 66.02% iron recovery efficiency with 56.7 wt% TFe was obtained in the concentrate by magnetic separation under surface magnetization conditions of 0.6 mol/L NaOH and 0.02 mol/L Fe2+ at 80 degrees C for 10 min. The increased iron recovery and TFe in the concentrate after magnetic separation was mainly attributed to the formation of magnetite Fe3O4 on the surface of iron-bearing minerals during surface magnetization.