Magnetic separation of hematite and limonite fines as hydrophobic flocs from iron ores

Magnetic separation of weakly magnetic iron mineral fines in the form of flocs, which is termed Floc Magnetic Separation (FMS) process, has been studied in the present work, in order to find a substitution for high-intensity or high-gradient magnetic separators to treat the ores with weakly magnetic iron minerals in the fine size range. This study was performed on a hematite ore and a limonite ore that were finely ground to be micron particles, through the hydrophobic flocculation induced by sodium oleate and kerosene to make flocs. The experimental results have shown that the FMS process is effective to recover hematite and limonite fines at a middle magnetic field intensity, greatly increased the separation efficiency, compared with the conventional magnetic separation at the same conditions. By applying the process to the fine hematite ore containing 30.5% Fe, a concentrate assaying 64% Fe with 82% recovery has been produced. It has been found that the separation efficiency of the FMS process closely correlates with the main parameters of hydrophobic flocculation such as sodium oleate addition, conditioning time and kerosene addition. This finding suggests that the high efficiency achieved by the FMS process might be attributed to the considerable increase of the magnetic force on the iron mineral fines in the form of hydrophobic flocs in a magnetic field, thus the fines can be held by the separation plates in a magnetic separator and then be collected as magnetic concentrates. (C) 2002 Elsevier Science Ltd. All rights reserved.