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, termed the Floc Magnetic Separation (FMS) process, has been investigated to identify an alternative to high-intensity or high-gradient magnetic separators suitable for treating ores with weakly magnetic iron minerals in fine size ranges. In this study, hematite and limonite ores were finely ground into micron-sized particles, and hydrophobic flocculation was induced using sodium oleate and kerosene to create flocs. The experimental results demonstrated that the FMS process effectively recovered hematite and limonite fines at a moderate magnetic field intensity, significantly increasing separation efficiency compared to conventional magnetic separation under identical conditions. When applied to fine hematite ore containing 30.5% Fe, a concentrate yielding 64% Fe with an 82% recovery rate was obtained. It was discovered that the efficiency of the FMS process is closely linked to primary hydrophobic flocculation parameters, including sodium oleate addition, conditioning time, and kerosene addition. This finding indicates that the enhanced efficiency achieved by the FMS process may be attributed to the substantial increase of the magnetic force acting on the iron mineral fines present as hydrophobic flocs within a magnetic field, facilitating their retention on separation plates in a magnetic separator for collection as magnetic concentrates.