Exploring particle size effects on magnetic-flotation separation efficiency

Froth flotation, as the most widely applicable mineral beneficiation method, mainly relies on the surface properties (the outermost atomic layers) of fine minerals. Thus, similarity in the surface properties of minerals would be one of the main challenges in their upgrading via flotation separation. As a supplementary of surface properties, magnetic properties are one of the particle characterizations that can be considered in flotation separation. Based on this fact, MAGnetic-FLOtation (MAGFLO), the most recently developed retrofit beneficiation method, has been introduced to improve the flotation upgrading of minerals with magnetic properties. Since this retrofit approach is still in its early stages of development, several factors need to be addressed. The mineral’s particle size is a crucial factor in flotation beneficiation. To fill the gap and better understand interactions within this new technology, different size fractions (−80 and −125 µm) of magnetic and quartz were examined under various conditions (magnetic fields: 6.37, 12.74, and 19.11 mT, always on and on/off 30-second interval magnetic field; and different flotation cells: steel and stainless-steel). Results from over 150 experiments indicated that MAGFLO could significantly depress magnetite particles and achieve high separation efficiency (SE). Vast particle analysis showed that during 3 min of MAGFLO processing, particles did not permanently aggregate. Particle entrapment could be reduced by varying the interval between magnetic field on/off states. Widening the feed particle size could lead to a meaningful reduction in SE, especially in the steel cell (where the SE for −80 and −125 µm was 75% and 67%, respectively). Overall, the results demonstrate that the MAGFLO retrofit concept applies to realistic particle size distributions. However, optimal performance requires a careful balance between field intensity, field application mode, and feed size distribution.