The self-carrier effect of hematite in the flotation

Finely disseminated iron ores are a type of refractory iron ores that exist in many regions in China, where fine grind is essential to liberate iron minerals from gangue. The flotation process of fine particles is plagued with losses of recovery and selectivity, which are due to the low collision efficiencies of fine particles with bubbles, mechanical/hydraulic entrainment, and high specific surface area. Carrier flotation, which is based on the carrier effect of coarse particles, is one of the effective methods for fine particle flotation. However, scarce information is available in the literature with regard to the " self-carrier” effect and mechanism of coarse hematite particles during flotation, which are necessary and beneficial for the efficient utilization of refractory iron ore resources. In this paper, micro-flotation test, optical microscopy analysis, E-DLVO theory calculations, and particle aggregation kinetics were used to study the self-carrier effect of hematite flotation in the sodium oleate system. Flotation results show that the recovery of coarse hematite (−106 + 45 μm) could be up to 90% when the sodium oleate concentration is over 15 mg·L⁻¹. However, for fine hematite (−18 μm) particles, the flotation recovery and flotation rate are relatively low. The highest recovery of fine-coarse hematite mixtures is obtained when the fine and coarse hematite are approximately equal in mass ratio, thereby indicating that the self-carrier effects are strongest; meanwhile, the improvement of coarse particles for flotation recovery gradually weakens with excessive coarseness in the mixtures. Optical microscopy analysis and E-DLVO theory calculations show that the interaction energies and aggregation tendencies between fine and coarse hematite particles are stronger than those among the fine hematite particles, which might be the main reasons that coarse particles could enhance the flotation performance of fine hematite particles. However, excessive coarse particles could strengthen the grinding/attrition effects during the flotation, thereby possibly weakening the self-carrier effects of coarse particles and resulting in decreased flotation recovery.