Enhancement of selective fine particle flotation by microbubbles generated through hydrodynamic cavitation

The flotation of fine particles less than 50 μm is challenging for the mining industry. By using hydrodynamic cavitation, a significant improvement on the recovery of fine particles has been found. This study aims to investigate the effect of hydrodynamic cavitation on the selective flotation of fine particles from detailed mechanism. Our single-bubble flotation results indicated that the bubble-particle collection efficiencies of fine silica particles (D50 = 6 μm and D50 = 16 μm) improved after hydrodynamic cavitation, especially for hydrophobized silica particles. The improved flotation performance of fine particles was investigated from three perspectives: (1) By zeta potential distribution measurements, bubble-frosting on hydrophobic particles was demonstrated after hydrodynamic cavitation. (2) The formation of large aggregates of hydrophobic fine particles after cavitation was revealed by slurry turbidity and particle size measurements, potentially contributing to the improved collision efficiency of the fine particles due to the bridging effect provided by microbubbles. (3) The attachment efficiency between a solid surface and flotation bubbles was enhanced if the surface was covered with hydrodynamic cavitation-generated microbubbles. Compared to the hydrophilic particles, the hydrophobic particles benefited from the hydrodynamic cavitation from the perspectives of bubble frosting, particle-bubble collision efficiency and attachment efficiency. Based on this study, it is expected that the separation efficiency for fine hydrophilic and hydrophobic particles can be improved by hydrodynamic cavitation.