Latest advances and progress in microbubble flotation of fine minerals: Microbubble preparation, equipment and applications

In the past few decades, microbubble flotation has been widely studied in the separation and beneficiation of fine minerals. Compared with conventional flotation, microbubble flotation has obvious advantages such as high grade and recovery, and low consumption of flotation reagents. Hereby, we systematically review the latest advances and research progress in the flotation of fine mineral particles by microbubbles. In general, microbubbles are characteristic of small bubble size, large specific surface area, high surface energy, good selectivity, and are easy to attach to the surface of hydrophobic particles or large bubbles, greatly reducing the detaching probability of particles from bubbles. Microbubbles can be prepared by pressurized aeration and dissolved air (PADA), electrolysis, ultrasonic cavitation, photocatalysis, solvent exchange, temperature difference method (TDM), venturi tube and membrane method, etc. Correspondingly, equipment for fine particle flotation is categorized as microbubble release flotation machine, centrifugal flotation column, packed flotation column, and magnetic flotation machine, etc. In practice, microbubble flotation has been widely studied in the beneficiation of ultrafine coals, metallic minerals, non-metallic minerals, and exhibited superiority than the conventional flotation machine. Mechanisms underpinning the promotion of fine particle flotation by nanobubbles include the agglomeration of fine particles, the high stability of nanobubbles in aqueous solution, the enhancement of particle hydrophobicity and flotation dynamics.