Mechanism and research progress of the bubble-particle attachment in flotation

The interaction process between particles and bubbles can be classified as collision, attachment, and detachment; all three sub-processes determine the collection probability between particles and bubbles. Upon collision, the hydrophobic particles strongly attach to the rising air bubbles, which carry them to the surface, thereby overflowing the flotation cell in the collecting launder. Hydrophilic particles unattached to the rising air bubbles are left to settle at the bottom of the cell to be discharged. Whether the target mineral particles can attach to the rising air bubbles is the key to froth flotation. Therefore, studying bubble-particle attachment to improve the flotation efficiency is quite significant. The bubble-particle attachment probability model, EDLVO theory, force analysis of the bubble-particle aggregate, influence factors, and experimental progress of the bubble-particle attachment were systematically analyzed. Based on the methods of contact time, induction time, and energy barrier, the adhesion probability model was analyzed from the perspectives of dynamics and thermodynamics, and the effect of particle size, bubble size, particle hydrophobicity, particle surface roughness, and pH values on adhesion probability were explained. The force analysis of the bubble-particle aggregate under quiescent and turbulent conditions was conducted. Typically, there exist three types of attachment forces of the bubble-particle aggregate:capillary force, hydrostatic pressure force, and buoyancy force. The weight force is the only detachment force of the bubble-particle aggregate in the quiescent condition, but the vibration and centrifugal forces are also detachment forces in the turbulent condition. Many researchers have conducted substantial research on particle-bubble adhesion using advanced instruments and detection means, and have made several research achievements. However, because bubble-particle interaction is extremely complicated, the interaction conditions are simplified during experimental study. Therefore, the attachment process is not satisfactorily described by the available theory. Combined with practical application demands, a bubble-particle study should be conducted from a deeper and more comprehensive level.