Influence of dewetting kinetics on bubble–particle interaction

Abstract

Bubble–particle dewetting kinetics relevant to froth flotation was experimentally studied on a modelled system using a CCD high-speed video microscopy. The experimental system included a gas–liquid interface formed at the bottom of a glass capillary filled with either deionized Milli-Q water or a solution of dodecylamine chloride (DAC) and hydrophobic glass beads dropping onto the interface in the solution inside the capillary under gravity. The dewetting process was observed underside the gas–liquid interface with a metallographic inverted microscope and a CCD high-speed video system operating at about 1000 frames s⁻¹ for imaging the dewetting process. The velocities of the dewetting process showed a maximum in the pH-domain where the flotation recovery also showed a maximum. This good correlation between the dewetting kinetics and flotation recovery indicates that the dewetting kinetics is equally necessary as the thinning and rupture of the intervening liquid film between bubbles and particles for success of the flotation process. The discussion highlighted the need of developing a better understanding of the particle–bubble contact interaction, in particular, the difference in contact angles on micron-sized particles and flat surfaces.