EFFECT ON SURFACE-CHARGES OF BUBBLES AND FINE PARTICLES ON AIR FLOTATION PROCESS

The adhesion of fine particles onto bubbles in flotation was studied on the basis of surface charge measurements of the bubbles and particles. The surface charges of the bubbles were measured by the use of a micro‐electropheresis apparatus devised in our previous study and the mechanism of the bubble charging was studied under various experimental conditions. In distilled water, the bubbles were negatively charged and the iso‐electric point appeared at pH = 2.5. The surface charges of the bubbles in the surfactant solution were determined by the surfactant molecules adsorbed at the surface and depend strongly on the values of pH. The flotation efficiency of latex particles (0.923 μm) was found to be strongly influenced by the surface charges of both the particles and the bubbles. The force between the particle and the bubble was estimated from the observation of the particle attachment to the bubble surface, and a simple equation including the effects of the hydrodynamic and surface charge interactions was proposed to determine the floatability limit. Copyright © 1990 Canadian Society for Chemical Engineering