Bubble-Particle Interaction Measured by Atomic Force Microscopy

Abstract

Interaction forces between solid particles and air bubbles during flotation are of significant academic and practical importance. An atomic force microscope (AFM) probe technique was used to measure the interaction forces between an air bubble and a hydrophobic/hydrophilic spherical particle. In the case of hydrophobic spheres, strong attraction between the surfaces, leading to the rupture of the intervening water film and the attachment of the particle to the air bubble was observed. In the case of hydrophilic spheres, the rupture of the intervening water film and the attachment of the particle to the air bubble did not take place. In each case, however, the repulsive interaction force during approach prior to attachment was dependent on the speed of the bubble (the piezoelectric translator) indicating that the hydrodynamic interaction between the bubble and the particle at short separation distances is significant. The force analysis together with the deformation of the gas-liquid interface during the interaction is described, which gives a more detailed description of the bubble-particle interaction. The outcome of this research increases our understanding of the flotation separation process.