Effect of surface roughness on the detachment between bubble and glass beads with different contact angles

Abstract

Surface roughness plays a critical role in flotation, as it has a marked impact on bubble-particle interaction, i.e., attachment and detachment. In the present study, the effect of surface roughness on the detachment between bubble and glass beads with different contact angles was investigated using a home-built system for measuring bubble-particle detachment. By applying a simple harmonic oscillation to a bubble-particle aggregate, the critical detachment force could be calculated from the critical amplitude based on Newton's second law. Smooth and rough glass beads were hydrophobized simultaneously using octadecyl trichlorosilane vapor to ensure that they have the same local contact angle in parallel experiments. The results show that the detachment force of a smooth particle was higher than that of a rough particle when the local contact angle with the particle surface was below 90° (hydrophilic). However, the detachment force of a rough particle was higher than that of a smooth particle when the local contact angle was above 90° (hydrophobic). Surface roughness rendered the hydrophilic bubble-particle aggregate less stable while hydrophobic bubble-particle aggregate more stable. The decrease in apparent contact angle and contact line length decreased the detachment force of the hydrophilic particles, while an increase in these parameters increased the detachment force of the hydrophobic particles.