Effect of surface hydrophobicity on the bubble-substrate collisional interaction process and interaction force

Abstract

Investigating the collisional interaction process and interaction forces between bubbles and substrates can enhance the comprehension of the bubble-particle collision and adhesion process in flotation. In this study, the collisional interaction processes between bubbles and various hydrophobic glass surfaces were studied, and the interaction forces were directly measured by a high-sensitive microbalance system. The results demonstrated that surface hydrophobicity has a negligible effect on the collision process, evidenced by the same velocity variation and the same number of collisions on different hydrophobic surfaces. In terms of adhesion behavior, it was observed that the adhesion area of bubbles increased substantially and the induction time decreased significantly with the increase in surface hydrophobicity, indicating that bubbles are more likely to adhere to hydrophobic surfaces. This phenomenon is consistent with the measurement of interaction forces, where higher adhesion force and pull-off force can be measured on hydrophobic surfaces. Meanwhile, with increasing surface hydrophobicity, the “jump-in” adhesion was more significant, and detachment was more difficult. To clarify the specific force variation during the interaction, the interaction forces were calculated theoretically at critical positions and compared to the measured value. It was found that they are consistent, and both capillary force and Laplace force increased with increasing surface hydrophobicity. These findings demonstrate that bubbles experience stronger attraction and adhere more strongly to hydrophobic surfaces.