Effect of solid material and surfactant presence on interactions of bubbles with horizontal solid surface

The interaction of a bubble with an immersed horizontal solid surface is studied experimentally. The effect of presence of a surfactant (limited to a specific nonionic surfactant, α‐terpineol, of various concentrations) and of surface material (cleaned glass, polypropylene, polyethylene, and Teflon) is investigated. The study focuses on two particular stages of the interaction, (i) the process of bubble bounce, which includes a collision and subsequent rebound from the solid surface, and (ii) the bubble attachment, which occurs after collision in time much longer than the duration of bounce and also after disappearance of all visible bubble movement. It is observed that the effect of the surface material on the bouncing is minor, possibly due to the liquid film separating the bubble and the solid surface. The presence of surfactant significantly affects the bouncing process. It not only decreases the initial bubble velocity, but also diminishes the bubble deformation after the collision and suppresses the bubble rebound from the surface. No rebound from the surface is observed in the most concentrated (1 × 10−3 mol/L) α‐terpineol solution. The adhesion time depends both on the solid material and α‐terpineol concentration. If the α‐terpineol concentration is increased, the adhesion time increases in the case of polypropylene surface, while it decreases in the case of polyethylene and Teflon surfaces. Results of this study are relevant for the description of attachment mechanism and to determine the proper conditions for selective flotation of plastics.