Bubble adhesion onto the hydrophobic surface in solutions of non-ionic surface-active agents

Abstract

Bubbles and drops are entities of enormous practical interest since their interfaces are encountered in numerous industrial processes. Froth flotation is just one of the examples in which bubble–particle attachment and especially fast bubble adhesion play a vital role. This work is focused on the experimental study of the three-phase contact (TPC) line expansion during the bubble adhesion onto the hydrophobic surface in solutions of three non-ionic surface-active agents (Terpineol, Triton X-100 and pentaethylene glycol monododecyl ether), which differ in their structure. The diameters of the TPC line together with bubble dynamic contact angles, dynamic surface tension, bubble rising velocity and dynamic drop contact angles were measured. It was confirmed that the bubble adhesion is fast in solutions of such surfactants whose hydrophobic and hydrophilic parts are small. On the other hand, surfactants with long and flexible hydrophobic tails exhibit more complex behaviour which usually leads to slower bubble adhesion. The molecule steric orientation in the proximity of the interface strongly influences the surfactant motion and thus the predictability of bubble attachment efficiency is low.