Experimental study on effect of surfactant and solution property on bubble rising motion

Bubbly flows are frequently run into in industrial processes. Since liquid phases usually contain impurities, bubble interface is polluted to a certain degree. This can affect flow structures, and heat and mass transfer properties at bubble interface, leading to a significant effect on industrial efficiencies. Therefore, it is important to study the hydrodynamic characteristics of polluted bubbles. It was experimentally investigated on the effects of surfactant concentration, ionization and solvent polarity on bubble shape, rise trajectory and velocity using a high-speed camera in this paper. The present studies show that the addition of a very small amount of non-ionic surfactants (1-OA) into a polar solution (a 56% glycerol-water solution) can cause a great change in bubble rise trajectory (an inhibition of about 80% in bubble lateral migration) and a decrease in bubble rise velocity (a decrease of about 25% in bubble maximum velocity) because surfactant molecules adsorbed at bubble interface gather tightly. However, the addition of ionic surfactant (SDS) with the same concentration into a polar solution cannot cause a significant change in bubble rise trajectory and rise velocity because the distribution of surfactant molecules adsorbed at bubble interface is relatively loose due to an electrostatic effect. The addition of surfactants into a non-polar solution (Dimethyl silicone oil) cannot obviously change the above parameters due to the non-solvent effect of surfactants in non-polar solutions. Namely, surfactant molecules cannot be adsorbed at bubble interface.(c) 2023 Elsevier B.V. All rights reserved.