Flow Effects on the Surface Properties of Surfactant Foam Films

The surface electrostatic properties of the liquid foam, involving the electrokinetic (EK) phenomena in the liquid-gas interface, have significant effects on the stability of foam. Here, we established a theoretical model for ion transport in liquid films by combing the liquid flow and surface reaction. We find that the surface electrostatic properties of liquid foams were influenced unexpectedly by the pressure-induced flow. The liquid flow will induce the potential and concentration differences at flow direction. When the pressure drop increases to a certain high value, the induced potential and salt concentration difference increases, which leads to the change of the surface electrostatic properties such as zeta potential and the surface charge density. This change shows that the surface electrostatic properties of the foam films depend on the coupling of various factors including ion distribution, pressure drop, etc., which deepens our understanding of the electrostatic properties of the foam films.