Adsorption Process at the Gas-Liquid Interface of a Spherical Rising Gas Bubble. 1st Report. Numerical Analysis on Surface Concentration of Surfactants at the Steady State.

Abstract

To estimate the total amount of adsorbed surfactants onto the surface of a single rising bubble, the Navier-Stokes equation, the convection-diffusion and the surface-diffusion equations of the surfactants were numerically solved at the steady state and the effects of the Reynolds number (Re) and the bulk concentration of the surfactants on the surface concentration distribution were investigated. The results reveal that the surface concentration of the surfactants at the top of the bubble is lower than that at the bottom and the difference between them increases as the Re increases or the bulk concentration of the surfactants decreases. The critical Re (Rec) can be estimated for the bubble to behave as a solid particle and the averaged concentration of surfactants coincide with the equilibrium concentration corresponding to a zero net adsorption-desorption flux for Re<Rec.