Zeta potential of air bubbles in surfactant solutions

A spinning tube electrophorometer was used to measure the zeta potential of air bubbles immersed in surfactant solutions. It was found that a suitable polymer coated on the inner surface of the tube prevents electroosmosis at pH values between 5 and 8, when anionic or nonionic surfactants are used. Generally speaking, zeta-potential variations principally reflect the kinetics and the saturation of the adsorption of surfactant molecules on the bubbles. Surfactant adsorption and counterion adsorption appear simultaneously, and as the former is substantially higher than the latter, it is not possible to distinguish each contribution. For a very pure nonionic surfactant and bubbles immersed in a solution with a very low counterion content, however, these contributions are sufficiently dissociated to produce a minimum zeta potential as a function of surfactant concentration. (C) 1996 Academic Press, Inc.