Zeta potential measurements of bubbles in aqueous surfactant solutions

Abstract

The Dorn effect, or the sedimentation potential created when finely divided argon gas bubbles are allowed to rise through an aqueous solution, was measured under various conditions. The sedimentation potential was found to be proportional to the volume fraction of gas bubbles depending upon the surfactant involved and the specific conductances of the solutions. The zeta potentials of bubbles in aqueous solutions of sodium hexadecyl sulfate (SHS) and hexadecyltrimethylammonium bromide (HTAB) are given as a function of surfactant concentrations ranging from 10 −7 to 10 −5 M. Zeta potentials of bubbles in solutions of nonionic surfactants, such as polyoxyethylene dodecyl ether or 1-butanol, and in a mixture of these with SHS and HTAB, respectively, are also given. Electrokinetic adsorption densities of SHS or HTAB at moving bubble surfaces were calculated from zeta potentials using the Gouy—Chapman theory and were compared with data available in the literature that were obtained under equilibrium conditions. The former are always smaller than the latter over the concentration range tested.