Electrochemical Instability in Liquid-Liquid Two-Phase Systems

On the basis of the dependency of adsorption and partitioning of ionic surfactant on the phase-boundary potential (Delta(W)(O)phi), it is possible to understand in a unified manner various instability phenomena at the liquid vertical bar liquid interface in the presence of ionic surfactants, such as spontaneous emulsification, oscillation of Delta(W)(O)phi and interfacial tension, and irregularly increased currents on voltammograms of the transfer of surface-active ions across the interface. These instabilities are associated with the electrochemical instability, which defines a thermodynamically unstable condition at the liquid vertical bar liquid interface in terms of Delta(W)(O)phi and is a fundamental concept to understand the instabilities in the presence of ionic surfactants. The characteristic manifestations of the electrochemical instability, that is, the irregularly increased current on voltammograms in the transfer of surface-active ions, the spontaneous emulsification, and the spontaneous oscillation of Delta(W)(O)phi can be designed based on the criterion of the electrochemical instability.