Coalescence in Oil/Water Systems

Abstract

<p> A theoretical and experimental study is presented of the effect of oil/water system physical properties, surfactant concentration, and drop size on the drop rest-time and lamella behaviour. </p> <p> The work has three distinct parts. The first part is based on the assumption that the dynamic pressure distribution in the lamella can be described by a simple three term polynomial. Equations for the relative lamella thickness profile are derived and are shown to accurately describe experimental lamella thickness profiles measured both in this work and by other investigators. </p> <p> The second part presents and discusses the experimentally measured drop rest-times and simultaneously observed lamella behaviour for the range of variables studied. Five mechanisms are proposed to account for the observed lamella behaviour. </p> <p> The third part derives equations to describe the lamella drainage, the interfacial distribution of adsorbed surfactant for a lamella undergoing drainage, and the dynamic lamella pressure distribution. The solution of the lamella drainage equation is then compared with experimentally determined profiles of the relative lamella thickness for both the complex model and a simple model based on a parallel disc lamella. </p>