Electrochemical Control of the Flow Behaviour of Coagulated Colloidal Sols

Abstract

The flow properties of colloidal suspensions are of paramount importance in many of their technological applications and the control of those flow properties has been known for a long time to depend upon control of the interaction forces between the particles. Addition of strongly adsorbed ions (like H⁺, OH^- and ionic surfactants) has often been used in an empirical way to alter dispersity and “viscosity” but only now are we beginning to obtain a more definite idea of how these ions work. In what follows we will concentrate attention for the most part on the behaviour of monodisperse suspensions of rigid spherical particles involved in attractive interactions with only brief preliminary reference to other types of interaction. The ions involved are in electrochemical equilibrium with the bulk suspension medium and on adsorption they modify the particle charge and hence the energy of interaction between particles. It is the quantitative connection between the solution electrochemistry and the ultimate flow behaviour, that we will explore in this paper.