Phase Separation in Deionized Colloidal Systems:  Extended Debye−Hückel Theory

Abstract

Using an extension of the Debye−Hückel theory for strong electrolytes, the thermodynamics, phase behavior, and effective pair colloidal potentials of deionized charged dispersions have been investigated. With the inclusion of colloid size effects, this model predicts the possibility of the existence of two critical points, one of which is thermodynamically metastable but can exhibit interesting behavior at high colloid charges. This analytic model also serves as a pedagogic demonstration that the phase transition is driven by cohesive Coulomb interactions between all charged species in the system and that this cohesion is not inconsistent with a repulsive effective pair potential between the colloidal particles.