Chemical charge regulation and charge renormalization in concentrated colloidal suspensions

This article discusses the charging behavior of particles in a colloidal su spension allowing for a simple model reaction at the surface of the colloid al particles that regulates the total number Z(f) of free counterions. This number is to be distinguished from an effective number of charges Z* calcu lated in the Wigner-Seitz cell model to determine the interaction between t he colloidal particles. We discuss the problem in terms of the full free en ergy of the system. The number of free counterions Z(f) as a function of th e structural charge of the colloid is derived from the minimum of this free energy. Our results are compared with experimental data. (C) 1999 Academic Press.