Gouy-chapman theory

Abstract

A net particle surface charge different from zero implies the existence of adsorbed ions in a diffuse swarm. Diffuse swarm species respond to surface charge by distributing themselves in order to screen it through counterion accumulation and coion exclusion. Screened particle charge, in turn, mediates the interparticle interactions in colloidal suspensions that determine their stability (Verwey and Overbeek, 1999; Hunter, 2001; Sposito, 2008). Thus particle charge screening is the most important resultant chemical property of the diffuse swarm. Gouy-Chapman theory offers perhaps the simplest quantitative description of the spatial distribution of ions in a diffuse swarm through the Poisson-Boltzmann equation (Equation 1), a nonlinear differential equation whose solution gives the spatial dependence of the average electrostatic potential in an adsorbed electrolyte solution modeled as a swarm of mobile hard-sphere ions immersed in a continuum dielectric medium contacting a charged particle surface that can be planar, cylindrical, or spherical.