Calcul du potentiel et de la densité de charge de surface d'une sphère chargée en présence d'électrolytes dissymétriques

Abstract

The surface charge and surface potential of the dispersed particles permits to estimate their physico-chemical interactions and the stability of the suspension.

In a practical case, the surface potential can reach very high values (± 100 to ± 400 mV). In that case, the solution of Debye-Hückel equation becomes inaccurate.

The same holds if the particle radius becomes very small (500 to 10 A) and κa < 100. In this latter case, it is the Poisson-Boltzmann equation implying the parity between a spherical particle and a plane surface which becomes unsuited.

A more adapted and precise solution of the non linear Poisson-Boltzmann equation for charged spherical particles in the presence of dissymmetrical electrolytes is given. We established the relationships of the electrostatic potential Ψ(x) and of the surface charge σ0 and demonstrated that electrolytes of trivalent anions [(1-3) and (2-3) ] give higher surface densities.