Electric double layer of colloidal particles in salt-free concentrated suspensions including non-uniform size effects and orientational ordering of water dipoles

TL;DR

This paper develops an advanced theoretical model for salt-free colloidal suspensions that incorporates non-uniform particle sizes and water dipole orientation, improving predictions of electric potential, ion distribution, and permittivity.

Contribution

It introduces a novel mean-field model including size effects and water dipole orientation, enhancing understanding of electric double layers in concentrated suspensions.

Findings

Model predicts significant permittivity decrease near highly charged particles.

Inclusion of effects improves accuracy for medium to high particle charges.

Model shows counterion stratification and altered electric potential profiles.

Abstract

The response of a suspension under a variety of static or alternating external fields strongly depends on the equilibrium electric double layer that surrounds the colloidal particles in the suspension. The theoretical models for salt-free suspensions can be improved by incorporating non-uniform size effects and orientational ordering of water dipoles neglected in previous mean-field approaches, which are based on the Poisson-Boltzmann approach. Our model including non-uniform size effects and orientational ordering of water dipoles seems to have quite a promising effect because the model can predict the phenomena like a heavy decrease in relative permittivity of the suspension and counterion stratification near highly charged colloidal particle. In this work we numerically obtain the electric potential, the counterions concentration and the relative permittivity around a charged particle in a concentrated salt-free suspension corrected by non-uniform size effects and orientational ordering of water dipoles. The results show the worth of such corrections for medium to high particle charges at every particle volume fraction. We conclude that non-uniform size effects and orientational ordering of water dipoles are necessary for the development of new theoretical models to study non-equilibrium properties in concentrated colloidal suspensions.