DC electrokinetics for spherical particles in salt-free concentrated suspensions including ion size effects

TL;DR

This paper investigates the electrophoretic mobility and electrical conductivity of salt-free concentrated suspensions of spherical particles, emphasizing the significant impact of finite ion size effects on electrokinetic behavior.

Contribution

It extends previous models by incorporating ion size effects into the analysis of electrokinetics in salt-free suspensions under static electric fields.

Findings

Ion size effects are crucial at moderate to high particle charges.

Finite ion size influences the electric double layer structure.

Results highlight the importance of ion size corrections for accurate modeling.

Abstract

We study the electrophoretic mobility of spherical particles and the electrical conductivity in salt-free concentrated suspensions including finite ion size effects. An ideal salt-free suspension is composed of just charged colloidal particles and the added counterions that counterbalance their surface charge. In a very recent paper [Roa et al., Phys. Chem. Chem. Phys., 2011, 13, 3960- 3968] we presented a model for the equilibrium electric double layer for this kind of suspensions considering the size of the counterions, and now we extend this work to analyze the response of the suspension under a static external electric field. The numerical results show the high importance of such corrections for moderate to high particle charges, especially when a region of closest approach of the counterions to the particle surface is considered. The present work sets the basis for further theoretical models with finite ion size corrections, concerning particularly the ac electrokinetics and rheology of such systems.