Electrophoretic mobility of a charged colloidal particle: A computer simulation study

TL;DR

This study uses computer simulations combining lattice Boltzmann and Langevin dynamics to analyze how a charged colloidal particle's electrophoretic mobility varies with surface charge, revealing non-monotonous behavior.

Contribution

It introduces a hybrid simulation approach to investigate the complex dependence of colloidal mobility on surface charge in an electric field.

Findings

Mobility increases linearly at low surface charge density.

Mobility decreases at higher charges where ions co-move with the colloid.

Non-monotonous dependence of mobility on bare charge observed.

Abstract

We study the mobility of a charged colloidal particle in a constant homogeneous electric field by means of computer simulations. The simulation method combines a lattice Boltzmann scheme for the fluid with standard Langevin dynamics for the colloidal particle, which is built up from a net of bonded particles forming the surface of the colloid. The coupling between the two subsystems is introduced via friction forces. In addition explicit counterions, also coupled to the fluid, are present. We observe a non-monotonous dependence of the electrophoretic mobility on the bare colloidal charge. At low surface charge density we observe a linear increase of the mobility with bare charge, whereas at higher charges, where more than half of the ions are co-moving with the colloid, the mobility decreases with increasing bare charge.