Electrophoretic mobility of a concentrated suspension of spherical particles

The electrophoretic behavior of concentrated spherical colloidal particles is analyzed theoretically for all levels of scaled surface potential φ(α), taking the effect of double-layer polarization (DLP) into account. The result of numerical simulation reveals that for a very small κα (<0.01), κ and α being, respectively, the reciprocal Debye length and the particle radius, or a very large κα (>100), using a linearized Poisson- Boltzmann equation (PBE) and neglecting the effect of DLP is reasonable; for an intermediate κα, appreciable deviation may result. The deviation is negative if κα is small, and positive if κα is large. The mobility against κα curve may have a local minimum and a local maximum. If φ(α) is low, the mobility increases with the porosity of the system under consideration, and for a fixed porosity, the mobility increases with κα. If φ(α) is high and κα is small, the effect of φ(α) (i.e., solving a nonlinear PBE) on the mobility of a particle is more significant than that of double-layer polarization, and the reverse is true if κα is large. For an intermediate κα, the effect of DLP is more significant than that of φ(α). when the porosity is high, and the reverse is true if it is low.