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 φa, taking the effect of double-layer polarization (DLP) into account. The result of numerical simulation reveals that for a very small kappaa (<0.01), kappa and a being, respectively, the reciprocal Debye length and the particle radius, or a very large kappaa (>100), using a linearized Poisson-Boltzmann equation (PBE) and neglecting the effect of DLP is reasonable; for an intermediate kappaa, appreciable deviation may result. The deviation is negative if kappaa is small, and positive if kappaa is large. The mobility against kappaa curve may have a local minimum and a local maximum. If φa is low, the mobility increases with the porosity of the system under consideration, and for a fixed porosity, the mobility increases with kappaa. If φa is high and kappaa is small, the effect of φa (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 kappaa is large. For an intermediate kappaa, the effect of DLP is more significant than that of φa when the porosity is high, and the reverse is true if it is low. Copyright 1999 Academic Press.