Electrophoresis of concentrated spherical particles with a charge-regulated surface

The electrophoretic behavior of spherical colloidal particles is modeled theoretically. The classic analysis is extended to the case of a concentrated dispersion in which the double layer surrounding a particle can assume an arbitrary thickness, and the effect of double-layer polarization is taken into account. Also, the surface of a particle is charge regulated, which leads to a general mixed-type boundary condition, and simulates entities bearing dissociable functional groups such as biological cells and particles with a membrane layer. We show that the absolute surface potential decreases with the increase in £ea, £e and a are, respectively, the reciprocal Debye length and the radius of a particle. The variation of the absolute electrophoretic mobility as a function of £ea is found to have a local maximum. The higher the surface potential the more significant the effect of double-layer polarization, and it becomes insignificant if £ea approaches infinity. ? 2000 American Institute of Physics.