電荷調整膠體粒子懸浮液中之輸送現象(1/3)

The body-force-driven migration in a homogeneous suspension of spherical
charge regulating particles with an arbitrary thickness of the electric double layers is
analyzed. The charge regulation due to association/dissociation reactions of
functional groups on the particle surfa ce is approximated by a linearized regulation
model, which specifies a linear relationship between the surface charge density and
the surface potential. The effects of particle interactions are taken into account by
employing a unit cell model. The overl ap of the double layers of adjacent particles
is allowed and the relaxation effect in the double layer surrounding each particle is
considered. The electrokinetic equations which govern the ionic concentration
distributions, the electrostatic potential pr ofile, and the fluid flow field in the
electrolyte solution in a unit cell are linearized assuming that the system is only
slightly distorted from equilibrium. Using a regular perturbation method, these
linearized equations are solved for a symmetrically charged electrolyte with the
equilibrium surface potential of the particle as the small perturbation parameter.
Closed-form formulas for the settling velocity of the charge regulating spheres are
derived. Our results show that the charge regulation effec ts on the sedimentation in
a suspension appear starting from the leading order of the equilibrium surface
potential, which is determined by the regulation characteristics of the suspension.