DIFFUSIOPHORESIS OF COLLOIDAL SPHEROIDS IN SYMMETRICAL ELECTROLYTES

An analytical study is presented of the diffusiophoresis of a non-cond ucting spheroid in a solution of symmetric electrolyte with a constant concentration gradient oriented arbitrarily with respect to the axis of revolution of the spheroid. The thickness of the electric double la yer surrounding the spheroid is assumed to be small relative to the di mension of the particle, but the effect of the polarization of the mob ile ions in the diffuse layer is incorporated. To solve the conservati ve equations governing the system, a slip velocity of fluid and normal fluxes of solute ions at the outer edge of the thin double layer whic h balance convection and diffusion of the solute ions along the partic le surface are used as the boundary conditions for the fluid domain ou tside the diffuse layer. Explicit expressions for the diffusiophoretic and electrophoretic velocities of a spheroidal particle and the avera ge particle velocities in an ensemble of identical, non-interacting sp heroids with random orientation distribution are obtained. It is found that the diffusiophoretic and electrophoretic velocities of the parti cle decrease with the reduction of the maximum length of the particle in the direction of migration.