Electrophoretic Migration of Charged Permeable Particle in Electrolyte

P.P. Gopmandal and S. Bhattacharyya
Indian Institute of Technology, Kharagpur, IN

Keywords: electrophoresis, charge density, Reynolds number

Summary:

Advection of a charged permeable aggregate under the influence of electric filed in a electrolyte is studied numerically. The electroosmotic flow and ion penetration inside the aggregate leads to characteristic difference in hydrodynamics compared to a rigid particle. In the present paper we have investigated the nonlinear electrokinetics of the permeable aggregate migrating at an arbitrary velocity. The particle can be transported either through a centrifugal field or by imposing a pressure gradient, combined with the electric field. The mathematical model considered here is based on the Navier-Stokes-Nernest-Planck-Poisson equations. Based on the Brinkman model for porous media, the flow field and ion distribution is computed both inner and outer region of the particle. The flow field is analyzed through a single domain approach in which the porous region is considered as a pseudo-fluid and the composite region as a continuum. A pressure correction based control volume approach is adopted for computing the governing equations. The deformation of electric field around the aggregate due to the convection of ions leads to the polarization effect. This polarization effect depends on the ion concentration of the electrolyte ( i.e., Debye length), charge density of the aggregate, its permeability as well as Reynolds number. A detailed investigation on the hydrodynamics and force field is investigated in the present analysis.