Electrostatic effects on partition coefficient of spherical colloid into porous membrane

Abstract

Electrostatic effects on partitioning of spherical colloids into a porous membrane consisting of long straight cylindrical pores filled with an electrolytic solution are investigated through a mathematical model. The colloids and the pore surface potential are assumed to be constant, and are such that the Debye-Huckel approximation can be applied. Assuming that the solution is diluted, the effects of colloid-colloid interactions is negligible. The cations and anions are viewed as point charges, and the electric potential is obtained as a solution of a linearized Poisson-Boltzmann equation. The colloid equilibrium partition coefficient, the ratio between the intrapore colloid concentration and that in the external bulk solution, is dependent on the difference between the electrostatic free energy of the system of a colloid confined in a cylindrical pore and the addition of the electrostatic free energy of a system of an isolated colloid in an unbounded fluid and that of an empty cylindrical pore. Effects of colloid size, colloid surface potential and Debye length on the colloid equilibrium partition coefficient are investigated.