Ion Partitioning Effects on Electroosmotic Flow Through pH Regulated Cylindrical Nanopore

Abstract

AbstractThe ion partitioning effects on electroosmotic flow have been studied through pH-regulated polyelectrolyte grafted cylindrical nanopore. The permittivity between the polyelectrolyte layer and electrolyte solution are taken differently, which generates ion partitioning. The surface charge density of the nanopore is negative, while the charge density in the polyelectrolyte layer depends on the pH values and concentration in aqueous solution. The present model of the electroosmotic flow through pH-regulated polyelectrolyte layer is considered Nernst–Planck equation for the ionic species, Navier–Stokes equation in modified form for flow and Poisson equation for potential distribution. These governing equations are solved numerically on a staggered grid system by finite volume method. This article investigates the importance of different dielectric permittivity, ionic strength, pH values, softness, and the charged density of the nanopore wall. The permittivity ratio is defined by the permittivity of polyelectrolyte layer and electrolyte solution. The average electroosmotic flow decreases with the permittivity ratio. The increase in the softness parameter decreases the flow rate. The ion partitioning contributes to the penetration effect of counter ions in the polyelectrolyte layer, which decreases the body force, and hence affects the electroosmotic flow rate.KeywordsIon partitionElectroosmotic flowPolyelectrolyte layerNernst–Planck equation