Electrokinetic properties of a restricted primitive model electrolyte in slit-like nanopores: Effects of enhanced ionic excluded volume

Abstract

The effects associated with the migration of charged particles in solution, driven by an external pressure gradient and/or electric field, are known as electrokinetic phenomena. Among these are the electroosmotic volume flux, capillary conductance, streaming potential, and the apparent electroviscosity. In this work we study the electrokinetic properties of an electrolyte solution confined in a slit-like nanopore. The pore is made up of two charged parallel plates and the fluid is considered through the restricted primitive model electrolyte. The hypernetted chain/mean spherical approximation (HNC/MSA) and Poisson–Boltzmann theory are used to obtain the equilibrium ionic concentration profiles inside the nanopore, thus, the electrokinetic coefficients are calculated by means hydrodynamics equations. The considered monovalent electrolytes are characterized by different ionic diameters and they are at fixed molar concentration. It is exhibited that the electrokinetic coefficients are strongly sensitive to the ionic size, especially for small pore widths. Important variations of electrokinetic coefficients are produced for large ionic diameters associated with their enhanced excluded volume. The quantitative differences between HNC/MSA and Poisson–Boltzmann theories are discussed throughout the paper.