Influence of ion-solvent interactions and ion correlations on the electroosmotic flow of multivalent electrolytes through charged polarizable conical nanopores
Phys. Rev. Fluids 11, 034202 – Published 24 March, 2026
DOI: https://doi.org/10.1103/8m3x-g2gx
Abstract
An improved mathematical model is developed to study the electroosmotic flow (EOF) of multivalent electrolytes through a conical nanopore embedded in a polarizable material and to elucidate the lacuna between the experimental hypothesis and the existing theoretical analysis. The present model accounts for hydrodynamic steric interactions and electrostatic correlations among finite-size ions, which manifest for nondilute ionic concentrations of multivalent electrolytes. We have also considered the permittivity as well as viscosity of the suspension medium, and hence ionic diffusivity, to vary with local ionic concentration. The bulk electrolyte concentration of monovalent or trivalent salts is varied up to 500 mM and the intrinsic membrane surface charge density is considered up to , so that the strong coupling of finite-size ions manifests. The membrane is considered as low-dielectric and high-dielectric (perfectly conducting) material. The polarization of the membrane, and hence the induced surface charge, depend on the ionic concentration at the electric double layer (EDL). The geometrical asymmetry of the pore and valence asymmetry of the electrolyte leads to an asymmetric-induced surface charge density arising through the dielectric polarization of the membrane. The ion saturation due to the ion steric interactions, electrostatic correlations, and the dielectric decrement affects the counterion distribution in the EDL, which modifies the solid polarization of the membrane. The impact of short-range Columbic as well as non-Columbic interactions is elucidated based on numerical computation of the full set of governing electrokinetic equations supplemented by an asymptotic analysis. Through the present continuum-based approach, we have demonstrated the nonclassical pattern of the EDL, i.e., layered structure of ions, counterion saturation, overscreening of surface charge, and reversal in EOF. Based on the present modified model, we have established qualitative agreement with several experimental observations, which the standard models fails to envisage. The short-range effects on ion transport and their impact on membrane polarization are quantified in this study.
