Modeling nanofiltration with Nernst‐Planck approach and polarization layer

Selectivity prediction of charged solutions separation by nanofiltration membranes with a two‐dimensional (2‐D) model, combining transport through the membrane and polarization layer (PPTM) is presented. Pore transport is based on the Donnan Steric Pore Model (DSPM) with dielectric reassessment, and transport within the polarization layer is modeled from a steady‐state mass balance, including turbulence influence on diffusion and velocity profiles, as well as wall influence on species diffusion very close to the wall. Specific experiments with glucose and concentrated NaCl solutions were carried out to determine membrane characteristics (average pore radius, charge density, dielectric constant of solution in the pore), and to adjust other model parameters. The model is then validated by comparing simulated rejections and experimental ones for other NaCl concentrations. With adjusted parameters, the model is able to predict local variations of rejection and permeation flux along the tubular membrane, as well as global observed rejections.