Nanofiltration theory: An analytic approach for single salts

We determine the complete set of nanofiltration (NF) parameters (rejection rate, electric filtration potential, volume flux density) of single salts using an analytical approach. Our model is based on the hindered extended Nernst-Planck (ENP) and Stokes equations. We solve the transport equations within the scope of the hindered electrotransport (HET) model, which takes into account ion charge and size (rejection is controlled by both electrostatic and steric effects). We also validate these calculations using both an analytical solution to the classic ENP model, which neglects the ion size, and numerical methods via our NF simulation program, Nanoflux. A preliminary application of the model to organic membranes suggests that the HET model provides a coherent description of ion transport in charged nanoporous membranes.