Theoretical Understanding of How Solution Properties Govern Nanofiltration Performances

Mechanisms governing transfer of ions through nanofiltration membranes are complex and it is primordial to understand how rejection and selectivity performances depend on the properties of the solution. For this purpose, a knowledge model based on a coupling between equilibrium partitioning induced by steric, electric and dielectric exclusions and transport inside pores by diffusion, convection and electro-migration is proposed to theoretically discuss the influence of solution properties on performances. After detailing the physical description of this model, the influence of ion size on rejection is firstly discussed from simulations obtained in several appropriate cases. Since electrostatic interactions are known to play a role on ion rejection, the influence of ion valence and concentration is then studied and different behaviors are brought to light depending on ions considered. Finally, the influence of confinement within nanopores on water dielectric properties and its consequences for ion separation are also addressed