English: Diagram showing rejection mechanisms that prevent solutes from entering the pores in nanofiltration. These include steric exclusion (size-based exclusion at the pore opening), Donnan effect (repulsion or attraction effect from electrical potential caused by ion concentration differences across a membrane) and dielectric exclusion (resistance to the solute entering the membrane pores due to an energy barrier associated with shedding of the solute hydration shell in order to enter the pore).^[1]