Significance of thermodynamic and physical characteristics on permeation of ions during membrane separation: Hydrated radius, hydration free energy and viscous effects

► Strength of hydration shell significantly affect ability of ions to permeate through thin film membranes. ► The hydrated radii of exhibit a strong correlation with ionic potential for cations but not for anions. ► During membrane filtration, hydration free energy plays a significant on sticky behavior of ions on the retentate site. ► Ions that can easily lose their hydration waters (e.g., K+, Na+) can partition to the membrane phase.