Ionic selectivity of nanofiltration membrane

Rejection properties of positively charged PDM/PSF nanofiltration(NF) membrane to inorganic ions are studied.Ion selectivity is correlated to their type and valence as well as Shannon′s radius.The experimental results show that the effect of valence of anions is insignificant to rejection,but the valence of cations has an effect on the rejection considerably;the rejection of the membrane to divalent cations(and multivalent cations) is higher than to monovalent cations.And the NF membrane has a higher rejection to composite ions than to mono ions.The rejection to anions increases with increasing of Shannon′s radius,but the rejection to cations is decreasing with increasing of Shannon′s radius.