RETENTION OF IONS IN NANOFILTRATION AT VARIOUS IONIC-STRENGTH

Retention of a single salt solution was investigated versus the applie d pressure, ion valencies and feed concentration using positively-char ged membranes, obtained by chemical modification of ZrO2 layer of UF m embranes with a cross-linked polymer. Retention of colon was in agreem ent with the Donnan effect but coupling with either divalent counterio n or the smallest colon (proton) was not accounted for. Mixtures of bi g positive organic solutes (antibiotics) and small cations were studie d at increasing ionic strength (I). Retentions of membrane colons were plotted versus I--0.5 according to the semi-empirical model of ionic strength controlled retention the applicability of which was discussed and compared to the Donnan effect.