Preparation and characterization of NASICON–ZnAl2O4-based ultrafiltration membranes

The present paper is devoted to the preparation of an ultrafiltration ceramic membrane. Thin NASICON–ZnAl2O4-based layers have then been synthesized by slip-casting on an alumina macroporous support from Na3Zr2Si2PO12, i.e. NASICON (Na-Super Ionic CONductor) and ZnAl2O4 sols. The electrical properties of the active layers and of its precursors were carried out from the streaming potential measurements across the membrane during the filtration process and from the determination of the electrophoretic mobilities of the powders precursors of the phases. The filtration performances of the NASICON–ZnAl2O4-based material towards different electrolytes were determined by the measurement of the ionic rejection rate. It has then been proved that the filtering properties of the membranes are governed by the electrostatic interactions at the solution–membrane interface. Salt rejection rates of 90% were measured against CaCl2 or NaSO4. A correlation was established between the streaming potential across the membrane and the filtration properties.