DETERMINATION OF THE FILTERING LAYER ELECTROKINETIC PROPERTIES OF A MULTILAYER CERAMIC MEMBRANE

A multi-layer ceramic UF membrane consisting of an alumina support, a titania intermediate layer and a zirconia filtering layer has been stu died. Streaming potential and permeation flux measurements have been p erformed on the lone support, the two-layered membrane (alumina+titani a) and the three-layered membrane in order to access the electrokineti c behaviour of each layer and especially the zirconia filtering layer. Results show that the global streaming potential measured across the multi-layered membrane does not reflect the real properties of the sep arating layer because each layer plays a non-negligible role on the gl obal measurement. indeed, the streaming potential values and the isoel ectric point determined for the filtering layer differ significantly f rom the ones obtained with the multi-layered membrane. A study of the apparent transport number of ions within the different membranes under an imposed concentration gradient was performed in order to confirm o ur results. Pores of the alumina support and the titania intermediate layer are not small enough to be characterized by this method, which o nly allows determining the isoelectric point of the zirconia layer. Fo r this last one, results are in good agreement with the isoelectric po int determined from streaming potential and permeation flux measuremen ts.