CHARACTERIZATION OF SURFACE-PROPERTIES OF CERAMIC ULTRAFILTRATION MEMBRANES BY STUDYING DIFFUSION-DRIVEN TRANSPORT AND STREAMING POTENTIAL

The knowledge of the electrokinetic properties of the filtering layer of membranes is useful to predict and understand their filtration perf ormances. Streaming potential allows the characterisation of these pro perties during the filtration process. This technique coupled with per meation flux measurements was carried out with different multi-layered ceramic membranes composed of distinct alumina, titania and zirconia layers in order to determine the true streaming potential and isoelect ric point of each metal oxide layer composing the membrane. The appare nt transport number of ions in the different structures and the permse lectivity have been determined by imposing a concentration gradient ac ross these membranes. The isoelectric point of the two finest pore lay ers were deduced from the pH dependence of the membrane permselectivit y. The specific adsorption of calcium ions onto the surface of these a mphoteric membranes was shown from permselectivity values as well as f rom streaming potential measurements.