journal of MEMBRANE SCIENCE ELSEVIER Journal of Membrane Science 114 (1996) 27-38 Effects of proteins on electrokinetic properties of inorganic membranes during ultra- and micro-filtration Laurence Ricq a Andr6 Pierre a,* Jean-Claude Reggiani a Serge Zaragoza-Piqueras a Jacques Pagetti a, Georges Daufin b a Laboratoire de Corrosion et Traitements de SurJace, 32 rue M~gevand. 25030 Besancon, Fr~mce INRA. Laboratoire de Recherches et de Technologie Laitikre, 65 rue de St. Brieuc, 35042 Rennes Cedex, Fran,'c Received 19 May 1995; revised 7 September 1995; accepted 12 September 1995 Abstract The streaming potential is measured across inorganic ultra-filtration and micro-filtration membranes to characterize them. Concurrently, electrophoretic mobility measurements are carried out to study the membrane material. The influence of whey proteins on the streaming potential and electrophoretic mobility is also studied. Results show that the membrane interface after adsorption has a surface property behavior similar to that of the proteins from a charge point of view. Moreover, the streaming potential considers two aspects of filtration which must take into account the steric and electric effects. In an electrolyte solution without proteins, the streaming potential depends only on charge repartition, determined by pH value. With whey proteins, the streaming potential depends on both charge repartition and permeate flux. If there is no inner fouling, the charge repartition is not affected and the streaming potential depends exclusively on flux; when there is an inner fouling by protein adsorption, the pore surface is modified and the streaming potential depends on both permeate flux and on electric charge of the oxide-solution interface. Keywords: Streaming potential; Electrophoretic mobility; Proteins; Zirconia; Microfiltration and ultrafiltration membranes 1. Introduction The use of ultra-filtration and micro-filtration to separate proteins needs to take into account the steric effect and role of the protein-membrane and pro- tein-protein interactions. Ferry's model [1 ] and more recently those of Munch et al. [2] and Zeman and Wales [3] have allowed an explanation of retention phenomena based on relative size of pores and so- lutes. Their models lead to steric rejection by mere- * Corresponding author. branes with uniform pore size distribution. Neverthe- less, they noticed that electrostatic phenomena affect the rejection of rigid macromolecules by controlling the length scale of repulsive interactions between molecules and the pore wall. The role of electric interactions on filtration is the subject of several recent studies, Khedr et al. [4] studied the streaming potential which allowed an estimation of the effec- tive exchange capacity of modified cellulose acetate membrane. Chaufer et al. [5] modified the interac- tions between membrane and proteins by varying the ionic strength to improve membrane selectivity. Nys- trom et al. [6] and Causserand et al. [7] showed that 0376-7388/96/S15.00 © 1996 Elsevier Science B.V. All rights rese~,ed SSDI 0376-7388(95)00248-0