EFFECT OF ADSORBED PROTEIN ON THE HYDRAULIC PERMEABILITY, MEMBRANE AND STREAMING POTENTIAL VALUES MEASURED ACROSS A MICROPOROUS MEMBRANE

The effect of the adsorption of a protein, bovine serum albumin (BSA), on the membrane potential, flux reduction and streaming potential mea sured across a microporous polysulphone membrane with different NaCl s olutions and pH values is studied. From electrokinetic phenomena, info rmation about the electrical properties of the membrane (fixed charge concentration and ionic transport numbers) or the membrane/solute inte ractions (streaming and zeta potentials) can be obtained. The influenc e of pH and ionic strength on volume flux and streaming potential valu es is considered. Results show that hydraulic permeability decreases s trongly when the pH decreases, having its minimum value at the isoelec tric point of the protein; the apparent zeta potential values are also dependent on both pH and salt concentration. Differences in the strea ming potential coefficient determined for two membranes fouled under d ifferent experimental conditions may be attributed to different mechan isms for the adsorption of proteins in the membrane: (i) a protein dep osition on the membrane pores; () an adsorbed layer of protein on the membrane surface. In this latter case, the whole membrane system can b e considered as a ''composite'' or two-layer membrane, and a compariso n of the results obtained with both microporous polysulphone and ''com posite'' (microporous + BSA layer) membranes could permit us to determ ine some parameters related to the protein sublayer. (C) 1998 Elsevier Science B.V.