CHARACTERIZATION OF THE ADSORPTION-FOULING LAYER USING GLOBULAR-PROTEINS ON ULTRAFILTRATION MEMBRANES

The mechanisms of membrane fouling and the effects of properties and structure of the adsorbed-protein layer on membrane fouling were studied using bovine serum albumin (BSA) and beta-lactoglobulin (beta-LG) as test proteins, and poly (vinylpyrrolidone)-coated polycarbonate (PC) and regenerated cellulose (RC) as membranes. Ultrafiltration (UF) experiments were modeled with a 3-parameter resistance model to separately determine resistances due to osmotic pressure and adsorption. An analytical method was also developed to determine protein loadings under UF and static conditions. The dynamic behavior of osmotic pressure or interfacial concentration is discussed on the basis of the material balance around the interface. Derjaguin-Landau and Verwey-Overbeek (DLVO) theory and the concept of a rate-limiting step are applied to phenomena that occur at the interface during protein adsorption. A steric hindrance repulsion due to PVP tails on the PC membrane has a pronounced effect on protein loading. The hydrophilic matrix of RC may act as a water reservoir that maintains continuous hydration of the adsorbed layer, which can be dehydrated during protein adsorption. We believe that hydration results in a lower fouling resistance. Additionally, the size of the pores relative to the protein molecule has a pronounced effect on the properties and structure of the adsorbed layer and its fouling resistance.