ULTRAFILTRATION OF PROTEIN SOLUTIONS ON ZRO2 MEMBRANES - THE INFLUENCE OF SURFACE-CHEMISTRY AND SOLUTION CHEMISTRY ON ADSORPTION

Ultrafiltration of ovalbumin solutions is carried out on an inorganic (carbon-zirconia) membrane (M6 Carbosep), under conditions which minimize concentration polarization. Protein adsorption is studied through the values of the rejection coefficient, and the additional resistance due to adsorption (R)ads. It is shown that the surface chemistry of the zirconia membrane has a decisive influence on the amount of adsorbed protein and on the permeate flux. The adsorption resistance may vary by a factor 5, the permeate flux by a factor 2 depending on the pretreatment and the ionic composition of the bulk, under identical ionic strength. In particular, the presence of negatively charged phosphate or citrate groups at the surface of the membrane prior to the ultrafiltration test favours a low adsorption of ovalbumin, whereas the presence of nitrate groups favours a high adsorption of this protein. An operating procedure is developed to minimize the adsorption of ovalbumin on this type of membrane.