Ultrafiltration of model solutions of macromolecular compounds. Effect of pH on ultrafiltration of solutions of proteins

It was found that in ultrafiltration of solutions with different pH, retention of globular proteins passes through a maximum or minimum at a pH corresponding to the isoelectric point; the concrete shape of the dependence is usually determined by the relation of the size of the molecules of the dissolved substance and the pores of the membrane. The results obtained are explained based on concepts of a model of concentration polarization with additional consideration of the changes caused by electrostatic interactions in the membrane-solution system. Problems of calibration of ultrafiltration membranes using globular proteins are discussed, and the role of the material of the membrane in membrane separation processes is noted.