Concentration of Ionic Groups as a Factor to Control Adsorption and Mass Transfer Properties of Aromatic Poly- and Copolyamide Based Ultrafiltration Membranes

Ultrafiltration membranes based on poly( m -phenylene isophthalamide) and random copolyamide containing 1, 3, 5, and 10 mol % units with sulfonate groups were fabricated. The adsorption (under static conditions and conditions of ultrafiltration of protein solutions) and mass transfer properties of membranes were examined. Solutions of bacitracin, lysozyme, myoglobin, and bovine serum albumin were used for adsorption and separation experiments. It was shown that in the presence of a charge on protein macromolecules and the membrane surface, the role of electrostatic forces is decisive in the protein adsorption mechanism, however the contribution of nonelectrostatic membrane/protein interactions is significant. It was found that in the systems studied, the adsorption capacity of membranes can vary from 0.02 to 0.29 mg cm –2 . The kinetic curves of the specific productivity and selectivity of membranes were obtained. The tools for regulating the electrostatic interaction intensity (the concentration and nature of ionic groups in the copolymer and the pH of the protein solution) were shown to be means for controlling the transport characteristics of membranes. The optimal combination of mass transfer properties of the resulting membranes can be achieved at pH above the isoelectric point of the protein.