Formation and Characterization of Functionalized Anion Exchange Membrane for Protein Separations

Formation and characterization of functionalized anion exchange membrane for protein separations

Authors

Lukai Yang, Ph.D. candidate, The University of Alabama

Stephen M.C. Ritchie, Associate Professor, The University of Alabama

Abstract

           The focus of this research is synthesis and characterization of functionalized polyethersulfone ultrafiltration membranes as anion exchange membranes for protein adsorption and separations. Functionalized membranes were synthesized by sulfonation, polymerization and amination. The initial step was to introduce sulfonic acid groups in a commercially available ultrafiltration membrane (300kDa) by sulfonation with 0.5 M H₂SO₄. The sulfonated membrane was subsequently polymerized with chloromethyl styrene by cationic polymerization. The final step involved amination with amine groups to impart positive charges to the grafted chains. Water flux and ion exchange capacity (IEC) studies were carried out to characterize the modified membrane. Decreased water permeability and increased IEC were observed after amination compared with the raw membrane indicating the presence of polymeric chains in the membrane flow path. ¹H NMR characterization confirmed the incorporation of poly (chloromethyl styrene) grafts. Sulfonation was also investigated in detail at room temperature by varying sulfuric acid concentration from 0.5 to 2 M. It was observed that initiator concentration increased from 0.014 to 0.027 meq/g when sulfuric acid concentration increased from 0.5 to 2 M. Amination was investigated with three aminating agents, diethylamine (DEA), para-aminobenzoic acid (PABA) and glycine. It was observed that glycine yielded the highest IEC. This was most likely due to the higher nucleophilicity of glycine compared with PABA. Results for protein adsorption will also be presented from Bovine Serum Albumin (BSA) adsorption studies.