Polysulfone Membrane Embedded With Chiral Condensation Product: A Dual Approach of Experimental Validation and Theoretical Prediction for Enantiomeric Separation of Racemic Alanine

Abstract

The precise separation of enantiomers is crucial in the pharmaceutical industry for the production of single enantiomer drugs. In this study, a novel chiral composite membrane was developed by embedding L-alanine glutaraldehyde condensation product (L-AGCP) onto a polysulfone (PSf) matrix for enantioselective separation. The PSf-L-AGCP membranes were systematically characterized using spectroscopic techniques to confirm the successful incorporation of L-AGCP and to evaluate the structural properties. Permeation studies using DL-alanine demonstrated that the membrane achieved an enantiomeric excess (ee) of 94% for D-alanine, with a flux of 68.1 mmol·m⁻²·h⁻¹ under optimal conditions of 4 bar of transmembrane pressure and 25 mL·min⁻¹ flow rate. The enantioselective performance of the membrane was influenced by varying in feed concentration, transmembrane pressure, and flow rate, achieving the highest ee at lower feed concentrations and moderate pressures. Computational study using density functional theory (DFT) revealed a significant interaction energy difference between L-AGCP and the alanine enantiomers, with values of −32.63 kJ·mol⁻¹ for L-alanine and −16.94 kJ·mol⁻¹ for D-alanine, explaining the selective retention of L-alanine on the membrane. This study demonstrates the potential of L-AGCP embedded PSf membranes in overcoming the permeability-selectivity trade-off in enantioselective separations, offering a promising avenue for scalable, efficient chiral separations in pharmaceutical applications.