Surface repair engineering of polyamide membranes for high-performance organic solvent reverse osmosis

Polymer membrane-based organic solvent reverse osmosis (OSRO) holds significant promise for the separation of organic solvent mixtures. However, research in this area remains in its early stages, highlighting a pressing need for advancements in the separation performance of OSRO membranes to meet the stringent requirements of practical applications. Typically, OSRO membranes, including polyamide (PA) membranes, are fabricated through interfacial polymerization (IP). This process is often accompanied by challenges such as the hydrolysis of acyl chloride, which leads to the formation of negatively charged carboxyl groups, defects, and a relatively broad pore size distribution. These factors collectively diminish OSRO performance, highlighting the critical importance of defect repair in enhancing membrane separation efficiency. In this study, we present an OSRO membranes with exceptionally high selectivity for methanol/toluene mixture. By coating a chitosan/glutaraldehyde (CS/GA) layer on the surface of thin-film-composite polyamide (TFC-PA) membranes, we successfully repair surface defects, resulting in membranes with smaller pore sizes and a narrower pore size distribution. Under the conditions of a methanol/toluene mass ratio of 9:1 in the concentrated feed solution, the optimized TFC-PA-CS membrane achieves a remarkable separation factor of 86.3, outperforming all previously reported OSRO membranes. This surface repair strategy provides valuable insights for the construction of next-generation OSRO membranes.