Synergistic effect of POSS and chitosan on highly enhancing the separation selectivity and antifouling capacity of polyamide membranes

Abstract

The trade-off limit between permeability and selectivity, along with membrane fouling, has consistently posed significant challenges impeding the practical implementation of water purification membranes. In this paper, a combination of polyhedral oligomeric silsesquioxanes (POSS) and chitosan is introduced into the polyamide layer through interfacial polymerization and crosslinking to optimize the physical, chemical structure of membrane simultaneously. The resulting P/CS-2-POSS-2 membrane exhibits a notable water flux of 221.3 L m−2 h−1 MPa−1 and a substantial Na2SO4 rejection of 97.1 %. The selectivity of water molecules over sulfates in the optimized hybrid membrane is approximately 4 times greater than that observed in the pristine polyamide membrane. This finding underscores the success of the developed method in mitigating the trade-off between permeability and selectivity. Furthermore, the hybrid membranes exhibit superior antifouling properties, as evidenced by an impressive flux recovery ratio of 95.8 % for bovine serum albumin. Additionally, the mass transport properties of the prepared membranes are explored via molecular dynamics (MD) simulations. The results highlight that chitosan primarily enhances the membrane's hydrophilicity, whereas POSS predominantly regulates the membrane's pore size. Both fillers synergistically enhance the comprehensive performance of the membrane by effectively utilizing steric hindrance and the Donnan effect.