Enhancing the long-term separation stability of TFC membrane by the covalent bond between synthetic amino-substituted polyethersulfone substrate and polyamide layer

The weak interfacial force among the substrate with polyamide layer is always a non-ignorable issue for the traditional thin-film composite (TFC) membrane during actual operation. To solve this issue, herein, we have proposed an effective strategy, which is enhancing the long-term separation durability of the TFC membrane by fixing the polyamide layer on the substrate through covalent bonding. To start with, an amino-substituted polyethersulfone (PES-NH2) was synthesized and blended with polyethersulfone (PES) to prepare a hydrophilic PES/PES-NH2 substrate. Next, the amino group in the substrate could effectively react with a part of acyl chloride groups in the organic phase to form the stable covalent bond with the polyamide layer formed by interfacial polymerization. The prepared PES/PES-NH2 TFC membrane possessed a denser polyamide layer with a higher cross-linking degree, as well as exhibited greatly increased separation performance at 0.6 MPa. Significantly, the PES/PES-NH2 TFC membrane still maintained excellent separation performance under a long-term filtration period of 15 days, which is also much longer than the PES TFC membrane. This effective and promising method provides a valuable way to maintain the separation stability of TFC membrane in long-term operation.