Tailoring Cl-/SO42- selectivity and fouling resistance in polyamide igsynergistic monomers

To address the growing demand for high-performance membranes in sustainable water treatment, this study developed a novel nanofiltration (NF) membrane via a mixed-monomer strategy. Interfacial polymerization was conducted on macroporous polyethersulfone (PES) supports using an aqueous phase containing piperazine (PIP) and piperazine-2-carboxylic acid (PIP-COOH), and an organic phase of trimesoyl chloride (TMC). The introduction of PIP-COOH, a carboxyl-functionalized monomer, not only increased the membrane’s surface negative charge but also moderated the interfacial reaction rate, enabling the formation of a more uniform and controllable polyamide layer. By systematically adjusting the PIP/PIP-COOH ratio and monomer concentrations, the membrane structure and separation properties were fine-tuned. Under optimal conditions (3:1 PIP/PIP-COOH, 0.4 % TMC), the membrane achieved a NaCl/Na 2 SO 4 selectivity of 19.86 and a water permeance of 10.42 L·m −2 ·h −1 ·bar −1 . Additionally, outstanding antifouling performance was demonstrated, with a total fouling ratio of just 4.62 % and a flux recovery rate of 99.07 % after hydraulic cleaning. These results highlight the potential of using functionalized monomers in mixed systems to achieve a favorable balance between permeability, selectivity, and fouling resistance. The proposed approach offers a scalable and effective pathway for designing next-generation NF membranes for sustainable water treatment and resource recovery.