A novel polyester-amide containing phthalazinone moieties nanofiltration membrane prepared by co-solvent assisted interfacial polymerization

The highly chlorine-resistant polyester-amide thin-film composite (TFC) nanofiltration (NF) membranes (PEA/PPBES) with specific layers incorporating phthalazinone moieties were prepared by interfacial polymerization. With the addition of 4-(4'-hydroxyphenyl)-2,3-phthalazin-1-one (DHPZ) to an aqueous phase of piperazine (PIP), and by using butanone as a co-solvent in the organic phase with trimesoyl chloride (TMC), the chlorine resistance and permeability of the PEA/PPBES membranes were enhanced simultaneously. When the co-solvent butanone was used, a distinctive ring-fold structure on the surface of the selective layer was observed, which could be the reason for the significantly improved the permeability of the PEA/PPBES membranes. With the addition of 3% butanone to the organic phase, the pure water flux (PWF) of the fabricated membrane was 118 L m -2 h -1 (0.5MPa), and the Na 2 SO 4 rejection reached 97.9%, increasing the water permeability by 2.6 times, compared to the control (without butanone). Additionally, the introduction of the phthalazinone moieties improved filtration performance at high temperatures as well as chlorine resistance. At an operation temperature of 95 °C, the water flux and Na 2 SO 4 rejection achieved 148.5 L m -2 h -1 and 96.4%, respectively. After a total NaClO exposure of 60,000 ppm h, the Na 2 SO 4 rejection and water flux changed slightly, demonstrating excellent chlorine resistance. This work offers a novel approach to fabricate TFC NF membranes with excellent chlorine resistance.