Effect of adding a smart potassium ion-responsive copolymer into polysulfone support membrane on the performance of thin-film composite nanofiltration membrane

Thin-film composite (TFC) nanofiltration (NF) membranes were fabricated via the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride on polysulfone (PSf) support membranes blended with K+-responsive poly(N-isopropylacryamideco-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB(15)C(5))). Membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscope, scanning electron microscope, contact angle, and filtration tests. The results showed that: (1) Under K+-free conditions, the blended P(NIPAM-co-AAB(15)C(5))/PSf supports had porous and hydrophilic surfaces, thereby producing NF membranes with smooth surfaces and low MgSO4 rejections; (2) With K+ in the PIP solution, the surface roughness and water permeability of the resultant NF membrane were increased due to the K+-induced transition of low-content P(NIPAM-co-AAB(15)C(5)) from hydrophilic to hydrophobic; (3) After a curing treatment at 95 degrees C, the improved NF membrane achieved an even higher pure water permeability of 10.97 Lm(-2)h(-1)bar(-1) under 200 psi. Overall, this study provides a novel method to improve the performance of NF membranes and helps understand the influence of supports on TFC membranes.