High-performance polyamide thin-film composite nanofiltration membrane: Role of thermal treatment

Highlights: • A high-performance NF membranes were fabricated by thermal treatment. • The optimal formula is 2 wt.% piperazine, 0.1 wt.% NaOH and 0.25 wt/v% trimesoyl chloride. • 95% salt rejection was achieved using the novel NF membrane. • Thermal treatment increased the crosslinking degree of NF membrane. • The optimal membrane water permeability is 13.6 L m⁻² h⁻¹ bar⁻¹. Nanofiltration (NF) membranes have many excellent applications (e.g., removing multivalent ions and pretreating water before reverse osmosis, RO), but their relatively high cost limits their application. Especially in recent years, researchers have paid substantial attention to reducing the cost of NF membranes. In this paper, high-performance NF membranes were fabricated using interfacial polymerization (IP) methods. The polymer concentration, IP solution concentration, and thermal treatment conditions were varied. The synthesized membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), a contact angle goniometer, X-ray photoelectron spectroscopy (XPS), attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy, and performance tests. The results show that water flux was significantly improved using a hot-water thermal treatment method. Our fabricated thermal-treated NF membrane had an approximately 15% higher water permeability with a value of 13.6 L/(m² h bar) than that of the commercially available GE HL membrane with a value of 11.8 L/(m² h bar). Our membranes had the same MgSO₄ rejection as that of the GE HL membrane. We found that the thermal treatment causes the NF membrane surface to be smoother and have a high crosslinking degree.