NaOH-assisted heat curing towards highly permeable, superior selective, and antifouling TFC nanofiltration membranes

Abstract

Polyamide (PA) nanofiltration (NF) membranes are promising for diverse water treatment applications, particularly due to their high permeability, selectivity, and inherent antifouling properties. These NF membranes are highly sought after delivering high-quality drinking water. The development of high-performance NF membranes through interfacial polymerization (IP) requires careful optimization of heat treatment and post-treatment processes. In this study, we integrated these steps to establish an optimized heat treatment strategy utilizing post-treatment solutions. Systematic investigations revealed that the use of NaOH as a heating reagent etched the PA layer while promoting the hydrolysis of chloride groups, resulting in NF membranes with enhanced negative charge, improved hydrophilicity, and increased pore size. The optimized Post-3 demonstrated exceptional performance, with a permeability of 29.3 LMH/bar while achieving a remarkable 97.3 % removal efficiency for Na₂SO₄. The Post-3 exhibited excellent selectivity for both monovalent and multivalent ions, making it ideal for advanced water treatment applications. Furthermore, during natural surface water purification, the Post-3 effectively removed organic compounds while retaining moderate mineral content, ensuring the provision of safe drinking water with optimal mineral composition. The study also highlighted the outstanding fouling resistance and long-term stability of the Post-3, offering valuable insights into the customization of NF membranes for advanced drinking water treatment systems.