High-flux polyamide membrane with improved chlorine resistance for efficient dye/salt separation based on a new N-rich amine monomer

Interfacial polymerization is the gold standard for manufacturing thin film composite (TFC) membranes for nanofiltration (NF) and reverse osmosis (RO). However, typical polyamide (PA) thin film composite (TFC) membranes fabricated by interfacial polymerization are inappropriate for dye wastewater zero discharge and are susceptible to oxidizing agents. In this study, by using a new N-rich amine monomer 3,5-diamino-1,2,4-triazole (DAT), a novel PA TFC membrane was fabricated for the separation of dyes and salts. It is speculated that the unique molecular structure of DAT can conducive to the formation of a less compact polyamide layer with improved chlorine resistance. The optimum membrane shows an ultrahigh pure water permeability (95.1 L/m2·h·bar) and an excellent dye/salt separation selectivity for Congo red and NaCl (rejection, 99.1% and 5.8%, respectively). This is superior to that of the two commonly used dye/salt separation commercial membranes (Sepro NF 6 and NF 2A, Ultura). Furthermore, the resultant DAT/TMC TFC membranes maintained their original separation efficacy after 120 h of immersion in NaClO solution, demonstrating their good chlorine resistance. In summary, this study not only expands the application of interfacial polymerization, but also provides a new inspiration for the preparation of advanced membranes for efficient dye/salt separation.