Preparation of novel carboxylated thin-film composite polyamide-polyester nanofiltration membranes with enhanced antifouling property and water flux

A new carboxylated aromatic diamine-diol (CDADO) monomer was synthesized and employed to fabricate polyamide-polyester thin-film composite (TFC) nanofiltration (NF) membranes, which showed better antifouling and performance properties. The interfacial polymerization (IP) procedure was utilized to prepare carboxylated TFC nanofiltration membranes by reaction of trimesoyl chloride (TMC) in the organic phase with amine and hydroxyl groups in the aqueous phase. By varying the amount of CDADO, it was possible to improve both salt rejection and flux of the membranes. The prepared membranes were characterized using SEM, FTIR, AFM, and contact angle and zeta potential analyses. The outcomes of antifouling and contact angle experiments showed that in presence of the synthesized monomer membrane performance and hydrophilicity improved. The high permeability and antifouling characteristic was due to the presence of suitable hydrophilic carboxylic acid groups and also, terminal hydroxyls and amines at the created polyamide layer. The results showed that the optimum concentration for the CDADO diamine was 2 wt%. The salt retention order for the 2 wt% membrane was Na₂SO₄ (91%) > NaCl (70%) > CaCl₂ (17%). Moreover, the influence of varying pH on rejection of the fabricated membrane with optimized CDADO concentration was investigated, interestingly the membrane showed a pH-responsive gating property. The satisfactory performance of the novel high flux NF membrane compared to pipirazine (PIP) based membranes revealed its valuable potential for the applied purpose.