Highly permeable chlorine-resistant forward osmosis membrane by grafting novel sulfonamide monomers

This paper presents a polyamide (PA) thin film composite (TFC) forward osmosis membranes with high chlorine resistance and permeability which were fabricated via interfacial polymerisation employing novel monomers with distinct stable sulfonamide structures. Three different membranes were produced, commonly having a substrate layer made through the phase inversion approach and a PA layer with piperazine (PIP) and tricarbonyl chloride (TMC) while differing in the additive chemical used to build the upper layers (sulfathiazole (ST), 4-aminobenzenesulfonamide (ABSA), and 2-aminosulfamide hydrochloride (AESA)). The cross-linked structures and surfaces of the developed membranes were rigorously assessed, and the infrared spectra revealed that the membranes' surfaces had been successfully grafted with the sulfonamide groups. The flow rates of fabricated membranes with ST, ABSA, and AESA additions increased by 148.2 %, 110.3 %, and 64.7 %, respectively, whereas their reverse salt fluxes decreased by 30.1 %, 26.9 %, and 35.7 %, respectively. 200 ppm NaClO was used to conduct a chlorine stability test under varied pH circumstances (5.0, 7.0, and 9.0), and the findings indicated that the membranes have excellent durability. As the sulfonamide comprises the NH functional groups, the sulfonamide-based membranes were not eroded by chloride ions; hence, the sulfonamide molecules effectively guarded the PA molecular structure from chloride ion damage, thereby increasing PA's tolerance to chloride ions.