Nitrogen‐Doped Carbon Quantum Dot as Novel Nano Additive to Improve Performance and Fouling Resistance of Forward Osmosis Thin Film Nanocomposite Membranes

ABSTRACT Forward osmosis (FO) is considered a strong and energy‐efficient desalination method. The thin film composite (TFC) membranes are widely used in the FO process. In this study, nitrogen‐doped carbon quantum dot (NCQD) was synthesized from citric acid (CA) and m‐phenylene diamine (MPD) as carbon and amine precursors, respectively, by a one‐step hydrothermal method. It was characterized completely by FT‐IR, XRD, UV–visible spectroscopy, DLS, and TEM analysis. Then, NCQD was incorporated in the polyamide (PA) layer to synthesize novel thin film nanocomposite (TFN) membranes. All membranes were analyzed by FT‐IR, WCA, AFM, and FE‐SEM. The TFN‐NCQD membrane, optimized with a concentration of 2000 ppm NCQD, exhibited outstanding FO performance, achieving a 70% increase in water flux compared to the pristine TFC. This membrane attained a peak water flux of 20.4 LMH, a reverse salt flux of 2.1 gMH, and showcased the best selectivity, with values as low as 0.10 g/L among the others. The strong interaction between amine functional groups of NCQD with both MPD and TMC during interfacial polymerization resulted in excellent adhesion and compatibility between the nanofiller and PA, increasing the lifespan of TFN membranes. Moreover, the novel TFN‐NCQD2 membrane showed better fouling behavior than pristine TFC, a 22% improvement when sodium alginate solution (600 ppm) was used as a foulant model.