Modification of polyacrylonitrile TFC-FO membrane by biowaste-derived hydrophilic N-doped carbon quantum dots for enhanced water desalination performance

Effective membranes are critical for enhancing the productivity of the forward osmosis (FO) desalination process. In this work, a straightforward approach is presented for constructing a hydrophilic and high-flux thin film composite FO (TFC-FO) membrane onto a polyacrylonitrile (PAN) sublayer. To this purpose, biowaste-derived nitrogen-doped carbon quantum dots (BWD-NCQDs) were incorporated into the polymeric structure of the TFC selective layer, which improved surface hydrophilicity and caused the creation of more water channels, resulting in better intrinsic transport properties. In both FO and pressure retarded osmosis (PRO) membrane orientations, TFC-FO membranes containing 0.01–0.1 wt% of BWD-NCQDs showed better water permeation and NaCl rejection than the pristine TFC membrane. In the presence of 0.05 wt% of BWD-NCQDs, water flux increased by 54.7 % and reached 24.6 Lm−2 h−1, and reverse solute flux decreased by 43.3 % to 3.81 g−2 h−1 compared to the pristine membrane. The optimum membrane also showed better fouling and water desalination behavior. Therefore, modification of the membranes by hydrophilic BWD-NCQDs represents superior performance in the FO processes. This study demonstrates the potential of using hydrophilic NCQDs derived from biowaste materials to incorporate into TFC membranes and improve their FO proficiency in water desalination.