Thin-film nanocomposite nanofiltration membrane with enhanced desalination and antifouling performance via incorporating L-aspartic acid functionalized graphene quantum dots

To fabricate thin-film nanocomposite (TFN) nanofiltration (NF) membrane with enhanced desalination and antifouling performance, L-aspartic acid functionalized graphene quantum dots (AGQDs), integrating the advantages of L-aspartic acid and graphene quantum dots (GQDs), were successfully synthesized and incorporated into the polyamide (PA) selective layer via interfacial polymerization (IP) method. The fabricated TFN membranes with various AGQDs contents were systematically characterized by the microstructures, surface properties, desalination, and antifouling performance. The optimal AGQDs concentration in the aqueous solution reaches 3000 ppm, the resultant TFN-3 membrane exhibits an outstanding water permeance of 18.5 LMH/bar, 60.9% higher than the TFC-blank membrane. Meanwhile, the TFN-3 membrane possesses a higher Na2SO4 rejection than that of the TFC-blank membrane (98.4% vs 95.7%). Additionally, the TFN-3 membrane shows superior antifouling performance over the TFC-blank membrane in the presence of either the negatively charged foulant (BSA) or the positively charged foulant (lysozyme). An appropriate amount of AGQDs added into aqueous solution favors the formation of a smooth, thin, hydrophilic, and electrically neutral selective layer. As a result, the overall separation performance of the TFN-3 membrane, especially the desalination and antifouling performance, are significantly enhanced with the help of AGQDs. Therefore, the incorporation of amino acid-functionalized GQDs into the PA selective layer presents a novel strategy to produce a high-performance NF membrane for water desalination.