Thin film nanocomposite polyamide membrane doped with amino-functionalized graphene quantum dots for organic solvent nanofiltration

Abstract

Thin film nanocomposite (TFN) organic solvent nanofiltration (OSN) membrane with improved separation performance was fabricated via interfacial polymerization reaction between amine-functionalized graphene quantum dots (af-GQDs) doped aqueous monomer solution of m-phenylenediamine (MPD) and n-hexane solution containing trimesoyl chloride (TMC) monomer. We emphasize the employment of extra-low content for both af-GQDs and MPD, so that we could maximize the function of these nanomaterials and eliminate their aggregation at the same time. The af-GQDs nanomaterials could regulate the interfacial polymerization process and could be strongly anchored in the polyamide film via covalent bonding, hence could prevent their loss while providing more channels for faster solvent penetration. As a result, the optimized OSN membrane, TFN-50, shows a super-smooth surface, with a surface roughness as low as 4.3 ± 0.2 nm, and excellent pure solvent permeances which reach 135.8, 112.7, and 69.8 L m−2 h−1 MPa−1 for methanol, DMF and ethanol, respectively, as well as a very high Rhodamine B (RDB, 479 Da) rejection of up to 99.2%, and an ethanol permeance of 61.4 L m−2 h−1 MPa−1. Furthermore, the TFN-50 OSN membrane still shows excellent filtration performance after being submerged in DMF for 336 h or continuous crossflow filtration with Rose bengal (RB, 1017 Da)/DMF solution for 136 h, demonstrating its excellent solvent resistance.