Fabrication of Permeable Polyamide Nanofiltration Membrane With Incorporation of Sulfonated Carbon Quantum Dots and the Employment of Nitrate Rejection

Carbon quantum dots with the promising properties of small size, hydrophilicity, miscibility and dispersibility have raised considerable attention toward the fabrication of novel nanofiltration membranes, without affecting the structural integrity of the polyamide layer after the incorporation. In this study, the sulfonated carbon quantum dots (SCQDs) were added to the aqueous phase and then incorporated into the polyamide layer of the thin-film nanocomposite (TFN) membrane via the interfacial polymerization process. Compared to the pristine thin-film composite (TFC) membrane without the incorporation of CQDs (showing a nitrate rejection rate of 89.5% and permeation flux of 15.3 L m −2 h −1 ), the fabricated nanofiltration membrane with the incorporation of SCQDs (TFN-SCQDs) exhibits superior nitrate rejection (95.33%) and the permeation flux (39.2 L m −2 h −1 ) at the tested pressure of 0.6 MPa. The incorporation of SCQDs results in a 5.95% increase in nitrate rejection and the alluring enhancement in permeability up to 156.2%, thereby significantly overcoming the “trade-off” effect of the nanofiltration membrane. Additionally, the TFN-SCQDs membrane shows excellent properties of long-term operational stability, antioxidation and fouling resistance.