Novel antifouling and antibacterial polyethersulfone membrane prepared by embedding nitrogen-doped carbon dots for efficient salt and dye rejection

Novel antifouling and antibacterial nanofiltration membranes were prepared by addition of nitrogen-doped carbon dots (NCDs) to the polyethersulfone (PES). The antibacterial NCDs were successfully fabricated using hydrothermal technique and then were characterized using photoluminescence (PL) spectra, FTIR, XRD, and dynamic light scattering (DLS). The resulted nanoparticles were introduced to PES through the phase separation method. The effect of adding NCDs into the PES membrane, as a novel nanofiller was studied in terms of surface and cross-sectional morphology, hydrophilicity, porosity, permeation, fouling resistance, antibacterial properties, and nanofiltration performance. All the NCD-blended membranes exhibited better performance compared to the bare PES. The water flux was significantly increased from 16.5 kg/m²h for the bare PES to 44.6 kg/m²h for the 0.50 wt% NCD-blended membrane. The 0.50 wt% of NCD-blended PES membrane also showed the best antifouling properties, with a flux recovery ratio (FRR) of 73.1%. The retention sequence of the salts was Na₂SO₄ (80.3%) > MgSO₄ (63.5%) > NaCl (20.7%), showing the common behavior of the negative charge nanofiltration membranes. The antibacterial assessment showed a zone of inhibition for both Gram-negative and Gram-positive bacteria in disks membranes containing higher than 0.10 wt% of NCD concentrations. The results offer NCD-blended membranes as a high potential hydrophilic and antibacterial nanofillers.