Construction of Silica Nanoparticle Penetrant-doped TFN membranes for Enhanced Permeance Nanofiltration

Constructing high-performance nanofiltration membranes requires maximizing water permeance while maintaining desirable rejection. Here, a thin-film nanocomposite (TFN) membrane with a filler penetrant-doped structure was designed for efficient desalination. Unlike conventional TFN membranes, the filler silica nanoparticles are exposed on the top of the polyamide layer, which further enhances the hydrophilicity and thus allows water to wet the membrane surface quickly. At the same time, the partially embedded silica nanoparticles create transportation channels for water molecules between silica and polyamide (PA) matrix. This stems from the moderate cross-linking between hydroxyl groups and chlorides on the silica surface, which builds water channels while avoiding large interfacial defects. As a result of the special doping, the NF membrane has a high water permeance, reaching an impressive value of 19.7 L m^-2h^-1 bar^-1, which is 95% higher than that of the conventional TFN membrane. Additionally, the membranes exhibited a Na₂SO₄ rejection exceeding 95%. In conclusion, this penetrant doping synthesis method provides a promising solution for the construction of high-permeance nanofiltration membranes.