Nanocomposite Membranes via the Codeposition of Polydopamine/Polyethylenimine with Silica Nanoparticles for Enhanced Mechanical Strength and High Water Permeability

A defect-free and stable selective layer is of critical significance for thin film composite membrane with excellent separation performance and service durability. We report a facial strategy for fabricating thin film nanocomposite (TFN) nanofltration membranes (NFMs) based on the codeposition of polydopamine, polyetheylenimine, and silica nanoparticles. Tripled water flux can be obtained from the TFN NFMs as compared with those NFMs without silica nanoparticles. This is ascribed to the improved wettability of the membrane surfaces and the enlarged pore sizes of the selective layer. The interfacial compatibility of the inorganic fillers and the polymer matrices can be enhanced by the electrostatic interactions of silica nanoparticles with polyethylenimine and the adhesive characteristics of polydopamine, resulting in a defect-free selective layer and then good rejection for both bivalent cations and neutral solutes. The rigid silica nanoparticles also improve the surface mechanical strength of the TFN NFMs effectively and lead to structural stability and compaction resistance during the long-term filtration process.