Enhancing the desalination performance of polyamide nanofiltration membranes via in-situ incorporation of zwitterionic nanohydrogel

Designing a nanofiltration (NF) membrane with distinguished high permeability and ion selectivity is attractive for handling hypersaline wastewater. In this work, we used zwitterionic nanogels (ZNGs) as aqueous additives to prepare NF membranes by interfacial polymerization (IP), and comprehensively investigated the chemical composition of the nanogels on the performance of NF membranes. The outcome of characterizations demonstrated that the nanogels mainly exist as an interlayer between the polyethersulfone (PES) substrate and polyamide (PA) layer, which elevated the hydrophilicity and electronegativity of the membrane surface. In addition, due to the stronger steric hindrance, electrostatic interaction and interlayer-promoted gutter effect, the optimized NF membrane prepared with the addition of 0.015 wt% amine functionalized PSB (SBMA-AH) in aqueous solution exhibited an exceptional water permeability of 20.6 L m−2 h−1 bar−1 and high Na2SO4 rejection of up to 99.5 %, as well as high selectivity of 160.1 for separating Cl−/SO42−. The membrane also displayed superior performance stability under different salt concentrations and pressures. The outstanding desalination performance of the as-prepared NF membrane enables it a promising candidate for hypersaline wastewater treatment.