Enhanced separation performance of composite nanofiltration membranes via electrostatic air spray PSS/PEI interlayer

Thin-film composite (TFC) membranes with an interlayer were prepared extensively for desalination, but the hydrophilicity and permeability were not well improved. In this work, a smooth and hydrophilic interlayer was constructed by electrostatic air spray deposition (EASD) of poly (sodium 4-styrenesulfonate) (PSS) and polyethyleneimine (PEI) on the polyethersulfone substrate and an ultra-thin separation layer was prepared using interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) to acquire high-performance composite nanofiltration (NF) membranes. The polymer solution was atomized into tiny particles under a high-pressure electrostatic air spray effect, facilitating the deposition of PSS/PEI with good homogeneity and enabling a denser and smoother interlayer surface. The introduction of PSS/PEI enhanced the hydrophilicity of TFC membranes and increased the repulsion of divalent cations to improve the salt rejection. The impacts of PEI concentration and EASD time on the separation performance of NF membrane were explored. The optimized TFC-3 NF membrane had a permeate flux of 74.5 ± 1.6 L·m−2·h−1 under 0.5 MPa, which was 2.5 times higher than the water flux of conventional TFC-0 membrane, while retaining up to 99.2 ± 0.5 % of Na2SO4. This work provides a prospective strategy to develop high-performance TFC membranes with great extensive progress for seawater purification.