Nanofiltration (NF) membranes with tannic acid (TA) based selective layers have been intensively studied in recent years, but they still suffer from poor inorganic salt rejection. This study provided a first report on mussel-inspired co-deposition of TA and amine to obtain high-performance NF membranes. The inorganic salt separation performance of the as-prepared NF membrane was significantly improved by optimising the amine molecular weight. The membranes prepared by TA and various amines were characterised by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM), zeta potential, and water contact angle measurement. It was found that amines with low molecular weight, such as ethylenediamine (EDA) and diethylenetriamine (DETA) facilitated the co-deposition onto the membrane surface, while polyethylene polyamine (PEPA) and branched polyethylenimine 600 (PEI600) enhanced the precipitation in solution. The TA/DETA co-deposited membrane showed an MgCl2 rejection of 83.5% and a pure water permeance of 4.5 L m-2 h-1 bar-1. The rejection was higher than the reported TA based NF membranes in the literature. In addition to demonstrating a TA based NF membrane with the improved inorganic salt rejection, this study provided new insights into the mussel-inspired co-deposition for material surface engineering towards various applications.
Keywords: Amine; Co-deposition; Inorganic salt rejection; Nanofiltration; Tannic acid.
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