Facile fabrication of superhydrophilic nanofiltration membranes via tannic acid and irons layer-by-layer self-assembly for dye separation

Co-deposition between plant polyphenol tannic acid (TA) and Fe3+ has been reported to be a facile way to construct nanofiltration (NF) membranes. However, this strategy suffers the problems of low atom economy and generating a large amount of environment-harmful aggregate wastes in solution. This work proposed a novel method based on layer-by-layer (LBL) self-assembly for preparation of TA-Fe3+ complex based NF membrane. The proposed method was facile and environmental-friendly because it did not require any chemical or solvent involved pretreatment nor generated any aggregate waste. A series of characterizations proved the successful formation of TA-Fe3+ complex based top layer on polyacrylonitrile (PAN) support surface. The resultant membrane showed superhydrophilicity property with water contact angle as low as 8°. Meanwhile, the optimized membrane showed a high water permeance of 40.9 L m−2 h−1 bar−1 whilst simultaneously maintained rejections higher than 93.9% towards various dyes with the molecular weight (MW) ranging from 320 to 1017 Da. Moreover, the as-prepared NF membranes showed stable long-term separation performance and good ion/organic selective separation performance. This study not only proposed a facile fabrication process for TA-Fe3+ complex based NF membrane, but also provided great potentials for sustainable molecular separation by the prepared membranes.