Fabrication of nanofiltration membranes via covalent layer-by-layer self-assembly for charged organic pollutants treatment

Developing a nanofiltration membrane for organic pollutants is regarded as a significant trial. In this work, composite nanofiltration (NF) membranes were reasonably fabricated by alternately impregnating tannic acid (TA) and polyethylene polyamine (PEPA) under the covalent layer-by-layer self-assembly (LBL) method. The covalent LBL is featured as excellent stability and antifouling properties compared with the conventional LBL method. By optimizing the coating parameters, the modified membrane showed a high water flux of 46.52 L m-2 h −1 bar −1 , and the rejection of various dyes with MWCO of 600–1300 Da was above 98%. Notably, the separation pressure of most current nanofiltration membranes is 4–6 bar. In contrast, the modified nanofiltration membrane achieved high rejection at a low pressure of 2.5 bar. In addition, due to the presence of TA and PEPA, it was easy to form a hydrophilic layer on the surface, which improves the antifouling performance of the modified membrane. Therefore, this work not only aims to provide a new method for nanofiltration membrane fabrication but also presents a bright application prospect for charged organic pollutants. Graphical abstract