Fabrication of high-performance composite nanofiltration membranes for dye wastewater treatment: mussel-inspired layer-by-layer self-assembly.

Inspired by the mussel adhesion mechanism, plant polyphenol tannic acid (TA) with abundant catechol groups and hydrophilic Jeffamine (JA) containing amino groups were used in a layer-by-layer (LBL) process to fabricate composite nanofiltration (NF) membranes in this study. Alternately immersing a polyacrylonitrile substrate into individual TA and JA buffer solutions could readily construct a NF membrane selective layer without any pre-treatment to the substrate. The optimised membrane showed a high pure water permeance of 37 L m-2 h-1 bar-1 whilst maintaining rejections higher than 90% towards various dyes with molecular weights ranging from 269 to 1017 g mol-1. Particularly, the obtained membrane exhibited excellent anti-fouling and long-term performance attributed to the hydrophilic membrane surface and covalent bonds in the selective layer. The novel strategy inherited the advantages of a mussel-inspired dopamine material but overcame its disadvantages. The results disclosed in this study not only provide a novel strategy to prepare composite NF membranes, but also facilitate the mussel-inspired LBL design of advanced materials for environmental applications.