Preparation of Layer-by-Layer Nanofiltration Membranes by Dynamic Deposition and Crosslinking

In recent decades, the advancements in layer-by-layer (LBL) assembly technology have provoked increasing interest in the preparation of multilayer polyelectrolyte membranes with excellent performance. In the current study, a novel nanofiltration (NF) membrane was prepared by pressure-driven layer-by-layer (LBL) assembly of polyethylenimine (PEI) and polyacrylicacid (PAA) on a porous substrate with chemical crosslinking. The effect of deposition pressure on separation performance of the prepared membranes was studied. The surface morphology, hydrophilicity and the charge property of the dynamically-deposited membranes were compared with those prepared by static adsorption. The characterization results showed that dynamic deposition process resulted in a smoother membrane surface with improved hydrophilicity. The mechanism of water-path formation was proposed to interpret the effect of pressure on the membrane performance. Glutaraldehyde (GA) was used as a crosslinker to reduce the number of polyelectrolyte bilayers for obtaining good separation performance. The rejections of different inorganic salts of the dynamically-deposited NF membrane were also investigated.