Layer-by-Layer Fabrication of High-Performance Polyamide/ZIF-8 Nanocomposite Membrane for Nanofiltration Applications

The conventional blending fabrication for thin-film nanocomposite (TFN) membranes is to disperse porous fillers in aqueous/organic phases prior to interfacial polymerization, and the aggregation of fillers may lead to the significant decrease in membrane performance. To overcome this limitation, we proposed a novel layer-by-layer (LBL) fabrication to prepare a polyamide (PA)/ZIF-8 nanocomposite membrane with a multilayer structure: a porous substrate, a ZIF-8 interlayer, and a PA coating layer. The PA/ZIF-8 (LBL) membrane for nanofiltration applications was prepared by growing an interlayer of ZIF-8 nanoparticles on an ultrafiltration membrane through in situ growth and then coating it with an ultrathin PA layer through interfacial polymerization. The obtained PA/ZIF-8 (LBL) membrane exhibited both better permeance and selectivity than did the conventional PA/ZIF-8 TFN membrane because of the ZIF-8 in situ growth producing a ZIF-8 interlayer with more ZIF-8 nanoparticles but fewer aggregates. Compared with the pure PA membrane (the flux of 11.2 kg/m(2)/h and rejection of 99.6%) for dye removal, the obtained PA/ZIF-8 (LBL) membranes achieved a significant improvement in membrane permeance and selectivity. (Flux was up to 27.1 kg/m(2)/h, and the rejection reaches 99.8%.) This LBL fabrication is a promising methodology for other polymer nanocomposite membranes simultaneously having high permeance and good selectivity.