Oxidation resistant high permeance PVBTMAC/PSS layer-by-layer self-assembled nanofiltration membrane

Oxidation resistant nanofiltration (NF) membranes have been pursued for wide applications. Mostly researched NF membranes were based on interfacial polymerization (IP) technology, which is not stable in oxidative chemicals. In this paper, a novel layer-by-layer (LBL) self-assembled NF membrane prepared by coating poly(vinylbenzyltrimethylammonium chloride)/poly(styrene sulfonic) (PVBTMAC/PSS) on a polyethersulfone (PES) substrate was presented with exceptionally high permeance and oxidation resistance. The optimized NF membrane of [PVBTMAC/PSS]8.5 demonstrated a pure water permeance (PWP) of 47.6 L/(m2·h·bar) and nearly 100 % rejection for various dyes. The PVBTMAC/PSS membrane showed distinct rejection to asymmetric salts (MgCl2, Na2SO4) following Donnan exclusion. Excellent chlorine resistance was found after 150,000 ppm·h sodium hypochlorite treatment for both [PVBTMAC/PSS]8.5 and [PVBTMAC/PSS]9, demonstrated by the stable rejection to MgSO4 and prussian blue (PB) dye with reduced pore size. Declined rejection to MgCl2 and increased rejection to Na2SO4 was explained by oxidation of the highly active α-H on the aromatic ring side group of PVBTMAC to -COO− and Donnan exclusion effect. The integrity of LBL NF membranes was caused by additional π-π stacking between the polyelectrolytes. Both membranes demonstrated good long-term operational stability for dye separation with great potential for real applications.