Layer-by-layer assembly of graphene oxide and polyelectrolyte composite membranes for monovalent cation separation

Abstract

Graphene oxide (GO) composite membranes were fabricated via layer-by-layer (LBL) assembling poly(ethylenimine) (PEI) and a mixture of GO and poly(acrylic acid) (PAA) on a poly(acrylonitrile) (PAN) support membrane. The composite membranes and their application performance were characterized and evaluated. The X-ray powder diffraction (XRD) spectrum shows that GO was successfully synthesized by the modified Hummers method, and it was homogenously dispersed in the composite membranes. Scanning electron microscopy (SEM) shows the successful assembly of multiple polyelectrolyte PEI and a mixture of GO and PAA bilayers on the PAN support membrane. The ultraviolet-visible (UV-Vis) spectrum indicates that the uniformity and continuity of the composite membrane were enhanced with the increasing number of assembled layers. The hydrophilic and selectivity tests reveals that the addition of GO decreased the water contact angle and enhanced the selectivity for monovalent cations of the multilayer polyelectrolyte composite membranes. All these advantages combine to fabricate a high-flux, high selectivity, and anti-fouling composite membrane for separation applications and water softening.