Self-assembly of graphene oxide and polyelectrolyte complex nanohybrid membranes for nanofiltration and pervaporation

Organic–inorganic nanohybrids are believed to be one of the most promising new membrane materials for separation applications. In this study, a new nanohybrid membrane was prepared by incorporating graphene oxide (GO) into polyelectrolyte complexes (PECs). Poly(ethyleneimine)-modified GO and polyacrylic acid were sequentially assembled onto a hydrolyzed polyacrylonitrile ultrafiltration supporting membrane. The nanohybrid membranes were subsequently immersed in polyvinyl alcohol solutions and cross-linked by glutaraldehyde. The assembly process was systematically investigated by scanning electron microscopy, fourier transform infrared analysis, an electrokinetic analyzer, a nano-indenter and thermogravimetric analyzer. The nanoindentation and thermogravimetric experiments in particular indicated that the GO incorporation greatly improved the Young’s modulus, hardness and thermal stability of the membranes. It was found that the resulting membranes had excellent dye removal capacity. The retention of Congo red could reach 99.5% with the permeance of 8.4 kg/m2 h MPa. In the case of the separation of monovalent and divalent ions, such membranes show good nanofiltration properties. The retention of Mg2+ and Na+ were 92.6% and 43.2%, respectively. Additionally, it was demonstrated that this GO/PECs nanohybrid membrane is also a good candidate for the pervaporation dehydration of different solvent–water mixtures. The water content could be enriched from 5.0 wt.% (in the feed) to 95.4 wt.% (in the permeate) with the permeate flux of 268 g/m2h in the pervaporation of ethanol/water mixture (50 °C).