Self-assembled membranes from polyethylenimine and graphene oxide for pervaporation dehydration of ethylene glycol

Pervaporation membranes were fabricated via layer-by-layer (LbL) self-assembly of polyethylenimine (PEI) and graphene oxide (GO) on a chlorine-treated thin-film-composite polyamide substrate for ethylene glycol (EG) dehydration. The surface morphologies and hydrophilicities of the membranes were characterized. Also investigated was how the number of the PEI/GO bilayers assembled affected the membranes performance. The mass transfer resistances of the PEI/GO bilayer and the substrate to the permeation of water and EG were investigated. The separation factor increased by 148% as the number of the PEI/GO bilayers increased from 1 to 15, at the expense of a 38% reduction in the total flux. The PEI/GO LbL membrane with three bilayers showed a permeation flux of 0.1 kg/(m2 h) and a separation factor of 375 in dehydrating EG at 35 °C and at a water content of 1 wt% in the feed. In view that inorganic salts are often present in aqueous EG solutions in gas and chemical processing, the dehydration of EG in the presence of NaCl was also considered. The separation factor was augmented while the total permeation flux declined when NaCl was present in the feed. In addition, unlike pervaporation separation of binary water/EG solutions for which the temperature had a negative impact on the separation factor, the separation factor for dehydrating EG in the presence of salt increased with an increase in temperature.