Graphene oxide/cross-linked polyimide (GO/CLPI) composite membranes for organic solvent nanofiltration

Purification and recovery of polar organic solvents such as dimethylformamide (DMF) with high chemical separation speed and low energy cost nanofiltration membranes has been widely investigated, while it is still a difficult challenge that high permeability of solvents and rejection of solutes are achieved simultaneously. In this study, a novel organic solvent nanofiltration (OSN) membranes was obtained via coating a thin selective graphene oxide (GO) layer on top of the polyimide porous substrate (PI) which was cross-linked to improve the stability in polar solvents. The resultant GO/cross-linked PI (GO/CLPI) composite membranes feature remarkable sieving capability of >94% for RBss molecules (1018 Da), accompanying high pure solvent permeability of 11.1 L h⁻¹ m⁻² bar⁻¹, 4.9 L h⁻¹ m⁻² bar⁻¹ and 1.0 L h⁻¹ m⁻² bar⁻¹ for water, IPA and DMF, respectively. Different from conventional method of characterization, low field nuclear magnetic resonance technology (LF-NMR) was utilized to confirm that the GO/CLPI membrane shows a higher adsorption capacity for IPA than DMF. This newly technique can be effectively utilized to evaluate the affinity between organic solvents and the surface of membranes.