Graphene oxide hollow fiber membranes for solvent dehydration by nanofiltration

Traditional technologies for solvent/water separation such as distillation and chromatography remain energy intensive. State-of-the-art organic solvent nanofiltration (OSN) membranes exhibit high solvent-solute selectivity, but their ability to discriminate between solvents is limited. Graphene oxide (GO) with homogeneous and tunable 2D nanochannels is a promising solution for this purpose, benefiting from its exceptional transport properties. Here, a one-step pressure-assisted cross-linking strategy was applied to coat GO on the inner surface of hollow fiber membranes. The direction of the external driving force during the assembly of the GO selective layers displays an important influence on the microstructure of the nanochannel and the separation performance. The covalent bonding formed at the GO/polyimide (PI) interface and PI substrate endows the membrane with significantly improved stability in solvent environments. The tunable morphology and hydrophilicity characteristic of the GO layer leads to the rapid transport of acetonitrile while impeding the penetration of water molecules. What's more, the migration route of acetonitrile is shorter than that of water in the cross-linked GO nanochannels. In particular, the cross-linked GO hollow fiber (CGHF) membrane exhibits a high acetonitrile permeance of 145.3 L m⁻²h⁻¹ bar⁻¹, and the dilute acetonitrile solution could be concentrated from 10 wt% to 92.4 ± 3.0 wt%. This means that the elaborately designed nanochannels offer a high energy-efficient prospect for solvent dehydration and OSN.