Vertically oriented Fe3O4 nanoflakes within hybrid membranes for efficient water/ethanol separation

Abstract Two-dimensional (2D) materials have exhibited tremendous potential as functional fillers of hybrid membranes. Manipulating the orientation of 2D fillers in hybrid membranes, a decisive factor in determining the separation performance, proves a critical challenge. In this study, hybrid membranes with vertical superparamagnetic Fe3O4 nanoflakes and sodium alginate (SA) matrix were prepared via the external magnetic field. The vertically aligned Fe3O4 nanoflakes constructed highly efficient interfacial regions for penetrants transport in hybrid membranes, which shortened the molecular diffusion pathways. In addition, the orientated fillers increased surface hydrophilicity of the hybrid membranes by enhancing the surface roughness. The effect of Fe3O4 nanoflakes orientation and content in hybrid membranes on the separation performance was systematically investigated. When the filler content is 0.4 wt%, the hybrid membrane with vertically aligned Fe3O4 nanoflakes achieved superior ethanol dehydration performance with an optimized selectivity of 3248 ± 233 and a decent water permeability of 1436 ± 169 Barrer, which increased by 68% and 133% compared to the hybrid membranes with horizontally aligned Fe3O4 nanoflakes, respectively. This strategy of manipulating 2D filler orientation may render hybrid membranes with more possibilities for enhanced separation performances.