Ice-crystal templating approach for tailoring mass transfer channels in graphene oxide membranes for high-performance dye/salt separation

Abstract

Abstract Graphene oxide (GO) has been considered as a promising material to develop advanced nanofiltration membranes to resolve the current worldwide water scarcity issue, benefiting from its extraordinary physicochemical properties. However, loose-GO-nanosheet-stacking rendered membrane compaction during operation significantly harms the mass transfer of GO membranes. Here, we proposed an ice-crystal templating approach to simultaneously tailor the two mass transfer channels of GO membranes, i.e., nanochannels originated from the interlayer spacing and microporous defects arising from poorly stacking of nanosheets. The tunability of the ice-crystal templating strategy was verified by low-field nuclear magnetic resonance (LF-NMR) coupled with X-ray diffraction patterns technique. The result demonstrated that the interlayer spacing can be precisely tuned from 7.5 to 9.3\xa0A while the volume of microporous defects can be adjusted from 2.9% to 24.6%. Thus, the optimized GO membrane (M2) was utilized for desalination of dye/NaCl mixtures and accomplished a high separation performance, for example, high water permeability of ∼22.6 LMH/bar (10-fold enhancement compared with traditional GO membranes), 100% rejection to EB dyes, 19% rejection to NaCl, and long-term running stability (180\xa0h). Therefore, the innovative ice-crystal templating fabrication techniques opens the door for the design of high-efficiency 2D material-based membranes.