Tuning interlayer structure to construct steady dual-crosslinked graphene oxide membranes for desalination of hypersaline brine via pervaporation

Graphene oxide (GO) membranes have shown great potential in desalination. However, it is still a challenge to tune the interlayer structure of GO and suppress its swelling in water to realize superior separation performance and enhance the mechanical stability of membrane. Herein, polyethyleneimine (PEI) with different molecular weight was employed to crosslink GO nanosheets and tune interlayer spacing of lamellar GO membrane for desalination of hypersaline brine by pervaporation (PV). A dual crosslinking structure was performed via electrostatic interaction and covalent bonding between PEI and GO rendering effectively restricted swelling of GO. The interlayer spacing was adjusted by tuning PEI molecular weight and the surface charge of GO membrane was converted to positive to repel ions. The membrane crosslinked with larger PEI (c-GO-PEI 70k) exhibited the most robust structure and showed outstanding PV desalination performance with high water flux of 86.0 kg/m(2) h and salt rejection of 99.99% in treating 10 wt% NaCl hypersaline solution at 90 degrees C. This work provides further understanding of regulating interlayer structure and constructing high-performance GO membranes for PV desalination.

Automated summary

This study demonstrates the use of polyethyleneimine (PEI) with different molecular weights to crosslink graphene oxide (GO) nanosheets and tune the interlayer spacing of the GO membrane. The dual crosslinking structure effectively restrains the swelling of GO and enhances the performance of the membrane in desalination. The optimized membrane exhibits outstanding pervaporation (PV) desalination performance with high water flux and salt rejection.