Mechanism of ethanol/water reverse separation through a functional graphene membrane: a molecular simulation investigation

Reverse-selective membranes have attracted considerable interest for bioethanol production. However, to date, the reverse-separation performance of ethanol/water is poor and the separation mechanism is unclear. Graphene-based membranes with tunable apertures and functional groups have shown substantial potential for use in molecular separation. Using molecular dynamics simulations, for the first time, we reveal two-way selectivity in ethanol/water separation through functional graphene membranes. Pristine graphene (PG) exhibits reverse-selective behavior with higher ethanol fluxes than water, resulting from the preferential adsorption for ethanol. Color flow mappings show that this ethanol-permselective process is initiated by the presence of ethanol-enriched and water-barren pores; this has not been reported in previous studies. In contrast, water molecules are preferred for hydroxylated graphene membranes because of the synergistic effects of molecular sieving and functional-group attraction. A simulation of the operando condition shows that the PG membrane with an aperture size of 3.8 & ANGS; achieves good separation performance, with an ethanol/water separation factor of 34 and a flux value of 69.3 kg & BULL;m(-2)& BULL;h(-1)& BULL;bar(-1). This study provides new insights into the reverse-selective mechanism of porous graphene membranes and a new avenue for efficient biofuel production.

Automated summary

Graphene-based membranes with tunable apertures and functional groups have shown potential in ethanol/water separation. Pristine graphene exhibits reverse-selective behavior due to preferential adsorption for ethanol. Ethanol-permselective process is initiated by ethanol-enriched and water-barren pores. In contrast, hydroxylated graphene membranes prefer water molecules due to molecular sieving and functional-group attraction. The study provides insights into the reverse-selective mechanism of porous graphene membranes and a new avenue for efficient biofuel production.