Water transport through graphene oxide membranes: the roles of driving forces

Abstract

Graphene oxide (GO) membranes have shown excellent selectivities in nanofiltration and pervaporation. However, the water transport mechanisms in the unique membrane laminar structure are still not well understood, especially in pervaporation which involves selective permeation and evaporation. Herein, water transport in GO membranes was tested under two different modes: pressure-driven permeation and pervaporation. The pure water flux was found to be 1-2 orders of magnitude higher in pervaporation due to the large capillary pressure induced by evaporation. The water flux in pervaporation was suggested to be limited by evaporation at room temperature but surface diffusion at high temperature.

Towards the dehydration of ethanol using pervaporation cross-linked poly(vinyl alcohol)/graphene oxide membranes

“…This is probably attributed to the loss of the guest water molecules that could be retained in the GO structure, e.g. water molecules trapped in graphitic domains of GO [25], as well as the water retained in the possible interfacial voids between the GO and PVA matrix. Moreover, there was a weight-loss (between 175-275 ºC) for the MMMs, which was more pronounced as the filler loading increased.…”

Functionalizing graphene oxide framework membranes with sulfonic acid groups for superior aqueous mixture separation

“…[10][11] This phenomenon has been widely reported with the d-spacing found to increase from ~0.8 to ~1.3 nm in aqueous environments. [12][13][14][15] Considering the thickness of graphite or well-reduced GO monosheet (ca. 0.34-0.40 nm), [16][17] the 2D nanochannel is accordingly increased from ~0.46 nm to ~0.90 nm.…”

Self-assembly of 2D-metal–organic framework/graphene oxide membranes as highly efficient adsorbents for the removal of Cs+ from aqueous solutions

“…4f). 33 For the GO membranes, it has also been reported that the in-plane oxygen functional groups limit the diffusion of water molecules into the graphene nanochannels due to hydrogen bonds, 34 which further rejects the diffusion of Cs + in solutions into the GO channels, as illustrated in Fig. 4g.…”