Water pumping effect over the organic ions defined graphene oxide membrane impulses high flux desalination

Abstract

Graphene oxide (GO) membranes have shown great potential in ionic sieving from aqueous solutions. However, it remains challenging for GO membranes to exclude small ions with a large water flux. Herein, organic ions are confined onto the GO interlaminations to form a precisely restricted 2D channel size of 0.71 nm, which presents >99.9% NaCl rejections and high freshwater fluxes via the pervaporation method, both being orders of magnitude higher than that of common GO membranes. Theoretical calculations reveal that, apart from controlling the 2D channel size of GO by strong cation–/anion–π and π–π interactions, the organic ions act as vapor traps to remarkably shorten vapor diffusion distance and then as water pumps to significantly enlarge water permeability. It not only theoretically explains the low permeability over the common GO membranes with large 2D channels, but also experimentally demonstrates fast and complete desalination on the organic ions-GO membrane.

Engineering Multinanochannel Polymer-Intercalated Graphene Oxide Membrane for Strict Volatile Sieving in Membrane Distillation

“…Still, the I D /I G of GO/PP of 0.89 was slightly higher than that of the GO membrane of 0.87, suggesting that polymer intercalation and cross-linking did not generate obvious defects within the GO membrane (Figure S4). 23 The resulting membrane exhibits a brown GO layer that uniformly covers the PVDF NFM substrate (the inset in Figure 1B, top), retaining high uniformity after the intercalation and cross-linking processes involving polymers. Field emission scanning electron microscopy (FE-SEM) images and photographs of the resultant membrane also reveal dense and defectfree GO and GO/PP coverage with characteristic wrinkles (Figure 1B, C).…”

A cation–π interaction confined graphene oxide membrane for separation of light paraffins and olefins

“…Due to the weak interactions between GO flakes, the untreated GO membrane is inevitably swollen in water. 6 For the Ag–GO membrane, the peak of the wet sample rises at 8.22°, corresponding to a d -value of 1.07 nm, which is smaller than that of the GO membrane (1.20 nm). This indicates that the cation–π interactions between Ag ions and graphene suppress the water swelling effect.…”

“…In addition, it has been proved that the strong interaction between ions and graphene (i.e., ion-p-effect) can control the channel size and improve the strength of GO membranes. 6 Herein, GO membranes were endowed with paraffin-olefin permselectivity through a simple and facile metal cation intercalation method. The resultant ion-GO membranes exhibit not only high ideal selectivity for C 2 H 6 /C 2 H 4 and C 3 H 8 /C 3 H 6 but also very fast gas permeance.…”

“…This suggests that Ag ion intercalation is a physical process without new defect generation on GO. 6 The permeation performance of the Ag-GO membrane for light paraffins and olefins was firstly measured using a singlegas method. As a control, the GO membrane delivers very close permeance (J) in C 2 H 4 (2.3 Â 10 À7 mol m À2 s À1 Pa À1 ) and C 2 H 6 (2.6 Â 10 À7 mol m À2 s À1 Pa À1 ) as well as in C 3 H 6 (2.1 Â 10 À7 mol m À2 s À1 Pa À1 ) and C 3 H 8 (2.4 Â 10 À7 mol m À2 s À1 Pa À1 ), reflecting the nonselective ideal selectivity (IS) of 1.09 and 1.13 for IS C 2 H 6 /C 2 H 4 and IS C 3 H 8 /C 3 H 6 , respectively (Fig.…”

“…This suggests that Ag ion intercalation is a physical process without new defect generation on GO. 6…”