Molecular Insight into Water Desalination across Multilayer Graphene Oxide Membranes

Chen, Bo; Jiang, Haifeng; Liu, Xiang; Hu, Xuejiao

doi:10.1021/acsami.7b05307

Cited by 144 publications

(103 citation statements)

References 51 publications

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“…Despite having hydrated size above the channel width, most cations still managed to come through, albeit at much hindered permeability. This implies that “dehydration” or “deformation” effect happens to the hydrated cations when they encounter channels with approximately the same or even smaller size . Practically, hydration shells around ions act more like an elastic sphere and are prone to distort and shrink under confinement.…”

Section: Transport‐controlling Effectsmentioning

confidence: 99%

2D Laminar Membranes for Selective Water and Ion Transport

Kang

Xia

Wang

et al. 2019

Adv Funct Materials

243

148

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energy storage and conversion devices, [26][27][28] as outlined in recent reviews (Figure 1, left). [29] Behind these applications lie a fundamental question: how water and ion transport are controlled in the laminar structure to obtain desired selectivity. A comprehensive summary of structure-transport relation is thereby imperative to understand and optimize membrane selective performance, but is so far lacking. In such context, our review aims to fill this gap by discussing: 1) how 2D materials with specific physicochemical features are assembled into laminar membranes; 2) most importantly, how membrane structure, and its response to external impacts, can tune mass transport (herein, water and ions); 3) how these transport mechanisms translate into selectivity in applications, and into future design of high-performance laminar membranes. Unsolved problems and emerging challenges around these topics are then concluded. We note that the knowledge summarized here can also, at least partly, assist the understanding of the selective gas, liquid, and micromolecule transport through laminar membranes, which are gaining considerable attention as well. [30][31][32] Transition Metal Carbides and/or Nitrides (MXene): MXene nanosheets are etched and delaminated from parent bulk MAX to M n+1 X n T x (e.g., Ti 3 C 2 T x ), and have thus several atom sublayers. [39] While M and X are early transition metal

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Section: Transport‐controlling Effectsmentioning

confidence: 99%

2D Laminar Membranes for Selective Water and Ion Transport

Kang

Xia

Wang

et al. 2019

Adv Funct Materials

243

148

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“…The hydroxyl groups were randomly distributed outside the pore wall with concentration c = OH / C = 24%, which is similar to both experimental [31,32] and simulation [20] results. The allatom optimized potential for liquid simulations (OPLS-AA) [33] was used for the functional groups, which is successfully applied in previous studies on the graphene oxides membrane [19,25,34].…”

Section: Modification Strategies To Reduce Threshold Pressure Dropmentioning

confidence: 99%

How Pore Hydrophilicity Influences Water Permeability?

Wei

Zhang

et al. 2019

Research

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Membrane separation is playing increasingly important role in providing clean water. Simulations predict that membrane pores with strong hydrophobicity produce ultrahigh water permeability as a result of low friction. However, experiments demonstrate that hydrophilic pores favor higher permeability. Herein we simulate water molecules transporting through interlayers of two-dimensional nanosheets with various hydrophilicities using nonequilibrium molecular dynamics. We reveal that there is a threshold pressure drop (ΔPT), exceeding which stable water permeability appears. Strongly hydrophobic pores exhibit extremely high ΔPT, prohibiting the achievement of ultrahigh water permeability under the experimentally accessible pressures. Under pressures < ΔPT, water flows in hydrophobic pores in a running-stop mode because of alternative wetting and nonwetting, thus leading to significantly reduced permeability. We discover that hydrophilic modification to one surface of the nanosheet can remarkably reduce ΔPT by > 99%, indicating a promising strategy to experimentally realize ultrafast membranes.

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“…However in most of the previously reported atomistic simulations on GO membranes, these non-idealities were not taken into consideration. 36,37,[43][44][45][46] In the present study we investigate the effect of these non-idealities on the performance of the layered GO membrane using equilibrium molecular dynamics (MD) simulations. The effect of the non-ideality (i.e.…”

Section: Introductionmentioning

confidence: 99%

Effect of graphene oxide (GO) nanosheet sizes, pinhole defects and non-ideal lamellar stacking on the performance of layered GO membranes: an atomistic investigation

2019

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The effect of non-idealities, namely pinhole defects and non-ideal lamellar stacking of nanosheets, on the performance of size-differentiated graphene oxide (GO) laminates is investigated using equilibrium molecular dynamics (MD) simulations. With the increase in sizes of the constituent GO nanosheets the water permeability of the layered GO membranes decreases and salt rejection increases. But with the inclusion of non-idealities the difference in water permeability between these membranes substantially reduced. The pinholes on the GO nanosheets provide shorter routes for trans-sheet flow, thereby increasing the water permeability of the membranes. The non-ideal stacking of the nanosheets without pinhole defects results in slight reduction in water permeability because of blockage of permeation pathways inside the membranes. However, with pinhole defects non-ideal stacking becomes favorable for water permeation through the layered GO membranes; as this time the non-ideal stacking leads to formation of voids inside the membranes, which act as routes for shorter permeation pathways. The effect of these non-idealities is more significant for layered GO membranes composed of large GO nanosheets. Although the water permeability through the layered GO membrane is greatly enhanced because of these non-idealities (about 10 times), the corresponding variation in the salt rejection is very low (<2%). Tel: +91 361 258 3532 † Electronic supplementary information (ESI) available: A brief description of the OPLS-AA force eld, structure of GO nanosheets, hydrated layered GO membranes with non-ideal lamellar stacking, salt permeation events through layered GO membranes, trajectory of water molecules through layered GO membranes with non-ideal lamellar stacking, trajectory of ions through the layered GO membranes, distribution of permeation time and permeation velocity of the water molecules through the layered GO membranes, spatial distribution of water for the layered GO membranes with W ¼ 0.0Å and W ¼ 8.0Å, variation of water ux with membrane thickness, effect of the number of pinhole defects on the performance of the layered GO membrane, and effect of pinhole sizes on the performance of the layered GO membrane. See

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Molecular Insight into Water Desalination across Multilayer Graphene Oxide Membranes

Cited by 144 publications

References 51 publications

2D Laminar Membranes for Selective Water and Ion Transport

2D Laminar Membranes for Selective Water and Ion Transport

How Pore Hydrophilicity Influences Water Permeability?

Effect of graphene oxide (GO) nanosheet sizes, pinhole defects and non-ideal lamellar stacking on the performance of layered GO membranes: an atomistic investigation

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