Interfacial friction of ethanol–water mixtures in graphene pores

Dai, Haiwei; Liu, Shuyan; Zhao, Mengyao; Xu, Zhijun; Yang, Xiaoning

doi:10.1007/s10404-016-1805-3

Cited by 12 publications

(8 citation statements)

References 45 publications

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“…To further clarify this issue, we calculate the liquid viscosity by considering nanoconfinement, which shows that the values obtained for the graphene and GO nanochannels with d = 4 nm are close to the bulk values except for ethylene glycol that may be attributed to the extended molecular configuration and ordered H-bond network (Figure S1, Table S2). The predicted values of l s and λ are significant under strong spatial confinement because of the appearance of ordered molecular structures at the liquid−wall interfaces (Figures 3a and 4a,b), in consistency with the results reported in recent studies, 23 with which one can then evaluate the flow enhancement factor compared to nonslip flows, ε = 1 + 6l s /d, for molecular liquids confined in graphene nanochannels. 9 Without loss of generality, we will then use the results obtained for the graphene and GO nanochannels with width d = 1.15 nm that corresponds to the formation of bilayer structures of organic liquids and the water trilayer and d = 4 nm as a wide-channel model that can be experimentally accessed at the single-channel level.…”

Section: ■ Results and Discussionsupporting

confidence: 91%

Confined Structures and Selective Mass Transport of Organic Liquids in Graphene Nanochannels

Jiao¹,

Zhou²,

Wu³

et al. 2018

ACS Appl. Mater. Interfaces

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Selective transport of liquids is an important process in the energy and environment industry. The increased energy consumption and the demands of clean water and fossil fuels have urged the development of highperformance membrane technologies. Nanoscale channels with the critical size for molecular sieving and atomistically smooth walls for significant boundary slippage are highly promising to balance the tradeoff between permeability and selectivity. In this work, we explore the molecular structures and dynamics of organic solvents and water, which are confined within nanoscale two-dimensional galleries between graphene or graphene oxide sheets. Molecular dynamics simulation results show that the layered order and significant interfacial slippage are universal for all molecular liquids, leading to notable flow enhancement for channels with a width of few nanometers, in the order of ethylene glycol > butanol > ethanol > hexane > toluene > water > acetone. The extracted dependence of permeability, selectivity on the channel width, and properties of molecular liquids clarify the underlying mechanisms of selective mass transport in nanofluidics, which help to understand and control the filtration and separation processes of molecular liquids. The performance of graphene oxide membranes for permeation and filtration is finally discussed based on the calculated flow resistance for pressure-driven flow or molecular diffusivity for diffusive flow, as well as the solubility and wettability of membranes.

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Section: ■ Results and Discussionsupporting

confidence: 91%

Confined Structures and Selective Mass Transport of Organic Liquids in Graphene Nanochannels

Jiao¹,

Zhou²,

Wu³

et al. 2018

ACS Appl. Mater. Interfaces

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“…This is not surprising because graphitic surfaces are known for their lipophilicity, that is, they interact strongly with hydrocarbons. This is consistent with the recent calculation of larger interfacial friction for ethanol in graphene capillaries compared to water 32 . The non-slip behavior of organic solvents also explains why certain organic molecules (polar solvents) can uniformly intercalate between GO layers, similar to water, but their permeability remains below our detection limit.…”

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confidence: 93%

Ultrathin graphene-based membrane with precise molecular sieving and ultrafast solvent permeation

et al. 2017

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Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation rates 1-9 . However, the membranes' use has been limited mostly to aqueous solutions because GO membranes appear to be impermeable to organic solvents 1 , a phenomenon not fully understood yet. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (

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“…Experimentally, Zhang et al 34 adopted sum-frequency vibrational spectroscopy and demonstrated that alcohols, such as methanol, ethanol, and 1-propanol, were always preferentially adsorbed at hydrophilic fused silica and hydrophobic octyltrichlorosilane-covered surfaces. When Dai et al 35 investigated the friction coefficient of ethanol and water molecule confined in 20-Å-width graphene slits by MD simulation, similar preferential adsorption of alcohols was also observed. As the chain length of alcohol molecules increases, the layered distribution of alcohol and water molecules confined in the slits becomes more obvious, which might be attributed to the decreasing polarity of alcohol molecules.…”

Section: ■ Results and Discussionmentioning

confidence: 77%

“…The gap between the peak positions of methyl and hydroxyl groups is more obvious as the length of the alcohol chain increases. Moreover, compared to the sharp peak of methyl groups, the profiles of hydroxyl groups are broad, which might be attributed to the different configurations exhibited by the alcohol molecules on the graphene surfaces with the different directions of hydroxyl groups …”

Section: Resultsmentioning

confidence: 99%

“…Moreover, compared to the sharp peak of methyl groups, the profiles of hydroxyl groups are broad, which might be attributed to the different configurations exhibited by the alcohol molecules on the graphene surfaces with the different directions of hydroxyl groups. 35 Because the positions of the oxygen atoms are closer to the center of mass of the water molecules, the spatial distribution of confined water molecules is represented by the density distribution and the Y−Z planar density distribution of oxygen atoms, respectively. Although a certain number of water molecule (Figure 3) also exists in the alcohol layer, especially for methanol, this phenomenon rapidly disappears so as to be negligible with the increase of the alcohol chain length.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Effect of Adsorbed Alcohol Layers on the Behavior of Water Molecules Confined in a Graphene Nanoslit: A Molecular Dynamics Study

et al. 2017

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With the rapid development of a two-dimensional (2D) nanomaterial, the confined liquid binary mixture has attracted increasing attention, which has significant potential in membrane separation. Alcohol/water is one of the most common systems in liquid-liquid separation. As one of the most focused systems, recent studies have found that ethanol molecules were preferentially adsorbed on the inner surface of the pore wall and formed an adsorbed ethanol layer under 2D nanoconfinement. To evaluate the effect of the alcohol adsorption layer on the mobility of water molecules, molecular simulations were performed to investigate four types of alcohol/water binary mixtures confined under a 20 Å graphene slit. Residence times of the water molecules covering the alcohol layer were in the order of methanol/water < ethanol/water < 1-propanol/water < 1-butanol/water. Detailed microstructural analysis of the hydrogen bonding (H-bond) network elucidated the underlying mechanism on the molecular scale in which a small average number of H-bonds between the preferentially adsorbed alcohol molecules and the surrounding water molecules could induce a small degree of damage to the H-bond network of the water molecules covering the alcohol layer, resulting in the long residence time of the water molecules.

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Interfacial friction of ethanol–water mixtures in graphene pores

Cited by 12 publications

References 45 publications

Confined Structures and Selective Mass Transport of Organic Liquids in Graphene Nanochannels

Confined Structures and Selective Mass Transport of Organic Liquids in Graphene Nanochannels

Ultrathin graphene-based membrane with precise molecular sieving and ultrafast solvent permeation

Effect of Adsorbed Alcohol Layers on the Behavior of Water Molecules Confined in a Graphene Nanoslit: A Molecular Dynamics Study

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