Phase separation of binary nonadditive hard sphere fluid mixture confined in random porous media

Chen, W.

doi:10.1063/1.4825178

Cited by 4 publications

(2 citation statements)

References 37 publications

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“…The preferential-adsorption-based separation using porous materials is proposed to be an efficient and energy saving method for ethanol-water separation [5,11]. It has been observed that liquids which are miscible in bulk can be phase segregated when confined at nanoscale [12][13][14]. The preferential attraction by the surface of confining nanopore or the size selective penetration through tunable pore for one of the species of the mixture can lead to their phase separation [15].…”

Section: Introductionmentioning

confidence: 99%

Evidence for confinement induced phase separation in ethanol–water mixture: a positron annihilation study

Muthulakshmi

Dutta

Maheshwari

et al. 2017

J. Phys.: Condens. Matter

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We report an experimental evidence for the phase separation of ethanol-water mixture confined in mesoporous silica with different pore size using positron annihilation lifetime spectroscopy (PALS). A bulk-like liquid in the core of the pore and a distinct interfacial region near the pore surface have been identified based on ortho-positronium lifetime components. The lifetime corresponding to the core liquid shows similar behavior to the bulk liquid mixture while the interfacial lifetime shows an abrupt rise within a particular range of ethanol concentration depending on the pore size. This abrupt increase is attributed to the appearance of excess free-volume near the interfacial region. The excess free-volume is originated due to microphase separation of confined ethanol-water primarily at the vicinity of the pore wall. We envisage that probing free-volume changes at the interface using PALS is a sensitive way to investigate microphase separation under nanoconfinement.

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Section: Introductionmentioning

confidence: 99%

Evidence for confinement induced phase separation in ethanol–water mixture: a positron annihilation study

Muthulakshmi

Dutta

Maheshwari

et al. 2017

J. Phys.: Condens. Matter

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“…Understanding the properties of ethanol–water at interfaces on the molecular level is very important for many chemical and physical processes. − It has been proved by many studies that surface-directed phase separation appears in confined binary mixtures while one component is preferentially attracted to the walls. − However, with regard to the interaction of ethanol–water mixtures with silica surfaces, our atomistic understanding is far from satisfactory. Water molecules can interact with the surface through hydrophobic or hydrophilic interactions and hydrogen bonding.…”

Section: Introductionmentioning

confidence: 99%

Local Microphase Separation of a Binary Liquid under Nanoscale Confinement

2014

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The structural and diffusive properties of an ethanol-water mixture under hydrophilic nanoscale confinement are investigated by means of molecular dynamics simulations based on the CHARMM force field. The resulting density profiles illustrate that demixing of solvents occurs at the pore wall region, which is composed of silanol molecules in our case. Ethanol molecules are more likely to attach to the wall via hydrogen bonds than water molecules. A noticeable O-H bond orientation is observed for the ethanol molecules in this region, which can be explained by the formation of two specific hydrogen bonds between ethanol and silanol. Water, in contrast, resides mostly outside the interfacial region and is in favor of forming small hydrogen bonded strings and clusters with other water molecules. This phenomenon is corroborated by both the orientation of ethanol hydroxyl groups and the radial distribution functions of the solvent oxygen atom to the silanol hydrogen atom. Ethanol selectively attaches to the wall and forms a layer close to the wall. The hydrophobic headgroups of these ethanol molecules lead to an internal hydrophobic interface layer, which in turn yields cluster structures in the adjacent water. The self-diffusion of water in the confined ethanol-water mixture at the center of the pore is faster than that of water in the bulk ethanol-water mixture; ethanol, on the other hand, diffuses slower when it is confined.

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Gibbs ensemble Monte Carlo of nonadditive hard-sphere mixtures

Pellicane

Pandaram

2014

The Journal of Chemical Physics

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In this article, we perform Gibbs ensemble Monte Carlo (GEMC) simulations of liquid-liquid phase coexistence in nonadditive hard-sphere mixtures (NAHSMs) for different size ratios and non-additivity parameters. The simulation data are used to provide a benchmark to a number of theoretical and mixed theoretical/computer simulation approaches which have been adopted in the past to study phase equilibria in NAHSMs, including the method of the zero of the Residual Multi-Particle Entropy, Integral Equation Theories (IETs), and classical Density Functional Theory (DFT). We show that while the entropic criterium is quite accurate in predicting the location of phase equilibrium curves, IETs and DFT provide at best a semi-quantitative reproduction of GEMC demixing curves.

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Phase separation of binary nonadditive hard sphere fluid mixture confined in random porous media

Cited by 4 publications

References 37 publications

Evidence for confinement induced phase separation in ethanol–water mixture: a positron annihilation study

Evidence for confinement induced phase separation in ethanol–water mixture: a positron annihilation study

Local Microphase Separation of a Binary Liquid under Nanoscale Confinement

Gibbs ensemble Monte Carlo of nonadditive hard-sphere mixtures

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