Surface properties of the ethanol/water mixture: Thickness and composition

Hyde, Anita; Ohshio, Maho; Nguyen, Cuong V.; Yusa, Shin‐ichi; Yamada, Norifumi L.; Phan, Chi

doi:10.1016/j.molliq.2019.111005

Cited by 14 publications

(14 citation statements)

References 39 publications

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“…In addition, the surface layer thicknesses of the binary mixtures (τ) were estimated using eq , listed in Table . The τ values obtained for water–EtOH (∼0.75 nm), water–BuOH (∼1.32 nm), and ACN–MeOH (∼0.36 nm) are close to those reported in the literature (∼0.5 to 1.3 for water–EtOH, ,− ∼0.8 to 1.8 nm for water–BuOH, and ∼0.58 to 1.09 nm for ACN–MeOH). The τ values of aqueous mixtures of alcohols (water–EtOH and water–BuOH) are larger than those of their organic mixtures (other eight systems), suggesting the difference in the adsorption states exists between the two kinds of mixtures.…”

Section: Resultssupporting

confidence: 87%

General Adsorption Model to Describe Sigmoidal Surface Tension Isotherms of Binary Liquid Mixtures

et al. 2022

Langmuir

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Surface tension (σ) isotherms of liquid mixtures can be divided into Langmuir-type (L-type, including LI- and LII-type) and sigmoid-type (S-type, including SI- and SII-type). Many models have been developed to describe the σ-isotherms. However, the existing models can well describe the L-type isotherms, but not the S-type ones. In the current work, a thermodynamic model, called the general adsorption model, was developed based on the assumption of surface aggregation occurring in the surface layers, to relate the surface composition with the bulk one. By coupling the general adsorption model with the modified Eberhart model, a two-parameter equation was developed to relate the σ with the bulk composition. Its rationality was examined using the σ data of 10 binary mixtures. The results indicate that the new model can accurately describe the S- and L-type isotherms of binary liquid mixtures, showing a good universality. One advantage of the model is that its two parameters, i.e., the adsorption equilibrium constant (K) and the average aggregation number (n), can be estimated by linear fitting experimental σ data, thereby obtaining unique values. This model suggests that the S- and LII-type isotherms arise from the surface aggregation (n ≠ 1). In addition, the standard molar Gibbs free energy of surface adsorption (ΔG̃ad 0) and the apparent surface layer thickness (τ) were analyzed for 10 binary mixtures. The ΔG̃ad 0 data suggest that the order of adsorption tendency is LI-type ≫ SI-type ≈ SII-type > LII-type, and the strong adsorption usually corresponds to large τ. This work provides a feasible model for describing the S-type isotherms and a better understanding of the surface properties of liquid mixtures.

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Section: Resultssupporting

confidence: 87%

General Adsorption Model to Describe Sigmoidal Surface Tension Isotherms of Binary Liquid Mixtures

et al. 2022

Langmuir

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“…As a result, in the ethyl alcohol–water solution, ethyl alcohol tends to enrich at the air/water interface, leading to higher concentration of ethyl alcohol at the surface layer compared to that in the bulk. This fact has been studied experimentally by mass spectrometry, , sum-frequency generation vibrational spectroscopy, , and neutron reflection , and theoretically by molecular dynamics simulation and has been well-accepted since the early 20th century. In ethyl alcohol–NaCl aqueous solution, the available space within the interface for ions is reduced by ethyl alcohol and NaCl is a surface-excluded electrolyte .…”

Section: Resultsmentioning

confidence: 99%

Inward Flow of Intervening Liquid Films Driven by the Marangoni Effect during Bubble–Solid Collisions in Ethyl Alcohol–NaCl Aqueous Solutions

et al. 2021

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The drainage dynamics of confined thin liquid films between an air bubble and a freshly cleaved mica surface were investigated in ethyl alcohol aqueous solutions. Focus was given to the holding stage, in which an unexpected increase in the thickness of a few hundred nanometers at the center of the film was captured by interferometry in ethyl alcohol–500 mM NaCl aqueous solutions. Such an increase in film thickness occurred when the ethyl alcohol concentration exceeded the critical value at a bubble approach velocity of 100 μm/s. For a given ethyl alcohol concentration, the increase in thickness at the center of the film did not happen when the bubble approach velocity was decreased to 10 μm/s. Compared to the cases in ethyl alcohol–500 mM NaCl solutions, no increase in thickness at the center of the film was observed in ethyl alcohol–water solutions under the same ethyl alcohol concentration and bubble approach velocity. The phenomenon of the increasing thickness at the center of the film was attributed to the net inward flow in the film, resulting from competition between the inward Marangoni flow and the outward drainage flow that was hindered by the narrow channel at the barrier rim of the film under a high electrolyte concentration. The inward Marangoni flow was achieved by a concentration gradient of ethyl alcohol between the film and the bulk solution resulting from the mobile air–liquid interface in the initial approaching period.

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“…The former can again be deduced from pendant drop measurements, where water adjacent to ethanol-saturated air was found to have an 11.56 mN m –1 higher surface tension than SCS in the same environment (Supporting Information). Molecular dynamics simulations of ethanol–water mixtures confirmed, that, albeit the surface concentration increases nonlinearly with the ethanol bulk concentration, the ethanol concentration at the surface is much lower compared to SCS . This implies that, when evaporation takes place, ethanol and water molecules are transferred to the gas phase.…”

Section: Discussionmentioning

confidence: 99%

Generation and Observation of Long-Lasting and Self-Sustaining Marangoni Flow

et al. 2023

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When solute molecules in a liquid evaporate at the surface, concentration gradients can lead to surface tension gradients and provoke fluid convection at the interface, a phenomenon commonly known as the Marangoni effect. Here, we demonstrate that minute quantities of ethanol in concentrated sodium hydroxide solution can induce pronounced and long-lasting Marangoni flow upon evaporation at room temperature. By employing particle image velocimetry and gravimetric analysis, we show that the mean interfacial speed of the evaporating solution sensitively increases with the evaporation rate for ethanol concentrations lower than 0.5 mol %. Placing impermeable objects near the liquid−gas interface enforces steady concentration gradients, thereby promoting the formation of stationary flows. This allows for contact-free control of the flow pattern as well as its modification by altering the objects shape. Analysis of bulk flows reveals that the energy of evaporation in the case of stationary flows is converted to kinetic fluid energy with high efficiency, but reducing the sodium hydroxide concentration drastically suppresses the observed effect to the point where flows become entirely absent. Investigating the properties of concentrated sodium hydroxide solution suggests that ethanol dissolution in the bulk is strongly limited. At the surface, however, the co-solvent is efficiently stored, enabling rapid adsorption or desorption of the alcohol depending on its concentration in the adjacent gas phase. This facilitates the generation of large surface tension gradients and, in combination with the perpetual replenishment of the surface ethanol concentration by bulk convection, to the generation of longlasting, self-sustaining flows.

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Surface properties of the ethanol/water mixture: Thickness and composition

Cited by 14 publications

References 39 publications

General Adsorption Model to Describe Sigmoidal Surface Tension Isotherms of Binary Liquid Mixtures

General Adsorption Model to Describe Sigmoidal Surface Tension Isotherms of Binary Liquid Mixtures

Inward Flow of Intervening Liquid Films Driven by the Marangoni Effect during Bubble–Solid Collisions in Ethyl Alcohol–NaCl Aqueous Solutions

Generation and Observation of Long-Lasting and Self-Sustaining Marangoni Flow

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