Effect of Monovalent and Divalent Salts on the Interfacial Tension of <i>n</i>-Heptane against Aqueous Anionic Surfactant Solutions

Jha, Nilesh Kumar; Iglauer, Stefan; Sangwai, Jitendra S.

doi:10.1021/acs.jced.7b00640

Cited by 36 publications

(31 citation statements)

References 61 publications

(141 reference statements)

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“…The observation that adding salt to a solution of the ionic surfactant further lowers the surface tension has been established. 48,49 An earlier explanation of Jones-Ray-like behavior was proposed by Nichols and Pratt, 50 who predicted a lowering of the surface tension if salt is added to a system with two phases where the salt is soluble in both. Although this study employs a similar physical mechanism, in the case of the airwater interface, it is the difference in the solvation free energy of the ions and surfactant in the interfacial layer that gives rise to the surface potential rather than the solubility of salt in two separate phases.…”

Section: E Alternative Explanationsmentioning

confidence: 99%

Detecting the undetectable: The role of trace surfactant in the Jones-Ray effect

Duignan

Peng

Nguyen

et al. 2018

The Journal of Chemical Physics

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The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the airwater surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration, the surface tension decreases. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we use both experimental surface tension measurements and numerical solution of the Poisson-Boltzmann equation to demonstrate that very low concentrations of surfactant in water create a Jones-Ray effect. We also demonstrate that the low concentrations of the surfactant necessary to create the Jones-Ray effect are too small to be detectable by surface sensitive spectroscopic measurements. The effect of surface curvature on this behavior is also examined, and the implications for unexplained bubble phenomena are discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces.

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Section: E Alternative Explanationsmentioning

confidence: 99%

Detecting the undetectable: The role of trace surfactant in the Jones-Ray effect

Duignan

Peng

Nguyen

et al. 2018

The Journal of Chemical Physics

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show abstract

“…The observation that adding salt to a solution of ionic surfactant further lowers the surface tension has been established. 40,41 An earlier explanation of Jones-Ray like behavior was put proposed by Nichols and Pratt 42 , who predicted a lowering of the surface tension if salt is added to a system with two phases where the salt is soluble in both. Although this study employs a similar physical mechanism, in the case of the air-water interface it is the difference in the solvation free energy of the ions and surfactant in the interfacial layer that…”

Section: A Flat Surfacementioning

confidence: 99%

Surfactant Impurities Can Explain the Jones-Ray Effect

Duignan

Baer²,

Mundy³

2018

Preprint

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<div> <p> </p><div> <div> <div> <p>The surface tension of dilute salt water is a fundamental property that is crucial to understanding the complexity of many aqueous phase processes. Small ions are known to be repelled from the air-water surface leading to an increase in the surface tension in accordance with the Gibbs adsorption isotherm. The Jones-Ray effect refers to the observation that at extremely low salt concentration the surface tension decreases in apparent contradiction with thermodynamics. Determining the mechanism that is responsible for this Jones-Ray effect is important for theoretically predicting the distribution of ions near surfaces. Here we show that this surface tension decrease can be explained by surfactant impurities in water that create a substantial negative electrostatic potential at the air-water interface. This potential strongly attracts positive cations in water to the interface lowering the surface tension and thus explaining the signature of the Jones-Ray effect. At higher salt concentrations, this electrostatic potential is screened by the added salt reducing the magnitude of this effect. The effect of surface curvature on this behavior is also examined and the implications for unexplained bubble phenomena is discussed. This work suggests that the purity standards for water may be inadequate and that the interactions between ions with background impurities are important to incorporate into our understanding of the driving forces that give rise to the speciation of ions at interfaces. </p> </div> </div> </div> </div>

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“…However, the surface tension of the electrolytes shows a characteristic minimum at millimolar electrolyte concentration values when the concentration is varied, known as the Jones-Ray effect [6,7]. The Jones-Ray effect has been controversial, but it has been experimentally reproduced by different methods and by different research groups [8][9][10][11][12][13][14][15]. The Jones-Ray effect was first explained by anion adsorption [16], which was supported by surface-sensitive nonlinear spectroscopy [17].…”

mentioning

confidence: 99%

Intentionally Added Ionic Surfactants Induce Jones-Ray Effect at Air-Water Interface

Uematsu

Chida

Matsubara

2018

Colloid and Interface Science Communications

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The Jones-Ray effect is an anomalous minimum in the surface tension of aqueous electrolytes at millimolar salt concentrations. We experimentally demonstrated that intentionally added ionic surfactants induce the Jones-Ray effect. The one-dimensional Poisson-Boltzmann theory, including the effect of surfactant adsorption and salt depletion, excellently agrees with the obtained experimental data. All the parameters of the ion-specific surface affinities used in the theory are consistent with previous experiments. These results strongly suggest that the Jones-Ray effect observed so far has been induced by the inevitable contamination of the air-water interfaces.

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Effect of Monovalent and Divalent Salts on the Interfacial Tension of n-Heptane against Aqueous Anionic Surfactant Solutions

Cited by 36 publications

References 61 publications

Detecting the undetectable: The role of trace surfactant in the Jones-Ray effect

Detecting the undetectable: The role of trace surfactant in the Jones-Ray effect

Surfactant Impurities Can Explain the Jones-Ray Effect

Intentionally Added Ionic Surfactants Induce Jones-Ray Effect at Air-Water Interface

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