The standard gibbs free energy of adsorption and isotherms of adsorption of amphiphilic molecules and clusters at the oil/water and gas/water interfaces: Adsorption of dry and hydrated chlorophyll

Markin, Vladislav S.; Gugeshashvili, M.I.; Volkov, Alexander G.; Munger, G.; Leblanc, Roger M.

doi:10.1016/0021-9797(92)90100-z

Cited by 13 publications

(7 citation statements)

References 9 publications

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“…Elsewhere, the MV or generalized Langmuir isotherm was successfully applied for the study of adsorption at the polarized and nonpolarized nitrobenzene−water, decane−water, and octane−water interfaces in the presence of amphiphilic compounds and for the evaluation of the interfacial structure. − …”

Section: Resultsmentioning

confidence: 99%

“…Pheophytin a is a well-known surfactant molecule that contains a hydrophobic chain (phytol) and a hydrophilic headgroup. The value of p less than 1.0 indicates that adsorbed molecules of n- octane are parallel to the interface between octane and water. − Substitution of one adsorbed octane molecule requires about 4−5 adsorbed pheophytin or chlorophyll molecules. These experimental data are supported by molecular dynamic studies in the systems decane−water, nonane−water, and hexane−water .…”

Section: Theoretical Basis: Generalized Modelmentioning

confidence: 99%

“…Traditional models for calculation of adsorption isotherms − are based on the assumption that surface-active compounds can substitute molecules of only one solvent and cannot penetrate the interface (Figure a). Although these models are useful for metal−water interfaces, recent interest has focused on the electrochemistry of amphiphilic compounds, which can penetrate both phases and replace adsorbed molecules of both solvents, − for example, water and oil (Figure b). Amphiphilic molecules consist of two moieties with opposing properties: a hydrophilic polar head and a hydrophobic tail.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption at Liquid Interfaces: The Generalized Langmuir Isotherm and Interfacial Structure

Markin

Volkova-Gugeshashvili

Volkov

2006

J. Phys. Chem. B

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The thermodynamics of adsorption of amphiphilic surface-active compounds at the interface between two immiscible liquids is considered. At the interface, these molecules are supposed to replace a few of the adsorbed molecules of both solvents. Classical isotherms of adsorption (Frumkin, Langmuir, Henry) were based on the model of nonpenetrable interface, where an adsorbate can substitute only molecules of one solvent. However, at the interface between two immiscible electrolytes, like nonpolar oil-water interfaces, or liquid membrane amphiphilic molecules can substitute molecules of both solvents; therefore, classical isotherms are not applicable in these cases. The generalization of Langmuir and Frumkin isotherms for permeable and nonpermeable interfaces, known as the Markin-Volkov (MV) isotherm, gives the possibility to analyze adsorption and the interfacial structure in a general case. In the present paper, the adsorption isotherms of pentafluorobenzoic acid at the octane-water interface at various pH were measured by the drop-weight method. The thermodynamic parameters of pentafluorobenzoic acid (PFBA) adsorption at the octane-water interface were found. From the measurements of PFBA adsorption, the structure of the octane-water interface was determined. Substitution of one adsorbed octane molecule requires approximately three adsorbed PFBA molecules. This result shows that the orientation of solvent molecules at the interface is different from the bulk solution. Adsorbed octane molecules have a lateral orientation with respect to the interface. Gibbs free energy of adsorption equilibrium and thermodynamic parameters of PFBA adsorption show that the adsorption of PFBA at the octane-water interface is accompanied by a reduction in the attraction between adsorbed PFBA molecules as the pH decreases to the acidic region.

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Section: Resultsmentioning

confidence: 99%

Section: Theoretical Basis: Generalized Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adsorption at Liquid Interfaces: The Generalized Langmuir Isotherm and Interfacial Structure

Markin

Volkova-Gugeshashvili

Volkov

2006

J. Phys. Chem. B

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“…It is based on the amphiphilic isotherm (MV isotherm) . The MV isotherm takes into account the limited number of adsorption sites, final size of the molecules, complex formation at the interface, and interaction between adsorbed molecules. ,,,, …”

Section: Introductionmentioning

confidence: 99%

Structure of Nonpolarizable Water/Nitrobenzene Interface: Potential Distribution, Ion Adsorption, and Interfacial Tension

Markin

Volkov

Volkova-Gugeshashvili

2005

J. Phys. Chem. B

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Adsorption of hydrophobic and hydrophilic ions at the nonpolarizable interface between two immiscible electrolyte solutions was investigated. The results were analyzed in three different models: (i) Gouy-Chapman model, (ii) ions as hard spheres, and (iii) ion pair formation at the interface. In the Gouy-Chapman model, an analytical expression for the interfacial tension was obtained. It predicts that interfacial tension should be proportional to the square root of the electrolyte concentration, which does not agree with experimental data. Modeling ions as hard spheres only slightly improves the agreement. The third model of interfacial ion pairing as the main origin of adsorption was analyzed using the amphiphilic isotherm (Markin-Volkov isotherm). A good agreement between ion-pairing theory and experimental values was achieved. The MV isotherm takes into account the limited number of adsorption sites, final size of molecules, complex formation at the interface, and interaction between adsorbed particles. The analysis revealed repulsion between adsorbed tetraalkylammonium ions at the nitrobenzene/water interface and demonstrated linear dependence between adsorption site area and the size of a molecule.

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“…[4][5][6][7] Aside, EMF (Electro Motive Force) measurements are extremely compelling as they give direct access to the free excess energy and are very adaptable. 8,9 Strangely, despite the booming interest in nanometric materials, they have been seldom applied to the determination of their free surface energy 10 although attempts have been made to track crystal ripening.…”

mentioning

confidence: 99%

Direct Determination of Oxide Surface Free Energy through Potentiometric Measurements

Croué

Jolivet

Larcher

2012

Electrochem. Solid-State Lett.

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The total surface free energy of nanometric particles in contact with a liquid electrolyte can be easily accessed through potentiometric measurements. This requires a special though simple designed set-up, and a careful chemical and textural characterization of the powders. This is here first exemplified for non-stoichiometric NiO, in contact with Ni 2+ aqueous solutions, which total surface free energy was evaluated to 0.34-0.36 J/m 2 for monolithic particles, independently of the level of non-stoichiometry. Much larger values are systematically observed for mosaic powders; hence indicating a large contribution of the solid-solid inter-crystallites interfacial energy or strains.

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The standard gibbs free energy of adsorption and isotherms of adsorption of amphiphilic molecules and clusters at the oil/water and gas/water interfaces: Adsorption of dry and hydrated chlorophyll

Cited by 13 publications

References 9 publications

Adsorption at Liquid Interfaces: The Generalized Langmuir Isotherm and Interfacial Structure

Adsorption at Liquid Interfaces: The Generalized Langmuir Isotherm and Interfacial Structure

Structure of Nonpolarizable Water/Nitrobenzene Interface: Potential Distribution, Ion Adsorption, and Interfacial Tension

Direct Determination of Oxide Surface Free Energy through Potentiometric Measurements

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