The adsorption of tri-N-butylphosphate at the benzene–water interface

1982 ◽  
Vol 60 (10) ◽  
pp. 1244-1249 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee ◽  
Michael J. Quinn
Keyword(s):  
Gas Chromatography ◽  
Equations Of State ◽  
Adsorbed Layer ◽  
Distribution Coefficients ◽  
Vapor Pressure Osmometry ◽  
Water Interface ◽  
Free Energies ◽  
Drop Volume ◽  
Enthalpy Of Adsorption ◽  
Strong Adsorption

Adsorption of tri-n-butylphosphate (TBP) at the benzene–water interface was studied as a function of the TBP mole fraction in benzene up to 0.018 and at temperatures from 9 to 29 °C. The extent of adsorption was calculated from interfacial tension data obtained by the drop-volume technique. Standard free energies of adsorption from benzene ranged from −20.9 kJ/mol at 9 °C to −22.5 kJ/mol at 29 °C, giving a standard enthalpy of adsorption of +2.5 kJ/mol. Thus the strong adsorption occurs because of entropy changes. Distribution coefficients for the partition of TBP between benzene and water were measured by gas chromatography, and standard free energies of adsorption from water were derived. They ranged from −44.8 kJ/mol at 9 °C to −51.1 kJ/mol at 29 °C, with standard enthalpies of adsorption ranging from 74 to 15 kJ/mol over the same temperature range.Results at higher mole fractions were fitted to various equations of state, after using vapor pressure osmometry (at 37 °C) to determine that activity corrections were small. The Schofield–Rideal equation described the results adequately, with A0 close to 1.0 nm2 and/close to 1.0 at lower temperatures. These values imply that lateral repulsion between TBP molecules in the adsorbed layer is minimal.

The adsorption of tri-n-butylphosphate at the n-dodecane–water interface

1979 ◽  
Vol 57 (10) ◽  
pp. 1218-1223 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee ◽  
Michael J. Quinn
Keyword(s):  
Mole Fraction ◽  
Model Equation ◽  
Equations Of State ◽  
Water Interface ◽  
Two Dimensional ◽  
Free Energies ◽  
Dimensional Solution ◽  
Simple Version ◽  
Enthalpy Of Adsorption ◽  
Gas Laws

The adsorption of tri-n-butylphosphate (TBP) from n-dodecane to the n-dodecane–water interface has been studied as a function of TBP mole fraction up to 2.7 × 10−4 in the n-dodecane, and as a function of temperature from 293.15 K to 308.15 K. Free energies of adsorption were calculated from the results at low TBP mole fractions, where the surface pressures were linear with mole fraction. They were in the range −36.1 to −35.6 kJ/mol. The enthalpy of adsorption, determined from the variation of the free energies of adsorption with temperature, was −45.4 kJ/mol.Several equations of state based on two-dimensional gas laws were applied to the results. The Schofield–Rideal equation described the results adequately but the simpler Volmer equation was inadequate especially at lower temperatures. Deviations from the Volmer equation were in the direction of higher surface pressure. A simple version of the two-dimensional solution model equation of state was not helpful.

The adsorption of lower trialkylphosphates at the dodecane – water interface

1980 ◽  
Vol 58 (24) ◽  
pp. 2789-2795 ◽  
Author(s):  
Norman H. Sagert ◽  
Woon Lee
Keyword(s):  
Equation Of State ◽  
Chain Length ◽  
Water Interface ◽  
Two Dimensional ◽  
Free Energies ◽  
Dimensional Solution ◽  
Interfacial Tensions ◽  
Enthalpy Of Adsorption ◽  
Solution Models ◽  
Methylene Group

The adsorption of tripropylphosphate, triethylphosphate, and trimethylphosphate at the dodecane–water interface has been studied at temperatures from 293 to 313 K. Standard free energies of adsorption were obtained from the lowering of interfacial tensions in the low (< 10−4) solute mole fraction region. Standard enthalpies and entropies of adsorption were then obtained from the temperature variation of the standard free energies of adsorption.Standard free energies of adsorption from dodecane showed little variation with solute chain length, with the exception of trimethylphosphate. On the other hand, free energies of adsorption from water decreased by 3.45 kJ/mol for each methylene group added, again with the exception of trimethylphosphate. Enthalpies of adsorption increased linearly with increasing solute chain length for adsorption from either phase. For each methylene group added, the enthalpy of adsorption from dodecane increased by 2.9 kJ/mol, while that from water increased by 2.4 kJ/mol.Results for tripropylphosphate adsorption and for triethylphosphate adsorption at higher temperatures could be adequately described by the Schofield–Rideal equation of state, but not by simple two-dimensional solution models. Results for trimethylphosphate adsorption and for triethylphosphate adsorption at lower temperatures could not be fitted adequately by either type of equation of state.

Surface active properties at the air–water interface of β-casein and its fragments derived by plasmin proteolysis

1989 ◽  
Vol 56 (3) ◽  
pp. 487-494 ◽  
Author(s):  
Michael Wilson ◽  
Daniel M. Mulvihill ◽  
William J. Donnelly ◽  
Brian P. Gill
Keyword(s):  
Surface Tension ◽  
Water Interface ◽  
Active Protein ◽  
Drop Volume ◽  
V Protein ◽  
Proteose Peptone ◽  
Rate Determining Step ◽  
Surface Active Properties ◽  
Air Water Interface ◽  
Surface Active

Summaryβ-Casein, was enzymically modified by incubation with plasmin to yield γ-caseins and proteose peptones. Whole γ-, γ1-, γ2/γ3-caseins and whole proteose peptone (pp) were isolated from the hydrolysate mixture. The time dependence of surface tension at the air-water interface of solutions of β-casein and its plasmin derived fragments, at concentrations of 10−1 to 10−4% (w/v) protein, pH 7.0, was determined, at 25 °C, using a drop volume apparatus. The ranking of the proteins with respect to rate of reduction of surface tension, during the first rate determining step, at 10-2% (w/v) protein, was γ2/γ3 ≫ pp > whole γ- > γ1- > β-casein. The ranking of the proteins with respect to surface pressures attained after 40 min (π40) was concentration dependent. γ2/γ3-Caseins were found to be very surface active, decreasing surface tension rapidly and giving a high π40. γ1 Casein decreased surface activity somewhat faster than β-casein, but generally reached a lower π40. Whole γ-casein reflected the properties of both γ1 and γ2/γ3-caseins. Proteose peptone was found to decrease surface tension rapidly during the initial rate determining step; it gave a relatively high π40 at a bulk phase concentration of 10−3% (w/v) protein, but, it was the least surface active protein at 10−1 and 10−2% (w/v) protein.

scholarly journals Free Energy Contribution to Gas Chromatographic Separation of Petroselinate and Oleate Esters

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Chanida Sansa-ard ◽  
Kornkanok Aryusuk ◽  
Supathra Lilitchan ◽  
Kanit Krisnangkura
Keyword(s):  
Fatty Acids ◽  
Molecular Weight ◽  
Gas Chromatography ◽  
Driving Force ◽  
Capillary Column ◽  
Free Energies ◽  
Energy Contribution ◽  
Free Energy Contribution ◽  
Gas Chromatographic Separation ◽  
Different Parts

The ease of separation by gas chromatography between petroselinic and oleic acids depends on the alcohol moieties of their esters. The esters of higher molecular weight alcohols tend to be better separated on a 90%-biscyanopropyl-10%-cyanopropylphenyl polysiloxane capillary column (30 m × 0.25 mm i.d.). By analysis of free energies contribution from different parts of the molecules, it is tentatively concluded that the interaction between the double bond and the column stationary phase is interfered by the bulky alkyl group, and it is the major driving force for the separation of the two fatty acids.

scholarly journals Determination of the surface properties of kaolinite by inverse gas chromatography

2018 ◽  
Vol 2017 (2) ◽  
pp. 319-328 ◽  
Author(s):  
Ceyda Bilgiç
Keyword(s):  
Gas Chromatography ◽  
Free Energy ◽  
Inverse Gas Chromatography ◽  
Specific Enthalpy ◽  
Free Energy Of Adsorption ◽  
Dispersive Component ◽  
Enthalpy Of Adsorption ◽  
Kaolinite Surface ◽  
Acceptor Numbers

Abstract Inverse gas chromatography (IGC) was applied to characterize the surface of kaolinite. The adsorption thermodynamic parameters (the standard enthalpy (∆H0), entropy (∆S0) and free energy of adsorption (∆G0), the dispersive component of the surface energy (γsd), and the acid/base character of kaolinite surface were estimated by using the retention time of different non-polar and polar probes at infinite dilution region. The specific free energy of adsorption (∆Gsp), the specific enthalpy of adsorption (∆Hsp), and the specific entropy of adsorption (∆Ssp) of polar probes on kaolinite were determined. (∆Gsp) values were correlated with the donor and modified acceptor numbers of the probes to quantify the acidic (KA) and the basic (KD) parameters of the kaolinite surface. The values obtained for the parameters KA and KD indicated a basic character for kaolinite surface.

scholarly journals Термомеханика деформаций в ангармоническом твердом теле

2019 ◽  
Vol 61 (4) ◽  
pp. 765
Author(s):  
Н.Н. Горобей ◽  
А.С. Лукьяненко
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of State ◽  
Interatomic Interaction ◽  
The Body ◽  
Free Energies ◽  
External Temperature ◽  
Interatomic Interaction Potential ◽  
Interaction Potential Energy ◽  
Classical Region ◽  
Temperature Force

AbstractThe macroscopic laws determining the temperature and deformations of an anharmonic solid body in a given external temperature force field have been stated in the form of the first thermodynamics law supplemented by equations of state of the body. The internal and free energies necessary for it are found from the statistical sum in which some of degrees of freedom determining the body shape are discharged from statistical averaging. These functions of state have been calculated up to the first order of the perturbation theory in the anharmonicity for the microscopic dynamic model of the body with the interatomic interaction potential energy given as a series in powers of atom coordinates. The classical region of high temperatures is considered.

Solvation Free Energies and Adsorption Energies at the Metal/Water Interface from Hybrid QM-MM Simulations

2020 ◽  
Author(s):  
Paul Clabaut ◽  
Benjamin Schweitzer ◽  
Andreas Goetz ◽  
Carine Michel ◽  
Stephan Steinmann
Keyword(s):  
Free Energy ◽  
Adsorption Energy ◽  
Metallic Surface ◽  
Implicit Solvent ◽  
Water Interface ◽  
Free Energies ◽  
Hybrid Scheme ◽  
Aromatic Molecules ◽  
Solvent Model ◽  
Metal Water

Modeling adsorption at the metal/water interfaces is a corner-stone towards an improved understanding in a variety of fields from heterogeneous catalysis to corrosion. We propose and validate a hybrid scheme that combines the adsorption free energies obtained in gas phase at the DFT level with the variation in solvation from the bulk phase to the interface evaluated using a molecular mechanics based alchemical transformation, denoted MMsolv. Using the GAL17 force field for the platinum/water interaction, we retrieve a qualitatively correct interaction energy of the water solvent at the interface. This interaction is of near chemisorption character and thus challenging, both for the alchemical transformation, but also for the fixed point-charge electrostatics. Our scheme passes through a state characterized by a well-behaved physisorption potential for the Pt(111)/H<sub>2</sub>O interaction to converge the free energy difference. The workflow is implemented in the freely available SolvHybrid package. We first assess the adsorption of a water molecule at the Pt/water interface, which turns out to be a stringent test. The intrinsic error of our QM-MM hybrid scheme is limited to 6 kcal/mol through the introduction of a correction term to attenuate the electrostatic interaction between near-chemisorbed water molecules and the underlying Pt atoms. Next, we show that the MMsolv solvation free energy of Pt (-0.46 J/m<sup>2</sup>) is in good agreement with the experimental estimate (-0.32 J/m<sup>2</sup>). Furthermore, we show that the entropy contribution at room temperature is roughly of equal magnitude as the free energy, but with opposite sign. Finally, we compute the adsorption energy of benzene and phenol at the Pt(111)/water interface, one of the rare systems for which experimental data are available. In qualitative agreement with experiment, but in stark contrast with a standard implicit solvent model, the adsorption of these aromatic molecules is strongly reduced (i.e., less exothermic by ~30 and 40 kcal/mol for our QM/MM hybrid scheme and experiment, respectively, but ~0 with the implicit solvent) at the solid/liquid compared to the solid/gas interface. This reduction is mainly due to the competition between the organic adsorbate and the solvent for adsorption on the metallic surface. The semi-quantitative agreement with experimental estimates for the adsorption energy of aromatic molecules thus validates the soundness of our hybrid QM-MM scheme.

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