Journal articles: 'Gibbs surface excess of solutes'

1

A., Gani, Bhadra R., K. Chattoraj D., C. Mukherjee D., and Mitra Atanu. "Thermodynamics of excess binding of inorganic salts and organic solutes to crab hemocyanin." Journal of Indian Chemical Society 93, May 2016 (2016): 553–61. https://doi.org/10.5281/zenodo.5639349.

Full text

Abstract:

Department of Food Technology and Biochemical Engineering, Jadavpur University, Kolkata-700 032, India Indian Institute of Chemical Biology, Kolkata-700 032, India Department of Chemistry, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009, India Manuscript received 06 January 2016, accepted 23 March 2016 Using isopiestic vapor pressure technique, extents of water bound to complex metaloprotein hemocyanin obtained from crab have been determined in the absence and presence of inorganic salts, sucrose and urea at a fixed temperature. The water vapor absorption curve for hemocyanin in the range of water activity varying between zero to unity is type III BET isotherm. Moles of water absorbed per kg of hemocyanin at unit water activity a1 have been evaluated by extrapolation method and the results support several models of bound water for different ranges of al. The standard free energies of adsorption ΔG0 for water-protein interaction at different temperatures have been calculated using Bull equation in integrated form. Based on Clausius-Clapeyron equation in integrated form, the integral enthalpy for water-hemocyanin interaction has also been evaluated. Using the isopiestic technique, values of excess binding ofsolute г2 1 and г1 2 excess binding of solvent per kg of hemocyanin in the presence of different bulk mole-fractions X2 of solutes (LiCl, NaCl, KCl, NaBr, NaI, KSCN, urea, and sucrose) have been calculated in each case from the evaluated values of the Gibbs surface excess. In certain ranges of solute concentration, the plot of г1 2.X2 vs X1 becomes linear so that moles of water and solute bound per kg of hemocyanin respectively can be calculated. X1 and X2 stand for the mole-fraction of the solvent and solute in the bulk phase of the sample. Also, using integrated form of the Gibbs adsorption equation, standard free energy change (ΔG0) for the solute-hemocyanin and the solvent-hemocyanin interactions for different systems have been computed and the values have been compared critically.

APA, Harvard, Vancouver, ISO, and other styles

2

Tasneem, Shadma. "Tensiometric and Thermodynamic Study of Aliphatic and Aromatic Amine in Aqueous D-Glucose Solutions: A Comparative Study." Applied Sciences 13, no. 12 (2023): 7012. http://dx.doi.org/10.3390/app13127012.

Full text

Abstract:

The surface tensions of aqueous taurine (TAU) and tyramine (TYR) with D-glucose mixed solvents were elevated from 298.15 to 318.15 K by the KSV sigma 702 tensiometer. The purpose of the study was to elucidate comparative studies of the thermodynamic and transport aggregation properties of aliphatic and aromatic amine, i.e., taurine and tyramine, which provide information in pharmacology and biochemistry. The experimental data investigated by this study were utilized to evaluate various interfacial parameters, including surface pressure, surface excess concentration, and other thermodynamic parameters of surface assembly, which are discussed in terms of solute–solvent and solute–solute interactions. The surface tension data have been analyzed using the Gibbs adsorption isotherm. The results signify that the negative isotherm exhibited by the ionic solute, i.e., taurine, an aliphatic amine, is contrary to the positive isotherm of tyramine, a biogenic aromatic amine. Both the amines exhibit surface properties such as surfactant molecules, which is elucidated in terms of ionic–hydrophilic and hydrophobic–hydrophobic interactions. The positive entropy values state that the process of surface formation is favored by entropy gain as well as the enthalpy effect. The present system provides a better understanding of the intermolecular interactions, which are required for their usefulness in the field of nutrition, pharmacy, and the food industry.

APA, Harvard, Vancouver, ISO, and other styles

3

Reddy, Ramana G., and Singareddy R. Reddy. "Derivation and consistency of the partial functions of a ternary system involving interaction coefficients." International Journal of Materials Research 95, no. 9 (2004): 806–12. http://dx.doi.org/10.1515/ijmr-2004-0149.

Full text

Abstract:

Abstract Margules equations are used to express the thermodynamics of a ternary system containing one solvent and two solutes in the vicinity of solvent, in terms of first order interaction coefficients of binary and ternary systems. Considering just the first order Margules coefficients, the resultant excess Gibbs energy function was convergent and the derived logarithmic activity coefficients of solvent and solutes were thermodynamically consistent. In the present study Margules equations are modified to get consistent equations. Partial functions of a ternary system are deduced using these modified equations via the excess Gibbs energy function. Derived partial functions are thermodynamically consistent and also deduced results are the same as those obtained using Maclaurin infinite series. Using the activity coefficient expressions of solvent and solutes, the activity coefficients of solvent and solute are calculated in Ni– Cr–Fe and Fe–Ti –C ternary systems, which are in excellent agreement with the experimental data.

APA, Harvard, Vancouver, ISO, and other styles

4

Killmann, E. "Adsorption and the Gibbs surface excess." Journal of Colloid and Interface Science 112, no. 2 (1986): 602. http://dx.doi.org/10.1016/0021-9797(86)90132-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Peterson, I. R. "Bulk aspects of the Gibbs surface excess parameters." Colloids and Surfaces A: Physicochemical and Engineering Aspects 102 (September 1995): 21–29. http://dx.doi.org/10.1016/0927-7757(95)03248-c.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Postigo, Miguel A., José L. Zurita, María L. G. De Soria, and Miguel Katz. "Excess thermodynamic properties of n-pentane + dichloromethane system at 298.15 K." Canadian Journal of Chemistry 64, no. 10 (1986): 1966–68. http://dx.doi.org/10.1139/v86-325.

Full text

Abstract:

Densities, refractive indices, viscosities, enthalpies, vapour–liquid equilibria, and surface tensions were determined for the n-pentane + dichloromethane system at 298.15 K. From the experimental results, excess molar volumes, excess viscosities, excess molar enthalpies, excess molar Gibbs free energies, and excess surface tensions were calculated. From these data, qualitative information could be obtained about the interaction between both chemical species.

APA, Harvard, Vancouver, ISO, and other styles

7

Sah, D. K., D. Adhikari, and S. K. Yadav. "Temperature-Dependence of Mixing Properties of Cu-Ti Liquid Alloy." Adhyayan Journal 10, no. 10 (2023): 1–10. http://dx.doi.org/10.3126/aj.v10i10.57306.

Full text

Abstract:

In this study, the temperature-dependence of thermodynamic and surface properties of Cu-Ti binary liquid alloy were studied. In thermodynamic properties, excess Gibbs free energy of mixing, enthalpy of mixing, excess entropy of mixing, and activity of the system were computed at 1873 K. The surface properties were analyzed by computing the surface tension and surface concentration of the system. Thermodynamic properties were computed in the framework of the Redlich-Kister polynomial, and the surface properties were computed using the Butler model. At its melting point, the system exhibited a tendency for the formation of compounds, and as the Cu concentration was increased, the surface tension of the system gradually decreased. The excess Gibbs free energy of mixing, activity and surface tension of the system were also computed at different temperatures, in the range 1873-2173 K. With the increase in temperature of the system, the compound forming tendency of the system gradually decreased.

APA, Harvard, Vancouver, ISO, and other styles

8

DELGADO, Daniel R., Andrés R. HOLGUÍN, and Fleming MARTÍNEZ. "SOLUTION THERMODYNAMICS OF TRICLOSAN AND TRICLOCARBAN IN SOME VOLATILE ORGANIC SOLVENTS." Vitae 19, no. 1 (2012): 79–92. http://dx.doi.org/10.17533/udea.vitae.10838.

Full text

Abstract:

Thermodynamic functions of Gibbs energy, enthalpy, and entropy for the solution processes of the antimicrobial drugs Triclosan and Triclocarban in five volatile organic solvents were calculated from solubility values at temperatures from 293.15 to 313.15 K. Triclosan and Triclocarban solubility was determined in acetone, acetonitrile (AcCN), ethyl acetate (AcOEt), methanol (MetOH), and cyclohexane (CH). The excess of Gibbs energy and the activity coefficients of the solutes were also calculated. The Triclosan solubilities were greater than those of Triclocarban in all the solvents studied. At 298.15 K the solubility diminished for Triclosan in the order, acetone > AcOEt > AcCN > MetOH > CH, while it diminished for Triclocarban in the order, acetone > AcOEt > MetOH > AcCN > CH. On the other hand, thermodynamic quantities relative to the transfer process of these drugs from CH to all other organic solvents, as well as from water to organic solvents for Triclosan were also calculated in order to estimate the hydrogen-bonding contributions.

APA, Harvard, Vancouver, ISO, and other styles

9

Yadav, S. K., N. Chaudhary, and D. Adhikari. "Thermodynamic, structural, surface and transport properties of Au-Ni liquid alloy at 1150 K." BIBECHANA 18, no. 1 (2021): 184–92. http://dx.doi.org/10.3126/bibechana.v18i1.30546.

Full text

Abstract:

Thermodynamic, structural, surface, and transport properties of Au-Ni liquid alloy at 1150 K were computed using different theoretical approaches. The thermodynamic properties, such as excess Gibbs free energy of mixing, enthalpy of mixing, activity and excess entropy of mixing, and structural properties, such as concentration fluctuation in long-wavelength limit and Warren-Cowley short-range order parameter were computed in the framework of Flory’s model. The effect of positive and negative values of the interchange energy parameter on the excess Gibbs free energy of mixing and concentration fluctuation in the long-wavelength limit was also observed. The surface tension and surface concentration of the system were calculated using Butler’s model. In the transport property, the viscosity of the system was calculated using Kaptay and Budai-Benko-Kaptay (BBK) models. BIBECHANA 18 (2021) 184-192

APA, Harvard, Vancouver, ISO, and other styles

10

Tanaka, Toshihiro, Nev A. Gokcen, Dieter Neuschütz, Philip J. Spencer, and Zen-ichiro Morita. "Estimation of partial excess Gibbs energy of solutes in infinitely dilute liquid iron base binary alloys." Steel Research 62, no. 9 (1991): 385–89. http://dx.doi.org/10.1002/srin.199101317.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Udoh, Tinuola, and Jan Vinogradov. "Experimental Investigations of Behaviour of Biosurfactants in Brine Solutions Relevant to Hydrocarbon Reservoirs." Colloids and Interfaces 3, no. 1 (2019): 24. http://dx.doi.org/10.3390/colloids3010024.

Full text

Abstract:

In this study, we investigated the behaviour of rhamnolipid and Greenzyme in brine solutions relevant to hydrocarbon reservoir. Prior to this work, several studies only reported the behaviour of the biosurfactants dissolved in sodium chloride solutions of varied salinity. The results of this study are relevant to the application of the biosurfactants in enhanced oil recovery, during which the compounds are injected into reservoir saturated with formation water, typically of high salinity and complex composition. Surface tension and conductivity methods were used to determine the critical micelle concentrations of the biosurfactants, Gibbs surface excess concentrations and standard free energy at water-air interface. The results show that rhamnolipid and Greenzyme could reduce the surface tension of water from 72.1 ± 0.2 mN/m to 34.7 ± 0.4 mN/m and 47.1 ± 0.1 mN/m respectively. They were also found to be stable in high salinity and high temperature with rhamnolipid being sensitive to brine salinity, composition and pH while Greenzyme showed tolerance for high salinity. Furthermore, the Gibbs standard free energy of micellisation shows that rhamnolipid and Greenzyme have the tendency to spontaneously form micelles with rhamnolipid showing more surface adsorption. However from maximal Gibbs surface excess concentration calculations, Greenzyme monomers tend to favour aggregation more than that of rhamnolipid.

APA, Harvard, Vancouver, ISO, and other styles

12

Yadav, Shashit Kumar. "Thermodynamic, structural and surface properties of rare earth metallic alloys: Au-La liquid system." BIBECHANA 20, no. 3 (2023): 316–25. http://dx.doi.org/10.3126/bibechana.v20i3.59896.

Full text

Abstract:

A complete information related to the mixing behaviours of Au alloyed with rare earth metals or lanthanides is very scarce. Therefore, an attempt has been made in this work to compute and study the temperature and concentration dependent thermodynamic, structural and surface properties of Au-La liquid alloy using different theoretical approaches. The thermodynamic properties, such as excess Gibbs free energy of mixing, enthalpy of mixing, excess entropy of mixing and activity of the system were computed using available coefficients of interaction energy parameters in the framework of Redlich-Kister polynomial. Taking these as reference values, model parameters for quasi-lattice model were optimised at 1473 K. The model parameters were then determined at higher temperatures assuming them to be linear temperature-dependent. The thermodynamic and structural properties were then computed in the temperature range 1473 K-1773 K. The surface properties of the system were computed using Bulter’s model using determined values of partial excess Gibbs free energy of its components. Present investigations revealed that the compound forming tendency of the system gradually decreased with increase in temperature of the system.

APA, Harvard, Vancouver, ISO, and other styles

13

Dong, W. "Thermodynamics of interfaces extended to nanoscales by introducing integral and differential surface tensions." Proceedings of the National Academy of Sciences 118, no. 3 (2021): e2019873118. http://dx.doi.org/10.1073/pnas.2019873118.

Full text

Abstract:

As a system shrinks down in size, more and more molecules are found in its surface region, so surface contribution becomes a large or even a dominant part of its thermodynamic potentials. Surface tension is a venerable scientific concept; Gibbs defined it as the excess of grand potential of an inhomogeneous system with respect to its bulk value per interface area [J. W. Gibbs, “The Collected Works” in Thermodynamics (1928), Vol. 1]. The mechanical definition expresses it in terms of pressure tensor. So far, it has been believed the two definitions always give the same result. We show that the equivalence can break down for fluids confined in narrow pores. New concepts of integral and differential surface tensions, along with integral and differential adsorptions, need to be introduced for extending Gibbs thermodynamics of interfaces. We derived two generalized Gibbs adsorption equations. These concepts are indispensable for an adequate description of nanoscale systems. We also find a relation between integral surface tension and Derjaguin’s disjoining pressure. This lays down the basis for measuring integral and differential surface tensions from disjoining pressure by using an atomic force microscope.

APA, Harvard, Vancouver, ISO, and other styles

14

Yadav, S. K., U. Mehta, and R. K. Gohivar. "Thermodynamic, structural, surface and transport properties of Au-Cu melt." BIBECHANA 21, no. 2 (2024): 150–58. http://dx.doi.org/10.3126/bibechana.v21i2.66853.

Full text

Abstract:

Thermodynamic, structural, surface and transport properties of Au-Cu liquid alloy were calculated on the basis of different theoretical modeling equations. The thermodynamic properties, such as excess Gibbs free energy of mixing, enthapy of mixing and activity were estimated and compared with the available experimental and literature data on the basis of simple theory of mixing (STM). The best fit values of model parameters were estimated using the experimental values of excess Gibbs free energy of mixing and enthalpy of mixing of the system at 1550 K. Using the same model parameters and frame, the concentration fluctuation in long wave-length limit and Warren-Cowley short range order parameter were calculated and analysed to understand the local arrangement of atoms in the liquid mixture. The surface tension and extent of surface segregation of atoms in the initial melt were computed using Butler’s model. In transport properties, the ratio of mutual to intrinsic diffusion coefficients was calculated using STM and viscosity was calculated using Kaptay equation. The system showed complete ordering tendency at its melting temperature.

APA, Harvard, Vancouver, ISO, and other styles

15

Jácome, Paulo A. D., Daniel J. Moutinho, Laercio G. Gomes, Amauri Garcia, Alexandre F. Ferreira, and Ileao L. Ferreira. "The Application of Computational Thermodynamics for the Determination of Surface Tension and Gibbs-Thomson Coefficient of Aluminum Ternary Alloys." Materials Science Forum 730-732 (November 2012): 871–76. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.871.

Full text

Abstract:

Casting simulation requires high quality information about the thermophysical properties of the alloy, but the number of alloys for which such information is available is limited. In this paper, a solution of Butler’s formulation for surface tension is presented for Al-Cu-Si ternary alloys and consequently, permitting the Gibbs-Thomson coefficient to be determined. The importance of the Gibbs-Thomson coefficient is related to the reliability of predictions furnished by predictive microstructure growth models and of numerical computations of solidification thermal variables, which will be strongly dependent on the values of the thermophysical properties adopted in the calculations. The Gibbs-Thomson coefficient for ternary alloys is seldom reported in the literature. A numerical model based on Powell hybrid algorithm and on a finite difference Jacobian approximation was coupled with a ThermoCalc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Cu-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.

APA, Harvard, Vancouver, ISO, and other styles

16

Samsonov, V. M., S. A. Vasilev, I. V. Talyzin, K. K. Nebyvalova, and V. V. Puitov. "Nanothermodynamics on the Example of Metallic Nanoparticles." Журнал физической химии 97, no. 8 (2023): 1167–77. http://dx.doi.org/10.31857/s004445372308023x.

Full text

Abstract:

After analyzing the problem of extending the Gibbs surface excess method to nanoscale objects, two different approaches to the application of the Gibbs method for finding the specific surface energy of metal nanoparticles are being considered. The first approach involves the use of the local coordination approximation to estimate the specific surface energy of icosahedral FCC metal nanoparticles (magic nanoclusters). For the first time, we have drawn attention to the fact that for such a nanocluster, it is possible to accurately calculate both the fraction of surface atoms and the values of the first coordination number in the inner region of the nanoparticle and on its surface (faces, edges, and vertices). The second approach implemented by us earlier for spherical Au nanoparticles and here for FCC Pt nanoparticles, involves the complex application of the Gibbs method adapted for nanoparticles and the results of molecular dynamics simulation. Estimates using both approaches agree with the experimental values of the surface energy corresponding to the flat surface of the bulk phases of the corresponding metals. In the final section of the work, the limits of applicability of thermodynamics to nanosystems are discussed.

APA, Harvard, Vancouver, ISO, and other styles

17

Jácome, Paulo A. D., Marcio T. Fernandes, Amauri Garcia, Alexandre F. Ferreira, José Adilson de Castro, and Ivaldo Leão Ferreira. "Application of Computational Thermodynamics to the Evolution of Surface Tension and Gibbs-Thomson Coefficient during Multicomponent Aluminum Alloy Solidification." Materials Science Forum 869 (August 2016): 416–22. http://dx.doi.org/10.4028/www.scientific.net/msf.869.416.

Full text

Abstract:

Numerical simulation of multicomponent alloy solidification demands accuracy of thermophysical properties in order to obtain a numerical representation as close as possible to the physical reality. Some alloy properties are only seldom found in the literature. In this paper, a solution of Butler’s formulation for surface tension is presented for Al-Cu-Si ternary alloys, allowing the Gibbs-Thomson coefficient to be calculated as a function of Cu and Si contents. The importance of the Gibbs-Thomson coefficient is related to the reliability of predictions furnished by predictive microstructure growth models and of numerical computations of solidification thermal variables that will be strongly dependent on the values of the thermophysical properties adopted in the calculations. A numerical model based on Powell hybrid algorithm and a finite difference Jacobian approximation was coupled with a ThermoCalc TCAPI interface to assess the excess Gibbs energy of the liquid phase, permitting the surface tension and Gibbs-Thomson coefficient for Al-Cu-Si hypoeutectic alloys to be calculated. The computed results are presented as a function of the alloy composition.

APA, Harvard, Vancouver, ISO, and other styles

18

Mukherjee, Indrajyoti, Satya P. Moulik, and Animesh K. Rakshit. "Tensiometric determination of Gibbs surface excess and micelle point: A critical revisit." Journal of Colloid and Interface Science 394 (March 2013): 329–36. http://dx.doi.org/10.1016/j.jcis.2012.12.004.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Lukša, Algimantas, Virginijus Bukauskas, Viktorija Nargelienė, et al. "Influence of Growth Time and Temperature on Optical Characteristics and Surface Wetting in Nano-Crystalline Graphene Deposited by PECVD Directly on Silicon Dioxide." Crystals 13, no. 8 (2023): 1243. http://dx.doi.org/10.3390/cryst13081243.

Full text

Abstract:

Unique electronic properties of graphene offer highly interesting ways to manipulate the functional properties of surfaces and develop novel structures which are sensitive to physical and chemical interactions. Nano-crystalline graphene is frequently preferable to crystalline monolayer in detecting devices. In this work, nano-crystalline graphene layers were synthesized directly on SiO2/Si substrates by plasma-enhanced chemical vapour deposition (PECVD). The influence of the deposition time and temperature on the characteristics of the structures were studied. The optical properties and evaporation kinetics of pure water droplets were analysed, along with arrangement and composition of the grown layers. The nano-crystalline graphene layers grown at 500 °C were characterised by the refraction index 2.75 ± 0.35 and the normalised excess Gibbs free energy density 0.85/γwater 10−4 m, both being similar to those of the monolayer graphene. The changes in the refraction index and the excess Gibbs free energy were related to the parameters of the Raman spectra and a correlation with the technological variables were disclosed.

APA, Harvard, Vancouver, ISO, and other styles

20

Cao, Liu, and Yugui Zhang. "Interpretation of Gibbs surface excess model for gas adsorption on heterogeneous coal particle." Fuel 214 (February 2018): 20–25. http://dx.doi.org/10.1016/j.fuel.2017.10.109.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Szaniawska, Magdalena, Katarzyna Szymczyk, Anna Zdziennicka, and Bronisław Jańczuk. "Thermodynamic Parameters of Berberine with Kolliphor Mixtures Adsorption and Micellization." Molecules 28, no. 7 (2023): 3115. http://dx.doi.org/10.3390/molecules28073115.

Full text

Abstract:

The poor solubility of berberine (Ber) in water limits its practical use. Its solubility can be increased, among other ways, by the addition of surfactants. Of the surfactants, Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) can be very useful in this respect. The increase of Ber’s solubility in water in the presence of ELP and RH40 should be reflected in the composition of the surface layers at the water-air interface and the micelles. The determined composition is reflected in the Gibbs energy of interactions of berberine with ELP and RH40 through the water phase and the standard Gibbs free energy, enthalpy, and entropy of adsorption and micellization. These energies were determined from the equations proposed by us, based on the Gibbs surface excess concentration of the Ber mixture with ELP and RH40, the activity of these compounds in the surface layer at the water-air interface and in the micelles obtained by the Hua and Rosen method, and the contributions of Ber, ELP, and RH40 to the reduction in the water surface tension. For this determination, the measurements of the surface tension of the aqueous solution of the Ber mixture with ELP or RH40 and that of the Ber mixture with these two surfactants, as well as the density and conductivity were performed. Moreover, the fluorescence emission spectra for the Ber + surfactant mixtures were recorded.

APA, Harvard, Vancouver, ISO, and other styles

22

Saba, Jadwiga. "The Mixed Adsorption Layers of Butanol/Thiourea and Butanol/Toluidine at the Interface Hg/Aqueous Perchlorate Solution." Collection of Czechoslovak Chemical Communications 61, no. 7 (1996): 999–1009. http://dx.doi.org/10.1135/cccc19960999.

Full text

Abstract:

Properties of mixed, two-component adsorption layers of butanol/thiourea, butanol/m-toluidine and butanol/p-toluidine in 1 M NaClO4 were investigated. The systems were characterized by the measurements of differential capacity, zero charge potential and surface tension at this potential. The data were analyzed to obtain the surface pressure and relative surface excess of thiourea, m-toluidine or p-toluidine as a function of charge and bulk concentration of these substances. The standard Gibbs energy of adsorption and parameters α, B obtained from the Frumkin and virial isotherms were compared. The electrostatic parameters of the inner layer were determined.

APA, Harvard, Vancouver, ISO, and other styles

23

Zarbaliyeva, I., A. Alimova, H. Nabiyeva, S. Ahmadbayova, and A. Mammadov. "NEW SURFACE-ACTIVE PETROCOLLECTING AND PETRODISPERSING REAGENT BASED ON STEARIC ACID AND TRYETHYLENETETRAAMINE." ASJ 1, no. 54 (2021): 39–44. http://dx.doi.org/10.31618/asj.2707-9864.2021.1.54.123.

Full text

Abstract:

New surfactant was synthesized from stearic and triethylenetetraamine at room temperature, without utilizing any catalyst or solvent. Structure and composition of the salt was confirmed by using IR-, NMR- and UV- spectroscopies . Surface tension, conductivity measurements were performed on aqueous solutions of new surfactant. Its surface activity and colloidal-chemical parameters such as critical micelle concentration (CMC), surface pressure at CMC (πCMC), surface tension at CMC (γCMC), surface excess (Γmax), concentration required for 20 mN/m reduction of surface tension (C20), Gibbs energies of adsorption and micellization (ΔGad and ΔGmic) were determined. Moreover, corrosion properties and petrocollecting and petrodispersing properties of this salt was determined and maximum values of petrocollecting coefficients was calculated.

APA, Harvard, Vancouver, ISO, and other styles

24

Bermúdez-Salguero, Carolina, and Jesús Gracia-Fadrique. "Gibbs Excess and the Calculation of the Absolute Surface Composition of Liquid Binary Mixtures." Journal of Physical Chemistry B 119, no. 17 (2015): 5598–608. http://dx.doi.org/10.1021/acs.jpcb.5b01436.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Gąsior, W., P. Fima, and Z. Moser. "Modeling of the Thermodynamic Properties of Liquid Fe-Ni and Fe-Co Alloys From the Surface Tension Data." Archives of Metallurgy and Materials 56, no. 1 (2011): 13–23. http://dx.doi.org/10.2478/v10172-011-0002-3.

Full text

Abstract:

Modeling of the Thermodynamic Properties of Liquid Fe-Ni and Fe-Co Alloys From the Surface Tension DataRecently proposed method of modeling of thermodynamic properties of liquid binary alloys from their surface tension data is described. The method utilizes Melford and Hoar equation, relating surface tension with excess Gibbs free energy, combined with new description of the monatomic surface layer and β parameter. The method is tested on Fe-Ni and Fe-Co alloys and the obtained results show very good agreement with experimental thermodynamic data of other authors. The model allows also to calculate the surface tension from thermodynamic data, and it gives better agreement with experimental results than those modeled with the use of Butler equation and traditionally defined monatomic surface layer and β = 0.83.

APA, Harvard, Vancouver, ISO, and other styles

26

Kukučka, Miroslav, and Nikoleta Kukučka Stojanović. "Intrinsic Dependence of Groundwater Cation Hydraulic and Concentration Features on Negatively Charged Thin Composite Nanofiltration Membrane Rejection and Permeation Behavior." Membranes 12, no. 1 (2022): 79. http://dx.doi.org/10.3390/membranes12010079.

Full text

Abstract:

Commercial nanofiltration membranes of different molecular weight cut-offs were tested on a pilot plant for the exploration of permeation nature of Ca, Mg, Mn, Fe, Na and ammonium ions. Correlation of transmembrane pressure and rejection quotient versus volumetric flux efficiency on nanofiltration membrane rejection and permeability behavior toward hydrated divalent and monovalent ions separation from the natural groundwater was observed. Membrane ion rejection affinity (MIRA) dimension was established as normalized TMP with regard to permeate solute moiety representing pressure value necessary for solute rejection change of 1%. Ion rejection coefficient (IRC) was introduced to evaluate the membrane rejection capability, and to indicate the prevailed nanofiltration partitioning mechanism near the membrane surface. Positive values of the IRC indicated satisfactory rejection efficiency of the membrane process and its negative values ensigned very low rejection affinity and high permeability of the membranes for the individual solutes. The TMP quotient and the efficiency of rejection for individual cations showed upward and downward trends along with flux utilization increase. Nanofiltration process was observed as an equilibrium. The higher the Gibbs free energy was, cation rejection was more exothermic and valuably enlarged. Low Gibbs free energy values circumferentially closer to endothermic zone indicated expressed ions permeation.

APA, Harvard, Vancouver, ISO, and other styles

27

Krawczyk, Joanna, Joanna Karasiewicz, and Katarzyna Wojdat. "Experimental and Thermodynamic Study on the Temperature-Dependent Surface Activity of Some Polyether Siloxane Surfactants at the Water–Air Interface." International Journal of Molecular Sciences 26, no. 12 (2025): 5472. https://doi.org/10.3390/ijms26125472.

Full text

Abstract:

Measurements of the surface tension of aqueous solutions of some trisiloxane surfactants containing various polyether groups (HOL7, HOL9, and HOL12) at 293 K, 303 K, and 313 K were performed. The studied surfactants were synthesized by hydrosilylation reaction and their structural analysis was carried out by the 1H NMR, 13C NMR, 29Si NMR, as well as FT-IR techniques. The thermal stability of HOL7, HOL9, and HOL12, as well as their molecular weight distributions, were also studied. On the basis of the obtained experimental results of the surface tension of aqueous solutions of HOL7, HOL9, and HOL12, the activity of the studied surfactants at the water–air interface was determined and discussed in the light of intermolecular interactions. Using the measured values of the surface tension, the Gibbs surface excess concentration, the area occupied by the surfactant molecule in the adsorption layer, and the standard Gibbs free energy of adsorption of the studied surfactants at the water–air interface were also calculated. Based on the obtained thermodynamic parameters of adsorption of the studied surfactants at the water–air interface, temperature, as well as a number of polyether groups in the hydrophilic part of surfactant, impact on particular surfactant adsorption was deduced. In general, the changes in the standard Gibbs free energy of adsorption of the studied surfactants at the water–air interface indicate that their adsorption tendency decreases with decreasing temperature. In addition, that tendency also diminishes as the number of the polyether groups in the hydrophilic part of the surfactant increases.

APA, Harvard, Vancouver, ISO, and other styles

28

Bogacki, M. B., J. Szymanowski, and K. Prochaska. "Application of spline functions in calculating the surface excess isotherm according to the gibbs isotherm." Analytica Chimica Acta 206 (1988): 215–21. http://dx.doi.org/10.1016/s0003-2670(00)80843-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Strubinger, Joseph R., and Jon F. Parcher. "Surface excess (Gibbs) adsorption isotherms of supercritical carbon dioxide on octadecyl-bonded silica stationary phases." Analytical Chemistry 61, no. 9 (1989): 951–55. http://dx.doi.org/10.1021/ac00184a007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Li, Qi, Yong Wu, and Lei Qiao. "Supercritical Methane Adsorption Characteristics and Pore Structure Characteristics of Deep Middle Rank Coal." Journal of Physics: Conference Series 2860, no. 1 (2024): 012045. http://dx.doi.org/10.1088/1742-6596/2860/1/012045.

Full text

Abstract:

Abstract In order to accurately analyze the adsorption characteristics, pore structure, and fractal law of deep middle rank coal, high-pressure isothermal adsorption tests based on magnetic levitation high-pressure thermobalance and pore structure tests based on mercury intrusion method were carried out on coal samples collected from typical kilometer level deep wells. The fractal law of sponge model was studied. The results showed that: a. The weight method adsorption test showed “excess adsorption” phenomenon with the increase of equilibrium pressure, and the modified Gibbs surface excess adsorption theory was in line with the Langmuir adsorption model; b. The distribution of macropore volume in deep middle rank coal accounts for a dominant proportion of 57.44% to 62.47%, and the proportion of microporous specific surface area reaches 72.96% to 74.27%, indicating that microporous adsorption capacity is the strongest; c. The pore structure parameters and adsorption constants exhibit strong nonlinear characteristics.

APA, Harvard, Vancouver, ISO, and other styles

31

Rustamova, I. V., and R. A. Rahimov. "Synthesis and properties of Gemini surfactant based on dodecyldiethylolammonium, dodecyltriethylolammonum bromide and potassium oxalate." Azerbaijan Oil Industry, no. 06 (June 15, 2023): 63–67. http://dx.doi.org/10.37474/0365-8554/2023-06-07-63-67.

Full text

Abstract:

The article focuses on the synthesis of Gemini cationic surfactants using dodecyldiethylolammonium bromide (DDDEAB), dodecyltriethylolammonium bromide (DDTEAB) and 2:1 mol potassium oxalate (PO). The structure of the obtained substances was determined using IR-spectroscopy. The study examines the surface tension and electrical conductivity of the new surfactants in aqueous solutions with different concentrations. The parameters such as critical micelle concentration, degree of counterion binding, effectiveness of surface tension reduction, surface excess concentration, surface area polar group per molecule at the air-water interface, Gibbs free energy values of adsorption and micellar formation processes were calculated. The article investigates the petroleum collecting and dispersing properties as well. Collecting and dispersing ability of the surfactants on a petroleum sample from Pirallahi field under laboratory conditions were observed.

APA, Harvard, Vancouver, ISO, and other styles

32

Raatikainen, T., and A. Laaksonen. "A simplified treatment of surfactant effects on cloud drop activation." Geoscientific Model Development 4, no. 1 (2011): 107–16. http://dx.doi.org/10.5194/gmd-4-107-2011.

Full text

Abstract:

Abstract. Dissolved surface active species, or surfactants, have a tendency to partition to solution surface and thereby decrease solution surface tension. Activating cloud droplets have large surface-to-volume ratios, and the amount of surfactant molecules in them is limited. Therefore, unlike with macroscopic solutions, partitioning to the surface can effectively deplete the droplet interior of surfactant molecules. Surfactant partitioning equilibrium for activating cloud droplets has so far been solved numerically from a group of non-linear equations containing the Gibbs adsorption equation coupled with a surface tension model and an optional activity coefficient model. This can be a problem when surfactant effects are examined by using large-scale cloud models. Namely, computing time increases significantly due to the partitioning calculations done in the lowest levels of nested iterations. Our purpose is to reduce the group of non-linear equations to simple polynomial equations with well known analytical solutions. In order to do that, we describe surface tension lowering using the Szyskowski equation, and ignore all droplet solution non-idealities. It is assumed that there is only one surfactant exhibiting bulk-surface partitioning, but the number of non-surfactant solutes is unlimited. It is shown that the simplifications cause only minor errors to predicted bulk solution concentrations and cloud droplet activation. In addition, computing time is decreased at least by an order of magnitude when using the analytical solutions.

APA, Harvard, Vancouver, ISO, and other styles

33

Jańczuk, Bronisław, Katarzyna Szymczyk, and Anna Zdziennicka. "Adsorption Properties of Hydrocarbon and Fluorocarbon Surfactants Ternary Mixture at the Water-Air Interface." Molecules 26, no. 14 (2021): 4313. http://dx.doi.org/10.3390/molecules26144313.

Full text

Abstract:

Measurements were made of the surface tension of the aqueous solutions of p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethylene glycols) having 10 oxyethylene groups in the molecule (Triton X-100, TX100) and cetyltrimethylammonium bromide (CTAB) with Zonyl FSN-100 (FC6EO14, FC1) as well as with Zonyl FSO-100 (FC5EO10, FC2) ternary mixtures. The obtained results were compared to those provided by the Fainerman and Miller equation and to the values of the solution surface tension calculated, based on the contribution of a particular surfactant in the mixture to the reduction of water surface tension. The changes of the aqueous solution ternary surfactants mixture surface tension at the constant concentration of TX100 and CTAB mixture at which the water surface tension was reduced to 60 and 50 mN/m as a function of fluorocarbon surfactant concentration, were considered with regard to the composition of the mixed monolayer at the water-air interface. Next, this composition was applied for the calculation of the concentration of the particular surfactants in the monolayer using the Frumkin equation. On the other hand, the Gibbs surface excess concentration was determined only for the fluorocarbon surfactants. The tendency of the particular surfactants to adsorb at the water-air interface was discussed, based on the Gibbs standard free energy of adsorption which was determined using different methods. This energy was also deduced, based on the surfactant tail surface tension and tail-water interface tension.

APA, Harvard, Vancouver, ISO, and other styles

34

Kishimoto, Naoyuki, and Honami Kimura. "Fouling behaviour of a reverse osmosis membrane by three types of surfactants." Journal of Water Reuse and Desalination 2, no. 1 (2012): 40–46. http://dx.doi.org/10.2166/wrd.2012.065.

Full text

Abstract:

The fouling behaviour of a reverse osmosis (RO) membrane by three types of surfactants and a countermeasure to the fouling were studied. The filtration experiments showed that the permeability during filtration depended on the surfactant concentration and the charge of surfactant. Higher surfactant concentration deteriorated the permeability due to the concentration polarization. A negatively charged anionic surfactant, sodium lauryl sulfate (SLS), had less influence on the permeability than cationic and non-ionic surfactants. As the RO membrane used in this research had a hydrophilic and negatively charged membrane surface, adsorption of the anionic surfactant was prevented by the electrostatic force between the membrane surface and the hydrophilic group of the surfactant. To control the fouling by the cationic and non-ionic surfactants, addition of SLS to the surfactant solution was tested. Consequently, the addition of excess SLS changed the surface charge of aggregates into more negative value and the permeability during filtration was successfully improved. Furthermore, the drop in pure water permeability after filtration was not observed by the addition of excess SLS. Thus, the modification of charge of solutes to the same sign of the membrane surface charge was thought to be useful to control a membrane fouling by surfactants.

APA, Harvard, Vancouver, ISO, and other styles

35

Parsons, Roger. "Gibbs’ method, Guggenheim's method and the surface excess as measured by thermodynamic methods and radiotracer methods." Journal of Electroanalytical Chemistry 484, no. 1 (2000): 97–98. http://dx.doi.org/10.1016/s0022-0728(00)00056-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Oli, P., D. K. Sah, U. Mehta, R. K. Gohivar, and S. K. Yadav. "Thermodynamic, Structural and Surface Properties of Liquid Al-Sr Alloy at Different Temperatures." Adhyayan Journal 11, no. 11 (2024): 24–32. http://dx.doi.org/10.3126/aj.v11i11.67053.

Full text

Abstract:

Thermodynamic functions like excess Gibbs free energy of mixing (∆GxsM) and activity (a) of liquid Al-Sr alloy were studied in the temperature range 1323-1623 K in the frame work of Redlich-Kister (R-K) polynomial. The compositional and temperature dependence of structural functions like concentration fluctuation in long wavelength limit (Scc(0)), Warren-Cowley short range order parameter (α) and ratio of mutual to intrinsic diffusion coefficients (Dm/Did) were computed and analysed using the same approach. The surface tension (σ) and surface segregation (xsi) tendencies of the atoms in the liquid mixture were computed and studied using Butler’s model. Present investigations revealed that association tendency among the atoms of metallic mixture gradually decreased with increase in temperature.

APA, Harvard, Vancouver, ISO, and other styles

37

Shah, Sujit Kumar, and Ajaya Bhattarai. "Interfacial and Micellization Behavior of Cetyltrimethylammonium Bromide (CTAB) in Water and Methanol-Water Mixture at 298.15 to 323.15 K." Journal of Chemistry 2020 (June 29, 2020): 1–13. http://dx.doi.org/10.1155/2020/4653092.

Full text

Abstract:

The micellization behavior of cetyltrimethylammonium bromide (CTAB) in water , 0.1, 0.2, 0.3, and 0.4 volume fractions of methanol at 298.15, 308.15, 318.15, and 323.15 K were investigated by surface tension measurements. The effect of methanol on values of critical micelle concentration (cmc), free energies of micellization ΔGmo, and surface properties viz. maximum surface excess concentration Γmax, area occupied by per surfactant molecule Amin, surface pressure πcmc, solution surface tension γcmc, solvent surface tension (γo), free energies of adsorption ΔGadso, the efficiency of adsorption (pC20), effective Gibbs free energy ΔGeffo, and free energy of surface at equilibrium (Gmin) were investigated using surface tension values. Other parameters such as the packing parameter (P), aggregation number (N), concentration of surfactant in the bulk phase (C20), relation between Amin and πcmc, and correlation of slopes dγ/d log C, γo/γcmc, Γ/Γmax, cmc/C20, ΔGadso/ΔGmo, and cmc/pC20 with the volume fraction of methanol are calculated and discussed in the light of the experiment done.

APA, Harvard, Vancouver, ISO, and other styles

38

Mehta, Upendra, Ramesh K. Gohivar, and Shashit Kumar Yadav. "Thermodynamic and surface properties of Sr–Si Liquid Alloy at Different Temperatures." Journal of Knowledge and Innovation 9, no. 2 (2023): 39–47. http://dx.doi.org/10.3126/jki.v9i2.67249.

Full text

Abstract:

Thermodynamic and surface properties of Sr–Si liquid alloy have been estimated and explained at different temperatures using quasi–lattice model and Butler’s model respectively. The interaction energy parameters, also called model parameters have been determined using the available literature data for excess Gibbs free energy of mixing. The reliability of the model parameters has been obtained by comparing the results of present work with the values of thermodynamic functions calculated using literature data. The mixing behaviour of the system have been analysed by reproducing the thermodynamic, structural and surface properties of the system at 1080 K using optimised model parameters. The temperature dependence of model parameters have been then calculated by assuming their temperature derivative terms to be constant for small change in temperature of the system.

APA, Harvard, Vancouver, ISO, and other styles

39

Urbina-Villalba, German, Sabrina DiScipio, and Neyda Garcia-Valera. "A NOVEL ALGORITHM FOR THE ESTIMATION OF THE SURFACTANT SURFACE EXCESS AT EMULSION INTERFACES." REVISTA DEL CENTRO DE ESTUDIOS INTERDISCIPLINARIOS DE LA FISICA 2 (June 1, 2013): 1–16. https://doi.org/10.5281/zenodo.5565574.

Full text

Abstract:

When the theoretical values of the interfacial tension -resulting from the homogeneous distribution of ionic surfactant molecules amongst the interface of emulsion drops- are plotted against the total surfactant concentration, they produce a curve comparable to the Gibbs adsorption isotherm. However, the actual isotherm takes into account the solubility of the surfactant in the aqueous bulk phase. Hence, assuming that the total surfactant population is only distributed among the available oil/water interfaces, one can calculate what surface concentration is necessary to reproduce the experimental values of the interfacial tension. A similar procedure can be followed using the zeta potential of the drops as a standard for a given set of salt and surfactant concentrations. We applied these procedures to the case of hexadecane/water nanoemulsions at different salt concentrations. This information was used to compute typical interaction potentials between non-deformable nanoemulsion drops. The results indicate that there are significant differences between the surfactant population expected from macroscopic adsorption isotherms, and the actual surfactant population adsorbed to the surface of nanoemulsion drops.

APA, Harvard, Vancouver, ISO, and other styles

40

Stottlemyer, R., and D. Toczydlowski. "Pattern of Solute Movement from Snow into an Upper Michigan Stream." Canadian Journal of Fisheries and Aquatic Sciences 47, no. 2 (1990): 290–300. http://dx.doi.org/10.1139/f90-031.

Full text

Abstract:

Precipitation, snowpack, snowmelt, and streamwater samples were collected in a small gauged watershed draining into Lake Superior during winter 1987–88 to assess the importance of snowmelt pattern and meltwater pathways in the occurrence of solute pulses in streamwater. The snowpack along the south shore of Lake Superior can contain 50% of annual precipitation inputs and 38% of annual ionic inputs including moderate levels of strong acids. Throughout winter, thawed surface soils and small but steady snowpack moisture release promoted movement of snowpack solutes to surface mineral soils. Preferential elution of K+, NH4+, and H+ from the snowpack occurred with the initial thaw. Most ions exhibited pulses in snowmelt. Transport of snowpack solutes to the stream during snowmelt was through near-surface soil macropores and overland flow. For those ions with concentrations higher in the snowpack than in the premelt streamwater, K+, NH4+, and H+, the earliest snowmelt pulses had the greatest influence on streamwater chemistry. Unlike other portions of the region with resistant bedrock, the widespread presence of alkaline glacial till provides excess stream acid neutralization capacity (ANC) to buffer acidic inputs. Peak winter streamwater ANC reduction was caused principally by spring melt dilution of base cations and associated alkalinity, constant high SO42− levels, and an increase in NO3−. The maximum reduction in stream ANC was concurrent with overland flow. Relative to its snowmelt concentration, NO3− was highest in streamwater with some stream input likely the result of nitrification and N mineralization.

APA, Harvard, Vancouver, ISO, and other styles

41

MacIsaac, Gwen, Aiysha Al-Wardian, Karen Glenn, and Rama M. Palepu. "Effects of di-, tri-, and tetraethylene glycols on the thermodynamic and micellar properties of Triton X-100 in water." Canadian Journal of Chemistry 82, no. 12 (2004): 1774–80. http://dx.doi.org/10.1139/v04-157.

Full text

Abstract:

Micellar and surface thermodynamic properties of aggregation of Triton X-100 (TX-100) in mixed solvent systems containing di-, tri-, and tetraethylene glycol with water have been investigated by employing surface tension, density, and fluorescence methods. The differences in Gibbs energies of micellization between water and binary solvent mixtures were determined to evaluate the influence of the co-solvent on the micellization process. From the surface tension measurements, the effects of the co-solvent on parameters such as surface excess, minimum area per molecule, and surface pressure indicate that the surface activity of the surfactant decreases with increasing concentration of the glycol co-solvent. Partial specific volumes, obtained from density measurements, indicate that the fraction of solvent molecules interacting with the micelles by hydrogen bonding vary with the type of additive. Fluorescence studies reveal that quenching of the pyrene probe by cetyl pyridinum chloride in TX-100 micelles is accompanied by simultaneous static and dynamic processes.Key words: Triton X-100, glycols, thermodynamics, micelles, fluorescence quenching.

APA, Harvard, Vancouver, ISO, and other styles

42

Neunert, Grażyna, Robert Hertmanowski, Stanislaw Witkowski, and Krzysztof Polewski. "Effect of Ester Moiety on Structural Properties of Binary Mixed Monolayers of Alpha-Tocopherol Derivatives with DPPC." Molecules 27, no. 15 (2022): 4670. http://dx.doi.org/10.3390/molecules27154670.

Full text

Abstract:

Phospholipid membranes are ubiquitous components of cells involved in physiological processes; thus, knowledge regarding their interactions with other molecules, including tocopherol ester derivatives, is of great importance. The surface pressure–area isotherms of pure α-tocopherol (Toc) and its derivatives (oxalate (OT), malonate (MT), succinate (ST), and carbo analog (CT)) were studied in Langmuir monolayers in order to evaluate phase formation, compressibility, packing, and ordering. The isotherms and compressibility results indicate that, under pressure, the ester derivatives and CT are able to form two-dimensional liquid-condensed (LC) ordered structures with collapse pressures ranging from 27 mN/m for CT to 44 mN/m for OT. Next, the effect of length of ester moiety on the surface behavior of DPPC/Toc derivatives’ binary monolayers at air–water interface was investigated. The average molecular area, elastic modulus, compressibility, and miscibility were calculated as a function of molar fraction of derivatives. Increasing the presence of Toc derivatives in DPPC monolayer induces expansion of isotherms, increased monolayer elasticity, interrupted packing, and lowered ordering in monolayer, leading to its fluidization. Decreasing collapse pressure with increasing molar ratio of derivatives indicates on the miscibility of Toc esters in DPPC monolayer. The interactions between components were analyzed using additivity rule and thermodynamic calculations of excess and total Gibbs energy of mixing. Calculated excess area and Gibbs energy indicated repulsion between components, confirming their partial mixing. In summary, the mechanism of the observed phenomena is mainly connected with interactions of ionized carboxyl groups of ester moieties with DPPC headgroup moieties where formed conformations perturb alignment of acyl chains, resulting in increasing mean area per molecule, leading to disordering and fluidization of mixed monolayer.

APA, Harvard, Vancouver, ISO, and other styles

43

Kazakova, O. O. "Quantum-chemical investigation of interactions in supramolecular systems: cholesterol - bile acids - silica in aqueous solutions." Surface 13(28) (December 30, 2021): 39–46. http://dx.doi.org/10.15407/surface.2021.13.039.

Full text

Abstract:

Hypercholesterolemia significantly increases the risk of myocardial infarction associated with COVID-19. Along with pharmacological treatment, the possibility of the excretion of excess cholesterol from an organism by adsorption is also of great interest. The interaction of cholesterol with the surface of partially hydrophobized silica in aqueous solutions of bile acids was investigated by the PM7 method using the COSMO (COnductor-like Screening MOdel) solvation model. The distribution of electrostatic and hydrophobic potentials of molecules and complexes was calculated. The values of free Gibbs energy adsorption of bile acids on the surface of silica correlate with the distribution coefficients in the n-octanol-water system. The energy of interaction of cholesterol with bile acids affects its adsorption on silica. The stronger the bond of cholesterol with the molecules of bile acids, the less it is released from the primary micelles in solution and adsorbed on the surface.

APA, Harvard, Vancouver, ISO, and other styles

44

Soyer, Nagihan, Sema Salgın, and Uğur Salgın. "Thermodynamic and Structural Properties of Biomimetic Monolayers Containing Cholesterol and Magnetite Nanoparticles." Black Sea Journal of Engineering and Science 8, no. 3 (2025): 7–8. https://doi.org/10.34248/bsengineering.1651121.

Full text

Abstract:

The thermodynamic and structural properties of biomimetic monolayers composed of cholesterol, dipalmitoylphosphatidylcholine, and hydrophobic magnetite (Fe₃O₄) nanoparticles were investigated under varying cholesterol molar fractions and pH conditions (4.8 and 7.4). Langmuir monolayer experiments were performed to analyze surface pressure-area isotherms, excess molecular area, excess Gibbs free energy of mixing, and compressibility modulus to assess lipid monolayer phase behavior, molecular organization, and mechanical stability. The results confirm that cholesterol enhances monolayer condensation up to a cholesterol molar fraction of 0.50, particularly at pH 7.4, where stronger lipid-lipid interactions promote molecular ordering and increase monolayer rigidity. At cholesterol molar fractions of 0.75 and higher, steric hindrance and phase separation effects emerge, disrupting monolayer homogeneity. pH significantly influences monolayer stability, with pH 7.4 favoring lipid condensation, whereas pH 4.8 induces monolayer expansion and molecular disorder. Excess molecular area and Gibbs free energy of mixing analyses indicate the strongest cholesterol-lipid interactions at a cholesterol molar fraction of 0.25 for pH 4.8 and 0.50 for pH 7.4, confirming these compositions as the most thermodynamically stable. Compressibility modulus analysis demonstrates that cholesterol enhances monolayer rigidity, with pH 7.4 producing higher values. However, at high cholesterol molar fractions, compressibility modules slightly decrease, suggesting steric constraints and lateral phase separation. The incorporation of magnetite nanoparticles increases molecular area and slightly reduces monolayer rigidity at low cholesterol molar fractions due to steric disruptions, but at cholesterol molar fractions of 0.50 and higher, cholesterol stabilizes the monolayer, counteracting nanoparticle-induced perturbations. These findings provide insight into the thermodynamic and structural regulation of biomimetic lipid monolayers by cholesterol and magnetite nanoparticles, with implications for nanomedicine, membrane biophysics, and lipid-based nanostructures.

APA, Harvard, Vancouver, ISO, and other styles

45

Belashchenko, D. K. "Molecular Dynamic Modeling of Magnesium in the Scheme of the Embedded Atom Model." Журнал физической химии 97, no. 3 (2023): 412–25. http://dx.doi.org/10.31857/s004445372303007x.

Full text

Abstract:

Potentials of the embedded atom model (EAM) for solid and liquid magnesium are proposed. Properties of magnesium are studied by means of molecular dynamics (MD) at binodals of up to 1500 K, and under conditions of static and shock compression. The main characteristics of bcc and liquid magnesium (structure, density, energy, compressibility, speed of sound, and coefficients of self-diffusion) are calculated. The static compression isotherm at 298 K up to a pressure of 108 GPa and the Hugoniot adiabat up to a pressure of 80 GPa are calculated with allowance for electron contributions. Values of the excess energy of the surfaces of magnesium nanoclusters with 13 to 2869 particles are found, and the Gibbs–Helmholtz equation for the relationship between surface tension and surface energy is estimated.

APA, Harvard, Vancouver, ISO, and other styles

46

Krishnan, Anandi, Yi-Hsiu Liu, Paul Cha, David Allara, and Erwin A. Vogler. "Interfacial energetics of globular–blood protein adsorption to a hydrophobic interface from aqueous-buffer solution." Journal of The Royal Society Interface 3, no. 7 (2005): 283–301. http://dx.doi.org/10.1098/rsif.2005.0087.

Full text

Abstract:

Adsorption isotherms of nine globular proteins with molecular weight (MW) spanning 10–1000 kDa confirm that interfacial energetics of protein adsorption to a hydrophobic solid/aqueous-buffer (solid–liquid, SL) interface are not fundamentally different than adsorption to the water–air (liquid–vapour, LV) interface. Adsorption dynamics dampen to a steady-state (equilibrium) within a 1 h observation time and protein adsorption appears to be reversible, following expectations of Gibbs' adsorption isotherm. Adsorption isotherms constructed from concentration-dependent advancing contact angles θ a of buffered-protein solutions on methyl-terminated, self-assembled monolayer surfaces show that maximum advancing spreading pressure, , falls within a relatively narrow band characteristic of all proteins studied, mirroring results obtained at the LV surface. Furthermore, Π a isotherms exhibited a ‘Traube-rule-like’ progression in MW similar to the ordering observed at the LV surface wherein molar concentrations required to reach a specified spreading pressure Π a decreased with increasing MW. Finally, neither Gibbs' surface excess quantities [ Γ sl − Γ sv ] nor Γ lv varied significantly with protein MW. The ratio {[ Γ sl − Γ sv ]/ Γ lv }∼1, implying both that Γ sv ∼0 and chemical activity of protein at SL and LV surfaces was identical. These results are collectively interpreted to mean that water controls protein adsorption to hydrophobic surfaces and that the mechanism of protein adsorption can be understood from this perspective for a diverse set of proteins with very different composition.

APA, Harvard, Vancouver, ISO, and other styles

47

Szymanowski, Jan, Krystyna Prochaska, and Mariusz Bogacki. "The correlation of copper extraction rate with surface excess, as determined by the gibbs isotherm using spline functions." Journal of Colloid and Interface Science 117, no. 1 (1987): 293–95. http://dx.doi.org/10.1016/0021-9797(87)90194-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Mauck, Robert L., Clark T. Hung, and Gerard A. Ateshian. "Modeling of Neutral Solute Transport in a Dynamically Loaded Porous Permeable Gel: Implications for Articular Cartilage Biosynthesis and Tissue Engineering." Journal of Biomechanical Engineering 125, no. 5 (2003): 602–14. http://dx.doi.org/10.1115/1.1611512.

Full text

Abstract:

A primary mechanism of solute transport in articular cartilage is believed to occur through passive diffusion across the articular surface, but cyclical loading has been shown experimentally to enhance the transport of large solutes. The objective of this study is to examine the effect of dynamic loading within a theoretical context, and to investigate the circumstances under which convective transport induced by dynamic loading might supplement diffusive transport. The theory of incompressible mixtures was used to model the tissue (gel) as a mixture of a gel solid matrix (extracellular matrix/scaffold), and two fluid phases (interstitial fluid solvent and neutral solute), to solve the problem of solute transport through the lateral surface of a cylindrical sample loaded dynamically in unconfined compression with frictionless impermeable platens in a bathing solution containing an excess of solute. The resulting equations are governed by nondimensional parameters, the most significant of which are the ratio of the diffusive velocity of the interstitial fluid in the gel to the solute diffusivity in the gel Rg, the ratio of actual to ideal solute diffusive velocities inside the gel Rd, the ratio of loading frequency to the characteristic frequency of the gel f^, and the compressive strain amplitude ε0. Results show that when Rg>1,Rd<1, and f^>1, dynamic loading can significantly enhance solute transport into the gel, and that this effect is enhanced as ε0 increases. Based on representative material properties of cartilage and agarose gels, and diffusivities of various solutes in these gels, it is found that the ranges Rg>1,Rd<1 correspond to large solutes, whereas f^>1 is in the range of physiological loading frequencies. These theoretical predictions are thus in agreement with the limited experimental data available in the literature. The results of this study apply to any porous hydrated tissue or material, and it is therefore plausible to hypothesize that dynamic loading may serve to enhance solute transport in a variety of physiological processes.

APA, Harvard, Vancouver, ISO, and other styles

49

Pogorzelski, Stanislaw, Paulina Janowicz, Krzysztof Dorywalski, Katarzyna Boniewicz-Szmyt, and Pawel Rochowski. "Wettability, Adsorption and Adhesion in Polymer (PMMA)—Commercially Available Mouthrinse System." Materials 16, no. 17 (2023): 5753. http://dx.doi.org/10.3390/ma16175753.

Full text

Abstract:

The study concerns the evaluation of the physicochemical and thermo-adsorptive surface properties of six commercially available mouthrinses, particularly surface tension, surface activity, partitioning coefficient, critical micellar concentration, Gibbs excesses at interfaces, surface entropy, and enthalpy. The aim was to quantify their effect on the adhesion and wettability of a model poly(methyl methacrylate) (PMMA) polymer. The adsorptive and thermal surface characteristics were derived from surface tension (γLV) vs. concentration and temperature dependences. Polymer surface wettability was characterized by the contact angle hysteresis (CAH) formalism, using the measurable advancing ΘA and receding ΘR dynamic contact angles and γLV as the input data. Further, wettability parameters: Young static angle (Θ), film pressure (Π), surface free energy (γSV) with its dispersive and polar components, work of adhesion (WA), and adhesional tension (γLV cosΘA) were considered as interfacial interaction indicators. The mouthrinse effect demonstrated the parameter’s evolution in reference to the PMMA/pure water case: Θ, ΘA and ΘR↓, CAH↑, Π↓, WA↓, γSV↓, and γLVcosΘA↑. Furthermore, the variations of the surface excess ratio pointed to the formation of multilayered structures of surfactants composing the mouthrinse mixtures considered. The contact angle data allowed for the penetration coefficient and the Marangoni temperature gradient-driven liquid flow speed to be estimated.

APA, Harvard, Vancouver, ISO, and other styles

50

Bråten, Vilde, Daniel Tianhou Zhang, Morten Hammer, Ailo Aasen, Sondre Kvalvåg Schnell, and Øivind Wilhelmsen. "Equation of state for confined fluids." Journal of Chemical Physics 156, no. 24 (2022): 244504. http://dx.doi.org/10.1063/5.0096875.

Full text

Abstract:

Fluids confined in small volumes behave differently than fluids in bulk systems. For bulk systems, a compact summary of the system’s thermodynamic properties is provided by equations of state. However, there is currently a lack of successful methods to predict the thermodynamic properties of confined fluids by use of equations of state, since their thermodynamic state depends on additional parameters introduced by the enclosing surface. In this work, we present a consistent thermodynamic framework that represents an equation of state for pure, confined fluids. The total system is decomposed into a bulk phase in equilibrium with a surface phase. The equation of state is based on an existing, accurate description of the bulk fluid and uses Gibbs’ framework for surface excess properties to consistently incorporate contributions from the surface. We apply the equation of state to a Lennard-Jones spline fluid confined by a spherical surface with a Weeks–Chandler–Andersen wall-potential. The pressure and internal energy predicted from the equation of state are in good agreement with the properties obtained directly from molecular dynamics simulations. We find that when the location of the dividing surface is chosen appropriately, the properties of highly curved surfaces can be predicted from those of a planar surface. The choice of the dividing surface affects the magnitude of the surface excess properties and its curvature dependence, but the properties of the total system remain unchanged. The framework can predict the properties of confined systems with a wide range of geometries, sizes, interparticle interactions, and wall–particle interactions, and it is independent of ensemble. A targeted area of use is the prediction of thermodynamic properties in porous media, for which a possible application of the framework is elaborated.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Gibbs surface excess of solutes'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles