Thermodynamically Consistent Equilibrium Adsorption Isotherms for Mixtures of Different-Sized Molecules

Franses, Elias I.; Siddiqui, Faisal A.; Ahn, Dong June; Chang, Chien Hsiang; Wang, Nien Hwa Linda

doi:10.1021/la00008a050

Cited by 53 publications

(47 citation statements)

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“…This equation is valid when there is no area change upon mixing, and it is consistent with the ideal adsorbed solution adsorption. For molecules that differ greatly in size, the ideal mixing conditions may be not fulfilled (24,25). LeVan and Vermeulen (26) derived a set of thermodynamically consistent equations of which Equation 4 is a particular case.…”

Section: Resultsmentioning

confidence: 99%

Surface tension of bovine serum albumin and tween 20 at the air‐aqueous interface

Niño

Patino

1998

J Americ Oil Chem Soc

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Interfacial properties (surface tension, σ, and critical micelle concentration, CMC) of aqueous solutions of Tween 20 (polyoxyethylene sorbitan monolaurate) and/or bovine serum albumin (BSA) were evaluated. Temperature, Tween 20 concentration in the aqueous phase, BSA/Tween 20 ratio, and aqueous phase composition [water, ethanol (0.5, 1.0, and 2.5 M), and sucrose (0.5 M)] were the variables studied. The CMC of Tween 20 was determined by surface tension measurements (Wilhelmy plate method). The existence of BSA-Tween 20 interactions was deduced from surface tension measurements. The results show that the effect of temperature on CMC depends on the aqueous phase composition, but the σ value at CMC, σ CMC , does decrease as temperature is increased. The CMC and σ CMC values also depend on the aqueous phase composition. In aqueous ethanol solutions, the CMC increases, but σ CMC decreases. However, in sucrose aqueous solutions, the CMC decreases, but there is no significant effect on σ CMC . The BSA-Tween 20 interactions at the interface depend on both Tween 20 concentration (C ) and solute in the bulk phase. In water and aqueous solutions of ethanol and sucrose, σ values decrease in the presence of protein at C < CMC but are practically independent of C at C > CMC. This is an indication that the interfacial characteristics of the mixed film are determined by either the protein or the lipid at the higher and lower protein/lipid ratio, respectively. In the intermediate region, the existence of BSA-Tween 20 interactions dominates the interfacial characteristics of mixed films.The formation of stable colloidal dispersions (emulsions, foams, etc.) is extremely important in the paint, petroleum, cosmetic, pharmaceutical, and food industries (1-3). Significant economic waste arises from the manufacture of unstable foams and emulsions. The chemical and physical properties of surface-active molecules are of great interest because they determine the colloidal stability of dispersed particles (4). Proteins stabilize foams and emulsions by forming a mechanical barrier at the interface that encapsulates the dispersed phase and resists random surface perturbations, droplet coalescence, or flocculation (5). The barrier is formed as intermolecular interactions between the adsorbed protein molecules are established. These contribute significantly to the rheological properties of the barrier and immobilize proteins in the adsorbed layer. In contrast, lipids stabilize the dispersed droplet or bubble by formation of a densely packed monomolecular layer, which is stabilized by Gibbs-Marangoni mechanisms (6). However, the presence of proteins and lipids in the same systems can result in instability as both types of surface-active molecules compete to form different types of adsorbed layers (immobile vs. mobile) (7). The distribution of proteins and lipids in food emulsions and foams is determined by competitive and cooperative adsorption between the two types of emulsifiers at the fluid-fluid interfaces, and by the nature of protein-lipi...

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Section: Resultsmentioning

confidence: 99%

Surface tension of bovine serum albumin and tween 20 at the air‐aqueous interface

Niño

Patino

1998

J Americ Oil Chem Soc

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“…(18) and (19) only apply to binary systems consisting of solvent and one adsorptive compound. For multi-component systems containing more than one adsorptive compound, the following generalization of Eq.…”

Section: Ellipsometrymentioning

confidence: 99%

“…A common approach used for the description of multicomponent monolayers is the direct integration of the Gibbs equation using model adsorption isotherms. Although model isotherms may be chosen at will, it should be noted however that, in order to ensure thermodynamic consistency of the model, the partial adsorption isotherms, C i and C j , of the components i and j must satisfy the following constraint [18,19].…”

Section: Introductionmentioning

confidence: 99%

Interfacial dynamics and structure of surfactant layers

Zhmud¹,

Tiberg

2005

Advances in Colloid and Interface Science

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“…We note that the proposed model automatically satisfies the thermodynamic consistency relation [14,15] oqQcd "~ ( OQzn O Uz.) Ccd = t, i-ffU ) Oz.'…”

Section: Construction Of Adsorption Isotherms From Batch Experimentsmentioning

confidence: 76%

Quantitative description of multi-component reactive transport in porous media: An empirical approach

et al. 1996

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We propose a general method for the description of multi-component reactive transport in porous media. The approach is based on the local equilibrium assumption and consists of four steps: (i) measurement of the adsorbed amounts of all components of interest by means of laboratory batch experiments, (ii) construction of a simple, empirical binding model consistent with the experimental data by means of constrained, regularized least-squares, (iii) calculations of multi-component breakthrough curves based on numerical solutions of the transport equations coupled to the empirical binding model, (iv) verification of these model predictions with laboratory column experiments. We demonstrate the applicability of the procedure by investigating simultaneous transport of cadmium and zinc at constant pH in a silica sand column.

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Thermodynamically Consistent Equilibrium Adsorption Isotherms for Mixtures of Different-Sized Molecules

Cited by 53 publications

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Surface tension of bovine serum albumin and tween 20 at the air‐aqueous interface

Surface tension of bovine serum albumin and tween 20 at the air‐aqueous interface

Interfacial dynamics and structure of surfactant layers

Quantitative description of multi-component reactive transport in porous media: An empirical approach

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