Adsorption standard free energy

From the adsorption standard free energies and standard enthalpies, adsorption entropies can be calculated from ... 

Standard Free Energies of Adsorption of B and BH. The standard free energy of adsorption of C12BMG was calculated from the surface tension data in Figures 1 and 2 by use of the equation ... 

AG°s is the standard free energy of adsorption of the solute to the stationary phase surface ([) is the column phase ratio... 

The data in Table 1 shows that the standard free energy of adsorption increases, on average, by 2.5 kj/mol for each methylene group added to the hydrophobic tail. However, the intermolecular interaction parameter p in... 

Fig. P6.2. Temperature dependence of the standard free energy of adsorption for (a) CF3SO3 and (b) H3P04 (E = 0.80 V). (Reprinted from P. Zelenay, B. R. Scharifker, J. O M. Bockris, and D. Gervasio, J. Electrochem. Soc. 133 2262, copyright 1986, Fig. 4, with permission of Elsevier Science.)...

Figure P6.4 shows the logarithmic dependence of the adsorption of chloride ions, log(T - r/r, on time, /(min). The adsorbing metal is aluminum, the concentration of chloride ions in solution is 1(T3 mol dm-3 at pH 12, and the potential in the hydrogen scale is -0.9 V. On the assumption that the adsorption is diffusion controlled, determine the standard free energy of adsorption of chloride ions on the surface concerned. 

For anionic monolayers, the reversal of the tt-A isotherms can be explained in terms of a competition between the anionic head groups and the alkali metal cations for molecules of water. If a modified Stern-type model of the plane interface is assumed, this interface will be composed of distinct adsorption sites, with counterions (cations) of finite size that can adsorb on these sites if the standard free energies of adsorption are favorable. If the anionic head group is more polarizable than water, as with carboxylic acids or phosphates, the hydration shell of the cation is incompletely filled, and the order of cation sizes near the interface is K+ > Na+ > Li+. When the polarizability of the anionic group is less than that of water, as with the sulfates, the lithium cation becomes the most hydrated one, and the order of cation sizes becomes Li+ > Na+ > K+. 

In these cases, the standard free energy of adsorption can be obtained from the equilibrium condition and is a simple exponential function of the potential which does not depend significantly on the charge distribution at the interface for an uncharged adsorbate. The chemisorption thus corresponds to a vertical shift in the free energy curves as depicted in Fig. 12 and affects the energy of activation [76]. 

From the slope and intercept of these plots the saturation coverage and adsorption coefficient were obtained by application of the previously given equation. The results are listed in Table I, which also includes the area per dye molecule at saturation coverage and the standard free energy of adsorption, AG°. Although the latter parameter was calculated as before (23), its thermodynamic validity is questionable since reversibility of adsorption of these dyes was not demonstrated. The molecular... 

Each monomer is ascribed with a two-dimensional coordinate, of which the abscissa dimension corresponds to the affinity to the polar (water) or the nonpolar phase (hexane) and the ordinate dimension corresponds to interfacial activity. The standard free energy of partition between water and hexane is used as a quantitative parameter for the abscissa axis (AFpart), whereas the standard energy of adsorption at the interface is used for the ordinate axis (AFa(js). Both parameters are normalized by the kT factor. The normalized values are denoted as A/part and A/ads, respectively. Thus,... 

The standard free energy of adsorption from either bulk phase was calculated from interfacial tension isotherms ... 

Recent studies showed that amphiphilic properties have to be taken into account for most water-soluble monomer units when their behavior in water solutions is considered. The amphiphilic properties of monomer units lead to an anisotropic shape of the polymer structures formed under appropriate conditions, which is confirmed both by computer simulation and experimental investigations. The concept of amphiphilicity applied to the monomer units leads to a new classification based on the interfacial and partitioning properties of the monomers. The classification in question opens a broad prospective for predicting properties of polymer systems with developed interfaces (i.e., micelles, polymer globules, fine dispersions of polymer aggregates). The relation between the standard free energy of adsorption and partition makes it possible to estimate semiquantitatively the distribution between the bulk and the interface of monomers and monomer units in complex polymer systems. 

Fig. 4.5 Standard free energy of adsorption as a function of temperature for (a) IC and (b) PEO in aqueous solution. (From ref. [28])...

Fig. 12.45. The standard free energy of adsorption of families of organics as a function of the standard free energy of solution. Note the difference in sign. Adsorption occurs more readily as the tendency to dissolve declines. (Reprinted with permission from E. Blomgren, J. O M Bockris, and K. Jesch, J. Phys. Chem. 65 2006, copyright 1961 American Chemical Society.)...

An additional characteristic, common to all purine analogues, and ascribed to the presence of the imidazole ring is the strong adsorption of adenine and its nucleosides and nucleotides at the electrode surface35 37 53, 153), with a standard free energy for adsorption of 29-38 kJ/M 37,53). 

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