Energy of adsorption from

But why determine the free energies of adsorption from experiment Instead, one can attempt to calculate the values from a knowledge of the particles, the forces between them, and the effect on the particles of the electric field operating on the electrified interface. 

Taylor and Strother found that the activation energy of Type A adsorption from 0 to 56°C varied, with increasing surface coverage, from 3 to 6 Kcal./mole. The activation energy of adsorption from 184° to 218°C, with the same surface coverage, varied from 10 to 11 Kcal./mole. The latter may be qualitatively compared to the activation energy for Type B adsorption of 0.8 e.v. or 18 Kcal./mole. Two sources of error may be mentioned here (1) the observed Type B adsorption may have... 

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

Knigliakov (95-97) proposed a concept called hydrophilc-lipophile ratio (HLR). which is the ratio of the energy of adsorption of the surfactant molecule from the water phase ro its energy of adsorption from the oil phase. The HLR is a good altemative, but it suffers from the. same drawback that Winsor R ratio... 

Note The reactions of chemical and electrochemical combination (Equations 2.3, 2.6, and 2.7) lead to H2 dissolved in water, so the rate equations for the reverse adsorption reactions involve the free energy of adsorption from H2(aq) and the activity of H2(aq), [Pg.127]

The adsorption of nonelectrolytes at the solid-solution interface may be viewed in terms of two somewhat different physical pictures. In the first, the adsorption is confined to a monolayer next to the surface, with the implication that succeeding layers are virtually normal bulk solution. The picture is similar to that for the chemisorption of gases (see Chapter XVIII) and arises under the assumption that solute-solid interactions decay very rapidly with distance. Unlike the chemisorption of gases, however, the heat of adsorption from solution is usually small it is more comparable with heats of solution than with chemical bond energies. 

Chemisorption may be rapid or slow and may occur above or below the critical temperature of the adsorbate. It is distinguishable, qualitatively, from physical adsorption in that chemical specihcity is higher and that the energy of adsorption is large enough to suggest that full chemical bonding has occurred. Gas that is chemisorbed may be difficult to remove, and desorption may be... 

The case of a vapor adsorbing on its own liquid surface should certainly correspond to mobile adsorption. Here, 6 is unity and P = the vapor pressure. The energy of adsorption is now that of condensation Qu, and it will be convenient to define the Langmuir constant for this case as thus, from Eq. xvn-39. 

Fig. XVII-23. (a) Entropy enthalpy, and free energy of adsorption relative to the liquid state of N2 on Graphon at 78.3 K (From Ref. 89.) b) Differential entropies of adsorption of n-hexane on (1) 1700°C heat-treated Spheron 6, (2) 2800°C heat-treated, (3) 3000°C heat-treated, and (4) Sterling MT-1, 3100°C heat-treated. (From Ref 18.)...

Fig. XVIII-13. Activation energies of adsorption and desorption and heat of chemisorption for nitrogen on a single promoted, intensively reduced iron catalyst Q is calculated from Q = Edes - ads- (From Ref. 130.)...

In Section 1.3 it was noted that the energy of adsorption even for a perfect crystal differs from one face to another. An actual specimen of solid will tend to be microcrystalline, and the proportion of the various faces exposed will depend not only on the lattice itself but also on the crystal habit this may well vary amongst the crystallites, since it is highly sensitive to the conditions prevailing during the preparation of the specimen. Thus the overall behaviour of the solid as an adsorbent will be determined not only by its chemical nature but also by the way in which it was prepared. 

The rate of evaporation of ions from a heated surface is given by Equation 7.3, in which Q, is the energy of adsorption of ions on the filament surface (usually about 2-3 eV) and Cj is the surface density of ions on the surface (a complete monolayer of ions on a filament surface would have a surface density of about 10 ions/cm" ). 

Equation 9 states that the surface excess of solute, F, is proportional to the concentration of solute, C, multipHed by the rate of change of surface tension, with respect to solute concentration, d /dC. The concentration of a surfactant ia a G—L iaterface can be calculated from the linear segment of a plot of surface tension versus concentration and similarly for the concentration ia an L—L iaterface from a plot of iaterfacial teasioa. la typical appHcatioas, the approximate form of the Gibbs equatioa was employed to calculate the area occupied by a series of sulfosucciaic ester molecules at the air—water iaterface (8) and the energies of adsorption at the air-water iaterface for a series of commercial aonionic surfactants (9). 

A theoretical description of hydrogen bonding effects can be made from model of charge-controlled adsorption. It was found that the energy of adsorption of organic molecules ai e determined by the ratios between the effective chai ges of their atoms and atoms in polai solvent molecules ... 

FIG. 9 Solvent contribution to the free energy of adsorption of I on Pt(lOO) at different temperatures as indicated. (From Ref. 164.)... 

In the absence of specific interactions of the receptor - ligand type the change in the Helmholtz free energy (AFadj due to the process of adsorption is AFads = yps - ypi - Ysi, where Yps, YPi and ys, are the protein-solid, protein-liquid and solid-liquid interfacial tensions, respectively [5], It is apparent from this equation that the free energy of adsorption of a protein onto a surface should depend not only of the surface tension of the adhering protein molecules and the substrate material but also on the surface tension of the suspending liquid. Two different situations are possible. 

Figure 26. Plot of the Gibbs energy of adsorption of organic substances at a = 0 vs. the interfacial parameter, AX. (1) 1-Hexanol, (2) 1-pentanol, and (3) acetonitrile. From Ref. 32, updated. Additional points (1) Au(l 11),910 Bi(l 11),152 and (2) Ga916...

Figure 27. Gibbs energy of adsorption of water from the bulk of the solution on the given metals as calculated by Afanasyev and Akulova.909 The figures on top of the bars are the values of the interfacial parameter, AX.

Figure 28. Dependence of the Gibbs energy of adsorption of diols on the number of carbon atoms in the molecule. Data for Hg from Ref. 912 data for Au from Ref. 911.

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