Adsorption Freundlich

An adsorbed film obeys a modified Amagat equation of state, t(t = qkT (see Eq. ni-107). Show that this corresponds to a Freundlich adsorption isotherm (Eq. XI-12) and comment on the situation. 

The dissolution of passive films, and hence the corrosion rate, is controlled by a chemical activation step. In contrast to the enhancement of the rate of dissolution by OH ions under film-free conditions, the rate of dissolution of the passive film is increased by increasing the ion concentration, and the rate of corrosion in film-forming conditions such as near-neutral solutions follows the empirical Freundlich adsorption isotherm ... 

The dissolution of passive films is, in the main, controlled by a chemical activation step in contrast to film-free conditions at. Many protective anodic films are oxides and hydroxides whose dissolution depends upon the hydrogen ion concentration, and the rate follows a Freundlich adsorption equation ... 

For many metals and alloys the determination of /p is complex, and its magnitude is governed by many factors such as surface finish, rate of formation, alloying constituents, and the presence of those anions, such as halides, that promote localised breakdown. In many instances the attack on passive films by halide ions shows a temperature and concentration dependence similar to the effect of hydrogen ions, i.e. the rate of film dissolution increases with concentration in accordance with a Freundlich adsorption relationship... 

Langmuir and Freundlich adsorption isotherms for toluene and MEK are shown in Figs. 2... 

The adsorption coefficients (K) were determined using the equation for the Freundlich adsorption isotherm ... 

K = Freundlich adsorption coefficient from TABLE IV. ds = bulk density of soil from TABLE I. 

Transport of the herbicides by vapor diffusion on moist soil was shown to be directly related to vapor pressure and inversely related to water solubility. Transport of the herbicides by leaching was shown to be inversely related to the Freundlich adsorption coefficient which in turn was directly related to the octanol/water partition coefficient and inversely related to water solubility (16). 

Figure 15.4(A) shows the effect of the R = Zn2+/Al3+ ratio, which determines the charge density of the LDH layer, on the Freundlich adsorption isotherms. K values are far higher than those measured for smectite or other inorganic matrices. The increase in Kf with the charge density (Kf= 215, 228, 325mg/g, respectively, for R = 4, 3 and 2) is supported by a mechanism of adsorption based on an anion exchange reaction. The desorption isotherms confirm that urease is chemically adsorbed by the LDH surface. The aggregation of the LDH platelets can affect noticeably their adsorption capacity for enzymes and the preparation of LDH adsorbant appears to be a determinant step for the immobilization efficiency. [ZnRAl]-urease hybrid LDH was also prepared by coprecipitation with R = 2, 3 and 4 and Q= urease/ZnRAl from 1 /3 up to 2.5. For Q < 1.0,100 % of the urease is retained by the LDH matrix whatever the R value while for higher Q values an increase in the enzyme/LDH weight ratio leads to a decrease in the percentage of the immobilized amount.

Figure 4.9. Stem-Volmer intensity quenching of (a) Ru(bpy)32+, (b) Ru(phen)32 and (c) Ru(Ph2phen)32+ on hydrophilic Cab-O-Sil silica disks. The solid lines are the best fits using a two-parameter Freundlich adsorption model. (Reprinted from Ref. 33 with permission. Copyright 1991, American Chemical Society.)...

Figure 10.9 shows the intensity versus [O2] quenching curve for three complexes in Cab-O-Sil disks. The solid lines are the best fits to a Freundlich adsorption model (see below). All quenching is dynamic with no static component. 

The Langmuir and BET models incorporate an assumption that the energy of adsorption is the same for all surface sites and not dependent on degree of coverage. Since in reality the energy of adsorption may vary because real surfaces are heterogeneous, the Freundlich adsorption model (see Chap. 2) [37] attempts to account for this ... 

The Sips [38] model (Eq. 10) can easily be extended to binary or multicomponent systems [34, 74]. The resulting expression for the multicomponent Langmuir-Freundlich adsorption model is ... 

These figures are in approximate agreement with values calculated -with the aid of the Freundlich adsorption isotherm (see p. 134) but no definite conclusions may be drawn from them since the actual area of liquid-liquid interface in all probability was variable being dependent on the amount of emulsifying agent present. More recently the quantity of various soaps required to form a stable emulsion of kerosene in water has been determined by Grifiin (J.A.C.8. XLV. 1648, 1923) for sodium oleate, potassium stearate and potassium palmitate and by der Meulen and Riemann ibid. XLVI. 876, 1924) for sodium ricinoleate. 

Freundlich adsorption isotherm constants for several compounds on several adsorbents/water systems at ambient temperature... 

Cremer and Fliigge have suggested for the derivation of the Ostwald-Freundlich adsorption isotherm (29) that the energy of desorption from a catalyst possessing many kinds of such surface centers is a linear function of the energy E. Thus... 

This is the well-known Freundlich adsorption-isotherm Both a and n are functions of temperature. 

Equation (135) is the well-known Freundlich adsorption isotherm. In a number of instances this isotherm accurately describes experimental data. The interpretation of the Freundlich adsorption isotherm as resulting from exponential nonuniformity of surface is due to Zel dovich 43). 

In the Freundlich adsorption isotherm, the amount adsorbed is proportional to a fractional power of the pressure of the adsorptive. For a particular system, the fractional power and the constant of proportionality are functions of temperature. In terms of coverage the isotherm assumes the form... 

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