Tempkin isotherm

Fig. 45. Coverage of surface by the adsorbed intermediate as a function of potential in the anodic dissolution of iron. Adsorption follows a Langmuir isotherm at low coverages (—) and a Tempkin isotherm at higher coverages. The data are as calculated by Tsuru et al. [129].

At higher coverages, Lorenz and co-workers [139, 140] postulated that adsorption would follow a Tempkin isotherm... 

The Tempkin isotherm describes the adsorbent-adsorbate interactions, which assumes that the adsorption heat decreases linearly rather than logarithmic as the coverage proceeds [7]. Besides, the derivation of this adsorption is characterized by a uniform distribution of binding energy, which can up to some maximum binding energy. The equation for this model is expressed as ... 

All the adsorption curves were analysed with respect to the most common adsorption isotherms used in chemisorption. The AT, thrombin and DlP-thrombin adsorptions seem to correspond respectively to a Tempkin isotherm (AT) or a Langmiur isotherm (thrombin). Then the equilibrium between the surface, the protein in solution and the adsorbed protein can be caracterised with an affinity constant. These values are reported in Table I. 

Antithrombin competes with albumin for the adsorption on the polymer sites but cannot be desorbed by addition of a polycationic compound. Moreover the theoretical isotherm which fits the experimental results is the Tempkin isotherm which means that the variation of heat of adsorption with coverage can be interpreted in terms of surface heterogeneity. These results suggest that AT may interact simultaneously with several polymer sites including or not the negatively charged functions. 

In order to understand the behavior of a PEMFC in the presence of CO, the electrochemistry of CO and hydrogen on the surface of platinum must be understood. This is because platinum or its alloys are invariably used and needed in low-temperature acid electrolyte fuel cells to facilitate the electrochemical reaction for the production of electric power. The electrochemistry of CO in an acidic environment has been studied extensively [95] and reviewed by Baschuk and Li [96]. CO oxidation and adsorption occurs on the (1 0 0) and (1 1 0) sites of platinum in an acid electrolyte. The adsorption of CO involves CO linearly bonded to platinum, and the adsorption isotherm is that of a Tempkin isotherm, which can be written as [97] ... 

Show that Brunauer-Love-Keenan isotherm can be reduced to Langmuir, Freundlich, and Tempkin isotherms under suitable limiting conditions. 

Several different mathematical relationships (referred to as isotherms) have been developed to describe the relationship of fractional surface coverage with respect to the adsorbing species. Work by Langmuir, Freundlich, Tempkin, and others have attempted to describe the above mentioned pressure differential to fractional surface coverage. The most widely used and accepted isotherm is the BET equation, named after its orignators, Brunauer, Emmett, and Teller, and is as follows 29... 

The three most important isotherms are those associated with the names of Langmuir, Freundlich and Tempkin. Each is based on a different theoretical model, the principal difference being the way the heat of adsorption varies with surface coverage. 

The adsorption of the intermediate [FeClOH ] again follows Langmuir (at low coverages) and Tempkin (at high coverages) isotherms. 

A still further isotherm (equation 22) is attributed to Tempkin and assumes a linear dependence of the adsorption energy on fractional coverage. 

Fe Oj, FejO, nanocomposites, oxidation polymerization, Langmuir adsorption isotherm, Freundlich adsorption isotherm, Dubinin-Radushkevich adsorption isotherm, Tempkin adsorption isotherm, pseudo-first-order kinetic. Pseudo-second-order kinetic, removal efficiency, adsorption capacity... 

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