Strong electrolyte, adsorption

Adsorption with strongly favorable isotherms and ion exchange between strong electrolytes can usually be carried out until most of the stoichiometric capacity of the sorbent has been utilized, corresponding to a thin MTZ. Consequently, the total capacity of the bed is... 

Idzikowski, S. (1973) Adsorption of inorganic ions on iron(III) oxide from mixtures of strong electrolytes. IV. Adsorption of silver, cupric and aluminium sulphate in presence of indifferent electrolyte. Rocz. Chem. 231-238... 

The papers in this volume deal with many of the foregoing questions and problems relating to adsorption from aqueous solution. In addition to general discussions of thermodynamic and kinetic aspects of adsorption phenomena, the papers include description of the results of studies on a variety of adsorbate-adsorbent systems. Among the adsorbates studied are (1) strong electrolytes (2) unhydrolyzed multi-valent cations ... 

Analysis of the Composite Isotherm for the Adsorption of a Strong Electrolyte from Its Aqueous Solution onto a Solid... 

Specific electrolyte adsorption can occur on oxides by ion exchange with structural cations, with hydrogen or hydroxyl of the surface hydroxide groups, or with impurities (92, 94). Ions which can form insoluble compounds or undissociated complexes with a component of the solid crystal lattice adsorb more strongly than those which cannot (2). This does not imply or require that such complexes or compounds do or do not form. The question may be left open. It does imply that, of a series of species which form insoluble compounds with components of the solid, that which forms the least-soluble compound will be adsorbed most strongly. Thus any generalization which can be used to predict solubility or complexing tendency can be extended to predict adsorba-bility, at least qualitatively. 

The potentials of the capacity minima are strongly dependent on the pH of the electrolyte. The current potential curves show the same dependence. These potential differences are not caused by changes in the space charge. It must be assumed that the source of these potential differences lies between the semiconductor surface and the Helmholtz plane in the electrolyte. Adsorption of OH ions may be an explanation of this effect. 

It frequently happens that hydrogen ions are removed from solution by impurities in the indicator or in the paper, or as a result of adsorption by the paper. In other words, the solution apparently is neutralized. The use of a buffer mixture, however, counteracts the influence of traces of impurities. The sensitivity of indicator papers is found to be the same as that of the corresponding indicator solutions when measured in the presence of buffer solutions. For strong electrolytes, the indicator papers measure the titration acidity rather than the hydrogen ion concentration. 

One of us has presented a statistical theory for strong electrolytes according to this point of view. The model of order-disorder is similar to that applied by Bethe in his theory of binary alloys. This model has been applied to adsorption phenomena of gases on surfaces, where it has explained the abnormal cases of isobaric adsorption, and it reproduces the isotherm of Langmuir. It has also been used for condensation phenomena, where we obtain from it the relations between physical quantities at the critical point. 

Figure 1. Effect of high concentrations of solutions of strong electrolytes on the adsorption of N-nitrosodiethylamine on lignins. Dependence of the number of Itmoles of the nitrosamine adsorbed on equilibrium concentration of free, unbound...

The method of mixed electrolytes first presented in two fundamental papers by Hurwitz [11] and Dutldewicz and Parsons [12] was an important contribution to the methods of evaluation of specific adsorption. In Ref. [11], Gibbs s adsorption equation has been derived in a general form for the case of mixed solutions of strong electrolytes at constant molal ionic strength. 

It can be generalized that the role of modifiers in the electron transfer process between the electrodes and redox proteins consists mainly in their capability to form a suitable electrode/electrolyte solution interface. At this interface only such surface configurations of the proteins are possible which prevent their strong electrostatic adsorption resulting in more extensive denaturation changes of the protein molecule [207,210,212]. 

The effects of carbon oxidation and reduction on adsorption of strong electrolytes have been studied with NaCl and NaBr (Jankowska, 1991). Their results are summarized in Table 5.7. The strong acidic groups introduced by oxidation undergo cation exchange with the sodium ion, hence acidifies the solution. The acidified solution significantly increases the potential that favors the adsorption of anions. This explains the simultaneous increases in the adsorption of both anions and the cation. 

Fig. 5.8 - Schematic models of the ion, potential (0) and charge (a) distribution across the metal-electrolyte interface for (a) non-specific adsorption, (b) weak specific adsorption and (c) strong specific adsorption. 0, 0j, 02 0 re the...

---