On the nature of the energetic surface heterogeneity in ion adsorption at a water/oxide interface: theoretical studies of some special features of ion adsorption at low ion concentrations

Abstract

At low surface concentrations the log-log plots of the experimental adsorption isotherms of ions on oxides show a transition from a linear (Henry's) plot with a tangent equal unity to a Freundlich plot with tangent smaller than unity. A theory has been developed reproducing that striking behavior of these adsorption isotherms. That theoretical treatment was based on a picture of a heterogeneous solid surface, with different adsorption sites-the outermost surface oxygens. Our theoretical study indicates that the binding-to-surface energies of different surface complexes, formed on different surface oxygens, vary in an independent way from one surface oxygen to another.

A Single-Site Model for Divalent Transition and Heavy Metal Adsorption over a Range of Metal Concentrations

“…Many investigators (e.g., 2,15,19,21,[24][25][26][27][28][29][30][31] have proposed that metal adsorption isotherms with slopes of <1 are a result of adsorption to more than one site type. Metal adsorption with increasing metal concentration occurs progressively onto two or more different types of surface sites.…”

Effects of surface heterogeneity of oxides in simple ion adsorption at oxide/electrolyte interfaces

“…Assuming the finite integration limits for the two different models of random surface we obtained (Rudzifiski et al, 1993) two different sets of equations for Oit, corresponding to two different correlation models. These sets were used to calculate the surface coverage by bivalent metal ions which are found at a small ion concentration.…”

“…This deserves some further experimental and theoretical studies. Rudzifiski et al (1993) developed the theory reproducing the behaviour of the log-log plots of the experimental adsorption isotherms of bivalent ions on oxides at low surface concentrations. These experimental adsorption isotherms show a transition from a linear loglog (Henry's) plot with a tangent equal to unity to a Freundlich log-log plot with tangent smaller than unity.…”

Calorimetric Effects and Temperature Dependence of Simple Ion Adsorption at Oxide/Electrolyte Interfaces: The Systems in Which PZC and CIP Do Not Coincide

“…Such theoretical analysis has been presented in the series of our recent publications (2)(3)(4)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42). It was based on the most popular triple-layer mechanistic model of oxide/electrolyte interfaces, and on the most commonly accepted 2-pK charging mechanism.…”