Calorimetric Effects of Simple Ion Adsorption at the Silica/Electrolyte Interface:  Quantitative Analysis of Surface Energetic Heterogeneity

Abstract

The equations developed by us for the triple layer surface complexation approach, taking into account energetic heterogeneity of surface oxygens, are applied here to study the heterogeneity influences on the enthalpic effects accompanying ion adsorption at the silica/NaCl aqueous solution interface. That study is accompanied by the parallel experimental/theoretical study of the energetic heterogeneity of surface oxygens for adsorption of argon molecules which are known to interact practically only with surface oxygens. Such studies provide a simpler interpretation for information of the surface energetic heterogeneity. That additional study confirms a proper choice of the model of surface heterogeneity, accepted by us in our description of ion adsorption at the oxide/electrolyte interfaces. Our quantitative analysis also confirms quite different features of the silica/electrolyte interface, compared to those formed by other metal oxides. Namely, in the case of the silica/electrolyte interface, the adsorption of water molecules on the surface oxygens SO- is a process highly competitive with proton adsorption leading to that of formation of the neutral surface complexes SOH0.

Aqueous silane-surfactant co-dispersions for deposition of hydrophobic coatings onto pre-oxidized polysilicon

“…11). The point of zero zeta potential or iso-electric point (IEP) was found to occur at a pH of approximately 2.5; this is in agreement with values reported in literature for silicon oxides on single crystal silicon [44,45].…”

Electrokinetic flow-induced currents in silica nanofluidic channels

“…The experimental data for other systems, for example, the silica and NaCl interface, showed inconsistency in the distribution of the surface charge or zeta potential, although the same colloidal silica [46,50] or pyrogenic silica [51][52][53] was used (data are not shown here). Figs.…”

Energetics of arsenate sorption on amorphous aluminum hydroxides studied using flow adsorption calorimetry

“…Flow adsorption calorimetry will not only give a direct measure of the heat effects but will also identify and quantify changes that occur in the properties of the surface under study as a result of a specific treatment. Flow calorimetry has been used to study the surface chemistry of many solids [19][20][21] as well as heats of ion adsorption at the oxide/electrolyte interfaces [22] and K/Ca and K/Pb exchange in tropical soils [23]. Yet to our knowledge no use of it has been made to the study of arsenate sorption on amorphous aluminum hydroxides (AHO).…”