Anderson22 applied the Langmuir-type isotherm to adsorption of arsenate ion on amorphous aluminum hydroxide at the isoelectric point, by considering the total concentration of the adsorbate, yet this analysis was designated as strictly empirical.3 The present work shows that there is justification in using such an isotherm in the treatment of adsorption data as long as the adsorption (22) Anderson, .

A simple general model framework for the charge development at hydrophobic surfaces in aqueous electrolyte solutions is proposed. It is based on the idea of enhanced autolysis of interfacial water triggered by a structured layer of water. The model is applied to experimental data for air, oil, diamond and Teflon aqueous interfaces and to the ice-water interface. The structure of the interfaces, as derived from sum frequency spectroscopy and molecular dynamics simulations, is used as a conceptual basis. The proposed model describes zeta potential data and supplementary macroscopic data well. The experimental zeta potentials used for the modelling of the different systems exhibit differences in magnitude. Streaming current measurements yield higher zeta potentials than conventional electrophoretic mobility measurements. This discrepancy in the data is reconciled in the resulting model parameters, such as the slip plane distance, s, an empirical parameter that allows the quantitative description of reported zeta potentials. Overall, the model parameters are consistent with similar work on other types of surfaces. Differences between the various surfaces studied in the present work can be explained by the difference in their properties, the different experimental techniques used and/or the diversity in data for nominally identical systems.

Abstract. This article summarizes methods for determining proton surface charge at mineral/water interfaces. It covers conventional experimental procedures and discusses problems with the techniques. Also it involves recommendations for obtaining reasonable and comparable results. The term "comparable results" refers to comparison between results for the same solid as obtained in different laboratories. The most important parameters for the surface titrations are discussed. We also propose a reference titration procedure that would allow direct, unbiased comparisons of experimental data. The article finally includes a check-list for researchers and reviewers which should allow limiting the amount of titration data that are not useful for future uses. (doi: 10.5562/cca2062)

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