engleski

A macroscopic, water structure based model for describing charging phenomena at hydrophobic surfaces in electrolyte solutions

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 data used for the modelling of the different systems exhibit differencies in the magnitudes of the zeta potentials. 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.

water; surface reaction; hydrophobic surfaces; electrolyte solutions

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