engleski

Charging of water at inert surfaces

Isoelectric point of silver halides depends on pH due to charging of interfacial water layer. The isoelectric point of water at inert and hydrophobic surfaces lies at pH ≈ 3 so that water at surfaces is negatively charged in the pH region above 4. Consequently the electroneutrality point of silver halides pAgeln in aqueous environment, with respect to adsorption of silver and halide ions, does not correspond to the isoelectric point pAgiep measured at pH ≈ 6, as previously assumed. The effect of assumed value of pAgiep was examined. The equilibrium constants for adsorption of silver and halide ions on silver chloride and silver bromide were calculated for the range of assumed pAgiep values ranging from isoelectric points measured at pH = 6 to pH= 3. The values of pAgiep obtained at pH = 3 was taken as pAgeln and the corresponding equilibrium constants of interfacial reactions were obtained.

single crystal electrode; silver chloride; silver bromide; surface potential; electrical interfacial layer; equilibrium parameters; interfacial water layer

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