Effects of Sodium and Calcium Ions on the Aggregation of Titanium Dioxide, at High pH, in Aqueous Dispersions
| Autor: | A. Pierre, P. Couchot, F. Mange, Alain Foissy |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Aqueous solution
Sodium Inorganic chemistry chemistry.chemical_element Calcium Alkali metal Surfaces Coatings and Films Electronic Optical and Magnetic Materials Biomaterials symbols.namesake Electrokinetic phenomena Colloid and Surface Chemistry Gibbs isotherm Adsorption chemistry symbols Surface charge |
| Zdroj: | Journal of Colloid and Interface Science. 159:58-67 |
| ISSN: | 0021-9797 |
| Popis: | This paper investigates how sodium and calcium ions affect the aggregation of TiO2 particles in aqueous solutions of high pH. Optical microscopy and sedimentation rate and rheological measurements are used to characterize the aggregation. The surface charge and calcium adsorption densities are measured as a function of the total calcium concentration. The aggregates' size is maximum at a negative electrokinetic potential (-35 to -40 mV) when the surface excess of calcium equals almost half the ionized surface sites' density. Similar results are obtained at three values of the solid-to-solution volume ratio, provided that the calcium content is expressed in terms of moles per gram of solid. We propose that this aggregation between strongly negative particles is due to an attractive potential created by an ion-ion correlation, a phenomenon expected in systems with a high surface charge and divalent counter ions. In the presence of sodium ions, at pH 11, the dispersion stability increases to above 10-1M. This phenomenon is attributed to the occurrence of hydration forces. |
| Databáze: | OpenAIRE |
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