Визначення ізоелектричної точки поверхнево-модифікованих оксидів металів у водних середовищах
The position of the isoelectric point of aqueous suspensions of metal oxides/hydroxides depends on many factors, in particular, on the parameters of the crystal lattice, its defects, and the presence of impurities. Since the isoelectric point is an integral characteristic of the electrosurface prope...
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| Datum: | 2025 |
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| Hauptverfasser: | , , |
| Format: | Artikel |
| Sprache: | Ukrainisch |
| Veröffentlicht: |
Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine
2025
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| Online Zugang: | https://www.cpts.com.ua/index.php/cpts/article/view/773 |
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| Назва журналу: | Chemistry, Physics and Technology of Surface |
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Chemistry, Physics and Technology of Surface| Zusammenfassung: | The position of the isoelectric point of aqueous suspensions of metal oxides/hydroxides depends on many factors, in particular, on the parameters of the crystal lattice, its defects, and the presence of impurities. Since the isoelectric point is an integral characteristic of the electrosurface properties of charged surfaces of amphoteric oxides in their aqueous suspensions, studies aimed at its determination are relevant.A new approach to the determination of the isoelectric point for surface-modified metal oxides, in which ionized surface hydroxyl groups in aqueous medium appear not only as a result of their ionization reactions involving pH-determining Н+ and ОН– ions, but also other reactions, has been proposed. The essence of this approach is to determine experimentally the dependence of the difference in pH of suspensions and the pH of the aqueous solutions on which these suspensions are based on the pH of the initial aqueous solutions. Based on this dependence, four variable parameters characterizing it are estimated by the least squares method, namely: two ionization constants of surface hydroxyl groups, the total concentration of surface hydroxyl groups, and the difference in the fraction of ionized surface hydroxyl groups that are not related to the pH-determining ions Н+ and ОН–.Based on the results obtained, an equation has been developed that allows to estimate the position of the isoelectric point for surface-modified metal oxides in their aqueous suspensions using the found variable parameters. In the case when the presence of ionized surface hydroxyl groups is associated only with pH-determining Н+ and ОН– ions, the proposed equation is simplified to the classical equation.The application of the obtained equation is illustrated by the example of determining the isoelectric point of aqueous suspensions of modified titanium dioxide. |
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