The Effects of Ethanol Concentration and of Ionic Strength on the Zeta Potential of Titania in the Presence of Sodium Octadecyl Sulfate
Abstract
:1. Introduction
- With very low ionic strengths (10−4 M or less), the available pH range is limited. For example, with the ionic strength of 10−4 M, a pH below 4 is not available, because at pH < 4 the acid added to adjust the pH produces an ionic strength higher than 10−4 M. In other words, a very low ionic strength is difficult to adjust and control.
- With very high ionic strengths (10−1 M or more) the dispersions are unstable against coagulation, especially near the IEP, while electrophoretic measurements require a relatively stable dispersion. Moreover, the zeta potentials at high ionic strengths are low in absolute value, and the signal-to-noise ratio is poor. This problem can be solved by using the electroacoustic technique [20] instead of electrophoresis, but this is a separate topic unrelated to the present work.
2. Materials and Methods
3. Results and Discussion
- IEP at pH 6.5 in the absence of surfactant and at very low surfactant concentrations, which is consistent with IEP of P25 and of other titanias reported in the literature [21].
- Substantial shift in the IEP at 5.4 × 10−6 M sodium octadecyl sulfate, but still positive zeta potentials in the acidic range.
- Negative zeta potentials over the entire pH-range at 1.1 × 10−5 M sodium octadecyl sulfate, but the zeta potentials are more negative (about −50 mV) at pH > 7, and less negative (about −20 mV) at pH < 4.
- Negative and pH-independent zeta potentials of about −50 mV over the entire pH-range at 2.1 × 10−5 M sodium octadecyl sulfate.
Author Contributions
Funding
Conflicts of Interest
References
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Kosmulski, M.; Mączka, E. The Effects of Ethanol Concentration and of Ionic Strength on the Zeta Potential of Titania in the Presence of Sodium Octadecyl Sulfate. Colloids Interfaces 2020, 4, 49. https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4040049
Kosmulski M, Mączka E. The Effects of Ethanol Concentration and of Ionic Strength on the Zeta Potential of Titania in the Presence of Sodium Octadecyl Sulfate. Colloids and Interfaces. 2020; 4(4):49. https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4040049
Chicago/Turabian StyleKosmulski, Marek, and Edward Mączka. 2020. "The Effects of Ethanol Concentration and of Ionic Strength on the Zeta Potential of Titania in the Presence of Sodium Octadecyl Sulfate" Colloids and Interfaces 4, no. 4: 49. https://0-doi-org.brum.beds.ac.uk/10.3390/colloids4040049