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Playing Favorites: Preferential Adsorption of Nonionic over Anionic Surfactants at the Liquid/Liquid Interface
Rebecca M Altman1, Evan L Christoffersen1, Konnor K Jones1
1Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 5, 2021
Summary
In mixed surfactant systems, nonionic Span-80 preferentially adsorbs to the oil/water interface over anionic AOT, which desorbs over time. This competitive adsorption impacts applications relying on surface properties.
Area of Science:
- Surface Chemistry
- Colloid and Interface Science
Background:
- Understanding competitive adsorption in binary surfactant systems is crucial for optimizing applications dependent on interfacial properties.
- Mixed surfactant systems are widely used in pharmaceuticals, industrial films, and environmental remediation.
Purpose of the Study:
- To investigate the surface behavior and competitive adsorption of a binary surfactant mixture containing nonionic Span-80 and anionic AOT at the oil/water interface.
Main Methods:
- Vibrational sum-frequency (VSF) spectroscopy was employed to study the interfacial behavior.
- Surface tensiometry was used to measure surface tension changes.
- Time-dependent and concentration-dependent studies were conducted to analyze adsorption dynamics.
Main Results:
- Both nonionic (Span-80) and anionic (AOT) surfactants initially adsorb to the oil/water interface.
- Anionic surfactants (AOT) were observed to desorb over time, while nonionic surfactants (Span-80) continued to adsorb.
- Concentration studies demonstrated preferential adsorption of Span-80 over AOT at the oil/water interface.
Conclusions:
- Nonionic Span-80 exhibits preferential adsorption over anionic AOT at the oil/water interface in binary mixtures.
- The competitive adsorption dynamics have significant implications for the design and efficacy of mixed surfactant systems in various applications.
- These findings aid in the optimized use of mixed surfactants for controlling interfacial properties.
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