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09:34
Extraction and Characterization of Surfactants from Atmospheric Aerosols
Published on: April 21, 2017
Interplay between the surface adsorption and solution-phase behavior in dialkyl chain cationic-nonionic surfactant
I Tucker1, J Penfold, R K Thomas
1Unilever Research and Development Laboratory, Port Sunlight, Quarry Road East, Bebington, Wirral, UK.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 13, 2008
Summary
This study reveals nonideal mixing in cationic and nonionic surfactant adsorption at air-solution interfaces. Surfactant adsorption behavior deviates from ideal mixing theories, influenced by ethylene oxide chain length.
Area of Science:
- Surface Chemistry
- Colloid Science
- Physical Chemistry
Background:
- Understanding surfactant adsorption at interfaces is crucial for various applications.
- Existing theories of nonideal mixing in surfactant solutions do not fully explain observed behaviors.
- Cationic and nonionic surfactants exhibit complex interactions at the air-solution interface.
Purpose of the Study:
- To investigate the adsorption behavior of dihexadecyl dimethyl ammonium bromide (DHDAB) mixed with different nonionic surfactants (C12E3, C12E6, C12E12) at the air-solution interface.
- To determine deviations from ideal mixing and explore the influence of nonionic surfactant ethylene oxide chain length on adsorption.
- To correlate adsorption behavior with solution phase behavior and mixed critical aggregation concentration (cac).
Main Methods:
- Neutron reflectivity (NR) was employed to quantitatively assess adsorption at the air-solution interface.
- Surface tension measurements were conducted to complement NR data and analyze interfacial properties.
- Systematic variation of surfactant mixture composition and nonionic surfactant ethylene oxide chain length.
Main Results:
- Adsorption of DHDAB and nonionic surfactant mixtures showed significant departure from ideal mixing predictions.
- A critical composition exists below which the cationic surfactant, DHDAB, exclusively dominates the surface.
- The onset of nonionic surfactant adsorption increased with longer ethylene oxide chains (C12E3 < C12E6 < C12E12).
Conclusions:
- The observed nonideal mixing behavior is not adequately described by current theoretical models.
- Adsorption is strongly linked to the phase behavior of the bulk solution.
- Estimated monomer concentrations align qualitatively with variations in mixed critical aggregation concentration (cac).
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