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Updated: Jul 12, 2026
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Extraction and Characterization of Surfactants from Atmospheric Aerosols
Published on: April 21, 2017
Equilibrium surface adsorption behavior in complex anionic/nonionic surfactant mixtures
J Penfold1, R K Thomas, C C Dong
1STFC, Rutherford Appleton Laboratory, Chilton, Didcot, OXON, Oxford University, South Parks Road, Oxford.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 30, 2007
Summary
The study reveals how calcium ions influence surfactant mixtures, causing structural changes from micelles to vesicles in sodium 6-dodecyl benzene-4 sulfonate (SDBS) and C12EO8 systems, unlike SDBS/C12EO23. This impacts surface adsorption behavior significantly.
Area of Science:
- Physical Chemistry
- Colloid and Surface Science
- Materials Science
Background:
- Understanding surfactant mixtures is crucial for applications in detergents, emulsification, and drug delivery.
- Investigating the self-assembly and interfacial behavior of mixed surfactants provides insights into complex fluid systems.
Purpose of the Study:
- To investigate the equilibrium surface adsorption and solution microstructure of sodium 6-dodecyl benzene-4 sulfonate (SDBS) mixed with nonionic surfactants C12EO8 and C12EO23.
- To determine the effect of divalent (Ca2+) and monovalent (Na+) ions on the microstructure and adsorption behavior of these mixed surfactant systems.
Main Methods:
- Neutron reflectivity (NR) and small-angle neutron scattering (SANS) were employed to probe solution microstructure and surface adsorption.
- Systematic variation of surfactant composition and electrolyte concentration (Ca2+, NaCl) was performed.
Main Results:
- SDBS/C12EO8 and SDBS/C12EO23 mixtures form small globular micelles in solution.
- Addition of Ca2+ to SDBS/C12EO8 induces a transition to vesicle phases, while SDBS/C12EO23 shows limited transition.
- Ca2+ ions promote multilayer formation at the air-solution interface for SDBS-rich compositions, unlike NaCl.
Conclusions:
- Divalent ions like Ca2+ significantly alter the self-assembly and interfacial properties of mixed surfactant systems, leading to phase transitions and multilayer formation.
- The mixing behavior of SDBS with nonionic surfactants is non-ideal and influenced by ionic strength and surfactant chain length.
- Regular solution theory (RST) provides a partial explanation for nonideality but does not fully capture the complex interactions, especially in the presence of Ca2+.
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