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Updated: Jun 23, 2026
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Extraction and Characterization of Surfactants from Atmospheric Aerosols
Published on: April 21, 2017
Using surface tension data to predict differences in surface and bulk concentrations of nonelectrolytes in water
Laurel M Pegram1, M Thomas Record
1Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
Summary
The solute partitioning model (SPM) quantifies how nonelectrolytes interact with the air-water surface. This model reveals consistent water layer thickness at the surface, regardless of the solute type.
Area of Science:
- Physical Chemistry
- Surface Science
- Thermodynamics
Background:
- The solute partitioning model (SPM) was previously established for interpreting surface tension increments (STI) of salts, acids, and bases.
- Understanding solute behavior at interfaces is crucial in various chemical and biological processes.
Purpose of the Study:
- To extend the SPM for a quantitative interpretation of surface tension increments (STI) of nonelectrolytes.
- To determine local-bulk partition coefficients (K(p)) and water layer thickness (b1σ) at the air-water surface for nonelectrolytes.
Main Methods:
- Utilized the solute partitioning model (SPM) to analyze surface tension increments (STI) of various nonelectrolytes.
- Calculated local-bulk partition coefficients (K(p)) and the amount of water per unit area (b1σ).
- Assessed the exclusion/accumulation of solutes at the air-water interface.
Main Results:
- Sucrose showed the largest positive STI, leading to a minimum estimate of b1σ of 0.20 H(2)O/Å(2), suggesting a surface region of approximately two water layers.
- Partition coefficients for nonelectrolytes varied from moderate exclusion (urea) to moderate accumulation (glycerol, ethylene glycol).
- The determined b1σ value is consistent across different solutes and surfaces, indicating a fundamental property of the air-water interface.
Conclusions:
- The SPM provides a robust framework for interpreting nonelectrolyte behavior at the air-water surface.
- The estimated surface region thickness (b1σ) appears to be a universal constant, independent of the specific solute or surface.
- Unlike salt ions, nonelectrolytes do not exhibit Hofmeister series-like patterns at the air-water interface.
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