Effect of Solute Core Curvature on Solubility

1. Effect of Solute Core Curvature on Solubility Luz Teresa Padró April 26, 2004.

2. Introduction • Aerosols are composed of: • Inorganic and organic matter • Implications of organics in cloud condensation nuclei (CCN) activity • Composition, structure and surface affect activation diameters at different supersaturations

3. Raymond and Pandis [2002] • Studied cloud activation of single component aerosol particles at 0.3% and 1% supersaturation • 15 compounds • Hygroscopic secondary organics • Hydrophobic primary organics • Compared results with classical Köhler theory and one that takes into account solubility

4. Results • Theoretical and experimental values do not agree • Attributing this to the particles solubility in water • More solute is being dissolved than that calculated by solubility studies • Is the organic completely soluble?

5. 0.3% Supersaturation

6. 1% Supersaturation

7. Modification of Results • Assumed everything dissolved • No core present • Theoretical and experimental values have better agreement • Low solubility compounds activation may be determined by the curvature or Kelvin effect alone

8. Complete Solubility Assumption

9. Köhler Theory where: pw(Dp) - water vapor pressure over the droplet diameter Dp po - water vapor pressure over a flat surface at the same temperature Mw - molecular weight of water σw - surface tension of water R - ideal gas constant T – temperature ρw - density of water ns - moles of solute

10. Köhler Curves

11. Critical Parameters Dpc and Sc • Critical Droplet Diameter, Dpc • Critical Saturation, Sc

12. Sc : Accounting for Solute where: ν - van’t Hoff factor ds - dry particle diameter ρs - density of the solute Ms - molecular weight of the solute

13. Compounds Studied • Adipic acid • Glutamic acid • Glutaric acid • Norpinic acid • Pinic acid • Pinonic acid

14. Method • Theory calculations: • ns required by theory • Dpc required for ns • mass of water in Dpc • nsolubility in mass of water • Ratio of ns/nsolubility for each compound

15. Theory to Solubility Table 1. Theory to solubility ratio for (a) 0.3% supersaturation and (b) 1% supersaturation. where: A – adipic acid GR – glutaric acid GM – glutamic acid N – norpinic acid PI – pinic acid PO – pinonic acid

16. Method II • Experimental Calculations: • nexperimental • Core diameters • Kelvin effect • greater than 1? • curvature enhanced-solubility

17. Theory to Experimental Table 2. Theory to experimental ratio for (a) 0.3% supersaturation and (b) 1% supersaturation.

18. Core diameter Mass Balance where: dw – core diameter ds – dry particle diameter ms – mass of solute Table 3. Dry core diameter for (a) 0.3% supersaturation and (b) 1% supersaturation.

19. Kelvin effect Table 4. Kelvin effect of compounds that have a core for (a) 0.3% supersaturation and (b) 1% supersaturation.

20. Summary of Results • Solubility shows no activation: • at both supersaturations • glutamic acid and pinonic acid • at 1% supersaturation • adipic acid, glutaric acid, norpinic acid and pinic acid

21. Summary of Results II • Experiments shows no activation: • At both supersaturations • glutamic acid • At 0.3% supersaturation • norpinic acid • Kelvin effect > 1 • Shows possibility of curvature-enhanced solubility • Will be studied using a dissolution kinetics model

22. Thank you!