10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Validating a Surface Concentration Model
Anthony Toribio, Nonne Prisle, ANTHONY S. WEXLER, University of California, Davis
Abstract Number: 56 Working Group: Aerosol Chemistry
Abstract In 2013, Wexler and Dutcher published a paper using statistical mechanics to derive an expression for the surface tension of solutions over the full range of concentration from pure solvent to pure solute. The model only has a few free parameters yet was able to fit surface tension data for a wide range of organic and electrolytic solutes in water. In the current work we used the expression derived by Wexler and Dutcher along with the Gibbs adsorption isotherm for multicomponent systems to derive expressions for surface excess concentration. The parameters in the surface tension equation are the same as in the surface concentration equation, so if measurements are available for surface tension as a function of solute activity, the parameters can be identified and used to predict the surface concentration. In 2015 and 2016, Walz and coworkers published some of the first measurements of the surface concentration of alcohols on water; X-ray photoelectron spectroscopy was used to make the measurements.
In the current work, the derivation of the surface concentration equation is presented and the surface concentration predictions are compared with the measurements of Walz for 1-butanol, 1-hexanol, 1-pentanol, 1-heptanol, and t-butanol. The comparison sheds light on the model and measurements, but also on the meaning of surface excess concentration.