AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Surface Tension Modeling of Binary and Multicomponent Atmospheric Aqueous Aerosols
HALLIE BOYER, Cari Dutcher, University of Minnesota, Twin Cities
Abstract Number: 243 Working Group: Aerosol Chemistry
Abstract Surface properties of aqueous solutions are an important diagnostic of atmospheric aerosol behavior because of their effect on particle interactions with the ambient, such as condensation of water vapor and radical species uptake, as well as optical properties and particle morphology. Previously, a predictive model was developed using a statistical mechanical approach for surface tension of both electrolyte and non-electrolyte aqueous solutions across the entire solute concentration range (Wexler and Dutcher, J. Phys. Chem. Lett., 2013). While the adjustable model parameters had statistical mechanical interpretations, in practice they remained largely empirical.
In this talk, the parameters in this surface tension model are related to solute molecular properties of aqueous solutions, reducing the number of free parameters down to one for both organic and electrolyte solutions in binary solutions. For organics, sorption tendencies suggest the importance of hydrophilic functional group spacing and number of methyl groups. For electrolytes, surface adsorption of ions follows the simulations of Pegram and Record, J. Phys. Chem. B 2007. In order to apply the model to more complex systems, the model approach is extended to multi-component aqueous solutions containing solutes of varied molecular sizes, where competitive adsorption between solute species is expected at the surface. Noteworthy agreement between multicomponent and binary models is found for a NaCl-NaNO3 system, where the size-related model parameters for a NaCl-NaNO3 system are consistent with the respective parameters from the single solute cases. Partition functions for solutes of varying size are also identified with the potential of addressing the different solute sizes of multicomponent systems. Excellent agreement has been found between the model predictions and experimental data obtained both from literature and using a new microfluidic tensiometry method developed by our group.