Abstract View
Concentration Depth Profile (CDP)-Based Multi-Sorption Layer Surface Tension Model
SHIHAO LIU, Cari Dutcher, University of Minnesota
Abstract Number: 378
Working Group: Aerosol Physics
Abstract
Surface tension plays a significant role in atmospheric aerosols, including aerosol nucleation, phase transitions, activation into cloud condensation nuclei. Recent predictive surface tension models using a mono-sorption layer framework is available for both organic and inorganic solutions (1). The model, however, considers the partitioning of solute and water molecules only between one surface layer and the bulk region, overlooking the continuous distribution of surface molecules at the surface. Here we discuss a binary-solution model that further divides the surface region into several layers to capture the continuity of molecule spatial distribution near the surface. Partition functions are established for both water molecules and solute molecules based on the molecule displacement. Treating the average number of displaced surface water molecules, the energy of bulk solute molecules, as well as energy difference of bulk and surface solute molecules as model parameters gives accurate prediction of surface tension of aqueous solutions. Published experimental and simulated results of concentration depth profile and number density of molecules/ions near the surface are used to obtain the parameters relevant to the number of solute molecules at each surface layer. Furthermore, the complexity of chemical compound of atmospheric aerosols motivates us to extend the model to predict surface tension of mixture solutions without additional parameter fitting. Coupled nonlinear equations are solved using neural network to predict surface tension with calculated number of molecules at the surface or in the bulk. Both binary and mixture models can predict surface tension over a wide range of concentrations, which can benefit the understanding of aerosol processes in the atmosphere.
[1] Boyer, H. C.; Dutcher, C. S. Atmospheric Aqueous Aerosol Surface Tensions: Isotherm-Based Modeling and Biphasic Microfluidic Measurements. J. Phys. Chem. A 2017, 121 (25), 4733–4742. https://doi.org/10.1021/acs.jpca.7b03189.