Date of Award

January 2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Hallie Chelmo

Abstract

The surface tensions and compositions of aqueous aerosols dictate surface-mediated processes, especially the growth of aerosol particles into cloud nuclei and interfacial chemical reactions. Surface tension is also an indirect proxy for the partitioning of organics to the surface due to enhanced organic activity, driven by a reduction in solubility. Model predictions are generally not available for most surfactant-laden multi-component aqueous solutions, despite the importance of surface tension. Our recent multi-component surface tension model uses competitive adsorption at the interface, but these results are not consistent with salting out.1 We have now applied these techniques to surfactants in pure water and aqueous solutions containing either NaCl or glutaric acid based on our previously derived two-parameter surface tension model from a monolayer adsorption framework2 developed for binary solutions. New model expressions incorporate the measured Critical Micelle Concentrations (CMCs) to reduce an empirical parameter. Further parameter reduction was achieved through correlations to the surface tension value at the CMC. The calculated model parameters for pure surfactant solutions are used to determine Setschenow constants in salty solutions to quantify the salting out effects at different surfactant concentrations. The model parameters and predictions we present improve organic surface-bulk partitioning predictions in aqueous aerosols, which has important implications for aerosol particle processing in the atmosphere.

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