Date of Thesis

Spring 2018

Thesis Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science in Chemical Engineering

Major

Chemical Engineering

First Advisor

Dabrina D Dutcher

Second Advisor

Timothy M. Raymond

Third Advisor

Kelly Bickel

Keywords

Aerosols, glutaric acid, polymorph, hygroscopicity, dicarboxylic acids

Abstract

Because of the abundance of dicarboxylic acids in the atmosphere, they are commonly studied in the aerosol field, specifically investigating their hygroscopic and cloud condensation nuclei activity. Glutaric acid, being a water-soluble dicarboxylic acid is commonly used to model water activity in dicarboxylic acid aerosols. Variability associated with glutaric acid aerosols, specifically DRH and hygroscopic data, has been reported by several groups. We hypothesize that this variability is caused by its polymorphism. Glutaric acid exhibits dimorphism, meaning the molecule can form into two different types of crystal structures, an alpha and a beta polymorph. Glutaric acid naturally forms the beta polymorph, which is more stable. The alpha polymorph is the metastable phase. These polymorphs manifest themselves as a bimodal aerosol size distribution when analyzed by Scanning Mobility Particle Sizer or other aerosol mobility sizing methods. In this paper, we discuss the formation of the nanoscale alpha glutaric acid polymorph generated from an aqueous glutaric acid solution. The formation of both polymorphs from an aqueous solution has not been documented elsewhere. We have found that the alpha polymorph forms at faster crystallization speeds, with a lower aqueous solution concentration and a lower solution flowrate into the atomizer. This identification of the presence of polymorphism in glutaric acid aerosols under common laboratory generation conditions explains the variability present in studies associated with glutaric acid aerosols. Understanding of the conditions at which the alpha polymorph is present will allow others to avoid it when using glutaric acid as a dicarboxylic acid standard.

Available for download on Thursday, April 25, 2019

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