Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor

Barbara J. W. Cole

Second Committee Member

Matthew Brichacek

Third Committee Member

William Gramlich

Additional Committee Members

Brian Frederick

Lynn Katz

Raymond C. Fort Jr.

Abstract

Pharmaceuticals and personal care products (PPCPs) are contaminants in water worldwide and the effects of the accumulation of these contaminants in the environment are a growing concern. Current water treatment methods involve chlorination and chloramination, which have the potential to create chlorinated by-products that are possibly more harmful than the starting material that was the target of decomposition. Alternative methods to chlorination are advanced oxidation processes (AOP). Previous studies of AOPs often focused on the rate at which the target compound is removed, but neglect to evaluate the by-products.

The compounds of interest in this study were chosen because of their frequent detection in groundwater and wastewater in concentrations of ng/L - µg/L. Acetaminophen is a widely used analgesic and enters wastewater through unmetabolized excretion in urine. N, N – diethyltoluamide (DEET) is a common insecticide and enters ground water through washing off skin or contaminated clothes. Caffeine is found in many popular drinks (coffee, tea, soda, and energy drinks) and enters wastewater through excretion in urine. Chloramphenicol is a broad spectrum antibiotic commonly prescribed that also enters wastewater through unmetabolized excretion in urine. The high occurrence of these compounds in wastewater is due to the widespread use of these compounds. Previous studies have shown the effectiveness of AOPs on these particular compounds, but few have studied the by-products present.

Analysis of by-products was carried out both by LCMS and by GCMS after samples were freeze-dried and derivatized via silylation. UV blanks and thermal blanks were carried out to ensure any degradation products observed were a result of hydroxyl radicals versus degradation due to UV irradiation or temperature degradation alone. Reactions were tested at various pH to study control of the degradation pathways through various reactive oxygen species (ROS) present. Computational studies of the mechanisms were implemented to support experimental data. Toxicity of by-products were assessed using an EPA program called ECOSAR (ECOlogical Structure-Activity Relationship Model) which calculates QSARs (quantitative structure-activity relationships).

The aim of this study was to identify by-products of an AOP method that utilizes UV irradiation to generate hydroxyl radicals from H2O2 which strongly oxidize and remove organic pollutants.

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