Date of Award

2025

Document Type

Thesis

Degree Name

MS in Chemistry

Department

Chemistry

First Advisor

Anne Vazquez

Second Advisor

David Brown

Third Advisor

Enju Wang

Abstract

The oil sands in Alberta, Canada are being destroyed by oil extraction because remediation methods have proven largely ineffective. One toxic byproduct of oil extraction is a family of cyclical surfactant organic acids known as naphthenic acids (NAs). They are toxic to aquatic life, including fish, frogs, and aquatic birds. It is suspected that NAs bind to humic acid, a major organic component of soil, in dissolved organic matter in natural water, making them difficult to remove by conventional remediation methods. This problem prompts the following question: what is the binding mechanism between NAs and humic acid when dissolved in aqueous solution? Fluorescence quenching experiments were used to deduce the binding mechanism between model NAs and humic acid. Fluorescence quenching refers to reducing the fluorescence intensity of a given substance. The Stern-Volmer method was used to determine if the quenching mechanism is static (binding) or dynamic (collisional) for model NAs. For static quenching, binding constants were calculated to determine the strength of the binding. Our findings show that NA model compounds with more compact structures quench the fluorescence of HA more strongly than the less compact structures. Based on the results, we propose two possible binding mechanisms between NAs and HA for further investigation: nonpolar interactions or polar interactions such as hydrogen bonding and acid-base interactions. Understanding how NAs bind to humic acid in dissolved organic matter may provide insights into new effective remediation methods in the oil sands.

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