Enhancing the Degradation and Bioremediation of Persistent Organic Pollutants Using Mechanochemistry

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants that are ubiquitous in the environment and harmful to human health. There is a range of available remediation techniques for the removal of PAHs such as incineration and microbial bioremediation. However, there are inherent challenges with the application of these existing techniques in the context of PAHs. Incineration of solid waste is energy consuming, adds to our global carbon emissions and often leads to the emission of harmful byproducts. By contrast, microbial bioremediation of PAHs is inherently limited by the poor bioavailability of PAHs due to their poor solubilities in organic solvents and indeed water. In this thesis, we successfully validate a green mechanochemical degradation process for the efficient removal of PAHs with no significant energy expenditures or harmful byproducts. We test the mechanochemical degradation process on pyrene (PYR) and show that in a matter of hours, almost all of the PYR could be degraded, leading to novel transformation products that could be used in a range of downstream processes. Since PAHs display low solubilities in most solvents, this limits their bioremediation potential. We therefore also demonstrate that mechanochemical ball milling can be used to improve the solubility of PAHs. Three novel binary eutectic solid forms were discovered during the course of experiments targeting the mechanochemical synthesis of binary cocrystals. The discovered eutectic solid forms were shown to be stable towards dissociation in solution and were found to display solubilities in ethanol that were an order of magnitude greater than that of the parent PAH.

Date of Award	Mar 2020
Original language	American English