Mechanochemical Destruction of Per- and Polyfluoroalkyl Substances in Environmental Media by Planetary Ball Milling
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Authors
Turner, Lauren Paige
Date
2024-03-18
Type
thesis
Language
eng
Keyword
PFAS , Per- and polyfluoroalkyl substances , organic contaminants , soil , remediation , ball milling , planetary ball mill , mechanochemical destruction
Alternative Title
Abstract
Per- and polyfluoroalkyl substances (PFAS) are an abundant and diverse group of anthropogenic, fluorinated organic chemicals that are ubiquitous in the environment. PFAS can adsorb to soils through hydrophobic and electrostatic interactions, resulting in contaminated sites with high retention in soils. PFAS impacted soils can act as sources of exposure to humans or sources of contamination to groundwater. Due to human health concerns and increasingly protective regulations, there is a demand for destructive remedial technologies for PFAS-impacted soils. The objective of this work was to evaluate the destruction of PFAS in environmental solid media. Using a benchtop planetary ball mill with stainless steel grinding media and a 250 mL grinding jar, the remediation of PFAS-impacted media and aqueous film forming foam (AFFF)-impacted media by ball milling was studied.
Results demonstrated that PFAS can be destroyed in single compound PFOS- or PFOA-amended sand, dual compound PFOS- and PFOA-amended silicates and carbonates and multi-compound AFFF-amended sand. Water content of media was a significant hinderance to PFOS and PFOA destruction, with most saturated trials resulting in negligible destruction. In 100% water saturated media, potassium hydroxide (KOH) as a co-milling reagent was effective at improving destruction up to 99% PFOS and 92% PFOA in amended nepheline syenite sand. KOH resulted in increased recovery of fluoride post-milling, suggesting improved defluorination or improved fluoride extraction in the presence of KOH. KOH as a co-milling reagent in AFFF-amended silica sand influenced perfluorocarboxylic acid (PFCA) transformation byproduct distribution. In diverse media, a range of PFAS were demonstrated to be destroyed without-KOH as a co-milling reagent, proving media and soil components can become reactive upon ball milling. It was identified that electrons are a reactive species generated from environmental media. High resolution mass spectrometry was employed to evaluate target and non-target transformation byproducts, and in combination with electron generation and fluoride measurements, results provided evidence to suggest an electron initiated reductive destruction mechanism, likely coupled with other pathways. Results from this work identified key factors to consider in applying ball milling for remediation and suggest further study and scale up should be explored.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.