Date of Award

2026-08-01

Degree Name

Doctor of Philosophy

Department

Chemistry

Advisor(s)

Dino Villagrán

Abstract

Ensuring universal access to safe water is a critical global challenge, particularly due to pollution from contaminants of emerging concern such as per- and polyfluoroalkyl substances (PFAS). These synthetic fluorinated chemicals have been widely used since the late 1940s because of their chemical stability and hydrophobic/lipophobic properties. However, the toxicity and persistence of legacy PFAS, including PFOA and PFOS, led to their gradual phase-out and replacement by shorter-chain alternatives such as GenX and PFBS. These replacement PFAS remain less explored in terms of reliable detection and degradation strategies, despite increasing evidence of their environmental occurrence, mobility, and potential toxicity. The first stage of PFAS remediation requires robust analytical methods to assess their occurrence and distribution in water. Conventional quantification relies on LC-MS/MS, which provides excellent sensitivity at ppt levels but is expensive, time-consuming, and not suitable for rapid on-site monitoring. Electrochemical sensors offer a promising alternative because they can be sensitive, affordable, and deployable. However, PFAS are generally redox-inactive under conventional electrochemical conditions, requiring indirect sensing strategies based on surface modified electrodes and secondary redox probes. In this dissertation, the electrochemical behavior of GenX was first evaluated using gold-based electrode platforms (Chapter 2). The results showed that the apparent oxidation signal observed at basic pH originated from ammonia/ammonium oxidation associated with the ammonium salt form of GenX, rather than direct oxidation of the HFPO-DA anion. This finding demonstrated the limitations of direct GenX detection and motivated the development of indirect sensing approaches. In Chapter 3, the hydrogen evolution reaction (HER) was explored as an environmentally friendly and universally available electrochemical probe to address MIP's limitation. Using a molecularly imprinted polymer based on electropolymerized o-phenylenediamine, HER-enabled GenX detection achieved a limit of detection of 5 ppt and a limit of quantification of 16 ppt, meeting the 2024 EPA regulatory level for GenX. The HER probe maintained the binding properties of the imprinted film, with an adsorption constant of 7.31 x 1011 cm3 mol-1 , comparable to values reported using conventional redox probes. Chapter 4 explores molecular electrografted layers for sensing (MELS) to further improve sensing performance. MELS were developed on gold and glassy carbon electrodes using fluorinated building blocks. These sensors reached limits of detection of 1 ppt and 4 ppt, respectively, with adsorption constants of 7.81 x 1012 and 6.08 x viii 1012 cm3 mol-1 . The MELS platforms also showed good selectivity in the presence of other PFAS and moderate interference in the presence of Humic acids, with recovery values comparable to LC-MS/MS. Finally, in Chapter 5, electrochemical PFAS degradation was investigated using bimetallic Ni-Co Porphvlar materials as heterogeneous electrocatalysts. These materials were characterized by XPS and evaluated for the degradation of PFOA, GenX, PFOS, and PFBS at ppm and environmentally relevant concentrations. Both Ni-Co compositions showed high degradation performance toward PFOA, GenX, and PFOS, while PFBS was more resistant, especially when tested individually. Adsorption controls indicated that PFAS adsorption on the Porphvlar surface was largely reversible without applied current, supporting that sustained removal occurred mainly through electrochemical degradation. Reusability tests showed stable performance across five cycles. LC-MS analysis of PFOA degradation revealed the transient formation and subsequent decrease of shorter-chain PFCA products, suggesting a stepwise chain-shortening pathway in which intermediates are further degraded over time. Overall, this dissertation demonstrates that electrochemical platforms can contribute to PFAS remediation by combining sustainable, selective sensing strategies with destructive degradation approaches for legacy and emerging PFAS.

Language

en

Provenance

Received from ProQuest

File Size

145 p.

File Format

application/pdf

Rights Holder

Diego Camilo Puerto Diaz

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Chemistry Commons

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