Investigating the Electrochemical Degradation of Perfluorooctanoic Acid (PFOA)

• Mia Bernstein, Chemical Engineering, University of Delaware

• Rachel Davidson, Chemistry & Biochemistry, University of Delaware

Per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” are man-made chemicals with extremely strong carbon–fluorine bonds. These substances were designed to resist degradation, making them extremely difficult to break down once released into the environment. This work explores two approaches targeting the electrochemical degradation of perfluorooctanoic acid (PFOA), which is one of the most widely documented harmful PFAS compounds.

In the first approach, we investigated how gold nanoparticle morphology affects the efficiency of PFOA electrochemical reduction. To isolate the effects of size, facet exposure, and surface roughness, gold nanoparticles were prepared with three distinct morphologies: Turkevich spheres, faceted gold nanocrystals, and raspberry-like nanospheres. Electrochemical surface area (ECSA) and linear sweep voltammetry measurements showed that direct PFOA adsorption on electrodeposited gold nanoparticles lowers the overpotential required to cleave C–F bonds compared to bare glassy carbon electrodes, with reduction behavior varying across different catalyst morphologies. Moving forward, we will continue to explore new gold nanoparticle syntheses and determine how differences in morphology impact degradation product distributions and the extent of PFOA degradation.

Through a second approach, we explored PFOA defluorination through electrochemical oxidation, comparing direct current (DC) against rapid alternating polarity (rAP) modes for reactions with reticulated vitreous carbon (RVC) and platinized titanium mesh working electrodes. Electrochemical oxidation of PFOA forms fluoride and CO2 as the main products. Fluoride concentrations were measured after the reaction using an ion-selective electrode (ISE). The reaction with a more oxidizing applied potential, which used a DC current, showed a significantly larger concentration of fluoride post-reaction compared to our rAP experiments, suggesting that a greater PFOA degradation was achieved under those conditions. Future work will involve studying how changes in electrode composition influence PFOA degradation by exploring different transition metal-oxide-functionalized anodes including electrodes functionalized with RuO2 and IrO2. We will also systematically explore how changes in the pulsed voltage profile, reaction time, and pH influence degradation.