PFAS Degradation in the Cathode Chamber of a Bioelectrochemical System Utilizing the West Branch Consortium (WBC-2)

Author

• Haoran Yang, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2026

Degree Name

Doctor of Philosophy

Department

Engineering Science

First Advisor

Liu, Jia

Abstract

Haoran Yang, for the Doctor of Philosophy degree in Engineering Science, presented on November 17, 2025, at Southern Illinois University Carbondale.TITLE: PFAS Degradation in the Cathode Chamber of a Bioelectrochemical System Utilizing the West Branch Consortium (WBC-2) MAJOR PROFESSOR: Dr. Jia Liu Per and polyfluoroalkyl substances (PFAS) persist in groundwater and resist conventional treatment because of the strength of the carbon–fluorine bond. This dissertation advances a bioelectrochemical systems (BES) strategy that couples an electroactive microbial consortium (derived from the inoculated West Branch Consortium, WBC 2) with poised cathodes to accelerate PFAS transformation, compares PFAS removal using nanomaterial-coated cathodes, and develops a mechanistic model linking electron availability, biofilm growth, sorption, and chain shortening kinetics. Bench scale two chamber reactors were compared across applied potentials (−650 and −450 mV vs. Ag/AgCl) and open circuit controls; analyses included solid phase extraction LC/MS/MS for PFAS and products, fluoride measurements, scanning electron microscopy with EDX, microbial community profiling, and, where relevant, XRD/XPS of nanomaterial modified electrodes. This research was guided by the following objectives: (i) to establish and optimize WBC 2–driven PFAS removal in deionized water and real groundwater, (ii) to quantify and interpret transformation intermediates and sorption to the cathode biofilm, (iii) to evaluate nanomaterial-coated cathodes for performance enhancement and durability, and (iv) to elucidate PFAS removal process via a calibrated process model. In two chamber BES cathodes inoculated with WBC 2 and poised at −450 mV, perfluorooctane sulfonate (PFOS) decreased from 100 μg/L to 0.84 ± 0.19 μg/L by day 21 (>99% removal). Daughter perfluoroalkyl carboxylates (notably PFOA, PFBA, PFPrA) formed transiently, and net fluoride was qualitatively detected despite analytical interferences, implicating C–F cleavage and stepwise chain shortening. In PFAS impacted groundwater, applied potentials similarly accelerated removal (e.g., PFOS 20.60 ± 2.20 to 0.54 ± 0.08 μg/L by day 21), and long term re amendment over ~664 days maintained high removal while short chain products accumulated at low μg/L and catholyte pH drifted upward. Sorbed species were detected on the electrode (e.g., PFPeA retained on brushes), indicating coupled degradation and partitioning. Together, these results demonstrate the potential for PFAS degradation under bioelectrochemical stimulation mediated by WBC-2 through an electron-driven biocatalysis process. Furthermore, cathode nano engineering was investigated to improve performance and manage intermediate build up. Magnetite/reduced graphene oxide (Fe₃O₄/rGO) coatings on carbon fiber brush cathodes delivered rapid and durable PFOS attenuation in WBC 2–driven BES (96.98 to 0.14 ± 0.01 μg/L by day 18), outpacing Fe₃O₄ only and uncoated electrodes while strongly suppressing PFOA accumulation (≤ ~ 0.20 μg/L during early operation). Upon re amendment after ~210 days, removal again proceeded rapidly, indicating coating stability. Post operation XRD/XPS confirmed persistent spinel iron oxide phases (no Fe⁰) and surface fluorine signatures on Fe₃O₄/rGO, while SEM/EDX showed coherent coatings that supported microbial attachment. These findings support a robust two stage mechanism in nano enabled reactors—early adsorption/catalysis followed by bioelectrocatalysis as biofilms mature. To interpret sparse time series and guide design, a mechanistic model was developed that (i) describes WBC 2 biomass with logistic growth modulated by electron availability at the cathode and by pH/fluoride inhibition; (ii) represents PFOS to PFOA to successive chain shortening reactions governed by Monod type kinetics; and (iii) includes reversible, kinetic sorption to the biofilm/electrode. Calibrated across reactor configurations and potentials, the model reproduced rapid early PFOS decay, transient intermediate peaks, and late tails attributable to desorption, while quantifying hidden fluxes between sampling points and the fraction of unmeasured products. This framework links electrode potential to biocatalytic capacity and provides diagnostic insight that is otherwise impractical to obtain experimentally at high frequency. Collectively, this dissertation integrates experiment, modeling, and materials design to (i) demonstrate WBC 2–mediated PFAS degradation and fluoride release under poised cathode conditions in both deionized water and field relevant groundwater, (ii) establish Fe₃O₄/rGO modified cathodes as durable accelerants that restrain intermediate build up, and (iii) provide a validated kinetic framework that connects electron supply, biofilm growth, sorption, and product evolution. The resulting scientific and engineering insights guided the optimization of the BES for PFAS removal in the cathode chamber, providing a lower energy pathway that couples biocatalysis with electrocatalysis for effective PFAS remediation and advancing understanding of the removal mechanisms in this complex system.