Experimental Investigation of the Roles of Non-oxidative Species in
Plasma-based Water Treatment
Chiagozie Chukwukwute
Poly -and perfluoroalkyl substances (PFAS) are a group of toxic non-oxidizable compounds that are used in the manufacturing of many consumer goods. While plasma treatment has demonstrated efficacy in degrading PFAS into shorter chain compounds, the conditions required for complete mineralization and the plasma species capable of degrading these non-oxidizable compounds remain unknown.
This work deconvolutes the individual contributions of photons, radicals, and other non-oxidizing species in perfluorooctanoic acid (PFOA) degradation and defluorination by employing the COST jet operating in mixtures of helium and other admixture gases at atmospheric pressure. Plasma was generated using a 13.56 MHz radio-frequency (RF) power supply, and the jet was employed to treat 2.5 mL aqueous samples.
Preliminary results revealed that the jet is capable of degrading concentrations of PFOA up to 50 ppm, at different low conversion rates, depending on the process gas mixture. Following a 120-minute treatment,
PFOA degradation amounts ranging from 20% to 70% have been recorded in experiments where applied voltage, gas flowrate, gas composition, and parent compound concentration were varied. The low PFOA degradation rates were explained by low hydrogen radical and photon fluxes generated by the COST jet compared to other plasma sources. The main byproduct of degradation was perfluoroheptanoic acid (PFHpA), indicating stepwise degradation of PFOA.
Monday, 10/7/2024 at 4:30 pm CAMP 176
Chiagozie Chukwukwute is a second year Ph.D. student in the Chemical and Biomolecular Engineering department at Clarkson University. She has an undergraduate degree in Mechanical Engineering from Nnamdi Azikiwe University in Nigeria. Since Fall 2023, she has been conducting research on plasma technologies for wastewater treatment at the Plasma Research Laboratory under the guidance of Prof. Selma Mededovic-Thagard.