“The Destruction Of Poly- And Perfluoroalkyl Substances (PFAS) At The
Plasma-Liquid Interface: Mechanisms, Reactor Design, And Process Optimization”
Ph.D. Dissertation Defense
Osakpolo Faith Isowamwen
Abstract
Perfluoroalkyl substances (PFAS) constitute a broad category of synthetic chemicals, comprising long-chain (LC), short-chain (SC), and ultra-short-chain (USC) compounds, recognized for their extensive environmental prevalence and potential health implications. These substances have diverse applications, including coatings, semiconductor fabrication, electronics and aerospace. The degradation of long-chain PFAS has been effectively demonstrated utilizing electrical discharge plasma, a reductive technology that leverages the adsorption of long-chain PFAS to the plasma-liquid interface for degradation. However, the efficacy of plasma alone in degrading SC and USC PFAS is limited due to their lower hydrophobicity compared to LC PFAS.
This study investigates the utilization of surfactant-assisted plasma treatment for the remediation of SC and USC PFAS in wastewater. The addition of cationic surfactants significantly enhances the mass transport of these PFAS by electrostatically binding with and facilitating their transport to the interface for degradation. As part of this study, various cationic surfactants with diverse structural groups were investigated to optimize the interfacial concentration and maximize the degradation efficiency of SC and USC PFAS. Pseudo-first-order reaction kinetics and defluorination efficiency were used as criteria to determine the most effective surfactant for each SC and USC PFAS. The research findings highlight two key factors that determine this effectiveness; firstly, the surface activity of the surfactant-PFAS complex determines the rate of degradation of the PFAS at the interface. Secondly, the molecular interactions between the surfactant and the PFAS at the interface significantly impact the orientation, position, and proximity of the PFAS to the plasma reactive species. These specific factors can be used to tailor the choice of surfactants for the effective plasma degradation of PFAS. Finally, the identified PFAS liquid and gaseous byproducts were used to propose degradation mechanisms.
Tuesday, June 11th
, 2024 at 10:00 am
CAMP 372
Zoom link: https://clarkson.zoom.us/j/98658322521 Meeting ID: 986 5832 2521
Advisor
Prof Selma Mededovic Thagard
Other Committee Members:
Prof Thomas Holsen
Dr Kim Taeyoung
Dr Yang Yang
Dr Ian McCrum