7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Removal Kinetics of PFAS utilizing Bubble Flotation and Non-Thermal Plasma
Streamer Discharges in Argon

David Alam 1, Samiuela Lee 1, Jungmi Hong 1, David F Fletcher 1, Dale McClure 1 2, David Cook 3,
PJ Cullen 1, and John M Kavanagh 1
12School of Chemical and Biomolecular Engineering, The University of Sydney
Department of Chemical Engineering, College of Engineering, Design and Physical Sciences,Brunel University3
Ventia Australia Pty Ltd
e-mail (speaker): david.alam@sydney.edu.au

The pollution of the environment and drinking waterwith trace quantities of per- and polyfluoroalkyl
substances (PFAS) has increasingly come under scrutiny
as these compounds are bioaccumulative and have links
to adverse health effects in humans such as kidney andtesticular cancer.1 These pollutants have been dubbed“Forever Chemicals” due to their recalcitrance todegradation by biological processes and persistence inthe environment.2 A growing need therefore exists todevelop low-cost and energy-efficient technologies
capable of achieving a high level of destruction of thisclass of pollutants at concentrations in the µg/L (ppb) as
detected in the environment.
A non-thermal plasma discharge generates a field ofhighly energy electrons and ionised species that wheninterfaced with a liquid surface, collide with watermolecules and introduce a range of highly reactivespecies (e.g. ·OH, ·O, H, O3, O2-).3 These radicals andsolvated electrons have been shown be effective at
destroying any PFAS molecules adsorbed at theplasma-liquid interface.4
The efficacy of a synergistic treatment reactor utilizing
non-thermal plasma streamer discharges in an argon
atmosphere and bubbles to transport the PFAS molecules
to the plasma-liquid interface was investigated to destroy
a structurally diverse suite of PFAS shown in Figure 1.
These compounds were plasma treated in individual
solutions of 2 L at 10, 25 and 50 ppb and incontaminated groundwater for up to 120 min.

Figure 1. Chemical structure of the PFAS investigatedusing non-thermal plasma

The trends in removal kinetics showed the treatabilityof the PFAS investigated correlated with the length of theperfluorinated carbon chain, with high removal rates(>99%) achievable for longer chain PFAS species suchas perfluorooctane sulfonate (PFOS) in contaminatedgroundwater after 120min of plasma treatment.
Quantification of breakdown products detected inorganic
fluoride ions (F-) as the primary breakdown productaccounting for up to 60% of the total fluorine initially inthe reactor with shorter chain species accounting for<5% of the total fluorine. The conductivity and ion
composition of the solutions influenced the degradation
rate by influencing the transport of PFAS to theplasma-liquid interface and surface coverage of the argonplasma discharge.
The synergy between the highly active radicals
produced by the non-thermal plasma and bubbles as atransport vector to the plasma-liquid interface was shown
to be effective remediation strategy applicable fordestroying a diverse range of PFAS pollutants present at
low concentrations in water.

References
1. European Environment Agency. Emerging chemicalrisksinEurope—“PFAS.”
https://www.eea.europa.eu/themes/human/chemicals/emergingchemical-risks-in-europe(2019)
doi:10.18356/e2f0ac16-en.
2. Jansen, K. ‘Forever chemicals’ no more? C&ENGlob. Enterp. 97, 28–32 (2019).
3. Locke, B. R., Sato, M., Sunka, P., Hoffmann, M. R.
& Chang, J. S. Electrohydraulic discharge andnonthermal plasma for water treatment. Ind. Eng.
Chem. Res. 45, 882–905 (2006).
4. Takeuchi, N. et al. Plasma-liquid interfacial
reaction in decomposition of perfluoro surfactants.
J. Phys. D. Appl. Phys. 47, (2014).