Characterization of a hyperbolic vortex plasma reactor for the removal of aqueous phase micropollutants

Klymenko, Roman; de Kroon, Esther; Agostinho, Luewton L F; Fuchs, Elmar C; Woisetschläger, Jakob; Hoeben, Wilfred F L M

doi:10.1088/1361-6463/ad2b22

Cited by 4 publications

References 45 publications

(62 reference statements)

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Numerical analysis of vortex dynamics in hyperbolic funnels using computational fluid dynamics

Donepudi,

van de Griend,

Agostinho

et al. 2024

Physics of Fluids

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Experimental investigations into the characterization of vortices in hyperbolic funnels have shown efficient aeration properties. Certain regimes of vortices have been observed to exhibit high gas dissolution rates. This phenomenon has prompted inquiries into the underlying physical mechanisms at both micro and macroscopic scales. The present study employs computational fluid dynamics to numerically analyze the flow field organization inside these vortices, aiming to elucidate the observed high gas transfer rates. Transient simulations are performed on a three-dimensional radially structured hexahedral mesh, utilizing a multiphase Euler–Euler approach-based volume of fluid method for modeling, along with shear stress transport turbulence modeling based on k−ω equations with curvature correction. The evaluation of the two vortex regimes was conducted in terms of hydraulic retention time, water volume in the reactor, air–water interfacial area, and bulk mixing. Instabilities resembling Taylor vortices observed in Taylor–Couette flow systems emerge in the secondary flow field of these vortical structures, facilitating turbulent mixing. A qualitative analysis of the strength of these instabilities in terms of average vorticity per unit mass of water explains the high gas transfer efficiency. Despite high gas transfer rates, water exiting the funnel remains undersaturated under given operating conditions due to the short hydraulic retention time.

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Numerical analysis of vortex dynamics in hyperbolic funnels using computational fluid dynamics

Donepudi,

van de Griend,

Agostinho

et al. 2024

Physics of Fluids

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Preliminary evaluations of a upscaled falling film plasma reactor for the degradation of organic pollutants in water

Milardovich,

Santamaría,

Fina

et al. 2024

Preprint

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Preliminary evaluations of a upscaled falling film plasma reactor for the degradation of aqueous organic pollutants in batch operation mode are reported. A pulsed corona discharge in humid air is excited by short voltage pulses (< 100 ns) generated by a capacitive–storage power source and a high–pressure gas spark–gap. The number of wires of the high–voltage electrode as well as the interelectrode gap distance is selected in the experiments to improve the impedance matching between the pulsed power source and the reactor. Indigo carmine is chosen as the reference pollutant. 20 L of indigo carmine solution are completely decolored after 11 min treatment for a reactor mean power of 33 W. The electrical–energy efficiency per order of the processes is 0.25 kWh/m3. The generation of reactive species is also assessed in both the liquid and gas phases. Very low concentrations of NO2– and NO3– ions are found, practically not causing water acidification. The main gaseous species produced by the corona discharge are O3 and HO2 radicals. In addition, a kinetic model of the reactor is presented and compared with measured data. The results indicate that reactions in the stagnant liquid film next to the gas–liquid interface are essential to explain the measured removal rates. The rapid kinetic regime of the liquid film strongly accelerates the uptake rates of HO2 (rapidly converted to O2–) and O3, which far exceed the uptake rates predicted by the mass transfer coefficient for a reactionless film.

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Assessment of Cytotoxicity and Genotoxicity of Plasma-Treated Perfluorooctanesulfonate Containing Water Using In Vitro Bioassays

Windisch,

Klymenko,

Grießler

et al. 2024

Toxics

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The contamination of ground and surface waters with per- and polyfluoroalkyl substances (PFASs) is of major concern due to their potential adverse effects on human health. The carbon–fluorine bond makes these compounds extremely stable and hardly degradable by natural processes. Therefore, methods for PFAS removal from water are desperately needed. In this context, plasma treatment of water has been proposed as an effective method with reported removal rates exceeding 90%. However, the high reactivity of plasma discharge results in the formation of many reactive species, like radicals, ozone, or even solvated electrons, which lead to a complex reaction cascade and, consequently, to the generation of a wide variety of different chemical products. The toxicological properties of these PFAS breakdown products are largely unknown. The present study focuses on a toxicological assessment of PFAS-containing plasma-treated water samples. Aqueous solutions of long-chain perfluorooctanesulfonate (PFOS) were treated with various plasma-atmospheric regimes. Subsequently, plasma-treated water samples were subjected to in vitro bioassays. Cytotoxicity and genotoxicity were assessed with the MTS assay using human liver cells (HepG2) and the Ames MPFTM assay using Salmonella Typhimurium strains. Our results demonstrate varying cyto- and genotoxic properties of water containing PFAS breakdown products depending on the atmosphere present during plasma treatment. Based on the results of this study, the atmosphere used during plasma treatment affects the toxicological properties of the treated sample. Further studies are therefore needed to uncover the toxicological implications of the different treatment parameters, including the PFAS starting compound, the atmosphere during treatment, as well as the quantity of plasma energy applied.

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Characterization of a hyperbolic vortex plasma reactor for the removal of aqueous phase micropollutants

Cited by 4 publications

References 45 publications

Numerical analysis of vortex dynamics in hyperbolic funnels using computational fluid dynamics

Numerical analysis of vortex dynamics in hyperbolic funnels using computational fluid dynamics

Preliminary evaluations of a upscaled falling film plasma reactor for the degradation of organic pollutants in water

Assessment of Cytotoxicity and Genotoxicity of Plasma-Treated Perfluorooctanesulfonate Containing Water Using In Vitro Bioassays

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