Influence of solution electrical conductivity and ionic composition on the performance of a gas–liquid pulsed spark discharge reactor for water treatment

Nau‐Hix, Chase; Holsen, Thomas M.; Thagard, Selma Mededovic

doi:10.1063/5.0054327

Cited by 16 publications

(28 citation statements)

References 62 publications

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“…Higher surface excess allows an increased probability for direct interaction with the gaseous electrons in the plasma above the interface. Similar findings were presented in a recent report, where an increase in the observed rate constant was measured due to higher surface accumulation with increasing solution conductivity …”

Section: Resultssupporting

confidence: 92%

Rate, Efficiency, and Mechanisms of Electrochemical Perfluorooctanoic Acid Degradation with Boron-Doped Diamond and Plasma Electrodes

et al. 2022

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The removal of per- or polyfluorinated alkyl substances (PFAS) has received increasing attention because of their extreme stability, our increasing awareness of their toxicity at even low levels, and scientific challenges for traditional treatment methods such as separation by activated carbon or destruction by advanced oxidation processes. Here, we performed a direct and systematic comparison of two electrified approaches that have recently shown promise for effective degradation of PFAS: plasma and conventional electrochemical degradation. We tailored a reactor configuration where one of the electrodes could be a plasma or a boron-doped diamond (BDD) electrode and operated both electrodes galvanostatically by continuous direct current. We show that while both methods achieved near-complete degradation of PFAS, the plasma was only effective as the cathode, whereas the BDD was only effective as the anode. Compared to the BDD, plasma required more than an order of magnitude higher voltage but lower current to achieve similar degradation efficiency with more rapid degradation kinetics. All these factors considered, it was noted that plasma or BDD degradation resulted in similar energy efficiencies. The BDD electrode exhibited zero-order kinetics, and thus, PFAS degradation using the conventional electrochemical method was kinetically controlled. On the contrary, analysis using a film model indicated that the plasma degradation kinetics of PFAS using plasma were mass-transfer-controlled because of the fast reaction kinetics. With the help of a simple quantitative model that incorporates mass transport, interfacial reaction, and surface accumulation, we propose that the degradation reaction kinetically follows an Eley–Rideal-type mechanism for the plasma electrode, and an intrinsic rate constant of 2.89 × 108 m4 mol–1 s–1 was obtained accordingly. The investigation shows that to realize the true kinetic potential of plasma degradation for water treatment, mass transfer to the interface must be enhanced.

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Section: Resultssupporting

confidence: 92%

Rate, Efficiency, and Mechanisms of Electrochemical Perfluorooctanoic Acid Degradation with Boron-Doped Diamond and Plasma Electrodes

et al. 2022

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“…A Spellman SL60PN1200 HV power supply was used with a custom-built circuit described in our previous work [15] to generate pulsed plasma in the bench-scale reactor. For the upscaled reactor, a TDK Lambda 102A-40kV-NEG power supply was used with a custom-build circuit shown in Figure S2.…”

Section: Electrical Circuitmentioning

confidence: 99%

Optimization of a gas–liquid plasma reactor for water treatment applications: Design guidelines and electrical circuit considerations

Nau‐Hix

Holsen

Thagard

2022

Plasma Processes & Polymers

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To provide insights into the design, optimization, and scale up of plasma reactors for water treatment, the influences of discharge energy, grounded electrode size and position, and number of high voltage (HV) discharge points on the production of reactive species and the degradation of 1,4-dioxane and perfluorooctanoic acid in a gas-liquid electrical discharge plasma reactor were assessed. Discharge energy and plasma area largely control the treatment

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“…It can be seen from SI Figure S4 that the change in the solution conductivity had a slight effect on the removal of PFOA. This observation is in accordance with Nau-Hix et al., finding that increasing conductivity exhibited a positive effect on the removal of PFOA in a point-to-point plasma reactor, and they attributed the increased removal to the salting out of PFOA (or other surfactant) to the plasma–liquid interface where the degradation occurs . These results indicated that the main effect of NO 3 – lies in the generation of RNS rather than the conductivity change.…”

Section: Resultsmentioning

confidence: 99%

Reactive Nitrogen Species Generated by Gas–Liquid Dielectric Barrier Discharge for Efficient Degradation of Perfluorooctanoic Acid from Water

Zhu

Sun

Zhang

et al. 2021

Environ. Sci. Technol.

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Perfluorooctanoic acid (PFOA) poses a serious threat to the ecological environment and biological health because of its ubiquitous distribution, extreme persistence, and high toxicity. In this study, we designed a novel gas–liquid dielectric barrier discharge (GLDBD) reactor which could efficiently destruct PFOA. PFOA removal efficiencies can be obtained in various water matrices, which were higher than 98.0% within 50 min, with energy yields higher than 114.5 mg·kWh–1. It was confirmed that the reactive species including e–, ONOOH, •NO2, and hydroxyl radicals (•OH) were responsible for PFOA removal. Especially, this study first revealed the crucial role of reactive nitrogen species (RNS) for PFOA degradation in the plasma system. Due to the generation of a large amount of RNS, the designed GLDBD reactor proved to be less sensitive to various water matrices, which meant a broader promising practical application. Moreover, influential factors including high concentration of various ions and humic acid (HA), were investigated. The possible PFOA degradation pathways were proposed based on liquid chromatograph–mass spectrometer (LC-MS) results and density functional theory (DFT) calculation, which further confirmed the feasibility of PFOA removal with RNS. This research, therefore, provides an effective and versatile alternative for PFOA removal from various water matrices.

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Influence of solution electrical conductivity and ionic composition on the performance of a gas–liquid pulsed spark discharge reactor for water treatment

Cited by 16 publications

References 62 publications

Rate, Efficiency, and Mechanisms of Electrochemical Perfluorooctanoic Acid Degradation with Boron-Doped Diamond and Plasma Electrodes

Rate, Efficiency, and Mechanisms of Electrochemical Perfluorooctanoic Acid Degradation with Boron-Doped Diamond and Plasma Electrodes

Optimization of a gas–liquid plasma reactor for water treatment applications: Design guidelines and electrical circuit considerations

Reactive Nitrogen Species Generated by Gas–Liquid Dielectric Barrier Discharge for Efficient Degradation of Perfluorooctanoic Acid from Water

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