Chemical Analysis of Secondary Electron Emission from a Water Cathode at the Interface with a Nonthermal Plasma

The electron dynamics in a stable and non-filamentary Argon plasma jet, generated using AC excitation at kHz frequencies and interacting with a liquid surface either at floating potential or electrically grounded were examined using laser Thomson scattering. In the case of a floating liquid, two discharge events were observed during each half-cycle of the applied sinusoidal voltage. In the grounded liquid case only one discharge event was observed, which occurred during the positive half period. Through spatio-temporal imaging of the discharge, its repetitive breakdown behavior was analyzed and divided into pre-, main-, and post-breakdown phases. The dynamics and presence of the various phases differed depending upon the grounding of the liquid. Thomson scattering measurements revealed maximum electron densities and temperatures of 6.0–6.3 × 1014 cm−3 and 3.1–3.3 eV for the floating liquid case and 1.1 × 1015 cm−3 and 4.3 eV in the grounded liquid case. Electron-driven reactions are the primary source of reactive chemical species in a plasma jet. Therefore, the electrical characteristics of the liquid sample can impact the fundamental physicochemical processes at play in the discharge, ultimately influencing its chemical composition.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of a kHz sinusoidal Argon plasma jet impinging on water using Thomson scattering and fast imaging

Slikboer¹,

Walsh²

2021

“…This will make the simulation result of the I-V character match the experimental result. To give deionized water such conductivity, it is assumed that a small amount of ions, Na aq + /Cl aq − , are present in the water [47,48]. The existence of ions will account for the slight increase in pH during the plasma treatment, as will be discussed hereinafter.…”

Section: Description Of the Simulation Modelmentioning

confidence: 99%

1D fluid model of the interaction between helium APPJ and deionized water

Liu¹,

Liu²,

Luo³

et al. 2022

Atmospheric pressure plasma jets (APPJs) are widely used for the treatment of water-containing substances such as human tissue, leading to a necessity of understanding the interaction between APPJs and water solutions for the development of plasma biomedicine. The reported two- or three-dimensional fluid models are shown to be an effective method for this study. However, owing to the complex chemistry in APPJ-water interaction, little of them could provide a quantitative estimation of reactive species, which are difficult to be measured but of much interest in the applications. In this paper, a one-dimensional fluid model is developed to simulate the interaction between a helium APPJ and deionized water, which incorporates a relatively comprehensive chemistry both in gas and liquid phases but with a moderate computational load. The composition and distribution of reactive species are quantified during a plasma treatment time of 6 min, which is typical in practice. By considering the sidewise loss inside the quartz tube, the air mixing outside the quartz tube, the conductivity of deionized water, and the chlorine evolution reaction, the simulation results agree well with the experiments. It is found that the plasma could be divided into three regions with much different physicochemical properties, mainly due to the sidewise loss, the air mixing and the water evaporation. In plasma-activated water, H2O2aq and HNO2aq/NO2aq- are the dominant reactive species, and OHaq is the key intermediate species for the transformation among other reactive species. Finally, the chemical pathways for the production of aqueous reactive species are elucidated.

“…The fluxes of positive ions and electrons to the surface of the solution are the same. But the energies are different, because cathode potential drops are hundreds of volts, and anode drops are tens of volts [22,23]. For this reason, the concentrations and rates of formation of particles that capable oxidize Fe 2+ to Fe 3+ (OH, H 2 O 2 , HO 2 .…”

Section: Process Mechanism Analysismentioning

confidence: 99%

Synthesis of oxygen-containing iron powders and water purification from iron ions by glow discharge of atmospheric pressure in contact with the solution

Shutov¹,

Ivanov²,

Rakovskaya³

et al. 2020

The formation of precipitation under the action of a direct current atmospheric pressure discharge in air on an iron sulfate (II) solution, which was the cathode and anode, was studied. As turbidimetric kinetics measurements have shown, the process, which proceeds both in the cathode and in the anode, has two stages. At the first stage (slow), a colloidal solution is formed, which then (the second stage, faster) is destroyed with the formation of a flocculent precipitate. The characteristic process times for both stages were found depending on the discharge current, the increase of which led to an increase in the deposition rate. The deposition rate in the cell with a liquid cathode was higher than in the cell with a liquid anode. For this reason, the amount of precipitate formed in the cell with the liquid cathode was greater than in the cell with the liquid anode at the same treatment time. Particle sizes of colloidal solutions and sediments were determined by scanning electron microscopy and dynamic light scattering . The sizes of both colloidal particles and sediment particles for the liquid anode were significantly smaller than for the liquid cathode. X-ray diffraction analysis showed that the precipitations obtained are amorphous, and their calcination turns them into γ-Fe2O3. Based on the data of elemental analysis and others, the composition of micelles was proposed, which included Fe(OH)3, SO4–, and H2O. An analysis of the mechanisms of the processes showed that the most probable chain of transformations involves the oxidation of Fe2+ by HO2 and H2O2 molecules to Fe3+, which irreversibly reacts with OH– to form Fe(OH)3.