Comparison of Chemistry Induced by Direct and Indirect Plasma Treatment of Water to the Effect of UV Radiation
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Comparison of Chemistry Induced by Direct and Indirect Plasma Treatment of Water to the Effect of UV Radiation I. M. Piskarev1 · I. P. Ivanova2 Received: 30 August 2019 / Accepted: 27 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The yield of redox reactions (Fe2+ oxidation and Mn7+ reduction in aqueous solutions) under the action of hot plasma radiation in liquid and species formed in the region of plasma discharge was measured. The goal of the investigation is to evaluate the role of hot plasma radiation as active factor compared to species generating in discharge itself. As source of active species we studied the spark discharge in air and in nitrogen (SD50 generator), the generator of corona discharge in air and low-pressure mercury UV lamp (λ = 253.7 nm). The yield of redox reactions for all sources was determined using detecting liquids; the mechanisms of these reactions were analysed. It was shown that chain reactions do not take place. When the yields were calculated, the stoichiometry of the reactions was taken into account. An analysis of the results shows that under the action of a spark discharge generator SD50, the main active factor is radiation. The role of active species formed in discharge region not more than 15%. Under the action of a spark discharge radiation, active species first form in the sample being processed, and then interact with substances dissolved in water. There is an indirect mechanism of action. Owing of this peculiarity, the redox properties of water, activated by hot plasma radiation, are the same as direct treatment of samples to hot plasma radiation. For a corona discharge plasma and radiation from a mercury lamp, such a mechanism does not occur. Keywords Spark discharge plasma radiation · Corona discharge plasma · UV lamp radiation · Oxidation · Reduction · Direct and indirect action
Introduction Cold plasma can make direct contact with an object without causing thermal damage. Species formed in plasma interact with a liquid through its surface [1]. Plasma processes are promising from the point of view of possible applications. Cold plasma treatment is used to influence the chemical composition of water and aqueous solutions [2, 3]. A feature of this type of treatment * I. M. Piskarev [email protected] 1
Skobeltsyn Institute of Nuclear Physics, Leninskie Gory, MSU, 1 (2), Moscow, Russia 119234
2
Privolzhsky Research Medical University, Minin and Pojarsky Sq., 10/1, Nizhny Novgorod, Russia 603005
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Plasma Chemistry and Plasma Processing
is that the concentration of active species in plasma is high, so the probability of their termination in interactions with each other is high [4]. As a result, the efficiency of the plasma treatment may decrease. In various papers, Plasma Activated Water (PAW) is discussed, see review [3]. PAW is obtained by the direct contact of cold plasma with water. In these works the effects of cold plasma itself and plasma radiation on water were not compared. It has be
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