Chemical Effects of Air Plasma Species on Aqueous Solutes in Direct and Delayed Exposure Modes: Discharge, Post-discharge and Plasma Activated Water

Abstract

The chemical interaction between non-thermal plasma species and aqueous solutions is considered in the case of discharges in humid air burning over aqueous solutions with emphasis on the oxidizing and acidic effects resulting from formed peroxynitrite ONOO -and derived species, such as transient nitrite and stable HNO 3 . The oxidizing properties are mainly attributed to the systems ONOOONOOH tentatively splits into reactive species, e.g., nitronium NO ? and nitrosonium NO 2 ? cations. NO ? which also results from both ionization of Á NO and the presence of HNO 2 in acidic medium, is involved in the amine diazotation/nitrosation degradation processes. NO 2 ? requires a sensibly higher energy than NO ? to form and is considered with the nitration and the degradation of aromatic molecules. Such chemical properties are especially important for organic waste degradation and bacterial inactivation. The kinetic aspect is also considered as an immediate consequence of exposing an aqueous container to the discharge. The relevant chemical effects in the liquid result from direct and delayed exposure conditions. The so called delayed conditions involve both post-discharge (after switching off the discharge) and plasma activated water. An electrochemical model is proposed with special interest devoted to the chemical mechanism of bacterial inactivation under direct or delayed plasma conditions.

Kinetics and Mechanism of Cr(VI) Reduction in a Water Cathode Induced by Atmospheric Pressure DC Discharge in Air

“…Also, peroxynitrite ONOO -could be other possible oxidizers [30,31]. Really, the formation of nitrite and nitrate ions was observed in the study [32] for the same discharge as presented here.…”

“…The acidity change (Fig. 6) confirms supposition on probable formation of ONOOH since pH decreases and tends to values around 3-3.5 (tentatively attributed to the transient presence of nitrous acid the acidity constant of pKa of which is reported [30]). But peroxynitrite was excluded from consideration for the following reasons.…”

Degradation of methylene blue using double-chamber dielectric barrier discharge reactor under different carrier gases

“…The NO x species was formed by discharge, when air was in the system (Manoj 2013). The resulting NO x (mainly NO and NO 2 ) dissolved in water forming strong HNO 2 (pK a 3.3) and HNO 3 (pK a -1.3) acidic, which were responsible for the pH decrease and the conductivity increase when using the air plasma (Rong, 2014;Brisset, 2015). The conductivity increased to 478 µS·cm -1 and 4150 µS·cm -1 when the discharge lasted for 40 min using the oxygen and air plasma.…”

State of the art in medical applications using non-thermal atmospheric pressure plasma

“…On the following day, cell viability was assayed using the MTS assay. **P \ 0.001 2009; Reuter et al 2012;Tanaka et al 2015b;Brisset and Pawlat 2016)]. These active species are typically generated in plasma-activated solutions.…”