Atmospheric Pressure Glow Discharges Generated in Contact with Flowing Liquid Cathode: Production of Active Species and Application in Wastewater Purification Processes

Abstract

Miniaturized atmospheric pressure glow discharges (APGDs) were generated in contact with small sized flowing liquid cathode systems. As anodes a solid pin electrode or a miniature flow Ar microjet were applied. Both discharge systems were operated in the open to air atmosphere. Hydrogen peroxide (H 2 O 2) as well as ammonium (NH 4 ?), nitrate (NO 3-), and nitrite (NO 2-) ions were quantified in solutions treated by studied discharge systems. Additionally, an increase in the acidification of these solutions was noted in each case. Emission spectra of the near cathode zone of both systems were measured in order to elucidate mechanisms that lead to the formation of active species in gas and liquid phases of the discharge. Additionally, the concentration of active species in the liquid phase (H 2 O 2 , NH 4 ? , NO 3 and NO 2-) was monitored as a function of the solution uptake rate and the flow rate of Ar. The suitability of investigated discharge systems in the water treatment was tested on artificial wastewaters containing an organic dye (methyl red), hardly removable by classical methods non-ionic surfactants (light Triton x-45 and heavy Triton x-405) and very toxic Cr(VI) ions. Preliminary results presented here indicate that both investigated flow-through APGD systems may successfully be applied for the efficient and fast on-line continuous flow chemical degradation of toxic and hazardous organic and inorganic species in wastewater solutions. Keywords Atmospheric pressure glow discharge Á Degradation of hazardous chemicals Á Plasma water treatment processes Á Plasma-liquid interaction

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

“…The calculation gave the following results for the conditions of Fig. 4: 20 mA, u = 2.4 9 10 -3 atoms per 100 eV or 4.7 9 10 -2 g per 1 kW 9 h; 80 mA, u = 3.0 9 10 -3 atoms per 100 eV or 5.8 9 10 -2 g per 1 kW 9 h. The close value of 9 9 10 -3 atoms per 100 eV was obtained in study [9] for Ar discharge. Also, we can compare these results with the data obtained for decomposition of organic substances.…”

“…In study [8] the K 2 Cr 2 O 7 concentration was 8 9 10 -4 mol/l, whereas in [9] it was 2 9 10 -3 mol/l. In both studies Cr 6?…”

“…Figure 7 shows the changes in the rates of most important reactions as a function of processing time. It appears that reaction (45) with Á H radical, which was assumed as the main one in studies [7][8][9], does not practically influence the Cr 6? reduction process in spite of a large rate constant, whereas reactions 45, 46 with HO 2 Á and H 2 O 2 are the main ones.…”

“…The action of a DC discharge at atmospheric pressure in argon on the solution of potassium dichromate was studied in [8,9] at the discharge current of 40 mA. In study [8] the K 2 Cr 2 O 7 concentration was 8 9 10 -4 mol/l, whereas in [9] it was 2 9 10 -3 mol/l.…”

Atmospheric pressure dielectric barrier discharge for the remediation of soil contaminated by organic pollutants

“…Non-thermal plasmas (NTPs) are regarded as promising advanced oxidation processes (AOPs) for the sustainable and efficient removal of organic pollutants from wastewater (Ognier et al 2009;Hijosa-Valsero et al 2013;Iya-Sou et al 2013;Jamróz et al 2014;Magureanu et al 2015;Stratton et al 2015) and polluted gas (Ostapczuk et al 2008;Malik et al 2011;Jolibois et al 2012;Bao et al 2014;Zhang et al 2015). During the last few years, they have started to be examined for soil remediation (Wang et al 2010;Lou et al 2012;Ognier et al 2014;Aggelopoulos et al 2015a).…”