Plasma activated water is a chemically active aqueous medium characterized by the presence of reactive oxygen and nitrogen species created by plasma exposure. This particular chemical composition is the starting point of extensive research studies in several domains such as bio-disinfectant in biomedical applications or as fertilizer in agricultural applications. These various applications need adjustments of the PAW properties and consequently require a better control of the PAW chemical composition. To achieve this aim, a UV spectrophotometric method (190–255 nm) is implemented to simultaneously detect the nitrate and nitrite ions in plasma activated water by a gliding arc discharge reactor at atmospheric pressure. The method, tested in plasma activated distilled water (PADW) and in plasma activated tap water (PATW), shows significant increases of nitrite and nitrate concentrations. Preliminary results on PADW and PATW kinetics evolutions highlight a different behavior of the temporal post-discharge reactions leading to non-conversion of the nitrite ions in the case of PATW. The near non-existence of acidification during and after plasma activation encountered in PATW is due to high levels of carbonate species in tap water acting as a buffer solution. Indeed, the presence of hydrogen carbonate (HCO3−) leads to the acidity consumption during plasma activation whereas the presence of non-dissolved limestone in hard water (CaCO3) acts as carbonates reserve, and this induces the acidity consumption after plasma treatment.
The non-thermal plasma technologies (NTP) have been proved to be an alternative for air and water pollutants treatment. The goal of this paper is to emphasize the effect of the different non-thermal plasma mini-reactor configurations on the soluble organic compounds' removal from water. Therefore, a soluble organic dye (Reactive Blue 19) solution has been treated in an NTP experimental reactor using different electrodes configurations. The influence of the different geometrical configuration of the reactors, such as electrodes shape and distance between them, on Reactive Blue 19 dye decolourization have been studied. The dye solution decolourization has been measured using colorimetric methods and upon the measurements results the energy efficiency EEf (g/kWh) of the dye removal have been calculated. The experimental results have shown that the electrochemical processes occurring in plasma and, consequently, the dye removal rate are significantly depending on the electrodes' shape. The best results have been obtained for using a reactor having one sharp active electrode and one horizontal plan section for the outlet electrode, while the distance between them was 4 mm.
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