Analysis of plasma activated water by gliding arc at atmospheric pressure: Effect of the chemical composition of water on the activation

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.