Water Modification by Cold Plasma Jet with Respect to Physical and Chemical Properties

This work is devoted to unbuffered and buffered water treatment by means of atmospheric pressure cold plasma of electrical discharges. The interest in the activation of these two liquids by plasma-induced, gaseous-phase chemistry ranges over a wide area of potential applications and interdisciplinary scientific fields. These include biology, medicine, sanitation, environmental restoration, agriculture, etc. Atmospheric pressure cold plasma is here produced in the form of a plasma jet and set into physical contact with the liquid specimens. The operational window of the treatment, in terms of plasma reactivity, is determined by means of UV-NIR optical emission spectroscopy, and the treated liquids are probed in a variety of respects. Evaporation rate, temperature, acidity and basicity, resistivity, and oxidation-reduction potential are measured as a function of the treatment time, either in-situ or ex-situ. The formation of principal reactive oxygen species, i.e., •OH, H2O2 and O2•−, with a plasma jet mean power lower than 400 mW, is eventually demonstrated and their concentration is measured with original methods borrowed from the biology field. The experimental results are linked to reports published over the last ten years, which are compiled in a brief but meaningful review.