Physicochemical properties of plasma activated water obtained with an atmospheric pressure water–cathode glow–type discharge

B. SANTAMARÍA; M. FERREYRA; J. C. CHAMORRO; E. CEJAS; B. FINA; L. PREVOSTO

Congreso; XX Materials Research Society (MRS) Meeting 2022; 2022

Non–thermal discharges in atmospheric pressure air in contact with water produce large amounts of reactive species in the gas–phase that can enter into the water by diffusion, thus inducing the formation of secondary reactive species in the liquid–phase; including those long–lived species such as NO2¯, NO3¯ and H2O2. [1] Depending on the controllable parameters of the discharge the plasma activated water (PAW) can acquire different physicochemical properties, resulting in various applications (e.g., agriculture [2]) Physicochemical measurements of PAW obtained through a water–cathode glow–type discharge in atmospheric pressure air operating in open and closed reactors are reported. A large volume of 1 L of distilled water was treated for 30 min. In both cases, low pH values  2.5 and very high–levels of NO3¯ (up to 400 mg/L) in the water were obtained, however in the closed system no H2O2 was found and high–concentrations of nitrite (62 mg/L) were measured; while in the open system large levels of H2O2 was observed (45 mg/L) and no NO2¯ was found. Likewise, the electrical conductivity value in the case of the closed system (1732 µS/cm) was significantly higher than in the open system (950 µS/cm). The reasons for these different behaviors in terms of the PAW chemistry are discussed. Also the time–stability of PAW was measured.