Effect of storage temperature on pH and conductivity of reverse osmosis water treated with atmospheric plasma

Abstract

We believe that the reactions involved in plasma-activated water (PAW) produc­tion are a consequence of long-lived reactive oxygen and nitrogen species (e.g., NO, O, OH, ONOO-, and H2O2) that are transferred from the plasma environment to liquid. Based on the assumption of reaction continuity in water treated with atmospheric plasma, we devised an ex­periment to monitor pH and electrical conductivity in samples of reverse osmosis water, before and after treatment. We used gliding arc discharge that was operated by a mixture of air + humid air at a flow of 10 L/min to evaluate the continuation of these chemical reactions at different storage temperatures: room temperature (24°C) for group 1 and refrigeration temperature (3°C) for group 2. To obtain PAW, we treated three 250-mL samples of reverse osmosis water for 10, 20, and 30 min of exposure to the plasma. After treatment, we performed periodic monitoring of the samples, with 24 h among measurements for a total period of 96 h. We can conclude that with increasing treatment time, acidification and electrical conductivity of water also increase. At this experiment range, storage temperature did not to exert significant influence on PAW physicochemical properties.