Abstract

Plasma-activated water (PAW) is increasingly used as an antimicrobial washing agent in biomedical and agricultural industries. In this study, an industrial prototype plasma jet utilizing an adjustable 500 W radio frequency (RF) power supply was developed for generating reactive species in water. A laboratory-scale plasma jet was firstly set up to test the effect of plasma on water. After activating 100 mL tap water by air plasma for 60 min, over 500 mg/L nitrate (NO3^–) and 5 mg/L nitrite NO2⁻ were obtained consistent with the increased electrical conductance and the pH reduction. For the industrial prototype, 60 ppm of hydrogen peroxide (H2O2) was obtained from the activation of 300 mL water for 120 min. Substituting air by argon drastically increased the H2O2 concentration. Although the water substantially evaporated during the plasma activation in vacuum, the low-pressure chamber is advantageous in enhancing H2O2 generation. With the water circulation, the PAW can continuously be produced with sufficient reactive species using a shorter activation time. The pressure and the type of gas, as well as the frequency and power in plasma generation, are all adjustable. Cost-effective PAW for industrial sanitization and other research purposes, including stimulation of seed germination and plant growth, can be generated by this flexible system.