(254bc) Water Acidification By Atmospheric Pressure Microplasmas Operated in Air

Authors: 
Lin, C. C., National Taiwan University
Hsu, C. (., National Taiwan University
Water acidification by plasmas is an important phenomenon that the pH value of water decreases upon plasma treatment. This is of great interest in plasma for biomedical application. It allows for decrease in pH without the need of chemicals. This work presents the acidification of water by atmospheric pressure microplasmas, which are plasmas with geometric dimensions less than 1 mm operated at one atmosphere. The microplasma used in this work is a dielectric-barrier-discharge-type plasma operated in air. The microplasma generation device (MGD) is made of double-sided printed circuit board with patterns defined by the toner transfer method, which is a low-cost, customized, and easy-to-fabricate process. It is generally accepted that water acidification by air plasma is a result of dissolved of NO and/or NO2 gases generated in plasma. The acidification rate is greatly influenced by the generation, transport, and dissolution of NO and/or NO2. Plasma operating conditions influence the generation rate, and plasma-induced flow (for example, ionic wind) can be an important factor that influences the transport and hence the dissolution. Preliminary studies are performed using AC power with an operating voltage of 2-2.5 kVp-p and a frequency of 20 kHz to ignite plasma on the MGD. When 0.002 mL of DI water droplet is sit adjacent to the plasma generation electrode of the MGD with a distance of 2 mm, the pH value decreases from 7 to 3 in 80 sec. By changing the plasma-droplet distance (2 mm-10 mm), MGD electrode geometry, and the plasma voltage, the acidification rate can be tailored, and desired pH valued can be obtained. In this work, we will test the influence of electrode arrangements and operating conditions on the acidification rate.