Plasma acid and its applications

Summary form only given. Non-thermal atmospheric pressure plasma applied to the surface of water can oxidize organic molecules in the solution and kill bacteria in it. Ozonation of water produce a solution that retains its oxidation potential for several minutes. We show that direct exposure of deionized water not only to ozone but to other neutral and charged species produced in plasma creates a strong oxidizer in this water which, for the lack of a better term, we can call plasma acid. Plasma acid can remain stable for much longer time than ozonated water and its oxidizing power may be linked to the significant lowering of its pH. We report experiments that demonstrate plasma acid´s stability. We also show that observed pH of as low as 2.0 cannot be completely accounted for by the production of nitric acid; and that the conjugate base derived from superoxide is at least partly responsible for both, lowering of the pH and increase in the oxidizing power of the solution. Existence of a stable oxidizer created using plasma treatment of pure water not only raises interesting scientific questions and possibilities, but is likely to find many applications in situations where “on the spot” plasma treatment may be difficult to achieve.