The role of metals in the deposition of long-lived reactive oxygen and nitrogen species into the plasma-activated liquids

The work investigates the role of metals on the formation and stability of reactive oxygen and nitrogen species (RONS) in liquids treated with a surface-wave microwave discharge. It is demonstrated that the high reduction potential metals can quasi-neutralize the acidification induced by the plasma treatment, and thus reduce the rate of the NO2-+H2O2+H+-> products reaction. As a consequence, while in the acidified plasma-activated water the NO2- production vanishes with increase in the treatment time, the addition of metals enhances the NO2- production. The RONS concentrations are quasi-stable for several weeks when pH is higher than 5.5, which can be achieved in a wide range of treatment conditions with the use of Mg powder, and at relatively shorter treatments with the usage of Zn.

Automated summary

The study investigates the impact of metals on the formation and stability of reactive oxygen and nitrogen species (RONS) in liquids treated with a surface-wave microwave discharge. It is shown that metals with high reduction potential can counteract the acidification caused by plasma treatment, leading to a decrease in the reaction rate of NO2- + H2O2 + H+ -> products. Consequently, the addition of metals enhances the production of NO2- in acidified plasma-activated water. The concentrations of RONS remain relatively stable for weeks when the pH is above 5.5, which can be achieved by using Mg powder or shorter treatment times with the use of Zn.