Modeling of plasma-liquid interactions

Plasma-liquid interactions are important for various applications, and therefore, a good understanding of the plasma-liquid interaction mechanisms is indispensable. This can be obtained by computer modeling. Different modeling approaches can be used, which all have their own advantages and drawbacks. For instance, a 0D chemical kinetics model cannot describe spatial behavior, but because of its limited calculation time, it can include a rich plasma chemistry. Vice versa, more-dimensional fluid dynamics models can account for gas and liquid flow behavior, but are more time-consuming, and therefore typically consider only a limited chemistry.

For this reason, we developed a combination of a 0D chemical kinetics model and a 2D fluid dynamics model for a plasma jet interacting with liquid water. We this model we can study the gas and liquid flow behavior, and the transport and chemical reactions of reactive oxygen and nitrogen species (RONS) both in gas and liquid phase. We calculate the species concentrations, both during and after plasma treatment, to elucidate the chemical pathways and the lifetime of the various RONS in solution.

In this talk I will show the gas and liquid flow profiles, and species concentration profiles, both in the gas and liquid phase. The latter are highly dictated by the Henry’s constants of the species. I will also illustrate how the species concentrations in the liquid vary as function of time, during and after plasma treatment, and explain this behavior based on the liquid phase chemistry and the Henry’s constants. After plasma treatment, the concentrations of most short-lived RONS drop within 10 seconds. The O₃ concentration drops linearly, and it takes ca. 50 seconds to disappear, explained by the low Henry’s constant, causing a continuous flow of O₃ back to the gas phase after plasma treatment. Only H₂O₂, HNO₂ and HNO₃ are stable in the liquid after plasma treatment, also confirmed by experiments.