Enhancement of NOx production in water by combining an air bubble plasma jet and an external magnetic field

Production of NOx (NO2− + NO3−) in water with an air bubble discharge plasma jet under the influence of an external axial steady magnetic field was investigated experimentally. The gas phase plasma parameters, rotational (Tr), vibrational (Tv) and electronic excitation (Tx) temperatures, and electron density (ne), as well as the liquid phase pH and the concentrations of nitrite (NO2−) and nitrate (NO3−), were measured as a function of treatment time and magnetic field strength. It was found that Tr, Tv, Tx, and ne slightly increased as a function of magnetic field strength in the gas phase plasma. The pH decreased both with treatment time and magnetic field strength. In the maximum field strength of 290 mT, the concentrations of NO2− and NO3− were ∼82% and ∼74%, respectively, greater than with B=0. With B=290 mT, the energy cost for producing NOx was ∼78% lower than with B=0. The energy cost may likely be reduced due to decreasing radial diffusion loss of charged species in the discharge with increasing magnetic field strength.