G = superficial gas rate, 1b.I (hr.)h, = operating holdup, cu.ft./cu.ft. li, = static holdup, cu.ft.1cu.ft. ht = total holdup, cu.ft./cu.ft. k, = gas-phase mass transfer coefficient, lb. moles/ (hr.) (sq. ft.) (atm.)

By application of the kinetic theory, with several simplifying assumptions, the previous equation of Buddenberg and the author has been modified to give a general equation for viscosity as a function of molecular weights and viscosities of the pure components of the mixture. Agreement of the equation with experimental data is demonstrated for a number of highly irregular binary gas systems and mixtures of three to seven components.

Water disinfection by indirect plasma treatment was investigated using a surface dielectric barrier discharge (DBD). Liquid was neither part of the discharge electrode configuration nor stirred during plasma treatment. High concentrations (106–108 cfu·mL−1) of Escherichia coli and Staphylococcus aureus have been completely inactivated within 5–15 min, depending on liquid sample volume. Inactivation occurred in non‐buffered liquids, only, where pH decrease was found. Measurements of pH, nitrate, and nitrite concentrations after DBD plasma or NO gas treatment lead to the conclusion that nitric acid formation from plasma‐generated reactive nitrogen species are the main source of liquid acidification. Incubation of bacteria in nitric acid alone did not result in comparable inactivation effects. Increase of H2O2 concentration was found as a result of plasma treatment of liquids but not after treatment by NO gas. Therefore, synergistic action of both reactive oxygen and nitrogen species are discussed to be responsible for antimicrobial plasma effects.

No abstract

Treatment of aqueous liquids by surface‐DBD in atmospheric air resulted in bactericidal activity of the liquid itself. A 7 min treatment of sodium chloride (NaCl) solution and its immediate addition to Escherichia coli resulted in a complete bacteria inactivation (≥7 log) after 15 min exposure time. With a 30 min delay between plasma treatment of liquid and its addition to the bacteria, bactericidal effect was reduced but still detectable. Nitrate (${\rm NO}_{2}^{{-} } $), nitrite (${\rm NO}_{2}^{{-} } $), and hydrogen peroxide (H2O2), respectively, as well as strong acidification are detected in plasma treated liquids and can explain this bactericidal activity partially. Combination of 1.5 mg · L−1 ${\rm NO}_{2}^{{-} } $ and 2.5 mg · L−1 H2O2 at pH 3 results in maximum 3.5 log E. coli reduction within 60 min. Plasma diagnostics and liquid analytics are combined with theoretical considerations to focus possible reaction channels of plasma–water interactions. Using FT‐IR, stable molecules like nitrous oxide (N2O), ozone (O3), carbon dioxide (CO2), and traces of nitric acid (HNO3) and/or peroxynitrous acid (ONOOH) were measured. Reactions of these molecules from the plasma/gas phase with the aqueous liquid can result in acidification and generation of H2O2, ${\rm NO}_{2}^{{-} } $, and ${\rm NO}_{3}^{{-} } $ or peroxynitrite (ONOO−), respectively, via reactions which are associated with the occurrence of several more or less stable but biologically active chemical intermediates like ${\rm NO}^{ \bullet } $ or nitrogen dioxide (${\rm NO}_{2}^{ \bullet } $). On the other hand, H2O2, ${\rm NO}_{2}^{{-} } $, and ${\rm NO}_{3}^{{-} } $/ONOO− could serve as starting reaction partners to generate ${\rm NO}^{ \bullet } $, ${\rm HO}^{ \bullet } $, ${\rm NO}_{2}^{ \bullet } $, or hydroxyl radicals (${\rm HOO}^{ \bullet } $) in the liquid.