Plasma-liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on nonequilibrium plasmas.

The subject of this paper is the recently developed 2.45 GHz microwave micro torch, which produces a surface wave discharge operating at low power of 25 W. Microwave plasma is generated using surfatron resonator in pure argon and argon with admixtures (up to 1.7%) of nitrogen and oxygen at the gas flow rate of 3 Slm. Two different configurations are used-a standard one and one with an additional metallic plate at the surfatron resonator end limiting the surface wave propagation along the plasma. Plasma parameters like temperatures (rotational, vibrational, electron) along the plasma torch axis as well as distribution of selected active particles are determined. The numeric simulation of the discharge and its properties are included, too. Finally, surface temperature of the fresh pork skin affected by the active particles flow is determined using thermo camera images. The obtained results show applicability of this system for the surface treatment of biological objects and possibility to modify the torch conditions by molecular gases additions.

A dc excited discharge generated in bubbles (He, Ar, Air, N 2 ) in liquid phase is investigated in this work. Voltage/current characteristics and emission spectra of the discharge are recorded in the current range 10-30 mA. Electron density in the discharge is measured from Stark broadening of the H β line and is of the order of 2-6 × 10 20 m −3 , depending on the feed gas. Estimation of electron temperature is carried out based on the balance of charged particles. Gas temperature is estimated by the slope of the Boltzmann plot and by the simulation of the OH band with different T 1 rot , T 2 rot and T vib . Rotation temperature in the He discharge is 1200 K at I = 10 mA and linearly increases with current up to 1600 K. In the plasma of molecular gases the temperature is higher and almost constant at different currents. Chemical efficiency of the plasma is measured by the production of H 2 O 2 and by the destruction of Direct Blue 106 dye. The highest energy consumption of H 2 O 2 generation is achieved in the air discharge and it decreases up to 50% in the He plasma. Maximal efficiency of dye destruction is observed in the N 2 plasma characterized by an energy consumption of dye decomposition of 0.86 g kWh −1 .

The contribution gives results of hydrogen peroxide generation obtained in the DC diaphragm discharge in water solutions. Chemical active species, such as hydroxyl radicals and hydrogen peroxide are produced by the discharge. The dependencies of hydrogen peroxide concentration on high voltage (magnitude and polarity), material of electrodes and dielectric diaphragm are studied for one electrolyte (NaCl) used for initial solution conductivity. The used dielectric diaphragms differ in material and they have various thickness.PACS: 52.80.Wq

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A recently presented novel plasma source generating discharge in liquids based on the pin-hole discharge configuration is characterized in detail. The system is supplied by DC non-pulsing high voltage of both polarities in NaCl water solutions at a conductivity range of 100-15 000 μS/cm. The discharge itself shows self-pulsing operation. The discharge ignition is observed in micro bubbles by transient discharge followed by a glow discharge in positive polarity at lower conductivities propagating inside the bubbles. At high conductivities, the glow regime is particularly replaced by a more energetic sequence of transient discharges followed by a shorter glow mode operation. The transient regime probability and its intensity are higher in the negative discharge polarity. The transient discharge produces acoustic waves and shock waves, which are observed at the moment of the bubble cavitation. The average gas temperature of 700-1500 K was calculated from the lowest OH (A-X) 0-0 band transitions. The average electron concentrations of 10 20 -10 23 m −3 were calculated from H α and H β line profiles. Finally, the production of a chemically active species is determined by hydrogen peroxide energy yields related to the energy consumption of the whole interelectrode system. All these quantities are dependent on the solution conductivity, the discharge polarity, and the applied power.

Demand for food quality and extended freshness without the use of harmful chemicals has become a major topic over the last decade. New technologies are using UV light, strong electric field, ozone and other reactive agents to decontaminate food surfaces. The low-power non-equilibrium (cold) atmospheric pressure operating plasmas effectively combines all the qualities mentioned above and thus, due to their synergetic influence, promising results in fruit surface decontamination can be obtained. The present paper focuses on the applicability of the recently developed microwave surface wave sustained plasma torch for the treatment of selected small fruit. Optical emission spectroscopy is used for the determination of plasma active particles (radicals, UV light) and plasma parameters during the fruit treatment. The infrared camera images confirm low and fully applicable heating of the treated surface that ensures no fruit quality changes. The detailed study shows that the efficiency of the microbial decontamination of selected fruits naturally contaminated by microorganisms is strongly dependent on the fruit surface shape. The decontamination of the rough strawberry surface seems inefficient using the current configuration, but for smooth berries promising results were obtained. Finally, antioxidant activity measurements demonstrate no changes due to plasma treatment. The results confirm that the MW surface wave sustained discharge is applicable to fruit surface decontamination.