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We report the generation of radical droplets activated by an underwater electrical discharge and the sterilization of bacteria cells by spraying the radical droplets to open air. The plasma formed by electrical discharge in a narrow dielectric capillary tube produces atomic oxygen, atomic hydrogen, and hydroxyl radicals from the dissociation of water vapor, which is achieved through Joule heating in the narrow capillary tube. The capillary discharge electrode is placed in a water flow line, and the plasma-activated water is sprayed as fine droplets through a nozzle at 0.08 L/min. In a bactericidal test, the droplets show a sterilization effect of more than 99.99% after an exposure time of 3 h. The proposed radical droplet generator may also be useful for the elimination of airborne microorganisms. [ABSTRACT FROM AUTHOR]

In this paper, we report on the mass production, characteristics and application of a hydrogenated TiO 2 photocatalyst (H-TiO 2 ) with high reactivity under solar light irradiation. The H-TiO 2 photocatalyst has been prepared by simple sol-gel method/underwater discharge plasma treatment at room temperature and atmospheric pressure. The optical absorption spectrum of TiO 2 can be extended from the ultraviolet (UV) into the visible range by changing the surface properties. The crystallinity, hydrogenation and porosity of TiO 2 can be greatly enhanced within 90 s through underwater discharge plasma, using amorphous TiO 2 (as-synthesized TiO 2 , a-TiO 2 ) as the precursor. The resultant H-TiO 2 showed high bicrystalline (anatase/brookite phases) and a large surface area (267.5 m 2 /g), thus improving photocatalytic activity. We have demonstrated that H-TiO 2 showed significant photocatalytic efficiencies for degradation of reactive black 5, rhodamine B, and phenol under solar light irradiation, up to 10 times higher than those of commercial TiO 2 and a-TiO 2 , leading to complete water purification. Interestingly, the H-TiO 2 photocatalyst also exhibited strong antimicrobial activities against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus under solar light irradiation, up to 5-times greater than those of commercial TiO 2 and a-TiO 2 . Given that H-TiO 2 can be mass produced and easily processed by underwater discharge plasma, we expect this plasma technology may find important environmental and medical applications. [ABSTRACT FROM AUTHOR]

• Acidity of wastewater is increasing with increasing plasma treatment duration. • The decreasing concentrations of O 3 , H 2 O 2 and N O 3 - suggest that they participate in the dissociation processes of textile dyes. • UV–vis spectra indicate the increase in decolorization efficiencies with increasing treatment durations. • Amines and alkynes are likely to be produced through oxidative processes of azo-bonds and nitrogen containing functional groups with the interactions of O 3 and O H radical. • FTIR spectra reveal the presence of functional groups that are likely to be produced due to dissociation by plasma treatments. • A fraction of organic nitrogen can be converted to nitrites through oxidation process. Textile wastewaters (WW) as released from textile industries damage aquatic environment and thereby create threat to plants and animals. To overcome the problems associated with wastewaters, the plasma technology can be an alternative approach for the reduction of effluents dissolved in textile WWs. In this present study, the degradation of textile dye model WWs is carried out using underwater parallel-multi-tube atmospheric pressure air discharge plasma jet. The investigation reveals that: p H is decreased, while electrical conductivity (E C) is increased in the deionized (DI) waters and model WWs with increasing plasma treatment duration. The Concentrations of O 3 , H 2 O 2 and N O 3 - in model WWs are decreased compared to that of DI water with treatment duration, but N O 2 - is increased. The decrease in O 3 , H 2 O 2 and N O 3 - suggest that they participate in the dissociation processes of textile dyes. UV–vis spectroscopic measurements show that almost 70 % of dyes were degraded within 10 min of treatments but the remaining 30 % was taken a longer time. FTIR spectroscopic measurements reveal that the amines and alkynes are likely to be produced through oxidative processes of azo-bonds and nitrogen containing functional groups with the interactions of O 3 and O H radical. A fraction of organic nitrogen can be converted to nitrites through oxidation for which the concentration of nitrite is increasing with treatment duration. The proposed environment friendly plasma technology can alternatively be adapted to the reduction of effluents as dissolve in textile WW. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the enhancement of membrane penetrability by means of a discharge in water. The system is composed of an underwater capillary discharge to produce the various plasma species containing OH, O, H, Na+, Cl−, ClO−, Cl2, etc., and a membrane for water filtration. We investigate the capillary discharge membrane system to treat the microorganisms and particles in seawater simultaneously. We also report the effects of the underwater capillary discharge on the membrane flux. The plasma by-products also depend on the discharge polarity significantly. Eventually, we expect that the hybrid system may be promising tool for sterilization of microorganisms and removal of particles in water. [Copyright &y& Elsevier]