Textile wastewater treatment by underwater parallel-multi-tube air discharge plasma jet.

• 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]