Degradation and Detoxification of Remazol Blue Contaminants as a Model Textile Effluent via Advanced Nonthermal Plasma Oxidation Processes

This study explores the degradation of the reactive Remazol Blue RR (RBRR) as a model textile effluent upon its exposure to non-thermal atmospheric pressure plasma. An extensive comparative study of different combinations of the following plasma/solution treatment environments was conducted: 1) Ar plasma jet (Ar-PJ) alone; 2) Ar/O
₂
and Ar/N
₂
plasmas; 3) Ar plasma with O
₂
or N
₂
injected (INJ) in the bulk of the Ar plasma afterglow; and 4) Ar plasma with O
₂
or N
₂
bubbling (BB) in the RBRR solution. In all conditions, plasma treatment was carried out at a fixed applied voltage of 31 kV and treatment time of 10 min. The degradation efficiency of RBRR in the different plasma-treated solutions was evaluated using UV–visible spectroscopy. Optical emission spectroscopy (OES) was used to examine the generation of excited species in plasma during the degradation processes. Moreover, the concentration of plasma-induced reactive hydroxyl radicals (OH
^•
) and hydrogen peroxide (H
₂
O
₂
) was determined spectroscopically. To further corroborate the results, the pH, conductivity, and total organic carbon (TOC) of the plasma-treated RBRR solutions were assessed. Overall, the results showed that the highest degradation efficiency (45%) was obtained upon exposure of RBRR aqueous solution to Ar plasma with N
₂
bubbling in the solution. The non-toxic nature of all plasma-treated solutions was confirmed by non-inhibition of bacterial growth (
Escherichia coli
and
Staphylococcus aureus
). Overall, plasma treatment in general and Ar plasma accompanied with N
₂
bubbling in particular constitute an eco-friendly and very promising techniques to degrade/decolorize textile effluent.