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 (H2O2) 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.