Influence of Peroxynitrite in Gliding Arc Discharge Treatment of Alizarin Red S and Postdischarge Effects

The gliding arc discharge is a cheap and efficient nonthermal plasma technique able to degrade organic compounds dispersed in water at atmospheric pressure. Alizarin Red Sulfonate (ARS) is selected as a stable quinonic dye. Exposure of the dye solution to the discharge in a batch reactor induces two successive reaction steps according to the treatment conditions. Direct exposure of the solution to the discharge induces simultaneous bleaching and COD evolution. In postdischarge conditions, that is, after the discharge is switched off, the reactions keep on developing. This study thus underlines two key features: the ability of glidarc discharges to degrade recalcitrant molecules and the low cost of the process which requires short exposure times. A model mechanism involves peroxynitrite as a likely active species formed in the discharge and involved in postdischarge phenomena in aqueous solutions and suggests short exposure times and much longer postdischarge times for optimized pollutant abatement.