3. Degradation and Discoloration of Textile Dyes Using Gliding Arc Plasma Combined with Fenton Catalysis

Degradation and discoloration of three kinds of representative textile dyes [Alphazurine A, Acid Orange II (AOII), and Acid Anthraquinone Blue (AAB)] and their mixture were investigated using the gliding arc discharge plasma, which produces reactive species, such as OH, NO, and H₂O₂, and other excited state molecules formed in the discharge and induces strong oxidizing effects on the target solution. The influence of zerovalent iron (ZVI) as Fenton catalysis on the efficiency of treatment was also studied. The acidic environment created by gliding arc discharge (GAD) is the cause of ZVI to release ferrous ions that act as a catalyst for decomposing hydrogen peroxide emitted by GAD. We treated the dyes with the UV-Vis analyses and chemical oxygen demand (COD) measurements to confirm the discoloration and degradation of the dyes, respectively. It has been observed that the discoloration ratios are almost complete (i.e., 96.55% for AA, 94.66% for AOII, and 89.69% for AAB). The discoloration and degradation for mixed dyes with ZVI follow pseudo-first-order kinetics. The kinetic constants of bleaching are 0.0301 and 0.0385 min⁻¹ at 483 and 637 nm, respectively, and of degradation is 0.0101 min⁻¹, which is much higher than 0.0019 min⁻¹, the kinetic of mixed dyes without ZVI. The degradation efficiency for the mixed solution with an addition of ZVI turns out to be 44.18% higher than that without. All these abovementioned points mean that GAD combined with ZVI can be a promising technology in the area of textile dye wastewater treatment (Li in Study on the treatment of dye wastewater in a gliding arc discharge plasma reactor. Yat-sen University, 2013, [1]).