Optimization of reactive blue 19 degradation by non-thermal plasma: evaluating the combined influence of conductivity and operational parameters via response surface methodology

This study examines the impact of multiple operational parameters on the degradation efficiency of the reactive blue 19 (RB19) dye during non-thermal plasma treatment. Electrical conductivity was examined simultaneously with other parameters, an aspect rarely addressed in previous plasma-based studies. Response surface methodology (RSM) was employed to determine the optimal conditions for dye degradation, encompassing dye concentration, applied voltage, pH, electrical conductivity, and solution volume. The results showed that a dye concentration of 30 mg/L, an applied voltage of 50 kV, a pH of 4, a conductivity of 0.045 mS/cm, and a solution volume of 10 mL achieved the highest degradation efficiency of approximately 100%. Kinetic analysis verified that RB19 degradation adheres to a second-order kinetic model, with notable interactions observed among the operational parameters. The energy efficiency for RB19 dye degradation decreases with increasing cold plasma treatment time; at a constant voltage of 50 kV, it decreases by 47% as treatment time increases from 3 to 6 minutes. Testing tert-butanol (TBA) and p-benzoquinone (BQ) scavengers to evaluate the effectiveness of OH • and O 2 •- radicals, it was concluded that the hydroxyl radical has a greater effect on the degradation of RB19. COD and TOC reductions of 50% and 29%, respectively, during the plasma oxidation process indicate that, beyond RB19 dye removal, partial mineralization of organic content was achieved. • The effectiveness of the plasma dielectric barrier discharge process for the purification of RB19 dye solution in an aqueous medium was investigated. • The effect of parameters such as pH, initial concentration of RB 19 dye, electrical conductivity of the solution, voltage, and sample volume has been evaluated. • The most optimal conditions are pH = 4, voltage = 50, and initial dye concentration of RB 19 = 30 mg/l in the plasma dielectric barrier discharge process. • Cold plasma technology can efficiently treat dye wastewater.