Kinetic study of Acid Orange 7 degradation using plasmas in NaNO3 solution sustained by pulsed power

The kinetic study of the degradation of Acid Orange 7 (AO7), an anionic monoazo dye, using plasmas sustained by pulsed power in NaNO3 solution is performed. The correlation between the degradation reaction rate constants and the OH radical density are investigated. Conditions with the application of pulsed power with ton = 0.1-1 ms and a repetitive frequency of 100 Hz in 0.02 M NaNO3 solution are examined. The level of AO7 degradation is quantified using a UV-vis spectrometer. An OH radical molecular probe, disodium salt of terephthalic acid (NaTA), is used to estimate the relative OH radical densities. Results demonstrate that the degradation of AO7 follows first-order kinetics with respect to AO7 concentration with a reaction constant increases from 0.0023 to 0.0191 min−1 when ton increases from 0.1 to 1 ms. A nearly linear relationship between the relative OH radical densities and the AO7 degradation rate constants is observed, which shows that an increase in ton is able to simultaneously increase the OH radical formation and the degradation strongly suggests that AO7 degradation by OH radicals is the dominant process.