Electrochemical degradation of acid orange 7 azo dye: process optimization, reaction kinetics, and mechanistic insights

The Acid Orange 7 (AO7) azo dye poses a serious problem due to its low environmental persistence and low treatment efficiency. Electrooxidation (EO) is a sustainable and highly efficient treatment technology for the effective oxidation of toxic AO7 azo dye. In this study, we investigated key parameters of the EO process for the oxidation of the AO7 azo dye, including current density (j), initial pH, initial AO7 concentration (Ci), and supporting electrolyte concentration (SEc). Under optimal operating conditions (anode/cathode = Pt/Gr-PtO2, j = 100 A/m2, pH = 3, Ci = 35 mg/L, and Na2SO4 = 50 mM), a removal efficiency of 79.0 % was achieved. Under the same conditions, the energy consumption and operating costs were calculated as 3.21 kWh/m3 (1471.82 kWh/kg AO7) and 0.57 $/m3 (11.96 $/kg AO7), respectively. Furthermore, the first-order model was evidenced by the determination of correlation coefficient values of (R2 = 0.984, AdjustedR2 = 0.963) and rate constant k = 0.00812 𝑚𝑖𝑛−1. These findings demonstrate that the EO process offers an effective and economical solution for removing AO7 azo dye, thereby supporting the potential of advanced oxidation technologies in environmental engineering.