Electrochemical degradation of the Acid Blue 62 dye on a β-PbO2 anode assessed by the response surface methodology

The electrochemical degradation of the anthraquinonic dye Acid Blue 62 in a filter-press reactor on a Ti/Pt/beta-PbO2 anode was investigated using the response surface methodology with the variables: current density, pH, [NaCl], and temperature. The system's modeling was carried out with the charge required for 90% decolorization (Q (90)) and the chemical oxygen demand removal percentage after a 30 min electrolysis (COD (30)), with good correlations between predicted and observed values. Best conditions for decolorization were attained in acidic solutions (pH = 4) with medium to high [NaCl] (1.0-2.0 g L-1) and lower temperature due to the prevalent oxidant species HOCl and Cl-2. Optimal conditions for COD (30) removal were attained at high current densities in pH > 5 solutions with high [NaCl], when the prevalent oxidant species are HOCl and OCl-. The lowest charge per unit volume of the electrolyzed solution necessary for total mineralization was attained at pH 11.