Comparative depollution of Methyl Orange aqueous solutions by electrochemical incineration using TiRuSnO2, BDD and PbO2 as high oxidation power anodes

The electrocatalytic properties of the Ti-Ru-Sn ternary oxide anode (TiRuSnO2), lead dioxide (PbO2) and boron-doped diamond (BDD) anodes were compared for the electrochemical incineration of Methyl Orange (MO), an azo dye, using an electrolytic flow cell with parallel-plate electrodes. The effects of several operating parameters such as current density, hydrodynamic conditions and initial dye concentration on the degradation rate, mineralization and current efficiency were determined. The experimental data indicate that, on PbO2 and BDD anodes, MO was completely oxidized by reaction with hydroxyl radicals electrogenerated from water discharge and the removal rate was favored by high flow rates, meaning that the oxidation was a diffusion-controlled process. It was also observed that the Methyl Orange decay followed a pseudo-first-order kinetics. After 3 h the BDD and PbO2 anodes lead to almost complete MO degradation with comparable removal rate, but BDD enables higher COD removal than PbO2, with 96% and 79% of mineralization, respectively. On the contrary, on DSA only a partial oxidation of MO was obtained corresponding to 75% degradation of the initial substrate with 60% mineralization.