On the performances of lead dioxide and boron-doped diamond electrodes in the anodic oxidation of simulated wastewater containing the Reactive Orange 16 dye

The performances of the Ti–Pt/β-PbO2 and boron-doped diamond (BDD) electrodes in the electrooxidation of simulated wastewaters containing 85 mg L−1 of the Reactive Orange 16 dye were investigated using a filter-press reactor. The electrolyses were carried out at the flow rate of 7 L min−1, at different current densities (10–70 mA cm−2), and in the absence or presence of chloride ions (10–70 mM NaCl). In the absence of NaCl, total decolourisation of the simulated dye wastewater was attained independently of the electrode used. However, the performance of the BDD electrode was better than that of the Ti–Pt/β-PbO2 electrode; the total decolourisations were achieved by applying only 1.0 A h L−1 and 2.0 A h L−1, respectively. In the presence of NaCl, with the electrogeneration of active chlorine, the times needed for total colour removal were markedly decreased; the addition of 50 mM Cl− or 35 mM Cl− (for Ti–Pt/β-PbO2 or BDD, respectively) to the supporting electrolyte led to a 90% decrease of these times (at 50 mA cm−2). On the other hand, total mineralization of the dye in the presence of NaCl was attained only when using the BDD electrode (for 1.0 A h L−1); for the Ti–Pt/β-PbO2 electrode, a maximum mineralization of 85% was attained (for 2.0 A h L−1). For total decolourisation of the simulated dye wastewater, the energy consumption per unit mass of dye oxidized was only 4.4 kWh kg−1 or 1.9 kWh kg−1 using the Ti–Pt/β-PbO2 or BDD electrode, respectively. Clearly the BDD electrode proved to be the best anode for the electrooxidative degradation of the dye, either in the presence or absence of chloride ions.