Electrochemical degradation of a real textile effluent using boron-doped diamond or β-PbO 2 as anode

Abstract

Constant current electrolyses are carried out in a filter-press reactor using a boron-doped diamond (Nb/BDD) or a Ti–Pt/β-PbO 2 anode, varying current density ( j) and temperature. The degradation of the real textile effluent is followed by its decolorization and chemical oxygen demand ( COD) abatement. The effect of adding NaCl (1.5 g L −1) on the degradation of the effluent is also investigated. The Nb/BDD anode yields much higher decolorization (attaining the DFZ limit) and COD-abatement rates than the Ti–Pt/β-PbO 2 anode, at any experimental condition. The best conditions are j = 5 mA cm −2 and 55 °C, for the system's optimized hydrodynamic conditions. The addition of chloride ions significantly increases the decolorization rate; thus a decrease of more than 90% of the effluent relative absorbance is attained using an applied electric charge per unit volume of the electrolyzed effluent ( Q ap) of only about 2 kA h m −3. Practically total abatement of the effluent COD is attained with the Nb/BDD anode using a Q ap value of only 7 kA h m −3, with an energy consumption of about 30 kW h m −3. This result allows to conclude that the Nb/BDD electrode might be an excellent option for the remediation of textile effluents.