Two different Ti/Pt-Ir materials (commercial and home made) and Ti/PdO + Co3O4 were investigated for their electrocatalytic properties versus Cl-2 evolution reaction. The materials were used in a batch electrochemical reactor to treat biologically recalcitrant di-azo compound. An electrochemically driven oxidation, mediated by a Cl-2/Cl-couple, proved efficient for destruction of this complex organic molecule, causing cleavage of the conjugated double bonds and destruction of unsatured bonds. Both Ti/Pt-Ir materials performed well; lower kinetics obtained with the Ti/PdO + Co3O4 anode was caused by adsorption of the model compound, evidenced in preliminary voltammetric measurements. The dye oxidation reaction followed the second order kinetics with partial orders in the model compound and (time varying) chlorine concentrations equal to one. Specific energy consumption of 3.12 kWh m(-3) proved the process more economic than the homogeneous phase oxidation. (c) 2004 Elsevier B.V. All rights reserved.