This work shows results obtained in the electrochemical degradation of 50 mg dm(-3) Acid Orange II dye in the presence of different supporting electrolytes (sulfate, chloride, and their mixture of different proportion). Experiments have been performed with a batch recirculation cell containing boron-doped diamond anode and Pt cathode. The effect of operating parameters, such as treatment time (20-40 min), flow rate (400-600 ml min(-1)), applied current density (1.29-2.58 mA cm(-2)) and total concentration of supporting electrolytes (1.0-5.0 mM), on treatment performance is assessed implementing a factorial experimental design. The results obtained, demonstrate that chlorides play interesting and important roles during the electrolytic oxidations. Additionally, the evidences from UV-vis spectra are used to better clarify the different roles of operating variables recorded. (C) 2014 Elsevier B.V. All rights reserved.