Some approximations on the effect of the supporting electrolyte towards electrochemical advanced oxidation degradation of Reactive Orange 84 (RO84)

In this paper, some advanced oxidation electrochemical processes such as anodic oxidation (AO), electro-Fenton (EF), and photoelectro-Fenton (PEF) to carry out the degradation of the azo dye Reactive Orange 84 (RO84) are presented. For this, boron-doped diamond (BDD) electrodes were used, and different configurations were taken in a stirred tank cell, like BDD/graphite and BDD/BDD. The effect of different operating parameters on the discoloration process was evaluated, including the concentration of the supporting electrolyte, namely 50 and 75 mM of Na₂SO₄, along with 50 mM NaCl and mixtures of Na₂SO₄ + 25 mM NaCl. The effect of the applied current density at 25, 50, and 100 mA cm⁻² over the loss of color was also analyzed using initial RO84 concentrations of 100 and 200 mg/L. The production of free radicals was evaluated in the bulk solution. The decrease in chemical oxygen demand (COD) was determined and the evolution of oxalic acid, a nontoxic, short-chain carboxylic acid was quantified as a final product of all treatments by using ion-exclusion high-performance liquid chromatography.