New insights into the relationship between anode material, supporting electrolyte and applied current density in anodic oxidation processes

Taking Acid orange-II (AO II) as pollutant model, the relationship between anode material, supporting electrolyte and applied current density was quantitatively investigated with the aid of a statistical tool, factorial design methodology. Boron-doped diamond (BDD), mixed metal oxide (MMO) and platinum (Pt) used as anode materials were examined with Na2SO4 and NaCl as supporting electrolytes. Analysis of result showed that AO II degradation efficiency was strongly linked to the anode-electrolyte-current interaction. The differing performances recorded in these anode/electrolyte systems could be explained in terms of oxygen evolution over-potential and electro-generated oxidants, and BDD/NaCl system outperformed other systems in terms of decolorization and mineralization efficiency. Further kinetic study indicated that the electrochemical degradation of AO II might follow different reaction orders, depending on the anode material and supporting electrolytes adopted. As a consequence, the new results recorded above were mainly consistent with the low electrolyte concentrations employed (1.0 ∼ 10.0 mM). Thus, we highlighted the importance of operating level selections in anodic oxidation processes, especially when different concentrations of supporting electrolytes were present in the reaction system.