Kinetic study of electro-Fenton oxidation of azo dyes on boron-doped diamond electrode

Abstract

The present work compares electrochemical degradation of red and blue azo textile dyes in single- and two-compartment electrochemical cells in the presence of Fenton reagent (Fe2+) and using a boron-doped diamond anode. Degradation of both dyes was related to the concentration of dye, applied current density and the concentration of FeSO4 catalyst. Complete colour removal and approximately 91% of organic matter oxidation was achieved in a two-compartment electrochemical cell at an applied current density of 20 mA·cm −2, pH of 3 and Fe2+ ion concentration of 0.02 mM. Higher current density and reaction time were required to achieve the same removals in a one-compartment electrochemical cell. Dye degradation kinetics as well as chemical oxygen demand removal rate were successfully modelled to pseudo first-order kinetics. The apparent first-order rate constants (k o) for degradation of red dye with an initial concentration of 20, 40 and 60 ppm were found to be 2.67±0.16, 2.19±0.09 and 1.5±0.03 min−1, and for blue dye at the same initial concentrations were 1.99±0.2, 0.95±0.02 and 0.71±0.030 min−1, respectively.