Enhanced sonochemical degradation of azure B dye by the electroFenton process

The degradation of azure B dye (C15H16ClN3S; AB) has been studied by Fenton, sonolysis and sono-electroFenton processes employing ultrasound at 23 kHz and the electrogeneration of H2O2 at the reticulated vitreous carbon electrode. It was found that the dye degradation followed apparent first-order kinetics in all the degradation processes tested. The rate constant was affected by both the pH of the solution and initial concentration of Fe2+, with the highest degradation obtained at pH between 2.6 and 3. The first-order rate constant decreased in the following order: sono-electroFenton > Fenton > sonolysis. The rate constant for AB degradation by sono-electroFenton is ∼10-fold that of sonolysis and ∼2-fold the one obtained by Fenton under silent conditions. The chemical oxygen demand was abated ∼68% and ∼85% by Fenton and sono-electroFenton respectively, achieving AB concentration removal over 90% with both processes.

► Sono-electroFenton enables high COD removal and azure B degradation under mild conditions.
► Sonolysis and Fenton reagent, with H2O2 electrogeneration, enhanced azure B degradation.
► Sono-electroFenton reaction produced a colorless solution with 85% of COD removal after 60 min of reaction.
► H2O2 electrogenerated combined with ultrasound represents an environmental friendly alternative for organic pollutant degradation.