Sono-advanced Fenton decolorization of azo dye Orange G: Analysis of synergistic effect and mechanisms

• A successful decolorization of Orange G was achieved by means of coupling of ultrasound and advanced Fenton process.
• The synergistic effect, mechanism of decolorization and main affecting factors were proposed.
• The input of ultrasound enhanced the activity of the Fe0/H2O2 system.
• Improving decolorization efficiency is possible via an optimal H2O2 dosage additive under an appropriate input method.

In this study, a successful decolorization of Orange G was achieved by means of coupling zero valent iron (ZVI), H2O2 and ultrasound (US) under acidic pH conditions. The synergistic effect and characterization of potential roles of the factors including ZVI, tert-Butanol as radical scavenger, dissolved ferrous ions and H2O2 generated from sonication were evaluated in this sono-advanced Fenton process (SAFP) system. A clear synergy was evident in terms of decolorization rate and the TOC removal as the input of US enhanced the activity of the Fe0/H2O2 system. The results suggested that the ZVI was potential replacement for the Fe2+ ion. This remarkable activity was attributed to the capacity of Fe2+ formed and reduction of sonic-dissolved Fe2+ concentration by the formation of {Fe·Fe2+}{Fe·Fe2+}. The modification of the condition of H2O2 addition such as the dosage and input method showed significant variations in terms of decolorization rate. This result indicated that the optimal external addition of H2O2 and input method is a limited factor of decolorization rate due to its comparatively insufficient generated by ultrasound.