Ultrasonic Destruction of Acid Orange 7: Effect of Humic Acid, Surfactants and Complex Matrices.

The ultrasonic degradation at 600 kHz of an azo dye, acid orange 7 (AO7), in the presence of various dissolved natural organic matters (humic acid and surfactants) and in environmentally relevant matrices (natural water and seawater) was investigated. Additionally, the dependence of AO7 degradation on several operating parameters was clarified. The obtained results showed that ultrasound completely destroyed AO7 in 90 min of treatment but only 10% of TOC was removed after a long irradiation time. Investigations using the radical scavengers tert-butyl alcohol and KI revealed that AO7 degradation proceeds through radical reactions occurring at the bubble-liquid interface. AO7 conversion was strongly affected by the operating conditions. While the degradation of the dye was not affected by the presence of humic acid, it was impacted negatively by the presence of surfactants. Replacing deionized water by natural water and seawater as real environmental matrices did not affect the degradation of the dye.