A heterogeneous system using nanoscale zero-valent copper (nZVC) as an activating agent via ultrasound (US) accleration was employed for the degradation of azo dye acid orange 7 (AO7). The degradation rate of AO7 was obviously promoted by ultrasound irradiation as compared to the silent system from 28.83% to 87.39% at 5 min. Via the surface characteristics detected by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM), it was indicated ultrasound can accelerate the corrosion process of nZVC as more Cu+ was generated at the same reaction time. Via the particle size detected it was proved US has the ability to disperse the aggregates of nZVC. The addition of neocuproine hemihydrates (NCP) proved Cu+ is the primary activating agent and a large number of free radicals (OH• and SO4•) were detected by adding methyl alcohol (MA) and tert butyl alcohol (TBA). Then, the parameters investigated were the ultrasound power, acid concentration, and nZVC dosage. The results showed that the increase of ultrasound power has few impacts on AO7 degradation, and with the increase of acid concentration and nZVC dosage, the degradation rate of AO7 was enhanced remarkably. As seen from the above results, it is clear that ultrasound enhances the release of Cu+ to participate in the process of AO7 removal.

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