Mechanistic study on the combination of ultrasound and peroxymonosulfate for the decomposition of endocrine disrupting compounds

The effectiveness and synergistic mechanisms of combining ultrasonic process (US) with peroxymonosulfate (PMS) were investigated using Bisphenol A (BPA) and Dimethyl Phthalate (DMP) as the model pollutants. Synergy between US and PMS improved the degradation of target pollutants, and PMS was found to play a dual role. The optimum dosage of PMS and the extent of efficiency promotion were found to depend on not only the ultrasonic frequency but also on the hydrophobicity of target pollutants. The scavenger quenching experiments and electron paramagnetic resonance analysis indicated that center dot OH was responsible for DMP degradation in both US and US/PMS processes. The chemical probe experiments also proved that activation of PMS could increase the production of center dot OH while excess PMS consumed the available radicals. Furthermore, it was found for the first time that the constituent salts of KHSO4 and K2SO4 in the commercial Oxone also made considerable influence on US/PMS process. It was also found that the combination of US and PMS showed more pronounced synergistic effect for treating DMP at lower concentrations. Higher efficiency was achieved at more acidic condition and similar efficiencies were obtained at pH range of 5.1 similar to 8.12. DMP degradation pathways were found to be the center dot OH addition to the aromatic ring and hydrogen absorption at the aliphatic chains with and without the presence of PMS, but much better mineralization capability was obtained in the presence of PMS than ultrasonic degradation alone.