Ultrasonic Activation of Persulfate for the Removal of BPA in 20, 28, and 300 kHz Systems

The effect of ultrasound (US) on persulfate (PS) activation was investigated to determine whether acoustic cavitation can effectively induce PS activation for bisphenol A (BPA) degradation at 20, 28, and 300 kHz under various temperature conditions. The optimal liquid volume in the vessel was geometrically determined to be 400, 900, and 420 mL at 20, 28, and 300 kHz, respectively, using KI dosimetry and sonochemiluminescence image analysis. The pseudo-1st-order reaction kinetic constants in the only PS, only US, and US/PS processes at 20, 28, and 300 kHz were obtained under 5-10 ℃, 15-20 ℃, 25-30 ℃, 45-50 ℃, 55-60 ℃, and no temperature control conditions. No notable BPA degradation occurred at 5-10 ℃, 15-20 ℃, and 25-30 ℃ in the only PS processes for all frequencies. The highest sonochemical BPA degradation was obtained at 300 kHz, and much lower BPA degradation was observed at 45-50 ℃ and 55-60 ℃ for all frequencies in the only US processes. No notable enhancement of BPA degradation was observed at 5-10 ℃, 15-20 ℃, and 25-30 ℃ in the US/PS processes compared to the only US processes for all frequencies. At 20 kHz and temperatures between 55 and 60 ℃, the highest BPA degradation was obtained, with a synergistic effect of 171 %. However, the enhancement might be due to the instant or local temperature increase, and not due to acoustic cavitation. No notable PS activation by US irradiation was observed in the US/PS processes in this study. The profiles of the generated sulfate ion concentrations in the US/PS processes confirmed this. Some previous studies found high synergistic effects, whereas others have found low or no synergistic effects in US/PS processes.