Synergistic effect of hydrogen peroxide production and sonochemiluminescence under dual frequency ultrasound irradiation

► The largest inhibition was observed under the dual irradiation of 28/28kHz. ► The largest enhancement was observed under the dual irradiation of 28/970kHz. ► H2O2 formation followed the order of 584/584>584/970>28/970≈28/584>28/28kHz. The synergistic effect of H2O2 production and sonochemiluminescence (SCL) was studied under both orthogonal and opposite dual irradiation at the frequencies of 28, 584 and 970kHz and at various acoustic powers. The largest reduction in H2O2 production was observed under opposite dual irradiation at a 28/28kHz frequency without considering the acoustic power levels. The largest enhancement was observed under dual irradiation at a frequency of 28/970kHz. This enhancement might be due to the increased number of bubbles that underwent violent collapse by low frequency ultrasound (28kHz). These results were also confirmed by observing the SCL. Under dual irradiation at relatively high frequencies (i.e., 584 and 970kHz), the synergistic effect was high at low acoustic power levels. However, the effect tended to decrease (to the equivalent of the calculation from the result of each single irradiation) with increasing acoustic power. Unlike dual irradiation coupled with a frequency of 28kHz, the inhibition effect was not observed under dual irradiation at relatively high frequencies. With respect to H2O2 production, the production rate constants of H2O2 followed the order of 584/584>584/970>28/970≈28/584>28/28kHz, which resulted from the fact that the production efficiency of H2O2 at an irradiation frequency of 584kHz was considerably higher than that at other frequencies.