Sonochemical enhancement of hydrogen peroxide production by inert glass beads and TiO2-coated glass beads in water

In this study, a series of experiments were carried out to determine the effects of ultrasound frequency at 28, 580, and 1000kHz on H₂O₂ production in the presence of both inert and TiO₂-coated glass beads. Several different sizes (no addition, 0.05, 0.1, 1, 2, 3, and 5mm) and amounts (no addition, 10, 25, 50, 100, and 200gL^-1) of inert glass beads were tested at a power density of 0.2WmL^-1. The production of H₂O₂ with a contact time of 60min at different frequencies follows the order: 580kHz (339μM/no addition-105μM/2mm)>1000kHz (208μM/no addition-4.0μM/1mm)>28kHz (71.2μM/0.1mm-18.5μM/no addition). For a constant glass-bead size of 0.1mm and at a frequency of 28kHz, the zero-order rate constant is highest in the presence of glass beads of the amount 10gL^-1 (3.3μM^-1min^-1), and it decreases significantly with increasing inert glass-bead amounts (2.7μM^-1min^-1/25gL^-1 to 0.45μM^-1min^-1/200gL^-1). The zero-order rate constant is the lowest (0.31μM^-1min^-1) with no addition of glass beads. Sonocatalysis at a low frequency of 28kHz with the addition of TiO₂-coated glass beads (5mm) of amount 100gL^-1 was significantly more effective (1540μM) than sonocatalysis carried out with no addition and inert glass beads (12-18μM) and those carried out at the high frequencies of 580kHz (33.4μM) and 1000kHz (8.77μM), with the other conditions remaining the same.