Synergetic degradation of benzotriazole by ultraviolet and ultrasound irradiation

The sonophotolytic degradation of benzotriazole (BTri) in aqueous solution was investigated in this study by combining ultrasound (20 kHz) and ultraviolet irradiation (λ = 254 nm). The ultrasound-caused pyrolysis was found to effectively promote the photochemical degradation of BTri and the corresponding synergetic effects were studied under different reaction conditions. Lower pH and higher ultrasonic power enhanced the BTri removal. However, the synergy between UV and US was much stronger at higher pH. The 15 min BTri removal at pH 3 was about four times of that at pH 9, while the synergy at pH 3 was nearly one-third of that at pH 9. The BTri removal increased with reaction time but the synergy decreased. Kinetics studies revealed that the degradation process followed the pseudo-first-order model.