Abstract
In this work, the sonolytic degradation of an endocrine disrupting chemical, propylparaben (PPB), was carried out at 352kHz and 80W. The effects of initial substrate concentration and initial solution pH on the ultrasonic degradation of PPB were examined. Additionally, sonochemical degradation of substrate was investigated in natural water and seawater. The best performances were achieved in the pH range of 3-8, whereas the degradation rate decreased with increasing solution pH from 8 to 10.5. The obtained results showed an interesting effect of real water matrices. At a low concentration of PPB (5mg/L), an improvement in the degradation process was observed in natural matrices, while at higher concentrations of PPB (25100mg/L), degradation was slightly inhibited, particularly in natural water. At a medium concentration of PPB (10mg/L), similar degradation rates were observed for all the tested media. The Langmuir-type kinetic models fit well the substrate sonolytic degradation. A perfect representation of the experimental data of PPB sonochemical degradation at different initial concentrations in pure water was obtained using the Serpone et al.'s model. In real water matrices, an adequate description of the sonolytic destruction of PPB was attained by the Okitsu et al.'s equation. These results indicate that PPB undergoes degradation predominantly at the bubble/solution interface in natural water and seawater, whereas the sonolytic destruction of substrate in pure water is mainly achieved both at bubble/solution interface and in the bulk solution.