Sonophotocatalytic Destruction of Chloroform: Comparison of Processes and Synergistic Effects

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This study compared ultrasound, ultraviolet, and catalyst processes and evaluated their respective synergistic effects. The ultrasonic frequencies in this study used 35, 283, 450, and 935 kHz, whereas short wavelength ultraviolet lamp (UVC) was used. The dose of TiO<sub>2</sub> was 0.3 g/L. The degradation rate constants for the sonophotolytic processes were $(4.2{\mbox{--}}8.7)\times 10^{-3}$ min-1, nearly the same for the sonolytic processes. The value of the synergistic effect was 1.07. The main mechanism of this process was pyrolysis by ultrasound. The ultraviolet provided another mechanism as using oxidation by hydroxyl radicals, but the enhancement was not significant. The rate constants of sonophotocatalytic processes were $(48.1{\mbox{--}}64.6)\times 10^{-3}$ min-1. The calculated value of synergistic effect was 1.54. In this process, the main mechanism for degradation was oxidation by hydroxyl radicals on the surface of TiO<sub>2</sub>. The roles of the ultrasound were the dispersion of catalyst and mass transport of pollutant to the surface of the catalyst.
2011-07-25