Sonochemical degradation of PAH in aqueous solution. Part I: monocomponent PAH solution.
The sonolysis of selected monocomponent PAH aqueous solution is studied at 20 and 506 kHz in the microg l(-1) range. The highest activity observed at 506 kHz, compared to 20 kHz, is tentatively explained by examination of the physical characteristics of bubbles (size and life-time) as well as by the calculation of the number of bubble at both frequency (5 x 10(3)bubbles l(-1) at 20 kHz and 4.5 x 10(9)bubbles l(-1) at 506 kHz). It is demonstrated that the main mechanism of sonodegradation is the pyrolysis of PAHs in the heart of the cavitation bubbles, and that a possible PAH oxidation by means of HO degrees appears as a minor way, since gaseous byproducts such as CO, CO2, C2H2 and CH4 have been detected. Correlations have been found by examination of kinetic variations in terms of the physical-chemical properties of PAHs. The rate constants of PAH degradation increase when the water solubility, the vapour pressure and the Henry's law constant increase.
David
Bernard
B
Université de Savoie, Polytech'Savoie, Laboratoire de Chimie Moléculaire et Environnement, 73376 Le Bourget du Lac Cedex, France. bernard.david@univ-savoie.fr
D000465:Algorithms; D002849:Chromatography, Gas; D005740:Gases / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D010084:Oxidation-Reduction; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry* / Q000528:radiation effects*; D012996:Solutions; D014465:Ultrasonics; D014867:Water
D005740:Gases; D011084:Polycyclic Aromatic Hydrocarbons; D012996:Solutions; D014867:Water; D006861:Hydrogen Peroxide