Sonochemical degradation rates of volatile solutes
Journal
Journal of Physical Chemistry A
Journal Volume
103
Journal Issue
15
Pages
2696-2699
Date Issued
1999
Author(s)
Abstract
We report degradation rates of chlorinated methanes, ethanes, and ethenesspanning the range of Henry's law constants 0.9 ≤ H/(atm M-1) ≤ 24.5in water solutions sonicated at f = 205, 358, 618, and 1078 kHz. First-order degradation rate constants, k-X, vary as k-X ∼ HX0.30±0.03 at all frequencies, change with f by less than a factor of 2 in this range, and peak at about 600 kHz for all species. We show that experimental rates are consistent with (1) complete decomposition of the solute contained in collapsing bubbles, (2) about 15% ultrasound power efficiency for transient cavitation, and (3) a rather flat N(Ro) ∝ Ron, n ∼ 0, initial radius bubble distribution under continuous sonication. The solute content of collapsing bubbles is composed of the equilibrated vapor at Ro, plus the amount incorporated by diffusion from the surrounding solution during the acoustically driven expansion from Ro to Rmax, the maximum radius attained prior to collapse. The finding that k-X's decline above 600 kHz is ascribed to the fact that increasingly smaller bubbles collapse at rates reaching a limiting value at sufficiently high frequencies.
SDGs
Type
journal article