Kinetics and mechanism of the sonolytic destruction of methyl tert-butyl ether by ultrasonic irradiation in the presence of ozone

The kinetics and mechanism of the sonolytic degradation of methyl tert-butyl ether (MTBE) have been investigated at an ultrasonic frequency of 205 kHz and power of 200 W L-1. The observed first-order degradation rate constant for the loss of MTBE increased from 4.1 x 10(-4) s(-1) to 8.5 x 10-4 s(-1) as the concentration of MTBE decreased from 1.0 to 0.01 mM. In the presence of O-3, the sonolytic rate of destruction of MTBE was accelerated substantially. The rate of MTBE sonolysis with ozone was enhanced by a factor of 1.5-3.9 depending on the initial concentration of MTBE. tert-Butyl formate, tert-butyl alcohol, methyl acetate, and acetone were found to be the primary intermediates and byproducts of the degradation reaction with yields of 8, 5, 3, and 12%, respectively. A reaction mechanism involving three parallel pathways that include the direct pyrolytic decomposition of MTBE, the direct reaction of MTBE with ozone, and the reaction of MTBE with hydroxyl radical is proposed.