Kinetics and mechanism of the enhanced reductive degradation of nitrobenzene by elemental iron in the presence of ultrasound

Article abstract of DOI:10.1021/es990385p

The degradation of nitrobenzene (NB) and aniline (AN) were facilitated by using sonolysis, reduction by Fe⁰ and a combination of the two processes. The rates of NB reduction by Fe⁰ increased in the presence of ultrasound. The first-order rate constant for NB degradation by ultrasound was 1.8 x 10^-3/min. The rate was considerably faster in the presence of Fe⁰. The similar degradation rates for AN in each system indicated that the sonication process was unaffected by the presence of Fe⁰. The rate enhancements for the NB degradation can be explained chiefly by the continuous cleaning and chemical activation of the Fe⁰ surfaces by acoustic cavitation and to accelerated mass transport rates of reactants, intermediates and products between the solution phase and the Fe⁰ surface. The relative concentrations of nitrosobenzene and AN, the main reaction intermediates produced by Fe⁰ reduction, were significantly changed in the presence of ultrasound.