Kinetic modeling of pyruvic acid ozonation in aqueous solutions catalyzed by Mn(II) and Mn(IV) ions

The ozonation of pyruvic acid (2-ketopropionic acid) in aqueous solutions, catalyzed by Mn(II) and Mn(IV) ions, has been studied at three different pH values (pH=1.1, 2.0 and 3.0). A mathematical model of the unsteady operati on of the experimental reactor has been developed, which takes into account the reactions occurring in the liquid phase and the ozone mass transfer fr om the gas bubbles. Those reactions have been described with two alternativ e kinetic models, both made out of four elementary steps. The two kinetic m odels correlate the experimental data with a fair accuracy, respectively at the lowest and at the highest pH examined. In particular, at pH=3.0, the o zonation results are inhibited by the acetate ions produced by the reaction itself. This effect has been correctly described in the terms of a complex formed with the low oxidation-state manganese, which successively reacts w ith the dissolved ozone. (C) 2000 Elsevier Science Ltd. All rights reserved .