Kinetics of oxidation of ammonia in solutions containing ozone with or without hydrogen peroxide

This research investigates the kinetics of traditional ozonation and peroxone oxidation of ammonia in alkaline solutions. The ozonation reaction is governed by the direct oxidation of ammonia with ozone molecules, and the overall kinetics is second order, with first order each in ozone and ammonia. The reaction rate increases slightly with temperature, and at 25 degrees C, the overall rate constant varies from 12.3 to 27.0 1/Ms as the pH increases from 8 to 10. In the presence of hydrogen peroxide, the peroxone oxidation is controlled mainly by the formation of hydroxyl radical and its subsequent radical reactions. The depletion rate of ozone is first order with respect to both concentrations of ozone and hydrogen peroxide but is nearly independent of the ammonia concentration. The overall rate constant increases from 5860 to 133 000 1/Ms in the pH range of 8-10 at 25 degrees C, indicating that the rate increases with the hydroxyl ion concentration of the exponent of 0.71. The destruction rate of ammonia depends on concentrations of various species, and for wastewaters containing high concentrations of ammonia, the peroxone oxidation process can be effective and economical to achieve a high efficiency for ozone utilization.