Kinetics and simulation of the decomposition of ozone in acidic aqueous solutions

The kinetics of the decomposition of ozone have been studied in acidic aque ous solutions by means of spectrophotometric techniques in order to obtain more information on the mechanism of this process. The effects of the purit y of the oxygen gas used for preparing the ozone solution, the ozone concen tration, ageing of the solution, pH (2-6), and the dependence on the ionic strength of the solution were investigated. It was found that the maximum o zone concentration and the self-decomposition of ozone in solution strongly depend on all these factors. The individual decomposition curves could be simulated successfully by using a simplified reaction scheme that involves the formation of a radical chain reaction initiated by the reaction of ozon e with hydroxide ion. This reaction scheme gives a very good representation of the experimental data over a wide pH range (1-6) and initial ozone conc entration (1.5-3.5 x 10(4) mol dm(3)) over a relatively long period of time (minutes and longer). From these simulations it was possible to obtain est imates of the equilibrium concentrations of transient species and by-produc ts formed during the decomposition of ozone. It followed from these calcula tions that the hydroxyl radical is the most abundant radical species and hy drogen peroxide a major product in equilibrated ozone solutions.