THE PRIMARY REACTION IN THE DECOMPOSITION OF OZONE IN ACIDIC AQUEOUS-SOLUTIONS

The primary step in the thermal decomposition of acidic aqueous ozone solutions is the dissociation reaction: O3 reversible O + O2. This reaction is supported by the retarding effect of O2 on the decomposition rate, by our activation energy measurements, E(A) = 79.5 +/- 8.0 kJ mol-1, and by isotopic exchange experiments with O-18(2),O-18(2). The rates of ozone decomposition were measured at pHs O-4, at temperatures 0-46-degrees-C, and at O2 concentrations 10(-5)-10(-3) M. The O atom formed in the dissociation reaction is postulated to be the precursor for OH and HO2 formation. The ionization of the HO2 free radical (pK = 4.8) accounts for the increase in rate with rising pH. The mechanistic implications of O3 decomposition in acid solution are briefly discussed.