Ozone decomposition in water studied by pulse radiolysis. 2. Hydroxyl and hydrogen tetroxide (HO4) as chain intermediates

✍ Scribed by Staehelin, J.; Buehler, R. E.; Hoigne, J.

• Book ID: 111859921
• Publisher: American Chemical Society
• Year: 1984
• Tongue: English
• Weight: 679 KB
• Volume: 88
• Category: Article
• ISSN: 0022-3654
• DOI: 10.1021/j150668a051

✦ Synopsis

Ozone decomposition in pure water involves a chain mechanism, initiated by the reaction OH-+ O3 and propagated by 02and OH. In the present studies this chain is initiated by pulse radiolysis of aqueous solutions of ozone. The chain propagation steps were studied in two parts: (I) 0, -0, -H 0 3 -OH and (11) OH + O3 -... -H 0 2 -0,. By computer simulation of the rate curves, it is shown that from OH + O3 an intermediate H 0 4 must be formed, most likely a charge-transfer complex (H0.03), which eventually decays into H02. The derived rate constants are k(OH+O,) = (2.0 f 0.5) X lo9 M-' s-l, k(H04-+H02+02) = (2.8 f 0.3) X lo4 s-I, and k(H04--+OH+03) < k(H04-H02+02). The spectrum of H 0 4 is derived.It is similar to the one of ozone, but the absorption coefficients are about 50% larger. In the presence of high ozone concentration, the dominant chain termination reactions are H 0 4 + H 0 4 and H 0 4 + HOB. The effect on chain length, dose, overall rate, and pH and of added scavengers is described. The implications for the natural ozone decay mechanism are discussed.