Photolysis of Ozone in Aqueous Solutions in the Presence of Tertiary Butanol
| Autor: | Heinz-Peter Schuchmann, Clements Von Sonntag, Erika Reisz, Winfried Schmidt |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Photolysis
Ozone Aqueous solution tert-Butyl Alcohol Hydroxyl Radical Chemistry Butanol Radical Photodissociation Free-radical reaction Quantum yield General Chemistry Models Theoretical Oxidants Photochemistry chemistry.chemical_compound Oxidants Photochemical Reaction rate constant Environmental Chemistry Organic chemistry |
| Zdroj: | Environmental Science & Technology. 37:1941-1948 |
| ISSN: | 1520-5851 0013-936X |
| DOI: | 10.1021/es0113100 |
| Popis: | The ozone decomposition quantum yield (phi) in millimolar and higher-concentration aqueous tertiary butanol solution is 0.64 +/- 0.05 (observed over a wavelength range from 250 to 280 nm) and rises toward lower tertiary butanol concentrations (phi approximately 1.5 at 10(-5) M at pH 2) on account of the onset of the well-known *OH-radical-induced chain reaction. The destruction of the organic is initiated by hydrogen-atom abstraction through OH radicals which are produced via the reaction of the photolytically generated O(1D) with the solvent water at a quantum yield of phi(*OH) of about 0.1. There is no decomposition of ozone in the dark on the time scale of the photolysis experiment. The efficiency of tertiary butanol destruction with respect to ozone consumption ([O3]0 = 3 x 10(-4) M), defined by the ratio delta[t-BuOH]/delta[O3], termed eta(t-BuOH), is 0.26 at millimolar tertiary butanol concentrations, determined at the stage of essentially complete ozone consumption. It diminishes toward lower tertiary butanol concentrations (delta[t-BuOH]/delta[O3] approximately 0.17 at [t-BuOH]0 = 1 x 10(-4) M). Part of the effect of the ozone, apart from being a source of *OH radicals, rests on the intervention of HO2*/O2*- which is produced in the course of the peroxyl-radical chemistry of the tertiary butanol in this dioxygen-saturated environment and converted into further *OH radical by reaction with ozone. Moreover in this system, organic free radicals and peroxyl radicals react with the ozone. On the basis of the experimental and mechanistic-simulation data, the quantum yield of direct (by hv) ozone cleavage in aqueous solution is estimated at about 0.5. |
| Databáze: | OpenAIRE |
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