Effects of Monochromatic UV-Visible Light and Sunlight on Fe(III)-Catalyzed Oxidation of Dissolved Sulfur Dioxide
| Autor: | Taixing Wu, Jian Zhan, Yuegang Zuo |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Journal of Atmospheric Chemistry. 50:195-210 |
| ISSN: | 1573-0662 0167-7764 |
| DOI: | 10.1007/s10874-005-2813-y |
| Popis: | The effect of UV-visible light and natural sunlight on the Fe(III)-catalyzed oxidation of dissolved sulfur dioxide has been studied under the conditions representative for those of acidified atmospheric liquids. The experimental results have shown that both sunlight and UV-visible light enhance the rate of Fe(III)-catalyzed oxidation of aqueous sulfite with wavelength ranging from 300 to 575 nm. The light enhanced oxidation is mainly due to photochemical formation of OH radicals from Fe(OH)2+ complexes in the wavelength region below 420 nm and SO3•− free radicals from Fe(III) sulfite complexes above 420 nm in the absence of organic ligands. Like the Fe(III)-catalyzed thermal chemical oxidation, the Fe(III)-catalyzed photochemical oxidation is also first order with respect to sulfite ion concentration. The sunlight irradiation can increase the Fe(III)-catalyzed oxidation of S(IV) over 45%. The presence of organic complex ligands, such as oxalate, can completely inhibit the Fe-catalyzed oxidation of S(IV) in the dark. However, the photolysis of Fe(III)-oxalato complexes generates oxalate free radicals, leading to the formation of H2O2 and OH radicals and the oxidation of S(IV). The rate of Fe(III)-catalyzed oxidation of S(IV) species is found to increase with increasing light intensity. The effects of sunlight on the Fe(III)-catalyzed oxidation of S(IV) should be taken into account when predicting the daytime rates of sulfuric acid formation in atmospheric water droplets. |
| Databáze: | OpenAIRE |
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