Photosensitizer Method to Determine Rate Constants for the Reaction of Carbonate Radical with Organic Compounds
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- 作者：Silvio Canonica ; Tamar Kohn ; Marek Mac ; Francisco J. Real ; Jakob Wirz ; and Urs von Gunten
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：December 1, 2005
- 年：2005
- 卷：39
- 期：23
- 页码：9182 - 9188
- 全文大小：159K
- 年卷期：v.39,no.23(December 1, 2005)
- ISSN：1520-5851
文摘
Carbonate radical (CO3
-) is a powerful oxidant that ispresent in sunlit surface waters and in waters treated byadvanced oxidation processes. The production of CO3-in aqueous solution through oxidation of carbonate anionby excited triplet states of aromatic ketones wasinvestigated in this study to provide new methods for thedetermination of rate constants and to explore a possiblephotoinduced pathway of CO3- formation in the aquaticenvironment. Rate constants for triplet quenching by carbonateanion of up to 3.0 × 107 M-1 s-1 and CO3- yieldsapproaching unity, determined using laser flash photolysis,allowed us to conclude that such a formation mechanismmight be significant in sulit natural waters. Kineticmethods based on either flash photolysis or steady-stateirradiation and on the use of aromatic ketones asphotosensitizers gave bimolecular rate constants in therange of 4 × 106 to 1 × 108 M-1 s-1 for the reaction of CO3-with several s-triazine and phenylurea herbicides. Forvarious anilines and phenoxide anions, rate constantsdetermined by these methods agreed well with publishedvalues. Moreover, it could be shown for the first timeby a direct method that dissolved natural organic matter(DOM) reduces the lifetime of CO3- and a second-order rateconstant of (280 ± 90) (mg of C/L)-1 s-1 was obtainedfor Suwannee River fulvic acid.
-) is a powerful oxidant that ispresent in sunlit surface waters and in waters treated byadvanced oxidation processes. The production of CO3-in aqueous solution through oxidation of carbonate anionby excited triplet states of aromatic ketones wasinvestigated in this study to provide new methods for thedetermination of rate constants and to explore a possiblephotoinduced pathway of CO3- formation in the aquaticenvironment. Rate constants for triplet quenching by carbonateanion of up to 3.0 × 107 M-1 s-1 and CO3- yieldsapproaching unity, determined using laser flash photolysis,allowed us to conclude that such a formation mechanismmight be significant in sulit natural waters. Kineticmethods based on either flash photolysis or steady-stateirradiation and on the use of aromatic ketones asphotosensitizers gave bimolecular rate constants in therange of 4 × 106 to 1 × 108 M-1 s-1 for the reaction of CO3-with several s-triazine and phenylurea herbicides. Forvarious anilines and phenoxide anions, rate constantsdetermined by these methods agreed well with publishedvalues. Moreover, it could be shown for the first timeby a direct method that dissolved natural organic matter(DOM) reduces the lifetime of CO3- and a second-order rateconstant of (280 ± 90) (mg of C/L)-1 s-1 was obtainedfor Suwannee River fulvic acid.