Photosensitizer method to determine rate constants for the reaction of carbonate radical with organic compounds
Photosensitizer method to determine rate constants for the reaction of carbonate radical with organic compounds
复制标题
DOI：
10.1021/es051236b
复制
发表时间：
2005-12-01
影响因子：
11.4
通讯作者：
Von Gunten, U
中科院分区：
文献类型：
--
作者：
Canonica, S;Kohn, T;Von Gunten, U
碳酸根（CO 3中心点-）是一种强氧化剂，存在于阳光照射的表面沃茨和经过高级氧化工艺处理的沃茨中。本文研究了水溶液中芳香酮三重态激发态氧化碳酸根阴离子产生CO 3中心点的过程，为确定反应速率常数提供新的方法，并探索水环境中CO 3中心点形成的可能光诱导途径。利用激光闪光光解测定的碳酸根阴离子对三重态猝灭的速率常数高达3.0 × 10（7）M-1 s（-1），CO 3中心点产率接近1，这使我们能够得出结论，这种形成机制在苏利特天然沃茨中可能是重要的。基于闪光光解或稳态辐射以及使用芳香酮作为光敏剂的动力学方法给出了CO 3中心点-与几种均三嗪和苯基脲除草剂反应的双分子速率常数在4 × 10（6）至1 × 10（8）M-1 s（-1）范围内。对于各种苯胺和苯酚阴离子，速率常数由这些方法确定同意以及与公布的值。此外，还首次用直接法证明了溶解性天然有机物（DOM）降低了CO_3中心点的寿命，并得到了Suwannee河富里酸的二级速率常数为（280 ± 90）（mg C/L）（-1）s（-1）。
Carbonate radical (CO3 center dot-) is a powerful oxidant that is present in sunlit surface waters and in waters treated by advanced oxidation processes. The production Of CO3 center dot- in aqueous solution through oxidation of carbonate anion by excited triplet states of aromatic ketones was investigated in this study to provide new methods for the determination of rate constants and to explore a possible photoinduced pathway of CO3 center dot- formation in the aquatic environment. Rate constants for triplet quenching by carbonate anion of up to 3.0 x 10(7) M-1 s(-1) and CO3 center dot- yields approaching unity, determined using laser flash photolysis, allowed us to conclude that such a formation mechanism might be significant in sulit natural waters. Kinetic methods based on either flash photolysis or steady-state irradiation and on the use of aromatic ketones as photosensitizers gave bimolecular rate constants in the range of 4 x 10(6) to I x 10(8) M-1 s(-1) for the reaction of CO3 center dot- with several s-triazine and phenylurea herbicides. For various anilines and phenoxide anions, rate constants determined by these methods agreed well with published values. Moreover, it could be shown for the first time by a direct method that dissolved natural organic matter (DOM) reduces the lifetime Of CO3 center dot- and a second-order rate constant of (280 +/- 90) (mg of C/L)(-1) s(-1) was obtained for Suwannee River fulvic acid.