Indirect Photodegradation of Amine Drugs in Aqueous Solution under Simulated Sunlight

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• 作者：Yong Chen ; Chun Hu ; Xuexiang Hu ; Jiuhui Qu
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：April 15, 2009
• 年：2009
• 卷：43
• 期：8
• 页码：2760-2765
• 全文大小：159K
• 年卷期：v.43,no.8(April 15, 2009)
• ISSN：1520-5851

文摘

The photodegradation of the widely used amine drugs including primary amine (mexiletine), secondary amine (propranolol, phenytoin), and tertiary amine (diphenhydramine, antipyrine) were investigated in the presence of nitrate and humic substances under simulated sunlight. All of the amine drugs were photodegraded by nitrate due to the attack of hydroxyl radicals (^•OH). The bimolecular rate constants for the reaction between each amine drug and ^•OH ranged from (2.1 ± 0.2) × 10⁹ to (8.7 ± 0.3) × 10⁹ M⁻¹ s⁻¹. In contrast, only mexiletine, propranolol, and diphenhydramine were selectively photodegraded in the presence of humic substances (HS). Fulvic acid was a more efficient sensitizer than humic acid throughout. The HS triplet states were verified to be main reactive species in the photochemical reaction. Furthermore, an electron transfer mechanism for the reaction with the HS triplet states was proposed on the basis of all information obtained under a series of experiments. The electron transfer from the nonbonding electrons on nitrogen (N-electrons) of the amine drugs to the excited ketone of the HS occurred. The availability of N-electrons and presence of hydrogen on carbon α of amine (α-hydrogen) were two key factors for the electron-transfer interaction. Moreover, the photoproducts were identified by GC-MS and the degradation pathways were proposed. The results strongly suggest the impact of humic substances on the photochemical fate of amine drugs in the natural waters.