State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, China.
Department of Chemistry, Karakorum International University, Gilgit-Balitstan, 15100, Pakistan.
Environ Sci Pollut Res Int. 2016 Oct;23(19):19921-30. doi: 10.1007/s11356-016-6956-y. Epub 2016 Jul 16.
Sulfonamide antibiotics (SAs) have been observed to undergo direct and indirect photodegradation in natural water environments. In this study, the density functional theory (DFT) method was employed for the study of direct and indirect photodegradation mechanisms of sulfameter (SME) with excited triplet states of dissolved organic matter ((3)DOM(*)) and metal ions. SME was adopted as a representative of SAs, and SO2 extrusion product was obtained with different energy paths in the triplet-sensitized photodegradation of the neutral (SME(0)) and the anionic (SME(-)) form of SME. The selected divalent metal ions (Ca(2+), Mg(2+), and Zn(2+)) promoted the triplet-sensitized photodegradation of SME(0) but showed an inhibitory effect in triplet-sensitized photodegradation of SME(-). The triplet-sensitized indirect photodegradation mechanism of SME was investigated with the three DOM analogues, i.e., 2-acetonaphthone (2-AN), fluorenone (FN), and thioxanthone (TN). Results indicated that the selected DOM analogues are highly responsible for the photodegradation via attacking on amine moiety of SME. According to the natural bond orbital (NBO) analysis, the triplet-sensitized photodegradation mechanism of SME(0) with 2-AN, FN, and TN was H-transfer, and the SME(-) was proton plus electron transfer with these DOM analogues.
磺胺类抗生素（SAs）在自然水环境中会发生直接和间接光降解。本研究采用密度泛函理论（DFT）方法研究了溶解有机物（3DOM（*））和金属离子激发三重态下磺胺脒（SME）的直接和间接光降解机制。SME 被选为 SAs 的代表，在中性（SME(0)）和阴离子（SME(-)）形式的 SME 的三重态敏化光降解中，通过不同的能量路径获得了 SO2 挤出产物。选择的二价金属离子（Ca(2+)、Mg(2+)和 Zn(2+)）促进了 SME(0)的三重态敏化光降解，但对 SME(-)的三重态敏化光降解表现出抑制作用。研究了三种 DOM 类似物，即 2-乙酰萘（2-AN）、芴酮（FN）和噻吨酮（TN）对 SME 的三重态敏化间接光降解机制。结果表明，所选的 DOM 类似物对通过攻击 SME 的胺基部分的光降解具有高度的责任。根据自然键轨道（NBO）分析，SME(0)与 2-AN、FN 和 TN 的三重态敏化光降解机制是 H 转移，而 SME(-)与这些 DOM 类似物的质子加电子转移。
