Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China.
Water Res. 2012 Mar 15;46(4):1327-36. doi: 10.1016/j.watres.2011.12.052. Epub 2011 Dec 31.
Trimethoprim (TMP), a bacteriostatic antibiotic, has recently been detected in wastewater and surface waters. In this study the sunlight mediated photochemical fate, and treatment using advanced oxidation and reduction (free radical) processes, have been investigated with respect to their effect on TMP. Photochemical fate, in the presence of humic acid, and advanced oxidation treatment both involve the hydroxyl radical (OH) as one of the reactive species of interest. Another reactive oxygen species, singlet oxygen (1O2), may also be important in the photochemical fate of TMP. The bimolecular reaction rate constants of TMP with 1O2 and OH were evaluated to be (3.2±0.2)×10(6) M(-1) s(-1) and 8.66×10(9) M(-1) s(-1), respectively. The reaction kinetics for the sub-structural moieties of TMP, 1,2,3-trimethoxybenzene (TMBz) and 2,4-diaminoprimidine (DAP), was evaluated to facilitate an understanding of the loss mechanisms. For TMBz and DAP the reaction rate constants with 1O2 were <1.0×10(4) and (3.0±0.1)×10(6) M(-1) s(-1), while with OH they were 8.12×10(9) and 1.64×10(9) M(-1) s(-1), respectively. The data suggests that the 1O2 attacks the DAP and the OH radical attacks the TMBz moiety. However, for TMP, 1O2 and OH reactions accounted for only ∼19% and ∼6%, of its total photodegradation, respectively. Therefore, the reaction of TMP with excited state natural organic matter is postulated as a significant degradation pathway for the loss of TMP in sunlit waters containing natural organic matter. There was no effect of pH on the direct or indirect photolysis of TMP. To complete the study for reductive treatment processes, the solvated electron reaction rates for the destruction of TMP, TMBz and DAP were also evaluated. The absolute bimolecular reaction rates obtained were, (13.6±0.01)×10(9), (6.36±0.11)×10(7) and (10.1±0.01)×10(9) M(-1) s(-1), respectively.
三甲氧苄氨嘧啶（TMP）是一种抑菌性抗生素，最近在废水和地表水被检测到。本研究采用高级氧化还原（自由基）工艺，考察了阳光介导的光化学命运及处理对 TMP 的影响。在腐殖酸存在的情况下，光化学命运和高级氧化处理都涉及到羟基自由基（OH）作为一种感兴趣的反应性物质。单线态氧（1O2）也可能是 TMP 光化学命运中的重要物质。TMP 与 1O2 和 OH 的双分子反应速率常数分别评估为(3.2±0.2)×10(6) M(-1) s(-1)和 8.66×10(9) M(-1) s(-1)。TMP 的亚结构部分，1,2,3-三甲氧基苯（TMBz）和 2,4-二氨基嘧啶（DAP）的反应动力学进行了评估，以促进对损失机制的理解。对于 TMBz 和 DAP，与 1O2 的反应速率常数分别为<1.0×10(4)和(3.0±0.1)×10(6) M(-1) s(-1)，而与 OH 的反应速率常数分别为 8.12×10(9)和 1.64×10(9) M(-1) s(-1)。数据表明，1O2 攻击 DAP，而 OH 自由基攻击 TMBz 部分。然而，对于 TMP，1O2 和 OH 的反应分别仅占其总光降解的约 19%和 6%。因此，TMP 与激发态天然有机物的反应被认为是含有天然有机物的阳光照射水中 TMP 损失的重要降解途径。pH 对 TMP 的直接或间接光解没有影响。为了完成还原处理过程的研究，还评估了 TMP、TMBz 和 DAP 破坏的溶剂化电子反应速率。获得的绝对双分子反应速率分别为(13.6±0.01)×10(9)、(6.36±0.11)×10(7)和(10.1±0.01)×10(9) M(-1) s(-1)。
