Department of Chemistry and Biochemistry, California State University at Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA.
J Phys Chem A. 2010 Aug 19;114(32):8391-5. doi: 10.1021/jp104509t.
The beta-lactam antibiotics are some of the most prevalent pharmaceutical contaminants currently being detected in aquatic environments. Because the presence of any trace level of antibiotic in water may adversely affect aquatic ecosystems and contribute to the production of antibiotic-resistant bacteria, active removal by additional water treatments, such as using advanced oxidation and reduction processes (AO/RPs), may be required. However, to ensure that any AOP treatment process occurs efficiently and quantitatively, a full understanding of the kinetics and mechanisms of all of the chemical reactions involved under the conditions of use is necessary. In this study, we report on our kinetic measurements for the hydroxyl-radical-induced oxidation of 11 beta-lactam antibiotics obtained using electron pulse radiolysis techniques. For the 5-member ring species, an average reaction rate constant of (7.9 +/- 0.8) x 10(9) M(-1) s(-1) was obtained, slightly faster than for the analogous 6-member ring containing antibiotics, (6.6 +/- 1.2) x 10(9) M(-1) s(-1). The consistency of these rate constants for each group infers a common reaction mechanism, consisting of the partitioning of the hydroxyl radical between addition to peripheral aromatic rings and reaction with the central double-ring core of these antibiotics.
β-内酰胺类抗生素是目前在水生环境中检测到的最常见的药物污染物之一。由于水中存在任何痕量水平的抗生素都可能对水生生态系统产生不利影响，并导致抗生素耐药菌的产生，因此可能需要额外的水处 理方法（如使用高级氧化还原工艺（AO/RPs））来主动去除。然而，为了确保任何 AOP 处理过程高效且定量地进行，需要充分了解在使用条件下涉及的所有化学反应的动力学和机制。在这项研究中，我们报告了使用电子脉冲辐射技术获得的羟基自由基诱导的 11 种β-内酰胺类抗生素氧化的动力学测量结果。对于 5 元环种类，获得的平均反应速率常数为（7.9 ± 0.8）x 10(9) M(-1) s(-1)，略快于具有类似 6 元环的抗生素，（6.6 ± 1.2）x 10(9) M(-1) s(-1)。每个组的这些速率常数的一致性推断出一个共同的反应机制，包括羟基自由基在加 入外围芳环和与这些抗生素的中环核心反应之间的分配。
