Department of Chemistry, University of La Rioja, C/Madre de Dios 53, E-26006, Logroño, La Rioja, Spain.
Department of Chemistry, University of La Rioja, C/Madre de Dios 53, E-26006, Logroño, La Rioja, Spain.
Chemosphere. 2020 May;247:125910. doi: 10.1016/j.chemosphere.2020.125910. Epub 2020 Jan 14.
The photocatalytic degradation of the antibiotic ciprofloxacin in water was carried out with nanosheets of graphitic carbon nitride (g-CN) as catalyst and visible light irradiation using low-power (4 × 10 W) white light LEDs. The aim of this study was to identify the intermediate by-products formed during the degradation and to propose a pathway for CIP degradation. To achieve this goal, photocatalytically degraded CIP solutions were analysed by liquid chromatography coupled to high-resolution mass spectrometry using a QTOF instrument. The accurate mass and the MS/MS data of the detected ions allowed us to determine the elementary composition of eight by-products and to propose the chemical structures for seven of them. Three of these by-products have been reported for the first time and the elementary composition of a fourth one that had been wrongly reported in the literature was accurately established. CIP degradation followed a pseudo-first order kinetics with a pseudo-first order kinetic constant of 0.035 min. In addition, a study of the influence of several scavengers showed that only the presence of triethanolamine dramatically reduced the pseudo-first order kinetic constant (0.00072 min), pointing out that the reactive species were the holes produced in the catalyst. Finally, the main pathway of CIP degradation seems to be the attack to the piperazine group by ·OH radicals, following heterocycle breakup and the subsequent loss of two of its carbon atoms as CO molecules, and then defluorination, oxidation and cleavage of the cycles of this intermediate.
采用纳米片石墨相氮化碳（g-CN）作为催化剂，在低功率（4×10 W）白色发光二极管可见光照射下，对水中的抗生素环丙沙星进行光催化降解。本研究的目的是确定降解过程中形成的中间产物，并提出 CIP 降解途径。为了实现这一目标，使用 QTOF 仪器，通过液相色谱与高分辨率质谱联用分析光催化降解的 CIP 溶液。检测到的离子的精确质量和 MS/MS 数据使我们能够确定八种副产物的元素组成，并对其中七种提出化学结构。其中三种副产物是首次报道的，而文献中错误报道的第四种副产物的元素组成也得到了准确的确定。CIP 的降解遵循拟一级动力学，拟一级动力学常数为 0.035 min。此外，对几种猝灭剂影响的研究表明，只有三乙醇胺的存在才会显著降低拟一级动力学常数（0.00072 min），这表明反应性物质是催化剂中产生的空穴。最后，CIP 降解的主要途径似乎是·OH 自由基攻击哌嗪基团，随后杂环断裂，接着失去两个碳原子作为 CO 分子，然后脱氟、氧化和裂解这个中间产物的环。
