Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, China.
Jinzhou Inspection, Examination and Certification Centre, Jinzhou, 121000, China.
Chemosphere. 2020 Apr;244:125582. doi: 10.1016/j.chemosphere.2019.125582. Epub 2019 Dec 9.
As the most typical geological environment, limestone landforms are widespreading in the world and affect the waters that flow around them, which may also change the fate of organic contaminants in these waters. In this study, aquatic environment surrounding limestone was simulated with calcium carbonate, and the photolysis of tetracycline was evaluated under UV irradiation (30 μW/cm). More tetracycline (up to 98%) was removed in 4 h in the presence of calcium carbonate while only 50% of tetracycline was eliminated in control experiment. The removal of tetracycline was greatly enhanced due to the major roles of alkaline pH and minor roles of Ca and HCO/CO. In alkaline pH, tetracycline existed as TCs with higher electronic density in the ring structures, which was more easily attacked by OH. Besides, it could also change the bond orbital energy to facilitate tetracycline absorbing more photon. Moreover, alkaline pH was beneficial to generate more OH and thus promote the indirect photolysis. In addition, alkaline pH also changed the degradation path of tetracycline and rapidly convert tetracycline to the byproducts with m/z 457 via hydroxylation and hydrogen abstraction. This work provides not only better understanding about the fate of tetracycline in aquatic environments but also new insights into the treatment of antibiotic-contaminated water.
作为最典型的地质环境，石灰岩地貌在世界范围内广泛分布，影响着周围的水流，这也可能改变这些水中有机污染物的命运。在这项研究中，用碳酸钙模拟了石灰岩周围的水生环境，并在紫外线照射（30 μW/cm）下评估了四环素的光解。在碳酸钙存在的情况下，四环素在 4 小时内被去除了高达 98%，而在对照实验中只有 50%的四环素被去除。由于碱性 pH 值的主要作用和 Ca 和 HCO/CO 的次要作用，四环素的去除率大大提高。在碱性 pH 值下，四环素以具有更高电子密度的 TCs 形式存在于环结构中，更容易被 OH 攻击。此外，它还可以改变键轨道能量，使四环素更容易吸收更多的光子。此外，碱性 pH 值有利于生成更多的 OH，从而促进间接光解。此外，碱性 pH 值还改变了四环素的降解途径，并通过羟化和氢提取迅速将四环素转化为 m/z 457 的副产物。这项工作不仅提供了对四环素在水生环境中命运的更好理解，也为处理抗生素污染水提供了新的见解。
