Reaction mechanism of chloramphenicol with hydroxyl radicals for advanced oxidation processes using DFT calculations
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ORIGINAL PAPER
Reaction mechanism of chloramphenicol with hydroxyl radicals for advanced oxidation processes using DFT calculations Lejin Xu 1
&
Wuyang Li 1 & Xiuyou Ye 2 & Enhao Zhang 1 & Chonghao Wang 1 & Jun Yang 1
Received: 17 June 2019 / Accepted: 22 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The structure properties of chloramphenicol (CAP), including bond information and the Fukui function for the atoms in the main chain, were investigated computationally by density functional theory (DFT). The result shows that the chiral carbons in CAP offer the most active positions for chemical reactions, which is in good agreement with the experiment. The detailed degradation mechanism for CAP with hydroxyl radicals in advanced oxidation processes is further studied at the SMD/M06-2X/6-311 + G(d,p) level of theory. The main reaction methods, including the addition-elimination reaction, hydrogen abstract reaction, hydroxyl radical addition, and bond-breaking processes, are calculated. The results show that the nitro-elimination reaction is the most likely reaction in the first step of the degradation of CAP, and the latter two processes are more likely to be hydrogen abstract reactions. The details for the transition states, intermediate radicals, and free energy surfaces for all proposed reactions are given, which makes up for a lack of experimental knowledge. Keywords Advanced oxidation processes . Chloramphenicol . Degradation mechanism . Density functional theory
Introduction Antibiotics, as animal growth promoters, are used worldwide in animals for the effective treatment of diseases [1]. Chloramphenicol (CAP), produced by the growth of certain strains of the soil bacterium Streptomyces venezuelae [2], is mainly prepared synthetically and has been widely used as an antimicrobial substance. The ways of CAP entering the environment mainly include sewage treatment plants and foodproducing animal husbandry. Because of the potential for the development of antimicrobial resistance, the presence and accumulation of CAP in aquatic environments have been the major threats to humans [3–5]. The effects of CAP on the human body are so severe that they can even lead to deadly diseases such as aplastic anemia and bone marrow
* Lejin Xu [email protected] 1
Department of Nuclear Engineering and Technology, School of Energy and Power Engineering, Huazhong University of Science & Technology, Wuhan 430074, People’s Republic of China
2
Zhejiang Uish Environmental Technology Co., Ltd., Ningbo 315336, Zhejiang, People’s Republic of China
suppression. Furthermore, CAP is difficult to decompose by conventional processes in sewage treatment projects [6]. Thus, it is essential to explore effective methods for the degradation and removal of CAP from wastewater. Experimental studies have already been performed to remove CAP from aqueous solutions using advanced oxidation processes (AOPs), which are based on the generation of hydroxyl radicals (•OH) [7]. Hydroxyl radicals are very aggressive
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