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Article

Indirect Photodegradation of Sulfamethoxazole and Trimethoprim by Hydroxyl Radicals in Aquatic Environment: Mechanisms, Transformation Products and Eco-Toxicity Evaluation

1
Environment Research Institute, Shandong University, Qingdao 266237, China
2
College of Biological and Environmental Engineering, Binzhou University, Binzhou 256600, China
*
Author to whom correspondence should be addressed.
Int. J. Mol. Sci. 2020, 21(17), 6276; https://doi.org/10.3390/ijms21176276
Received: 11 August 2020 / Revised: 26 August 2020 / Accepted: 28 August 2020 / Published: 30 August 2020
(This article belongs to the Section Physical Chemistry and Chemical Physics)
The bacteriostatic antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), have frequently been found in wastewater and surface water, which raises the concerns about their ecotoxicological effects. The indirect photochemical transformation has been proven to be an efficient way to degrade SMX and TMP. In this study, the reaction mechanisms of the degradation by SMX and TMF by OH radicals were investigated by theoretical calculations. Corresponding rate constants were determined and the eco-toxicity of SMX and TMP and its degradations products were predicted using theoretical models. The results indicate that the most favorable pathways for the transformation of SMX and TMP are both •OH-addition reaction of benzene ring site with lowest Gibbs free energy barriers (6.86 and 6.21 kcal mol−1). It was found that the overall reaction rate constants of •OH-initial reaction of SMX and TMP are 1.28 × 108 M−1 s−1 and 6.21 × 108 M−1 s−1 at 298 K, respectively. When comparing the eco-toxicity of transformation products with parent SMX and TMP, it can be concluded that the acute and chronic toxicities of the degraded products are reduced, but some products remain harmful for organisms, especially for daphnid (toxic or very toxic level). This study can give greater insight into the degradation of SMX and TMP by •OH through theoretical calculations in aquatic environment. View Full-Text
Keywords: sulfamethoxazole (SMX); trimethoprim (TMP); hydroxyl radical (•OH); transformation mechanisms; photoproducts; eco-toxicity sulfamethoxazole (SMX); trimethoprim (TMP); hydroxyl radical (•OH); transformation mechanisms; photoproducts; eco-toxicity
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MDPI and ACS Style

Yang, J.; Lv, G.; Zhang, C.; Wang, Z.; Sun, X. Indirect Photodegradation of Sulfamethoxazole and Trimethoprim by Hydroxyl Radicals in Aquatic Environment: Mechanisms, Transformation Products and Eco-Toxicity Evaluation. Int. J. Mol. Sci. 2020, 21, 6276. https://doi.org/10.3390/ijms21176276

AMA Style

Yang J, Lv G, Zhang C, Wang Z, Sun X. Indirect Photodegradation of Sulfamethoxazole and Trimethoprim by Hydroxyl Radicals in Aquatic Environment: Mechanisms, Transformation Products and Eco-Toxicity Evaluation. International Journal of Molecular Sciences. 2020; 21(17):6276. https://doi.org/10.3390/ijms21176276

Chicago/Turabian Style

Yang, Jiaoxue, Guochun Lv, Chenxi Zhang, Zehua Wang, and Xiaomin Sun. 2020. "Indirect Photodegradation of Sulfamethoxazole and Trimethoprim by Hydroxyl Radicals in Aquatic Environment: Mechanisms, Transformation Products and Eco-Toxicity Evaluation" International Journal of Molecular Sciences 21, no. 17: 6276. https://doi.org/10.3390/ijms21176276

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