Issue 3, 2017

The degradation mechanism of sulfamethoxazole under ozonation: a DFT study

Abstract

Sulfamethoxazole (SMX), a kind of antibiotic, remains in the environment and threatens public health. Ozone as a strong and green oxidant was widely used for selective oxidation degradation of residual SMX. However, it is hard to elucidate the detailed oxidation mechanism through current experimental approaches. A theoretical study has been carried out herein for exploring possible ozonation pathways of SMX. Two reaction mechanisms, viz., direct addition (DA) and H atom transfer (HAT), are considered. The results show that the primary oxidation of aromatic rings (benzene or isoxazole rings) of SMX follows the DA mechanism, featuring an electrophilic addition. Whereas, the oxidation of amino and methyl groups of SMX follows the HAT mechanism. Following the proposed mechanisms, the primary oxidation products detected in previous experiments could reasonably be obtained according to the current calculations. More importantly, O3 molecules as an electrophilic agent feasibly attack the moiety having a large orbital contribution to the highest occupied molecular orbital (HOMO) of sulfonamides. This result suggests that the primary ozonation site of sulfonamides could be theoretically predictable through the information of their frontier molecular orbitals. Meanwhile, a positive correlation between the O3-mediated HAT energy barriers and bond dissociation energies has been found for N–H and C–H bond oxidations.

Graphical abstract: The degradation mechanism of sulfamethoxazole under ozonation: a DFT study

Supplementary files

Article information

Article type
Paper
Submitted
23 十二月 2016
Accepted
23 一月 2017
First published
24 一月 2017

Environ. Sci.: Processes Impacts, 2017,19, 379-387

The degradation mechanism of sulfamethoxazole under ozonation: a DFT study

H. Yu, P. Ge, J. Chen, H. Xie and Y. Luo, Environ. Sci.: Processes Impacts, 2017, 19, 379 DOI: 10.1039/C6EM00698A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements