Oxidation of diclofenac by birnessite: Identification of products and proposed transformation pathway

Yue Zhao; Fei Liu; Min Wang; Xiaopeng Qin

doi:10.1016/j.jes.2020.05.017

Oxidation of diclofenac by birnessite: Identification of products and proposed transformation pathway

J Environ Sci (China). 2020 Dec:98:169-178. doi: 10.1016/j.jes.2020.05.017. Epub 2020 Jun 19.

Authors

Yue Zhao¹, Fei Liu², Min Wang³, Xiaopeng Qin⁴

Affiliations

¹ Institute of Quality Standards and Testing Technology for Agro-Products, Key Laboratory of Agro-Product Quality and Safety, Chinese Academy of Agricultural Sciences, Beijing 100081, China; School of Water Resources and Environment, and Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China.
² School of Water Resources and Environment, and Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China. Electronic address: feiliu@cugb.edu.cn.
³ Institute of Quality Standards and Testing Technology for Agro-Products, Key Laboratory of Agro-Product Quality and Safety, Chinese Academy of Agricultural Sciences, Beijing 100081, China. Electronic address: wangmin@caas.cn.
⁴ Department of Technology Assessment, Technical Centre for Soil, Agricultural and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing 100012, China.

PMID: 33097149
DOI: 10.1016/j.jes.2020.05.017

Abstract

Diclofenac (DCF), a widely used non-steroidal anti-inflammatory, reacted readily with birnessite under mild conditions, and the pseudo first order kinetic constants achieved 8.84 × 10^-2 hr^-1. Five products of DCF including an iminoquinone product (2,5-iminoquinone-diclofenac) and four dimer products were observed and identified by tandem mass spectrometry during the reaction. Meanwhile, 2,5-iminoquinone-diclofenac was identified to be the major product, accounting for 83.09% of the transformed DCF. According to the results of spectroscopic Mn(III) trapping experiments and X-ray Photoelectron Spectroscopy, Mn(IV) contained in birnessite solid was consumed and mainly converted into Mn(III) during reaction process, which proved that the removal of DCF by birnessite was through oxidation. Based on the identified products of DCF and the changes of Mn valence state in birnessite solid, a tentative transformation pathway of DCF was proposed.

Keywords: Birnessite; Diclofenac; Emerging contaminants; Oxidation mechanism; Transformation pathway.

MeSH terms

Anti-Inflammatory Agents, Non-Steroidal
Diclofenac*
Oxidation-Reduction
Oxides*

Substances

Anti-Inflammatory Agents, Non-Steroidal
Oxides
birnessite
Diclofenac