Occurrence and cycle of dissolved iron mediated by humic acids resulting in continuous natural photodegradation of 17α-ethinylestradiol

Danni Cui; Huan He; Wenxiao Xie; Shanshan Yang; Ziwei Guo; Zhicheng Liao; Feng Liu; Chaochao Lai; Xiaomin Ren; Bin Huang; Xuejun Pan

doi:10.1016/j.jhazmat.2023.133155

Occurrence and cycle of dissolved iron mediated by humic acids resulting in continuous natural photodegradation of 17α-ethinylestradiol

J Hazard Mater. 2024 Mar 5:465:133155. doi: 10.1016/j.jhazmat.2023.133155. Epub 2023 Dec 2.

Authors

Danni Cui¹, Huan He², Wenxiao Xie¹, Shanshan Yang³, Ziwei Guo¹, Zhicheng Liao⁴, Feng Liu¹, Chaochao Lai¹, Xiaomin Ren¹, Bin Huang¹, Xuejun Pan⁴

Affiliations

¹ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China.
² Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China. Electronic address: huanhe08@kust.edu.cn.
³ School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China.
⁴ Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650500, China; Southwest United Graduate School, Kunming 650092, China.

PMID: 38091802
DOI: 10.1016/j.jhazmat.2023.133155

Abstract

17α-ethinylestradiol (EE2), a synthetic endocrine-disrupting chemical, can degrade in natural waters where humic acids (HA) and dissolved iron (DFe) are present. The iron is mostly bound in Fe(III)-HA complexes, the formation process of Fe(III)-HA complexes and their effect on EE2 degradation were explored in laboratory experiments. The mechanism of ferrihydrite facilitated by HA was explored with results indicating that HA facilitated the dissolution of ferrihydrite and the generation of Fe(III)-HA complexes with the stable chemical bonds such as C-O, CO in neutral, alkaline media with a suitable Fe/C ratio. ¹O₂, •OH, and ³HA* were all found to be important in the photodegradation of EE2 mediated by Fe(III)-HA complexes. Fe(III)-HA complexes could produce Fe(II) and hydrogen peroxide (H₂O₂) to create conditions suitable for photo-Fenton reactions at neutral pH. HA helped to maintain higher dissolved iron concentrations and alter the Fe(III)/Fe(II) cycling. The natural EE2 photodegradation pathway elucidated here provides a theoretical foundation for investigating the natural transformation of other trace organic contaminants in aquatic environments.

Keywords: 17α-ethinylestradiol; Complexes; Humic acids; Photodegradation; Photoreduction.