The pH dependence and role of fluorinated substituent of enoxacin binding to ferrihydrite

Liting Wang; Liwen Zhang; Baogen Feng; Xiuyi Hua; Yanchun Li; Wenming Zhang; Zhiyong Guo

doi:10.1016/j.scitotenv.2022.153707

The pH dependence and role of fluorinated substituent of enoxacin binding to ferrihydrite

Sci Total Environ. 2022 Jun 1:823:153707. doi: 10.1016/j.scitotenv.2022.153707. Epub 2022 Feb 8.

Authors

Liting Wang¹, Liwen Zhang¹, Baogen Feng², Xiuyi Hua¹, Yanchun Li³, Wenming Zhang⁴, Zhiyong Guo⁵

Affiliations

¹ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin Provincial Key Laboratory of Water Resources and Environment, College of New Energy and Environment, Jilin University, Changchun 130012, China.
² China Three Gorges Corporation, Beijing 100038, China.
³ Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130023, China.
⁴ Dept of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
⁵ Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin Provincial Key Laboratory of Water Resources and Environment, College of New Energy and Environment, Jilin University, Changchun 130012, China. Electronic address: zyguo@jlu.edu.cn.

PMID: 35149063
DOI: 10.1016/j.scitotenv.2022.153707

Abstract

The sorption of antibiotics on iron (hydr)oxides is an important process that influences their environmental fate. Ferrihydrite (Fh) nanosized iron hydroxide is omnipresent in nature. However, the sorption mechanism of fluoroquinolone (FQ) antibiotics on Fh is unclear. Here, a combined experimental and computational study was conducted to investigate the sorption of enoxacin (ENO) as one model of FQs on Fh. Pipemidic acid (PPA), as a structural analog of ENO, was selected to compare the effect of fluorinated substituent on the sorption mechanism. Results indicated that the average K_d values of ENO at pH = 7.0 and 8.0 were 1.72 and 2.75 times higher than those at pH in the ranges of 4.0-6.0 and 9.0-10.0, respectively. The main sorption mechanisms included electrostatic, hydrophobic interaction, and inner-sphere complexation. The fluorinated substituent of ENO facilitated its sorption on Fh through enhancing its hydrophobicity as well as modifying its dissociation constants and charge distribution. The findings give new insights into the significant influence of active fluorinated substituents on the environmental behaviors of fluorinated pharmaceuticals.

Keywords: Antibiotic; Fluorine; Fluoroquinolone; Iron mineral; Sorption.

MeSH terms

Adsorption
Enoxacin*
Ferric Compounds* / chemistry
Hydrogen-Ion Concentration
Iron

Substances

Ferric Compounds
Enoxacin
ferric oxyhydroxide
Iron