Sorption of the antimicrobial ciprofloxacin to aluminum and iron hydrous oxides.
Solution chemistry (pH, ionic strength (I), and sorbate-to-sorbent ratio) effects on ciprofloxacin sorption to hydrous oxides of Al (HAO) and Fe (HFO) were investigated using macroscopic and spectroscopic analyses. Sorption to both HAO and HFO showed a strong pH-dependent behavior, following the fraction of zwitterionic species over the entire pH range studied. Increase in I from 0.01 to 0.5 M had an insignificant effect on the extent of ciprofloxacin sorption, and isotherms were well-described by the Langmuir model. HFO possessed a higher sorption capacity (0.066 mmol kg(-1)) than HAO (0.041 mmol kg(-1)). Ligand-promoted dissolution of hydrous oxides, more pronounced for HAO, was observed in the presence of ciprofloxacin, but at a fairly high initial concentration (0.5 mM). Attenuated total reflectance Fourier transform infrared spectroscopy analysis indicated that different types of ciprofloxacin surface complexes are formed with HAO and HFO; while a monodentate mononuclear complex (with -COO-) appears likely between ciprofloxacin and HAO, keto O and one O from COO- seem to be involved in the formation of a six-membered ring with Fe on the HFO surface. The study results are expected to increase our understanding of the environmental reactivity of fluoroquinolones, an important class of antimicrobial compounds.
Gu
Cheng
C
Department of Biological Systems Engineering, Environmental Chemistry and Technology Program, University of Wisconsin, Madison 53706, USA.
Karthikeyan
K G
KG
D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002939:Ciprofloxacin / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
D000900:Anti-Bacterial Agents; D005290:Ferric Compounds; C000499:ferric oxide; D002939:Ciprofloxacin; D000535:Aluminum