title: Sorption of the antimicrobial ciprofloxacin to aluminum and iron hydrous oxides.
abstract: 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.
authors.affiliation: Department of Biological Systems Engineering, Environmental Chemistry and Technology Program, University of Wisconsin, Madison 53706, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Gu
authors.forename: K G
authors.initials: KG
authors.lastname: Karthikeyan
mesh_terms: 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
chemical_list: D000900:Anti-Bacterial Agents; D005290:Ferric Compounds; C000499:ferric oxide; D002939:Ciprofloxacin; D000535:Aluminum