Spectroscopic Investigation of Ciprofloxacin Speciation at the Goethite−Water Interface

Abstract

We investigated ciprofloxacin (a fluoroquinolone antibiotic) speciation as a function of pH in aqueous solution and in the presence of dissolved ferric ions and goethite using ATR-FTIR and UV-vis spectroscopy. The presence of dissolved and surface bound ferric species induced the deprotonation of the ciprofloxacin carboxylic acid group at pH < pKa1. The resultant ciprofloxacin zwitterions appeared to interact via both carboxylate oxygens to form bidentate chelate and bridging bidentate complexes within colloidal iron oxide-ciprofloxacin precipitates and bidentate chelates on the goethite surface. However, the structure of the aqueous ferric-ciprofloxacin complexes remains unclear. Our evidence for bidentate chelates (involving only the carboxylate oxygens) on the goethite surface was distinct from previous IR studies of fluoroquinolone sorption to metal oxides that have proposed surface complexes involving both the keto and the carboxylate groups. We find that the distinct ciprofloxacin surface complex proposed at the goethite-water interface may be a result of differences in metal oxide mineralogy or assignment of the carboxylate antisymmetric stretch in the metal oxide-fluoroquinolone spectra.

Sorption of aromatic hydrocarbons onto montmorillonite as affected by norfloxacin

“…Assignments of the remaining vibrations observed in Fig. 1 are as follows: C O stretch of ketone group (1629 cm −1 ), and coupled carboxylic acid C O stretch ( COOH ) and O-H deformation (ı C OH ) (1274 cm −1 ) [3,4]. The interaction between Nor and K + -montmorillonite was investigated by comparing the spectra of sorbed Nor with those of Nor in solution.…”

“…Thus, their sorption behavior in the environment is significantly different from that of other hydrophobic organic chemicals (HOCs). Past studies examined pH-dependent sorption of antibiotics onto clays [2], aluminum oxides [3,4], and amorphous iron oxides [3], goethite [4], soil and soil minerals [5,6], and carbon nanotubes [7]. The proposed mechanisms included cation exchange and cation bridging [8], surface complexation [3,4], and hydrophobic interaction [7].…”

Trends in the occurrence of human and veterinary antibiotics in the sediments of the Yellow River, Hai River and Liao River in northern China

“…These antibiotics can interact strongly with clay, nature organic matter and metal oxides Karthikeyan, 2005, 2008;Trivedi and Vasudevan, 2007;Mackay and Seremet, 2008). Simon (2005) also found that loosely bound antibiotics are subject to desorption and might be biologically active, which suggests that the sediment may be a pollution source of antibiotics.…”

Coadsorption of Ciprofloxacin and Cu(II) on Montmorillonite and Kaolinite as Affected by Solution pH

“…Current understanding of Cip and tetracycline sorption to soils and soil minerals has revealed similarities in the mechanisms, with both compound classes being sorbed onto aluminosilicate clays either via cation exchange and cation bridging (3,(8)(9)(10) or via surface complexation (4,5,11,12). However, the exact mechanism of surface complexation is unknown.…”