title: Macroscopic and molecular approaches of enrofloxacin retention in soils in presence of Cu(II).
abstract: The co-adsorption of copper and the fluoroquinolone antibiotic enrofloxacin (ENR) at the water-soil interface was studied by means of batch adsorption experiments, and extended X-ray absorption fine structure (EXAFS) spectroscopy. The system was investigated over a pH range between 6 and 10, at different contact times, ionic strengths, and ENR concentrations. Adsorption coefficient - Kd - was determined at relevant environmental concentrations and the value obtained in water at a ionic strength imposed by the soil and at soil natural pH was equal to 0.66Lg(-1). ENR adsorption onto the soil showed strong pH dependence illustrating the influence of the electrostatic interactions in the sorption processes. The simultaneous co-adsorption of ENR and Cu(II) on the soil was also investigated. The presence of Cu(II) strongly influenced the retention of the antibiotic, leading to an increase up to 35% of adsorbed ENR amount. The combined quantitative and spectroscopic results showed that Cu(II) and ENR directly interacted at the water-soil interface to form ternary surface complexes. Cu K-edge EXAFS data indicated a molecular structure where the carboxylate and carbonyl groups of ENR coordinate to Cu(II) to form a 6-membered chelate ring and where Cu(II) bridges between ENR and the soil surface sites. Cu(II) bonds bidentately to the surface in an inner-sphere mode. Thus, the spectroscopic data allowed us to propose the formation of ternary surface complexes with the molecular architecture soil-Cu(II)-ENR.
authors: Institut de Chimie Moléculaire de Reims (ICMR, UMR CNRS 7312), Groupe Chimie de Coordination, Université de Reims Champagne-Ardenne, F-51687 Reims Cedex 2, France.
authors: Mareen
authors: M
authors: Graouer-Bacart
authors: Stéphanie
authors: S
authors: Sayen
authors: Emmanuel
authors: E
authors: Guillon
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000737:chemistry*; D007700:Kinetics; D012989:Soil Pollutants / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D012989:Soil Pollutants; D000077422:Enrofloxacin; D003300:Copper
keywords: Adsorption; Co-adsorption; Copper; EXAFS; Enrofloxacin; Soil