title: Enrofloxacin sorption on smectite clays: effects of pH, cations, and humic acid.
abstract: Enrofloxacin (ENR) occurs widely in natural waters because of its extensive use as a veterinary chemotherapeutic agent. To improve our understanding of the interaction of this emerging contaminant with soils and sediments, sorption of ENR on homoionic smectites and kaolinite was studied as a function of pH, ionic strength, exchangeable cations, and humic acid concentration. Batch experiments and in situ ATR-FTIR analysis suggested multiple sorption mechanisms. Cation exchange was a major contributor to the sorption of cationic ENR species on smectite. The decreased ENR sorption with increasing ionic strength indicated the formation of outer-sphere complexes. Exchangeable cations significantly influenced the sorption capacity, and the observed order was Cs<Ca<K. The peak shifts of the COO(-) stretch, coupled CO stretch and OH deformation, and the result of irreversible desorption FTIR spectra indicated that OH of the carboxyl group was involved in the formation of inner-sphere surface complexes. The XRD analysis confirmed that interlayer intercalation is an important contributor to ENR sorption, while humic acid had a negligible contribution to the interlayer intercalation. The results of this study provide new insight into the molecular mechanisms of ENR sorption on clay minerals.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yan
authors.forename: Shan
authors.initials: S
authors.lastname: Hu
authors.forename: Chuanyong
authors.initials: C
authors.lastname: Jing
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates; D000970:Antineoplastic Agents / Q000302:isolation & purification; D002412:Cations; D000077215:Clay; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000302:isolation & purification*; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D009994:Osmolar Concentration; D017640:Silicates / Q000737:chemistry*; D012989:Soil Pollutants / Q000302:isolation & purification
chemical_list: D000538:Aluminum Silicates; D000970:Antineoplastic Agents; D002412:Cations; D024841:Fluoroquinolones; D006812:Humic Substances; D017640:Silicates; D012989:Soil Pollutants; D000077422:Enrofloxacin; C033214:Smectite; D000077215:Clay