title: Insight to ternary complexes of co-adsorption of norfloxacin and Cu(II) onto montmorillonite at different pH using EXAFS.
abstract: Co-adsorption of norfloxacin (Nor) and Cu(II) on montmorillonite at pH 4.5, 7.0 and 9.0 was studied by integrated batch adsorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy. Under such pH conditions the dominant species of Nor are cation (Nor(+)), zwitterion (Nor(±)), and anion (Nor(-)), respectively. Results indicated that Nor sorption decreased with an increase of solution pH. The presence of Cu(II) slightly suppressed the Nor(+) sorption at pH 4.5, while increased Nor(±) and Nor(-)sorption on montmorillonite at pH 7.0 and 9.0, respectively. In contrast, Nor increased Cu(II) adsorption at pH 4.5, but had little effect on the adsorption of Cu(II) on montmorillonite at pH 7.0 and 9.0. Spectroscopic results showed that, at pH 4.5, Nor(+) was sorbed on montmorillonite by the formation of outer-sphere montmorillonite-Nor-Cu(II) ternary surface complex. At pH 7.0, montmorillonite-Nor-Cu(II) and montmorillonite-Cu(II)-Nor ternary surface complexes co-exist. At pH 9.0, montmorillonite-Cu(II)-Nor ternary surface complex was likely formed, which was different to Cu(II)(Nor)(2) precipitate of the solution.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Pei
authors.forename: Xiao-Quan
authors.initials: XQ
authors.lastname: Shan
authors.forename: Shu-Zhen
authors.initials: SZ
authors.lastname: Zhang
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Kong
authors.forename: Bei
authors.initials: B
authors.lastname: Wen
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Li-Rong
authors.initials: LR
authors.lastname: Zheng
authors.forename: Ya-Ning
authors.initials: YN
authors.lastname: Xie
authors.forename: Koen
authors.initials: K
authors.lastname: Janssens
mesh_terms: D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009643:Norfloxacin / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D001546:Bentonite; D003300:Copper; D009643:Norfloxacin