Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Illinois State Water Survey, 2204 Griffith Drive, Champaign, IL 61820, USA.
J Colloid Interface Sci. 2014 Aug 15;428:63-72. doi: 10.1016/j.jcis.2014.04.034. Epub 2014 Apr 24.
Fluoroquinolone (FQ) antibacterials are aquatic contaminants of emerging concern (CEC), and adsorption to mineral surfaces is expected to play an important role in the fate, transport, and treatment of FQs. This study characterizes and models the adsorption of a zwitterionic FQ, ofloxacin (OFX), to goethite (α-FeOOH) over a wide range of pH (3-11), OFX concentration (20-500 μM), and electrolyte compositions (0.001-0.1M NaCl and NaClO4). Comparing OFX adsorption to structural analogues demonstrates that the carboxylate group is essential for binding to goethite. ATR-FTIR measurements indicate that FQs complex to goethite surfaces through carboxylate and carbonyl oxygen atoms, and that ClO4(-) co-adsorbs with OFX. Adsorption of the zwitterionic OFX increases with increasing ionic strength and is enhanced in NaClO4 relative to NaCl electrolyte, whereas adsorption of a non-zwitterionic analogue is insensitive to ionic strength. A CD-MUSIC (charge distribution-multisite complexation) model, incorporating multiple modes of surface complexation constrained by spectroscopic measurements and the crystallographic distribution of goethite surface sites, yields accurate predictions over wide-ranging solution conditions. According to the model, OFX adsorbs predominantly by inner-sphere complexation on terminal surfaces of the rod-shaped goethite crystals in NaCl electrolyte, and OFX-ClO4(-) ion pairing in NaClO4 induces formation of additional inner- and outer-sphere surface complexes on multiple crystal faces of goethite.
氟喹诺酮 (FQ) 类抗菌药物是具有新兴关注的水生污染物 (CEC)，预计它们在 FQ 的命运、迁移和处理方面会吸附到矿物表面。本研究通过广泛的 pH 值（3-11）、OFX 浓度（20-500 μM）和电解质组成（0.001-0.1M NaCl 和 NaClO4）来描述和模拟两性离子 FQ，氧氟沙星（OFX）在针铁矿（α-FeOOH）上的吸附情况。将 OFX 的吸附与结构类似物进行比较表明，羧酸基团对于与针铁矿结合是必不可少的。ATR-FTIR 测量表明 FQs 通过羧酸根和羰基氧原子与针铁矿表面结合，ClO4(-)与 OFX 共同吸附。两性离子 OFX 的吸附随着离子强度的增加而增加，并且在 NaClO4 电解质中相对于 NaCl 增强，而非两性离子类似物的吸附对离子强度不敏感。CD-MUSIC（电荷分布-多配位体络合）模型，结合了由光谱测量和针铁矿表面位点的晶体分布约束的多种表面络合模式，在广泛的溶液条件下可进行准确预测。根据该模型，OFX 在 NaCl 电解质中主要通过棒状针铁矿晶体末端表面的内球络合吸附，而 OFX-ClO4(-)离子对在 NaClO4 中诱导了多个针铁矿晶面上额外的内球和外球表面络合的形成。
