Abstract：
There is little information on how widespread surfactants affect the adsorption of norfloxacin (NOR) onto iron oxide minerals. In order to elucidate the effects of various surfactants on the adsorption characteristics of NOR onto typical iron oxides, we have explored the different influences of sodium dodecylbenzene sulfonate (SDBS), an anionic surfactant, and didodecyldimethylammonium bromide (DDAB), a cationic surfactant, on the interactions between NOR and ferrihydrite under different solution chemistry conditions. Interestingly, SDBS facilitated NOR adsorption, whereas DDAB inhibited NOR adsorption. The adsorption-enhancement effect of SDBS was ascribed to the enhanced electrostatic attraction, the interactions between the adsorbed SDBS on ferrihydrite surfaces and NOR molecules, and the bridging effect of SDBS between NOR and iron oxide. In comparison, the adsorption-inhibition effect of DDAB owning to the adsorption site competitive adsorption between NOR and DDAB for the effective sites as well as the steric hindrance between NOR-DDAB complexes and the adsorbed DDAB on ferrihydrite surfaces. Additionally, the magnitude of the effects of surfactants on NOR adsorption declined with increasing pH values from 5.0 to 9.0, which was related to the amounts of surfactant binding to ferrihydrite surfaces. Moreover, when the background electrolyte was Ca2+, the enhanced effect of SDBS on NOR adsorption was caused by the formation of NOR-Ca2+-SDBS complexes. The inhibitory effect of DDAB was due to the DDAB coating on ferrihydrite, which undermined the cation-bridging effect. Together, the findings from this work emphasize the essential roles of widely existing surfactants in controlling the environmental fate of quinolone antibiotics.
摘要：
关于广泛的表面活性剂如何影响诺氟沙星（NOR）在氧化铁矿物上的吸附的信息很少。为了阐明各种表面活性剂对NOR在典型氧化铁上的吸附特性的影响,我们探索了十二烷基苯磺酸钠（SDBS）的不同影响，阴离子表面活性剂，和二十二烷基二甲基溴化铵（DDAB），阳离子表面活性剂，在不同溶液化学条件下，NOR与水铁矿之间的相互作用。有趣的是,SDBS促进NOR吸附，而DDAB抑制NOR吸附。SDBS的吸附增强效果归因于增强的静电吸引力，水铁矿表面吸附的SDBS与NOR分子之间的相互作用，以及SDBS在NOR和氧化铁之间的桥接作用。相比之下,DDAB的吸附抑制作用归因于NOR和DDAB之间对有效位点的竞争吸附以及NOR-DDAB复合物与吸附在水铁矿表面的DDAB之间的空间位阻。此外,表面活性剂对NOR吸附的影响程度随pH值从5.0增加到9.0而下降，这与表面活性剂与水铁矿表面结合的量有关。此外，当背景电解质为Ca2+时，SDBS对NOR吸附的增强作用是由NOR-Ca2-SDBS配合物的形成引起的。DDAB的抑制作用是由于DDAB涂层在水铁矿上的作用，这破坏了阳离子桥接效应。一起,这项工作的发现强调了广泛存在的表面活性剂在控制喹诺酮类抗生素的环境命运中的重要作用。
