College of Environmental Science and Engineering, Hunan University, Changsha, 410082, Hunan, China.
Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, Hunan, China.
Environ Geochem Health. 2024 Apr 8;46(5):153. doi: 10.1007/s10653-024-01927-2.
The environmental fate and risks of ciprofloxacin (CIP) in the subsurface have raised intensive concerns. Herein, the transport behaviors of CIP in both saturated quartz sand and sand/multi-walled carbon nanotubes (MWCNTs) mixtures under different solution ionic strength of the solution and coexisting cation types were investigated. Batch adsorption experiments highlighted growing adsorptive capacity for CIP with the increasing content of MWCNTs in the MWCNTs-quartz sand mixtures (from 0.5% to 1.5%, w/w). Breakthrough curves (BTCs) of CIP in the MWCNTs-quartz sand mixtures were well fitted by the two-site chemical nonequilibrium model (R > 0.833). The estimated retardation factors for CIP increased from 9.68 to 282 with growing content of MWCNTs in the sand column, suggesting the presence of MWCNTs significantly inhibited the transport of CIP in saturated porous media. Moreover, the values of retardation factors are negatively correlated with the ionic strength and higher ionic strength could facilitate the transport of CIP in the saturated porous media. Compared with monovalent cations (Na), the presence of divalent cations (Ca) significantly facilitated the transport of CIP in the columns due to the complexation between CIP and Ca as well as deposition of MWCNTs aggregates on the sand surface. Results regarding CIP retention in columns indicated that MWCNTs could enhance the accumulation of CIP in the layers close to the influent of sand columns, while they could hinder upward transport of CIP to the effluent. This study improves our understanding for transport behaviors and environmental risk assessments of CIP in the saturated porous media with MWCNTs.
环丙沙星（CIP）在地下环境中的归宿和风险引起了广泛关注。本研究考察了不同溶液离子强度和共存阳离子类型下，CIP 在饱和石英砂和砂/多壁碳纳米管（MWCNTs）混合物中的迁移行为。批吸附实验表明，随着MWCNTs-石英砂混合物中 MWCNTs 含量（从 0.5%到 1.5%，w/w）的增加，CIP 的吸附容量逐渐增大。MWCNTs-石英砂混合物中 CIP 的穿透曲线（BTCs）通过双位点化学非平衡模型（R>0.833）得到了很好的拟合。随着砂柱中 MWCNTs 含量的增加，CIP 的阻滞因子从 9.68 增加到 282，表明 MWCNTs 的存在显著抑制了 CIP 在饱和多孔介质中的迁移。此外，阻滞因子的值与离子强度呈负相关，较高的离子强度有利于 CIP 在饱和多孔介质中的迁移。与单价阳离子（Na）相比，由于 CIP 与 Ca 的络合作用以及 MWCNTs 聚集体在砂表面的沉积作用，二价阳离子（Ca）的存在显著促进了 CIP 在柱中的迁移。关于 CIP 在柱中保留的结果表明，MWCNTs 可以增强 CIP 在靠近砂柱入口层的积累，同时阻碍 CIP 向上向出口的迁移。本研究提高了我们对 MWCNTs 存在下 CIP 在饱和多孔介质中的迁移行为和环境风险评估的认识。
