Li Jia, Zhang Hua
Key Laboratory of Coastal Environmental Process and Ecology Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China; University of Chinese Academy of Sciences, Beijing, China.
Key Laboratory of Coastal Environmental Process and Ecology Remediation, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, China.
Chemosphere. 2016 Dec;164:156-163. doi: 10.1016/j.chemosphere.2016.08.100. Epub 2016 Aug 30.
To reveal the kinetics and mechanisms of antibiotic adsorption/desorption processes, batch and stirred flow chamber (SFC) experiments were carried out with oxytetracycline (OTC) on two marine sediments. The OTC adsorption capacities of the marine sediments were relatively weak and related to their organic carbon (OC) and contents of fine particles. Sorption isotherms of OTC on marine sediment can be well described by both the Langmuir and Freundlich models. Langmuir adsorption maxima (q) and Freundlich distribution coefficients (K) increased with the decrease of salinity and pH, which indicated the importance of variable charged sites on sediment surfaces. A second order kinetic model successfully described adsorption and desorption kinetics of OTC and well reproduced the concentration change during stop-flow. The adsorption kinetic rates (k) for OTC under different experimental conditions ranged from 2.00 × 10 to 1.97 × 10 L (mg min). Results of SFC experiments indicated that diffusive mass transfer was the dominant mechanism of the time-dependent adsorption of OTC and its release from marine sediment was mildly hysteretic. The high desorption percentage (43-75% for LZB and 58-75% for BHB) implied that binding strength of OTC on two marine sediments was weak. In conclusion, marine sediment characteristics and environmental factors such as salinity, pH, and flow rate are critical factors determine extent of OTC sorption on marine sediment and need to be incorporated in modeling fate and transport of OTC in marine environment.
为揭示抗生素吸附/解吸过程的动力学和机制，采用土霉素（OTC）在两种海洋沉积物上进行了批次和搅拌流室（SFC）实验。海洋沉积物对OTC的吸附能力相对较弱，且与它们的有机碳（OC）和细颗粒含量有关。OTC在海洋沉积物上的吸附等温线可以用Langmuir模型和Freundlich模型很好地描述。Langmuir吸附最大值（q）和Freundlich分配系数（K）随着盐度和pH值的降低而增加，这表明沉积物表面可变电荷位点的重要性。二级动力学模型成功地描述了OTC的吸附和解吸动力学，并很好地再现了停流期间的浓度变化。不同实验条件下OTC的吸附动力学速率（k）范围为2.00×10至1.97×10 L/（mg·min）。SFC实验结果表明，扩散传质是OTC随时间变化吸附的主要机制，其从海洋沉积物中的释放具有轻微滞后性。高解吸百分比（LZB为43 - 75%，BHB为58 - 75%）表明OTC在两种海洋沉积物上的结合强度较弱。总之，海洋沉积物特性以及盐度、pH值和流速等环境因素是决定OTC在海洋沉积物上吸附程度的关键因素，需要纳入OTC在海洋环境中归宿和迁移的模型中。
