两性修饰蒙脱石对水中镉和四环素的吸附性能研究

Adsorption of Cd( Ⅱ ) and tetracycline by amphoteric surfactants modified montmorillonite

以两性表面活性剂十二烷基二甲基甜菜碱(BS-12)为改性剂制备两性修饰蒙脱石(BS-Mt),在单一体系和Cd^(2+)+TC复合体系中研究其对Cd^(2+)和四环素的吸附行为,同时利用XRD、FTIR、TG-DSC和Zeta电位对两性修饰蒙脱石进行表征分析.表征结果显示,BS-12已成功负载到蒙脱石上,改性后材料表面的负电荷增加;吸附实验结果显示,BS-Mt对Cd^(2+)和四环素的吸附量较Mt有较大的提高;其中BS-Mt对Cd^(2+)的吸附行为符合Langmuir等温吸附模型和准一级动力学模型,吸附机理主要为电荷吸附和螯合作用;BS-Mt对四环素的吸附随p H的升高而降低,吸附行为符合Freundlich等温吸附模型和准二级动力学模型,吸附机理主要为电荷吸附和物理吸附.在Cd^(2+)+TC复合体系中Cd^(2+)和TC会形成复合物,Mt和BS-Mt对四环素和Cd^(2+)的吸附量比单一体系增加.

In this study,amphoteric surfactant dodecyl dimethyl betaine（ BS-12） was used to modify montmorillonite（ BS-Mt） and the adsorption of Cd^2＋and tetracycline in the single Cd^2＋or tetracycline（ TC） system,Cd^2＋plus TC complex system,by the prepared adsorbents were investigated. The Characteristics of the modified montmorillonite were performed by using X-ray diffraction（ XRD）,Fourier transform infrared spectroscopy（ FTIR）,Thermogravimetric differential thermal analysis（ TG-DSC） and Zeta potential analysis. It was found that BS-12 had intercalated successfully into montmorillonite interlayer. The introduction of BS-12 led to more negative charges on the surface of montmorillonite. In the p H ranging from 2 to 9,solution p H had a significant impact on the adsorption of both Cd^2＋and TC. For the adsorption behavior for Cd^2＋,pseudo-first-order kinetics and Langmuir adsorption model fitted the experimental data well. the adsorption of Cd^2＋was mainly attributed to chelation and electrostatic attraction. However,the adsorption of TC could be well described by pseudo-second-order kinetics and Freundlich isotherm,and the adsorption of TC were mainly due to physical adsorption and electrostatic attraction. In the Cd^2＋plus TC complex system,the adsorption for Cd^2＋and TC is higher than that in single systems. Overall,BS-Mt had superiority over Mt for the adsorption of both Cd^2＋and tetracycline,suggesting it could be a promising adsorbent in the application of treating wastewater containing Cd^2＋ and tetracycline.