钠基膨润土负载零价锌去除水溶液中U(Ⅵ)的效果及机理

    Removal of U(Ⅵ) From Aqueous Solution by Supported Zerovalent Zinc on GMZ-Sodium Bentonite and Investigation of Mechanism

    • 摘要: 制备了零价锌(ZVZ)、钠基膨润土(Na-bent)负载的零价锌(ZVZ/Na-bent)和AlCl3柱撑改性钠基膨润土负载的零价锌(ZVZ/Al/Na-bent),并研究了ZVZ、ZVZ/Na-bent、ZVZ/Al/Na-bent和Na-bent对水溶液中U(Ⅵ)的吸附效果。采用X射线粉末衍射(XRD)、扫描电镜(SEM)、X射线能谱分析(EDS)、X射线光电子能谱(XPS)对四种吸附剂吸附U(Ⅵ)前后进行了表征,研究了四种吸附剂吸附U(Ⅵ)的机理。结果表明:ZVZ呈片状堆叠结构,掺杂膨润土后能明显消除ZVZ堆叠现象。ZVZ/Na-bent和ZVZ/Al/Na-bent对铀的最大吸附量约为250 mg/g,ZVZ的最大吸附量能达到505 mg/g。采用Langmuir和Freundlich模型分析发现,U(Ⅵ)在四种吸附剂上的吸附行为符合Langmuir模型,热力学研究发现吸附过程的ΔS、ΔH为正值,ΔG<0。U(Ⅵ)的去除机理主要为化学还原、水解沉淀和离子交换。

       

      Abstract: It is the first time that zero-valent zinc(ZVZ), sodium bentonite(Na-bent) supported zero-valent zinc(ZVZ/Na-bent) and AlCl3 solution pillars modified Na-bent supported zero valent zinc(ZVZ/Al/Na-bent) were prepared in our experiment. The effects on removing U(Ⅵ) from aqueous solution of ZVZ, Na-bent, ZVZ/Na-bent and ZVZ/Al/Na-bent were studied. The U(Ⅵ) adsorption mechanism of above four adsorbents was investigated by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS) and X-ray photoelectron spectroscopy(XPS). The results show that ZVZ has a layered stack structure, which can be significantly eliminated by doping bentonite. The maximum adsorption capacity of uranium by ZVZ/Na-bent and ZVZ/Al/Na-bent are about 250 mg/g, while the adsorption capacity of ZVZ can be as high as 505 mg/g. All of the adsorption processes of the four adsorbents have positive ΔS, ΔH and negative ΔG, which are agreed well with the Langmuir model. The removal mechanism of U(Ⅵ) is mainly chemical reduction, hydrolytic precipitation and ion exchange.

       

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