| EXAFS研究Zn在δ-MnO2上的吸附-解吸机理 |
| 摘要点击 1898 全文点击 1793 投稿时间：2002-11-27 修订日期：2003-02-14 |
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| 中文关键词 EXAFS Zn δMnO2 吸附机制 吸附可逆性 |
| 英文关键词 EXAFS Zn δ-MnO2 adsorption mechanism adsorption reversibility |
| 作者 | 单位 | | 潘纲 | 中国科学院生态环境研究中心环境水质学国家重点实验室,北京,100085 | | 李贤良 | 中国科学院生态环境研究中心环境水质学国家重点实验室,北京,100085 | | 秦延文 | 中国科学院生态环境研究中心环境水质学国家重点实验室,北京,100085 | | 胡天斗 | 中国科学院高能物理研究所同步辐射室,北京,100039 | | 吴自玉 | 中国科学院高能物理研究所同步辐射室,北京,100039 | | 谢亚宁 | 中国科学院高能物理研究所同步辐射室,北京,100039 |
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| 中文摘要 |
| 用延展X-ray吸收精细结构光谱(EXAFS)研究了重金属Zn(Ⅱ)在δ-MnO2上吸附产物的微观结构及其吸附机制.在pH 5.50,0.1mol/L NaNO3介质中,吸附在δ-MnO2表面上Zn(Ⅱ)以六配位的水合离子八面体形式存在.水合锌离子八面体从δ-MnO2层状结构的空位上下方,与δ-MnO2的结构单元MnO6八面体通过共用O原子结合,形成角-角结合的弱吸附,Zn-O平均原子间距为(2.071±0.007)A(n=3),Zn-Mn平均原子间距为(3.528±0.006)A(n=3).在同一条等温线上随着吸附量增加,以角-角结合的弱吸附形式基本上没有变化.宏观的吸附-解吸实验结果显示Zn(Ⅱ)在δ-MnO2上的吸附可逆性很高,解吸等温线和吸附等温线几乎重合在一起EXAFS结果从分子水平表明,Zn(Ⅱ)在δ-MnO2上的高吸附可逆性是由角-角形式弱吸附所导致的. |
| 英文摘要 |
| Microscopic structures of Zn(Ⅱ) surface complexes adsorbed at a δ-MnO2 water interface were studied using extended X ray absorption fine structure (EXAFS) spectroscopy. In a 0.1mol/L NaNO3 solution of pH 5.50, Zn(Ⅱ) was adsorbed onto the solid surface in the form of octahedral hydrous Zn(Ⅱ) ions. The octahedral Zn(Ⅱ) was linked to the structural unit of octahedral MnO6 of the δ-MnO2 surface by sharing the O atoms. The average bond length of RZn-O was (2.071±0.007)A ( n =3) and the Zn Mn atomic distance was (3.528±0.006)A ( n =3), which corresponded to a corner sharing linkage adsorption mode (weaker adsorption). Macroscopic adsorption desorption isotherm experiments showed that, in contrast to that of Zn manganite, adsorption of Zn(Ⅱ) on δ-MnO2 was highly reversible and no apparent adsorption hysteresis was observed. EXAFS results indicated that the microscopic mechanism for the high adsorption reversibility was corresponded to the weak adsorption sites of corner sharing linkage between the adsorbate and adsorbent polyhedra. |
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