Study on coordination structure of Re adsorbed on Mg-Al layered double hydroxide using X-ray absorption fine structure.
Study on coordination structure of Re adsorbed on Mg-Al layered double hydroxide using X-ray absorption fine structure.
复制标题
利用X射线吸收精细结构研究Mg-Al层状双氢氧化物吸附Re的配位结构。
DOI：
10.1007/s10934-018-0634-z
复制
发表时间：
2019
影响因子：
2.6
通讯作者：
B.
中科院分区：
文献类型：
--
作者：
Tanaka;K.;Kozai;N.;Ohnuki;T. and Grambow;B.
水滑石类层状双氢氧化物（LDHs）多孔材料已被用于从溶液中去除阴离子污染物。然而，由于缺乏光谱研究，吸附在LDHs上的阴离子的局部配位结构还没有完全了解。在这项研究中，我们利用X-射线吸收精细结构光谱来澄清镁铝LDH作为Tc的替代物的Re的配位结构。在不同浓度的NaCl、NaNO 3和Na 2SO 4水溶液中，研究了煅烧和未煅烧Mg-Al LDHs对ReO 4 −的吸附性能。通过化学成分分析、扫描电镜（SEM）和比表面积等手段对煅烧前后的Mg-Al水滑石进行了表征。焙烧后的Mg-Al LDH比未焙烧的LDH有更高的吸附量。ReO 4 −的吸附是可逆的，并且随着竞争阴离子（如Cl−、NO3−或SO 42 −）浓度的增加而减少。铼的LIII边X射线吸收近边结构表明，在嵌入Mg-Al LDH的过程中，既没有发生氧化还原反应，也没有发生配位结构的变化。Re LIII边扩展X射线吸收精细结构分析表明，ReO 4 −以外层络合物形式吸附在Mg-Al LDH上。所观察到的Re吸附-脱附行为，这是敏感的竞争阴离子的存在下，是与形成外球络合物。
Porous materials of hydrotalcite-like layered double hydroxides (LDHs) have been used for removal of anionic contaminants from solution. However, local coordination structures of anions adsorbed on LDHs are not fully understood because of the lack of spectroscopic studies. In this study, we utilized X-ray absorption fine structure spectroscopy to clarify the coordination structure of Re in Mg–Al LDH as a surrogate of Tc. Adsorption experiments of ReO4−on calcined and uncalcined Mg–Al LDHs were conducted in aqueous solutions with different concentrations of NaCl, NaNO3, and Na2SO4. The tested calcined and uncalcined Mg–Al LDHs were characterized by chemical composition analysis, scanning electron microscopy (SEM), and BET surface area. Calcined Mg–Al LDH showed much higher adsorption than uncalcined one. The adsorption of ReO4−was reversible, and decreased with increasing concentration of competing anions like Cl−, NO3−, or SO42−. Rhenium LIII-edge X-ray absorption near edge structure suggested that neither redox reaction nor change of coordination structure occurred during intercalation of Re into Mg–Al LDH. Analysis of Re LIII-edge extended X-ray absorption fine structure indicated that ReO4−was adsorbed as an outer-sphere complex on Mg–Al LDH. The observed Re adsorption–desorption behavior, which was sensitive to the presence of competing anions, was consistent with the formation of outer sphere-complex.