Guzzinati Roberta, Sarti Elena, Catani Martina, Costa Valentina, Pagnoni Antonella, Martucci Annalisa, Rodeghero Elisa, Capitani Donatella, Pietrantonio Massimiliana, Cavazzini Alberto, Pasti Luisa
University of Ferrara, Department of Chemistry and Pharmaceutical Sciences, Via L. Borsari, 46, 44121, Ferrara, Italy.
Italian National Agency for New Technologies, Energy and Suitable Economic Development (ENEA), R. C. Bologna, Via Martiri di Monte Sole, 4, 40129, Bologna, Italy.
Chemphyschem. 2018 Sep 5;19(17):2208-2217. doi: 10.1002/cphc.201800333. Epub 2018 Jun 20.
The adsorption behavior of neodymium (Nd ) and yttrium (Y ) cations on synthetic FAU zeolite X in its sodium form (NaX) has been investigated by means of macroscopic (adsorption isotherm determination and thermal analysis) and microscopic measurements (including solid-state NMR spectroscopy and X-ray powder diffraction). The multidisciplinary study reveals some unexpected features. Firstly, adsorption constants of cations are not correlated to their ionic radii or hydration enthalpy. The adsorption constant of Y on NaX was indeed about twice that of Nd , which is the opposite of what could be expected based on the size of the cations. In addition, adsorption was accompanied by partial dealumination of the zeolite framework. The extent of dealumination changed depending on the exchanged cations, with the extent being more significant on the Nd-exchanged zeolite than on the Y-exchanged one. The most interesting finding of this study, however, is the presence of supramolecular clusters composed of water, Nd , residual sodium ions, and extra-framework aluminum at the interface of Nd-exchanged zeolite. The hypothesis that these host-guest complexes are responsible of the significantly different behavior exhibited by NaX towards the adsorption/desorption of Nd and Y has been formulated.
通过宏观测量（吸附等温线测定和热分析）和微观测量（包括固态核磁共振光谱和X射线粉末衍射），研究了钕（Nd）和钇（Y）阳离子在钠型合成FAU沸石X（NaX）上的吸附行为。多学科研究揭示了一些意想不到的特征。首先，阳离子的吸附常数与其离子半径或水合焓无关。Y在NaX上的吸附常数实际上约为Nd的两倍，这与基于阳离子大小的预期相反。此外，吸附伴随着沸石骨架的部分脱铝。脱铝程度随交换的阳离子而变化，Nd交换沸石上的脱铝程度比Y交换沸石上的更显著。然而，这项研究最有趣的发现是在Nd交换沸石的界面处存在由水、Nd、残留钠离子和骨架外铝组成的超分子簇。已经提出了这些主客体络合物导致NaX对Nd和Y的吸附/解吸表现出显著不同行为的假设。
