Formation of Supramolecular Clusters at the Interface of Zeolite X Following the Adsorption of Rare‐Earth Cations and Their Impact on the Macroscopic Properties of the Zeolite. Issue 17 (20th June 2018)

• Record Type: Journal Article
• Authors: Guzzinati, Roberta; Sarti, Elena; Catani, Martina; Costa, Valentina; Pagnoni, Antonella; Martucci, Annalisa; Rodeghero, Elisa; Capitani, Donatella; Pietrantonio, Massimiliana; Cavazzini, Alberto; Pasti, Luisa
• Is Part Of: Chemphyschem. Volume 19:Issue 17(2018)
• Page Start: 2208
• Page End: 2217
• Publication Date: 2018-06-20
• Subjects: Adsorption -- exchange interactions -- rare-earths elements -- supramolecular clusters -- zeolites; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201800333
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: The adsorption behavior of neodymium (Nd 3+ ) and yttrium (Y 3+ ) 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 3+ on NaX was indeed about twice that of Nd 3+, 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 3+, 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 3+ and Y 3+ has been formulated. Abstract : Exchanged cation : Adsorption of rare‐earth elements on hydrophilic zeolites was investigated. Exploiting both macroscopic and microscopic techniques, it was found that dealumination occurs during the cation exchange process. The extra‐framework aluminum with water, Nd 3+, and residual sodium ions form supramolecular clusters on the surface of the Nd‐exchanged zeolite.