On the nature of Pb species in Pb-(over)exchanged zeolite: a combined experimental and theoretical study
On the nature of Pb species in Pb-(over)exchanged zeolite: a combined experimental and theoretical study
Roos, D. P.; Scheinost, A.; Churakov, S. V.; Nagashima, M.; Cametti, G.
Abstract
Structural properties of Pb-exchanged zeolites are of interest because of their applications in environmental remediation and in industrial processes. In this study, we report on a Pb-exchanged aluminosilicate zeolite (Pb-STI), with particular focus on the cationic species, which form inside the zeolitic pores as a result of the exchange experiments. The produced
zeolite had chemical composition Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O, indicating a Pb2+ overexchange of approximately 50%. The STI framework maintained the Fmmm space group characteristic of the type material. However, the extraframework occupants, Pb2+, H2O and OH-, were characterized by a strong positional-disorder. The latter was resolved and
interpreted combining Extended X-ray Absorption Fine Structure (EXAFS) analysis with Molecular Dynamics (MD) simulations. On average, Pb2+ ions are coordinated by 2 OH- and
1 H2O at distances < 2.5 Å, whereas bonds to framework oxygen-atoms were found only at longer distances (> 2.8 Å). Pb2+ adopts mainly a sided distorted coordination, indicating a
stereochemical activity of the lone pair electrons. The obtained results were compared with those of other mono-cationic forms of STI zeolites. Based on the analysis of the framework
distortion experienced after the incorporation of different metal ions, considerations are drawn on the potential effect of Pb2+ on the thermal stability of STI framework type zeolites.
Keywords: XAFS; Zeolite; XRD; Molecular dynamics; DFT
Beteiligte Forschungsanlagen
- Rossendorf Beamline an der ESRF DOI: 10.1107/S1600577520014265
Verknüpfte Publikationen
- DOI: 10.1107/S1600577520014265 is cited by this (Id 33007) publication
-
Microporous and Mesoporous Materials 327(2021), 111444
DOI: 10.1016/j.micromeso.2021.111444
Cited 1 times in Scopus
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