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Crystal Chemistry of the Microporous Zirconosilicate Na6Zr3[Si9O27], a Product of High-Temperature Transformation of Catapleiite, and Its Ag-Exchanged Form

1
Faculty of Geology, Moscow State University, Vorobievy Gory, 119991 Moscow, Russia
2
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, 142432 Moscow, Russia
*
Author to whom correspondence should be addressed.
Minerals 2020, 10(3), 243; https://doi.org/10.3390/min10030243
Received: 20 January 2020 / Revised: 28 February 2020 / Accepted: 5 March 2020 / Published: 7 March 2020
(This article belongs to the Special Issue Zr-minerals)
The crystal structure of the Ag-exchanged form of the zirconosilicate with the simplified formula (Na6-2xCaxx)Zr3[Si9O27] with x < 1 (the idealized formula Na6Zr3[Si9O27]), a product of thermal transformation of catapleiite, ideally Na2Zr[Si3O9]·2H2O, was studied using single crystal X-ray diffraction data. The crystal structure of Na6Zr3[Si9O27] is based on a heteropolyhedral framework built by nine-membered tetrahedral rings [Si9O27] and isolated [ZrO6] octahedra. This zirconosilicate demonstrates high exchange capacity to Ag (experiment with 1 M AgNO3 aqueous solution, 250 °C, 30 days). Its Ag-exchanged form with the simplified formula (Ag5Ca0.5)Zr3[Si9O27] is characterized by a significant distortion of the heteropolyhedral framework and strongly disordered arrangement of extra-framework cations (Ag) which results in the doubling of a parameter of the hexagonal unit cell [a = 23.3462(3), c = 10.10640(10) Å, V = 4770.45(13) Å3] and space group P63cm. Ag+ cations preferably occupy the sites that are close to the Na sites in Na6Zr3[Si9O27]. View Full-Text
Keywords: catapleiite; high-temperature transformation; microporous zirconosilicate; nine-membered Si tetrahedral ring; cyclosilicate; ion exchange; silver; zeolitic properties; crystal structure catapleiite; high-temperature transformation; microporous zirconosilicate; nine-membered Si tetrahedral ring; cyclosilicate; ion exchange; silver; zeolitic properties; crystal structure
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Zubkova, N.V.; Ksenofontov, D.A.; Chukanov, N.V.; Pekov, I.V.; Artamonova, A.A.; Koshlyakova, N.N.; Bychkov, A.Y.; Pushcharovsky, D.Y. Crystal Chemistry of the Microporous Zirconosilicate Na6Zr3[Si9O27], a Product of High-Temperature Transformation of Catapleiite, and Its Ag-Exchanged Form. Minerals 2020, 10, 243.

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