Role of Cation鈥揥ater Disorder during Cation Exchange in Small-Pore Zeolite Sodium Natrolite

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• 作者：Yongmoon Lee ; Jun-Sik Lee ; Chi-Chang Kao ; Ji-Ho Yoon ; Thomas Vogt ; Yongjae Lee
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 8, 2013
• 年：2013
• 卷：117
• 期：31
• 页码：16119-16126
• 全文大小：340K
• 年卷期：v.117,no.31(August 8, 2013)
• ISSN：1932-7455

文摘

By combining X-ray diffraction with oxygen K-edge absorption spectroscopy we track changes occurring during the K⁺鈥揘a⁺ cation exchange of Na-natrolite (Na-NAT) as tightly bonded Na⁺ cations and H₂O molecules convert into a disordered K⁺鈥揌₂O substructure and the unit cell expands by ca. 10% after 50% cation exchange. The coordination of the confined H₂O and nonframework cations change from a tetrahedral configuration, similar in ice I_h, with Na⁺ near the middle of the channels in Na-NAT to two-bonded configuration, similar in bulk water, and K⁺ located near the walls of the framework in K-NAT. This is related to the enhanced ion-exchange properties of K-NAT, which, in marked contrast to Na-NAT, permits the exchange of K⁺ by a variety of uni-, di-, and trivalent cations.