제올라이트 Y (Si/Al = 1.56) 골격 내의 Ca2+과 Cs+ 이온의 자리 경쟁 및 그들의 결정학적 연구

The present work was performed in order to study the effect of competing cation of Ca2+ ion on ion exchange of Cs+ on zeolite Y (Si/Al = 1.56). Three single-crystals of fully dehydrated and partially Cs+-exchanged zeolites Y (Si/Al = 1.56) were prepared by the flow method using mixed ion-exchange solutions. The CsNO3 : Ca(NO3)2 molar ratios of the ion exchange solution were 1 : 1 (crystal 1), 1 : 100 (crystal 2), and 1 : 250 (crystal 3) with a total concentration of 0.05 M. The single-crystals were then vacuum dehydrated at 723 K and 1 × 10-4 Pa for 2 days. The structures of the crystals were determined by single-crystal synchrotron X-ray diffraction technique in the cubic space group Fd3m, at 100(1) K. The unit-cell formulas of crystals 1, 2, and 3 were |Cs21Ca27|[Si117Al75O384]-FAU, |Cs2Ca36.5|[Si117Al75O384]-FAU, and |Cs1Ca37|[Si117Al75O384]-FAU, respectively. In all three crystals, the Ca2+ ions preferred to occupy site I in the D6Rs, with the remainder occupying sites I’, II’, and II. On the other hand, the significant differences in the fractional distribution of Cs+ ions are observed depending on the intial Cs+ concentrations in given ion exchange solution. In Crystal 1, Cs+ ion are located at sites II’, II, III, and III’, and in crystal 2, at sites II, IIIa, and IIIb. In crystal 3, Cs+ ions are only located at sites IIIa and IIIb. The degree of Cs+ ion exchange decreased sharply from 28.0 to 2.7 to 1.3 % as the initial Ca2+ concentration increases and the Cs+ content decreases.