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Crystallographic Study on the Selectivity and Distribution of Sr2+ Ions Within Zeolite A In the Presence of Competing Na+ Ions in Aqueous Exchange Solution

Na+ 경쟁이온이 존재하는 수용액에서 Zeolite A 내 Sr2+ 이온의 선택성 및 분포에 관한 결정학적 연구

  • kim, Hu Sik (Department of Applied Chemistry, Andong National University) ;
  • Park, Jong Sam (Department of Radiologic Technology, Daegu Health College) ;
  • Lim, Woo Taik (Department of Applied Chemistry, Andong National University)
  • 김후식 (안동대학교 응용화학과) ;
  • 박종삼 (대구보건대학교 방사선과) ;
  • 임우택 (안동대학교 응용화학과)
  • Received : 2022.02.24
  • Accepted : 2022.03.12
  • Published : 2022.03.31

Abstract

To study the properties of Sr2+ exchange into zeolite A with increasing the molar concentration of Na+ in given exchange solution, four single crystals of fully dehydrated Sr2+- and Na+- exchanged zeolite A were prepared by the bath method using mixed ion-exchange solutions. The Sr(NO3)2:NaNO3 molar rations of the ion exchange solution were 1:1(crystal 1), 1:100(crystal 2), 1:250(crystal 3), and 1:500 (crystal 4), respectively, with a total concentration of 0.05 M. The single-crystals were then vacuum dehydration at 623 K and 1×10-4 Pa for 2 days. Their single-crystal structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Pm3-m, at 100(1) K, and were then refined to the final error indices of R1/wR2=0.047/0.146, 0.048/0.142, 0.036/0.128, and 0.040/0.156 for crystals 1, 2, 3, and 4, respectively. In crystals 1 and 2, the 6 Sr2+ ions are found at three different crystallographic sites. In crystal 3, 1 Sr2+ and 10 Na+ ions are found in large cavity and sodalite unit. In crystal 4, only 12 Na+ ions occupy three equipoints. The degree of Sr2+ ion-exchange decreased sharply from 100 to 16.7 to 0% as the initial Na+ concentration increase and the Sr2+ concentration decrease. In addition, the unit cell constant of the zeolite framework decreased with this lower level of Sr2+ exchange.

이온교환 용액내 Na+ 이온의 몰농도 증가에 따른 zeolite A의 Sr2+ 이온교환 특성을 연구하기 위하여, Sr2+ 및 Na+ 이온으로 교환된 4개의 zeolite A 단결정을 혼합 이온교환 용액을 이용하여 회분법으로 준비하였다. 이들 이온교환용액의 전체 몰농도는 0.05 M이며, Sr(NO3)2:NaNO3 몰비는 각각 1:1(crystal 1), 1:100(crystal 2), 1:250(crystal 3), and 1:500(crystal 4) 이다. 이들 단결정은 623 K와 1×10-4 Pa의 진공하에서 2 일간 탈수 시켰다. 이들의 구조는 단결정 싱크로트론 X-선 회절법으로 입방공간군 Pm3-m을 사용하여 해석하였으며 crystals 1, 2, 3 및 4의 최종 오차 인자를 각각 0.047/0.146, 0.048/0.142, 0.036/0.128, and 0.040/0.156로 정밀화하였다. Crystal 1과 2에서는 6개의 Sr2+ 이온이 결정학적으로 서로 다른 3개의 위치에서 발견되었다. Crystal 3에서는 1개의 Sr2+ 이온과 10개의 Na+ 이온이 large cavity와 sodalite 내부에서 발견 되었다. Crystal 4 에서는 단지 12개의 Na+ 이온만이 3개의 서로 다른 결정학적 자리에 점유하고 있었다. Sr2+ 이온의 이온교환율은 초기 Na+ 이온의 농도가 증가하고 Sr2+ 이온의 농도가 감소함에 따라 100에서 16.7 및 0%로 급격하게 감소 하였다. 또한, Sr2+ 이온 교환률이 감소 함에 따라 제올라이트 골격의 단위 격자 상수 값이 갑소 하였다.

Keywords

Acknowledgement

본 연구는 2020년도 중소벤처기업부의 기술개발사업 지원에 의한 연구임(과제번호. S2907885).

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