Korean Journal of Mineralogy and Petrology (광물과 암석)

The Petrological Society of Korea & The Mineralogical Society of Korea (한국암석학회 & 한국광물학회)
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Comparative Crystal Chemistry of Exchanged by Cs-, Cd-, Pb-, and Sr-synthetic Mordenite Using High Resolution X-ray Powder Diffraction

고분해능 X-선 분말 회절을 이용한 Cs-, Cd-, Pb-, Sr-으로 치환된 합성 모데나이트의 격자상수 비교 연구

  • Lee, Soojin (Department of Geological Sciences, Pusan National University) ;
  • Lee, Hyunseung (Department of Geological Sciences, Pusan National University) ;
  • Seoung, Donghoon (Department of Earth and Environmental Sciences, Chonnam National University) ;
  • Kim, Pyosang (Department of Earth and Environmental Sciences, Chonnam National University) ;
  • Kim, Hyeonsu (Department of Earth and Environmental Sciences, Chonnam National University) ;
  • Lee, Yongmoon (Department of Geological Sciences, Pusan National University)
  • 이수진 (부산대학교 지질환경과학과) ;
  • 이현승 (부산대학교 지질환경과학과) ;
  • 성동훈 (전남대학교 지구환경과학부) ;
  • 김표상 (전남대학교 지구환경과학부) ;
  • 김현수 (전남대학교 지구환경과학부) ;
  • 이용문 (부산대학교 지질환경과학과)
  • Received : 2022.07.06
  • Accepted : 2022.07.27
  • Published : 2022.09.30
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Abstract

This study aimed to fundamentally understand changes of cell parameters of cation-exchanged mordenites using high resolution X-ray powder diffraction for studies that immobilization of various heavy metal cation using synthesis mordenite (Na6.6Al6.6Si41.4O96·20.4H2O, Na-MOR). As a results of measurement by Thermogravimetric analysis (TGA), it was confirmed that 19.4, 20.4 water molecules per unit cell were present in monovalent-cation substituted MOR (Cs-MOR, Na-MOR), and 21, 23.1, 23.2 water molecules per unit cell were present in divalent-cation substituted MOR (Pb-MOR, Sr-MOR, Cd-MOR). The space group of all the samples were identified as Cmcm belonging to the orthorhombic crystal system. Compared to Na-MOR, starting material, relative peak intensity of (110) and (200) is significantly changed after cation substitution whereas peak position is almost similar. Also, (220) peak that was not found in Na-MOR was clearly observed in Pb-, Cd- and Sr-exchanged MOR. Thus, it was estimated that changes of atomic distribution usually occurred on ab-plane while changes of cell parameters were little. Detailed changes in the cell parameters of cation-exchanged mordenites were derived from whole profile fitting method using the GSAS suite program. Changes in the axial lengths and unit cell volume of cation substitution showed different relationship depending on ionic radius and charge number. In case of monovalent-cation substituted MOR, the length of a-axis increases whereas the length of b- and c-axis decrease by absorbed cation radius. In the case of divalent-cation exchanged MOR, the length of a-axis usually decreases while the length of b- and c-axis increases by cation radius. It was confirmed that unit cell volume of monovalent and divalent cation substituted MORs had an independent tendency by cation radius.

본 연구는 합성 모데나이트(Na6.6Al6.6Si41.4O96·20.4H2O, Na-MOR)를 이용한 다양한 중금속의 포획 연구를 하기 위한 기초 단계로, 고분해능 X-선 분말 회절을 이용하여 치환체의 격자상수 및 부피 변화를 이해하기 위한 목적으로 실험을 진행하였다. 열중량 분석법(Thermogravimetric analysis, TGA)으로 측정한 결과, 1가 양이온 치환체(Cs-MOR, Na-MOR)는 단위포 당 19.4, 20.4개의 물분자가 존재하였으며, 2가 양이온 치환체(Pb-MOR, Sr-MOR, Cd-MOR)는 단위포 당 21, 23.1, 23.2개가 존재하는 것을 확인하였다. 측정한 모든 물질은 사방정계에 속하는 Cmcm의 공간군을 가지는 것으로 확인할 수 있었다. 치환 전 물질인 Na-MOR과 비교했을 때, 치환체의 (110)면과 (200)면의 회절강도가 명확하게 변화하였으나, 전체적인 피크의 위치는 거의 유사하게 나타나는 것을 확인할 수 있었다. 또한 Na-MOR에서는 확인이 되지 않았던 (220)면의 피크가 Pb-, Cd-, Sr-MOR에서 뚜렷하게 관찰되었다. 이를 통해서 양이온 치환에 따른 원자들의 분포 변화가 주로 ab-평면상에서 나타나지만, 격자상수의 변화는 미세할 것으로 짐작할 수 있었다. Whole profile fitting 방법을 사용하여 치환된 모데나이트의 미세한 격자상수의 변화를 관찰하였다. 치환체의 격자상수 및 격자부피의 변화는 치환된 양이온의 반경 및 전하수에 따라 서로 다른 경향성을 보였다. 1가 양이온의 경우, 이온반경이 증가할수록 a-축의 길이는 증가하지만, 반면에 b- 및 c-축의 길이는 감소하였다. 2가 양이온의 경우, 이온반경이 증가할수록 대체적으로 a-축의 길이가 감소하고, b- 및 c-축의 길이는 증가하였다. 격자부피는 1가 또는 2가 양이온 치환체들이 각각 독립된 경향성을 가지며, 이온반경에 따라 증가하는 것을 확인할 수 있었다.

Keywords

Acknowledgement

본 연구는 부산대학교 기본연구지원사업(2년)에 의하여 연구되었다.

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