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Front. Chem. | doi: 10.3389/fchem.2018.00558

Rietveld structure refinement of Cu-trien exchanged nontronites

  • 1Freiberg University of Mining and Technology, Germany
  • 2China University of Geosciences, China

The Rietveld analysis of X-ray powder diffraction patterns is widely used for obtaining the structural information of clay minerals. However, the complex hydration behavior and the variability of interlayer contents are commonly considered difficult to be described correctly by a simple structure model. In the present work, the use of Cu-triethylenetetramine (Cu-trien) exchanged nontronites has been proposed to simplify the interlayer structure. This method provides a potential to obtain the structural information of nontronites, e.g. the layer charge density, occupancies of cis-octahedral sites and iron content by the Rietveld analysis from the X-ray powder diffraction patterns.

The approach was demonstrated on three Cu-trien exchanged nontronite samples. The Rietveld refinements were firstly carried out on the purified samples and the results showed a good peak fitting between measured and calculated patterns. The refined iron content and the occupancies of cis-octahedral sites are in general agreement with the reference data which obtained from chemical and thermal analysis. The refinement of layer charge density showed lower values compared to the reference. It may due to the assumption of temperature factor of Cu-trien in the interlayer. A raw sample with natural impurities was chosen to test the applicability of this method. The refinement pattern of the raw sample led to good agreement with the observed data. The results of the iron content and the occupancies of cis-octahedral sites showed same tendency as purified sample. This study was shown that this approach allows for obtaining some structural details of nontronites directly from X-ray powder diffraction patterns of Cu-trien exchanged samples.

Keywords: Nontronites, Rietveld refinement, CU-TRIETHYLENETETRAMINE, crystal structure, X-ray powder diffraction

Received: 27 Jul 2018; Accepted: 29 Oct 2018.

Edited by:

Wenbo Wang, Lanzhou Institute of Chemical Physics (CAS), China

Reviewed by:

Luyi Sun, University of Connecticut, United States
JIANXI ZHU, Guangzhou Institute of Geochemistry (CAS), China
Yunfei Xi, Queensland University of Technology, Australia  

Copyright: © 2018 Wang and Liao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Libing Liao, China University of Geosciences, Beijing, 100083, Beijing Municipality, China,