Preparation and structure's analyses of lanthanide (Ln) -exchanged bentonites

Eszter Mária Kovács, Eszter Erdélyiné Baradács, Péter Kónya, Péter Kovács-Pálffy, Sándor Harangi, E. Kuzmann, József Kónya, N. Nagy

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7 Citations (Scopus)

Abstract

The interaction between Lanthanides (Ln)- ions and Ca-bentonite and the structural changes accompanying were studied. Ln-exchanged bentonites were prepared from Ca-bentonite (Istenmezeje, Hungary) by ion exchange in three consecutive washings with lanthanide solutions. Scanning Eletronmicroscopy Energy Dispersive X-ray spectroscopy (SEM-EDX) studies showed even distribution of Lns and other components of bentonite. The natural bentonite and the lanthnide exchanged bentonites were characterized by X-ray diffraction (XRD), which revealed the same mineral composition, and the increase of the basal spacing of montmorillonite from 1.465 (Ca2+) to 1.577 nm (REE3+). The d001 basal spacing of lanthanide montmorillonite increases as the ion radius of the lanthanide cation increases. The Fe3+, and Lns3+ amount on the bentonite were determined by X-ray-fluorescence spectrometry (XRF) elemental analysis. The amount of exchanged Lns were determined by washing the Ln-bentonite with 1 M ammonium-acetate, and measuring the amount of Ln released, using inductively coupled plasma optical emission spectrometry (ICP-OES). In most Ln-bentonites, the quantity of the exchanged Ln ions was about 80–90% of the cation exchange capacity (CEC) of the bentonite. In case of some lanthanides bentonite (La3+, Ce3+, and Gd3+), however, the sorbed quantity of lanthanum ions was higher than the cation exchange capacity. In case of lanthanum-bentonite, the lanthanide quantity is as high as 136% of CEC. Moreover, the iron(III) content of lanthanum bentonite is less than that of the original Ca-bentonite. Mössbauer spectra of the La-, Ce-, and Gd-exchanged samples at 78 K revealed an unexpected magnetically split component that was absent from the Ca-bentonite. This component may belong to interlayer Fe. This iron can be released from the octahedral positions crystal lattice.

Original languageEnglish
Pages (from-to)287-294
Number of pages8
JournalColloids and Surfaces A: Physicochemical and Engineering Aspects
Volume522
DOIs
Publication statusPublished - Jun 5 2017

Keywords

  • Complexometric titration
  • Inductively coupled plasma optical emission spectrometry
  • Ln-bentonites
  • Scanning electron microscopy
  • X-ray diffraction
  • X-ray-fluorescence spectrometry

ASJC Scopus subject areas

  • Colloid and Surface Chemistry

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