Please cite this article as: Eszter Mária Kovács, Eszter Erdélyiné Baradács, Péter Kónya, Péter Kovács-Pálffy, Sándor Harangi, József Kónya, Noémi M.Nagy, Preparation and structure's analyses of lanthanide (Ln) -exchanged bentonites, Colloids and Surfaces A: Physicochemical and Engineering Aspects http://dx.doi.org/10. 1016/j.colsurfa.2017.02.085 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
HIGHLIGHTS REE-exchanged bentonites were prepared from Ca-bentonite by ion exchange. The La 3+ -, Ce 3+ -, and Gd 3+ -bentonite, the sorbed ion amount was higher than the CEC. In case of lanthanum-bentonite, the rare earth quantity is as high as 136% of CEC. The iron(III) content of lanthanum bentonite is less than that of the original Cabentonite.
4Abstract The interaction between Lanthanides (Ln)-ions and Ca-bentonite and the structural changes accompanying were studied. Ln-exchanged bentonites were prepared from Cabentonite (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 (Ca 2+ ) to 1.577 nm (REE 3+ ). The d001 basal spacing of lanthanide montmorillonite increases as the ion radius of the lanthanide cation increases. The Fe 3+ , and Lns 3+ amount on the bentonite were determined by X-rayfluorescence spectrometry (XRF) elemental analysis. The amount of exchanged Lns were determined by washing the Ln-bentonite with 1M 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 (La 3+ , Ce 3+ , and Gd 3+ ), 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.5
