Precipitation of ALn(CO{sub 3}){sub 2},xH{sub 2}O and Dy{sub 2}(CO{sub 3}){sub 3},xH{sub 2}O compounds from aqueous solutions for A{sup +}=Li{sup +},Na{sup +},K{sup +},Cs{sup +},NH{sub 4}{sup +} and Ln{sup 3+}=La{sup 3+},Nd{sup 3+},Eu{sup 3+},Dy{sup 3+}

Journal Article · Mon Sep 15 00:00:00 EDT 2008 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2008.04.030· OSTI ID:21128424

Philippini, Violaine ^[1]; Vercouter, Thomas ^[1]; Chausse, Annie ^[2]; Vitorge, Pierre ^[1]

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1. CEA Saclay DEN/DPC/SECR Laboratoire de Speciation des Radionucleides et des Molecules, 91191 Gif-sur-Yvette (France)
2. Laboratoire Analyse et Modelisation pour la Biologie et l'Environnement UMR 8587, Universite d'Evry Val d'Essonne-CNRS, Boulevard F. Mitterrand, 91025 Evry cedex (France)

Double carbonates of lanthanide (Ln) and alkaline or ammonium (A) ions, noted ALn(CO{sub 3}){sub 2},xH{sub 2}O, were precipitated from concentrated A{sub 2}CO{sub 3} aqueous solutions at room temperature and atmospheric pressure. Twelve hydrated compounds out of the twenty targeted ones have been obtained: Li(NdorEu)(CO{sub 3}){sub 2}, NaLa(CO{sub 3}){sub 2}, KNd(CO{sub 3}){sub 2},xH{sub 2}O, Cs(LaorNd)(CO{sub 3}){sub 2}, NH{sub 4}(Nd,EuorDy)(CO{sub 3}){sub 2}, Dy{sub 2}(CO{sub 3}){sub 3} from concentrated A{sub 2}CO{sub 3} solutions and Na(Nd,EuorDy)(CO{sub 3}){sub 2} from concentrated AHCO{sub 3} solutions. Although the trivalent lanthanide ions are often considered as analogs in solution, differences in their precipitation behaviour was observed, which is believed to have a kinetic origin in relation to the small differences in their ionic radii. The solid compounds were characterised by elemental analyses, thermogravimetry (TG), X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS). The powder diffraction patterns of nine solids were fitted using the tetragonal P4/mmmLaue class: LiNd(CO{sub 3}){sub 2},xH{sub 2}O: a=(12.16{+-}0.02)A, c=(9.21{+-}0.02)A, LiEu(CO{sub 3}){sub 2},3H{sub 2}O: a=(12.201{+-}0.007)A, c=(9.23{+-}0.01)A, KNd(CO{sub 3}){sub 2},xH{sub 2}O: a=(13.28{+-}0.04)A, c=(10.00{+-}0.04)A, CsLa(CO{sub 3}){sub 2},xH{sub 2}O: a=(10.82{+-}0.02)A, c=(8.18{+-}0.02)A, CsNd(CO{sub 3}){sub 2},xH{sub 2}O: a=(10.81{+-}0.07)A, c=(8.16{+-}0.07)A for NaLn(CO{sub 3}){sub 2},xH{sub 2}O: a=(11.10+1.75r{sub Ln{sup 3}{sup +}})A and c=(8.60+1.13r{sub Ln{sup 3+}})A, where r{sub Ln{sup 3+}} is the ionic radius of Ln{sup 3+} for a coordination number of 8 (r{sub La{sup 3+}}=1.16A, r{sub Nd{sup 3+}}=1.12A, r{sub Eu{sup 3+}}=1.07A and r{sub Dy{sup 3+}}=1.03A). It is proposed that all the NaLn(CO{sub 3}){sub 2},xH{sub 2}O compounds are of very similar structure, as evidenced by their XRD patterns and by the linear variations of the lattice parameters with r{sub Ln{sup 3+}}. The small differences in the lattice parameters can induce large modification of the precipitation pathways. Conversely, structural changes were evidenced within the A{sup +} series for ANd(CO{sub 3}){sub 2},xH{sub 2}O. Dy{sub 2}(CO{sub 3}){sub 3},xH{sub 2}O was also obtained as a by-product. Its lattice parameters are in good agreement with Eu{sub 2}(CO{sub 3}){sub 3},3H{sub 2}O ones. - Linear relationships between the ionic radii of the lanthanides and the unit cell parameters of the corresponding NaLn(CO{sub 3}){sub 2},xH{sub 2}O compounds, extracted from three different studies (our experimental data (black) are compared with those of Mochizuki et al. (red) and Runde et al. (blue))

• OSTI ID: 21128424
• Journal Information: Journal of Solid State Chemistry, Vol. 181, Issue 9; Other Information: DOI: 10.1016/j.jssc.2008.04.030; PII: S0022-4596(08)00218-1; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ALKALI METAL COMPOUNDS
AQUEOUS SOLUTIONS
ATMOSPHERIC PRESSURE
CARBONATES
CESIUM IONS
COORDINATION NUMBER
DYSPROSIUM IONS
EUROPIUM IONS
LANTHANUM IONS
LATTICE PARAMETERS
LITHIUM IONS
NEODYMIUM IONS
POTASSIUM IONS
PRECIPITATION
RARE EARTH COMPOUNDS
SCANNING ELECTRON MICROSCOPY
SODIUM IONS
TEMPERATURE RANGE 0273-0400 K
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION