Uptake of Lanthanides by Vermiculite

Pascual Olivera Pastor, Enrique Rodríguez-Castellón and Aurora Rodríguez García
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Facultad de Ciencias Universidad de Málaga, 29071 Málaga, Spain

Abstract: The uptake of Ce3+, Nd3+, Gd3+, Er3+, and Lu3+ on vermiculite was studied using cation-exchange measurements, infrared spectroscopy (IR), and X-ray powder diffraction (XRD). The reaction was followed by measuring the amount of lanthanide ions (Ln3+) taken up by n-butylammonium-exchanged vermiculite in relation to amount of Ln3+ salt added and the pH of the equilibrium solution. The amount of Ln3+ taken up in excess of the CEC value increased with the hydration energy of the lanthanide ion and with the pH of the n-butylammonium-exchanged vermiculite suspension. At equilibrium solution pHs of 3–4.5, the uptake of Ln3+ ions was only slightly greater than the CEC, whereas at pHs >4.5 the amount taken up by the vermiculite increased sharply. The uptake of Ln3+ ions beyond the CEC of the vermiculite is probably related to the hydrolysis of Ln3+ ions on the vermiculite interlayer surface. The appearance of a band at 1715–1720 cm−1 in the IR spectra of the Ln3+-exchanged vermiculite suggests a strongly acidic medium in the interlayer space. The Ln3+-exchanged vermiculites gave XRD patterns having 002/001 intensity ratios greater than that of Mg-exchanged vermiculite.

Key Words: Hydration energy • Hydrolysis • Infrared spectroscopy • Ion exchange • Lanthanide ions • Vermiculite • X-ray powder diffraction

Clays and Clay Minerals; February 1988 v. 36; no. 1; p. 68-72; DOI: 10.1346/CCMN.1988.0360109
© 1988, The Clay Minerals Society
Clay Minerals Society (www.clays.org)