Exchange Selectivity of Lanthanide Ions in Montmorillonite

J. Maza-Rodriguez, P. Olivera-Pastor, S. Bruque and A. Jimenez-Lopez
Departamento de Química Inorgánica, Cristalografia y Mineralogia, Universidad de Málaga, Apdo. 59, 29071 Málaga, Spain

Abstract: The exchange of Ca2+ and Na+ by tanthanide ions (Ln3+ = Pr3+, Gd3+, Er3+) in montmorillonite was investigated at two different ionic strengths (0·01 and 0·1 mol/kg). Preferential sorption of Ln3+ was observed and variable selectivity coefficients were found depending upon the lanthanide concentration in the solid, and ionic strength. The highest exchange extent of Ln3+ always occurred for the system Na+/Ln3+, but the exchange selectivities of Ln3+ were generally higher in the exchange system Ca2+/Ln3+. Although the relative affinity of montmorillonite for the three lanthanide ions was similar, distinctive behaviour between Pr3+ and the heavier lanthanides, Gd3+ and Er3+, was noted. The study of Ln3+ adsorption in trace amounts showed specific adsorption of lanthanides at high concentrations of Na+ in the external solution and that the exchange stoichiometries in the interlayer regions were 3 : 1 at equilibrium pH = 4.

Clay Minerals; March 1992 v. 27; no. 1; p. 81-89; DOI: 10.1180/claymin.1992.027.1.08
© 1992, The Mineralogical Society
Mineralogical Society (www.minersoc.org)