Retention of tripositive lanthanides (Gd, Ho, Yb, Lu) by montmorillonite

Abstract

A Trancos montmorillonite from Gador (Spain), with a calculated charge deficit per unit cell of 0.87 units, has been saturated with Gd (III), Ho (III), Yb (III) and Lu (III). FT-IR spectra and b-dimension measurements show no migration of the 4f ions from their interlamellar sites to octahedral ones with air-heating treatments at 300°C. The fixation of the lanthanide ions by the montmorillonite with heating should be ascribed exclusively to the hydrolysis of the hydrated ions. The FT-IR spectroscopy results show a large decrease in the extension of the lanthanide montmorillonite hydration, which has been ascribed to a decrease of the more firmly held water, direct coordinated to the cations in a first sphere. The heated lanthanide montmorillonites are capable of swelling, the ones with the heavier 4f ions showing some inertia to it.