Effects of Temperature on the Sorption of Lanthanides by Montmorillonite

Abstract

Abstract--The diffusion of exchanged Yb, Ho, and Eu from interlayer positions in montmorillonite was studied using infrared spectroscopy (IR), X-ray powder diffraction, and cation-exchange measurements. Dehydration of exchanged montmorillonite between 100 ~ and 280~ caused the ions to diffuse into the hexagonal rings of surface oxygens. Subsequent migration into vacant octahedral sites was small regardless of the radius of the cation. Considerable ion fixation in excess of the cation-exchange capacity of the clay was observed at 20~ in both water and a I: 1 water:95% ethanol mixture. Evidence for hydrolysis as a possible mechanism for cation fixation was obtained by observing frequency shifts for deuterated hydroxyl groups using IR spectroscopy. A major IR band centered at 2680 cm -1 was observed for all three lanthanideexchanged montmorillonites studied and assigned to the OH-stretching frequency of a lanthanide hydroxide. This band intensified on heating at 300~ for 1 hr. An IR band between 690 and 710 cm -1 also was observed for all three lanthanide-exchanged montmorillonites and was assigned to a lanthanide-hydroxyl deformation mode. No hydrolysis was observed for Na-montmorillonite, as expected from the very low hydration energy of Na +.

Effect of Pressure on the Sorption of Yb by Montmorillonite

“…The swelling behavior and sorbed ion content of the samples treated at 110 atm and 20~ are nearly identical with the samples examined at 1 atm by Miller et al (1982), For 100 ~ and 160~ less irreversible Yb-sorption took place at 110 atm than at 1 atm, and more 10.0-A interlayers persisted. Such persistent 10.0-A interlayers were observed for aqueous resuspensions of samples treated at 1 atm only after extensive dehydration due to heating.…”

“…Samples heat treated at 100 ~ and 160~ show, in addition, a weak 10-A reflection. The polarographic data (Table 1) indicate that at 110 atm the amount of Yb z+ sorbed by the clay phase decreased as the temperature increased in marked contrast to the 1-atm experiments of Miller et al (1982).…”

“…The Irtran disk was then placed in a stainless steel sample holder of an infrared vacuum cell which was positioned in the infrared beam. The specifics regarding the design of the infrared cell are described in detail by Miller et al (1982).…”

“…This study considers the effects of both temperature and pressure on the irreversible fixation of lanthanide ions on the same Upton, Wyoming, montmorillonite studied by Miller et al (1982). The Yb-exchanged montmorillonite is representative of the lanthanide-exchanged clays considered previously because: (1) octahedral migration, although small, is greater for Yb than for Ho and Eu; and (2) Yb-exchanged montmorillonites hydrolyze more extensively at a given temperature than their Eu or Ho counterparts.…”

The adsorption of quadrivalent cerium by kaolinite

“…Recently, the adsorption of a few lanthanides by montmorillonite was investigated by Bruque et al (1980( ) and Miller et al (1982( , 1983. The present communication deals with the mechanism of adsorption of cerium by kaolinite.…”