A B S T R A C T:The adsorption of cerium(IV) by both natural and Na-exchanged kaolinite from aqueous solutions of ceric ammonium nitrate was studied in equilibrium systems. Cerium may be adsorbed either as a monomeric species or as a polymeric hydroxy cation. The species adsorbed depends on the concentration of cerium in the stock solution, the age of this solution prior to the preparation of the equilibrium system and on the equilibration period. Adsorbed cations undergo polymerization on the surface of the kaolinite; the resulting polymeric species forms strong bonds with the clay surface--it is not desorbed by sulphuric acid--and may be considered fixed. Adsorption of cerium reaches a maximum in solutions containing 0.15 M sulphuric acid.Very little is known about the adsorption of lanthanides by clay minerals, although this process seems to be important in the geochemical cycle of these elements. 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. EXPERIMENTAL MaterialsNatural kaolinite from Maktesh-Ramon, Israel, was manually ground using an agate pestle and mortar and the fraction passing an 80-mesh (0.177 mm) sieve was used. Na-kaolinite was prepared by dispersing 1 g of natural kaolinite:in 25 ml M NaC1 and, after a 24-h equilibration period, the excess NaCI was removed by repeated washing with distilled water, followed by centrifugation, until no chloride was detected. The exchangeable sodium content of the Na-kaolinite was 0.03 mEq Na/g clay. Equilibrium systemsThree stock solutions containing 0.1, 0.01 and 0.001 M ceric ammonium nitrate were used for the preparation of equilibrium systems. The cerium salt was dissolved either in distilled water or in aqueous solutions of sulphuric acid. Adsorption was carried out in equilibrium systems containing 1 g clay. Various amounts between 0.5 and 10.0 ml of each of the stock solutions of cerium(IV) were added. The suspension was diluted to 12.0 ml by adding distilled water. Some of the series of equilibrium systems were prepared from fresh and others from aged stock solutions. Equilibration periods ranged from 30 min to 1984 The Mineralogical Society
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.