The adsorption of quadrivalent cerium by kaolinite.

The adsorption of cerium(IV) by both natural and Na-exchanged kaolinite from aqueous solutions of ceric ammonium nitrate was studied in equilibrium systems. Ce may be adsorbed either as a monomeric species or as a polymeric hydroxy cation. The species adsorbed depends on the concentration of Ce 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 H₂SO₄ - and may be considered fixed. Adsorption of Ce reaches a maximum in solutions containing 0.15 M H₂SO₄. (Authors' abstract)-D.J.M.Dept. of Inorganic & Analytical Chemistry, Hebrew Univ., Jerusalem 91904, Israel.