Adsorption of Thorium(IV) on Chemically Modified Amazon Clays

Kaolinite and smectite clay samples from the Amazon region, Brazil, were modified with 2-mercaptobenzimidazole (MBI) using homogeneous and heterogeneous routes. The modified clay samples (K-HOM, S-HOM, K-HET and S-HET) were characterized by textural analysis, SEM and C-13 NMR spectroscopy. The chemically modified clay samples showed modifications of their physical-chemical properties including: specific area 48.0 (S) to 869.8 m(2) g(-1) (S-HET). The ability of these materials to remove thorium(IV) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature, and pH 2.0. The maximum number of moles adsorbed was determined to be 8.29, 8.86, 9.57 and 9.89 10(-1) mmol g(-1) for K-HOM,K- K-HET, S-HOM and S-HET, respectively. The energetic effects (Delta H-int, Delta(int)G and Delta S-int) caused by thorium(IV) cation adsorption were determined through calorimetry.