Interaction of Eu(III) ion and non-porous silica: Irreversible sorption of Eu(III) on silica and hydrolysis of silica promoted by Eu(III)

The interaction of Eu(III) with non-porous silica was studied using sorption-desorption experiments and Eu(III) was characterized by laser-induced fluorescence spectroscopy. The independence of Eu(III) sorption on ionic strength, the increased affinity of silica for heavier rare earth ions, and the removal of water in the inner-sphere of Eu(III) due to sorption demonstrate that the formation of an inner-sphere complex of Eu(III) with silanol groups at the silica surface is an important process in the initial reaction. A further decrease in the number of hydrated water molecules with time and the irreversibility of the Eu(III) sorption suggest that a new phase incorporating Eu(Ill) and Si(IV) forms at the silica surface. The presence of Eu(III) greatly promoted the dissolution of silica, which indicated that Eu(III) was effectively hydrolyzing the Si-O-Si bonds. The formation process of the Eu(Ill)-silicate phase is discussed. (c) 2005 Elsevier B.V. All rights reserved.