Sorption of Eu(III) on a Natural Hematite: Application of a Surface Complexation Model.
The solid/water interface reaction is investigated for the sorption of the Eu3+ ion onto a well-characterized natural hematite at pH </=6 in 0.1 mol/L NaClO4. Sorption isotherms are determined at different pH. The sorption of Eu3+ onto hematite at coverages <1% of the surface hydroxyl groups follows the ideal Nernst behavior and can be interpreted in terms of the surface complexation by the following equilibrium reaction: &tbond;XOH + Eu3+ if &tbond;XOEu2+ + H+ (log Kintx = 2.50 +/- 0.19). Complexation constants are calculated by either graphically interpretating the sorption isotherms or fitting the data using the code FITEQL. At higher surface coverages a deviation from the Nernst behavior is observed which can be described satisfactorily by a two-site surface complexation model, taking into account the lateral electrostatic interaction of surface-bound Eu(III): &tbond;YOH + Eu3+ if &tbond;YOEu2+ + H+ (log Kinty = -0.82 +/- 0.11). The experimental results are compared with data published in the literature, and the interpretation of sorption isotherms with regard to the sorption mechanisms is critically discussed. Copyright 1998 Academic Press.
Rabung
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Anorganische und Analytische Chemie und Radiochemie, Universität des Saarlandes, Saarbrücken, D-66041, Germany
Geckeis
H
Kim
JI
Beck
HP