Characterizing the reactivity of metallic iron in Fe-0/U-VI/H2O systems by long-term column experiments

Aqueous iron corrosion has been identified as a powerful process for environmental remediation and safe drinking water provision. The intrinsic reactivity of conventional micro-scale metallic iron (Fe-0) has been mostly enhanced by the association of other metals (e.g. Cu, Ni and Pd) or by using nano-scale Fe-0. However, the mechanisms responsible for increased reactivity are yet to be univocally elucidated. Therefore, it appears that basic knowledge on Fe-0 intrinsic reactivity decreases as Fe-0 technology advances. This work was performed to address the intrinsic reactivity of four selected conventional Fe-0 materials in long-term column studies. Five systems were investigated. Each system was made up of two columns in series. The first column contains 5.0 g of a U-bearing rock mixed with sand. The second sand column contained 0.0 or 4.0 g of each Fe-0. The extent of U fixation in the systems was used to characterize the reactivity of the Fe-0 materials. Results showed a clearer differentiation among the three Fe-0 materials which exhibited very closed extents of iron dissolution in 2 mM EDTA under dynamic conditions. The crucial importance of long-term column experiments to test the suitability of Fe-0 for field applications is delineated. A new research trend is presented. (C) 2011 Elsevier B.V. All rights reserved.