Characterizing the reactivity of metallic iron in Fe0/UVI/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 (Fe0) has been mostly enhanced by the association of other metals (e.g. Cu, Ni and Pd) or by using nano-scale Fe0. However, the mechanisms responsible for increased reactivity are yet to be univocally elucidated. Therefore, it appears that basic knowledge on Fe0 intrinsic reactivity decreases as Fe0 technology advances. This work was performed to address the intrinsic reactivity of four selected conventional Fe0 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 Fe0. The extent of U fixation in the systems was used to characterize the reactivity of the Fe0 materials. Results showed a clearer differentiation among the three Fe0 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 Fe0 for field applications is delineated. A new research trend is presented.