Characterizing the reactivity of metallic iron in Fe0/EDTA/H2O systems with column experiments

Characterizing the intrinsic reactivity of iron materials for environmental remediation has received relative little interest. Available results are mostly based on the removal extent of selected contaminants in batch systems. Under static conditions however, contaminant removal depends on the properties of the oxide-film. The present study was performed to investigate the chemical reactivity of nine Fe0 materials under conditions that minimize the formation of an oxide-film on the metal surface. Ethylenediaminetetraacetate (EDTA) was used to sustain Fe0 dissolution during column testing for 2 months. The results confirm Fe0 dissolution rate in 2 mM EDTA as a good tool for comparative reactivity characterization. Moreover, long-term column studies with 2 mM EDTA enable: (i) the evidence of increased powdered Fe0 reactivity relative to granular materials and (ii) a clear differentiation among granular materials which exhibited very closed extents of iron dissolution under static conditions. Future works comparing Fe0 intrinsic reactivity should ideally characterize material behaviour in an oxide-free system and compare the results to those obtained under relevant experimental conditions.