Exploring the influence of operational parameters on the reactivity of elemental iron materials

In an attempt to characterize material intrinsic reactivity, iron dissolution from elemental iron materials (Fe0) was investigated under various experimental conditions in batch tests. Dissolution experiments were performed in a dilute solution of ethylenediaminetetraacetate (Na2-EDTA - 2 mM). The dissolution kinetics of 18 Fe0 materials were investigated. The effects of individual operational parameters were assessed using selected materials. The effects of available reactive sites [Fe0 particle size (≤2.0 mm) and metal loading (2-64 g L−1)], mixing type (air bubbling, shaking), shaking intensity (0-250 min−1), and Fe0 pre-treatment (ascorbate, HCl and EDTA washing) were investigated. The data were analysed using the initial dissolution rate (kEDTA). The results show increased iron dissolution with increasing reactive sites (decreasing particle size or increasing metal loading), and increasing mixing speed. Air bubbling and material pre-treatment also lead to increased iron dissolution. The main output of this work is that available results are hardly comparable as they were achieved under very different experimental conditions. A unified experimental procedure for the investigation of processes in Fe0/H2O systems is suitable. Alternatively, a parameter (τEDTA) is introduced which could routinely used to characterize Fe0 reactivity under given experimental conditions.