| Summary: | Studies were undertaken to characterize the intrinsic reactivity of Fe<sup>0</sup>-bearing steel wool (Fe<sup>0</sup> SW) materials using the ethylenediaminetetraacetate method (EDTA test). A 2 mM Na<sub>2</sub>-EDTA solution was used in batch and column leaching experiments. A total of 15 Fe<sup>0</sup> SW specimens and one granular iron (GI) were tested in batch experiments. Column experiments were performed with four Fe<sup>0</sup> SW of the same grade but from various suppliers and the GI. The conventional EDTA test (0.100 g Fe<sup>0</sup>, 50 mL EDTA, 96 h) protocol was modified in two manners: (i) Decreasing the experimental duration (down to 24 h) and (ii) decreasing the Fe<sup>0</sup> mass (down to 0.01 g). Column leaching studies involved glass columns filled to 1/4 with sand, on top of which 0.50 g of Fe<sup>0</sup> was placed. Columns were daily gravity fed with EDTA and effluent analyzed for Fe concentration. Selected reactive Fe<sup>0</sup> SW specimens were additionally investigated for discoloration efficiency of methylene blue (MB) in shaken batch experiments (75 rpm) for two and eight weeks. The last series of experiments tested six selected Fe<sup>0</sup> SW for water defluoridation in Fe<sup>0</sup>/sand columns. Results showed that (i) the modifications of the conventional EDTA test enabled a better characterization of Fe<sup>0</sup> SW; (ii) after 53 leaching events the Fe<sup>0</sup> SW showing the best k<sub>EDTA</sub> value released the lowest amount of iron; (iii) all Fe<sup>0</sup> specimens were efficient at discoloring cationic MB after eight weeks; (iv) limited water defluoridation by all six Fe<sup>0</sup> SW was documented. Fluoride removal in the column systems appears to be a viable tool to characterize the Fe<sup>0</sup> long-term corrosion kinetics. Further research should include correlation of the intrinsic reactivity of SW specimens with their efficiency at removing different contaminants in water.
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