An analysis of the evolution of reactive species in Fe0/H2O systems.

Aqueous contaminant removal in the presence of metallic iron (e.g. in Fe(0)/H(2)O systems) is characterized by the large diversity of removing agents. This paper analyses the synergistic effect of adsorption, co-precipitation and reduction on the process contaminant removal in Fe(0)/H(2)O systems on the basis of simple theoretical calculations. The system evolution is characterized by the percent Fe(0) consumption. The results showed that contaminant reduction by Fe(0) is likely to significantly contribute to the removal process only in the earliest stage of Fe(0) immersion. With increasing reaction time, contaminant removal is a complex interplay of adsorption onto iron corrosion products, co-precipitation or sequestration in the matrix of iron corrosion products and reduction by Fe(0), Fe(II) or H(2)/H. The results also suggested that in real world Fe(0)/H(2)O systems, any inflowing contaminant can be regarded as foreign species in a domain of precipitating iron hydroxides. Therefore, current experimental protocols with high contaminant to Fe(0) ratios should be revisited. Possible optimising of experimental conditions is suggested.