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/H2O systems) is characterized by the large diversity of removing agents. This paper analyses the synergistic effect of adsorption, coprecipitation and reduction on the process contaminant removal in Fe-0/H2O systems oil 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/H2O 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. (C) 2009 Elsevier B.V. All rights reserved.