The idea that manganese oxide (MnO2) sustains the reactivity of metallic iron (Fe-0) is investigated in this study. A multi-elemental aqueous system containing Cr-VI, Cu-II, Mo-VI, Sb-V, U-VI and Zn-II (each about 100 mu M) was used as model solution. Non-disturbed batch experiments were performed at initial pH values 4.0 and 6.0 for one month. Three different systems were investigated: (i) "MnO2 alone", (ii) "Fe-0 + sand", and (iii) "Fe-0 + MnO2". The experimental vessels contained either: (i) no material (blank), (ii) up to 9.0 g L-1 of MnO2, or (iii) 5 g L-1 Fe-0 and 0-9.0 g L-1 MnO2 or sand. Results clearly revealed quantitative contaminant removal (>70%) confirming the suitability of Fe-0 as a highly efficient reactive material for the removal of the 6 tested metallic ions over a pH range applicable to environmental waters. Results also corroborated the suitability of MnO2 to sustain the long-term Fe-0 reactivity. Further studies in dynamic systems (column studies) are necessary to fine-tune the use of MnO2 in Fe-0 filtration systems. (C) 2011 Elsevier B.V. All rights reserved.