Impact of MnO2 on the efficiency of metallic iron for the removal of dissolved CrVI, CuII, MoVI, SbV, UVI and ZnII

The idea that manganese oxide (MnO2) sustains the reactivity of metallic iron (Fe0) is investigated in this study. A multi-elemental aqueous system containing CrVI, CuII, MoVI, SbV, UVI, and ZnII (each about 100 μM) 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) “Fe0 + sand”, and (iii) “Fe0 + 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 Fe0 and 0–9.0 g L−1 MnO2 or sand. Results clearly revealed quantitative contaminant removal (>70%) confirming the suitability of Fe0 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 Fe0 reactivity. Further studies in dynamic systems (column studies) are necessary to fine-tune the use of MnO2 in Fe0 filtration systems.

► Fe0/MnO2 systems have been reported to be long-term efficient for contaminant removal.
► The suitability of MnO2 to sustain the removal of dissolved CrVI, CuII, MoVI, SbV, UVI and ZnII by Fe0 is demonstrated.
► Metal ions are progressively sequestrated by in situ generated iron corrosion products at pH > 4.5.
► Results corroborated the view that contaminants are fundamentally adsorbed and co-precipitated in Fe0/H2O systems.