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Table 1 Summary of experimental results of previous studies of Fe(II) reacted with Mn-oxides

From: Fe(II) reduction of pyrolusite (β-MnO2) and secondary mineral evolution

Mn-oxide substrate Fe-oxide formed Conditions Notes References
Birnessite [δ-MnO2] FeOOH pH 3–6 Fe(III) stays in solution for pH < 4 and XRD inconclusive [18]
Birnessite [δ-MnO2] Lepidocrocite and trace goethite pH 4–6 Higher pH produces more goethite, noncrystalline Fe-oxide [32]
Hexagonal birnessite Lepidocrocite and goethite pH 4–7 Less goethite under anoxic conditions compared to oxic [48]
Cryptomelane [KMn8O16] Akaganeite-FeOOH pH 3–6 [20]
Hausmannite [Mn3O4] Magnetite Fe3O4 pH 3–6 [20]
MnO2 Fe(OH)3 [15]
MnO2 Fe(OH)3; 6-line ferrihydrite Column pH 2.5–6 Natural Mn-oxide coated sand [19]
Pyrolusite [β-MnO2] Fe-oxyhydroxide, lepidocrocite pH 3–6 [20]
Pyrolusite coated silica sand 2-line ferrihydrite and jacobsite (MnFe2O4) pH 3 Fe(III) precipitates inhibit reductive dissolution of pyrolusite by Fe(II) [16]
Pyrolusite coated quartz Schwertmannite or sulfate-substituted ferrihydrite pH 3 [17]
Poorly crystalline MnO2 (similar to birnessite) and freshwater sediment Amorphic Fe(III) oxide pH 7 [49]
Vernadite [δ-MnO2] Fe2O3 pH 7.4 Fe phase proposed in equation but not characterized [50]