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The high oxidation ability of manganese oxides or soils was used to study effects of pH and coatingon Cr(Ⅲ) oxidation. The results indicated that Cr(Ⅲ) oxidation peaked in pH 4.0-6.5. The amount andrate of Cr(Ⅲ) being oxidized by uncoated δ-MnO2 were larger than those by Fe oxide- or CaCO3-coatedone. Inorganic Cr(Ⅲ) was more easi1y oxidized by MnO2 than organic complex Cr(Ⅲ) due to differentsurface affinities. Precipitated Cr(Ⅲ) and adsorbed Cr(Ⅲ) might be transferred onto MnO2 surface andthen oxidized to Cr(VI).
The high oxidation ability of manganese oxides or soils was used to study effects of pH and coating on Cr (III) oxidation. The results indicated that Cr (III) oxidation peaked at pH 4.0-6.5. The amount and rate of Cr (III) being oxidized by uncoated δ-MnO2 were larger than those by Fe oxide- or CaCO3-coatedone. Inorganic Cr (Ⅲ) was more easi1y oxidized by MnO2 than organic complex Cr (Ⅲ) due to differentsurface affinities. III) might be transferred onto MnO2 surface and then oxidized to Cr (VI).