Oxidative removal of Mn(II) from solution catalysed by the γ-FeOOH (lepidocrocite) surface

The formation process of hydrous manganese oxide deposit can hardly be demonstrated in natural environments, namely, hot and cold springs and deep-sea hydrothermal vents. We discovered a unique phenomenum that hydrous manganese oxide is now actively depositing from the hot spring water at the Yuno-taki Falls, Hokkaido, Japan. The chemical and the biological factors that potentially control the actual manganese deposition in the natural environment were examined.Pure manganese oxide deposit (1.1 ton/year calculated as Mn02) is currently being formed from weakly acidic hot spring water by the mediation of microbial consortium consisting of manganese-oxidizing bacteria and filamentous algae. A comparison of the mineral deposition at this location with other terrestrial and oceanic deposits suggests that they were formed in a similar manner.

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“…(a) Iron oxide particle such as y-FeOOH cata lytically promotes manganese oxidation (Morgan and Stumm, 1965;Sung and Morgan, 1981).…”

Section: Resultsmentioning

confidence: 99%

“…(c) DO oxidizes Mn2+ chemically (by air oxi dation) under high pH (greater than 8.5), precipi tating Mn02 (Morgan and Stumm, 1965;Sung and Morgan, 1981).…”

Section: Resultsmentioning

confidence: 99%

A growing deposit of hydrous manganese oxide produced by microbial mediation at a hot spring, Japan.

et al. 1994

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“…Pankow and Morgan ( 1981) proposed that specific adsorption was responsible for the high affinity of Mn oxides for Mn 2+. A number of workers (Hem, 1963;Morgan and Stumm, 1964;Sung and Morgan, 1981) believed that the adsorbed Mn 2+ was oxidized to Mn 4+ through autocatalytic reaction by the oxide surfaces. The oxidation of adsorbed Mn 2+ on the oxide surfaces was suggested by Murray and Dillard (1979), who, using X-ray photoelectron spectroscopy, were unable to detect any Mn 2+ on the surface of birnessite after adsorption of Mn 2 § Whether the oxidation of Mn 2 § occurred during, just prior to, or after adsorption remains an enigma.…”

Section: Discussionmentioning

confidence: 99%

Transformations of Synthetic Birnessite as Affected by pH and Manganese Concentration

1994

Clays and clay miner.

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AImtract--The amount of Mn 2+ adsorbed or removed from solution by birnessite is several times greater than its reported cation exchange capacity. Extractability of the sorbed Mn 2+ decreases with aging. It is uncertain whether the sorbed Mn 2+ is oxidized on the surface or incorporated into the structure of birnessite. Using X-ray powder diffractometry and transmission electron microscopy, a study was conducted to examine the mineralogical alteration of birnessite after treatment with various concentrations of MnSO4 and solution pH.The sorbed Mn 2+ was not directly oxidized and remained on the birnessite surface. The sorption of Mn 2+ was followed by alteration ofbirnessite with the formation of new Mn minerals. The specific Mn minerals formed were governed by the pH of the reaction, and the rate of the transformation was determined by Mn 2+ concentration and pH. Nsutite and ramsdellite were identified at pH 2.4, cryptomelane at pH 4, groutite at pH 6, and mangarfite at pH 8. Other Mn minerals formed at these and other pH levels could not be identified. As the concentration of Mn in the solution decreased, the time required to form new minerals from the birnessite increased. The newly formed phases were the result of structural conversion since dissolution of birnessite and reprecipitation of new phases were not observed.

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“…The very low carbonate content of the (Sung and Morgan, 1981). Therefore it is said nodules and the highly oxidative terrestrial that Fe plays an important role on the evolution environment will reduce minor element contents and the growth of terrestrial ferro-manganese of these fractions.…”

Section: Resultsmentioning

confidence: 99%

Terrestrial ferro-manganese nodules formed in limestone areas of the Ryukyu islands II. Partitioning of major and minor chemical constituents determined by selective chemical leaching technique.

1985

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Selective chemical leaching technique has been applied to the study on the partitioning of major and minor constituents into individual mineral species in ferro-manganese nodules formed in limestone areas of the Ryukyu Islands.The technique includes the use of 25% CH3COOH, 1 M NH2OH-HCl-25 % CH3COOH and 30% H202 solutions.Treatment with 25% CH3COOH solution led to the leaching of 51% of Ca, 0.6% of Fe and 1.5% of Mn. Successive leaching with 1 M NH2OH-HCl-25% CH3000H solu tion led to the leaching of 32% of Fe and almost 100% of Mn. The rate of leaching is largely dependent on the mineral components in the nodules.Minor elements are concentrated in the ferro-manganese fraction which is leached with 1 M NH2OH•HCl-25% CH3COOH solution. The rate of leaching is 100% for Co, 93% for Cu, 87% for Pb, 82% for Cd, 76% for Ni and 45% for Zn. Some parts of the elements remained insoluble in the above solutions.The remained fraction may have been associated with either stable clay lattice structure or stable oxide forms of lithogenous origins.

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Oxidative removal of Mn(II) from solution catalysed by the γ-FeOOH (lepidocrocite) surface

Cited by 184 publications

References 23 publications

A growing deposit of hydrous manganese oxide produced by microbial mediation at a hot spring, Japan.

A growing deposit of hydrous manganese oxide produced by microbial mediation at a hot spring, Japan.

Transformations of Synthetic Birnessite as Affected by pH and Manganese Concentration

Terrestrial ferro-manganese nodules formed in limestone areas of the Ryukyu islands II. Partitioning of major and minor chemical constituents determined by selective chemical leaching technique.

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