Oxidation of Chromium(III) to (VI) by Manganese Oxides

Kim, Jae Gon; Dixon, J. B.; Chusuei, Charles C.; Deng, Youjun

doi:10.2136/sssaj2002.0306

Cited by 74 publications

(69 citation statements)

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“…However, the kinetics of Cr(III) oxidation by O 2 are extremely slow in natural settings (55,56). As a result, the most common oxidant for Cr(III) in Earth surface environments is Mn, in the form of Mn(III,IV) (hydr)oxides (15,(57)(58)(59)(60)(61). The kinetics of this process can be generally formulated as (62)(63)(64)(65):…”

Section: A Kinetic Framework For Cr(iii) and Mn(ii) Oxidationmentioning

confidence: 99%

Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals

Planavsky

Reinhard

Wang

et al. 2014

Science

628

469

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Low oxygen limited the rise of animals Oxygen levels in Earth's early atmosphere had an important influence on the evolution of complex life. Planavsky et al. analyzed the isotopic signature of chromium in sedimentary rocks from across the globe—a proxy for past oxygen levels. Oxygen levels in the mid-Proterozoic (1.6 billion to 900 million years ago) were very low: less than 0.1% of the modern atmosphere. These low levels were probably below the minimum oxygen requirements for the earliest animals, delaying their emergence and diversification. Science , this issue p. 635

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Section: A Kinetic Framework For Cr(iii) and Mn(ii) Oxidationmentioning

confidence: 99%

Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals

Planavsky

Reinhard

Wang

et al. 2014

Science

628

469

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“…Chromium(III) can be oxidized into Cr(VI) in soils, mostly by Mn oxides, especially quadrivalent Mn (Bartlett and James, 1979;Kim et al, 2002;Fendorf et al, 1993). It was reported that Cr(III) is oxidized by the moist soil after 1-4 days and then reduced (Bartlett and James, 1979).…”

Section: Transformation Of Cr Between Trivalent and Hexavalent Forms mentioning

confidence: 99%

“…Chromium(III) is essential to human health, and a stable and less soluble cation in soils, while Cr(VI), a class A human carcinogenic, is a soluble and mobile anion in soils. However, Cr(III) is oxidized into Cr(VI) by manganese oxides in soils (Kim et al, 2002). Chromium(VI) is reduced to Cr(III) by Fe(II), organic matter and sulfide (Wittbrodt and Palmer, 1995;Patterson et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Distribution, transformation and bioavailability of trivalent and hexavalent chromium in contaminated soil

Han

Sridhar

et al. 2004

Plant Soil

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“…They are some of the strongest naturally occurred oxidants in the environment and participate in a wide range of redox reactions with organic and inorganic chemical compounds in soils and natural waters (Shindo and Huang 1984;Sunda and Kieber 1994;Post 1999;Kim et al 2002;He et al 2010). Natural manganese oxides have high sorption capacities for numerous metal cations (e.g., Cu, Co, Ni, Zn, Pb, and Cd) and influence greatly the distribution and bioavailability of many toxic and essential elements in the environment (McKenzie 1989;Post 1999;Foster et al 2003;Stüben 2007).…”

Section: Introductionmentioning

confidence: 99%

Aging promotes todorokite formation from layered manganese oxide at near-surface conditions

et al. 2010

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Purpose Todorokite is one common manganese oxide in soils and sediments and is commonly formed from layered Nabuserite. Aging processes can alter the physicochemical properties of freshly formed Na-buserite in natural environments. However, it is not clear whether and how aging affects the formation of todorokites. In the present paper, Na-buserite with aging treatment was employed to prepare todorokite at atmospheric pressure to investigate the effects of aging treatment of Na-buserite on the formation of todorokite. Materials and methods Four aged Na-buserite samples, which are produced through oxidation of Mn 2+ in concentrated NaOH medium by O 2 with aging for 3, 6, 9, and 12 months, were employed to investigate the effects of aging processes on the transformation from Na-buserite to todorokite by Mg 2+ -templating reaction at atmospheric pressure. The manganese oxides were examined using X-ray diffraction (XRD), elemental analysis, determinations of the average manganese oxidation number, infrared spectroscopy (IR), and transmission electron microscopy (TEM). Results and discussion The XRD, IR, and elemental analyses indicate that aging treatment can alter the substructure of the freshly synthesized Na-buserite. During the aging process, some of the Mn(III) may migrate into the interlayer region or disproportionate to form Mn 2+ and Mn 4+ from the layer of Na-buserite and the concomitant formation of layer vacancies. The interlayer Mn 3+ or Mn 2+ occupied above or below the layer vacancy sites and become corner-sharing octahedral. XRD analyses and TEM clearly show that the transformation from Na-buserite to todorokite was promoted by aging treatments. The alterations of substructure of aged Na-buserites can promote the rearrangement of manganese to construct a tunnel structure during the transformation from layered manganese oxides to tunnel-structure todorokite at atmospheric pressure. Conclusions The transformation from Na-buserite to todorokite was promoted by aging treatments at atmospheric pressure, and it is more suitable to explore the origination of natural todorokite in Earth surface environments using aged layered manganese oxides.

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Oxidation of Chromium(III) to (VI) by Manganese Oxides

Cited by 74 publications

References 0 publications

Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals

Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals

Distribution, transformation and bioavailability of trivalent and hexavalent chromium in contaminated soil

Aging promotes todorokite formation from layered manganese oxide at near-surface conditions

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