New data on natural todorokites

Chukhrov, F. V.; Горшков, А. И.; Сивцов, А. В.; Beresovskaya, V. V.

doi:10.1038/278631a0

Cited by 42 publications

(37 citation statements)

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“…The variability of tunnel a dimension as observed by HRTEM was similar to that reported for natural samples (Chukhrov et al, 1979;Turner and Buseck, 1979;. The manganite impurity observed in the product obtained by autoclaving Mg-birnessite can be eliminated by employing an autoclaving time of 8 hr (Golden et al, 1986a).…”

Section: Discussionsupporting

confidence: 63%

Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment

Golden

1987

Clays and clay miner.

199

157

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Abstract--Investigations were conducted to determine the hydrothermal transformations of synthetic birnessite exchanged with different metal ions. Autoclaving in a Teflon-lined stainless steel pressure vessel at 155~ for 24 hr of Mg-, Ca-, La-, and Co-saturated birnessite yielded manganese minerals having 10-,~ X-ray powder diffraction (XRD) spacings. The autoclaved Mg-birnessite yielded a mineral identical to natural todorokite in its infrared (IR) spectrum and XRD patterns. High-resolution transmission electron microscopy (HRTEM) provided images having 10-, 12.5-, 15-, and 20-~ wide fringes indicating heterogeneous channel widths in the crystallographic a direction, and IR spectroscopy produced bands at 757, 635, 552, 515, 460, and 435 cm -~, confirming the product obtained by autoclaving Mg-birnessite to be todorokite. Prolonged autoclaving of Mg-birnessite yielded manganite (3,-MnOOH) as a by-product; manganite did not form when the autoclaving time was shortened to 8 hr. Also, when Ca-saturated samples were autoclaved, the product gave d-values of l0 ,/~, but the XRD lines were broad and heterogeneity of the channel sizes was evident from HRTEM observations. The Ca-derivative had an IR spectrum similar to that of natural todorokite. Images showing 10-A lattice fringes were observed by HRTEM for the Ni-saturated sample, which also produced an XRD pattern similar to that of the Mgsaturated sample. Co-and La-saturated samples did not form todorokite, although HRTEM of Lasaturated samples indicated some 10-• lattice fringes that were unstable in the electron beam. Birnessite saturated with Na, K, NH4, Cs, Ba, or Mn(lI) gave products having 7-A spacings upon autoclaving.

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Section: Discussionsupporting

confidence: 63%

Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment

Golden

1987

Clays and clay miner.

199

157

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“…1). TEM images also revealed intergrowths with todorokite having tunnels measuring 3X4, 3X5, and up to 3X9 octahedra in cross section (78,79).…”

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confidence: 99%

Manganese oxide minerals: Crystal structures and economic and environmental significance

Post

1999

Proc. Natl. Acad. Sci. U.S.A.

1,550

1,182

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Manganese oxide minerals have been used for thousands of years-by the ancients for pigments and to clarify glass, and today as ores of Mn metal, catalysts, and battery material. More than 30 Mn oxide minerals occur in a wide variety of geological settings. They are major components of Mn nodules that pave huge areas of the ocean f loor and bottoms of many fresh-water lakes. Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Their typical occurrence as fine-grained mixtures makes it difficult to study their atomic structures and crystal chemistries. In recent years, however, investigations using transmission electron microscopy and powder x-ray and neutron diffraction methods have provided important new insights into the structures and properties of these materials. The crystal structures for todorokite and birnessite, two of the more common Mn oxide minerals in terrestrial deposits and ocean nodules, were determined by using powder x-ray diffraction data and the Rietveld refinement method. Because of the large tunnels in todorokite and related structures there is considerable interest in the use of these materials and synthetic analogues as catalysts and cation exchange agents. Birnessite-group minerals have layer structures and readily undergo oxidation reduction and cation-exchange reactions and play a major role in controlling groundwater chemistry.

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“…During the last decade electron microscopy (EM), both scanning (SEM) and high resolution transmission (HRTEM), has been increasingly used in the study of these phases. At optical magnifications, terrestrial todorokite appears as prismatic crystals or as masses of parallel fibres (Chukhrov et al, 1978(Chukhrov et al, , 1980. Under the SEM marine todorokite has been identified as fibrous masses (Burns and Burns, 1978) and as platelets (Lallier-Verges and Clinard, 1983).…”

Section: Some Observations On the Chemical Composition Of Todorokitementioning

confidence: 99%

“…At the present time the term todorokite is widely accepted for the complex tunnel structure in both marine and terrestrial deposits which give an X-ray diffraction pattern with major lines at, or close to, 9.6, 4.8, 2.4, and 1.4 A (Burns and Burns, 1977). Whether this tunnel structure is the only phase in marine nodules giving an X-ray pattern similar to the above is still under investigation (Chukhrov et al, 1983). This paper is not directed at the question of todorokite crystal structure but at its chemical composition.…”

Section: Some Observations On the Chemical Composition Of Todorokitementioning

confidence: 99%

“…One difficulty with todorokite (and other manganese oxides) is that it commonly alters to a range of minerals including pyrolusite (Ostwald, 1982a), cryptomelane (Chukhrov et al, 1978), vernadite (Chukhrov et al, 1980), and possibly birnessite (Chukhrov et al, 1978), each mineral having its own suite of component elements. Thus both bulk analyses and electron probe microanalyses (EPMA) may be in error because of heterogeneity.…”

Section: Some Observations On the Chemical Composition Of Todorokitementioning

confidence: 99%

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Some observations on the chemical composition of todorokite

Ostwald

1986

Mineral. mag.

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New data on natural todorokites

Cited by 42 publications

References 1 publication

Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment

Transformation of Birnessite to Buserite, Todorokite, and Manganite under Mild Hydrothermal Treatment

Manganese oxide minerals: Crystal structures and economic and environmental significance

Some observations on the chemical composition of todorokite

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