Über Oxidhydroxide des vierwertigen Mangans mit Schichtengitter. 1. Mitteilung. Natriummangan (II, III)manganat(IV)

Abstract

The preparation of Na4Mn14O27, 9H2O (hitherto named manganomanganite or δ‐MnO2) by oxidation of a fresh Mn(OH)2 suspension in aqueous NaOH by molecular oxygen, and its probable structure are described. It is a double layer manganate (IV) structure resembling other manganates such as chalcophanite. Orthorhombic unit cell parameters are, a0 = 8,54, b0 = 15,39, c0 = 14,26 Å. In diluted nitric acid topotactical transition to manganese (III) manganate (IV), Mn7O13.5H2O (unit cell: a0 = 2,84, c0 = 7,27 Å; primitively hexagonal), and by prolonged digestion to nsutite, γ‐MnO2, occurs.

Secondary Phase Formation During Nuclear Waste-Glass Dissolution

“…In the discs, the basal fringes are arranged concentrically about a hollow core. Selected-area electron diffraction (SAED) patterns of individual crystals ( Figure 4) gave lattice constants consistent with those reported previously for birnessite Giovanoli et al, 1970). The wedge-shaped crystals were concentrated in inter-island regions between the smectite-birnessite islands.…”

“…Birnessite, a manganese oxyhydroxide, is capable o f incorporating a wide variety o f cations Chen et aL, 1986;Giovanoli et al, 1970). The composition of birnessite was determined by EMPA analysis of crystals peeled from the inter-island region of sample 546D.…”

“…In this regard, the observation of birnessite and a U-Ti-O phase within the alteration bands of glasses I and II is interesting. Birnessite exhibits a strong ionexchange preference for heavy metals (Giovanoli et aL, 1970) and can be converted to hollandite by heating. Hollandites have been used as a radionuclide-bearing phase in the synthetic waste form SYNROC (Ringwood and Kesson, 1988;Giovanoli et al, 1970;Giovanoli and Balmer, 1981).…”

“…Birnessite exhibits a strong ionexchange preference for heavy metals (Giovanoli et aL, 1970) and can be converted to hollandite by heating. Hollandites have been used as a radionuclide-bearing phase in the synthetic waste form SYNROC (Ringwood and Kesson, 1988;Giovanoli et al, 1970;Giovanoli and Balmer, 1981). The lack of uranium or rare earth uptake by precipitated birnessite in glass II, however, along with the appearance of the U-Ti-O phase, suggests that the formation of a stable actinide phase rather than ion exchange may be the primary mechanism for retarding radionuclide release into the environment.…”

A transmission electron microscope study of deep-sea manganese nodules

“…The weak rings through t.he spots are probably produced by tiny fragments of the same mineral. · Crystal in nodule powder DWIID-16 showirig "rafted" fine structure (compare· Giovanoli (1970)). Diffraction pattern identical with Na-birnessite.…”