Cation exchange in synthetic manganates: I. Alkylammonium exchange in a synthetic phyllomanganate

Abstract

On treatment with dodecylammonium chloride, a synthetic Na-saturated phyllomanganate undergoes a cation-exchange reaction in which the structure expands from a collapsed basal spacing of 7 ,~ or a hydrated one of 10 N to ~ 25-5 •. The exchange reaction is strongly influenced by the saturating cation in the original manganate and by the degree of hydration of the interlayer zone in which the exchangeable cations are located. Of the 12 cations tested, from Groups IA, IIA and lIB of the Periodic Table, only Co-manganate undergoes alkylammonium exchange when fully-dehydrated by evacuation. The results are discussed in the context of existing knowledge of the synthetic phyllomanganate and, by extrapolation, the potential value of the technique in the characterization of natural manganates has been assessed.

Characterization of Mn oxides in cemented streambed crusts from Pinal Creek, Arizona, U.S.A., and in hot-spring deposits from Yuno-Taki Falls, Hokkaido, Japan

“…Expansion and dehydration tests were particularly useful for studying these samples. Sample A did not show expansion from 10 Å to 26 Å, as would be expected for buserite during exposure to dodecyl ammonium chloride (Paterson et al 1986), but Sample B did. Yuno-Taki samples A and B dehydrated and contracted to 7 Å.…”

“…60 mL doubly distilled H 2 O in a Schott Duran bottle with a heat-resistant stopper (up to 180 ∞C) and left standing in an incubator at 100 ∞C for 100 h. After cooling, a sub-sample of each solid was analyzed by XRD while still wet, and a dried sample was prepared for electron microscopy. To test expandable characteristics of synthetic buserite (i.e., to determine whether the 10 Å spacing expands to 26 Å, which is a proof of a layered structure), another sub-sample was suspended in 20 mL of freshly prepared 0.1 M dodecylammonium chloride solution and left standing for 24 h, according to the method of Paterson et al (1986). After washing once, this sub-sample was analyzed by XRD.…”

Natural speciation of Ni, Zn, Ba, and As in ferromanganese coatings on quartz using X-ray fluorescence, absorption, and diffraction

“…The term buserite, which designates a 10 Å phyllomanganate with exchangeable cations and an expanding and contracting interlayer spacing Giovanoli and Brü tsch, 1979;Tejedor-Tejedor and Paterson, 1979;Golden et al, 1986;Paterson et al, 1986) is not used here because buserite is a two-layer hydrate form of birnessite and vernadite. Today it appears that there is no fundamental structural difference between buserite and its dehydration product and, consequently, the names birnessite (Jones and Milne, 1956) and vernadite (Betekhtin, 1940), which date back to long before buserite, are preferred.…”

Physicochemical and structural factors in the sulfuric acid leaching of nickel- and copper-bearing synthetic birnessites

“…[39,52,53] The doped divalent transition element may either occupy the vacant lattice sites in the MnO 6 octahedra, or substitute for Mn(II) in the MnO 6 octahedra and/or Mn(II) and Na + in the interlayer region. [13,53] Substitution of Mn(IV) by divalent ions is unlikely, because of a large difference in the ionic radii of Mn(IV) (0.053 nm) and Ni(II) (0.069 nm) and Cu(II) (0.073 nm) and a loss of CFSE (CFSEs of Mn(IV), Ni(II), and Cu(II) are 393, 122.2, and 90.4 kJ/mol, respectively). Substitution of Mn(II) (ionic radius 0.083 nm and CFSE equal to zero) by Ni(II) and Cu(II) is expected, due to similar ionic radii and a gain in CFSE.…”