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

Abstract

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.

Synthesis of todorokite-type manganese oxide from Cu-buserite by controlling the pH at atmospheric pressure

“…Cu-OMS-1 had a stronger band at $3400 cm À1 than the hydrothermally synthesized Cu-todorokite, indicating that Cu-OMS-1 might possess more disordered water in the tunnel than the hydrothermally synthesized Cu-todorokite. The bands at 433, 504 and 763 cm À1 can be assigned to Mn-O stretching vibrations, and the absorbed band around 763 cm À1 can be assigned to the characteristic adsorbent of manganese oxides with tunnel structure [12].…”

“…Todorokite was firstly synthesized by Golden et al through autoclave treatment of Mg 2+ exchanged birnessite (Mg-buserite) under hydrothermal conditions [11]. Other hydrated inorganic divalent cations, such as Ni 2+ , Co 2+ , Cu 2+ , have successfully been used as templates for the synthesis of todorokites with different physical and chemical properties [12][13][14]. Over 25 ions, including group I/II metals and other main-group metals, transition metals, and lanthanides, have been ion-exchanged into stable Na-buserite by double-aging method, and todorokites have been made from these stable metal-buserites by hydrothermal treatment [15].…”

Oxidation of 1,2- and 1,4-Dihydroxybenzene by Birnessite in Acidic Aqueous Suspension

“…Figure 5 compares Mn dissolution with 1,2-DHB oxidized, revealing that the ratio of Mn-dissolved to 1,2-DHB oxidized was about 1.36. This mole excess of Mn release may have been a function of the oxidation state of Mn in the oxide, which for a synthetic birnessite has been reported to be 3.57+ (Golden et al, 1987). For that oxidation state, 1.27 moles of Mn 2+ could be released for each mole of 1,2-DHB oxidized, assuming no ability of the oxide to retain the reduced metal.…”

A consistent model for surface complexation on birnessite (−MnO2) and its application to a column experiment

“…The process of contraction and expansion is reversible, although after numerous cycles, water uptake tends to become incomplete (Giovanoli et al, 1970a). Other alkali elements likewise give a 7 Å structure upon drying while Mg 2ϩ , Ca 2ϩ and Ni 2ϩ forms maintain the 10 Å spacing (Golden et al, 1987;Kuma et al, 1994;Le Goff et al, 1996). Transition metal cations can also stabilize the 10 Å spacing (Golden et al, 1987;Giovanoli et al, 1975).…”