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Manganese oxides: Spectroscopic stud...

Princeton University.

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Manganese oxides: Spectroscopic studies of structure, reactivity and biogenic formation.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Manganese oxides: Spectroscopic studies of structure, reactivity and biogenic formation./
作者:	Oyerinde, Oyeyemi F.
面頁冊數:	135 p.
附註:	Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4513.
Contained By:	Dissertation Abstracts International68-07B.
標題:	Chemistry, Inorganic. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3273524
ISBN:	9780549136439

Manganese oxides: Spectroscopic studies of structure, reactivity and biogenic formation.
Oyerinde, Oyeyemi F.

Manganese oxides: Spectroscopic studies of structure, reactivity and biogenic formation. - 135 p.

Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4513.

Thesis (Ph.D.)--Princeton University, 2007.

The oxidation of naturally occurring Mn(II), catalyzed by microorganisms, is orders of magnitude faster than surface catalyzed abiotic oxidation. The resulting biogenic oxide minerals, common constituents of oceans, soils and sediments, play a key role in the biogeochemical cycles of metals and organic compounds, affecting their transport and fate via catalytic and oxidative processes. For a fundamental understanding of these biogeochemical effects, knowledge of the origin and structure of the oxides, along with the chemical nature of their interactions with environmental components is essential. Within this context, we have prepared and examined synthetic analogs to the biogenic manganese oxides, using a combination of different spectroscopic and chromatographic techniques to evaluate the environmental chemistry mediated by the oxides.

ISBN: 9780549136439Subjects--Topical Terms:

517253
Chemistry, Inorganic.

Manganese oxides: Spectroscopic studies of structure, reactivity and biogenic formation.
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502 $a Thesis (Ph.D.)--Princeton University, 2007.
520 $a The oxidation of naturally occurring Mn(II), catalyzed by microorganisms, is orders of magnitude faster than surface catalyzed abiotic oxidation. The resulting biogenic oxide minerals, common constituents of oceans, soils and sediments, play a key role in the biogeochemical cycles of metals and organic compounds, affecting their transport and fate via catalytic and oxidative processes. For a fundamental understanding of these biogeochemical effects, knowledge of the origin and structure of the oxides, along with the chemical nature of their interactions with environmental components is essential. Within this context, we have prepared and examined synthetic analogs to the biogenic manganese oxides, using a combination of different spectroscopic and chromatographic techniques to evaluate the environmental chemistry mediated by the oxides.
520 $a From the Raman spectroscopic structural characterization of synthetic colloidal oxides, we obtained two symmetric stretching frequencies between 570--650 cm-1 which reflect the Mn oxide surface and interior oxygen sites. Further analysis revealed a correlation between the intensity of these vibrational bands and an electronic charge transfer (O→Mn) transition, a sensitive probe of the colloid particle sizes. These results open up the possibility of exploring the effect of particle size variations on the environmental reactivity of manganese oxides with an emphasis on their interactions with surface adsorbates.
520 $a The adsorption of molybdenum on manganese oxides was examined by using UV resonance Raman spectroscopy (UVRR) to monitor the perturbation of equilibrium between the various environmentally relevant molybdenum species. At low concentrations (below 10-3 M), the likely species to be adsorbed on manganese oxides is the monomeric molybdic acid, H2MoO4 however, the molecular structure of H2MoO4 is elusive, since it is available only in dilute solutions. Using UVRR spectroscopy, the Mo=O stretching vibration of molybdic acid was detected at 919 cm-1. A combination of this finding with a density functional theory analysis of computed geometries and vibrational modes for various structures led to the proposal of a molecular structure of MoO3(H2O) 3 for the molybdic acid.
520 $a Detailed studies of xenobiotic degradation capabilities of manganese oxides were also explored by monitoring the breakdown products of atrazine, a common herbicide, using High Performance Liquid Chromatography (HPLC). The effects of pH and humidity on the MnO2 catalyzed degradation were quantified revealing an interplay between dealkylation and hydrolysis reactions. Dealkylation dominates at high pH, while hydrolysis dominates at low pH. Lowering the humidity accelerates both reactions, especially hydrolysis. These studies help to identify the conditions under which atrazine degradation on MnO 2 may be enhanced in contaminated environments.
520 $a Finally, an investigation of molecular pathways of bacterial Mn(II) oxidation by exosporium extracts of Bacillus sp. SG-1 spores was undertaken using a combination of Electron Paramagnetic Resonance (EPR) and time resolved UV--Vis absorption spectroscopies. Optimal conditions for detection of Mn (II) and Mn(III) using EPR spectroscopy were established and an EPR protocol has been developed for future inhibition studies. To further clarify mechanistic issues for the biomineralization of MnO2, several experiments have been proposed based on this protocol.
590 $a School code: 0181.
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