XPS STUDY OF REDUCTIVE DISSOLUTION OF 7#9-BIRNESSITE BY H3ASO3, WITH CONSTRAINTS ON REACTION MECHANISM - PART 1. EXAFS STTUDIES OF THE GEOMETRY OF COPRECIPITATED AND ADSORBED ARSENATE
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dc.contributor.author | Nesbitt H.W. | |
dc.contributor.author | Canning G.W. | |
dc.contributor.author | Bancroft G.M. | |
dc.date.accessioned | 2020-12-29T05:12:01Z | |
dc.date.available | 2020-12-29T05:12:01Z | |
dc.date.issued | 1998 | |
dc.identifier | https://elibrary.ru/item.asp?id=77483 | |
dc.identifier.citation | Geochimica et Cosmochimica Acta, 1998, , 12, 2097-2110 | |
dc.identifier.issn | 0016-7037 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/21645 | |
dc.description.abstract | Reductive dissolution of synthetic birnessite (MnO1.7(OH)0.25 or MnO1.95) by arsenious acid (H3AsO3) proceeds in two steps. The first entails reduction of Mn(IV) to Mn(III), with stoichiometry: 2MnO2+H3AsO3=2MnOOH*+H3AsO4H3AsO3 then attacks MnOOH* according to the stoichiometric reaction: 2MnOOH*+H3AsO3=2MnO+H3AsO4+H2O, where MnOOH* is an intermediate reaction product. Mn(II) is released ultimately to solution. Most importantly, one electron is transferred to each metal ion per reaction step. A Mn(III) component of the original, synthetic birnessite also undergoes reductive dissolution independently of, and at a different rate than, reduction of MnOOH*.X-ray Photoelectron Spectroscopy (XPS) demonstrates formation of an intermediate reaction product composed of Mn(III), hydroxyl, and H2O (here represented as MnOOH*). MnOOH* increases to a maximum value and subsequently decreases, as expected of an intermediate reaction product of a consecutive reaction scheme. Seven reactions are required to represent adequately reductive dissolution of birnessite. These include redox and sorption reactions. A Monte Carlo simulation successfully reproduces the major features of both XPS and previously published leach-rate results.Reductive dissolution of birnessite may proceed either via a classic electron transfer mechanism by which a bidentate surface complex forms, or via a substitution reaction mechanism, by which a monodentate surface complex forms. X-ray absorption spectroscopic (XAS) studies may be used to identify the appropriate mechanism. | |
dc.title | XPS STUDY OF REDUCTIVE DISSOLUTION OF 7#9-BIRNESSITE BY H3ASO3, WITH CONSTRAINTS ON REACTION MECHANISM - PART 1. EXAFS STTUDIES OF THE GEOMETRY OF COPRECIPITATED AND ADSORBED ARSENATE | |
dc.type | Статья |
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