Manganese oxyhydroxide

Belzile, N. Chen,Y.-W. Wang, Z. (2001) Oxidation of antimony (111) by amorphous iron and manganese oxyhydroxides. Chem. Geol. 

Tessier, A. Fortin, D. Belzile, N. DeVitre, R.R. Leppard, G.G. (1996) Metal sorption to di-agenetic iron and manganese oxyhydroxides and associated organic matter Narrowing the gap between field and laboratory measurements. Geochim. Cosmochim. Acta 60 387-404... 

Manganese oxyhydroxides formed in the vadose zone undergo reduction by organic reduction similar to the general eq 5 (21). 

Jackson, T.A. and Bistricki, T. (1995) Selective scavenging of copper, zinc, lead, and arsenic by iron and manganese oxyhydroxide coatings on plankton in lakes polluted with mine and smelter wastes results of energy dispersive X-ray micro- analysis. Journal of Geochemical Exploration, 52(1-2), 97-125. 

The coupons were contacted for 24 h with a solution (termed KTOX) containing 0.1 mol/L potassium tetraoxalate and 0.1 mol/L hydroxylamine hydrochloride to remove radionuclides associated with iron and manganese oxyhydroxides ... 

In operationally defined speciation the physical or chemical fractionation procedure applied to the sample defines the fraction isolated for measurement. For example, selective sequential extraction procedures are used to isolate metals associated with the water/acid soluble , exchangeable , reducible , oxidisable and residual fractions in a sediment. The reducible, oxidisable and residual fractions, for example, are often equated with the metals associated, bound or adsorbed in the iron/manganese oxyhydroxide, organic matter/sulfide and silicate phases, respectively. While this is often a convenient concept it must be emphasised that these associations are nominal and can be misleading. It is, therefore, sounder to regard the isolated fractions as defined by the operational procedure. Physical procedures such as the division of a solid sample into particle-size fractions or the isolation of a soil solution by filtration, centrifugation or dialysis are also examples of operational speciation. Indeed even the distinction between soluble and insoluble species in aquatic systems can be considered as operational speciation as it is based on the somewhat arbitrary definition of soluble as the ability to pass a 0.45/Am filter. 

In addition to their use in the functional speciation role, selective extraction methods have been used to target element species in soil, or elements bound to, or associated with, particular soil phases or compounds. Examples include the use of extractants to release, for determination, metals on exchange sites, or metals bound or associated with soil iron or manganese oxyhydroxides or with soil organic matter. Most of these extractants are, however, less specific than intended and may extract species from other phases. Such extractants, however, are commonly, and conveniently, designated by their target species, e.g. extractable metal species or carbonate-bound species, but should more strictly be regarded as examples of speciation in which the species are operationally defined, i.e. by the method used to isolate them. 

Research conducted at Washington State University, as well as in situ applications by commercial entities, has indicated that stabilization of hydrogen peroxide is necessary for effective subsurface injection [39]. Without stabilization, added peroxide decomposes rapidly through interaction with iron oxyhydroxides, manganese oxyhydroxides, dissolved metals, and enzymes (e.g., peroxidase and catalase). Some of these peroxide decay pathways involve nonhydroxyl radical-forming mechanisms, and therefore are especially detrimental to Fenton oxidation systems. 

Davranche, M. and Bollinger, J., Heavy metals desorption from synthesized and natural iron and manganese oxyhydroxides Effect of reductive conditions, J. Colloid Interface Sci., 227, 531, 2000. 

When all nitrate is depleted, iron oxyhydroxides, Fe(OH)3, and manganese oxyhydroxides, Mn(OH)4, often represented as Mn02, serve as oxidants. These oxides are very common in soils and sediments. Iron reduction proceeds as follows ... 

A similar reaction using manganese oxyhydroxides can occur the AG° is — 30.3 kcal/mol. For the same concentrations of CH20 and H+ as previously, and with 10 M Mn4+, AG, is — 24.3 kcal/mol at 25°C. Although manganese reduction is energetically more favorable than iron reduction, manganese is much less abundant than iron in most environments, and therefore iron (III) is likely to be the more important oxidant. 

Suboxic metabolism, which includes nitrate, manganese and iron reduction, does not generally seem to form a discrete layer due to the relatively low levels of nitrate available under natural conditions and the insoluble nature of manganese oxyhydroxides and iron oxides. These reactions appear to be restricted, where they are apparent at all, to micro-environments, but since, of the reduction reactions in Table 6.1, they are the only ones to generate alkaline conditions, they may be important for the precipitation and preservation of carbonate minerals. 

The most commonly found manganese mineral in soils is birnessite, with lithiophorite, the other manganese oxyhydroxide listed in Table 1.2, restricted largely to acidic soils. Birnessite contains sheets of MnO octahedra linked in some fashion with Mn(III), Mn(II), Na(I), and Ca(II) ions coordinated to both hydroxyl groups and water molecules. In lithiophorite, sheets of MnO octahedra alternate with sheets of 0.67 0.33 octahedra. ... 

Oxygen isotope resnlts may be affected (and the nickel pyrolysis tube contaminated) if iron or manganese oxyhydroxides are present (often indicated by distinctive reddish or orange-brown colour of the final cellulose concentrate) and should be removed using the following leach solution ... 

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