Manganese oxides selective dissolution

Chao T. T. Selective dissolution of manganese oxides from soils and sediments with acidified hydroxylamine hydrochloride. Soil Sci Soc Am Proc 1972 36 704-768. 

Tokashiki, Y, J. B. Dixon, and D. C. Golden. 1986. Manganese oxide analysis in soils by combined x-ray diffraction and selective dissolution methods. Soil Sci. Soc. Am. J. 50 1079-1084. 

Various chemical extraction techniques have been introduced in order to selectively remove metals from the different adsorption or complexation sites of natural sediments (e.g., Tessier et al, 1979 Erel et al, 1990 Leleyter et al., 1999). It is, for example, shown by Leleyter et al. (1999) that between 20% and 60% of REE in various suspended river sediments are removed by successive extractions by water, by Mg(N03)2 (exchangeable fraction), sodium actetate (acid-soluble fraction), NH2OH - - HCl (manganese oxide dissolution) ammonium oxalate (iron oxide dissolution) and a mixture of H2O2 + HNO3 (oxidizable fraction). The complexity of... 

It has been reported that use of a 0.01 to 0.1 mol L hydroxylamine hydrochloride solution acidified at pH 2 causes the selective dissolution of manganese oxides with minimum extraction of iron oxides (Shuman, 1985 Kersten and Forstner, 1986 Berti and Cunningham, 1997). Nevertheless, the low pH value may lead to a partial release of TE bound to organic matter. The separated reducible fraction can thus be overestimated. An improved method for the selective dissolution of manganese oxides involving a nonacidified 0.1 mol L hydroxylamine solution at pH 3.6 as a leachant has been proposed by Neaman et al. (2004). Actually, the nonacidified hydroxylamine solution is not expected to dissolve considerable amounts of iron oxides, organic matter, or... 

---