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Improved methods for selective dissolution of manganese oxides from soils and rocks
Author(s) -
Neaman A.,
Waller B.,
Mouélé F.,
Trolard F.,
Bourrié G.
Publication year - 2004
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1046/j.1351-0754.2003.0545.x
Subject(s) - dissolution , manganese , chemistry , nitric acid , hydrogen peroxide , stoichiometry , inorganic chemistry , nuclear chemistry , hydroxylamine hydrochloride , hydroxylamine , organic chemistry
Summary Hydroxylamine hydrochloride (NH 2 OH‐HCl) and hydrogen peroxide (H 2 O 2 ) have been used in the past for selective dissolution of manganese oxide minerals. The methods reported, however, give poor recoveries. We tried to improve the methods in this respect. By stoichiometry, incomplete dissolution of Mn oxides is due to the lack of NH 2 OH‐HCl added or to the lack of acid added in the case of H 2 O 2 treatment. By increasing the amount of solution for a given amount of solid in the case of NH 2 OH‐HCl and by increasing the acid concentration in the case of H 2 O 2 treatment, we obtained rapid and complete dissolution of synthetic Mn oxides. The dissolution of natural samples, however, was slower than that of synthetic ones. Based on the results obtained, the improved methods are: (i) 0.1 m NH 2 OH‐HCl, non‐acidified, 2 hours' stirring, and 1 g solid in 2 litres solution; (ii) 30% H 2 O 2 in 0.5 m nitric acid, 0.5 hours' stirring, and 1 g solid in 1 litre solution. The improved methods achieved almost complete release of manganese from samples without decreasing the selectivity of dissolution.