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Spectroscopic study of a cryptomelane-type manganic acid exchanged by divalent transition-metal cations
Published online by Cambridge University Press: 31 January 2011
Abstract
A cryptomelane-type manganic acid (CMA) exchanged by divalent transition-metal cations was studied by means of x-ray diffraction, electron microscopic observation, electron spin resonance, infrared spectra, and electron spectroscopy for chemical analysis. Especially the last three techniques were decisive for the chemical speciation of manganese oxide systems. The findings clearly eliminated a redox process as the principal process for cation uptake in the α–MnO2 phase. Transition-metal cations are stoichiometrically exchanged on this material on an equivalent basis similarly with alkali and alkaline-earth metal cations, except Fe2+. The last ion is oxidized to Fe3+ through a redox reaction with Mn3+ in the a–MnO2. The CMA is a mixed-valence compound represented by H2Mn2IIIMn6IVO16 2.3H2O. Two moles of tunnel protons are exchangeable to give 2.70 mequiv/g for the calculated ion-exchange capacity.
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- Copyright © Materials Research Society 2001
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