Kinetics of Mn{sub 2}O{sub 3} digestion in H{sub 2}SO{sub 4} solutions

Journal Article · Mon Jun 15 00:00:00 EDT 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.02.034· OSTI ID:21370419

Walanda, Daud K; Lawrance, Geoffrey A ^[1]

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1. Discipline of Chemistry, University of Newcastle, Callaghan, NSW 2308 (Australia)

The kinetics of Mn{sub 2}O{sub 3} digestion in various H{sub 2}SO{sub 4} solutions (0.5-2.0 M) and at various temperatures (ambient to 80 deg. C) to form solid gamma-MnO{sub 2} and soluble Mn(II) have been examined using X-ray diffraction. Using a modified first-order Avrami expression to describe digestion kinetics, rate constants in the range 0.02-0.98 h{sup -1} were found for Mn{sub 2}O{sub 3} disappearance, and 0.03-0.42 h{sup -1} for gamma-MnO{sub 2} formation, with higher H{sub 2}SO{sub 4} concentrations and temperatures leading to faster conversion rates. Also, for a particular set of experimental conditions, the rate of gamma-MnO{sub 2} formation was always slower than Mn{sub 2}O{sub 3} disappearance. This was interpreted in terms of the solubility and stability of the soluble Mn(III) intermediated formed during the digestion. Activation energies for Mn{sub 2}O{sub 3} dissolution and gamma-MnO{sub 2} formation were also determined. - Graphical Abstract: Manganese dioxide phase diagram resulting from the acid digestion of Mn{sub 2}O{sub 3}.

• OSTI ID: 21370419
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 6; Other Information: DOI: 10.1016/j.jssc.2009.02.034; PII: S0022-4596(09)00095-4; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
AMBIENT TEMPERATURE
DISSOLUTION
HYDROTHERMAL SYNTHESIS
MANGANESE OXIDES
PHASE DIAGRAMS
REACTION KINETICS
SOLUBILITY
SOLUTIONS
STABILITY
SULFURIC ACID
TEMPERATURE RANGE 0273-0400 K
X-RAY DIFFRACTION
CHALCOGENIDES
COHERENT SCATTERING
DIAGRAMS
DIFFRACTION
DISPERSIONS
ENERGY
HOMOGENEOUS MIXTURES
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
INORGANIC COMPOUNDS
KINETICS
MANGANESE COMPOUNDS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
SCATTERING
SULFUR COMPOUNDS
SYNTHESIS
TEMPERATURE RANGE
TRANSITION ELEMENT COMPOUNDS