Hostname: page-component-586b7cd67f-2plfb Total loading time: 0 Render date: 2024-11-22T14:48:37.587Z Has data issue: false hasContentIssue false
  • English
  • Français

Characteristics of Products from the Acid Ammonium Oxalate Treatment of Manganese Minerals

Published online by Cambridge University Press:  02 April 2024

Efraím Mendelovici  and
Amaya Sagarzazu
Efraím Mendelovici
Affiliation:
Materials Physico-Chemistry Laboratory, Department of Materials Science, IVIC, Apartado 21827, Caracas 1020A, Venezuela
Amaya Sagarzazu
Affiliation:
Materials Physico-Chemistry Laboratory, Department of Materials Science, IVIC, Apartado 21827, Caracas 1020A, Venezuela
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

To determine the parameters that control the attack of Mn minerals by acid ammonium oxalate in darkness (AAOD), rhodochrosite, pyrolusite, manganosite, hausmannite, and bixbyite were shaken with AAOD for 2 hr. These treatments were followed systematically by X-ray powder diffraction (XRD) and AAOD-extractable Mn analyses. About 5% of original hausmannite (surface area = 6 m2/g) remained in the solid residue of the AAOD treatment; however, if the hausmannite surface area was increased to 8 m2/g, by grinding, it completely dissolved in oxalate. Synthetic hausmannite of high surface area (37 m2/g) and rhodochrosite were completely dissolved by oxalate. Manganosite (1.5 m2/g) and especially pyrolusite (~ 1 m2/g) were more resistant to AAOD attack. Ground manganosite (4.2 m2/g) dissolved completely, but ground pyrolusite (7.2 m2/g) was only partially attacked by AAOD, inasmuch as about 25% of pyrolusite was found in the residue. An increase of the extraction time to 4 hr did not completely dissolve the ground pyrolusite.

As a result of the AAOD treatment, MnC2O4 · 3H2O and MnC2O4 · 2H2O precipitated from the oxalate solutions with all starting minerals, except pyrolusite (~ 1 m2/g), which only slightly dissolved. The seldom reported MnC2O4 · 3H2O phase was identified in residues of freshly extracted samples by its strong characteristic peak at 6.5.-6.6 Å, the intensity of which gradually decreased and disappeared over several days when the sample was exposed to ambient conditions (22°C and 70% relative humidity). The trihydrate phase also collapsed after heating AAOD-treated rhodochrosite at 50°C; α-MnC2O4 · 2H2O was identified as the main crystalline product. Heating the α-MnC2O4 · 2H2O product at 115°C overnight transformed most of it to MnC2O4. The color of the oxalate-treated samples ranged from pinkish-gray to black (7.5 YR); their surface area ranged from about 20 to 30 m2/g. The degree of transformation of Mn minerals by oxalate depended on the surface area and structural characteristics of the starting materials.

Keywords

Acid ammonium oxalateDissolutionGrindingManganese oxidesSurface areaX-ray powder diffraction
Type
Research Article
Information
Clays and Clay Minerals , Volume 39 , Issue 3 , June 1991 , pp. 264 - 269
Copyright
Copyright © 1991, The Clay Minerals Society

References

Blume, H. P. and Schwertmann, U., 1969 Genetic evaluation of profile distribution of aluminum, iron, and manganese oxides Soil Sci. Soc. Amer. Proc 33 438 – 444.CrossRefGoogle Scholar
Chao, T. T., 1972 Selective dissolution of manganese oxides from soils and sediments with acidified hydroxylamine hydrochloride Soil. Sci. Soc. Amer. Proc 36 764 – 768.CrossRefGoogle Scholar
Chao, T. T. and Theobald, P. K., 1976 The significance of secondary iron and manganese oxides in geochemical exploration Econ. Geol 71 1560 – 1569.CrossRefGoogle Scholar
Cornell, R. M. and Giovanoli, R., 1987 Effect of manganese on the transformation of ferrihydrite into goethite and jacobsite in alkaline media Clays & Clay Minerals 35 11 – 20.CrossRefGoogle Scholar
Deyrieux, R., Berro, C. and Péneloux, A., 1973 Contribution à l’étude des oxalates de certaines métaux bivalents (Part III) Bull. Soc. Chim 1 25 – 34.Google Scholar
Ebinger, M. H. and Schulze, D. G., 1989 Mn-substituted goethite and Fe-substituted groutite synthesized at acid pH Clays & Clay Minerals 37 151 – 156.CrossRefGoogle Scholar
Golden, D. C., Dixon, J. B. and Chen, C. C., 1986 Ion exchange, thermal transformations, and oxidizing properties of birnessite Clays & Clay Minerals 34 511 – 520.CrossRefGoogle Scholar
Huizing, A. A., van Hal, H. A. M. Kwestroo, W., Langereis, C. and van Losdregt, P. C., 1977 Hydrates of manga-nese(II) oxalate Mat. Res. Bull 12 605 – 611.CrossRefGoogle Scholar
JCPD., 1987 Powder Diffraction File, Inorganic Phases Swarthmore, Pennsylvania International Center for Diffraction Data.Google Scholar
Lind, C. J., 1988 Hausmannite (Mn3O4) conversion to manganite (γ-MnOOH) in dilute oxalate solution Environ. Sci. Technol 22 62 – 70.CrossRefGoogle ScholarPubMed
Mendelovici, E. and Sagarzazu, A., 1988 Thermal synthesis of hausmannite via manganese alkoxide Thermochim. Acta 133 93 – 100.CrossRefGoogle Scholar
Robin, J., 1953 Etude des oxalates métalliques comme matirès premières pour la préparation de solutions solides d’oxydes métalliques Bull. Soc. Chim 1078 – 1084.Google Scholar