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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
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Abstract

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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