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Infrared Vibrations of Hematite Formed from Aqueous- and Dry-Thermal Incubation of Si-Containing Ferrihydrite

Published online by Cambridge University Press:  02 April 2024

R. K. Vempati ,
R. H. Loeppert ,
H. Sittertz-Bhatkar  and
R. C. Burghardt
R. K. Vempati
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
R. H. Loeppert
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
H. Sittertz-Bhatkar
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
R. C. Burghardt
Affiliation:
Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas 77843
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Abstract

Ferrihydrite samples having Si/Fe molar ratios ranging from 0 to 1 were synthesized by the reaction of Fe2(SO4)3 and Na2SiO3 with NaOH to an equilibrium pH of 8.2. Hematite formed by incubating the ferrihydrite (Si/Fe molar ratios ≤0.05) at pH 12.5 and 91°C for 36 hr had a globular morphology. Hematite formed from Si-free ferrihydrite gave infrared (IR) bands at 548, 471, 397, and 337 cm−1, whereas, hematite formed from Si-containing ferrihydrite having 0.001 to 0.05 Si/Fe molar ratios gave broad IR bands at about 550, 450, and 330 cm−1. Ferrihydrite having Si/Fe molar ratios ≥0.10 did not transform to hematite following the aqueous-thermal treatment.

The ferrihydrite samples were thermally treated for 2 hr at consecutive 100°C intervals from 100° to 800°C. The Si-free ferrihydrite transformed at 300°C to poorly crystalline hematite. Transmission electron microscopic analyses indicated that the hematite consisted of aggregates of spheroidal particles of 20–80 Å cross sections. Broad IR bands were observed at 529 and 452 cm−1; however, after heating the sample to 800°C, the particle cross sections increased to about 150–600 Å, and additional IR bands were present at 378 and 325 cm−1. The differences in the IR patterns of hematite formed from ferrihydrite at 300° and 800°C were probably due to increases in particle size and aggregation and improved crystallinity of the hematite particles following the higher temperature treatment. The hematite formed by the thermal transformation of the ferrihydrite having a 0.01 Si/Fe molar ratio was also spheroidal, and IR vibrations were present at about 528 and 443 cm−1. An increase in the temperature of the thermal treatment, however, did not result in additional IR bands.

Differences in the IR vibrations of hematite formed during aqueous- and dry-thermal treatments of the ferrihydrite samples were probably due to differences in the particle size and morphology of the product. The Si content, due to its effect on particle size of the precursor and the prevention of sintering and particle growth of hematite, influenced the IR pattern of the product. Particle morphology and IR spectroscopy may therefore be useful indicators of the precursor of hematite and the conditions of hematite formation in soil.

Keywords

FerrihydriteHematiteInfrared spectroscopyMorphologySiliconThermal treatment
Type
Research Article
Information
Clays and Clay Minerals , Volume 38 , Issue 3 , June 1990 , pp. 294 - 298
Copyright
Copyright © 1990, The Clay Minerals Society

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References

Barron, V., Rendon, J. L., Torrent, J. and Serna, C. J., 1984 Relation of infrared, crystallochemical, and morphological properties of aluminum-substituted hematite Clays & Clay Minerals 32 475 – 479.CrossRefGoogle Scholar
Berreman, D. W., 1963 Infrared Absorption at Longitudinal Optic Frequency in Cubic Crystal Films Physical Review 130 6 2193 – 2198.CrossRefGoogle Scholar
Corjeno, J., 1987 Porosity evolution of thermally treated hydrous ferric oxide gel J. Colloidal Interface Sci 115 260 – 263.Google Scholar
Feitknecht, W. and Michaelis, W., 1962 Über die Hydrolyse von Eisen (III)-Perchlorat-Lösungen Heb. Chim. Acta 45 212 – 224.CrossRefGoogle Scholar
Fischer, W. R. and Schwertmann, U., 1975 The formation of hematite from amorphous iron(III) hydroxides Clay Miner 23 33 – 37.CrossRefGoogle Scholar
Herbillon, A. J. and An, J. T., 1969 Heterogeneity in sil-icon-iron mixed hydroxides J. Soil Sci 20 223 – 235.CrossRefGoogle Scholar
Hunt, J. M., Wisherd, M. P. and Bonham, L. C., 1950 Infrared absorption spectra of minerals and other inorganic compounds Anal. Chem 25 1169 – 1174.CrossRefGoogle Scholar
Matijevic, E. and Scheiner, P. J., 1978 Ferric hydrous oxide sols. III. Preparation of uniform particles by hydrolysis of Fe(III)-chloride, -nitrate, and -Perchlorate solutions J. Colloid Interface Sci 63 509 – 524.Google Scholar
Ozaki, S., Kratohvil, S. and Matijevic, E., 1984 Formation of monodispersed spindle-type hematite particles J. Colloid Interface Sci 63 509 – 524.Google Scholar
Rendon, J. L. and Serna, C. J., 1981 IR spectra of powder hematite: Effect of particle size and shape Clay Miner 16 375 – 381.CrossRefGoogle Scholar
Saraswat, I. P., Vajpei, A. C., Garg, V. K., Sharma, V. K. and Nam, P., 1980 Characterization and thermal trans-formation of ferric oxide hydrated gel J. Colloidal Interface Sci 73 373 – 380.CrossRefGoogle Scholar
Schwertmann, U. (1988) Some properties of soil and synthetic iron oxides in Iron in Soil and Clay Minerals, Stucki, J. W., Goodman, B. A. and Schwertmann, U., eds., Reidel, Dordrecht, The Netherlands, p. 893.Google Scholar
Serna, C. J. and Iglesias, J. E., 1986 Nature of protohae-matite and hydrohaematite J. Materials Sci. Lett 5 901 – 902.CrossRefGoogle Scholar
Serna, C. J., Ocana, M. and Iglesias, J. E., 1987 Optical properties of α-Fe2O3 microcrystals in the infrared J. Phys. C: Solid State Phys 20 473 184.CrossRefGoogle Scholar
Sidhu, P. S., 1988 Transformation of trace-element substituted maghemite to hematite Clays & Clay Minerals 36 31 – 38.CrossRefGoogle Scholar
Vempati, R. K. and Loeppert, R. H., 1989 Influence of structural and adsorbed Si on the transformation of synthetic ferrihydrite Clays & Clay Minerals 37 273 – 279.CrossRefGoogle Scholar
Vempati, R. K., Loeppert, R. H. and Cocke, D. L., 1990 Mineralogy and reactivity of amorphous Siferrihydrite Solid State Ionics (in press).CrossRefGoogle Scholar
Wilson, M. J., Russell, J. D., Tait, J. D., Clark, D. R., Fraser, A. R. and Stephen, I., 1981 A swelling hematite/layer silicate complex in weathering granite Clay Miner 16 261 – 277.CrossRefGoogle Scholar