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Influence of Structural and Adsorbed Si on the Transformation of Synthetic Ferrihydrite

Published online by Cambridge University Press:  02 April 2024

R. K. Vempati  and
R. H. Loeppert
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
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Abstract

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The transformation of ferrihydrite to goethite and/or hematite, as influenced by the presence of co-precipitated Si, was investigated by infrared spectroscopy (IR), X-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Ferrihydrite samples having Si/Fe molar ratios ranging from 0 to 1 were synthesized by reacting Fe2(SO4)3 with NaOH to an equilibrium pH of 8.2 in the presence of Na2SiO3. The XRD pattern of the Si-free sample contained five distinct but weak peaks, whereas the patterns of ferrihydrite samples containing Si had only two broad bands. With an increase of the Si/Fe molar ratio from 0.10 to 1.0, the 2.54-Å XRD peak shifted to 2.97 Å, and broad IR bands were observed at 990 cm−1 (Si-O stretching region) and 450 cm−1 (silicate bending region). The intensities of both IR bands increased with increasing Si/Fe molar ratio.

Ferrihydrite samples were incubated at room temperature in sodium acetate/acetic acid buffer solutions at pH 3, 5, 7, and 10 and in CaCO3 suspension at pH 8.3 for 10 months. Additional samples were incubated at pH 12.5 at 24°, 40°, 60°, and 91°C for 36 hr. Room-temperature incubation of ferrihydrite samples having Si/Fe molar ratios ≥0.1 at pH 3 for one week resulted in the dissolution of Fe and the precipitation of silica gel. Ferrihydrite samples having Si/Fe molar ratios ≤0.05 transformed to poorly crystalline goethite during room-temperature incubation at pH 5. The rate of transformation and the degree of crystallinity of the product were inversely related to Si/Fe molar ratio, and, with heat treatment, were also dependent on incubation temperature. Siliceous ferrihydrite samples having Si/Fe molar ratios ≥0.10 did not transform to phases having greater crystallinity during incubation at either room temperature in buffered solutions at pH ≥7 for as long as 10 months or at pH 12.5 at 91°C for 36 hr. The XRD peak at 2.97 Å did not shift significantly during incubation procedures, providing evidence that the structure of the high-Si ferrihydrite was not significantly altered.

Keywords

AdsorptionCrystal structureFerrihydriteInfrared spectroscopySiliconSynthesisX-ray powder diffraction
Type
Research Article
Information
Clays and Clay Minerals , Volume 37 , Issue 3 , June 1989 , pp. 273 - 279
Copyright
Copyright © 1989, The Clay Minerals Society

Footnotes

1

Contribution from the Texas Agricultural Experiment Station as Journal Series TA 22847.

References

Cambier, P., 1986 Infrared study of goethites of varying crystallinity and particle size: I. Interpretation of OH and lattice vibration frequencies Clay Miner 21 191 – 200.CrossRefGoogle Scholar
Campbell, J. M. and Schwertmann, U., 1984 Iron oxide mineralogy of placic horizons J. Soil Sci 35 569 – 582.CrossRefGoogle Scholar
Carlson, L. and Schwertmann, U., 1980 Natural ferrihy-drites in surface deposits from Finland and their association with silica Geochim. Cosmochim. Acta 45 421 – 429.CrossRefGoogle Scholar
Childs, C. W., Downs, C. J. and Wells, N., 1982 Hydrous iron oxide minerals with short range order deposited in a spring/stream system, Tongariro National Park, New Zealand Aust. J. Soil Res 20 119 – 129.CrossRefGoogle Scholar
Eggleton, R. A. and Fitzpatrick, R. W., 1988 New data and a revised structural model for ferrihydrite Clays & Clay Minerals 36 111 – 124.CrossRefGoogle Scholar
Feitknecht, W. R. and Michaelis, W., 1962 Über die Hydrolyse von Eisen(III)-Perchlorat-Losungen Helv. Chim. Acta AS 212 – 224.CrossRefGoogle Scholar
Harrison, J. B. and Berkheiser, V. E., 1982 Anion interactions with freshly prepared hydrous iron oxides Clays & Clay Minerals 30 97 – 102.CrossRefGoogle Scholar
Herbillon, A. J. and Tran Vinh An, J., 1969 Heterogeneity in silicon-iron mixed hydroxides J. Soil Sci 20 223 – 235.CrossRefGoogle Scholar
Hingston, F. T., Posner, A. M. and Quirk, J. P., 1972 Anion adsorption by goethite and gibbsite J. Soil Sci 23 177 – 192.CrossRefGoogle Scholar
Jackson, M. L., 1969 Soil Chemical Analysis, Advanced Course 2nd ed. Madison, Wisconsin Dept. Soil Science, Univ. Wisconsin.Google Scholar
Lindsay, W. L., 1979 Chemical Equilibra in Soils New York Wiley.Google Scholar
Manning, P. G., Lum, K.R. and Wong, K.T., 1985 Origin and age of the ferrihydrite layer in Lake Ontario sediments Canadian Mineral 23 103 – 110.Google Scholar
McKeague, J. A. and Day, J. H., 1966 Dithionite- and oxalate-extractable Fe and Al as aids in differentiating various classes of soils Can. J. Soil Sci 46 13 – 22.CrossRefGoogle Scholar
Motts, C. J. B., Greenland, D. J. and Hayes, M. H. B., 1978 Anion and ligand exchange The Chemistry of Soil Processes New York Wiley 179 – 220.Google Scholar
Parfitt, R. L., Atkinson, R. J. and Smart, R St C, 1975 The mechanism of phosphate fixation by iron oxides Soil Sci. Soc. Amer. Proc 39 837 – 841.CrossRefGoogle 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
Schwertmann, U. and Fischer, W. R., 1973 Natural “amorphous” ferric hydroxide Geoderma 10 237 – 247.CrossRefGoogle Scholar
Schwertmann, U. and Thalmann, H., 1976 The influence of Fe(II), Si and pH on the formation of lepidocrocite and ferrihydrite during oxidation of aqueous FeCl2 solution Clay Miner 11 189 – 200.CrossRefGoogle Scholar
Vempati, R. K. and Loeppert, R. H., 1985 Structure and transformation of siliceous ferrihydrites: American Society of Agronomy Annual Meeting Agron. Abstracts 152.Google Scholar
Vempati, R. K. and Loeppert, R. H., 1986 Synthetic ferrihydrite as a potential Fe amendment in calcareous soils J. Plant Nutr 9 1039 – 1052.CrossRefGoogle Scholar
Vempati, R. K., Loeppert, R. H. and Cocke, D. L., 1989 Mineralogy and reactivity of Si-ferrihydrite Solid State Ionics .CrossRefGoogle Scholar