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The effect of dry heating of synthetic 2-line and 6-line ferrihydrite: II. Surface area, porosity and fractal dimension

Published online by Cambridge University Press:  09 July 2018

P. G. Weidler  and
H. Stanjek
P. G. Weidler*
Affiliation:
Lehrstuhl für Bodenkunde, TU-Münehen/Weihenstephan, D-85350 Freising-Weihenstephan, Germany
H. Stanjek
Affiliation:
Lehrstuhl für Bodenkunde, TU-Münehen/Weihenstephan, D-85350 Freising-Weihenstephan, Germany
*
*Corresponding author; current address Institute for Terrestrial Ecology ETH Zurich/ CH-8952 Schlieren, Switzerland; e-mail: [email protected]
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Abstract

Nitrogen adsorption isotherms were measured on synthetic 2-line and 6-line ferrihydrites heated to 400 K, 500 K, and 600 K under dry conditions for different times ranging from 4 to 3000 h. Evaluation of specific surface area, microporosity and fractal dimension revealed that 2-line and 6-line ferrihydrites are highly microporous powders consisting of aggregates with corrugated interior and exterior surfaces. Furthermore, the surfaces of the single particles forming the aggregates have a smaller fractal dimension, i.e. a smoother appearance, than those of the entire aggregate. The diffusion of water lost during the heating process is influenced by the size of the micropores. The initial stage of the dehydration of the ferrihydrites can be described as similar to the process of Ostwald ripening.

Type
Research Article
Information
Clay Minerals , Volume 33 , Issue 2 , June 1998 , pp. 277 - 284
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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References

Avnir, D. & Jaroniec, M. (1989) An isotherm equation for adsorption on fractal surfaces of heterogeneous porous materials. Langmuir, 5, 1431–1433.CrossRefGoogle Scholar
Barrett, E.P., Joyner, L.G. & Halenda, P.P. (1951) The determination of pore volume and area distribution in porous substances. I. Computations from nitrogen isotherms. J. Am. Chem. Soc. 73, 373–380.CrossRefGoogle Scholar
Brunauer, S., Emmett, P.H. & Teller, E. (1932) Adsorption of gases in multimolecular Layers. J. Am. Chem. Soc. 60, 309–319.CrossRefGoogle Scholar
Childs, C.W. (1992) Ferrihydrite: A review of structure, properties and occurrence in relation to soils. Z. Pflanzenerniihr. Bodenk. 155, 441–448.CrossRefGoogle Scholar
Cornejo, J. (1987) Porosity evolution of thermally treated hydrous ferric oxide gel. J. Coll. Interf. Sci. 115, 260–263.CrossRefGoogle Scholar
Cornejo, J., Serna, C.J. & Hermosin, M.C. (1984) Nitrogen adsorption on synthetic ferrihydrite. J. Coll. lnterf Sci. 102, 101–106.CrossRefGoogle Scholar
de Boer, J.H., Lippens, B.G., Linsen, B.G., Broekhiff, J.C.P., van den Heuvel, A. & Osinga, Th.J. (1966) The t-curve of multimolecular N2-adsorption. J. Coll. Interf Sci. 21, 405–414.CrossRefGoogle Scholar
Eggleton, R.A. & Fitzpatrick, R.W. (1988) New data and revised structural model for ferrihydrite. Clays Clay Miner. 36(2), 111-124.Google Scholar
Fischer, W.R. & Schwertmann, U. (1975) The formation of hematite from amorphous iron(III)hydroxide. Clays Clay Miner. 23, 33–37.CrossRefGoogle Scholar
Johnston, J.H. & Lewis, D.G. (1983) A detailed study of the transformation of ferrihydrite to hematite in an aqueous medium at 92°. Geochim. Cosmochim. Acta, 47, 1823–1831.CrossRefGoogle Scholar
Jost, W. & Hauffe, K. (1972) Diffusion. Steinkopff Verlag, Darmstadt, 2. edn.CrossRefGoogle ScholarPubMed
Kabai, J. (1973) Determination of specific activation energies of metal oxides and metal oxides hydrates by measurement of the rate of dissolution. Acta. Chim. Acad. Scientiarium Hungaricae, 78, 57–73.Google Scholar
Karnaukhov, A.P. (1979) Simulation of porous materials. Pp. 301–311 in: Characterization of Porous Solids. (Gregg, S., Sing, K. & Stoeckli, H., editors). Society of Chemical Industries, London.Google Scholar
Ooi, K., Katoh, S. & Sugasaka, K. (1987) Pore structure of hydrous titanium (IV)-oxide. J. Coll. Interj. Sci. 119, 595.Google Scholar
Schwertmann, U. & Murad, E. (1983) Effect of pH on the formation of goethite and hematite from ferrihydrite. Clays Clay Miner. 31, 277–284.CrossRefGoogle Scholar
Sing, J.W., Everett D,H., Haul, R.A.W., Moscou, L., Pierotti, R.A., Rouquérol, J. & Siemieniewska, T. (1985) Reporting physisorption data for gas/solid systems. Pure Appl. Chem. 57, 603–619.Google Scholar
Stanjek, H. & Weidler, P.G. (1992) The effect of dry heating on the chemistry, surface area, and oxalate solubility of synthetic 2-line and 6-line ferrihydrites. Clay Miner. 27, 397–412.CrossRefGoogle Scholar
Towe, K. & Bradley, W.F. (1967) Mineralogical constitution of colloidal ‘hydrous ferric oxides'. J. Coll. Inter. Sci. 24, 384–392.CrossRefGoogle Scholar
Weidler, P.G. (1995) Oberfliächen und Porositäten synthetischer Eisenoxide. FhD thesis, TU München/Weihenstephan, Germany.Google Scholar
Wilke, K.Th. (1988) Kristallzüchtung. VEB Dtsch. Verlag der Wissenschaften, Berlin.Google Scholar
Willett, I.R., Chartres, C.J. & Nguyen, T.T. (1988) Migration of phosphate into aggregated particles of ferrihydrite. J. Soil Sci. 39, 275–282.CrossRefGoogle Scholar