Hostname: page-component-586b7cd67f-vdxz6 Total loading time: 0 Render date: 2024-11-23T05:41:30.421Z Has data issue: false hasContentIssue false

Micropore formation in heated synthetic Al-goethites from a ferrous system

Published online by Cambridge University Press:  09 July 2018

H. D. Ruan
Affiliation:
Soil Science and Plant Nutrition, Faculty of Agriculture, University of Western Australia, Nedlands 6907, Australia
R. J. Gilkes
Affiliation:
Soil Science and Plant Nutrition, Faculty of Agriculture, University of Western Australia, Nedlands 6907, Australia

Abstract

Nitrogen adsorption and desorption isotherms were obtained for microcrystalline, platy crystals of synthetic Al-substituted goethites synthesized from the ferrous system and heated to 260°C. Specific surface area, cumulative pore area and frequency of mesopore wall-separations of 2–15 nm in size increased as Al substitution increased. Nanometre-size micropores developed at heating temperatures between 200 and 240°C and decreased during the growth of hematite crystals between 240 and 260°C. Aluminium substitution had little effect on micropore development and a moderate effect on mesopore development. The increases in micropore volume and specific surface area due to heating are much smaller than is reported in the literature for large, lath-like crystals of goethite that develop abundant slit-shaped micropores.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1996

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Brunauer, S., Deming, L.S., Deming, W.E. & Teller, E. (1940) On a theory of the van der Waals adsorption of gasses. J. Am. Chem. Soc. 62, 17231732.Google Scholar
De Boer, J.H. (1958) The Structure and Properties of Porous Materials (Everett, D.H. & Stone, F.S., editors). Butterworth, London.Google Scholar
Fey, M.B. & Dixon, J.B. (1981) Synthesis and properties of poorly crystalline hydrated aluminous goethites. Clays Clay Miner. 29, 91100.Google Scholar
Goss, C.J. (1987) The kinetics and reaction mechanism of the goethite to hematite transformation. Mineral. Mag. 51, 437451.CrossRefGoogle Scholar
Naono, H. & Fuiiwara, R. (1980) Micropore formation due to decomposition of acicular microcrystals of α-FeOOH. J. Colloid Interf. Sci. 73, 404415.Google Scholar
Naono, H., Nakai, K., Sueyoshi, T. & Yagi, H. (1987) Porous texture in hematite derived from goethite: Mechanism of thermal decomposition of goethite. J. Colloid Interf. Sci. 120, 439450.Google Scholar
Paterson, E. (1977) Specific surface area and pore structure of allophanic soil clays. Clay Miner. 12, 19.Google Scholar
Rendon, J.L., Cornejo, J., De Arambarri, P. & Serna, C.J. 1983) Pore structure of thermally treated goethite (α-FeOOH). J. Colloid Interf. Sci. 92, 508516.CrossRefGoogle Scholar
Ruan, H.D & Gilkes, R.J. (1995) Dehydroxylation of aluminous goethite: unit cell dimensions, crystal size and surface area. Clays Clay Miner. 43, 196–211.CrossRefGoogle Scholar
Schulze, D.G. & Schwzrtmann, U. (1987) The influence of aluminium on iron oxides: XIII. properties of goethites synthesised in 0.3 M KOH at 25C. Clay Miner. 22, 8392.Google Scholar
Sills, I.D., Aylmore, L.A.G. & Quirk, J.P. (1973) A pore size distribution analysis of illite-kaolinite mixtures. Soil Sci. 24, 480490.Google Scholar
Taylor, H.F.W. (1962) Homogeneous and inhomogeneous mechanisms in the dehydroxylation of minerals. Clay Miner. Bull. 5, 45–55.Google Scholar
Watari, F., Delavignette, P., Van Landuyt, J. & Amelinckx, S. (1983) Electron microscopic study of dehydration transformations. Part III: High resolution observation of the reaction process FeOOH → Fe2O3. J. Solid State Chem. 48, 4964.Google Scholar