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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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