The Influence of Aluminum on Iron Oxides. Part I. The Influence of Al on Fe Oxide Formation from the Fe(II) System

R. M. Taylor and U. Schwertmann
CSIRO Division of Soils, Private Bag 2 Glen Osmond, South Australia 5064
Institut für Bodenkunde, Technische Universtät München, 8050 Freising, B.R.D.

Abstract: The influence of Al on the products formed by aerial oxidation at pH 5.5–7 and 20°C of Fe(II) chloride, sulfate and carbonate solutions, was examined. In all cases Al at levels Al/Al + Fe = 0.09–0.30 inhibited the formation of γ phases (lepidocrocite and maghemite) in favor of goethite under conditions where, in the absence of Al, these γ phases formed. The influence of Al in these laboratory studies was supported by field observations.

At higher levels of Al, ferrihydrite formation was favored. This effect of Al was seen to be the result of a slowing down in the hydrolysis/oxidation rate of the Fe(II) system.

The presence of Al not only changed the direction of mineral formation, but also caused the formation of Al substitued goethites which resembled in particle size and morphology the natural aluminiferous goethite extracted from a soil.

Key Words: Aluminum • Ferrihydrite • Goethite • Iron • Lepidocrocite • Maghemite

Clays and Clay Minerals; December 1978 v. 26; no. 6; p. 373-383; DOI: 10.1346/CCMN.1978.0260601
© 1978, The Clay Minerals Society
Clay Minerals Society (www.clays.org)