The presence of HFO influenced the
distribution of Al-hydroxypolymers in
the HFAO mixture and it influenced
their ordering. Conversely, Al influenced
the structural organisation in the Fe-
hydroxypolymers. X-ray and electron
diffraction data suggested that HFO
bears the structure of a 2-line ferrihydrite
whatever the concentration of Al (Fig.
➋
).
However, subtle changes occurred with
increasing Al. The EXAFS traces reflecting
the local environment around an iron
centre indicated improved symmetry
in the octahedral arrangement of the
oxygen ions around Fe. Fitting in k and R
space revealed that the number of Fe-Fe
linkages decreased as Al increases in
the system, indicative of a lesser degree
of polymerisation of the HFO nuclei, or
of a relative increase of surface Fe with
disrupted octahedra linkages. Finally
Raman spectra revealed vibration bands
arising in the HFAO spectra with increasing
Al, not assigned to either of the end-
members, faintly resembling akaganeite.
Influence of Al on HFO ordering
➊
Normalised Al K-edge XANES of (
a
) the samples (thick lines) and the corresponding linear combination fits
(thin lines), (
b
) the references.
LUCIA & SAMBA beamlines
ASSOCIATED PUBLICATION
Interaction of Fe(III) and Al(III) during
hydroxylation by forced hydrolysis: the nature
of Al-Fe oxyhydroxy co-precipitates
A. Hofmann*, D. Vantelon,
E. Montarges-Pelletier, F. Villain, O. Gardoll,
A. Razafitianamaharavo and J. Ghanbaja
Journal of Colloid and Interface Science
407 (2013), 76
REFERENCES
[1] R.M. Cornell, U. Schwertmann,
2003 The iron oxides. Structure, properties,
reactions, occurrences and uses,
Wiley-VCH ed., Weinheim
[2] A. C. Cismasu AC et al. Geochim.
Cosmochim. Acta 92 (2012), 275
[3] Y.T. Liu & D. Hesterberg,
Environ. Sci. Technol. 45 (2011), 6283
* Géosystèmes, Université Lille 1, CNRS,
UMR 8217, 59655-Villeneuve d’Ascq, France
CORRESPONDING AUTHOR
➋
Bright field TEM micrographs of Fe-Al co-precipitates with 0, 25, 75 and 100 % Al. (b) The ED pattern of HFO
is representative of 2-line ferrihydrite. (c) Lattice parameters d obtained from ED pattern for the HFAO series.
39
SYNCHROTRON
HIGHLIGHTS
2013
