How Aluminum Substitution in Goethite affects Iron Release
EMSL Project ID
6901
Abstract
Goethite formed in terrestrial weathering environments often exhibit Alsubstitution for Fe, [Fe1-xAlxOOH] and can vary in Al content from x <
0.15 in hydromorphic environments to a maximum of x = 0.33 in subsurface
soils. The amount of Al substitution in goethite has a profound effect on
crystal size, texture, domain morphology, surface area, structural strain,
and other properties that influence the rate and mechanism of goethite
dissolution. To date, many studies have shown that the rate of Fe(III)
dissolution from mineral surfaces increases as a function of
Al-substitution in goethite (Cervini-Silva, J. and G. Sposito, Environ.
Sci. Technol., 2002, 36, 337). Cervini-Silva and Sposito 2002 have studied
the steady-state dissolution kinetics of Al-goethite in the presence of
the siderophore desferrioxamine B (DFO-B) and oxalate. Their results
indicated that Fe(III) dissolution increases with both Al-substitution and
DFO-B concentrations. For Al-substitution of x < 0.04 in goethite, a
synergism existed between the dissolution rates of oxalate and DFO-B. At
higher x, this synergism did not exist, indicating changes in Fe-OH
surface density. Finally, this study concluded that the there may be
Al(OH)3 clusters within the goethite structure because Al release by DFO-B
scaled approximately with Fe but was not affected by the concentration of
the siderophore.
An understanding of the structural changes upon Al for Fe
substitution in goethite can give insight into the properties that govern
the rate and mechanism of Fe(III) dissolution. Spectroscopic techniques,
such as infrared, x-ray absorption, and Mssbauer spectroscopy, are
well-suited techniques to probe the molecular chemistry of Al-substituted
goethite.
In this project, we propose to use Mssbauer spectroscopy couple
Attenuated Total Reflectance-Infrared (ATR-IR), x-ray absorption near edge
structure (XANES), and extended x-ray absorption fine structure (EXAFS)
spectroscopy to probe the structure of Al-substituted goethite and how al
distribution and sample crystallinity affects mineral dissolution.
Project Details
Project type
Exploratory Research
Start Date
2004-03-01
End Date
2006-11-01
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
A.R. Geanes, F.N. Smith, D. Mei, and E.C. Buck (2013) Modeling the interaction of radiolytic species with noble metal particles, in Proceedings of the 14th International High-Level Radioactive Waste Management Conference (IHLRWMC), April 28th-May 2nd, Albuquerque, NM.