Clays and Clay Minerals, Vol. 61, No. 1, 11–25, 2013.
Loading...
Authors
Bolanz, Ralph Michael
Blass, Ulrich
Ackermann, Sonia
Ciobota, Valerian
Rosch, Petra
Tarcea, Nicolae
Popp, Jurgen
Majzlan, Juraj
Issue Date
2011
Type
Article
Language
Keywords
Periodicals , Geology , Antimony , Arsenic , Ferrihydrite , Feroxyhyte , Goethite , Hematite , Iron Oxides , Phosphorous , Transformation , Tripuhyite
Alternative Title
The Effect Of Antimonate, Arsenate, And Phosphate On The Transformation Of Ferrihydrite To Goethite, Hematite, Feroxyhyte, And Tripuhyite
Abstract
Iron oxides, typical constituents of many soils, represent a natural immobilization mechanism for toxic elements. Most iron oxides are formed during the transformation of poorly crystalline ferrihydrite to more crystalline iron phases. The present study examined the impact of well known contaminants, such as P(V), As(V), and Sb(V), on the ferrihydrite transformation and investigated the transformation products with a set of bulk and nano-resolution methods. Irrespective of the pH, P(V) and As(V) favor the formation of hematite (a-Fe2O3) over goethite (a-FeOOH) and retard these transformations at high concentrations. Sb(V), on the other hand, favors the formation of goethite, feroxyhyte (d’-FeOOH), and tripuhyite (FeSbO4) depending on pH and Sb(V) concentration. The elemental composition of the transformation products analyzed by inductively coupled plasma optical emission spectroscopy show high loadings of Sb(V) with molar Sb:Fe ratios of 0.12, whereas the molar P:Fe and As:Fe ratios do not exceed 0.03 and 0.06, respectively. The structural similarity of feroxyhyte and hematite was resolved by detailed electron diffraction studies, and feroxyhyte was positively identified in a number of the samples examined. These results indicate that, compared to P(V) and As(V), Sb(V) can be incorporated into the structure of certain iron oxides through Fe(III)-Sb(V) substitution, coupled with other substitutions. However, the outcome of the ferrihydrite transformation (hematite, goethite, feroxyhyte, or tripuhyite) depends on the Sb(V) concentration, pH, and temperature.
Description
gsccm61102-bol.pdf-- 958KB
Citation
Clays and Clay Minerals, Vol. 61, No. 1, 11–25, 2013.
Publisher
License
Copyright © 2006-2018