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. 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. 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. Sb(V), on the other hand, favors the formation of goethite, feroxyhyte (d’-FeOOH), and tripuhyite (FeSbO 4) depending on pH and Sb(V) concentration. Irrespective of the pH, P(V) and As(V) favor the formation of hematite (α-Fe 2O 3) over goethite (α-FeOOH) and retard these transformations at high concentrations. 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. Most iron oxides are formed during the transformation of poorly crystalline ferrihydrite to more crystalline iron phases.
Iron oxides, typical constituents of many soils, represent a natural immobilization mechanism for toxic elements.
0 kommentar(er)
