Effect of Aqueous Fe(II) on Arsenate Sorption on Goethite and Hematite

Abstract

Biogeochemical iron cycling often generates systems where aqueous Fe(II) and solid Fe(III) oxides coexist. Reactions between these species result in iron oxide surface and phase transformations, iron isotope fractionation, and redox transformations of many contaminant species. Fe(II)-induced recrystallization of goethite and hematite has recently been shown to cause the repartitioning of Ni(II) at the mineral-water interface, with adsorbed Ni incorporating into the iron oxide structure and preincorporated Ni released back into aqueous solution. However, the effect of Fe(II) on the fate and speciation of redox inactive species incompatible with iron oxide structures is unclear. Arsenate sorption to hematite and goethite in the presence of aqueous Fe(II) was studied to determine whether Fe(II) causes substantial changes in the sorption mechanisms of such incompatible species. Sorption isotherms reveal that Fe(II) minimally alters macroscopic arsenate sorption behavior except at circumneutral pH in the presence of elevated concentrations (10⁻³ M) of Fe(II) and at high arsenate loadings, where a clear signature of precipitation is observed. Powder X-ray diffraction demonstrates that the ferrous arsenate mineral symplesite precipitates under such conditions. Extended X-ray absorption fine structure spectroscopy shows that outside this precipitation regime arsenate surface complexation mechanisms are unaffected by Fe(II). In addition, arsenate was found to suppress Fe(II) sorption through competitive adsorption processes before the onset of symplesite precipitation. This study demonstrates that the sorption of species incompatible with iron oxide structure is not substantially affected by Fe(II) but that such species may potentially interfere with Fe(II)-iron oxide reactions via competitive adsorption.

Arsenate and cadmium co-adsorption and co-precipitation on goethite

“…Arsenate adsorption was reported to decrease the surface zeta potential of the soils [16]. In another study of As(V) and Fe(II) adsorption on goethite, As(V) adsorption was also found to shift the surface potential to a more negative value and enhanced Fe(II) adsorption [34], which is consistent with our observation. Moreover, the different adsorption procedures result in different Cd sorption amount.…”

Influence of Fe2+-catalysed iron oxide recrystallization on metal cycling

“…As with haematite, Frierdich et al [36] observed incorporation of Ni 2 + into Fe 2 + -exposed goethite using XAS, with nickel in a co-ordination environment similar to that of nickel-doped goethite. In contrast, XAS indicated that As 5 + remained sorbed or precipitated as ferrous arsenate rather than being incorporated in goethite during Fe 2 + -induced recrystallization [56]. In contrast, XAS indicated that As 5 + remained sorbed or precipitated as ferrous arsenate rather than being incorporated in goethite during Fe 2 + -induced recrystallization [56].…”

“…For example, the incorporation of uranium in iron oxides has been suggested to make the uranium less resistant to oxidative mobilization [5,50]. [7,46,56]). [67]), as well as predicting the release of metals such as arsenic into water (e.g.…”

Metal concentrations and distribution in paint waste generated during bridge rehabilitation in New York State

“…At the same time, it is important to note that under the reducing conditions found in anoxic portions of landfills, iron oxides may be reduced, and release bound metals in the system (Charlatchka and Cambier, 2000;Ghosh et al, 2004). Iron cycling and metal sorption occurs at the interface for trace metals such as Pb and As (Catalano et al, 2011;Neumann et al, 2013).…”