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

Journal Article · Thu Nov 17 04:00:00 EST 2011 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es202445w· OSTI ID:1027659

Catalano, Jeffrey G; Luo, Yun; Otemuyiwa, Bamidele ^[1]

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1. WU

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{sup -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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSF
• OSTI ID: 1027659
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 20 Vol. 45; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
ADSORPTION
AQUEOUS SOLUTIONS
ARSENATES
FINE STRUCTURE
FRACTIONATION
GOETHITE
HEMATITE
IRON
IRON ISOTOPES
IRON OXIDES
ISOTHERMS
OXIDES
PHASE TRANSFORMATIONS
PRECIPITATION
RECRYSTALLIZATION
SORPTION
SPECTROSCOPY
TRANSFORMATIONS
X-RAY DIFFRACTION