TY - JOUR
T1 - Chemical and structural characterization of As immobilization by nanoparticles of mackinawite (FeSm)
AU - Renock, Devon
AU - Gallegos, Tanya
AU - Utsunomiya, Satoshi
AU - Hayes, Kim
AU - Ewing, Rodney C.
AU - Becker, Udo
N1 - Funding Information:
This research was supported by a National Science Foundation NIRT Grant EAR-0403732 . Partial support for this work was provided by funds from the Strategic Environmental Research and Development Program (SERDP) Grant CU 1375 from the Department of Defense , and the Department of Army , Contract W912HQ-04-C-0035 . This paper has not been subject to agency review; it therefore does not necessarily reflect the sponsors' views.
PY - 2009/10/20
Y1 - 2009/10/20
N2 - The mobility and availability of arsenite, As(III), in anoxic environments is largely controlled by adsorption onto iron sulfides and/or precipitation of arsenic in solid phases. The interaction of As(III) with synthetic mackinawite (FeSm) in pH 5 and 9 suspensions was investigated using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), STEM elemental mapping, high resolution TEM, and X-ray photoelectron spectroscopy (XPS). At pH 5, arsenic sulfide phases precipitate among the FeSm particles as discrete particles that are an amorphous hydrous phase of arsenic sulfide. The oxidation state of As in the surface layers of the arsenic sulfide precipitates is 'realgar-like' based on XPS results showing that > 75% of the As 3d peak area is due to As with oxidation states between 0 and 2+. Discrete, arsenic sulfide precipitates are absent at pH 9, but elemental mapping in STEM-EDX mode shows that arsenic is uniformly distributed on the FeSm, suggesting that uptake is caused by the sorption of As(III) oxyanions and/or the precipitation of highly dispersed arsenic sulfides on FeSm. XPS also revealed that the FeSm that equilibrated without As(III) has a more oxidized surface composition than the sample at pH 9, as indicated by the higher concentration of O (∼ three times greater than that at pH 9) and the larger fraction of Fe(III) species making up the total Fe (2p3/2) peak. These findings provide a better understanding of redox processes and phase transitions upon As(III) adsorption on iron sulfide substrates.
AB - The mobility and availability of arsenite, As(III), in anoxic environments is largely controlled by adsorption onto iron sulfides and/or precipitation of arsenic in solid phases. The interaction of As(III) with synthetic mackinawite (FeSm) in pH 5 and 9 suspensions was investigated using high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), STEM elemental mapping, high resolution TEM, and X-ray photoelectron spectroscopy (XPS). At pH 5, arsenic sulfide phases precipitate among the FeSm particles as discrete particles that are an amorphous hydrous phase of arsenic sulfide. The oxidation state of As in the surface layers of the arsenic sulfide precipitates is 'realgar-like' based on XPS results showing that > 75% of the As 3d peak area is due to As with oxidation states between 0 and 2+. Discrete, arsenic sulfide precipitates are absent at pH 9, but elemental mapping in STEM-EDX mode shows that arsenic is uniformly distributed on the FeSm, suggesting that uptake is caused by the sorption of As(III) oxyanions and/or the precipitation of highly dispersed arsenic sulfides on FeSm. XPS also revealed that the FeSm that equilibrated without As(III) has a more oxidized surface composition than the sample at pH 9, as indicated by the higher concentration of O (∼ three times greater than that at pH 9) and the larger fraction of Fe(III) species making up the total Fe (2p3/2) peak. These findings provide a better understanding of redox processes and phase transitions upon As(III) adsorption on iron sulfide substrates.
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U2 - 10.1016/j.chemgeo.2009.08.003
DO - 10.1016/j.chemgeo.2009.08.003
M3 - Article
AN - SCOPUS:70349402558
VL - 268
SP - 116
EP - 125
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
IS - 1-2
ER -