TY - JOUR
T1 - Ni(II) complexation to amorphous hydrous ferric oxide
T2 - An X-ray absorption spectroscopy study
AU - Xu, Ying
AU - Axe, Lisa
AU - Boonfueng, Thipnakarin
AU - Tyson, Trevor A.
AU - Trivedi, Paras
AU - Pandya, Kaumudi
N1 - Funding Information: This material is based upon work supported by the DuPont Young Professor's Grant and the National Science Foundation under Grant No. BES 0089903. The authors thank James A. Dyer and Noel C. Scrivner of DuPont Engineering Technology for their input and support. We appreciate the technical support provided by staff at beamline X11A and X11B, National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL). Research carried out at NSLS BNL is supported in part by the US Department of Energy, Division of Materials Sciences and Division of Chemical Sciences, under Contract DE-AC02-98CH10886.
PY - 2007/10/1
Y1 - 2007/10/1
N2 - Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable α-Ni(OH)2 at a Ni(II) loading of 3.5 × 10-3 mol g-1. On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO6 octahedra when sorbed to HFO surfaces with Ni-O distances of 2.05-2.07 Å and Ni-Fe distances of 3.07-3.11 Å. This surface complex was observed by EXAFS study over 2.8 × 10-3 to 10-1 ionic strength, pH from 6 to 7, a Ni(II) loading of 8 × 10-4 to 8.1 × 10-3 mol g-1 HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni2+ was not observed to substitute for Fe3+ in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface.
AB - Ni(II) sorption onto iron oxides and in particular hydrous ferric oxide (HFO) is among the important processes impacting its distribution, mobility, and bioavailability in environment. To develop mechanistic models for Ni, extended X-ray absorption fine structure (EXAFS) analysis has been conducted on Ni(II) sorbed to HFO. Coprecipitation revealed the formation of the metastable α-Ni(OH)2 at a Ni(II) loading of 3.5 × 10-3 mol g-1. On the other hand, Ni(II) formed inner-sphere mononuclear bidentate complexes along edges of FeO6 octahedra when sorbed to HFO surfaces with Ni-O distances of 2.05-2.07 Å and Ni-Fe distances of 3.07-3.11 Å. This surface complex was observed by EXAFS study over 2.8 × 10-3 to 10-1 ionic strength, pH from 6 to 7, a Ni(II) loading of 8 × 10-4 to 8.1 × 10-3 mol g-1 HFO, and reaction times from 4 hours to 8 months. The short- and long-range structure analyses suggest that the presence of Ni(II) inhibited transformation of the amorphous iron oxide into a more crystalline form. However, Ni2+ was not observed to substitute for Fe3+ in the oxide structure. This study systematically addresses Ni(II) adsorption mechanisms to amorphous iron oxide. The experimentally defined surface complexes can be used to constrain surface complexation modeling for improved prediction of metal distribution at the iron oxide/aqueous interface.
KW - Adsorption
KW - Amorphous oxide
KW - EXAFS
KW - Hydrous ferric oxide
KW - Nickel
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U2 - 10.1016/j.jcis.2007.05.037
DO - 10.1016/j.jcis.2007.05.037
M3 - Article
C2 - 17561066
SN - 0021-9797
VL - 314
SP - 10
EP - 17
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
IS - 1
ER -