Ni(II) complexation to amorphous hydrous ferric oxide: An X-ray absorption spectroscopy study

Document Type

Article

Publication Date

10-1-2007

Abstract

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. © 2007 Elsevier Inc. All rights reserved.

Identifier

34547550508 (Scopus)

Publication Title

Journal of Colloid and Interface Science

External Full Text Location

https://doi.org/10.1016/j.jcis.2007.05.037

ISSN

00219797

PubMed ID

17561066

First Page

10

Last Page

17

Issue

1

Volume

314

Grant

DE-AC02-98CH10886

Fund Ref

National Science Foundation

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