In Situ X-ray Absorption Spectroscopic Study of the Adsorption of Ni2+ on Fe3O4 Nanoparticles in Supercritical Aqueous Fluids

Abstract

In situ X-ray absorption spectroscopy (XAS) measurements were made on Fe3O4 nanoparticles in supercritical aqueous fluids to study their reactivity with Ni2+ ions and to investigate the structural properties of the reacted nanoparticles. XAS spectra were measured from Ni2+ added to an aqueous solution containing Fe3O4 nanoparticles at temperatures up to 500 °C. The XANES and the EXAFS data indicate that reactivity of Fe3O4 nanoparticles with Ni2+ ions is negligible to 300 °C but becomes significant in the 400-500 °C temperature range. Analysis of Ni K-edge extended X-ray absorption fine structure (EXAFS) using an atomic cluster model based on the spinel structure shows that Ni2+ adsorbs predominantly on octahedral sites of the surface of nanoparticles in aqueous fluids at 400-500 °C. The EXAFS structural results are consistent with diffusion of Ni into the near-surface region of the Fe3O4 nanoparticles in the aqueous fluid at 400 and 500 °C.

Department(s)

Physics, Astronomy, and Materials Science

Document Type

Article

DOI

https://doi.org/10.1021/jp2067793

Keywords

X-ray absorption near edge spectroscopy, nanoparticles, ions, extended X-ray absorption fine structure, fluids

Publication Date

2011

Journal Title

The Journal of Physical Chemistry C

Link to Full Text

Share

COinS