Investigation of surface structures by powder diffraction: a differential pair distribution function study on arsenate sorption on ferrihydrite.
Differential pair distribution function (d-PDF) analysis of high energy powder X-ray diffraction data was carried out on 2-line ferrihydrite nanoparticles with arsenate oxyanions adsorbed on the surface to investigate the binding mechanism. In this analysis, a PDF of ferrihydrite is subtracted from a PDF of ferrihydrite with arsenate sorbed on the surface, leaving only correlations from within the surface layer and between the surface and the particle. As-O and As-Fe correlations were observed at 1.68 and 3.29 A, respectively, in good agreement with previously published EXAFS data, confirming a bidentate binuclear binding mechanism. Further peaks are observed in the d-PDF which are not present in EXAFS, corresponding to correlations between As and O in the particle and As-2nd Fe.
Harrington
Richard
R
Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, USA. richard.harrington@stonybrook.edu
Hausner
Douglas B
DB
Bhandari
Narayan
N
Strongin
Daniel R
DR
Chapman
Karena W
KW
Chupas
Peter J
PJ
Middlemiss
Derek S
DS
Grey
Clare P
CP
Parise
John B
JB