title: Investigation of surface structures by powder diffraction: a differential pair distribution function study on arsenate sorption on ferrihydrite.
abstract: 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.
authors.affiliation: Department of Geosciences, Stony Brook University, Stony Brook, New York 11794, USA. richard.harrington@stonybrook.edu
authors.forename: Richard
authors.initials: R
authors.lastname: Harrington
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Hausner
authors.forename: Narayan
authors.initials: N
authors.lastname: Bhandari
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Strongin
authors.forename: Karena W
authors.initials: KW
authors.lastname: Chapman
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Chupas
authors.forename: Derek S
authors.initials: DS
authors.lastname: Middlemiss
authors.forename: Clare P
authors.initials: CP
authors.lastname: Grey
authors.forename: John B
authors.initials: JB
authors.lastname: Parise