title: In situ spectroscopic identification of neptunium(V) inner-sphere complexes on the hematite-water interface.
abstract: Hematite plays a decisive role in regulating the mobility of contaminants in rocks and soils. The Np(V) reactions at the hematite-water interface were comprehensively investigated by a combined approach of in situ vibrational spectroscopy, X-ray absorption spectroscopy and surface complexation modeling. A variety of sorption parameters such as Np(V) concentration, pH, ionic strength, and the presence of bicarbonate was considered. Time-resolved IR spectroscopic sorption experiments at the iron oxide-water interface evidenced the formation of a single monomer Np(V) inner-sphere sorption complex. EXAFS provided complementary information on bidentate edge-sharing coordination. In the presence of atmospherically derived bicarbonate the formation of the bis-carbonato inner-sphere complex was confirmed supporting previous EXAFS findings.1 The obtained molecular structure allows more reliable surface complexation modeling of recent and future macroscopic data. Such confident modeling is mandatory for evaluating water contamination and for predicting the fate and migration of radioactive contaminants in the subsurface environment as it might occur in the vicinity of a radioactive waste repository or a reprocessing plant.
authors.affiliation: Helmholtz-Zentrum Dresden - Rossendorf, Institute of Resource Ecology , Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Müller
authors.forename: Annett
authors.initials: A
authors.lastname: Gröschel
authors.forename: André
authors.initials: A
authors.lastname: Rossberg
authors.forename: Frank
authors.initials: F
authors.lastname: Bok
authors.forename: Carola
authors.initials: C
authors.lastname: Franzen
authors.forename: Vinzenz
authors.initials: V
authors.lastname: Brendler
authors.forename: Harald
authors.initials: H
authors.lastname: Foerstendorf
mesh_terms: D000251:Adenosine Triphosphatases; D002352:Carrier Proteins; D005290:Ferric Compounds / Q000737:chemistry*; D008565:Membrane Proteins; D025261:Mitochondrial Proton-Translocating ATPases; D009405:Neptunium / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D014867:Water / Q000737:chemistry; D014877:Water Pollution, Chemical; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002352:Carrier Proteins; D005290:Ferric Compounds; D008565:Membrane Proteins; D014867:Water; C000499:ferric oxide; D009405:Neptunium; D000251:Adenosine Triphosphatases; D025261:Mitochondrial Proton-Translocating ATPases; C020439:oligomycin sensitivity-conferring protein