title: Molybdenum speciation in uranium mine tailings using X-ray absorption spectroscopy.
abstract: Uranium (U) mill tailings in northern Saskatchewan, Canada, contain elevated concentrations of molybdenum (Mo). The potential for long-term (>10,000 years) mobilization of Mo from the tailings management facilities to regional groundwater systems is an environmental concern. To assist in characterizing long-term stability, X-ray absorption spectroscopy was used to define the chemical (redox and molecular) speciation of Mo in tailings samples from the Deilmann Tailings Management Facility (DTMF) at the Key Lake operations of Cameco Corporation. Comparison of Mo K near-edge X-ray absorption spectra of tailings samples and reference compounds of known oxidation states indicates Mo exists mainly as molybdate (+6 oxidation state). Principal component analysis of tailings samples spectra followed by linear combination fitting using spectra of reference compounds indicates that various proportions of NiMoO(4) and CaMoO(4) complexes, as well as molybdate adsorbed onto ferrihydrite, are the Mo species present in the U mine tailings. Tailings samples with low Fe/Mo (<708) and high Ni/Mo (>113) molar ratios are dominated by NiMoO(4), whereas those with high Fe/Mo (>708) and low Ni/Mo (<113) molar ratios are dominated by molybdate adsorbed onto ferrihydrite. This suggests that the speciation of Mo in the tailings is dependent in part on the chemistry of the original ore.
authors.affiliation: Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, Canada. joe377@mail.usask.ca
authors.forename: Joseph
authors.initials: J
authors.lastname: Essilfie-Dughan
authors.forename: Ingrid J
authors.initials: IJ
authors.lastname: Pickering
authors.forename: M Jim
authors.initials: MJ
authors.lastname: Hendry
authors.forename: Graham N
authors.initials: GN
authors.lastname: George
authors.forename: Tom
authors.initials: T
authors.lastname: Kotzer
mesh_terms: D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry; D008906:Mining; D008982:Molybdenum / Q000032:analysis / Q000737:chemistry*; D010084:Oxidation-Reduction; D025341:Principal Component Analysis; D012525:Saskatchewan; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry*; D014501:Uranium / Q000032:analysis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012989:Soil Pollutants; D014501:Uranium; D008982:Molybdenum