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Title: Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

Abstract

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO 2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondary uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca 2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K + and Pb 2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since amore » comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Authors:
 [1];  [2];  [2];  [2];  [3]
  1. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Inst.
  2. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science
  3. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science, Dept. of Chemistry and Biochemistry
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1416495
Report Number(s):
LLNL-JRNL-725124
Journal ID: ISSN 0883-2927
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Geochemistry
Additional Journal Information:
Journal Volume: 87; Journal Issue: C; Journal ID: ISSN 0883-2927
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; uranium ore; uranium ore alteration; extraction chromatography; ICP-MS; rare-earth elements fractionation

Citation Formats

Balboni, Enrica, Spano, T, Cook, N, Simonetti, A, and Burns, P C. Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals. United States: N. p., 2017. Web. doi:10.1016/j.apgeochem.2017.10.007.
Balboni, Enrica, Spano, T, Cook, N, Simonetti, A, & Burns, P C. Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals. United States. doi:10.1016/j.apgeochem.2017.10.007.
Balboni, Enrica, Spano, T, Cook, N, Simonetti, A, and Burns, P C. 2017. "Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals". United States. doi:10.1016/j.apgeochem.2017.10.007.
@article{osti_1416495,
title = {Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals},
author = {Balboni, Enrica and Spano, T and Cook, N and Simonetti, A and Burns, P C},
abstractNote = {We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondary uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K+ and Pb2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.},
doi = {10.1016/j.apgeochem.2017.10.007},
journal = {Applied Geochemistry},
number = C,
volume = 87,
place = {United States},
year = 2017,
month =
}

Journal Article:
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  • The character of the alteration of lanthanoid composition corresponds to the assumed trend in the process of acidity change of mineral-forming solutions during orthite replacement. As a result of a comparison of concentration coefficients of individual rare earth elements, a conclusion is drawn concerning the considerably higher mobility and ability for concentration of the middle members of the lanthanoid series-Sm, Gd, and Dy-in comparison to its extreme mennbers in some secondary geochemical processes. (auth)
  • Rare earth element (REE) concentrations were measured in 5 well water samples and 3 springs located along a groundwater flow path in a shallow, tuffaceous alluvial aquifer from southern Nevada, USA. The REE concentrations in these groundwaters decrease in the direction of groundwater flow. A previous investigation demonstrated that REE solid-liquid phase partitioning coefficients (i.e., K{sub d}'s) for groundwaters from tuffaceous alluvial aquifers in southern Nevada are relatively high (mean K{sub d} = 10{sup 2.6}). The groundwater REE data, in conjunction with these K{sub d}'s support strong sorption of aqueous REEs to aquifer surface sites as the primary removal mechanismmore » of REEs from these groundwaters. In addition, relatively high aqueous REE concentrations occur at distinct locations along the groundwater flow path. The elevated REE concentrations are explained by addition of deeper groundwaters, influx of geothermal waters from a hot spring system, differences in solution complexation, and/or mixtures of regional and local recharge sources. Solution complexation modeling of REEs in the groundwaters indicate that carbonate complexes account for more than 99% of each REEs in solution. Moreover, groundwater Yb/Nd ratios (a measure of REE fractionation) are associated with alkalinity (HCO{sub 3}{sup {minus}} + CO{sub 3}{sup 2{minus}}; r = 0.71). The data and speciation model results indicate that REE fractionation (i.e., the observed heavy REE, HREE, enrichments compared to rock-sources) is controlled by formation of progressively stronger carbonate complexes in solution with increasing atomic number, which inhibits HREE sorption compared to light REEs (LREE); and a greater affinity for the LREEs to sorb to surface sites in the local tuffaceous alluvial aquifers compared to the HREEs.« less
  • Two meteorites were analyzed by PIXE with the Los Alamos Nuclear Microprobe. The enstatite achondrite Pena Blanca Spring and the ordinary chondrite St. Severin were chosen as likely candidates for use in /sup 244/Pu (t/sub 1/2/ = 82 my) cosmochronology and geochronology. These applications require the meteoritic minerals to have unfractionated actinides and lanthanides relative to cosmic elemental abundance ratios. The PIXE analyses produced evidence of actinide-lanthanide fractionation in Pena Blanca Spring oldhamite (CaS) whereas the St Severin phosphates, whitlockite and chlorapatite, do not exhibit this fractionation.