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Title: Competitive Incorporation of Perrhenate and Nitrate into Sodalite

Nuclear waste storage tanks at the Hanford site in southeastern Washington have released highly alkaline solutions, containing radioactive and other contaminants, into subsurface sediments. When this waste reacts with subsurface sediments, feldspathoid minerals (sodalite, cancrinite) can form, sequestering pertechnetate ( 99TcO 4 ) and other ions. This study investigates the potential for incorporation of perrhenate (ReO 4 ), a chemical surrogate for 99TcO 4 , into mixed perrhenate/nitrate (ReO 4 /NO 3 ) sodalite. Mixed-anion sodalites were hydrothermally synthesized in the laboratory from zeolite A in sodium hydroxide, nitrate, and perrhenate solutions at 90 °C for 24 h. The resulting solids were characterized by bulk chemical analysis, X-ray diffraction, scanning electron microscopy, and X-ray absorption near edge structure spectroscopy (XANES) to determine the products’ chemical composition, structure, morphology, and Re oxidation state. The XANES data indicated that nearly all rhenium (Re) was incorporated as Re(VII)O 4 . The nonlinear increase of the unit cell parameter with ReO 4 /NO 3 ratios suggests formation of two separate sodalite phases in lieu of a mixed-anion sodalite. The results reveal that the sodalite cage is highly selective toward NO 3 over ReO 4 . Calculated enthalpy and Gibbs free energy ofmore » formation at 298 K for NO 3 - and ReO 4 -sodalite suggest that NO 3 incorporation into the cage is favored over the incorporation of the larger ReO 4 , due to the smaller ionic radius of NO 3 . In conclusion, based on these results, it is expected that NO 3 , which is present at significantly higher concentrations in alkaline waste solutions than 99TcO 4 , will be strongly preferred for incorporation into the sodalite cage.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3]
  1. Washington State Univ., Pullman, WA (United States). Dept. of Crop and Soil Sciences
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
Publication Date:
Report Number(s):
LBNL-181975
Journal ID: ISSN 0013-936X; ir:181975
Grant/Contract Number:
AC05-00OR22725; AC02-05CH11231
Type:
Published Article
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 48; Journal Issue: 21; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1234080
Alternate Identifier(s):
OSTI ID: 1373101