title: Structure and Thermochemistry of Perrhenate Sodalite and Mixed Guest Perrhenate/Pertechnetate Sodalite.
abstract: Treatment and immobilization of technetium-99 (99Tc) contained in reprocessed nuclear waste and present in contaminated subsurface systems represents a major environmental challenge. One potential approach to managing this highly mobile and long-lived radionuclide is immobilization into micro- and meso-porous crystalline solids, specifically sodalite. We synthesized and characterized the structure of perrhenate sodalite, Na8[AlSiO4]6(ReO4)2, and the structure of a mixed guest perrhenate/pertechnetate sodalite, Na8[AlSiO4]6(ReO4)2-x(TcO4)x. Perrhenate was used as a chemical analogue for pertechnetate. Bulk analyses of each solid confirm a cubic sodalite-type structure (P4̅3n, No. 218 space group) with rhenium and technetium in the 7+ oxidation state. High-resolution nanometer scale characterization measurements provide first-of-a-kind evidence that the ReO4-anions are distributed in a periodic array in the sample, nanoscale clustering is not observed, and the ReO4-anion occupies the center of the sodalite β-cage in Na8[AlSiO4]6(ReO4)2. We also demonstrate, for the first time, that the TcO4-anion can be incorporated into the sodalite structure. Lastly, thermochemistry measurements for the perrhenate sodalite were used to estimate the thermochemistry of pertechnetate sodalite based on a relationship between ionic potential and the enthalpy and Gibbs free energy of formation for previously measured oxyanion-bearing feldspathoid phases. The results collected in this study suggest that micro- and mesoporous crystalline solids maybe viable candidates for the treatment and immobilization of99Tc present in reprocessed nuclear waste streams and contaminated subsurface environments.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS: 6038, Oak Ridge, Tennessee 37831, United States.
authors.forename: Eric M
authors.identifier: 0000-0002-4951-1931
authors.initials: EM
authors.lastname: Pierce
authors.affiliation: Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis , Davis, California 95616, United States.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lilova
authors.affiliation: Analytical Development Center, Savannah River National Laboratory, Aiken, South Carolina 29808, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Missimer
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Wayne W
authors.identifier: 0000-0002-0796-7631
authors.initials: WW
authors.lastname: Lukens
authors.affiliation: Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis , Davis, California 95616, United States.
authors.forename: Lili
authors.initials: L
authors.lastname: Wu
authors.affiliation: Department of Civil & Environmental Engineering, Princeton University , Princeton, New Jersey 08544, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Fitts
authors.affiliation: Department of Materials Science & Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Claudia
authors.initials: C
authors.lastname: Rawn
authors.affiliation: Chemical & Engineering Materials Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, United States.
authors.forename: Ashfia
authors.initials: A
authors.lastname: Huq
authors.affiliation: Department of Materials Science & Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
authors.forename: Donovan N
authors.initials: DN
authors.lastname: Leonard
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, MS: 6038, Oak Ridge, Tennessee 37831, United States.
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Eskelsen
authors.affiliation: Chemistry & Biochemistry, Brigham Young University , Provo, Utah 84602, United States.
authors.forename: Brian
authors.initials: B
authors.lastname: F Woodfield
authors.affiliation: Environmental Technology Center, Savannah River National Laboratory, Aiken, South Carolina 29808, United States.
authors.forename: Carol M
authors.initials: CM
authors.lastname: Jantzen
authors.affiliation: Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California at Davis , Davis, California 95616, United States.
authors.forename: Alexandra
authors.identifier: 0000-0002-3260-0364
authors.initials: A
authors.lastname: Navrotsky
mesh_terms: D009930:Organic Chemicals; D011850:Radioactive Waste; D013670:Sodium Pertechnetate Tc 99m; D013667:Technetium
chemical_list: D009930:Organic Chemicals; D011850:Radioactive Waste; D013667:Technetium; D013670:Sodium Pertechnetate Tc 99m